RC10Talk - The Net's Largest Vintage R/C Community

Ok I have a 2c Zippy 4000mah lipo with a Reedy brushed motor and an LRP V1 runner. I'm using a MRC 965 charger for balance charging. Also have a low voltage alarm. The combo worked flawless for last two weeks until today. I charged the battery for the typical 1 hr or so,took it to street and within ten mins the low voltage alarm is going off. I thought maybe the charger wasn't plugged in so I charged again. This time same thing alarm goes off quick. Both times I noticed the voltage display on charger was reading 0.00. The last time I charged it started off at the setting I use which is 3.25 v and steadily went down. I'm not sure what's going on here. Is it possible the low voltage alarm is screwed ? Is there away to test the battery? Will hobby shops do that .?

Sounds like the pack has a dead cell, if you have a multimeter check the voltage of each individual cell through the balance plug.

I'll have to get a voltmeter and check , how does a cell just go dead?

Lipo technology still has some hiccups, more often with cheaper packs but not always the case.
When/if i buy Lipo's from overseas, I'll order 2 just to be safe.

Charge in balance mode and then discharge in balance mode. lipo's aren't the holy grail. If it doesn't work right then just throw it away. Its done.

foots wrote:Charge in balance mode and then discharge in balance mode. lipo's aren't the holy grail. If it doesn't work right then just throw it away. Its done.

Be safe and dispose of properly, so you don't set the house on fire. Last thing you want is a lipo going puffy and meltdown in your trash can...

Speaking of puffy LiPos...one of my GensAce LiPos got a bit puffy the last time I balance-charged it. I remember checking it frequently and it never even got warm to the touch. Needless to say, I was a bit pissed off to notice the plastic outer case was separating at the side seams. It's not REALLY puffy, I can easily press it and tape it together, but now I'm concerned that an otherwise new, hardly used battery will be at risk of burning up one of my cars.

It's one of these:
http://www.hobbypartz.com/98p-25c-4000-2s1p-hardcase-direct.html

Can LiPos sometimes just go puffy for no reason, and possibly be defective?

Coelacanth wrote:Speaking of puffy LiPos...one of my GensAce LiPos got a bit puffy the last time I balance-charged it. I remember checking it frequently and it never even got warm to the touch. Needless to say, I was a bit pissed off to notice the plastic outer case was separating at the side seams. It's not REALLY puffy, I can easily press it and tape it together, but now I'm concerned that an otherwise new, hardly used battery will be at risk of burning up one of my cars.

It's one of these:
http://www.hobbypartz.com/98p-25c-4000-2s1p-hardcase-direct.html

Can LiPos sometimes just go puffy for no reason, and possibly be defective?

Usually there's a reason. I've had a couple go puffy over the years. One went puffy after I left it nearly fully charged for a couple of weeks (I usually leave them at 40% charge for this reason) My fault, I should have checked it after racing, I failed to start a final hence why the lipo was nearly fully charged.

The other I had that went puffy was a couple of years old, and to be honest it had a hard life in a mod class. High amp drain can also make lipos swell a little.

Paul.

I wonder why it would go puffy shortly after balance-charging it, and it never even got warm? The case was still cool to the touch after charging.

Ok guys figured out the problem. I had the deans plugs soldered backwards on charger and esc ,so the battery wires we're also plugged in backwards. Once I fixed my MRC charger balance charged for along time it eventually had both cells almost identical .only problem is once I had car out on street the voltage alarm went off after 5 Mins. So either that's broke or battery is damaged.