On the two DALY 250 amp BMS I have they will not register amperage below about 3 amps, I figured that out when my compressor frig drew the battery down to about 10% while the BMS still showed 80% soc.
Sorry, I thought for sure you had said 3.97
You don't want to balance when the battery voltage is in the "flat" portion of the charge/discharge curve. It balances voltage, not capacity. You want to balance in the steeper portion of the curve where a small SOC change results in a large voltage change.
Right. And whatever it does do will most likely throw off the top balance.
How are you controlling the Heltec's? Can you simply open the positive lead and they stop working or do you need a 5PST switch or relay to totally shut them down?
The loom is one negative and 4 positives. So it has to stop doing anything if switched so the negative is cut, with only 4x positive leads remaining attached.
I mounted my 4S Heltec’s on the outside of my battery cases, so that I can disconnect them easily.
One would hope so but battery level negative is available from the B- so its "possible" that opening wire 1 does not do what you want. That's on the BMS maker whether there are shenanigans inside.
If anyone figures this out, how to shut down the whole function of the Heltec by disconnecting only one wire, then please post it here. (I could do it by disconnecting either/or the pos/neg and doing a clamp-meter amp-test during a heavy charge but I am about 6 months behind now on my task schedule.) I have been running with my Helecs disconnected after I assume finally getting them top balanced. To repeat the story, the cells I purchased were sold as top balanced but weren't. I'd already mounted them, way over budget and didn't want to order a shop power supply, so while the BMS had the top cut-off at 3.65, I just set the low resume voltage up from 3.45 to 3.63 and after a day on a 14.6 camper lead/acid charger the low-lagging cell that would never go over 3.5V finally slowly crept up to 3.63, which I offically called "done". This charge-fest was also with the assistance of 10A worth of Heltek activine balancing (2 in parallel). So after getting my problem lagging voltage cell up to this new almost-perfect balance, I found that after only one cycle they are close enough together to show I no longer have a problem. Right now I unplugged the Heltecs and am running without them because the cells are all staying remarkably balanced through a cycle but that's just with 30A worth of solar. It may be a different story when I hit them again with the 70A 14.6V to do an almost-quick boost-charge.
I read back up a ways and think I may have misspoken. I think my comments would only apply to how a BMS might work without the negative balance lead connected because a BMS also has a B- wire.
It is a bit ironic that those bullet points for going to "lithium" seem to decrease as we get further along into our builds. At the top of the list for recent years has been "charge at 1x output and be done in no time" to what we see today, "add an expensive B2B converter and be happy with 40A", which is hard to take if you just disconnected a lead/acid bank that was charging at 60A LOL.
I have a Victron bmv-700, a Victron Smart solar 150/100 cc, and 2 jbd BMS on two 280ah packs@12v in parallel. Right this second, at low pv input, they are all within .03v of each other, but at other times, they seem to vary widely. During initial setup, I adjusted my settings to compensate for these variances, but now that I have no real inconsistencies, I guess I will have to pay more attention, and possibly adjust my settings again:/ Regardless, my cc is my primary control. It shuts off charging so that the BMS does not have to. Previously, I had a lesser charge controller, and a 100ah LiFePo4 pack, and the Daly BMS did all charging cutoffs, and that thing was switching on and off constantly through the day, and it was a non-issue.
