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Jan 19, 2019, 07:33 PM
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Need help with wiring for charging multiple 1S batteries


Hey, I'm building a board for charging 18650 batteries, and I want to use ISDT Q6+ that I already own for it. I printed a tray and I have a spare 6S balance lead I can use, but I'm not sure about the wiring.

First of all, do I need to plug the main lead somewhere (XT60) or can I charge using just the balance lead?

The batteries I have are 3400mAh. If I understand correctly wiring them in series would require charging as 4S 3400mAh and I would have to always have 4 batteries in charger to close the circuit. However I'd like to be able to charge any number of batteries at once (1-4 for now) and not be locked to 4 always). For this I think the correct charger settings are charging as 1S and the capacity (output A) setting to multiple of 3400 (correct?) . How do I wire this up?



I checked with a multimeter on a lipo parallel charging board and the connections seem to go like this:



So I think to get what I need I would wire like this:

NEG ___ 1- ___ 2- ___ 3- ___ 4- all bridged
1 ___ 1+
2 ___ 2+
3 ___ 3+
4 ___ 4+

Is this correct?
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Jan 19, 2019, 09:24 PM
That's what I wanted it to do
MrEFlyer's Avatar
Connect all of the + together and connect all of the - together. If you put one battery in then set the charger for 3.4 Amp. If you put two batteries in the holder set the charger to 6.8 Amps and so on. Add 3.4 Amps for ech additional battery.
Charge as if it is a single battery with incremental 3.6 Amp capacities.
Jan 19, 2019, 10:28 PM
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SilverSport's Avatar
I was looking to be able to charge 2 to 4 at one time myself, then I came across these two on HK and decided a dedicated charger was better. Mine are just 18650's for flashlights and a few electronics I use 14500's in . When I got them I think they were each $10.

https://hobbyking.com/en_us/item-vc4.html
https://hobbyking.com/en_us/25w-5a-usb-charger-1.html - to power the charger with at least 2.1A
Jan 19, 2019, 10:48 PM
If it flies, I can crash it.
rocketsled666's Avatar
You are making it unnecessarily difficult. MrEFlyer has it right. You can charge all those cells in parallel. The charger will always think it's charging a 1S. Whatever charge current you would be using for 1 cell, multiply that by as many cells as you have in parallel and charge them all in parallel. You can use the charging case you made, just tie all the "+" together, and then tie all the "-" together, and then hook up to the charger like it's a 1S cell.

You only have to do what you're doing if the charger won't do 1S.
Jan 20, 2019, 04:55 AM
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Quote:
Originally Posted by MrEFlyer View Post
Connect all of the + together and connect all of the - together. If you put one battery in then set the charger for 3.4 Amp. If you put two batteries in the holder set the charger to 6.8 Amps and so on. Add 3.4 Amps for ech additional battery.
Charge as if it is a single battery with incremental 3.6 Amp capacities.
So I would only connect the main lead then and not balance? Are Li-Ion batteries charged at 1C just like Li-Po? Some sources state 0.5C as the recommended value
Jan 20, 2019, 09:05 AM
Registered User
I don't think the Q6+ will work properly without a balance lead hooked up as well as the power lead. It needs that to read the cell voltage correctly during charging. I have never tried 1S on mine but it should work if you hook up to both the power and first two balance leads. I would do your 1S charging in parallel - just make sure that your batteries are all near the same voltage when you hook them up.
Jan 20, 2019, 10:02 AM
Registered User
The recommended charge current is around 0,3 0,4C or less.
It is also not a mistake to connect the balancer cable on 1s parallel charging additionally to the batteries. This can save a little charging time.
Jan 20, 2019, 04:12 PM
If it flies, I can crash it.
rocketsled666's Avatar
If the Q6 designers took even a moment to think about it, 1S would be the only case where the balance taps aren't required. This is how my PL8 works. It knows for a 1S there's no point.

It shouldn't make a difference to charging time, C rate is C rate regardless of whether it's being applied via the primary leads or the balance taps. If your 1S charges faster with both primary and balance taps connected, the charger is violating the charge current setting you set. It's either not delivering the programmed current with just one set of connectors attached, or it's delivering too much current with both set attached.
Jan 20, 2019, 04:18 PM
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Thread OP
Without the balance cable the voltage reading was wrong, read 4.5V on 3.68 actual voltage. After I connected both it worked fine. Charged 2 batteries at 0.5C (3.4A out) so it seems to be working all right.

Thanks everyone for your help.
Jan 20, 2019, 04:40 PM
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Quote:
Originally Posted by rocketsled666 View Post
....It shouldn't make a difference to charging time, C rate is C rate regardless of whether it's being applied via the primary leads or the balance taps. If your 1S charges faster with both primary and balance taps connected, the charger is violating the charge current setting you set. It's either not delivering the programmed current with just one set of connectors attached, or it's delivering too much current with both set attached.
No, the charging current is the same. But the balancer connection compensates for the voltage drop on the charging cable, causing the charger to enter the CV phase sooner than necessary.

https://www.rcgroups.com/forums/show...6#post28819489
Jan 20, 2019, 05:45 PM
That's what I wanted it to do
MrEFlyer's Avatar
ISDT is one of the best chargers sold today. It can charge 1S batteries in a snap. Just connect your batteries in parallel, set the charger to 1S at the current required for the batter(y) (ies) connected and charge (it) (them).
Jan 20, 2019, 07:48 PM
If it flies, I can crash it.
rocketsled666's Avatar
Quote:
Originally Posted by RNFLY View Post
No, the charging current is the same. But the balancer connection compensates for the voltage drop on the charging cable, causing the charger to enter the CV phase sooner than necessary.
I agree this can make a difference when the resistive losses in the primary charging cable are high. At a few Amps I don't think it can add up to enough to matter. But north of 10A it can start to matter a little, I guess... it would depend on how the charger was implemented.

How much time is saved on the charge if CC terminates a few 10s of mV below 4.2V? I bet it'd be pretty hard to measure. The cell is going to continue to draw the same current for a while after the switch to CV anyway. So effectively, it's still getting the CC rate. The charge cuts off when the current being drawn by the cell drops to some low level, C/10 or C/20, and any voltage drop is going to be pretty low by then.
Jan 21, 2019, 06:58 AM
Registered User
Basically, it can make a noticeable difference in the charging time when parallel charging of several cells, because the current is correspondingly higher than in single or serial circuit. On the other hand, LiIo batteries should be charged with less than 0.5C, so that the total charging current keeps within manageable limits.
How big the difference is, I never have tested. I also think that it does not matter much. I wrote: "This can save a little charging time. "
Last edited by RNFLY; Jan 21, 2019 at 07:05 AM.


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