Lithium Battery Update – OUT goes the InterVolt and IN comes Contactor for BMS system

Well that didn’t last long. Dave (SV Nimrod) filled me in that the InterVolt Programmable Voltage Relay, that we both were using, are only low voltage relays and would not chop the connection in over-voltage conditions. Shit, that is no good. While the LiFePO4 don’t catch fire they can smoke and make a big mess, not to mention destroy the expensive batteries. The picture above is the final installation with Contactors and BMS on both battery packs.

So instead of using the BMS only for cell charge balancing, I will now use it to disconnect the batteries if there is a “too low” or “too high” voltage on the batteries. This required purchasing a Contactor (relay) for the House and for the Starter battery packs. I went with the recommended Tyco (TE) (P/N EV200AAANA) 500 amp relay, with a 12V coil voltage with the “economizer” (lower operation current). This unit is hermetically sealed and completely water-proof. Not that I will be testing this property…

After removing the Intervolt units it was an easy swap since the studs on both units were 8mm bolts. New mounting holes tapped for the Contactors, protection over the battery terminals and quickly the system was up and running.

I will be adding a 0.25″ thick Plexiglass cover over the entire battery system shortly.