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IS IT DEAD

skymaster

Well-known member
#1
Well last night i was clearing some stuff that needed to be cleared out of the house, and came across my battery's had not checked on them for a while since the weather has been horrible. so i decided to check all of them. i think i lost one of them. 850mAh 3s checked all cells and one of the cells came up as 3.9- 0.000 and 3.852 so lets just say i did not had a good night sleep. should i just scrapp it or try to save it and make it into a 2cell?
 

Piotrsko

Well-known member
#3
At this point you haven't done anything to really determine that it is failed or useable. Whats the voltage on the motor connector? More than 8 volts? Then your balance wire is toast. Is it puffy/bloated? How desperate are you to save the other cells? Others will interject their opinions soon.
 

BATTLEAXE

Well-known member
#4
Well last night i was clearing some stuff that needed to be cleared out of the house, and came across my battery's had not checked on them for a while since the weather has been horrible. so i decided to check all of them. i think i lost one of them. 850mAh 3s checked all cells and one of the cells came up as 3.9- 0.000 and 3.852 so lets just say i did not had a good night sleep. should i just scrapp it or try to save it and make it into a 2cell?
If there is no physical damage to it then if I was you I would try to charge it. Keep an eye on it for any overheating. If you have a digital charger it might not let you force charge it.

Beyond that it could be that one of your balance lead connections in the battery has come loose and just isn't reading the second cell. But I wouldn't use it as a 2 cell battery.
 

basslord1124

Well-known member
#5
Honestly, it may be ok aside from a faulty balance lead if that's the problem. Otherwise, I do know folks have taken lipos and modify them if a cell or 2 ended up being bad. In the end though it's up to you. If you wanna tinker around with lipo surgery go right ahead...just be safe and research what you need to do beforehand. And make sure you got quick access to outside if something goes bad. If I knew how to do that type of stuff, I'd give it a shot at least for the knowledge and experience of it.

If you're not comfortable with it, a 3S 850 is a fairly cheap battery and you could just go buy a new one.
 

sprzout

Knower of useless information
Mentor
#6
Honestly, it may be ok aside from a faulty balance lead if that's the problem. Otherwise, I do know folks have taken lipos and modify them if a cell or 2 ended up being bad. In the end though it's up to you. If you wanna tinker around with lipo surgery go right ahead...just be safe and research what you need to do beforehand. And make sure you got quick access to outside if something goes bad. If I knew how to do that type of stuff, I'd give it a shot at least for the knowledge and experience of it.

If you're not comfortable with it, a 3S 850 is a fairly cheap battery and you could just go buy a new one.
That's kinda what I'm leaning towards. I've seen guys try to fly with questionable batteries, only to have problems later (such as smoke and/or fire). I know that we want to try and save some stuff, but batteries are one of those things where there I have a healthy respect for safety. I'd rather not see you have something serious happen where it causes a plane to burn up, or worse, your home/hands/face/other body parts.
 

LitterBug

Troll Spammer
#7
I have one questionable battery that is referred to as Mr. Sag. He is no longer used for actual flight, but rather just for bench work and has SAG written on him in print that can not be missed. This sounds like a good candidate for a Sag Buddy. Better safe than sorry if you can not find the exact reason one cell is showing low or AWOL.

Cheers!
LitterBug
 

sprzout

Knower of useless information
Mentor
#8
I have one questionable battery that is referred to as Mr. Sag. He is no longer used for actual flight, but rather just for bench work and has SAG written on him in print that can not be missed. This sounds like a good candidate for a Sag Buddy. Better safe than sorry if you can not find the exact reason one cell is showing low or AWOL.

Cheers!
LitterBug
I had a 3S battery like that; it went through a crash and one cell zeroed out. I used it to test ESC connections until just the other night when I couldn't get anything to power on when I plugged it in. I figure it's now ready for recycling. :)
 

sprzout

Knower of useless information
Mentor
#12
here is what it looks like.
I'm going to go with it being a bad cell. Unless you REALLY know what you're doing, it could result in a potential workshop fire, and a lot of the time, the battery won't charge properly with that cell reading as dead, or potentially overcharging the other cells in an effort to charge up the low cell.

Let me put it this way:

Which is more cost effective - spending $15 on a new 850 3S battery, or worrying about a battery that might potentially go up?
 
#13
If you have a dead cell in a battery and you run it on something, that cell will either puff up an insane amount or screw up everything by lowering power/exploding, so I would just buy a new one.
 

evranch

Well-known member
#14
For the size/cost of that battery I would just scrap it rather than try to salvage the other 2 cells. A cell that has hit 0.00 will never put out the currents to fly again.
 
#15
You're only checking that with the balance lead, and it could still be a single connector pin or lead that's gone faulty. What voltage do you read across the main leads?
 

skymaster

Well-known member
#16
Thank's guys for all the info but i know this battery is done. i am just using this battery as how battery's go bad. so as the time that i saw the lipo had a bad cell in it. it went from being a battery to a research item (i was going to say Guinea pig but is sound to cruel) i'm going to try and remove the cell #2 cable from the balancing charging connector and i will try and do a storage charge on the other cells with my venom pro 2. if it detects the only 2cells it should kind of work and them i could reconnect the other #2 cell and try to charge somewhere outside i will make barricade around it for safety. what do you guy think? i also used a multi meter on it the two cell came like in the pictures and the #2 cell game me a reading of 10.something.
 

evranch

Well-known member
#17
If your total voltage is over 10 on the main leads it may just be the balance lead after all. Open the end of the battery pack, very carefully without contacting any metal parts with the knife or puncturing the cells, and measure the tabs on the cells if you want to proceed with this route.

You cannot charge the battery by modifying the balance lead without removing the damaged cell itself from the main series connection. It will puff up for sure and might catch fire. The balance lead is not for the main charging current, but for monitoring the cell voltages and slightly adjusting them. All the current will still be passing through that dead cell, but it will be completely unmonitored which is a recipe for disaster.

As per a discussion we had on another thread, if you measure the voltage between the tabs on the cell to be truly 0.00v, you could solder a jumper over it, effectively removing it from the pack. You will then need to rearrange your balance leads for the new 2s battery configuration.

Otherwise you need to desolder the tabs and remove the cell from the pack physically.

"Kind of work" is not good enough in the world of lithium cells, it tends to lead to either a dead pack or a fire.