Help!!! Smoke during top balancing

[moonlitsouls]

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.

if wire the battery in series to create one 12v battery , then i should set each power supply to 6v yes?

 

[Bud Martin]

Why do you want to put two power supplies in series to charge 12V batteries when youir power supply is rated up to 30V 5A, not sure what you are trying to do.

https://www.amazon.com/TACKLIFE-DC-Power-Supply/dp/B08HLRDHDB

 

[moonlitsouls]

Why do you want to put two power supplies in series to charge 12V batteries when youir power supply is rated up to 30V 5A, not sure what you are trying to do.

https://www.amazon.com/TACKLIFE-DC-Power-Supply/dp/B08HLRDHDB

i am very new to this so pls bear with me as i try to understand this. Ive done plenty of research but clearly still having a hard time, although this thread has been very helpful. The reason i assumed i would use two is because i could increase the amount of amps

 

[John Frum]

if wire the battery in series to create one 12v battery , then i should set each power supply to 6v yes?

Oh I see what you are trying to do.
12 volts is 3 volts per cell which is darn near empty.
Pretty sure your cells are way beyond that now.

 

[moonlitsouls]

Oh I see what you are trying to do.
12 volts is 3 volts per cell which is darn near empty.
Pretty sure your cells are way beyond that now.

Hey Joey , well i got your msg about the Voltage but i think i misunderstood. So if i rewire in series then i need to charge at 12v bc i now have a 12v battery. Since i have a second power supply, i figured maybe i could use them both together to increase the amps from 5amps to 10amps. But forget that, im making this more complicated than i need to. Heres my plan . wire in series , set up the BMS , get on the APP and adjust the high voltage disconnect. then i will set my power supply to 12v and 4.0 amps and just wait until the first cell hits 3.65 then ill switch back to top balance , thanks to everyone for the time and help

 

[John Frum]

Hey Joey , well i got your msg about the Voltage but i think i misunderstood. So if i rewire in series then i need to charge at 12v bc i now have a 12v battery. Since i have a second power supply, i figured maybe i could use them both together to increase the amps from 5amps to 10amps. But forget that, im making this more complicated than i need to. Heres my plan . wire in series , set up the BMS , get on the APP and adjust the high voltage disconnect. then i will set my power supply to 12v and 4.0 amps and just wait until the first cell hits 3.65 then ill switch back to top balance , thanks to everyone for the time and help

As I have already said12 volts at the battery level is 3 volts per cell.
Your cells are almost assuredly already well beyond 3 volts.
Max charge for your pack is 14.6 volts which is 3.65 volts per cell.
I think you should stop and really think about things before you proceed.
I'm saying this is the nicest possible way
I'll try to answer any questions you may have, as will others I'm sure.

 

[Luthj]

Note that we refer to a 4S pack as a "12V nominal". The charge voltage for a 12V nominal pack is not 12V, but over 14V.

 

[Just John]

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.

I think he means he will hook up the cells into a battery pack with a BMS and use both power supplies to charge.
At least I hope he means he will use a BMS.

 

[moonlitsouls]

I think he means he will hook up the cells into a battery pack with a BMS and use both power supplies to charge.
At least I hope he means he will use a BMS.

Yeah this is what i was thinking. Each of my cells is at 3.32 right now.

 

[Just John]

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

Actually you should be easily be able to get the full 5 amps out of both supplies in parallel.

 

[moonlitsouls]

Note that we refer to a 4S pack as a "12V nominal". The charge voltage for a 12V nominal pack is not 12V, but over 14V.

Ok so if i use one power supply for a 4s pack, i should set the charge voltage to 14.6 correct?

 

[Just John]

if wire the battery in series to create one 12v battery , then i should set each power supply to 6v yes?

If you use a BMS (please use a BMS) you should be able to wire the cells into a battery and charge at 14 volts - 14.6 volts. You would use the power supplies in parallel (not in series). Each positive from the power supplies connects to the battery positive, and each negative connects to the battery negative, and each set at charge voltage (try 13.8 first, if the BMS is good and no cell goes over, then try over 14 volts). My top balanced packs get greater than 95% full when charged to 13.8, should be quick to parallel top balance then.

 

[Just John]

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.

That's an interesting thought. I don't have his power supply, but I do have a cheap 10 amp supply. I might hook it up and see what happens or if anything heats up at max output at varying voltages.

The Longwei I have is identical to the Dr. Meter that Will recommends. Just different names on the plastic. The official Longwei store even sells the Dr. Meter branded supply.

 

[Luthj]

Assemble the cells in a 4S pack (WITH properly configured BMS!). Set the power supply to 14.6V, and then connect to the pack. You can connect both power supplies in this manner (not in series!).

One cell will eventually hit 3.65V before the others. This will cause the BMS to disconnect. Once this happens, disconnect your power supply, set it back to 3.65V, and then connect it to the lowest cell. Once that one is charged to 3.65V, move to the next lowest, and so on. The other cells will drift down over time to around 3.5V. This is normal. They are still fully charged.

 

[Just John]

I am going to do it

Please check the BMS settings and let us know the high cell voltage disconnect and low cell voltage disconnect settings before you start, wouldn't want you to overcharge the cells. Some BMS come with strange default settings, just FYI.

 

[Bud Martin]

Suggestion to OP, once you have BMS connected please upload clear pictures for us to look at and verify that it is hooked up correctly.

 

[moonlitsouls]

Please check the BMS settings and let us know the high cell voltage disconnect and low cell voltage disconnect settings before you start, wouldn't want you to overcharge the cells. Some BMS come with strange default settings, just FYI.

Suggestion to OP, once you have BMS connected please upload clear pictures for us to look at and verify that it is hooked up correctly.

ok guys thanks!

 

[John Frum]

Please check the BMS settings and let us know the high cell voltage disconnect and low cell voltage disconnect settings before you start, wouldn't want you to overcharge the cells. Some BMS come with strange default settings, just FYI.

Also its a very good idea to test things just in case there is a surprise.

 

[moonlitsouls]

Assemble the cells in a 4S pack (WITH properly configured BMS!). Set the power supply to 14.6V, and then connect to the pack. You can connect both power supplies in this manner (not in series!).

One cell will eventually hit 3.65V before the others. This will cause the BMS to disconnect. Once this happens, disconnect your power supply, set it back to 3.65V, and then connect it to the lowest cell. Once that one is charged to 3.65V, move to the next lowest, and so on. The other cells will drift down over time to around 3.5V. This is normal. They are still fully charged.

so with the 12v battery you have a main battery positive and a main battery negative, to wire the power supply in parallel means attaching both leads of each supply to positive and negative accordingly , i am confused about how this 12v battery would be charged in series then?

i thought i understood the concept of parallel vs series, at least in relation to the way the battery pack is assembled. in this case 3.65volts vs 12v

but i was not aware the power supply could be wired parallel vs series as well which is throwing me off now

 

[Just John]

Suggestion to OP, once you have BMS connected please upload clear pictures for us to look at and verify that it is hooked up correctly.

Yes, the output enable button on his supply is unusual in cheap supplies. Most don't have that, and it is actually a good safety feature. It does make it difficult to figure out why his supply wasn't working.