Charging big battery packs with large power supplies

[Alexanderfoti]

Hi all!!

I need to charge a Li-ion pack that is 26S, to a nominal voltage of 107.9VDC (4.15V per cell).

I have a few chargers I have found on Aliexpress

https://www.aliexpress.com/store/product/Li-Ion-Battery-72v-3A-4A-5A-6A-7A-8A-9A-10A-11A-12A-Adjustable-Current/4450039_32914065128.html?spm=2114.12010612.8148356.18.792d1fa7wPkbW1

This, and and most others, will do CC at 12A until they hit a certain voltage, and then switch to CV mode.

One seller sent me this:

https://www.aliexpress.com/store/product/3000W-Big-Power-0-90v-0-120v-Adjustable-Lithium-Battery-Charger-0-30A-Adjustable-Charger-for/4450039_32964180998.html?spm=2114.12010612.8148356.2.792d1fa7wPkbW1

As far as I can tell, this is just a large power supply with no CC/CV circuit. I can set an upper voltage limit and a current limit, so I assume it will dump current into the pack at the set current (25A for example) until it reaches the output voltage of the charger, but will taper off, and not have an intelligent control.

If anyone can give me any advice, I will be much appreciated.

 

[john61ct]

Hi all!!

I need to charge a Li-ion pack that is 26S, to a nominal voltage of 107.9VDC (4.15V per cell).

I have a few chargers I have found on Aliexpress

https://www.aliexpress.com/store/product/Li-Ion-Battery-72v-3A-4A-5A-6A-7A-8A-9A-10A-11A-12A-Adjustable-Current/4450039_32914065128.html?spm=2114.12010612.8148356.18.792d1fa7wPkbW1

This, and and most others, will do CC at 12A until they hit a certain voltage, and then switch to CV mode.

One seller sent me this:

https://www.aliexpress.com/store/product/3000W-Big-Power-0-90v-0-120v-Adjustable-Lithium-Battery-Charger-0-30A-Adjustable-Charger-for/4450039_32964180998.html?spm=2114.12010612.8148356.2.792d1fa7wPkbW1

As far as I can tell, this is just a large power supply with no CC/CV circuit. I can set an upper voltage limit and a current limit, so I assume it will dump current into the pack at the set current (25A for example) until it reaches the output voltage of the charger, but will taper off, and not have an intelligent control.

If anyone can give me any advice, I will be much appreciated.

LI batteries do not need an "X" stage charger, a simple power supply will do just fine.

It is not the regulator in any case that determines the CC to CV transition, but the batt chemistry and its acceptance rate profile, SoC and current rate.

For most chemistries, at a healthy charge rate (low C) that transition happens at such a high SoC, you could dispense with CV entirely, unless the last few percent of range is critical to you.

At a high rate less suited to longevity, the transition is earlier, but we're not talking about more than a few minutes in either case.

To prevent overcharging, you should be standing there with your ammeter showing bank acceptance.

A regulator automating the cutoff based on your endAmps setpoint would be nice, but you should regularly check on its accuracy and have a redundant cutoff for safety.

 

[john61ct]

I need to charge a Li-ion pack that is 26S, to a nominal voltage of 107.9VDC (4.15V per cell).
…
will do CC at 12A until they hit a certain voltage, and then switch to CV mode.

The first sentence implies no CV needed, just charge to that voltage setpoint and stop.

As stated if a low enough current, that can get you to a very high SoC, and is safer for bank longevity. Where did you get that termination voltage? What is the batt specific chemistry? Link?

> As far as I can tell, this is just a large power supply with no CC/CV circuit.

There is no such circuit, or at least, such is not needed.

A charger with built-in "intelligence" to terminate should be fully user-adjustable, based on hitting the voltage setpoint, or that + an adjustable Absorb Hold Time, or, if real precision is required to maximize SoC without overcharging, based on endAmps.

I have not seen such chargers.

And you should not be relying on automation and leaving it unattended anyway IMO.

 

[pullin-gs]

Bulk charging large packs with a regulated (voltage AND amps) powersupply works fine in theory.....however any imbalanced or defective cells would reach their 4.2v maximum while other cells are below that, thus pack (and fully charged cell) is still recieving current while other cells "catch up". This is a dangerous condition and very bad things can happen.

Study up on BMS systems which can disconnect charging system when any single cell reaches 4.2v.

 

[999zip999]

How many ah is this pack and what will it be used for.

 

[john61ct]

Yes the need for balanced cells is important, especially if old or of inconsistent quality to start with.

With large top quality LFP prismatics in low C-rate applications and with proper care, it is possible to go many years without re-balancing required, just checking periodically.

And with regular balance charging, you don't need to use a BMS for that function anyway.

 

[leffex]

I have a few chargers I have found on Aliexpress

https://www.aliexpress.com/store/product/Li-Ion-Battery-72v-3A-4A-5A-6A-7A-8A-9A-10A-11A-12A-Adjustable-Current/4450039_32914065128.html?spm=2114.12010612.8148356.18.792d1fa7wPkbW1

This, and and most others, will do CC at 12A until they hit a certain voltage, and then switch to CV mode.

One seller sent me this:

https://www.aliexpress.com/store/product/3000W-Big-Power-0-90v-0-120v-Adjustable-Lithium-Battery-Charger-0-30A-Adjustable-Charger-for/4450039_32964180998.html?spm=2114.12010612.8148356.2.792d1fa7wPkbW1

I was thinking about the first one you have got for a while, the second one on your list I bought. Its in transit or do you say shipped back and forth in my town right now, I don't know what they are doing honestly. "You've got one job..." I'm going to collect it tomorrow in the morning and can write a line here later. I think an upgrade of fan and cooling is a good thing to do and also add silicon compound inside as I will use it as a charger that I bring with me on my bumpy rides.

 

[Alexanderfoti]

Sorry guys/girls. I didn't see the responses to this thread.

Charging at 20Amps on a 26S pack (leaf modules), should be fine, and as you say, won't require the need for a charger that "switches" between cv/cc mode.

I have reader 107.9V as I have a 26S Leaf pack. This ends up being 4.15V per cell (at "fully charged" setting of the charger I use".

The pack is not managed by a BMS, but I do check the call balancing every charge with a Cellinfo meter, and they are all within .1v within each other. I discharge down to 45AH consumed current, but haven't checked the pack voltage at that level yet. It should be 60AH worth of capacity, but depends on how I treat the pack of course.

Looking at the aliexpress listing, it looks like a modified Huawei DC power supply, used in mobile phone systems. Makes sense, I have ordered one and we will see what turns up and at what voltage it runs unloaded.

Thanks all!

 

[amberwolf]

FWIW, I think both of you would be better off with the Meanwell HLG LED PSUs (lots of threads and posts about them here), as they are already sealed and potted, and adustable voltage and current (in the "A" versions).

You may need to series and/or parallel multiple units to get the voltage and current you need, but they can be bolted onto the bike/vehicle and wired in. (if you think you'd leave the bike/etc sitting unused for a long time you can add a switch between the charger and pack, so it doesn't drain the pack via the "on" LED in the charger.)

Because they're sealed and potted, they're heavier than the equivalent fan-cooled unit, but they are silent, and can operate at their max power without cooling other than being in open air. (mine is mounted under the SB Cruiser trike's cargo/seatbox, to charge a 14s 2p EIG NMC pack at about 12A, or about 0.33c).

 

[Alexanderfoti]

That is part of the issue on the bike, is that there is not enough space for HLG's for my pack. I would have to series 2 units and parallel 3 units to get the same current capacity as one of the other PSU's.

There is of course not a bad idea to make a "home" charging station for faster recharges at home, but It would be nice to charge at 3+KW at public charge stations with an an adapter and an onboard charger.

 

[flippy]

just get 2 of the mean well SP-750-48.

that will give you 1.7kW on 108V easy.
you will be hard pressed to get more power in a smaller space. you can also get the 480W models, those are considerably flatter.

if you got money to burn you can use a RST-5000-48,2 of those to get 100V+ and then you can charge at 12kW...

 

[eee291]

https://www.ebay.co.uk/itm/1PC-new-Eaton-APR48-3G-communication-power-supply/172613169456?hash=item28308bf130:g:nC0AAOSwc49Y7Yfp&frcectupt=true

Two of these in series can supply 3.6Kw
Mod thread: https://endless-sphere.com/forums/viewtopic.php?f=2&t=66169

I can also help program these without opening them since I have the original Programmer.

 

[john61ct]

if you got money to burn you can use a RST-5000-48,2 of those to get 100V+ and then you can charge at 12kW...

With money to burn, can do much better than Mean Well

also, requires three phase ~240 AC input or 4-wire / Y 340~530VAC

IOW lots more than a grand to get the sparkie in, only useful stationary location