LiPo Battery Help... Don't really want a fire tonight

[seaninsc]

Hi all,
I just finished my first quadcopter build today. I charged my Turnigy Nano-Tech 1300mah 3s 45c-90c LiPo on a Turnigy Accucell 6 and started messing around with the quad. I only took it a few feet off the ground for only seconds at a time, so I didn't think to much of the battery level. I have a buzzer set up to sound off when a cell is less than 3.4, I i wasn't really worried until my quad wouldn't take off anymore (I'm guessing it is a default for the ESCs to stop working after a certain voltage is reached. I ran back to my charger and looked at the cells. 2 and 3 were around 3.25v-3.3v, while 1 was 2.92v-2.98v (I forgot exactly). I immediately started to balance charge to a storage voltage of 3.8 per cell. After that, I threw it into a LiPo bag, sealed it up, and jumped on this forum .

So, my question is: is the battery ruined or can I still use it? It looks visually perfect with no swelling. It didn't get hot while charging. The Accucell brought the 2.9v up to the other cells relatively quickly, but I don't know if it really did or not (only a $30 charger). Right now all the cells read 3.8v

Being new, I only bought the one battery, so I'm hoping I can still use it. I'd hate to order another one off HobbyKing, but I will if it means I won't destroy my quad or burn my house down.

Thanks in advance,
Sean

 

[cranialrectosis]

Do you have a battery checker that can show you current cell by cell voltage?

Is the lipo still fully charged an hour or two later or is one cell down by 3 or 4 volts.

I don't think it will explode on you. Don't leave it on a charger or tester all night. I wouldn't leave it fully charged all night.

I do think it will have reduced life as a result. I just don't think it will be obvious for a few cycles.

I would always balance charge this lipo.

 

[seaninsc]

Thanks for the fast reply.
I just checked it on my charger (don't have a designated checker) and all the cells are 3.79, 0.01 volts lower than they were a few hours ago. They are all the same voltage according to the charger. Is this a good sign or a bad sign?

What voltage do you suggest I store them overnight at?

Also, just as a side question, would it be beneficial to charge the battery at below 1C from now on (like 0.1C)?

 

[Cyberdactyl]

It's all VERY low probability of a fire if you have a LiPo sitting around somewhat balanced and between 2.9 and 4.2 volts per cell.

Where it gets hairy is when you do not balance charge. Always, ALWAYS balance charge.

However if you ever drop your batteries under what your charger will recognize as a valid healthy LiPo, you ...can... bring them back to life by slowly charging as a NiCad at a very low charge rate. You should monitor them closely during this process for the 5-30 minutes it takes for each cell to reach ~2.9V per cell. Then switch over to LiPo and BALANCE charge them fully**.

**As we all know, not all our LiPos are charged in a safety bag, but any LiPo you have rescued from complete death, or a deep discharge should never be recharged without a bag.

 

[Ethanator10000]

Thanks for the fast reply.
I just checked it on my charger (don't have a designated checker) and all the cells are 3.79, 0.01 volts lower than they were a few hours ago. They are all the same voltage according to the charger. Is this a good sign or a bad sign?

What voltage do you suggest I store them overnight at?

Also, just as a side question, would it be beneficial to charge the battery at below 1C from now on (like 0.1C)?

From what I've heard, there is no need to charge a LiPo to a certain voltage for just overnight storage. I think that you should store them if you won't use it for a week or so.

A well charged Lipo should have all equally balanced cells, however after over-discharging a cell, it might lose voltage more easily and have less capacity thus resulting in a un-balanced battery.

Is the battery puffy or soft now? If it is, it might be best to say goodbye to it.

Here is a video I found about charging a over-discharged Lipo. Since you were able to charge it normally without the first step he did with the Nicad setting, your situation is probably a lot less extreme, but there is still a bit of information in there about over-discharged Lipos. (I do not own the video)

https://www.youtube.com/watch?v=vusc1BFJX40

 

[seaninsc]

The pack is the same stiffness as when I got it. I just ordered an external LiPo alarm for my rig, hopefully it will work better than the VBAT on the Naze32. Any ideas of why the buzzer didn't go off? The buzzer works and the parameters were set on Cleanflight to a 3.4V alarm.