Lipos

peterwaller · Post by **peterwaller** » Mon Jan 15, 2007 4:32 pm

Don't confuse the capacity of a battery in milli amp hours and the charge rate in milli amps. Most non lithium batteries are charged at the 10 hour rate unless specified as fast charge. ie a 400mah battery would be charged at 40 ma but because charging is not a very efficient thing you charge for 14 hours. Most lithiums can be charged at fairly high rates I tend to charge my Kokam's as follows: 145mah at 100ma, 220mah at 300ma and 360mah at 500ma. Some cheaper cells have much lower maximum discharge currents and are likly to require a slower charge. If the cells have balloned it is almost certainly a case of over charging either by too much current or by charging to too high a voltage. Lithium cells are normall constant current charged until they reach 4.2 volts per cell then constant voltage charged until the current drops to a very low value when charging is stopped.

patdied · Post by **patdied** » Mon Jan 15, 2007 9:50 pm

Ok, I just went to read my charger and I have a 11.1V/400mAh battery. The charger had a 4.2V,8.4V,12.6V Voltage Selection. The current Switch had(they are in mA) 2000,1500,1200,900,600,300,100 and 0. For my battery I would have to set it to 8.4V and im not sure what mA because I can't find any in between 100-0.

...400mah battery would be charged at 40 ma...

peterwaller · Post by **peterwaller** » Tue Jan 16, 2007 9:12 am

It is always confusing when some quote the the nominal voltage (3.7v)and some the maximum voltage (4.2v) per cell for lithium batteries.
No Cells Nominal Maximum
1................3.7.............4.2
2................7.4.............8.4
3...............11.1...........12.6
If you have an 11.1v pack it has three cells and should be charged on the 12.6v setting. As for the current this can vary but check the documentation that came with the battery. If you cant find a recommended current and the supplier is unable to supply the information I would suggest the 100 ma setting as the safest. I always keep an eye on my lithiums while charging and always in the garage.
The 40ma charge I quoted was for non lithium batteries.

Simon Windisch · Post by **Simon Windisch** » Tue Jan 16, 2007 7:23 pm

Thanks Peter, they are lithiums.

Simon

patdied · Post by **patdied** » Tue Jan 16, 2007 8:47 pm

Thanks for that help, so that means the battery would charge pritty fast

.

Post by **BeligerAnt** » Tue Jan 16, 2007 10:23 pm

It takes about 4 hours to fully charge a Lithium battery at a 1C rate.
C is the capacity (mAh)

However, most of the charging is done in the first quarter of the time so many chargers will tell you the battery is fully charged after 1hr @ 1C.

If you charge at less than 1C, it will take longer. DO NOT charge lithium batteries at more than 1C - they really don't like it!

You CANNOT fast-charge lithium batteries, unlike nickel-based ones (NiCd or NiMH) which can be charged in as little as 15 mins!

patdied · Post by **patdied** » Wed Jan 17, 2007 1:54 am

Aww...Even charging a battery is confusing

.

So charge my 11.1V/400mAh at 12.6 volts and 100 mA, thats over the normal amount. My charger can't get any lower execpt for the voltage selection.

What if I charged it at 8.4 volts and 100mA?

peterwaller · Post by **peterwaller** » Wed Jan 17, 2007 7:17 pm

If you set the charger to 8.4V it won't charge the battery as its voltage is already higher than that. Most good 400 mah lithiums can be charged at up to 1C as Gary (BeligerAnt) says which is 400ma I was only suggesting the lower current 100ma as I dont know the make or the current rating of your batteries. The best Lithiums seem to have about a 20C continuous rating with a 30C peak discharge current. If yours have they can almost certainly take the 400ma charge. If you don't have any data and can't find it on the web post the make and model of your batteries here and we will see if anyone knows more about them. As I said before the 40 ma was for non lithium cells.

Simon Windisch · Post by **Simon Windisch** » Wed Jan 17, 2007 11:38 pm

FYI I just realosed I had my charger on the 3 cell setting for a two cell battery.

Simon

patdied · Post by **patdied** » Thu Jan 18, 2007 1:21 am

Ok I took some pictures of the charger and got a picture of the battery. The battery is:
3 Cell Li Poly, 11.1v (nominal)
400Mah (rated up to 4amp output)
JST male connector
1.28oz
2x1.21x.49"

I got it from the shop.

The charger said "read user's guide carefully before using," and it never came with the manual

.

Battery picture
http://www.box.net/public/uqfy7afvf0

Top and bottom picture of the charger.
http://www.box.net/public/db1718uld2
http://www.box.net/public/5pqxzb06qy

I also went to the website and it had no help.
Thank you guys!