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Parallel Charging Lipo Batteries - Is it Safe ?

Old 04-15-2022, 11:09 PM
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Default Parallel Charging Lipo Batteries - Is it Safe ?

I have the parallel charging board shown, so far unused. It's use would make charging multiple batteries much more convenient ( time-wise ). But I seem to recall a web-site that declared it was unsafe to parallel charge Lipos under any circumstances.

Is there actually any significant risk in doing this and do many people out there routinely do this without issues ? Maybe it's "standard operating procedure" but as I am not a club member, I just don't know.


Old 04-17-2022, 04:16 AM
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There is not just one web site that tells you this is dangerous, there are many. You are much better off getting a charger that can charge multiple batteries at the same time.

If you do it, however, take a video of the fire and post it in RC Humor.
Old 04-17-2022, 07:39 AM
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Really, I Use them all the time,, perfectly safe if you know what you're doing,

My first set up worked so well, I bought second one so I can charge multiple packs with different cell counts at the same time



Old 04-17-2022, 08:01 PM
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Assuming parallel charging is only to be done with batteries of the same voltage, I guess one of the potential dangers is hooking together batteries of widely different discharge levels/voltages. Because that would cause an immediate current flow towards the lower charged battery/ies hence the need for fuse protection. But if all batteries were ( about ) equally discharged, I can't see the problem.

I know flight times might vary and throttle use times, leading to different discharge levels in used batteries, but that is an awareness thing by the operator. For example, if a flight is cut short for some reason, you would single out that pack for different treatment.

I would think checking each battery's final voltages ( after discharge ), including looking at individual cell voltages, would be sufficient before connecting them up for parallel charging. Some judgement on what is close enough would be needed. Also I would check voltages on each battery after charging.

scale only 4 me : Is this what you do ? Also what does that red and black board sitting on top of your power supply do in the first photo ? ( the blue board has cell balance sockets so not sure about the red and black board ).

rgburrill :What am I missing ? Do you have specific reasons for calling this dangerous ? What about if I do what I mention above ? My charger has two outputs and the most I have seen is four, so for folks with many batteries to charge, that seems a very expensive way to charge.
Old 04-18-2022, 03:37 AM
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Originally Posted by Tphage
Assuming parallel charging is only to be done with batteries of the same voltage, I guess one of the potential dangers is hooking together batteries of widely different discharge levels/voltages. Because that would cause an immediate current flow towards the lower charged battery/ies hence the need for fuse protection. But if all batteries were ( about ) equally discharged, I can't see the problem.

I know flight times might vary and throttle use times, leading to different discharge levels in used batteries, but that is an awareness thing by the operator. For example, if a flight is cut short for some reason, you would single out that pack for different treatment.

I would think checking each battery's final voltages ( after discharge ), including looking at individual cell voltages, would be sufficient before connecting them up for parallel charging. Some judgement on what is close enough would be needed. Also I would check voltages on each battery after charging.

scale only 4 me : Is this what you do ? Also what does that red and black board sitting on top of your power supply do in the first photo ? ( the blue board has cell balance sockets so not sure about the red and black board ).

rgburrill :What am I missing ? Do you have specific reasons for calling this dangerous ? What about if I do what I mention above ? My charger has two outputs and the most I have seen is four, so for folks with many batteries to charge, that seems a very expensive way to charge.
You answered your own question in bold. Look it up, it can cause fires and eruptions.

For the latter part, If the connectors are simply connected in parallel there is no way to determine if one battery is being overcharged, thereby becoming dangerous. And that surge you mention would likely come as soon as you plugged in the second battery, even with the charger off. Surely you have jump started a car with a dead battery and observed the spark. OTOH, if you have circuitry on those little boards that determine charge rate and voltage conditions of each battery, that would be just the same as having a charger with many outputs. And then they are not really in parallel.

As far as those folks who have "many batteries to charge", I am reminded of a comment from George Burns about a woman with many, many kids: "I love my cigar but I let it rest once in a while." Let others have a turn, too.

Last edited by rgburrill; 04-18-2022 at 03:47 AM.
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Tphage (04-18-2022)
Old 04-18-2022, 04:36 AM
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Originally Posted by Tphage
Assuming parallel charging is only to be done with batteries of the same voltage, ,,,,,,,,,,,,,,,,,,,,

scale only 4 me : Is this what you do ? Also what does that red and black board sitting on top of your power supply do in the first photo ? ( the blue board has cell balance sockets so not sure about the red and black board ).
.
Yes, they must of course be the same cell count and same Mah to realistically be charged safely, I routinely charge 4-4s-5000mah packs at a 20 amp rate, and when I was racing cars/trucks I used the second one to charge 2or 3 2s-5000mah packs, I never charge at more than 1c, so I have never had a problem

That is a Cellpro Multi-4 charger and adaptor board,, I use for my A-123 RX packs as a field charger, that only charges one pack at a time

Last edited by scale only 4 me; 04-18-2022 at 04:38 AM.
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Old 04-18-2022, 03:02 PM
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Food for thought.

At my beginner-to-R.C. level ( although not entirely to the field of electrical knowledge ), I may take George's advice.

I have two more B6 chargers I can dig out, albeit at having to find the bench space to fit everything, so I can do 4 batteries at a time.

scale-only-4-me : Your set-up is most impressive and you obviously know you are doing. You are way ahead of me.

Thank you very much guys for your valuable inputs.
Old 04-18-2022, 04:27 PM
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I started out with a Hitec x4 4 circuit charger to do multiple packs,, but at 50watts per channel, it just didn't have the output to charge the larger packs I started using in a reasonable time frame,, just make sure what ever you get has the horsepower for the battery size you're using

good luck
Old 04-23-2022, 10:17 AM
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The nice thing about the Internet, you can always find "a guy" or someone who says "... I remember a web site, but I can't find it any more" that tells you that if you push "this" button, the world will end.

"I found a guy" (actually, several) that says there is no problem charging LiPo batteries in parallel.

Complete Guide to LiPo Batteries and Failure Reports - Part II.
Parallel charging packs

https://www.rcgroups.com/forums/show...light=parallel
https://www.rcgroups.com/forums/show...light=Parallel
https://www.rcgroups.com/forums/show...light=Parallel
https://www.rcgroups.com/forums/show...postcount=8din
Old 05-02-2022, 11:41 PM
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Originally Posted by Tphage
I have the parallel charging board shown, so far unused. It's use would make charging multiple batteries much more convenient ( time-wise ). But I seem to recall a web-site that declared it was unsafe to parallel charge Lipos under any circumstances.

Is there actually any significant risk in doing this and do many people out there routinely do this without issues ? Maybe it's "standard operating procedure" but as I am not a club member, I just don't know.
I personally would never do so, especially with those piddly boards as shown in pic. I'm lot better of with multi chargers.

This is much safer way!

Ready for flying action.


I personally would never do so, especially with those piddly boards as shown in pic. I'm lot better of with multi chargers.
Old 05-03-2022, 04:17 AM
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Originally Posted by Joseph Frost
I personally would never do so, especially with those piddly boards as shown in pic. I'm lot better of with multi chargers.
I've been using those piddly boards for years,,

I see only one of your chargers puts out 100 watts per channel, the other two only 50 like the Hitec I had,, 'My Icharger 306b can put out up to 1000watts (500 on 12v),,, how exactly are you better off?

And why are you charging without the balance tabs hooked up??? That's for sure something I'd never do
Old 05-03-2022, 04:02 PM
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We all do things different way, it's only natural, I have only expressed my way of doing it and would never recommend charging packs in PAR. LOL- Love it or Loath it!
I prefer doing it the safer way with my lipo fleet.


Always charging outdoors.

Metal cabinet Outdoor lipo storage.

My new solar outdoor mini charging station, AC/DC output.
Old 05-05-2022, 08:27 AM
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Originally Posted by Joseph Frost
We all do things different way, it's only natural, I have only expressed my way of doing it and would never recommend charging packs in PAR. LOL- Love it or Loath it!
I prefer doing it the safer way with my lipo fleet.


Always charging outdoors.

Metal cabinet Outdoor lipo storage.

My new solar outdoor mini charging station, AC/DC output.
Those pictures showing all your batteries and chargers answer none of my questions

If your way of doing it is charging lipos without a Balance function enabled,, that is straight dangerous, that's exactly why we had so many fires in the early days of lipos
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Old 05-09-2022, 09:25 AM
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I charge 4 at a time as long as same cell count. My 2s for my rc car, and my 2s for my rc plane rx and gear. The voard cuts the batteries off automatically at 8.4v balanced.

Haven't had an issue yet..just don't leave it unattended and use charging bags.

I just leve em in the bags and set em on the work bench. It might bite me some day, but, I have a routine with batteries. Once a month, they get fully charged, load tested, discharged to minimum voltage, then charged to storage if I'm not going to use em. Load test has probably saved at least two planes over the years..cells failed during load test thst would have failed in flight, causing either LOS or a dead stick situation.
I'm a bit OCD (Ok, a lot OCD) so I also keep logs of pre and post flight or run on em..When I start to see it "drop off" as in not retaining levels for similar run times, of course check out what it goes to, but if all the other stuff checks out, battery gets replaced. Even if its still "good" it gets replaced every two seasons. I don't hang on to oldies, otherwise I'd be swamped in NiCads

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Old 08-26-2023, 01:56 PM
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double

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Old 08-26-2023, 01:58 PM
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Originally Posted by Joseph Frost
We all do things different way, it's only natural, I have only expressed my way of doing it and would never recommend charging packs in PAR. LOL- Love it or Loath it!
I prefer doing it the safer way with my lipo fleet.


Always charging outdoors.

Metal cabinet Outdoor lipo storage.

My new solar outdoor mini charging station, AC/DC output.
Why is your way safer, both have dangers but both dangers are easily mitigated.
Old 09-02-2023, 10:19 PM
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I use (4) of the wimpy Imax B6 chargers. I am in no hurry charging my larger batteries. I also use a multi charge board to charge my 3s 550, 350mah lipo's. As the batteries don't give the quad a long flight time, I can run through my 12 pack pretty fast. So I use (2) boards in (2) chargers to charge (8) batteries. I guess it was 2019 when I first started using the boards. So far no issues, but I am not trying to charge at 10c, 20c either.

Lets face it, a water bottle can be dangerous in some peoples hands. There are all sorts of web site that say every thing is dangerous. I remember one company put out an add for their charging bags. To show how dangerous lipos are, they stuck a nail through a lipo.

Buzz.
Old 11-30-2023, 09:54 AM
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It's a bad idea. Use a multiple output charger instead. It's best to balance charge, where each cell in a pack is voltage-matched to the other cells, and this is not possible if they are in parallel.
Old 12-01-2023, 10:06 PM
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Ever charged a high capacity battery, chances are that pack is built in parallel, so how is charging batteries in parallel dangerous. It is very little benefit using low power charger.
It is dangerous if you plug a battery with 90% charge with one that is in a lower charge state. That’s a lot of amps being pushed into the other.

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