MisterSandals
Participation Medalist
That is NOT even close to being a BMS. That is a battery monitor with alarm and minuscule balancing capabilities.
Problems with charging (overcharge, voltage increased rapidly over 3.5V)
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D
Deleted member 9967
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Wow, you kick puppies as well?
I was given it and it works.
So I used it and it has worked for me so far until today literally.
Also it will balance my cells. It has before and it will do so again. It did it today as a matter of fact.
So I have no clue what you are on about.
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Ampster
Renewable Energy Hobbyist
That is a battery monitor. It has no way to to stop or turn off your charger. It does do some balancing and that can help you solve the problem.
Bob B
Emperor Of Solar
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It looks to me like the cells are out of balance and that was likely the cause of the overcharged cells .... I suspect the balance capabilities of this unit isn't sufficient for the size of your cells.
Since you are charging in series, it is very easy for this to happen. Some cells reach the knee before the others when they are out of balance and the charge levels on those cells can rise rapidly. Bad connections to some of the cells could also cause this.
Sorry, but there is no substitute for a BMS that will disconnect the charge if one or more cells start to run away from the others.
Since you are charging in series, it is very easy for this to happen. Some cells reach the knee before the others when they are out of balance and the charge levels on those cells can rise rapidly. Bad connections to some of the cells could also cause this.
Sorry, but there is no substitute for a BMS that will disconnect the charge if one or more cells start to run away from the others.
Ampster
Renewable Energy Hobbyist
What @MisterSandals is saying is that the Battery Monitor will tell you when your cells are getting close and at that point you are the only one or thing that can turn off the charger, as you have found out.
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Deleted member 9967
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I have said repeatedly I turned off the power.
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D
Deleted member 9967
Guest
ALL of the cells were within.005 volts of each other. [please refer to the video I posted]
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Bob B
Emperor Of Solar
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As you have found out .... That can change rapidly when the upper knee of the charge is reached.
Ampster
Renewable Energy Hobbyist
That is probably true in the short term. The best short term plan is to set the charger to stop when the first cell reaches 3.5 volts.
Longer term there may be other workarounds. Only if she is interested?
MisterSandals
Participation Medalist
I do not know how the OP ever got to this reasoning. She has posted about BMSs over 125 times since July (i searched!). Its a shame She did not mention that She was using an iSDT battery monitor thinking it was a BMS; we could have helped Her had we known (first mention of iSDT in post #40 above).
Hopefully Hers cells are ok and She somehow gets a BMS for Her battery.
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Sharky722
New Member
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I suspected something wrong in #24 but didn't want to assume, but having spent 2hrs reading about the issue still wasn't sure.
I prey for a positive outcome to this due to OP circumstances ? and understand the emotions involved.
What I see in the video is a cell monitor, NOT a BMS. Did someone tell you this would work? Although it claims a balance function, it's designed for RC model batteries. It is NOT a BMS. This is really just a meter, and it would seem like most people who hook up individual cells to make a battery without a BMS, you thought "I'll keep an eye on it".
Yes this thread got more heated than it needed to. But I can understand how emotions are easily strained when (1) there is worry that expensive cells were damaged, and (2) when someone feels they are not being misunderstood.
That said, I also want to underscore what has already been said A Battery Management System (BMS) is not a battery monitor or a simple balancer. A BMS needs be able to monitor, but is also mst be able to intervene automatically to protect the battery.
A battery monitor or a balancer is better than nothing but not a substitute for a BMS, the key difference being the BMS provides automated protection.
I know we have talked about the importance of a BMS before and the risks of foregoing automated protection, and I know you have practical constraints that have kept you from purchasing one, but I would urge you to consider at least a basic one going forward.
For now ^ the above is not the most pressing consideration, just something to consider going forward.
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Where do things stand right now? You have discharged all cells to healthier levels and are letting your Balancer do its thing?
I do think its worth considering what Bob said about your cells possibly being out of balance (I don't recall if they were ever manually top balanced with a benchtop power supply), but if not you may be dealing with unbalanced cells, and a small balancer (like the one you have, or like most of the common BMSes) would not be able to compensate.
That said, I also want to underscore what has already been said A Battery Management System (BMS) is not a battery monitor or a simple balancer. A BMS needs be able to monitor, but is also mst be able to intervene automatically to protect the battery.
A battery monitor or a balancer is better than nothing but not a substitute for a BMS, the key difference being the BMS provides automated protection.
I know we have talked about the importance of a BMS before and the risks of foregoing automated protection, and I know you have practical constraints that have kept you from purchasing one, but I would urge you to consider at least a basic one going forward.
For now ^ the above is not the most pressing consideration, just something to consider going forward.
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Where do things stand right now? You have discharged all cells to healthier levels and are letting your Balancer do its thing?
I do think its worth considering what Bob said about your cells possibly being out of balance (I don't recall if they were ever manually top balanced with a benchtop power supply), but if not you may be dealing with unbalanced cells, and a small balancer (like the one you have, or like most of the common BMSes) would not be able to compensate.
I have a BattGO. Next to useless because it is a sequential (one cell at a time) low-current passive balancer with +/-5mV channel precision.
do by the time is goes it’s thing, cells have settled back into the knee (where the weakest cell is likely to be from the start) and you can have 10% SOC mismatch just due to read precision.
More importantly, it is not a Battery Management System (no cut-off control), it is just a Battery Monitor.
Charging in series without a BMS is just asking for trouble...
The cells may or may not have been damaged, but without a true BMS, this project has little likelihood of success.
do by the time is goes it’s thing, cells have settled back into the knee (where the weakest cell is likely to be from the start) and you can have 10% SOC mismatch just due to read precision.
More importantly, it is not a Battery Management System (no cut-off control), it is just a Battery Monitor.
Charging in series without a BMS is just asking for trouble...
The cells may or may not have been damaged, but without a true BMS, this project has little likelihood of success.
D
Deleted member 9967
Guest
I have top balanced them. Back in October.
I then used them and then charged them up to 3.5 and then used them again and then charged and then used them etc. And then the scooter broke. I got a new used scooter after a few weeks.
The batteries sat on the floor in their box I made for them in October after lowering the voltages 20%. Then I charged them up again like I said and used them over and over with no problems.
I decided to charge the batteries to 3.5 volts after I got the new used scooter. They were not yet connected to the scooter.
I started to charge them and they went nuts.
The rest is written earlier as to what happened.
I then used them and then charged them up to 3.5 and then used them again and then charged and then used them etc. And then the scooter broke. I got a new used scooter after a few weeks.
The batteries sat on the floor in their box I made for them in October after lowering the voltages 20%. Then I charged them up again like I said and used them over and over with no problems.
I decided to charge the batteries to 3.5 volts after I got the new used scooter. They were not yet connected to the scooter.
I started to charge them and they went nuts.
The rest is written earlier as to what happened.
BMS = Battery Management System, not monitor.
Kick puppies? Seriously? Everyone is tiptoeing around the subject, so I'll be blunt. You did something you shouldn't have done, and it is NOT the fault of the vendor who sold you the battery cells. Did you ASK anyone here if the toy MONITOR would work for big honking cells? I feel for you, I really do, but really, the fault lies with your actions and assumptions, not the cell vendor, or the battery MONITOR manufacturer. It's like buying a car battery and hooking it up backwards. You damage things, and nobody to blame except yourself, not the battery manufacturer, not the car manufacturer.
Nobody likes telling you that you did something wrong, but bottom line is that you did.
D
Deleted member 9967
Guest
Yes I was given it as a present by someone here that is rather important I am told.
So yes I asked and then was given this
Anyhow, whatever. You obviously have no clue what is happening so ignoring you.
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She'd have to get a BMS, not really effective to reach over and flip off the power supply (she called it a charger, but it is a bog standard bench power supply). Likely didn't top balance (or bottom balance) the cells, just hooked them up in series. A cell got low, so she "hooked up the charger" and wham, we find out quickly which cells were fully charged, and which were not. I'm sorry, but even if you need a mobility scooter to get around, it isn't right to demand a vendor refund or replace the cells that your lack of knowledge destroyed.
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