Fortres Battery Stack SOC

Luisoler · January 2023

Hello - Have two Fortress eVault Max in parallel. Its been manage by voltage since have not been able to use the schneider SOC logic. On the battery screens there is more that 14% difference on the SOC of each battery display (78.9% vrs 64.7). Voltage reading is the same on each battery. Question is this normal, what would be the max differential in SOC on stack battery.

BB. · January 2023

I tried the Fortress website for manuals... And found some broken links and less than detailed information.

From this quick start:

https://www.fortresspower.com/wp-content/uploads/2021/11/quickstart-guide-REV1.pdf

Image: https://us.v-cdn.net/6024911/uploads/editor/8f/uwa2akje9pcq.png

Are you meeting these numbers? Many BMS (battery management systems) seem to "reset" to 100% when charged to full voltage (54.4 volts in this case)... If the batteries operate at less than 100% full charge for day/weeks/etc., the BMS can drift apart over time (and cycling).

I would suggest contacting your battery supplier or the factory support folks. Because this could involve warranty issues--You need the "official" engineers to work with you... It could be almost anything from "normal" to needing to upgrade BMS firmware. I would suggest that anything over ~10% difference between BMS capacity values should be investigated (just a guess--I have no experience).

-Bill

NMPaul · November 24

I had this problem also, with five batteries. I was advised by Fortress to charge the batteries to 55.4. That fixed the problem, since I normally charge the batteries to 53v to give 75% SOC (according to the %SOC/Voltage table Fortress sent me). One a month I charge them to 54.4 to bring the SOC readings together. If that doesn’t work I do a 55.4 charge as Fortress recommended. I now normally disregard the Fortress SOC figure and go by voltage alone.

Fortres Battery Stack SOC

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