By the time I reach high voltage disconnect the charge rate has reduced to less than 5 amps. I assume the bms is doing that.
New Battery on Amazon and Ebay - Global Power 12V100AH LIFEPO4 - $399! Has anybody actually bought one yet? Torn it down yet?
- Thread starter Indepthdude
- Start date
SolarRat
Solar Addict
Wild's explanation makes sense. Another reason might have to do with the way lithium cells behave when nearing full. On a lead battery, the higher its voltage goes the harder it is to increase it further. On a lithium cell, once it reaches a certain voltage it will quickly increase in voltage even at low charge levels. So it's possible your faster charge is moving the lower cells more before the inevitable cutoff from the highest cell?
I agree the meters are not accurate
SolarRat
Solar Addict
Are the batteries cutting off, or is the inverter cutting off? Either way, why run them that low?
SolarRat
Solar Addict
That is your charge controller switching from constant current to constant voltage, not the bms.
No usually just 2 or 3, and they're the ones that were on during charging.
as far as the low voltage disconnect goes,in all probability- either you have 1 weak or badly out of balance cell (which is technically 20 cells wired in parallel) it's hitting the 10v cutoff and shutting down the bms. As far as the charge voltage going way higher than the battery voltage at the top end @ higher amps,I can definitely confirm that. it had me screaming in frustration trying to program a growatt aio to behave properly. vis a vi charging profiles. getting the charger to cut out before the bms at both high amperage charge and low amperage charge rates proved challenging/impossible
The Dish Doc
Photon Pharmer
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I’m just testing to see if the batteries will reach the stated cutoff points. I’m close at high voltage cutoff but I miss low cutoff by 6 volts. 1.5 volts each battery.
I was thinking it might be a balance issue. I’m hoping the balance boards will help with that. I will run another discharge and charge cycle to see what low cutoff is and to see if my ah is going up or down. Then I think I will set my charge profile a bit conservative but still in the range of keeping the balance boards running and my inverter low voltage shutdown above whatever my low voltage cutoff is now and see what happens.
The Dish Doc
Photon Pharmer
Then you'd be "Up LifePooh creek without a paddle"
SolarRat
Solar Addict
Has anyone got these boards to do a damn thing? I wasted enough time with these crap batteries. I just deleted a long rant post, but I gotta tell ya, I'm pissed.
I attempted to do a final amp hour test but I wasn’t able to be very accurate because I had a setting incorrect on the charger and it stopped charging before the batteries were full But I’m very close to 100ah. I think the balance boards have helped but they have such a short range that they balance in and such a small amperage that they balance at it’s going to take a lot of cycles to make any difference. I set my charger at 56.8 volts for the top and inverter for cutoff at 47 volts. I’m going to let it operate for a few months and see what happens.
SolarRat
Solar Addict
An amp hour test won't really tell us much, because we still don't know how many amps the cylindrical cells are. For all we know they could be grade B 6amp cells * 20 = 120ah, but with such poor balancing they sell as a 100ah battery (lifespan will be very short if this is the case). Some of my cells never reach 3.4v, while others are killing themselves at 3.65+.
I've been cycling for three days straight with these balancers, at least 5 cycles a day. And I've bled the high cells lower than the low cells 3 times now. If anything, the balance got worse. BMS still disconnects around 13.7v. Here is the better of the two batteries:
Day 1 start Day 4 start
3.427 3.428
3.340 3.340
3.340 3.340
3.406 3.410
Cells 2-3 never go above 3.37 when charging, then settle back to 3.34.
I'm charging that battery with a bench supply at very low amps (under 1).
The other battery I'm just charging with a 10 amp charge controller till cutoff, then draining with a 10 amp load, then charging again. CC is set to 13.8v. I think the BMS is starting to fail as I now have to disconnect the sense wires all the time to restore power to the terminals.
Anyone got a link to a decent, cheap BMS, in the US?
I've been cycling for three days straight with these balancers, at least 5 cycles a day. And I've bled the high cells lower than the low cells 3 times now. If anything, the balance got worse. BMS still disconnects around 13.7v. Here is the better of the two batteries:
Day 1 start Day 4 start
3.427 3.428
3.340 3.340
3.340 3.340
3.406 3.410
Cells 2-3 never go above 3.37 when charging, then settle back to 3.34.
I'm charging that battery with a bench supply at very low amps (under 1).
The other battery I'm just charging with a 10 amp charge controller till cutoff, then draining with a 10 amp load, then charging again. CC is set to 13.8v. I think the BMS is starting to fail as I now have to disconnect the sense wires all the time to restore power to the terminals.
Anyone got a link to a decent, cheap BMS, in the US?
Are you disconnecting the charger after the bms trips or leaving it hooked up? I would leave it hooked up at >1a and walk away. The balance board will bleed the high cells until the bms turns on then the whole bank will charge... rinse repeat until balanced. I started a new one balancing last night, this morning 3 cells are above 3.45, I'll update when all 4 are. Imo these don't work nearly as well as active balancers, but they do work. Remind me what voltage you are running and I'll try to find a good replacement bms if you want to go that route, but if I where you and these don't/ won't work to spec, I'd just return them for a full refund.
SolarRat
Solar Addict
Leaving them on, shutting them off, and a combination of the two. On one battery, I tried the bench power supply I from 200ma to 3 amps . On the other battery I just let the 10amp charge controller do its thing. After a while with 10amps the bms would just trip and stay tripped. Unplugging the balance connector on the bms itself usually resets it. The last time it took a while for it to reset. I don't think the bms's can handle cycling like that.
But, I haven't tried leaving them overnight banging the bms limit. It can't be good for the high cell, bms, or the charger/PS. But at this point, why not. I'll go set the PS at 1.5a and walk away. I've kept it going for a few hours <1a at least once, but with no change on the low cells measured on the Fluke I called it quits. I had to keep a fan on the balance board...it is working overtime, but all it seems to be doing (using clamp meter) is shunting the high cells to ground at 225ma.
I did order the 5a active balancer a couple months ago, but before installing I came back to this thread for updates and saw that there was a plug and play solution (and my JST cables haven't gotten here from china yet). Maybe I'll rig it up when the connectors come.
Originally, I ordered 1 of these batteries to see if they were good enough to buy more for my 36/48v golf cart and boat. The first wasn't working right so he sent another which did the same. I kept them both at a discount figuring I'll just top balance them and all would be well. LOL. So now I have two, and I'd really like to be able to buy one or two more for a matching set...but at this point it seems I'd be better off starting over and building one...but now is not the time to be ordering from China, so I keep trying to get these workable...
As far as the connectors here, You can have them by Thursday. As far as replacing the bms for 12 or 24v use is pretty easy just about any 4s jbd will work, if you need 48v though it's much harder and more expensive with individual internal bms's. Much more cost effective to go to an external 16s bms
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ok I've been continually float charging this one since this post was made. All cells are now resting @ 3.437 to 3.442. When I hook the charger up the bms doesn't cut out until the whole battery is over 14.5. I'd say their balanced. Now I'll cycle a few times and see if the ballancer is enough to keep them that way.
I have been busy the last few week getting the 10 solar panels I had temporarily resting on cement blocks over at the camp mounted on my rv roof. I was able to get them on and connected last week and disconnected the rv from shore power. So for The last 5 or 6 days my batteries have short cycled 4 or 5 times a day and one deeper cycle overnight. ( I set it up that way so the balancers would be constantly working) My 48v pack reached 58.4 volts on the AIO readout 58 volts on my multimeter on today’s see how high I can go test charge.Well into the range the batteries are listed for. The balancers must be working. I was hitting high voltage cutoff at 56 volts before I installed the 48v active balancer and with the internal balancers I have gone from 56.6 to 58.4 as high as my charger will go they must be working they are just very slow. I also noticed that the balancers are barely getting warm now until I am almost at max voltage.
Well, I installed the balancers without incident. We took our camper out this weekend for the first time and the batteries were dead when we got there. They showed fully charged (13.4V) but with any kind of load on them they were effectively drained (9.4V) and couldn't even power the trailer 5W LED lights. Fortunately, we had an electric site and I let them charge for 24 hours, but it didn't make any difference.
When we got home, I took them apart and there was a significant amount of char inside both batteries that looked like it emanated from the BMS. I wracked my brain for anything that I could have done wrong, but I have no clue. There was only one way to put the balancers in.
I have contacted Global Power and requested a refund; he said he would take care of it, but still waiting. We have a two-week trip coming up in a little over a week and can't do it without batteries.
When we got home, I took them apart and there was a significant amount of char inside both batteries that looked like it emanated from the BMS. I wracked my brain for anything that I could have done wrong, but I have no clue. There was only one way to put the balancers in.
I have contacted Global Power and requested a refund; he said he would take care of it, but still waiting. We have a two-week trip coming up in a little over a week and can't do it without batteries.
Sorry to hear about your trouble. I have 5 of these batteries and haven’t had any trouble with them since installation of the balancers. We are using them every day now that we are boondocking and they are working great. Knock on wood.