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wandering-parakeet asked

Battery Protect: Default settings not appropriate for lithium batteries?

I am considering the use of a BP or Smart-BP to protect two 100Ah Battle Born lithium batteries. I was hoping to have the device cut off the load when the batteries had depleted to 20% of their original charge. I have four questions.

1) Given that the highest cutoff voltage on the "non-smart" BP is 12V, I shouldn't use this device, right? 12V corresponds to 9% battery charge left on BB lithium battery. I really want the cutoff voltage to be 12.9V (which corresponds to 20%, according to BB's datasheet). Is there some way to configure a higher cutoff voltage for the non-smart BP?

2) If I shouldn't use the non-smart BP, then I suppose that I could use the "smart" BP. What is the configurable range? Can I set it as high as 12.9V or higher? I'm not sure how I should be interpreting the user manual and data sheets.

3) How would I configure this with a load AND multiple charging sources (e.g., Orion, BlueSolar, and an AC converter)? It sounds like all of the charging sources would need to go directly to the battery (bypassing the BP), and the BP would be between the sources and the load. I would essentially need one bus for power sources and the battery, and a separate bus for all of the loads, with the BP in between. If I put the battery on one bus, and have the chargers and the load on a separate bus, then I run the risk of having reverse current going through the BP when the battery was charging.

4) I have a cheap inverter that I was hoping to use on the load side. I'm gathering from other posts (correct me if I'm wrong) that I should not use either BP (smart or non-smart) with this inverter. Would it be appropriate to have the BP in front of all of the loads EXCEPT the inverter? Then this would suggest that rather than putting the inverter on the "load" bus, I should put the inverter on the same bus as the chargers and batteries. The BP would only protect the battery from "non-inverter" loads. This means that I would not be using the BP to protect the battery when I was using the inverter, but since I would be using the inverter very infrequently, then this should not be much of a problem. Right?

Lithium BatteryBattery Protect
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1 Answer
kevgermany avatar image
kevgermany answered ·

If you're installing a BMV like the Victron BMV 712, there's a configurable relay in it.

I'd work off SOC, not voltage. Too inaccurate.


Charger positives common together to battery positive.

High current relay from battery positive to positive busbar.

Loads to positive busbar.

BMV712 relay which handles light loads switches the heavy duty relay. If you get a good quality solid state relay, the load on the BMV 712 relay/current draw will be negligible.

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