Need help with charger problem. 21V Needed

Batteries, Chargers, and Battery Management Systems.
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monsterkali666   100 µW

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Need help with charger problem. 21V Needed

Post by monsterkali666 » Jan 28 2019 11:07am

Hello all
I have a problem charging a small pack.
I have a 18S, homemade battery.
It's made of 18s8p ,Samsung 30A cells (2900mah rated)
The battery is soldered,and i have two bms. a13s one, for series 1-13.
And a second bms, 5s for series 13-18.
For the 13s part of battery,i have a Luna Mini,the 150W one.
For the 5s part, where is the problem ,i don't have any idea how to charge it.
Tried with a 24v 3ah laptop-style charger, it overheated and died in around 15 mins.
It has charged,though,from around 3.750 per cell,to around 3.980.then dead.
I bought today a SMPS 24v 5ah.Same story.Died in around 20mins.
Anyone knows a good charger,that would not die?

e-beach   1 GW

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Re: Need help with charger problem. 21V Needed

Post by e-beach » Jan 30 2019 4:43pm

I am wondering if it was the chargers....

How did the chargers die? Did they just stop working? Did they over heat? Be spicific.

Also, can you tell us about your wiring and post a picture? Make sure they are clear and in focus.


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amberwolf   100 GW

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Re: Need help with charger problem. 21V Needed

Post by amberwolf » Jan 30 2019 8:38pm

Keep in mind that laptop "chargers" are not chargers, they are just SMPS units. The actual charger is inside the laptop.

SMPS units are not by their nature current-limited in a useful way for battery charging without modification, though some are built as "CC" or Constant Current supplies, like some of the Meanwell series, and those *can* be used as battery chargers directly. There are a lot of threads about using a PSU as a chargers.

Most SMPS units with current-limiting are just what they call "hiccup mode" so they simply shut off once the limit is reached.

But not all SMPS units even have current limiting, and if they don't, then when used to charge a battery the current draw may be so high they just burn out trying to reach the voltage they are designed to output. That's probably what happened to yours.


If you want a charger that can do multiple different voltage packs, check out Grin Tech's Cycle Satiator.

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zzoing   10 kW

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Re: Need help with charger problem. 21V Needed

Post by zzoing » Feb 04 2019 11:57pm


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Chalo   100 GW

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Re: Need help with charger problem. 21V Needed

Post by Chalo » Feb 05 2019 1:49am

This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

monsterkali666   100 µW

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Re: Need help with charger problem. 21V Needed

Post by monsterkali666 » Feb 11 2019 1:24pm

Sorry for late answer
I don't have photos right now
About how the chargers died, yes, they overtheated and stopped working.
I found a 20.64v, lenovo charger, with 6.32A
This one charged without problem all the cells, to 4.120 each.
The charger just got "normal" warm.
Still looking after a charger that would charge to 4.2 :)
Thank you for links. I will check them

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Re: Need help with charger problem. 21V Needed

Post by amberwolf » Feb 11 2019 10:53pm

monsterkali666 wrote:
Feb 11 2019 1:24pm
I found a 20.64v, lenovo charger, with 6.32A
It's not a charger.

It's a power supply.

The charger is inside the device powered by the power supply.

Keep in mind the battery can only take so much charge current; each cell type and brand and model is different, but you don't want to exceed that charging C-rate. If you do, you may damage them--slowly, or quickly, depending on how much you exceed the specification for those cells. Exceeding it far enough may cause a fire.

It's also possible to overheat the power supply itself internally until *it* catches fire.


If you want to be certain of operation, you should get an actual battery charger intended for the voltage and current you are after, or one that has adjustments for voltage and current.

Or you can get an adjustable-current & adjustable-voltage "lab PSU", or LED PSU, etc., which are designed to keep a constant current in a very similar way to an actual battery charger.

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