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MPPT SmartSolar doesn't charge deeply discharged LFP battery

We are attempting to charge a (non-Victron) 24V LFP Lithium battery after the BMS has turned off the battery due to deep discharge with a SmartSolar 100/30 and 1 solar panel (385Wp, 35 Vmp). There is no voltage to be measured on the poles of the battery. We also have a Victron battery monitor connected. We observe that the monitor keeps turning on, voltage going up to some 15V, the going down again and turning off again, this process takes a few seconds, after another few seconds the process repeats. This process continues and the MPPT seems to not be able to charge the battery. In one test where we had connected two panels in series it worked after a couple of minutes. Is there a way to get this to work with one panel, I am assuming with two panels the voltage ramps up quickly enough for the BMS to realize that there is a charger attempting to charge, however this is just an assumption. Does anyone have some insights or tips how to deal with this? In practice we expect this to not happen very often but when it happens its a big issue as one has to connect an alternative charging source to the battery in order to bring it back to life. Any support is greatly appreciated.

MPPT ControllersLithium BatteryBMS
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Adam Sherman avatar image Adam Sherman commented ·

If the battery has a built in BMS, what does its documentation say about the situation?

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2 Answers
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kevgermany answered ·

The MPPT thinks there isn't a functioning battery, but keeps trying.

One method is to temporarily connect a second 24V battery in parallel. MPPT sees this, starts charging, 'dead' battery wakes up and starts to charge. Temp battery can be disconnected.

You may be able to get the same result by temporarily connectiong a constant load across the 'dead' battery that's big enough to allow charging to start.

This is, of course, not official policy. The right way to do it is to use a charger which copes with BMS shutdown, like the Phoenix.

Then follow the advice to prevent re-occurence

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pbx avatar image pbx commented ·
Thank you for your answer and insights
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pwfarnell avatar image pwfarnell pbx commented ·
Is the Smart solar set to 24V battery rather than auto detect.
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seb71 avatar image
seb71 answered ·

Does anyone have some insights or tips how to deal with this?

Reduce the energy consumption from that battery or increase the size of the battery and PV array.

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