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Anyone using Thornwave Powermon Relay and Li Monitor to disconnect Alternator charging ?

12kw_2021

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May 3, 2021
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Hello

I just purchased a Thornwave Powermon battery monitor. It is reviewed as having on board timeline data, excellent blue tooth range, and I just noticed it also has relay control based on measured battery voltage.

I have a Mastervolt Chargemate pro 40 DC-DC device that connects the house battery to the starting battery/alternator and a switch to turn in on and off.
My understanding is that the Chargemate Pro is really just a charge current limiter, and quite dumb beyond that, and they assume you will add downstream components to turn the device on when the engine is running, and to turn the device off when the output house battery is full.

Without additional components added to send a "turn off now" when the Li battery if full to the Chargemate pro I cannot use this Chargemate pro device as it will just keep sending current as long as the engine is running and the alternator is sending current to it.

I know other DC-DC chargers have built in settings to control the charging based on battery V levels, but would like to make use of what I have on hand as long as I can do so safely.

Thornwave sells nice 100Amp solid state relay that can be turned on and off and could be placed in the +12v output of the chargemate., so I will need to build a circuit that turns the Chargemate pro on when the engine is running , and off when the Lithium battery is full.

Is there a risk in utilizing the Thornwave powermon to turn off the DC-DC charger based on the measured battery V, say off if/when it see > 14V on the house LI battery? I see that it has that feature built in.

Current rough plan would be do two things when the House battery V is >14V...
1.0 Turn off the chargemate regardless of engine condition running or off
2.0 Open the solid state relay output from the chargmate pro to the house battery.

Doing this would mean my alternator charge current has two items to fail and prevent overcharge of the battery and BMS battery disconnect from my RV.

Thanks for any feedback, and if you think this is an incorrect path to go down let me know please.
 
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