Don't risk your LiFePO batteries.

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Jim Niemann

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Jun 4, 2021, 11:44:32 AM (8 days ago) Jun 4
to electrodacus

As has been described numerous times.  The SBMS controllers will cut off both charge and discharge if the EXT temp reaches less than setting.   LiFePO don't like a charge below freezing,  but they are okay with BEING DISCHARGED far below freezing.  As Dacian has stated the ISL chip is programmed to cut both CHG and Discharge.  I had a heating element and heater in my RV hooked to SBMS load.   My heating element failed, and when the SBMS cut power that night my heater fan also died.  So I could not heat the RV until the next day when temps warmed up.  What I did to prevent this from happening again was hook the heating element and the RV heater directly to the battery.  Use an OPTO relay that is hooked to SBMS EXT low voltage cutoff so you cant drain your batts below specs.
Nothing more frustrating than having a full battery and not being able to discharge it to stay warm.

Dacian Todea

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Jun 4, 2021, 3:20:10 PM (8 days ago) Jun 4
to electrodacus
Jim,

Not quite sure what you did but the battery heater needs to be supplied through something like a Victron BP65 or similar controlled by SBMS0 EXT IOx set as type 2
Not quite sure how a heating element can fail but if it did and you had a low temperature limit set then yes the SBMS0 will stop all charge and discharge sources as any temperature limit (high or low) is considered a fault.
I also do not understand what your solution was as you mention the heating element is controlled by the SBMS0 EXT IOx but that was also the case before so how is now any different ?
Battery box should be designed so that battery is always kept above freezing then you will not have any of the mentioned problems.  If battery is not well insulated then battery will either get cold or you will spend more energy than the battery contains trying to keep it warm.

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