is there a C rating for nimh batteries

Thinking about a battery build project so is there a c rating for nimh cells. I got a 25 amp motor and I want to build a 20ah pack. Is it going to crash and burn. I saw an article today that said the c was 170 and lith is 200 is that about right.

If I read that correctly. It will discharge at 2c without destroying the battery. I think that is all I really need to know. I really do appreciate the information.

The plan for the battery is to use c cell 9500 mah to create a 36v 19ah battery pack and run my 25amp controller and hub motor. Then at any point along the way I can increase the ah or voltage myself. I like to be able to morph my battery packs.

I did some experimenting with Nimh two years ago I think it was. I found out a lot about them, but since I was trying to integrate them into existing battery pack nothing worked. Now I realize you can't mix chemistries. So I am going to try building a pack all nimh as I go. It should be interesting.

I have a real problem with a lipo since it is what it is, for me at least. This chemistry seems to be a little more forgiving. Once upon a time the nimh batteries were in Toyota hybrid so I think they should work for a little bicycle.

I'm going to buy the cells in 1.2v 9500 mah hour then combine 10 cells for the voltage the build a second ten cell string to my 19ah. If all else fails I can build some flash lights with rechargeable .

Any advice other then you are crazy.

Thanks,

yes I have seen the graphs the give the huge difference in time vs amp drain. It looks like I can pull at least 1.5 c from the pack. I went ahead and ordered the first string. I'm going to build two strings before I deploy them. My first test will be on 36v 19ah. two string pack.

The truth is I'm doubtful that 9.5ah will be the real ah value, as I bought ebay chinese cells. But if it is two strings will be enough to power the bike, I think. If not I'll just add another string.

This is my dead of winter project, so we shall see how it goes maybe I can have it ready in the spring. I use a 2 way switch on my trike so I can put a sla battery on one leg and the nimh on the other, I can use one pack till it is to low to use further the switch to the other so that I can use both without mixing them.

I found a charging formula for nimh batteries. It looks as though the rate is a total of the capacity plus 10% divided by the amp hour of the charger. from complete drain it would be 14 hours. But they warn against over charging so I will have do some experimenting with the charger since I doubt the batteries will be fully drained or fully charged when they are built.

Thats what I figured to. I am starting with a 36 9.5 ah battery. 30 nimh C cells.

I have a motor i used for a friction drive bike and I found a 300 watt 36v controller and throttle in my parts box. so I'm going to test the batteries with it. I expect that the controller for this little beast pulls 10Amps which should be a good test for a single string.

If the battery performs well I will purchase and construct the other batteries. I have built batteries from consumer cells before and they work quite well with my technique.

I use consumer aluminum foil folded several time to make a connector between cells. Use black plastic tape and duct tape to assemble the packs. Since I am doing more systematic testing this time, I am expecting to learn a lot more.

Just to handle the bulk and make the batteries more square I use six volt strings. then assemble them into 36v 9.5 ah boxes then do a parallel with at least two strings. Since I can add a complete 36v 9,5ah battery for 100 bucks I might add a third string before spring.

That would give me a 36v 28ah battery for under 300 bucks. The beauty of it is that I could reconfigure it easily. It isn't a lot cheaper than lipo, but it would be more versatile I think. It might prove a complete bust but what the heck at least I will get it out of my system once and for all.

Okay I'm coming to you guys with another question I can't find the answer to on the net. Maybe I don't know how to phase it for google but here it is anyway.

The 36v battery pack I built needed charging so I did. I did it an hour then read the voltage with my multimeter. I also check along for any over heating. i+I did it every hour for four hours.

When I felt pretty good about it I stopped for the night. So my high end voltage during charging is 41.5 volts. Which from the literature seems to be acceptable. The overnight standing voltage was 38.7 which is about what the cells gave me before I used them.

I am wondering what is a good standing voltage and I can't find it. I find working range is anywhere from 36v to 43volts but what should the standing voltage of a full charged 36v pack be. On sla it is about 39.5 I know that is probably a little hot.

So here it is WHAT IS THE VOLTAGE OF A FULLY CHARGED 36VOLT NIMH PACK.

paul that has been my experience with all the batteries/ just would like to know when I have charged them enough there is no automatic cut off on my charge for nimh. I think 39v at rest and I will stop. The most after an overnight rest so far is 38.7