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calculating charging rate for 4S4P 18650 battery pack?

Tex

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Dec 16, 2019
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Ok,
This is giving me a headache!
As I have access to a supply of new 2600 mAh 18650 cells for free I have started getting into converting some of my old power tools etc.
One of the first projects I did was to convert a Bosch portable vacuum cleaner.
I put 4 cells of these 2600 mAh cells together (soldered) with with an RC alarm plugged into a balance lead, and a switch to isolate it when not being used, worked pretty good. I then bought a Accucell S60 hobby charger with balance port to charge it.

After that I acquired another lot of cells, so I also bought an Opus BT-C3100 cell tester/charger, a Sequre SQ-SW1 spot welder with foot pedal and some nickel strip, and several different flavors of BMS boards, so I was ready to rock and roll.

I then built a new 4S4P battery pack with a 20 amp BMS board, which just fitted in the little vacuum to double to battery size from the original 4.

I removed the switch and made a recessed charging port from an EC3 Dean plug, all installed and tested works a treat.
Soooo, here is my stupid question, my brains says 4S x 4P @ 2600 mAh per cell = 14.4 volts / 10.4 amps. (nominal), correct?
Secondly, the spec for these cells says Charging (CC) C rate 0.5C – 1.3A (per cell) – x 4 = 5.2 amps? or is it by 8?
And the Charging voltage spec says voltage: 4.2v max. (per cell) x 4 = 16.8v. or is it by 8?
That's my issue, I suspect it's by 4 for both specs.

Unfortunately it appears my Accucell S60 hobby charger won't charge anything without a balance plug, but I do have a Victron 10 amp charger for my 200 amp hour LiFePO4 battery which I thought might do the job but I suspect not.
I do have an HP 18 volt x 2.23 Amp power adapter, I think that might be the go?
I just can't seem to get it clear in my head, any help would be appreciated.

Cheers
Tex

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Ok, so it's 16.4V x 10.4 amps i think you are saying?
I just checked my Victron Smart Blue charger and it's actually 15 amps so way too big.
at 0.5C charging rate I guess I need something around 7 to 8 amps.
 
Gotcha, thanks for that.
Actually 4P = 1.3A (maximum) * 4 = 5.2A
So do you think the 18 volt x 2.23 Amp power adapter would make an ideal slow charger?
 

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BMS is shown in two pics.
Sorry, "function at lower voltage level"?
I've used that plug pack to charge a 200 amp LiFePO4 several times, I added a big heat sink way back when.
 

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BMS is shown in two pics.
Sorry, "function at lower voltage level"?

Constant voltage power supplies have operating ranges to varying degrees. This is akin to some 12V chargers being unable to charge 12V batteries if the battery voltage level is abnormally low.

I've used that plug pack to charge a 200 amp LiFePO4 several times, I added a big heat sink way back when.

If you've used it to charge @ ~12V before, should be fine.
 
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Can anyone identify these CJ brand 18650 cells or tell me what there capacity is from the label please?
Can't find anything in all my 18650 ID lists or online.
 

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They have to be kidding!
It's just one connection or the other, it's not long winded and it's only one question (in the second paragraph.
I just supplied plenty of info so to avoid any confusion.
As for telling me to ask a supplier, what a joke, I have spoken to several Victron suppliers over the years and the best they can do is tell you to watch a useless YouTube video, and even on this forum there is zero factory advice provided, sorry but their customer service sucks!
 
Curious. They clearly state their guidelines, but you proceed to do whatever suits you. More information isn't always better. Simple is better.

Victron has never been shy about their position on support. They support their VARs, not end users. As someone who frequents that forum regularly, I see your type of question ignored frequently. It's vague, has extraneous information, and you didn't even ask a question.

You included your van diagram, which is completely irrelevant as well as a picture of a solar panel and some odds and ends.

It's almost like you went out of your way to minimize the chances of an answer.

You probably think I'm being a dick, and you're entitled to that, but the community forum isn't anything like this one. You're asking the Victron community for support on a system with only a single Victron component. You're asking for design services for free.

I'll give you some feedback.

For the love of God, do not mount anything to the back of a solar panel. Panels get hot, and they rely on the back face to dissipate heat. You're proposing to put heat sensitive items on the back of a panel... inhibiting the panels ability to shed heat AND force the components to have more heat input. It's just a bad idea. You really want to heat your MPPT and battery to 120°F+ ??

As far as which one, that depends on you. Do you want to use the load port? Can your load port handle the loads? If the answers are yes and yes, then use the second option. I'm with Geraldo on the connection. if you're going to use the load ports, use both.
 
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