QUCC relay BMS : troubles

[scpanish]

Same behavior for charging. It needs somewhere between 5 and 10 amps @24V to close the relay and start charging. That isn't really a disaster as purely a protection device (which will ideally never be triggered) but it is certainly suboptimal.

Oh well. At least it didn't totally fail to act as a relay, always pass power, and then fry like my Chargery DCCs! And much cheaper.

 

[scpanish]

One additional note. I put the QUCC pack in parallel with a pack equipped with a JK BMS and allowed the charge level to rise to the identically set over voltage setpoints. Both BMSs cut off charging as they should. The JK reenabled charging when the voltage dropped and the pack was functional. The QUCC reenabled charging, but the relay did not close, perhaps because the JK was at that point handling all the discharge. I disabled discharge on the JK and the QUCC immediately closed the relay and resumed normal functioning. I asked QUCC support about this behavior and was told that the relay BMS cannot be used in parallel. So for those of us building systems to run a house, where parallel packs are necessary, this BMS is a poor choice. It may however be OK where a single pack is adequate. My system now has JK BMSs on both packs, in parallel.

 

[burgerking]

I asked QUCC support about this behavior and was told that the relay BMS cannot be used in parallel.

JK also officially said their BMS is not to be used in Parallel (either with another JK or with other BMS).

 

[timselectric]

JK also officially said their BMS is not to be used in Parallel (either with another JK or with other BMS).

That's because multiple batteries in parallel have a short circuit current that is higher than the BMS can control. (Internal OCP) but the difference is that they still work in parallel. And can be protected externally.

 

[scpanish]

Yes, I have 175A SF (semiconductor fuse) fuses on the positive bus connections from each pack. Those are the fastest fuse class. Just in case. But JK now says their BMS can be used in parallel so long as proper fuse or diode protection is in place. They even copied a diagram from users of this website and gave credit for it on their website.

 

[timselectric]

Yes, I have 175A SF (semiconductor fuse) fuses on the positive bus connections from each pack. Those are the fastest fuse class. Just in case. But JK now says their BMS can be used in parallel so long as proper fuse or diode protection is in place. They even copied a diagram from users of this website and gave credit for it on their website.

I'm putting 14 in parallel, with zero concerns.