Frequently Asked Questions

Q1. How does the TriMetric (or PentaMetric) determine Battery Percent full ?  

Here’s a brief description: When you first connect the meter to the battery system it has no way of knowing how full the battery is. It requires the following process to determine this:

1. When the battery is measured to be “full” (because during battery charging, the battery volts are high enough, and at the same time the charging current is low enough) it then immediately says the batteries are “100% full.” To do this it uses the programmed volts and amps setpoint values (program P1,P2,P3 values in the TM-2030.)

2. After that, whenever you withdraw energy, as indicated by an “amps” number that is negative, the percentage goes down depending on your current draw from the battery, much the way the bank knows your bank balance by always subtracting your withdrawal amount when you take out money.

3. When you are charging, as indicated by an “amps” number that is positive, then the percent number goes up, but it is discounted slightly by a “efficiency factor” which you can set, but defaults to 94% of the actual amount. The reason for the discount is that to be charged the batteries require a little more energy to be put in than was taken out before.

4. As you use your system it continues to go up and down until it again senses that they are “full” (described in step 1) which should be when the value is pretty close to “100%”–and then again resets the number to exactly 100% to start the process again.

In a system being constantly charged and discharged this is usually much more accurate way to measure “state of charge” than what just the voltage can tell you.

A more complete description is shown in the TM-2030 or TM-2025 “Users Intructions” (or “Manuals”). In either document go to section 6.2. This can be downloaded from the web site. At the top of this page go to “support-manuals.”

Q2. My TriMetric (or PentaMetric) works mostly OK except the values for Battery Percent Full seem wrong. How can I fix this?   

If your only problem is that the display shows three dashes, see TriMetric Frequently Answered Questions, Q4.

Before troubleshooting the “Percent full” display, please read FAQ above, Q1.

Two important things to know about the Percent Full display: Once the correct settings are entered, and the meter and all loads and charging sources are connected correctly in your system the Percent Full display on the TriMetric (or PentaMetric) is quite easy to use and pretty accurate. But if it is not working right that could indicate some problems with the way your system is connected. Note the following two points:

1. This display is mainly useful when your batteries are being discharged, and then recharged frequently, such as would be the case when relying mainly on solar power when living in a home, or when using solar power while “boondocking” in an RV. During a period when your batteries are hardly being used it’s not as useful, as you typically know that the batteries are staying pretty full.

2. If the Percent full display is NOT working properly, you should be concerned. It may indicate a problem that also affects your battery life, or the meter could sometimes be showing the wrong “amps” data.

Once wiring and setpoint problems are eliminated, as mentioned above, the real usefulness of this data is when the batteries are being somewhat discharged, then recharged again. If you batteries are in a period of not being used, but mostly sitting being kept at standby at their “float” voltage by solar or a line charger the batteries will typically be kept pretty fully charged by the charger. When you are discharging your batteries regularly is when this function is really useful. The only requirement for useful % full data is that regularly used batteries are being “pretty well charged” every 5 days or so–which is also necessary to maintaining your batteries’ capacity.

What can go wrong falls in two large categories:

1. METER PROBLEMS: the two programmable “charging parameters” in the meter must be correctly set. The meter must read the correct value of “amps” going in or out of the batteries.

2. CHARGING SOURCES AND LOAD MEASUREMENTS: All charging sources must be charging correctly and loads and charging sytems must be connected correctly in your system. What is “correct” is completely covered in the TriMetric step by step “Installation Instructions.”

Within these two categories, a lot can go wrong. To fix the problem you must find out where the problem is.

In the METER PROBLEMS category:

A. Two parameters in the meter must be programmed correctly: the “charged volts setpoint” and the “charged amps setpoint” must both be correct. To check these, for the TM-2025 or TM-2030 see section C.1 in the TM-2025 or TM-2030 “INSTALLER’s INSTRUCTIONS.” For the TM-2020 see the “TM-2030 INSTRUCTIONS”, section C.1.

B. The wires from meter to shunt must be correctly connected to the shunt so the “amps” are being accurately measured. Most important is that if the battery has zero charging or zero loads, the meter must show zero amps (not more than 0.1 amps). We will soon have an FAQ on this topic.

In the CHARGER and LOAD category:

A. Your chargers (alternators, generators, solar controllers, inverters) must have their “absorb” voltages adjusted correctly to get batteries reasonably well charged. This is especially important for the one doing the final, or finish charging.

B. Enough charging time needs to take place to get the batteries reasonably well charged.

C All chargers and loads must be correctly connected to the shunt, so that the amps from each charger and load is properly “seen” by the TriMetric. It is surprising how often people have a wrong connection that doesn’t allow this to happen. This point covered in the following INSTALLATION instructions: TM-2030,”INSTALLER’S INSTRUCTIONS” under Section B, Step 1, “avoid a common mistake” and also Figure 1. For the TM-2025: TM-2025 INSTALLERS’ INSTRUCTIONS, Figure 1. For the TM-2020,User’s Instructions, wiring diagram last page, look at lower left–read in box just above the minus battery terminal.

The same problems can exist with all the TriMetrics. However, for troubleshooting, the newer TM2025 and TM2030 have a big advantage over the older TM2020. They have some very useful “history” data that makes it easier to discover where the problem is.

Q3. How can I find what the volts and amps” charged setpoints are in my TriMetric? 

To get the “volts” charged setpoint number for the TM-2025 or TM-2030 do this: Hold down the “SELECT” button (this will take 8 seconds or less) and watch for “P1” to come into the display. As soon as you see “P1” release “SELECT.” P1 will alternate with a voltage number which is the “charged setpoint voltage”.

To get the “amps” charged setpoint number for the TM-2025: While observing the “P1” data (above) push the SELECT once to get P2. The P2 data is the “amps” charged setpoint.

To get the “amps” charged setpoint number for the TM-2030: while observing the “P1” data (above) push the SELECT once to get P2, which is a percentage. Then Push SELECT again to observe P3, which is the system capacity. Multiply the percent P2 times capacity P3. The result will be the “amps” charged setpoint.

To get the “volts” charged setpoint for the TM-2020 do this: Use SELECT button to read “Volts”. Then push SELECT button down, and quickly while holding SELECT push RESET at the same time. (If you hold SELECT down too long you will go to “AH” display, and have to go back to VOLTS and try again.) The “volts” light will flash and the number will the the “volts charged setpoint”.

To get the “amps” charged setpoint for the TM2020 do this: Use SELECT button to read “Amps”.Then push SELECT button down, and quickly while holding SELECT push RESET at the same time. (If you hold SELECT down too long you will go to “AH” display, and have to go back to VOLTS and try again.) The “Amps” light will flash and the number will the the “Amps charged setpoint”.

Q4. My TriMetric Percent full display shows only three dashes. How do I fix this? 

Whenever the TriMetric TM-2025 or TM-2030 is powered off and on, the Percent Full display usually begins to show three dashes. The reason is that when first powered it has no way of knowing how full the batteries are. It won’t be accurate until the TriMetric detects that the batteries are fully charged for the first time, after which the numbers will remain in the display. If you have three dashes it is because the meter hasn’t sensed this yet, or your power has gone off and on and it hasn’t been fully charged after power was returned.

The way the meter determines that the battery is “charged” is that it senses that the battery “volts” exceeds the programmed “charged volts” setpoint and at the same time the battery “amps” is LESS THAN the “charged amps” setpoint. These must both occur at the SAME TIME. The FAQ A3, (above) describes how to determine what these setpoints are. If you continue to see only three dashes after you think your batteries should be charged it is because your batteries are not reaching these programmed setpoint values. That could be because the setpoints are wrong, or because your charger (or chargers) are not achieving these target setpoint values. To change these values, please refer to the “Users manual” for either the TM-2030 or TM-2025. Refer to Section 5 in those documents. Both of these documents may be downloaded from this website under “support”, “manuals.”

Also, the values of “volts” and “amps” from the battery that the meter is using to do the above test are not exactly the regular “volts” or “amps” values that you usually see on the meter. It is using “filtered” versions of these values, which are more slowly responding, sluggish versions of these displayed values. If you wish to view these actual test values, you need to go to program “P7” in your meter and change the Operation Level to “L3.” After doing this, go back to observing the regular “volts”or “amps” value display. Whenever you hold the RESET button down the display will then show the filtered values instead.

Also useful for troubleshooting is that the TM-2030 and TM-2025 also have some “History Data” which shows the highest (charging) voltage reached during each day for the last five days of operation, as well as the lowest charging current at the same time. This can be quite helpful to discover whether your chargers have gotten the voltage high enough, and the charging current has gone low enough to reach the “charged” criteria. The best place to read about reading the History Data is to download a late version (February 25, 2015 version or later) of the TM-2030 “User’s instructions”. The information there is also applicable to the TM-2025. Look in section 6.3. The important history data are items H7 and H8.

Q5. Your wiring diagrams all have the red wire w/fuse connecting directly to the battery + terminal. Does it really have to go directly to the battery + terminal?

The reason for connecting the wire going to the B1 terminal close to the battery + terminal is for the TriMetric to get an accurate measure of battery voltage. If you connect it too far away from the battery terminal there could be a slight difference in voltage, due to currents flowing in the cable between the connection point and the + battery terminal. If the distance is short, and the currents are not high, and the cable is large the difference may be insignificant.

It is especially important to have accurate battery voltage when you are also using the SC-2030 solar charger–because when the SC-2030 Solar Charger is being used with the TM-2030 this voltage is used to control the charging to an accurate voltage. Some battery companies specify that the “absorb” charging voltage should be controlled to within 1/10 of a volt or so. In some systems the battery voltage could vary significantly more than this depending on exactly where the voltage is measured if the cables conducting the battery currents are small, or if the cables are long.

So the bottom line is that if the point you choose to connect it is close enough to give an accurate measure of the voltage across the battery terminals, it is OK.

Q6:  The Amps reported by my monitor often differs the actual current by a set amount.  And, when I turn off all the loads, I expect to see a current reading that is close to zero, but the monitor shows several Amps.  What could cause this?

The monitor consumes between 30 to 50 milliamps ().03 to 0.05 A) for its operation.  This current is delivered to the monitor on G1 & B1 wires.  A consequence of this is that there is a small voltage drop along these conductors.  Wires SIG & G2 are used to measure the voltage across the shunt and do not carry any current.  Though wires G1 & G2 originate at the same point on the shunt, they must not contact each other on their way to the monitor’s back terminals.  Any accidental contact between G1 & G2 will create an electrical potential between G2 & SIG and the monitor will interpret this as a real current.  To fix this problem, examine the wiring thoroughly, looking for breaks in the insulation and correct any issue discovered.  To rule out issues with the monitor itself, perform this test.

Q7. Explain the rPC (replaced percentage) display that is new to the TM-2030. How is it useful to determine that batteries are being properly charged? 

This display is unique to the TM-2030 and is one of the most useful displays it has for determining that your batteries have been properly charged. It is listed as the last item in the “extra display” section on the front panel of the TM-2030. To access it, hold the SELECT button down until the “AH” pops into the display—then release SELECT. Then push SELECT four times until the “rPC” display shows.

Two types of information are available:

1: Percent of charge returned: When your batteries are charging, it shows what percentage of charge you have returned during the charge process, compared to the lowest point of the previous (recent) discharge of the battery set. Properly charged batteries require that more than 100% of previous discharge be returned, but usually less than 120%, as described below. (This does NOT mean 104-110% of your total battery capacity.)

2: Lowest amount of charge previously removed: When your batteries are charging, if you hold down the RESET button while watching this display it will show how low the amp hours went during the PREVIOUS discharge of your batteries, such as the night before. You can observe your actual amount of usage (amp hours) of your batteries during the previous evening, for example. However if you didn’t fully charge the batteries the day before, then it will show you the lowest amp hour value since the last full charge.

Why is this useful? Many battery company experts believe that the best way to determine how much to charge is to replace all the energy just previously replaced, followed by 4-20% more depending on battery type. This is what the “recharge percentage” display shows. This avoids overcharge or undercharge. After reaching correct overcharge batteries should go into “float” mode. Vendors of liquid electrolyte batteries often recommend that you return 110-120% of what charge you previously removed. With AGM batteries the number is usually less—typically 104-110% depending on the battery company.)

Example: If during the day you fully charged your batteries, and then during that evening took 50 amp hours of charge from your batteries, then the next day when you begin to recharge you will observe 50 in the “lowest amount of charge previously removed” display (while holding down the RESET button). When you release RESET it will show you the percentage of charge returned during your present charge period. So when charging begins it will start with “0” and gradually rise while charging. When you replace 50 amp hours it will then read 100%. As you charge further it will go up to 110-120% or even higher, indicating that 55-60 total amp hours have been returned. When you get to the desired charge, ideally your charge controller should go into “float” mode.

This is one of the the best ways to decide when to stop charging and go into “float” mode, and works even if you use more than one charger. If you are using the Bogart Engineering SC-2030 charger it will automatically stop charging at some point (such as 10% overcharge) to a value that you have programmed (by program P20.) If you are using a different solar or any other type of charger, you can use the above display to see if you are under or overcharging. If undercharging possibly you would want to increase the “absorb” time of your charger, or increasing the absorb voltage somewhat (if these are adjustable options with your charger). And do the opposite if your percentage is going too high, which can happen especially if batteries are charged by an enthusiastic solar charger during a period when batteries are not being used, for example while an RV is being stored outside for days.

For the TM-2030 to keep track of charging in this way it is very important that every charger you have registers its amperage on the “Amps” display of the TM-2030. This will be the case if charging sources are properly connected to the shunt as shown in figure 1 of the “TM-2030 Installation” instructions.

If your batteries have been used very little during the night such as an unoccupied RV, then the extra charge will be very small, to prevent overcharge. When you have previously used power, you can verify that your charging source has charged the battery sufficiently with the proper overcharge to properly maintain the capacity, as undercharging is a common cause of capacity loss with lead acid batteries.

Q7. According to a chart I have that shows how battery voltage relates to percent full, it indicates a charge that is different from the percent full display shown on the TriMetric. Which is correct? 

All charts that relate a battery’s voltage to its state of charge (% Full) use the ‘resting’ voltage – the voltage when the battery has not been charged or discharged for a few hours.  Besides, the voltage in these charts use the voltage of the battery when its internal temperature is 25 C (77 F).  At other temperatures, a correction must be applied to the measured voltage before it can be used to estimate the state of charge.

The above requirements make the voltage of a battery while its under use a very unreliable indicator of its remaining capacity.

Our battery monitors accurately measure the Amp-hours taken out from (or returned to) a battery bank and calculate the state of charge.  This approach is similar to a personal finance program that uses all deposits & withdrawals from a bank account to calculate the balance remaining at any time.

SC-2030 and charging Frequently Answered Questions

Q1. The debate rages: which controller is best PWM (Pulse Width Modulation) or MPPT (Maximum Power Point Tracking). Why did you choose PWM technology instead of MPPT for your SC-2030 Solar Charger? 

A very good question! They BOTH have good and bad. Plenty of hype has been written already. Here’s my (Ralph’s) view:

The “good” for PWM: It is simpler and lower cost technology. Under some common circumstances–it can actually deliver more amps to the battery. That could be when:

(1)days are moderate or warm, with few clouds.

(2) batteries are charging at over 13 volts, (in a 12 battery system) which they almost always are when actually CHARGING.

(3) Panel voltage is properly matched to the battery voltage, for example “12V” panels are being used with a 12V system.

PWM is actually more “power efficient” than MPPT–which means less total power loss in the controller itself. So heat sinks in the design can be smaller (and less expensive). Missing in most analysis of MPPT is that there is always a conversion loss with MPPT, which tends to be higher the greater the voltage difference between battery and panels. That’s why PWM can actually beat MPPT under circumstances described above.

Some places that analyze MPPT assume that panels with 30V open circuit voltage are being used in a 12V system. Any good MPPT system will easily provide better performance in that case. They also may assume batteries are charging at 12 or even 11 volts, which is unrealistic. Lead acid batteries are typically below 13 volts only when discharging, or perhaps charging with very little charging current–meaning the actual potential gain in amps is not great.

The benefit for MPPT becomes apparent if you use panels not voltage matched for the battery. If they are not, MPPT will utilize more of the potential energy of the panels. For example, if you use 24 volt panels to charge a 12 volt battery system you must use MPPT, otherwise you would be using your panels very inefficiently. If you are trying to use PWM in that case, you are misusing the PWM technology.

Another potential benefit with MPPT is that if distance between panels and batteries is far, smaller wire can be utilized by running panels at higher voltage to the batteries. Running at twice the voltage reduces wire size to 1/4, which for a long run can be a significant saving in copper wire.

If temperatures are low enough, the slightly less power efficiency of MPPT will be compensated by the higher panel voltages, which will result in a little more battery current. But in actual measurements we made using a commonly sold MPPT solar controller, this would occur at temperatures less than 55 F degrees (in full sun, when charging at more than 13 volts), where there is a slight advantage to MPPT in my location (Boulder Creek, near the California coast). As temperature drops below that (in full sun) MPPT will get some advantage, such as could occur at high elevations in Colorado in the winter. Potentially this would be maximum about a 2.5% improvement in amps output for every 10 degrees F lower in temperature (or 4.6% per 10 degrees C colder. I’m using data from Kyocera KD-140 panels.)

There can be theoretically optimal situations (that I don’t personally experience where I live) where MPPT could give some advantage: that is when solar current is present, but the batteries are quite low in charge–but because loads are high and even greater than the solar current the batteries are still discharging despite the solar current. Under these conditions the voltage COULD be at 12.5 volts, or even lower. Again, using data from Kyocera panels, (“Normal Operating Conditions”) there is a theoretical maximum gain over PWM of 20% current assuming NO MPPT conversion loss and no voltage drop in the wires to the panels, at 20C (68F). With PWM, the voltage drop in the wires in this case would not affect the charging current. Now if in addition you lower the temperature to below freezing at 28 degrees F (while sun is shining) you might actually get up to a THEORETICAL nearly 30% gain while the batteries are discharging.

The only REALLY BAD part of MPPT, is all the hype surrounding it–for example one manufacturer advertises “UP TO 30% OR MORE” power harvested from you panels. If you are using solar panels properly matched to the batteries, 30% ain’t gonna happen unless it’s EXTREMELY cold. And your batteries have to be abnormally low in charging voltage–which tends not to happen when it’s cold (unless you assume the battery is still discharging while solar is happening). Virtually all the analyses I’ve seen touting MPPT on the Internet ignore the conversion loss, assume really cold temperatures, assume unreasonably low charging voltages, assume no voltage drop in the wires from panels to batteries, use STC conditions for the panels (that the marketing types prefer) rather than more realistic NOCT conditions, and in some cases assume panels not voltage matched to the batteries.

The other thing that is misleading about MPPT, is that some manufacturers make meters that show both the solar current and the battery current. In almost all cases for a well designed MPPT type the battery current will be greater. The engineers making these know better, but it is implied (by marketing types?) that if you were NOT using MPPT you would be charging your batteries with only the SOLAR current that you read on their meters. That’s not true, because the PWM BATTERY current should always be higher than the MPPT SOLAR current. It is the nature of the MPPT that maximum power occurs when the current is lower than the maximum, so they must operate there to get the maximum power. So to properly compare the two you need to compare MPPT with an actual PWM controller in the same circumstances.

Finally, the reason we went to PWM is that I was anticipating that panel prices were going to drop (which they certainly have over the last 5-10 years!) and that the small advantage of MPPT (under conditions where the correct panels are used for the batteries) would not justify their additional cost and complexity. So my thinking, for more total benefit per $, put your money in an extra panel rather than a more expensive and complex technology.

Q2. Is it OK to extend (or reduce) the length of the TS-2 temperature sensor cable that connects to the SC-2030 charge controller ?

Yes. You can cut the cable, and eliminate a section, or add an additional amount of your own cable. You don’t need to be concerned about the polarity of the wires when you do this. The sensor works with either polarity. Changing the length will not affect the accuracy of the temperature measurement.

Q3. What happens when I hook up a grid tied charger, or to shore power at a park with your SC-2030 Solar Charger? Is there any conflict or concerns when this grid charger comes on to charge the batteries?

That will not cause a problem as long as your shore power device negative output is connected to the correct “load” side of the shunt, (not directly to the negative post of the batteries) as illustrated on Figure 1 of the TM-2030 INSTALLATION instructions. If it is correctly connected, then when you charge with your grid power you will be able to observe the charging amps on the TriMetric “amps” display. Then the TM-2030 will be taking account of this when it regulates your solar power and when it decides to go into “float.” Of course the TriMetric won’t be able to restrain the grid charger if it tries to overcharge too much. However while you are using it you can observe the “rPC” display occasionally on the TriMetric and turn off the shore charger if it’s heading above 115% or so which is desirable for most wet cell batteries. (108% with AGM type batteries) The “rPC” (“replaced PerCentage”) display shown at the bottom of the TriMetric front panel, this is NOT the main “% full” display.

Q4. What happens if my panels try to put more than 30 amps with your SC-2030, 30 amp Solar Charger? Will that damage it?

No, it will not. Incidentally, it is actually a 31 amp charger. If you try to put in more than 31 amps it will limit the current to protect itself. So it is OK to use panels that normally have a maximum of about 30 amps or even more, but which may occasionally exceed that if cloud effects on a very sunny day cause the amps to go higher.

When that happens the amber light on the charger will flash twice per second to let you know. But if you try to exceed 31 amps, it will not just limit the amps to 31. In order to safely protect the charger, it will limit it to slightly LESS than 31 amps, according to this formula:

A= (31*31)/P = 961/P.
A=Amps into battery,
P=Amps panels try to put into charger when greater than 31 amps.

But you needn’t be concerned that this will damage the SC-2030. If you try to use panels that very commonly go over 31 amps, you won’t hurt the SC2030, but you will be losing some solar energy whenever that happens because it will be putting in LESS than 31 amps, however it won’t be much less so long as the panels don’t go much above 31 amps.

Q5. What is equalization? Why, when and how should it be done ?

What it is:

Equalization refers to an occasional deliberate overcharge of wet cell lead acid batteries, usually by bringing the battery voltage higher, up to 15-17 volts for a 12V system, and putting more charge in the battery than the usual full charge. This term usually applies to only wet cell batteries, and not to sealed AGM or gel type batteries. Under certain conditions some companies who make AGM batteries occasionally recommend a similar overcharge-often in this case referred to as “conditioning.”

Why Equalize?

“Equalization” serves three purposes. One function, from which the name is derived, is to get all the battery cells equally well charged. 12 Volt batteries consist of six 2 volt cells in series. If a battery experiences only partial charging, over time the cells may become imbalanced, and the weaker ones then limit the discharge capability.

A second purpose is to help restore batteries that may have been left for a time at a partial state of charge. As lead-acid batteries are discharged, lead gets transformed into lead sulfate. If batteries remain at less than full charge for too long the lead sulfate will gradually change its crystalline form. This will make it more difficult to fully recharge the lead sulfate back into lead and lead oxide. This results in a loss of battery capacity, called “sulfation” of the battery. A longer period of equalization can help reverse this process.

A third purpose is to cause some water in the electrolyte to break up into oxygen and hydrogen, causing “gassing” of the electrolyte. The bubbles rise to the top and stir up the electrolyte in wet cell batteries to keep the heavier acid from remaining at the bottom. This distributes the concentration of acid more evenly on the plates.

If complete charges occur regularly on a battery system, equalization may not be necessary. One of the objectives of the Bogart Engineering SC-2030 charger is to deliver daily “mini equalizations” intended to give a more complete charge based on the amount previously discharged. However this may not happen if there is not sufficient solar power to deliver the necessary overcharge.

If the battery has been chronically undercharged, using only battery voltage to judge that batteries are full can become unreliable because voltage can go high before the “charged” reaction has been fully completed.

When to equalize:

Battery companies often recommend that deep discharge type batteries be equalized at regular intervals, like every 30-60 days. This applies when batteries are regularly discharged, especially when they may not get fully charged frequently. On the other hand, if your batteries are in semi storage in a vehicle, and even getting slightly charged every day (by solar, or trickle charger on “float”) — then you should not need to worry about equalizing at all.

Some chargers equalize “automatically” at regular intervals, (weekly or monthly). However the best way to determine whether to equalize is to measure the specific gravity of the battery electrolyte (sulfuric acid) with a hydrometer to see that it matches what the BATTERY manufacturer says it should be. Check with a hydrometer only after a regular charge is pretty well finished, after some gassing has occurred to mix the acid so you get a representative sample of acid at the top of the battery. Then equalize if the acid is not getting up to the specific gravity value specified by the battery manufacturer for a fully charged battery.

How to equalize: As said, equalization requires that you must first get the batteries pretty well charged before beginning. If at that time the specific gravity is low for what a fully charged battery should be, then equalization would be appropriate. If batteries have been staying chronically at low charge, this process may or may not be effective in totally restoring the specific gravity. In that case equalization can often help to partially restore the specific gravity of the electrolyte. (You should not attempt to add additional acid to correct this. That won’t work because it doesn’t restore the lead which is the other half of the reaction.)

Accomplishing equalization may be difficult if you use your batteries nightly and only have solar power available for this purpose–because the equalization time required may be greater than one solar day. If you can’t do complete equalization in one day, then it could be done if you completely completely refrain from discharging the battery during the night and continue the next day.

A faster method if you are using solar power and also have available a generator or grid power is to start early in the day to charge the battery pretty well with your generator or grid powered source. Finishing the equalization process takes more time, but doesn’t require as much current, which is why solar is well fitted for the last part. While there are still many hours of solar available, measure the acid with a hydrometer. Then equalize if the acid is below where the battery company says it should be. If you are using the the SC-2030 charger (and TM-2030) look in Section 6 of the SC-2030 User’s instructions to see how to turn on the equalize function for 2 hours. Other chargers may have instructions describing how to equalize. After two hours, check again with a hydrometer to see if the specific gravity has increased. Repeat the equalization process for another 2 hours if it needs more overcharge. You could even continue the next day, but to do this you must not discharge the batteries significantly until the next day. If you partially discharge in between successive equalizations, you won’t be getting the benefit of this process.

After equalization:

When equalization is complete, it is often recommended to be a good time to check water levels in each cell. Add water to get them within 1/8 inch or so of the maximum water level marker in each cell. The reason for doing it at this time is to avoid overfilling because the water level tends to be the highest when batteries are well charged. Don’t fill them more than the indicated level indicator. Never fill to the very top.

Q6. Will your SC-2030 solar charger or TM-2030 battery monitor work with Lithium batteries?

Yes, the TM-2030 and SC-2030 will work with lithium batteries.

When used by itself in the stand-alone mode (no TM-2030 connected), the SC-2030’s AGM profile is very close to the profile widely recommended for lithium LFP batteries.  The AGM profile is: Absorb stage at 14.3V and float stage at 13.2V.

When used with a TM-2030, set the following parameters:

Set “Absorb” voltage P1 = 14.4 Volts.

Set “Absorb current before float P2 = 2.0%
Set “Capacity” P3 = capacity of the battery bank.

Set User Level in P7 to L3
Set “Max Absorb time” P14 = 0.3 hours.
Set Finish Stage voltage  P15 = 13.2 volts (not used for charging lithium batteries).
Set “float voltage” P16 = 13.2 volts.
Set Overcharge % P20 to 0% Set ‘Finish stage current limit’ P21 to 0%


Temperature compensation (recommended for lead acid batteries) are NOT be used for lithium. This means that you do not have to buy the optional temperature sensor and you should not connect it to the SC-2030 charger.

Q7. My SC-2030 solar charger seems not to be charging my batteries, even though there is plenty of solar. It often just stays in float, and the voltage doesn’t go up to the absorb voltage for my batteries. What’s wrong?  

If the SC-2030 appears not to be charging and it is staying in “float” despite much available solar, the most likely reason is that you are not using the batteries much–so the batteries don’t need much (if any) charging. If you would like to see it charge more, then use enough energy from your batteries so that the “% full” display goes BELOW 98% during the night– at least down to 97%, and preferably down to 90% or so. The next day after that it should charge- and the voltage should go up into the “absorb” voltage. If you only discharge to 97% it won’t stay at the absorb voltage long–only enough to make up 100% of what you used the night before, plus about 10% overcharge beyond that (depending on your P20 setting)–which might only take a very short time. The SC-2030 is designed not to overcharge batteries that have an abundance of solar energy and are not being used very much.

Shunt Frequently Answered Questions

Q1.Which shunt should I use in my system? 

The two choices are the 500 Amp/50mV shunt or 100 Amp/100mV shunt. The most common choice is the 500A/50mV shunt. The deciding factors are the MAXIMUM amps that you will either charge or discharge with your system, and the highest “amps” resolution that you want to see on your meter. Usually this is determined by your maximum loads on the battery.

The 100A/100mV shunt will likely overheat if your system if charging or discharging your batteries over 70 amps, so in that case you should use the 500A shunt. Going over this value will not harm the meter–however the shunt can overheat with too many amps. If you have an inverter, converter, or loads with a 12 volts system that exceed 800 watts (or with 24 system 1600 watts) then that will likely put you over the 70 amp limit. For example, using a microwave would usually exceed 70 amps in a 12V system. With the 500A/50mV shunt you will be able to read “amps” values down to 0.1 amp. A 0.1 amp draw in a 12V system would be represented by a 1.2 watt load. With a 24V system it would be 2.4 watts.

If you have a smaller system there is an advantage of the 100A/100mV shunt, in that you will be able to read amps values on the meter as low as 0.01 amp instead of 0.1 amp. This would hardly matter in a large system, but in a smaller system you may want to able to see really small loads. 0.01 amp would allow you to see loads down to 0.12 watt loads.

Q2. Is it permissible to connect more than one device to the Kelvin connections on the shunt? 

Yes you can. You can connect other devices besides the meter to these connections. To make sure two devices will not interfere with each other you should connect each device with its own wire going directly to each Kelvin connection. (The Kelvin connections are the small screws on the top or side of the shunt that are the critical sense points for measuring “amps’) For example, if you have two TriMetrics put a ring terminal on each wire from the “Sig” wire from the meter and then screw both ring terminals to the correct Kelvin terminal. One additional fact–if it gets too crowded on the Kelvin terminals, or if it is for some reason easier for you, the “G1” terminal does NOT have to be connected to the Kelvin screw. In this case you will have to distinguish between the “G1” wire and “G2” wire if they are the same color (often black.) The G1 wire can go instead to the big bolt near the corresponding Kelvin terminal with no loss of accuracy. However both the G2 and the Sig (current sensing) wires from the meter MUST be connected directly to the Kelvin terminals–otherwise the “Amps” values will not be accurate.

Q3. Can the shunt be exposed to any weather at all? I’m wondering about installing it under the coach in a semi protected area. It could get a little wet if driving in the rain but that would be it unless we drove through a flooded area.

The shunt is not a delicate device and need not be fully protected from the elements.  However, exposure wet conditions with corrosive chemicals like road salts can lead to corrosion on the Kelvin terminals & cause measurement errors.

Q4. Does the shunt need to be next to the battery? How far away can it be?

Even if the shunt is not close to the battery it will still measure the amps accurately. The main reason we say the shunt should be “near the batteries” is that the large cables to the battery need to be kept short to keep the voltage drop low to your loads and to charging sources. Since the shunt is in that path, it therefore will be near the batteries. The only slight inaccuracy that could occur if it isn’t near the battery is that if the cable is too small, or the amps are really high there can be a little voltage drop that will cause the “volts” on the meter to read perhaps as much as a few tenths of a volt different than is at the battery. This error will be minimized if the cable is large enough to keep the voltage drop low.