Over charging Lipos?
 

I have a Hitec X4 Plus charger. I have left things set to factory parameters and everything has worked great so far. Most of my lipos are 5000mah to 5300mah and the charger has been left at 5000mah capacity cutoff. I balance charge every time.

Recently I purchased two 6500mah 70c lipos for more run time, but I don't see a difference between the 6500mah and the 5000mah batteries. The charger will stop charging on occasion at 5000mah capacity cutoff. So I changed the capacity cutoff to 6500mah.

Now when charging the 5000mah and 5300mah batteries the charger shows I'm going over mah capacity. I manually shut the charge off on my 5300mah battery when the charger showed 5400mah charged.

My questions are,

1) Is my charger showing a correct reading or just a ballpark idea?
2) Am I over using my lipos and draining them down too low? (LVC is 6.4 volts)
3) Should I use the capacity cutoff on my charger?
4) If cutting off capacity cutoff will my charger over charge the batteries?

lips are kinda funny. with them you want to charge 2s to a volt level, not a capacity level. Some batteries will take more mah than they are advertised to take, but it usually isn't very much. maybe 50-100 mah. Set the capacity for something you know you aren't going to hit, and just charge until the batteries hit 8.4 volts.

make sure you are charging in lipo mode.

I am in lipo mode and they charge to 8.4 volts fairly quickly. Once at 8.4 volts they will sometimes charge for 10-15 more minutes at a lower amp, like a trickle charge.

That's normal. Called CC/CV. Up to 4.2V/cell in CC - constant current, then CV - constant voltage as current drops off. Then at some point the charger will finish.

It is OK to stop the charge early if you want, the last bit adds very little capacity/run time.

For the LVC, better to stop running as soon as the power drops off.

Thanks. I was unsure if the charger was over charging the lipos by putting more mah in the battery then what it was rated for.

The charger stops when it's "delta peak" is reached. That is a function of voltage, not capacity. This is true of lipos and nimh. Iv'e never used the capacity cutoff feature but according to the manual it is not available in lipo mode, but is available in nimh/nicad. Makes me wonder how you are getting it in lipo mode.

I'm not sure about the manual but in Balance Lipo charge mode it will shut off at a mah capacity that you can select in settings.

Please tell us more. Take a couple pics, one of the charger screen in cap cutoff in lipo mode would be nice. I could not get any screen to change the cutoff cap on my charger.
EDIT
and i just tried again to find "cap cutoff" in lipo balance mode and there is no option to change the cutoff.

I have the capacity cutoff in lipo mode on my orion touch charger. I have never used it though. (as i just set it to like 10,000 mah and left it) I don't know why they have it. Places that check batteries always check for voltage, not mah, so i don't know why you would even need it.

Perhaps a little off topic, but lipos do not "delta peak" like a nickel based battery. Voltage controlled yes, but not a peak and delta drop off.

Attachment 1156904
This picture shows the lipo charging and its put 57mah of charge in the battery that was already at 8.4v. I set the capacity cutoff at 100mah because the battery is already charged.

Attachment 1156905
This picture shows the charger has cutoff and says CAPA because it has reached its programed capacity of 100mah showed in the lower right side of the screen.

So if its already charged to 8.4v why did the charger supposedly put 100mah into the battery?

Like any other battery, they will self discharge when not in use. The batterys own internal resistance will discharge the battery over time.

You charge lipo to 4.2V/cell until they take no more current. If you don'y exceed that voltage you cannot overcharge them. mAh and time limits are failsafes not end of charge detectors.

Several things can make your charger show more mAh that written on the battery
- cells do have higher capacity (at least when new)
- charger current sensor not very precise
- a little capacity lost as heat during charging

I was thinking it was a fail safe, just wanted to make sure. Im going to set the capacity cutoff at 7500mah which is 1000 more then my largest packs.