Help me obtain a better understanding of discharge rates

[Docwolf]

Back when I worked in IT for my company we had a rash of lenovo laptop batteries that the latches failed on. Lenovo just sent us new batteries and told us to toss the ones we had. All that was wrong with them was the latch, the cells were fine. So I took home and figured I could find a use for them, if not in a truck then in a TX or even for a winch.

Starting to finally get around to see if they are of any use to me now, I have them tore down and I am trying to self educate on their specs.

I have:
6 Blue that I cannot find info on 18650 6H20313 60959 - roughly 2200mah

6 Panasonic green ST US18650GR - roughly 2000mah

6 Red that I cannot find info on HIUFJT5 - roughly 2600mah

AND
9 Panasonic grey NCR18650 MH12210 - roughly 2900mah

Obviously the 18650 is a industry ID and they are all Li-on. The capacity was easy to find for the ones I could ID, the others are a estimation based on the pack capacity. All colors are each from the same pack.

So the 9s will fit in a build I have as 3p3s, but I want to make sure I have enough discharge for this rig. The plan is to have a 4000 to 5000kv brushless system to make a all around Monster (The 55' for those familiar) . Previously it had a 15t brushed system and two 1600mah 3s 25-50c packs was enough to spread the load out and not over discharge a pack. I did nearly cook a single pack on my first test so I fully understand the issue here.

So what I need to understand now I guess is, how is the "C" rating figured? Is it a percentage of the total voltage? Is it per cell? What is the definition of the metric?

 

[Awesome-Sauce RC]

i use old laptop cells i harvested for 2/3 cell packs to power my winch or lighting.

the discharge rate for these 18650 cells is VERY low, maybe 1.5-2c discharge, so they really are not suitable for an esc to use unless its something very small and light like a micro rig.

connecting them in series or parallel wont make any usable difference to the discharge but they are handy to power other things on your rig.

i have 2x2s packs i made for my lighting and 1x3s pack i made to power my winch if i dont want to run either from my main lipo, normally if we do a night run and its so darn cold i use them to save my precious main pack mah.


tony

 

[Docwolf]

That is what I was afraid of, thanks.

 

[GodSpeed999]

Why bother when guys are buying 3S 2200mAh 20-30c batteries for $6 bucks?

 

[Docwolf]

These were free... Plus I have a form factor issue to conform to.

 

[JokersWild]

Donno how to figure c rating, bit do know knowing it will change quite a few factors.

There have been talks about how most of the discharge rates are just un rated and just printed.

Chris the battery man, I'm sure john over at Holmes and someone else would have a better idea on how to figure such rates without burning down the house to say. Lol. Not sure if a lap top has a good discharge rate to begin with.

 

[Docwolf]

Sounds like they are pretty low, which stands to reason for the application.

 

[Johnnysplits]

C rating is the continuous output of a battery measured in amps. Ex: 5000mah 30C ... 5 x 30 = 150 amps continuous. You multiply mah by C rating.

 

[Docwolf]

Aww, okay. Go the grey have a constant discharge of 408mA which is .408 amp right. So if the Mah is 2900, that is 2.9 amps, come out to 7c right? Way too low which should be obvious by the discharge rate but I didn't comprehend that the first time.... For some reason.

 

[JokersWild]

Was figuring we did not know the c rating at all. Lol. But yea the discharge of them seems quite low to say the least.

 

[Docwolf]

Guess I will just spend the money and buy the individual cells to build my own. I am sure I can find uses for these.