Batteries Parallel Charging

[sneezy007]

Hey guys,

I was looking through my 4S lipo batteries today for my quad. I noticed one battery is down to 9 volts and it says 0% fuel left in the battery.

These batteries came with a used quad I bought. Can I parallel charge this battery with the other ones? The rest are good with 20% to 30% fuel remaining and they're around 11 volts.

Thanks,
Dino

 

[Smoggie]

No, you cant parallel charge that battery. It sounds like it has a bad cell or all the cells are severely over discharged. You must not connect it to another battery or it might pull down the cells on the good battery too. Thus may potentially cause the bad cell to 'pop' and even start a fire.

If the other 4S batteries are at 11V then they are quite badly over discharged too, 14V is about the lowest you would ever want to take a 4S battery... Are you sure the batteries are 4S and not 3S?

It's maybe possible that the bad battery can be recovered using the NiMh trickle charge method, but you need to be very careful.

 

[sneezy007]

Thank you Smoggie for confirming my suspicions. Once I saw the battery was at 0% for fuel, I figured it was toast.
Can I use it as a bench test battery? If not what is the best way to dispose of them?

I checked the other batteries again. My mistake they are 4S batteries, each one is at 15 volts. It looks like he gave them to me fully charged. They've been sitting like that all winter.

Dino

 

[Smoggie]

16.8v is full charge for a 4s battery. 15v is fine for storage so they should be ok.

If the other battery has been at 9v for a long time then it’s probably toast. You could maybe check the individual cell voltages, if they are all over 2v then you might be able to recover it.

 

[sneezy007]

Good to know, I'm still learning about this lipos. So much to learn in this hobby.

I checked the individual cells and they range from 2.0 to 2.4v.

 

[Tony]

That is quite low. Anything below about 3.4 volts per cell can damage the battery. Especially for an extended period of time.

 

[sneezy007]

I think that battery is toast. It's been sitting like that all winter.

 

[Smoggie]

I think that battery is toast. It's been sitting like that all winter.

Most likely you are right but if the cells are not puffy it might be worth an attempt at recovery. To recover an over discharged battery you set the charger to NiMh battery type and charge at a vary low rate just long enough so that all the cells come up to 3.3V. You need to constantly and closely monitor the battery while you are doing this, do not leave untended. It should only take a few minutes to get the cells up to 3.3V, once they are there stop the charge and reset the charger to standard LiPo balance charge mode and charge as you would normally, but again closely monitor .

Sometimes it works, sometimes it doesnt.

 

[sneezy007]

Thanks for your help Smoggie.
Dino

 

[Dennis H]

I have parallel charged 8 batteries at the same time, same bank. "ALL" cells must be close (voltage wise) before doing something like this.

I use a Duo 406 with a 1,500w power supply.

After doing this a few times, I now only charge 4 batteries at a time on one bank, the other 4 on the second bank, if I need 8 charged batteries.

I guess I was testing the limits of the 406, it worked, but when charging 8, it definetly takes a long time. In fact, I mostly only parallel 2 at a time now. They charge must faster.

After flying, I storage charge my batteries. When I know I am going to fly, I will charge them the day before, or the day of the flights.

Nothing beats have a good charger, it makes all the difference in the world.

PS: If any of my batteries are below 3.4v, I pull them from the stack and deal with it separately. Anything under 3 is usually toast. I have replaced a single cell in 6 cell batteries. I DON'T recommend this, it's dangerous, I do have an electrical background, but the only drawback is this battery even after replacing the bad cell will usually go bad within 3 or 4 months. I guess the other 5 cells can't handle a newbie in the pack.

I have taken 6 cell batteries and made them 3 cell, then use a series connector to bring them back to 22.2 volts. This seems to work OK.

DON'T TRY ANY OF THE ABOVE UNLESS YOU HAVE ELECTRICAL BACKGROUND EXPERIENCE. IT'S VERY DANGEROUS AND EASY TO CROSS WIRES which will cause a phosphorus type fire that will have to be smothered out to stop, or they will burn themselves out.

On another note, I have received brand new "bad" batteries. I always watch the first 5 minutes of charging and never leave the room when charging. One time I pressed the start button and noticed my 406 going crazy. The battery started puffing immediately and I JERK OUT the connections. There is not a doubt in my mind this one battery would have exploded in less than 15 seconds more. I didn't even think about hitting the stop button. I guess my experience kicked in as that's exactly what I would have done at work. I carefully got it out of my shop and put it on the concrete driveway. The next day I properly disposed of the battery. There was no way I was going to ship it back.

 

[sneezy007]

Thanks Dennis, I appreciate your input. I'm new to the world of parallel charging.
I definitely don't have an electrical background.
Dino

 

[Dennis H]

Don't even ask, LOL.

I was making a 4 battery parallel charging lead, plus a balance cord to handle 4 22.2v 5000mAh batteries for a friend.

Things got out of control, Sorta of.

Dennis

 

[Dennis H]

 

[Dennis H]

Replacing a faulty rocker switch in my Futaba 14SG, dropped it and the switch lever broke off.

Getting the switch off the green board is the hardest part of replacing a switch. Soldering the new one one, simple.

 

[Dennis H]

Parallel cord Left, Series connector Right Side. I usually custom make them using the smallest amount of wire possible for the Helicopter their going on. On both below, I use the same amount of wire on each cord. Other Words, I don't have 6" (inches) on one battery, and 4" inches on the other battery. I keep things even as possible. I also leave enough wire incase I either have to repair or replace a plug.

By the way, I have had great success with Floureon Batteries. I have several close to two years old. When charging, the IR's are single digit and very close to each other. Pulse is my favorite.

Feel free to ask questions any time. Dennis

 

[Dennis H]

The Venom charger in the above picture is a GREAT charger also. I usually charge my TX batteries on this charger. Both chargers are powered with one power pack.

All cords are made with 10 AWG , the Blue wire seen is what I now use when making Series Connectors, makes is "very" easy to identify a Series converter.

 

[sneezy007]

My brain hurts looking at these pictures
Dino

 

[Smoggie]

Here’s mine, charging as I type this:

 

[Dennis H]

Question: If you have a 22.2v 4500 mAh battery, and a 22.2v 5000 mAh battery, can they both be parallel charged setting you charger to 9500 mAh's?

 

[Tony]

Yes they can. The only thing you have to match is the voltage of the packs/cells. MAH doesn't matter and each battery will be properly charged to it's rated MAH.