Help!!! Smoke during top balancing

[Just John]

After 12 hours my battery cells have not charged at all

First, take the one that didn't emit magic smoke, and clip the leads to your Voltmeter probes and verify it is putting out 3.65v. For the time being, put the one that smoked aside. If you confirm the output, then it just takes a few days to put that many amps into the cells.

 

[moonlitsouls]

You can't tell by voltage until nearly the end.
The charge curve is very flat except for the extreme ends.
If there is current going into the cells then they are charging.
I think we already did the math for you, confirm?

They are still only at 3.32 though , that’s normal?

 

[moonlitsouls]

Also I don’t have room on the edge of my bus bars to attach the alligator clips so I had to put them inside the stud , is that ok? I checked the voltage coming off the leads and it’s correct. I also tightened down the studs and nuts with a wrench. Previously only tightened by hand bc will said on his YouTube video not to over tighten

 

[Hedges]

If supply meter shows amps flowing, batteries are charging and you just have to be patient.
Between cell capacity x quantity and charge current, you can calculate how long from 50% or 70% discharged until fully recharged.

If still using skinny wires and alligator clips, supply will hit CV and battery will be at lower voltage, charge current lower, so it will take longer.

 

[Just John]

They are still only at 3.32 though , that’s normal?

Very normal. Some others did the math for you earlier. Patience. Once it finally gets above 3.4 volts on the cells, the voltage will increase more rapidly. It just takes a long time.

 

[Just John]

280 Ah x 4 in parallel = 1120 Ah.
You could try to look up what 3.29V at rest is as far as SoC. I'm lazy. Assuming 50% ...
560 Ah to go / 8A (assuming 80% of max on your replacement supply) = 70 hours or 3 days.

Not so bad to keep it simple.
Maybe it's a bit longer as current tails off. But you're only doing a 12V pack not 48V, so it isn't 2 weeks.

Yes, Hedges is accurate, the cells SHOULD ship between 20 and 50% state of charge. SHOULD is the operative word, since some of mine were shipped above 95%. So it could take 3 days, or up to a week. Patience please.

 

[Just John]

Also I don’t have room on the edge of my bus bars to attach the alligator clips so I had to put them inside the stud , is that ok? I checked the voltage coming off the leads and it’s correct. I also tightened down the studs and nuts with a wrench. Previously only tightened by hand bc will said on his YouTube video not to over tighten

Be careful tightening these, lots of people have stripped the threads since the aluminum terminal is quite soft. That's why most people (like you) use grub screws, set screws, or whatever you want to call them. You can use an allen wrench to hold the grub screws in place and tighten the nuts, but still be very careful.

 

[Bud Martin]

Not sure what I’m doing wrong

Your post #33, I am not convinced this power supply is working due to the fact that it shows 4.6A without load connected and 0VDC on your meter.
BTW, it took over 20 hours at 15A charging rate to charge my one 280Ah battery.

 

[Bud Martin]

I could be wrong, but at 3.65 volts out of 30, they are likely below 80%.

I am talking about current, 5A is the max current it can hadle at any output Voltage.

 

[blutow]

I do have a BMS that I planned on installing when I assembled the battery pack. I want to keep this process as simple as possible. Ok I attached my multimeter to the power supply where the alligator lines plug into and there is no volts , is that the correct way to verify output ?

I'm all for simplicity, but it should only take 5 -10 minutes to wire up the BMS and do the initial charge at 12v. Even better if you have a 12v charger that can push more amps. Once you get them mostly topped off (at BMS cutout), top balancing in parallel is quick.

If you look at it in terms of watt hours, it really highlights the speed difference:

• 4 of those 280ah cells hold about 3640 watt hours.
• Traditional parallel balance at 3.25v and 5a, it would take over 9 days to completely charge those cells from empty (you are charging at only 16.25 watts).
• Put them in series with a BMS and use a real 12v charger at an average of 13v at 90a, it would take ~3 hours to fill them from empty (you are charging at 1170 watts, so 72x faster than the parallel approach using a cheap 5a power supply

I think my math is right there. Anyway you slice it, charging these huge cells at 3.x volts and 5a is a huge exercise in patience. Not something I have.

 

[Just John]

I am talking about current, 5A is the max current it can hadle at any output Voltage.

Usually (note USUALLY) the limiting factor is heat dissipation. Slightly over 18 watts will not place a significant strain on the supply. I could be wrong, but I would have no qualms about running a 150 watt rated power supply at under 20 watts, and I'm quite conservative. I've run my 40 amp Tekpower supply for many hours on end at 40 amps, 3.65 volts, since it is rated at 15v, 40 amps. If I were to run it at 15v, I would limit it to 35-37 amps, but I've also run it for many hours at 13.8v and 40 amps. Now, how well built is a VERY CHEAP Chinese power supply? Probably not very, but running it at 5 amps shouldn't be a problem at this voltage. I could be wrong, but under 20 watts is really not much.

 

[Just John]

I'm all for simplicity, but it should only take 5 -10 minutes to wire up the BMS and do the initial charge at 12v. Even better if you have a 12v charger that can push more amps. Once you get them mostly topped off (at BMS cutout), top balancing in parallel is quick.

If you look at it in terms of watt hours, it really highlights the speed difference:

• 4 of those 280ah cells hold about 3640 watt hours.
• Traditional parallel balance at 3.25v and 5a, it would take over 9 days to completely charge those cells from empty (you are charging at only 16.25 watts).
• Put them in series with a BMS and use a real 12v charger at an average of 13v at 90a, it would take ~3 hours to fill them from empty (you are charging at 1170 watts, so 72x faster than the parallel approach using a cheap 5a power supply

I think my math is right there. Anyway you slice it, charging these huge cells at 3.x volts and 5a is a huge exercise in patience. Not something I have.

Shorter version:

If you have a BMS with the correct high voltage cell disconnect setting, charging in series is 4 times as fast.

 

[blutow]

Shorter version:

If you have a BMS with the correct high voltage cell disconnect setting, charging in series is 4 times as fast.

4x as fast if you are still using the same cheap bench top power supply. If you have access to a real battery charger pushing reasonable amps, that can add to the speed dramatically.

 

[Just John]

4x as fast if you are still using the same cheap bench top power supply. If you have access to a real battery charger pushing reasonable amps, that can add to the speed dramatically.

I usually use either my Riden or my Tekpower both of which are indeed considerably faster. I have found a newer power supply that looks really good for the price:

150.99US $ 30% OFF|Wanptek Adjustable Dc Power Supply 60v 20a Laboratory Bench Source Stabilized Switch Power 30v 10a Ac 220v Ac110 500w 1000w Diy - Switching Power Supply - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

60 amps at up to 15 volts, around $200. Looking at the pictures, I suspect the same company manufactures it as the Tekpower (which is really high quality work inside, and given me zero problems).

Some others I think look good (I don't own them, so can't really say):

30v at 10a on Amazon (cheapest I could find with 4 digit display although I wouldn't trust the accuracy):

Amazon.com: DC Power Supply Variable 30V 10A 4Digital LCD Display, Adjustable Regulated Switching Power Supply with Alligator Leads Power Cord: Computers & Accessories

Amazon.com: DC Power Supply Variable 30V 10A 4Digital LCD Display, Adjustable Regulated Switching Power Supply with Alligator Leads Power Cord: Computers & Accessories

smile.amazon.com

Another with much better quality alligator clips/leads (I do own the more expensive version of this):

DC Power Supply Variable, 0-30 V / 0-10 A LW-K3010D Adjustable Switching Regulated Power Supply Digital, with Alligator Leads US Power Cord Used for Spectrophotometer and lab Equipment Repair: Amazon.com: Industrial & Scientific

DC Power Supply Variable, 0-30 V / 0-10 A LW-K3010D Adjustable Switching Regulated Power Supply Digital, with Alligator Leads US Power Cord Used for Spectrophotometer and lab Equipment Repair: Amazon.com: Industrial & Scientific

smile.amazon.com

This one I actually own, it has no problem putting out 3.65v at 10a for at least 4 days (and much better than most alligator clips leads):

DC Power Supply Variable 30V 10A, 4-Digital LED Display, Precision Adjustable Switching Regulated Multifunctional Power Supply Digital with USB Interface, Disply with Output Power Lab Grade: Amazon.com: Industrial & Scientific

DC Power Supply Variable 30V 10A, 4-Digital LED Display, Precision Adjustable Switching Regulated Multifunctional Power Supply Digital with USB Interface, Disply with Output Power Lab Grade: Amazon.com: Industrial & Scientific

smile.amazon.com

 

[Hedges]

Usually (note USUALLY) the limiting factor is heat dissipation. Slightly over 18 watts will not place a significant strain on the supply. I could be wrong, but I would have no qualms about running a 150 watt rated power supply at under 20 watts, and I'm quite conservative. I've run my 40 amp Tekpower supply for many hours on end at 40 amps, 3.65 volts, since it is rated at 15v, 40 amps. If I were to run it at 15v, I would limit it to 35-37 amps, but I've also run it for many hours at 13.8v and 40 amps. Now, how well built is a VERY CHEAP Chinese power supply? Probably not very, but running it at 5 amps shouldn't be a problem at this voltage. I could be wrong, but under 20 watts is really not much.

Remember, this is a switching power supply. Running 100% current could be maximum stress for some components even if it is 10% power.
In fact, he is doing 90% voltage decrease and 100% current, high by two measures.
Would probably be under less stress (for portions of the circuit) delivering 28V at 5A.

 

[moonlitsouls]

Your post #33, I am not convinced this power supply is working due to the fact that it shows 4.6A without load connected and 0VDC on your meter.
BTW, it took over 20 hours at 15A charging rate to charge my one 280Ah battery.

hello , the problem was i had to push the "output" button , for it to actually work. Which BTW is does not say anywhere in the manual. I tested the voltage and the base of the machine where the alligator leads plug in, i also attached the alligator leads to the multimeter and it confirmed its working again. I am going to wire them in series as recommended and report back .

 

[moonlitsouls]

Remember, this is a switching power supply. Running 100% current could be maximum stress for some components even if it is 10% power.
In fact, he is doing 90% voltage decrease and 100% current, high by two measures.
Would probably be under less stress (for portions of the circuit) delivering 28V at 5A.

I am going to wire them in series as recommended and report back .

 

[moonlitsouls]

Shorter version:

If you have a BMS with the correct high voltage cell disconnect setting, charging in series is 4 times as fast.

I am going to do it

 

[moonlitsouls]

4x as fast if you are still using the same cheap bench top power supply. If you have access to a real battery charger pushing reasonable amps, that can add to the speed dramatically.

well i have two of these already so i can get up to 8 amps easily, will wire in series thanks for the help

 

[John Frum]

well i have two of these already so i can get up to 8 amps easily, will wire in series thanks for the help

Stop!
If you wire the chargers in series the voltage doubles.
3.65 x 2 = 7.2 volts.
That would be very bad for your cells.
serial aggregates voltage
parallel aggregates current

They are already effectively wired in parallel as they are both attached to the inter-cell busbars.