Warning to anyone new to RC and Lipo batterys

[bgchip]

Hi I have a ONYX235 charger. I was charging an ONYX 4000, 3 cell, 25C, LIPO. The warnings say never to charge over 4.2 per cell. This setup appeared to be charging each cell at 4.5 a cell. Charge time was amazing fast. Is that OK? Am I doing something wrong? I keep the battery in a ammo case. Thank you

[Turner]

Nope, cell voltage should never be over 4.2 for LiPo. 4.5 is damn close to bursting into flames.

[bgchip]

What would cause this charger to read this high? The charger goes through a series of screens when I start charge. At one point the screens shows a reading for each cell. That's where the it will read 4.5. The instructions have a 4.196. I am afraid of these batteries. I bought an ammo box. I have the charger bag. I am trying to take all safety precautions. I don't want a fire. Thank you

[Turner]

There could be something wrong with it. Have you checked the voltages with another device such as a cell checker or voltmeter? If the charger is really over charging by that much I would stop using it or very carefully monitor charging voltages with a volt meter and stop the charge when the first cell reaches 4.2 volts.

[bgchip]

Thanks for the help. This may be a dumb question but how do you check voltages on a LIPO? My battery is a 3 cell battery. The battery pack is well wrapped. How do I check each cell voltage? Or do I only check the battery voltage? I have a VOM and check my NICADs.

[kyleservicetech]

Originally Posted by bgchip

Thanks for the help. This may be a dumb question but how do you check voltages on a LIPO? My battery is a 3 cell battery. The battery pack is well wrapped. How do I check each cell voltage? Or do I only check the battery voltage? I have a VOM and check my NICADs.

Take a look at the balance connector on your LiPo's. Generally, the cells run across the pins of the balance connector in succession. So, first you need to locate the negative end of the battery, and connect the black wire of your VOM to that negative lead. Then put the red wire on the first pin adjacent to the negative wire, should be 3.8 volts DC or so. Move to the next pin, should be 7.6 Volts or so, and last should be 11.4 Volts or so depending on state of charge on your battery.

Usually these balance connectors have a pin locking location on the back of the plastic shell you can use to probe with your VOM. Don't push to hard though, you might "Unlock" that pin, and it could come out. If it does, just tweak that locking thing back and re-insert the pin.

You are not going to use a Channel Lock pliers for this job! Something very small such as the point of an Exacto knife, and a magnifier visor to see what's going on.

(Just like checking your Nicads)

[Turner]

Or something like this:

Cell Checker

[hayofstacks]

Or for less then 1/2 the price with $2 shipping through headsup.

http://www.headsuprc.com/servlet/the...Checker/Detail

[Turner]

That's a better deal, Thanks.

[bgchip]

Absolutely, but thanks for the previous help. Now if I could tell what the output of my charger is. The LCD said over 4.5.

[Mikejeff]

well, thank you for message, really useful for me.

[fhhuber]

4.2 v/cell is considered full.
This is used because it has a bit of a safety margin if doing a charge without balancing and there is very little capacity above 4.2v/cell.

The cells can tolerate 4.4 v with no issues at a gain of usually less than 1% capacity. So if you fail to balance every charge and drift leaves a 2S pack at 4.0v in one cell and 4.4 in the other you still have essentially no risk of fire.

LiPos are expected to burn anywhere from 4.5 v to 5.0 v (usually above 4.7 v) in any one cell... not predictable exactly when.

Older LiPo chargers were not as accurate as what we have now... and many did not have balance capability at all. Early LiPo packs didn't even have balance plugs and this is where we got the 4.2 v/cell max.

Its still safer to set the charger at 4.2/cell for LiPos. But don't panic if you find a cell at 4.5. Just put a normal load on it and bring it back down. It should be fine.

If your charger is consistently pushing cells above 4.2 v in balance mode... something is set wrong or the charger is broke. Its pretty easy with some programmable chargers to get into the "user setting" menu accidentally and when intending to set the charge rate to be inputting the volts per cell. Be very careful to read just what you are setting.