Batteries in series and multiple chargers?

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Iccarus
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Batteries in series and multiple chargers?

I would like to know if anyone can tell me how to use multiple chargers on 28 cells in series. I noticed that on the 3500li pack negative there are three wires connected at the terminal. What I want to do is take the wire that goes to the controller and connect it to the 28th cell. Take the charging wire and hook it to the 24th cell right?(I'm using a 24cell charger) and then use a 4cell charger to charge the other 4cells. As long as I do this right I can leave all the batteries in series correct?

garygid
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Re: Batteries in series and multiple chargers?

Yes

Cheers, Gary
XM-5000Li, wired for cell voltage measuring and logging.

Iccarus
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Re: Batteries in series and multiple chargers?

Thanks. I went through alot of trouble with ioslator switches that I didn't need I guess... if I only had a brain, da da - da da da da da.

PS Is a 20amp charge to much for a 40AH cell. I was thinking of using two of those 10amp 4cell smart chargers together to keep up with the TSL72-15. It's either that or another three amp smart charger, I can't find a 5amp lifepo4 charger. I just don't want to be waiting for the 4pack to finish charging after the TSL is done.

2008 XM3500li Mods/Kelly KBL12251/84v 28cell 40AH pack/ Variable regen brake trigger on left brake handle/Givi/Cycle Analyst/Homemade BMS

KMX Typhoon Home build (recumbent pedelec) with two Astro Brushless 3220motors/twin castle Phoenix ICEHV 160/ Cycl

garygid
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Re: Batteries in series and multiple chargers?

Use 2 chargers in series only if at least one has an "isolated" output.

Two in parallel might work (or not), but that depends upon the charger design details. The safer path is assume not, but ... be careful.

Charging at 0.5C (20 amps into a 40 Ah cell) is usually OK, but varies by battery type, make, and model.

Cheers, Gary
XM-5000Li, wired for cell voltage measuring and logging.

Iccarus
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Re: Batteries in series and multiple chargers?

I thought of charging parallel but figured the lower voltage charger would never turn on, because the voltage would be to high. This way should work I think because the chargers will only read the voltage between thier poles. I still don't understand about isolated output but with all the bells and whistles these smart chargers come with they probably both have them.

2008 XM3500li Mods/Kelly KBL12251/84v 28cell 40AH pack/ Variable regen brake trigger on left brake handle/Givi/Cycle Analyst/Homemade BMS

KMX Typhoon Home build (recumbent pedelec) with two Astro Brushless 3220motors/twin castle Phoenix ICEHV 160/ Cycl

Iccarus
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Re: Batteries in series and multiple chargers?

Bill 016.jpgBill 012.jpgBill 015.jpgBill 007.jpgHere is a picture of how the 8 extra cells fit in the 3500li. It looks a little sloppy right now but I'm setting it up so I can leave everything under the seat and have just one plug to plug in. I also had a little fun customizing with two 15" blue led strips (it looks pretty cool at night and makes you more visable) and side lights and extra skull brake light,all LED. Also a picture of one of four balance cards that I use to read voltages and balance with till I start using the Goodrum/Fechter. When it gets hot I'll see what this thing can take. More Temp readings to come.

Bill-

2008 XM3500li Mods/Kelly KBL12251/84v 28cell 40AH pack/ Variable regen brake trigger on left brake handle/Givi/Cycle Analyst/Homemade BMS

KMX Typhoon Home build (recumbent pedelec) with two Astro Brushless 3220motors/twin castle Phoenix ICEHV 160/ Cycl

sixpax2k9
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Re: Batteries in series and multiple chargers?

on a similar note.... Would this concept be the same for SLA batteries?
I mean for 72V system, could I leave them always connected in series, and just have 2 charging connectors, 1 48V wired to the - of bat#1 and + of bat#4, then a 24V charging plug connected to the - of bat#5 and + of bat#6. Is that doable or does the connection between batteries 4 and 5 need to be severed while charging????

Dave

Dave ; Tennessee
XB-600.

garygid
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Re: Batteries in series and multiple chargers?

Same rules for SLA, no need to switch out IF the charger has an isolated output.
No, "smart" charger does NOT mean isolated.
If you do not understand "isolation", then best to use switches to isolate the battery sub-packs for charging.

Or, get help to check for charger-output isolation. If the chargers are ON and not connected to anything, and you can measure a very high RESISTANCE between the minus (-) output of one charger and the minus of the other, then (most likely) one (or both) had an isolated output.

The "isolated output" is usually more expensive, so it is usually listed in the product specifications, something like "X to Y volts DC, isolated".

Cheers, Gary
XM-5000Li, wired for cell voltage measuring and logging.

Iccarus
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Re: Batteries in series and multiple chargers?

Dave, I don't mean to keep repeating but... remember if you add cells the low voltage cuttoff for your controller will be to low. Devide the LVC (52.5v for a 3500) by the number of cells and that gives you the individual cell LVC. So you will become responsible for not drawing the pack to low. I can't overstate this. Just don't want to see anyone kill their pack. I didn't realize this when I started and drew my pack a little low a few times. Lucky it didn't seem to effect anything so far.

Bill-
28cell 3500li

2008 XM3500li Mods/Kelly KBL12251/84v 28cell 40AH pack/ Variable regen brake trigger on left brake handle/Givi/Cycle Analyst/Homemade BMS

KMX Typhoon Home build (recumbent pedelec) with two Astro Brushless 3220motors/twin castle Phoenix ICEHV 160/ Cycl

sixpax2k9
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Re: Batteries in series and multiple chargers?

Appreciate the concern, I am not using Lithium batteries... using good ol SLA batteries at the moment.
When the current SLA batteries die I will more than likely switch to LIFe.

Dave ; Tennessee
XB-600.

yount3000
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Re: Batteries in series and multiple chargers?

Like the daring approach here. Would love to see a move detailed description here as to what you did to achieve this.

yount

Iccarus
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Re: Batteries in series and multiple chargers?

It's a little complicated, and frankly probably not worth the hassle. It's probably better to just settle for 24 cells unless you can find a suitable portable charger for charging 28 cells. I just did it because I had the stuff I needed and to much spare time.

Bill

2008 XM3500li Mods/Kelly KBL12251/84v 28cell 40AH pack/ Variable regen brake trigger on left brake handle/Givi/Cycle Analyst/Homemade BMS

KMX Typhoon Home build (recumbent pedelec) with two Astro Brushless 3220motors/twin castle Phoenix ICEHV 160/ Cycl

marylandbob
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Re: Batteries in series and multiple chargers?

The best solution is to raise the charger output by 14 volts, to change it from a 24 cell charger to a 28 cell charger. Otherwise, if the charger outputs are isolated and floating with respect to each other and powerline ground, You could connect the 24 cell charger positive lead to the main positive battery terminal, and connect this 24 cell chargers negative lead to ground at the 24 cell point, 4 cells before main ground.-The 4 cell chargers positive lead would connect to this same point, with the negative lead from the 24 cell charger, and negative of the 4 cell charger would connect to the main ground/negative terminal at the end of the battery.-For safety, install fuses in each chargers leads, fuses should be rated slightly higher than maximum charging current.---Bob

Robert M. Curry

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