max c rating on nimh aa cells

[truckerzero]

i know most standerd aa cells are rated for a 1 c rating but has any one tried a 2 or 3 c load and if so how did they perform big loss in capacity or cycle life because i know 2500 mh sub c nicads can take 10 c are about the same price but heaveyer

 

[fitek]

Well, my test with the Tenergy AA at 2C showed they did quote poorly; though less so than other Tenergy cells. That's not saying much; if the AAs can be called "bad" then the D cell was "awful."

 

[rybitski]

I am looking at building a pack out of AA NiMh 2600 mAh cells. The plan would be a 36 volt pack with 3 strings of 30 cells. I am new to battery technology (other than SLA's) so I am not sure how reasonable this is. Would this be a feasible pack design for a 750 watt motor or will that be discharging the cells too quickly? If I am doing the math correctly this would be a 3C discharge? If this is not possible with AA size cells then what package would work? I have alot of questions and am feeling a little overwhelmed with all of the numbers.

 

[amberwolf]

I think you need to do a lot more research on NiMH and those types of cells, C-rates, and a few other things before you spend any money on that project.

If you already had everything lying around, you could try it out, but if not, do the research first, so you won't be so disappointed later.

Plus if you manage to find 2600mAh NiMH AA cells that actualy supply anything like that in less than a trickle current, a few people might be interested in them. I havent' found any that even give half of that rating just running a 20-lumen LED flashlight.

 

[slayer]

i am almost certain that there are none aa 3c available like Amberwolf says ...and a couple of rules you have to follow when charging nimh ...they can t be charged in parralel so you would need to make it so that you charge individual pack and then series them to discharge

batteryspace is a good place to buy some loose nimh and maybe take example on how they charge and discharge them (the packs they sell)
better yet buy a pack already built save yourself the trouble

http://www.batteryspace.com/36v-396vbatterypackseries.aspx


you could have some sub c cells that are capable of 6 c or 30 amps discharge for a 4.5 ah

http://www.batteryspace.com/subcsizeseriesbatteries.aspx

 

[liveforphysics]

NiMH is very tough to work with, charging is tricky as best, and you will require a charger and isolation diode for each parallel string.

 

[dogman dan]

Even a dumbass lke me knows it's a bad idea. Rethink the plan with A123 lifepo4, or something.

I know, too damn expensive! But in the end you will find lipo, lifepo4, or something lithium to be cheaper in the cost per ride.

You have an RC plane, so I'd say look into lipo from Hobby King. Starting small, like two 6s 5 ah packs paralelled for 12s voltage is pretty cheap.

 

[slayer]

Plus one on what Dogman says ...also nimh won t work in high temperature i remember a couple of times when the hotest days of summer i had to walk back home cause they where too hot ...

 

[rybitski]

Thanks for all of the replies. I don't know what I was thinking... I was in save money mode so i was searching for alternatives to lipo and got caught up in it. When I stood back and thought about it a 36 v 5Ah lip pack and charger is only $75 more and would be less of a pain. Thanks again for all of the reality checks. I am now thinking about using 2 Turnigy 5s 5Ah 20C in series for 37V.