help needed: bulk charge 18650 5s5p pack?

[tuurb]

Hello,

I'm working on a project and I am going to use a 5s5p 18650 pack. Probably the samsung 25R cells...

I read that I need to charge them constant current, and then constant voltage with a cutoff at 100mA. So could I use simply a cc/cv led driver psu??

I thought to use a meanwell HLG series power supply, the HLG-240H-20 can be adjusted from 18,6-21,4V and 6-12A.
http://www.meanwell.com/search/hlg-240h/default.htm

So I would adjust it to 21V and then work with some kind of timer to avoid overcharging the batteries.
Or I should invent something to monitor the chargingcurrent and to cut off at 500mA (5*100mA)?

Now, am I forgetting something?
Is a more complicated charger needed?
Do these cells need balancing? (I would like to keep them constantly in parallel)
Anybody an idea for the 500mA cutoff system?

Thanks in advance!

 

[tuurb]

Nobody with answers to my questions?

I found that lots of people already use this meanwell psu's:
http://endless-sphere.com/forums/viewtopic.php?f=14&t=42169&p=616665&hilit=meanwell+charger+ip67#p616665

Also there's this current limiter board of Fechter. very nice thing but if I understand it correctly it cannot be used to cut off the charging when the batteries are full (100mA cutoff for most 18650 cells...
http://endless-sphere.com/forums/viewtopic.php?f=31&t=36958

Also found this site to order meanwell power supplies. Seems to be quite cheap. Not sure what they charge for shipping though...
https://www.meanwell-web.com/en/products/ac-dc-power-supply/led-driver/gt-185-w-led-driver/hlg-240h

 

[Matt Gruber]

i sometimes charge my 5s2p makita pack(s) with an old school transformer, 16.5v 2 amp.
i don't see what the fuss is about. i use a timer and can predict the time to about 1 minute

 

[999zip999]

I like an extra set of sense wires and a RC cell monitor and or cell balancer style ?

 

[tuurb]

Hi,

Thanks for the replies

@matt:
How do you predict the time and kind of timer do you use?

@999zip999:
no BMS because I wanted to keep it simple. I will however make balance leads so that I can add a BMS and balance the cells if needed.
But I read that the recent 18650 cells do not need to be balanced??
I'm really curious or this is true because I tend to keep my 5s5p constantly in parallel and I would not like the cells to discharge eachother...

regards,

Tuurb

 

[Matt Gruber]

i make a charge map.
write down charge time for each .1 volt
here is a sample of 5s4p
19.2v.........6 minutes
19.3..........12
19.4........ 8
19.5.......5
19.6.....3
19.7.....8
19.8 ..16 minutes
and so on.........
then for the next charge, i look for the start voltage, add up the time to whatever v i want, and set the timer.

 

[tuurb]

nice, that is a quite simple way.

I think I'm going to start searching for a small and easy programmable time-switch.

 

[dnmun]

why? it is really unfair for you to be so severely mislead but we cannot stop it.

how will you keep the cells in your 5S pack from overcharging? how does the pack get balanced? why did you decide on 5S5P?

 

[teslanv]

You would be much better off getting an RC Balance charger.

Something like this would suffice:

http://www.hobbyking.com/hobbyking/...AC_Charger_Discharger_1_6_Cells_GENUINE_.html

There are of course many other options, and the charger referenced above would be quite slow, but the point is that an RC charger is the proper tool to use for charging and balancing Lithium cells, if you do not have a BMS on the battery.

 

[tuurb]

Hi,

So you mean that timing is not such a good idea?
I understand that timing is not as exact as measuring current but because I do not have experience with these batteries I do not know or mich be that bad...this is why I started this thread of course...

I decided to use 5 batteries is series because of the max speed of +-35km/h that I want to achieve with my e-scooter. Then in the chassis I could hide max. 5 paralleled 5s batteries.

For balancing I wanted to buy some sort of charger of hobbyking... But because I wanted a smaller and simpler charger (without adjustable settings and without seprate psu) I started to look at the meanwell psu's.

greets,

Tuurb

 

[tuurb]

Hi teslanv,

Guess we were typing a reply at the same time.
I know a RC charger would better and easy. But then I would have to carry around 2 separate things because there is almost allways a seperate psu needed. Also the total volume of the charger would be much bigger for the same power.

The charger you propose is only 50W and only (roughly) 2 times smaller than the 240W meanwell cc/cv psu.

It would take a lot more time to charge the 5S5P pack...

regards, Tuurb

 

[999zip999]

I like an extra set of sense wires and a RC cell monitor and or cell balancer style ?[/quote]

 

[999zip999]

Funky phone

 

[999zip999]

Deleted first part.

 

[teslanv]

Hi teslanv,

Guess we were typing a reply at the same time.
I know a RC charger would better and easy. But then I would have to carry around 2 separate things because there is almost allways a seperate psu needed. Also the total volume of the charger would be much bigger for the same power.

The charger you propose is only 50W and only (roughly) 2 times smaller than the 240W meanwell cc/cv psu.

It would take a lot more time to charge the 5S5P pack...

regards, Tuurb

What you are talking about is "bulk charging" with a Meanwell. And yes, the charger I referenced is only 50W so it would take a long time to charge.

It really depends on WHERE you intend to charge and how long you can wait to charge. If you want to charge your batteries really fast and will be watching them the whole time (i.e. at a truck stop on a long bike trip) then a meanwell PS might be a good solution. If, however, you are charging at home in your garage and cannot watch the batteries to know when to stop, a lower powered RC charger (or a high-powered charger & Separate power supply) can work well. - an RC charger can also BALANCE the cells, where the meanwell bulk-charging method will not. Over time this can become a problem, as some cells will over/under charge disproportionately, and damage the cells.

I have both options, and find both useful.

 

[Matt Gruber]

i only use 18650's that are known to stay in balance. and i check them now and then, individually of course.
not the cheap stuff many hobby guys use.
not that i spend a lot; i'd rather have used quality cells that new questionable stuff.

 

[tuurb]

I agree that lipo's need to be balanced, teslanv.
I have experience with normal flat lipo packs and have seen that this cells tend to drift. For charging these I use an RC charger with a separate psu

But I read that somewhere that NMC chemistry 18650 cells do not drift and do not need to be balanced.
I was hoping people here had experience with the samsung 25R cells and can confirm this.
What kind of cells do you use Matt Gruber?

Also if I use the 240W meanwell psu for a 5s5p pack I would be charging at a max current of 2,4A, well below the specified max charge current of 4A, so I assume this would remain safe. But again, I'm really curious for experiences of 18650 cell owners!

If I eventually made the pack I would surely foresee balance leads, but I really hope that with these 18650 I would only need to balance the pack every 10-20 charges... Also if the cells do not tend to drift I would think I can constantly keep them in parallel ! ?
How often do you balance your cells Matt Gruber? More often than every 10-20 charges?

thanks!

 

[Matt Gruber]

i spent many hours reading old posts. look for Doctorbass and Makita Konions, and Doc's happy customers. one guy got i think 1500 charges without balancing! he even over discharged them, a really bad thing, and they came back after a few shallow cycles without individual balancing.
and look into BOSCH tool packs. they come from Bosch without any rube goldberg balance crap. The good stuff doesn't drift much if at all.