The TriMetrics and PentaMetric  are both designed to help you maintain  batteries which are  periodically charged and discharged such as are  typically used for storing energy in  solar or wind powered homes, RV’s or boats or (for the PentaMetric) remote offgrid commercial sites with batteries.

The TriMetric will be the choice for most battery systems in homes, RV’s and boats where the owner does not need the greater analysis capability that the PentaMetric has.

The PentaMetric has additional capability to do more extensive system analysis, and logging of system data, which can be controlled by a computer and emailed or even controlled and analyzed remotely. The PentaMetric may be appropriate for larger systems or for systems owned by technical users who are interested in more system detail, or systems which may be managed by installers that are not usually  at the battery site, or unattended commercial installations.

Both monitors show you the following:

• flow of energy in or out of the batteries (in amps or watts) so you can check your charging sources or electrical loads.
• battery volts
• battery state of charge (i.e., how much energy is left in the batteries)
• how recently since you fully charged the batteries, which is useful because lead acid batteries should not go too long between being fully charged.

 How they keep track of “state of charge” They both determine the “state of charge” by keeping track of the amp hours flowing in and out of the batteries. This is a more accurate method than using only the battery voltage as some less expensive meters do.

How they keep track of "state of charge" (PDF)

The TriMetric battery monitor now comes in three variations: The  TM-2020 has been made since 1999. The (two) newer TM2025-RV and TM2020-A models were introduced in 2009, and are very similar to the TM-2020, but have some improvements over the  TM-2020 based on customers’ experience.  

The two newer TM-2025’s  are both identical to each other in function, but differ only in physical size and label colors. The TM-2025-RV has its own enclosure with more muted front panel colors. The TM-2025-A has a larger panel size and fits into a “double gang” electrical box, which is not included, but can more easily be flush mounted on a wall.  

More about TriMetric

All require external shunts: Both TriMetric and PentaMetric measure the amps flowing in and out of the batteries by using an electrical shunt (or shunts)  that are accessories which must be installed in series with the negative cable of the battery system. They cost about $30 each. There are two types depending on whether the maximum current flow (amps) charging or discharging is less or greater than about 70 amperes. More shunt info can be found in our application notes.

The PentaMetric is more complex and more expensive—but that does not mean that it is necessarily better for any application than the TriMetric. For many users the TriMetric is the better choice because it is less costly,  and simpler to install and use.