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Battery Low Temp Disconnect?

JAS

Solar Enthusiast
Joined
Jan 16, 2020
Messages
506
Hey all,

Been thinking... If my low temp disconnect kicks in on the battery, isn't that the same as disconnecting the Charge Controller from the battery? And if so, isn't that bad to do to a charge controller? (IE: disconnect battery while the solar panels are still connected and charging)
 
Depends on the type of BMS. Overkill and other separate-port BMS just cut the charging circuit, not the discharging circuit.

Additionally, most controllers suffer no ill effects from a battery disconnect with panels attached even if there are cautions in the manual.
 
Alternately ... Choose a charge controller that can be shut down remotely without disconnecting from the battery ... and a BMS that is capable of doing that. The same thing can be done with the inverter.
This option also removes the necessity of switching what could be higher current.
 
Set the low temperature cutoff of the solar charge controller to a higher value than used by the BMS. That way the solar charge controller isn't pushing power to the system when the BMS decides to cutoff charging.

The counterargument to that is, what happens when the BMS cuts off charging due to hitting a high voltage threshold? It seems to me it's the same thing as the low temperature cutoff. If you aren't worried about the solar charge controller in the case of high voltage disconnect, then why are you worried about it due to low temperature cutoff? You can set the solar charge controller to stop at 14.3 and the BMS at 14.4. But a single cell can hit the cell high voltage threshold without hitting the battery threshold of 14.4.
 
Just for clarification... I already have a Battle Born with an EPEver Tracer CC. So the BMS is not configurable and the CC does not have the "smarts" for a low temp disconnect either. So short of throwing the breaker/disconnect on my panels when I think about it, I guess I just won't worry about it...
 
BB has built-in low temp protection. Disables charging. Allows discharge.
So that would imply the CC won't get disconnected when the BMS goes into low temp protection, correct?

However, as HRTKD mentioned, does BB BMS keep allowing discharge when a high voltage charging event occurs?
 
So that would imply the CC won't get disconnected when the BMS goes into low temp protection, correct?

However, as HRTKD mentioned, does BB BMS keep allowing discharge when a high voltage charging event occurs?

What I meant was that the low temp cutoff and high voltage cutoff should look the same from the perspective of all the devices connected to the battery. Charging is disabled, but the discharge still works.
 
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