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diy solar

Will my RC battery charger work for top balance?

Yes, but it can only charge at 1A meaning you'll likely need 136 hours to fully charge the battery.

3.6 vs. 3.65 won't make any difference especially given how low the charge current is.
 
Thanks for the reply. Yeah the book is wrong there... its 6A or 50w max charge rate. So not as bad as 1A.
I'd definitely be getting something faster if it was 1A haha.
 
you have a Life setting on that charger--- use it!

put your pack together and charge with your 12v charger, then pull it apart and top charge each cell with your rc charger. I do it all the time. or you can put the pack in parallel and top charge all together.
 
you have a Life setting on that charger--- use it!

put your pack together and charge with your 12v charger, then pull it apart and top charge each cell with your rc charger. I do it all the time. or you can put the pack in parallel and top charge all together.

Agreed, much faster when charging as a 12V series pack. However, make sure you have a BMS and set it to 3.65V HVD. Since the cell's aren't in balance you have the risk of overcharging a single cell if you don't set a HVD.
 
Agreed, much faster when charging as a 12V series pack. However, make sure you have a BMS and set it to 3.65V HVD. Since the cell's aren't in balance you have the risk of overcharging a single cell if you don't set a HVD.

No risk. It's an actual balance charger. It monitors the cells, modulates the charge current accordingly and balances among cells. It will not permit any cell to go over 3.6V. No BMS needed. These are used 1000s of times per day to charge firey-explodey RC packs with no BMS.
 
yes assuming i make a set of balance leads so i can charge/balance it as a 4s pack I could charge them a bit faster which i still may do. But as of now I'm only going to charge as a 1s4p at 6a max.
 
What's the max Ah cell your charger will accommodate? My RC charger is limited to a 100Ah cell, so I just assumed that it couldn't be used with a 280Ah cell. Don't have the cells yet to try it, but it would be nice if I could use it for balancing.
 
Lol... This is me RIGHT NOW! Lol... I also have a 6amp LiPo/LiFe RC charger... and I'm top balancing 4 ea 280 amp hour cells. Sheesh... this takes FOREVER.... Lol... I started with the little guy, then reconfigured it for 12 volt and got my 15 amp battery charger on it. Still moved slow, so I borrowed a neighbors charger too...both set for AGM. Around 25 amps in theory. I got up early and got it charging again... The variance later this morning was .09 with the high cell at 3.65 on the multimeter and 3.72 on the Overkill BMS as a monitor. Now I have them in parallel and on the RC charger again, set for LiPo which is 4.2 volts. Why the discrepancy?
I have been bypassing the BMS and charging directly on the battery, while watching closely with a good multimeter. When in series I've been using the BMS to monitor cell voltage. Weird thing is there is a big variance between the BMS and the multimeter... I can't figure out why?
Dang thing is that the RC charger keeps cutting out. Since resetting this am on parallel, the cells have only hit 3.44 volts. I have a bench top CC CV 10 amp being delivered today, but I'll keep on the hobby charger until then. Heat gun at the ready to capacity test with dual overkill BMS in Parallel as an experiment!
 

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What's the max Ah cell your charger will accommodate? My RC charger is limited to a 100Ah cell, so I just assumed that it couldn't be used with a 280Ah cell. Don't have the cells yet to try it, but it would be nice if I could use it for balancing.
The RC one I'm using has a capacity limit of 8000 m Amp hrs. It can be turned off I think. Probably why mine keeps shutting off. The one I have is a SkyRC B6 mini...
 
, set for LiPo which is 4.2 volts. Why the discrepancy?

4.2V?
Thats fine for a 3.7V Li-ion, but not for LFP.

did you test the multimeter with different leads? Some meters have pretty bad cables delivered with the meter, so sometimes its better to dump them and replace with proper ones.

Another issue: Most meters don't have a 4V setting, generally it's 2V and the next selectable range is 20V. The accuracy on a lot of meters is the best at the near-range-end, so 18V on a 20V setting is much more accurate than 3.6V on a 20V setting. This mainly applies to analog meters, not so much on digital ones, but it still makes a (small) difference.

Digital multimeters generally take measurements with accuracy superior to their analog counterparts. Standard portable digital multimeters are specified to have an accuracy of typically ±0.5% on the DC voltage ranges.

Accuracy figures need to be interpreted with care. Digital meters usually specify accuracy as a percentage of reading plus a percentage of full-scale value, sometimes expressed in counts rather than percentage terms
Source: https://en.wikipedia.org/wiki/Multimeter

3.6V at 0.5% is still 20mV difference.. so anywhere between and 3.582 and 3.618 is considered fine. You need to check the actual accuracy of your meter.
For the OverkillSolar BMS, I don't know what its accuracy is. but with these low voltages, proper wiring for the balance leads do also matter
 
yes assuming i make a set of balance leads so i can charge/balance it as a 4s pack I could charge them a bit faster which i still may do. But as of now I'm only going to charge as a 1s4p at 6a max.

For the love of all that is holy, make balance leads and cut your very lengthy charge time to 25%.
 
I don't think there is a max Ah. I know I can set a safety cutoff for ah into the battery. I will be testing it soon.

SoundinSpirit, "Now I have them in parallel and on the RC charger again, set for LiPo which is 4.2 volts. Why the discrepancy?"

From what i understand is if you use the lipo setting its going to use that 4.2v as the max per cell... so over the 3.65 max for lifepo4 cells.
If your charger has a life setting id use it.

Snoobler, hahaha, yeah I agree and am working on it now :)
 
For the love of all that is holy, make balance leads and cut your very lengthy charge time to 25%.
Sorry to bomb you on a bunch of different threads! Lol.... Would you clarify the balance leads thing? I'm not sure I follow... Thanks!
 
Sorry to bomb you on a bunch of different threads! Lol.... Would you clarify the balance leads thing? I'm not sure I follow... Thanks!
Balance leads are the multi wire connector (5 wires for 4s) that lets the bms or charger in this case read the voltage each cell in the pack.
 
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Sorry to bomb you on a bunch of different threads! Lol.... Would you clarify the balance leads thing? I'm not sure I follow... Thanks!
Its the wire that is going into your 5 in 1 cell meter. Your rc charger should let you hook that plug plus the main pos and neg into the charger. Then you can use the balance charge function on the charger and it will monitor and regulate the amount of volts in each cell to keep the pack balanced.
 
Its the wire that is going into your 5 in 1 cell meter. Your rc charger should let you hook that plug plus the main pos and neg into the charger. Then you can use the balance charge function on the charger and it will monitor and regulate the amount of volts in each cell to keep the pack balanced.
That's what I thought... I was just wondering if there was something I was overlooking! Cutting charge time down on 280 amp hour batteries.... I'll take any gimmick I can dream up! Lol...
 
That's what I thought... I was just wondering if there was something I was overlooking! Cutting charge time down on 280 amp hour batteries.... I'll take any gimmick I can dream up! Lol...

Not a gimmick. It's a specialized Lithium charger that has a main connection at the terminals and a set of balance leads that's attached to each cell, so the charger sees pack voltage and individual cell voltages. In balance charging mode, it provide max current until ONE cell hits peak, then it begins to throttle current to hold it there and begins passing slightly more current to the other cells. In the end, all cells will be at the peak voltage at charge termination.
 
Well its working so far. Time counter only goes to 999 and then resets it and the mah reading but other then that its all good. I have the parts for a better balance cable on the way also.
 

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Well its working so far. Time counter only goes to 999 and then resets it and the mah reading but other then that its all good. I have the parts for a better balance cable on the way also.
Did you make studs for each cell terminals? That's way better than the ones that came with my cells! I'm afraid they could strip out...
 
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