At what voltage your pack reaches 100%

[Namasaki]

@PXSS

I also own a $350 charger that has programmable charge and discharge features

Wow, and I thought I went overboard on my $170 charger

[Namasaki]

@PXSS

I’m sure we could source a BMS from Bestech designed to balance charge at a lower voltage.You can also balance your packs with an RC charger which is what I do

Here are the adjustable parameters:

[PXSS]

Yep. I know. But I also know that you can get customized ones from them too as we do for work

[Eboosted]

I found last week 2 of my cells were 0V, BMS didn’t detect that because I’m using it only for charging.

I don’t want to go over this again and at the moment I have a pack with 2V less than the rest, it’s taking forever to balance on each charge cycle

@namasaki you were right regular brick chargers won’t do the job.

Brick chargers are presetted at 42.3V howewer BMS will stop the charge as soon as the first pack reaches 42V (for protection) and will stop charging completely, leaving lower voltage packs unbalanced.

What we need is to charge the pack at 41V as suggested by @Maxid, sending small current amounts until all cells are filled equally, in this case we won’t need a BMS at all.

So I decided to buy an adjustable balancer charger and forget about all BMS nonesense.

Is there a travel size charger or all of them are big as the DROC and KORAD? or all of them are huge boxes?

[Namasaki]

The one I got really isn’t too big. It is kinda heavy though. It’s a Linear power supply and they tend to be a bit heavy. I use it at home and I still have my 5a brick charger for travel.

[Namasaki]

@Eboosted

What we need is to charge the pack at 41V as suggested by @Maxid, sending small current amounts until all cells are filled equally, in this case we won’t need a BMS at all.

I would keep the bms because as in your case, you have one cell group that’s not taking a charge, you might wind up charging 9 cell groups to 41v or 4.5v per cell group which could be a real problem.

[Eboosted]

Were your cells perfectly balanced after the first charge on the Korad?

Are you charging until 42V or less?

How do you charge your cells if the charger does not have a laptop plug, do you have an addapter?

[Namasaki]

I haven’t pulled the enclosure and checked them after fully charging. I will do that in the next couple days and report back. I am charging to 42v but I usually stop when the power supply output drops to around 50ma. When I start charging, its in CC mode with 5a and voltage just a little higher than the battery. As it charges the voltage output increases as the battery voltage increases. Once the battery gets to around 90%-95% the power supply switches to CV mode and the voltage is at 42v and the current start to decrease as the battery fills. I made a charge cable with banana plugs on one end to plug into the charger ports.

[Eboosted]

@Namasaki

I would keep the bms because as in your case, you have one cell group that’s not taking a charge, you might wind up charging 9 cell groups to 41v or 4.5v per cell group which could be a real problem.

If this happens how would the charger fill the half-charged cells?, BMS would detect a cell with 4.2V and stop all charging activity leaving low charged cells still unbalanced.

I guess in this case it’d be better to charge at lower voltage, once all packs are balanced, charger would continue the charge all the way to 4.2V for each pack.

[Namasaki]

If I understand correctly, the bms monitors each cell or cell group and when they reach the detection voltage, it starts trimming them down. On my bms the detection voltage is 4.28 Hobby chargers continue to fill low cells while trimming higher cells once they are full. I think the bms will do this also IF the charger will continue to supply low amperage charge while the full cells are being trimmed. This is where the adjustable power supply rocks. And the brick charger falls short. I’m gonna do a test in next couple days. I’ll pull the cover off and record all cell voltages before charge and again after full charge and I’ll get back to you with the results.

[Eboosted]

I’d like to buy an adjustable charger or hobby charger for this purpose but really don’t want to buy one as big as yours, it’s difficult to carry around, I wonder if that’ll be the only alternative

[Namasaki]

If you can find a hobby charger for 10s, it will be expensive. If you use a power supply, it will need to be a CC/CV with adjustable voltage and current. Commonly they come in 30v and 60v versions. So for 10s you would need 60v. You could save money by getting a 3a version. As far as size and weight, it is what it is.

[Eboosted]

I wonder if this one would work:

https://www.amazon.com/Digital-Adjustable-Regulated-Stabilizer-Supply/dp/B01N6AHGTG/ref=pd_sbs_469_6?_encoding=UTF8&pd_rd_i=B01N6AHGTG&pd_rd_r=0H79F16T09Y6XBJ6746J&pd_rd_w=y8AHl&pd_rd_wg=VXgWB&psc=1&refRID=0H79F16T09Y6XBJ6746J

[smurf]

10 amps

https://www.circuitspecialists.com/bench-power-supply-csi6010x.html

[Namasaki]

@Eboosted

I wonder if this one would work: amazon.com Digital Adjustable Regulated Stabilizer DC Power Supply 60V 5A Features: 1. Leading technology: new PWM switch for voltage stabilization, MOS linear secondary voltage stabilization 2. Energy-saving and high efficiency: over 80% high efficiency, 40% higher than $65.99

It has CC AND CV so it should work.

[Namasaki]

@smurf

10 amps 60 Volt Adjustable Linear DC Power Supply, 10 Amps

I didn’t see a price on the link but it looks expensive.

[smurf]

Ya I know I would like to get a powerful charger but there just so expensive.

[Okami]

Im sorry guys for cutting your power supply / charger talk short but I wanted to ask @PXSS one question directly

@PXSS

As I said, I’ve discharged tens of packs down to 2.5V for hundreds of cycles. Look up the spec sheets, manufacturers do it all the time too.

With this - do you mean rest voltage or under-load voltage?

---

I tried to bring my cells to 2.8v rest voltage… but they were weak as fuck so to speak at already 3.1v rest voltage or so…

At using the cells with 3.0v rest voltage, the voltage started to ‘‘dip into red zone’’ - of 2.3v or so under load at 2.5 A of load per cell. These are 10A capable cells, so the load was about 0.25c when on their weak side…

---

So - @PXSS what do you consider ‘‘red zone’’ for cells under load? How much voltage sag have you experienced and how much sag is ‘‘normal’’ and can be sustained?

I might as well go into this on the old voltage sag topic… but since u mentioned 2.5v I got interested…

[PXSS]

@Okami. Stuck in traffic, so short answer is 2.5v under load. 2.5v is your absolute minimum. Can be more detailed later

[Okami]

@PXSS Cool. Thanks for letting me know! yeh more detailed answer would be nice… if it gets too lenghty u might as well write to me in private!

I think this is a bit misleading that 2.5v is not ‘‘marked’’ as no load voltage… since it is not always possible to determine what is the rest voltage at this level or when battery has already depleted itself…