need help with battery voltage. plz?

[Drayken D]

I just bought a few packs, matched 2400's. They are 1.13, and discharged at 25 amps. My father bought 1.14, and discharged at 20 amps. Both were done at 5.0 amps charge. I almost 100% mine has lower resistance on the sticker. Which is the better battery(Have yet to test them)

My main question is this, what is the difference in different discharge rates. Some guy told me that lower discharge rates, will show higher voltage, when pertaining to the matching stickers. Is this true? He had two packs, one was 1.166 at 30amps, and another at 1.166 at 20amps, he said the 30 amp battery was ALOT better. Can anyone give me a lesson on how to read and compare? thanks

[Leet TC3]

The avg. voltage posted is just that: The AVERAGE voltage measured at the battery over the length of the discharge.

The more amperage you use to discharge the battery, the lower the avg. voltage. You are, afterall, drawing more power from the battery at higher amperages. Therefore, a higher amperage discharge will always have a lower avg. voltage if the batteries are the same.

This is why you should always pay attention to the discharge amperage value on a battery label. Different manufacturers use different amperages. e.g. Trinity uses 30 amp discharges when rating their batteries while Integy uses 20 amps. Trinity will also list their avg. voltgage at 20 amp discharge on their label.

There is a new rating that takes this into account, called milliwatt hours (mwh). The formuala uses avg. voltage and runtime at a given amp discharge rate. This will make it easier to compare batteries from different manufacturers.

[Grizzbob]

You're on the right track, though you can still find good cells that are matched at 20 amps. The real advantage to buying ones matched at 30 amps is that the higher discharge rate seems better at weeding out the bad cells. A number of people have tried testing packs at 20 & 30 amps, & they've said that a good pack at 30 amps is a good pack at 20, but not every pack matched at 20 will be as good at 30. Now, I can see cells averaging 1.16 volts at 20 amps, but I've never seen one do it at 30, 1.13 is the best I've seen at that, so anyone telling you they have some putting out 1.16 at 30, I'd be very suspicious. A good example of this is Integy, who artificially inflates their cells voltage numbers by cutting off the voltage readings at a certain number of seconds(about 390, I believe), & really any high capacity cells will put out better numbers if you do that cutoff. However, reputable matchers like Trinity do NOT do any cutoff, they measure voltage the entire discharge time, & then give you the average. if you did the same for Integy's, they'd look about the same, or maybe lower(it depends, so your mileage may vary)..... :)

[Drayken D]

Grizzbob, I saw the stickers on the batteries. It was 1.166 or something like that. They were Reedy's. The guy I was talking to is sponsored by Associated. He had Reedy batteries, motor, and LRP ESC, on a B3. He is GOOD. Anyhow, thx for the insights. I figure that since my betteries were discharged at 25, with 1.13, they are as good or better than 1.14 at 20. Besides, the guy that matched my cells, cycles them 5 times, most matchers do 3.

[Grizzbob]

That explains it, the readings are also different at 25 amps than they are at 20 or 30. However, I don't have any idea what the 25 amps numbers would translate to at the other amperages. If possible, you might ask someone who has a Competition Electronics Turbo 30 or 35 to do a test cycle on your packs, that'd be the best way to really gauge each one's relative performance..... :)