Hi

If i were to buy this battery ([link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXPWJ3&P=7]Battery[/link]) and then run it at maximum capacity. How long would it run. Does anyone know any formulas on how to figure it out based on resistance and voltage. We didn't learn maximum capacities and battery life in Physics 12.

Thanks

If you consider the 20C to be "maximum capacity" then it should be 3 minutes or less. It is 5000 maHOUR , that is 5000 ma per hr or a multiple of that such as 2500 per 30 minutes at twice the current of 10 amps. The higher the current the lower capacity will appear.

Ok this makes sense. If I run this battery at with a current of 1 A it will last 5 hours, 2 A 2.5 hours, 4 A 1.25 hours...
I get it now I am amazed I didn't see that simple relationship considering we spent months doing this stuff in Physics.

Thanks alot.

You got it, and chargeing works the same way.

Ok Great. Now I know you arent supposed to drain Lipos to less than 2.5 v per cell. When a battery says 5000mAh and say my boat draws 5A that means that the battery will last 1 hour. Now after that one hour is the battery going to be at 2.5V or will it be toasted.

Thanks allot This is making more and more sense.

The battery SHOULD be around 3.5 RESTING VOLTAGE . I sure wouldn't push it that long for the first time. If the current happened to be 5.2 then you may in fact pull it down too low. It might also only average 1-2 amps and last a lot longer. Usually what I do if I have an unknown discharge current is to time a few runs and then go by this chart as a "fuel gage" Most everyone uses 4.2 as the full mark, but some people use 3, 3.2, 3.5 3.6 3.7 as the empty mark and there isn't a lot of capacity difference between 3 and 3.7

Charge % Open voltage Mah

100.00 4.2 5000
90 4.13 4500
80 4.06 4000
70 3.99 3500
60 3.92 3000
50 3.85 2500
40 3.78 2000
30 3.71 1500
20 3.64 1000
10 3.57 500
0.00 3.5 0

The remaing charge is pretty straight line and the resting voltage is an accurate indicator. If your figures are correct then perhaps a 15 or 30 minute timed run then a rest and voltage check according to chart will confirm.

Thanks Guver

You have been allot of help. What you have taught me has greatly increased my understanding of lipo batteries. I am having trouble getting the charge and kill em NiCd practice out of my head.

Thanks a tonne.

Brett

Yae, I actually think they are easier especially for someone who has no knowledge of Nickel batts. They are much more predictable.