Can setting low temp cutoff in BMV-712 stop AC converter charging?

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jdhaasdmb asked Apr 15, '21

Can setting low temp cutoff in BMV-712 stop AC converter charging?

I am running the BMV-712, Battery Smart Temp Sensor and the MPPT 100/15 with a 2x LiFePo4 200amp hour battery bank. The battery bank has BMS onboard but a low temp cutoff is not included unfortunately. I have things set with the MPPT to cutoff charging at 3deg C but that is only when charging from solar. It looked like if I set the BMV-712 relay low temp cutoff setting to 3deg C, it would cut charging regardless of whether it was from solar or the AC charge converter but my tests are showing the relay closed when it's supposed to be, however the AC charge converter is still charging the battery bank. Any thoughts or ideas? Thank you in advance.

BMV Battery Monitor charger Temperature Sensor mppt charging ac

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Answer 1 · 2021-04-15T17:44:14Z

Kevin Windrem answered · Apr 15, 2021 at 05:44 PM

What is your other charging source? Does it have a control input? If not, you will probably need to use an external relay to interrupt the AC input to the charger.

The other option is to insert a battery protect in all charging paths to the battery and feed that with the BMV's relay.

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jdhaasdmb commented · Apr 15, 2021 at 05:58 PM

Thank you Kevin, My charging sources are the AC charge converter when connected to shore power, a suitcase solar unit I connect to the input on the side of the RV and the 12v source from the tow vehicle when connected to the 7-pin wire harness.

I thought the battery protect only protected against voltage, not temperature?

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Kevin Windrem jdhaasdmb commented · Apr 15, 2021 at 06:15 PM

The Victron battery protect units have a control input that opens the connection. They also shut down the connection on low voltage.

In this case, you'd wire your charging sources to the input of the battery protect and the battery to the output.

If you want low voltage battery protection, you'd need a second battery protect between the battery and the loads.

By "converter", I assume you are referring to the standard component in an RV that's either in the power distribution panel or somewhere near by in a separate box. Some of the Progressive Dynamics units have remote shutdown inputs which could be connected to the BMV's relay but most do not.

Note that regardless of the mechanism, low temperature battery protection will disable the converter so in this mode you are running your DC loads only on battery even if you have shore power!!!!

Alternatives include moving the LFP batteries inside the RV's living space to avoid the low temperatures or fitting the batteries with heat blankets.

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Answer 2 · 2022-12-05T22:00:30Z

avk13 answered · Dec 05, 2022 at 10:00 PM

@jdhaasdmb were you able to resolve this issue? I have a similar predicament for my class A. I'd like to convert to LiFePO4 batteries, but would like to protect my battery from charging from the converter charger below 32F with the BMV-712 using the temp sensor. Were you able to do this?

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