Question about nimh batteries on ebay

[hochdorf]

http://cgi.ebay.com/6-x-C-Size-9500mAh-NiMH-Rechargeable-Battery-Ultracell-/270751582587?pt=US_Batteries&hash=item3f0a0d497b
Energy density 190 wh/kg.
Price 245 dollars per kw/h only.
It is true? Seller has 99.4% Positive feedback.
Wikipedia says that nimh's maximum energy density is 100 W·h/kg only.

 

[skeetab5780]

arent those just like regular alkaline batteries, but just a rechargeable version? they probably have awful discharge rates and the tabs are tiny. i think these cells are meant for boombox radios kids toys and small portable electronics from back in the day. i remember i had this old school general electric tape recorder when i was a kid and it would eat thru 6 of these batteries in a day! i wish i had a set of these rechargeable ones

 

[hochdorf]

I need battery for ebike.
30 of them can connect in series for 36v.
I want to know is so big energy density true or seller lies?

 

[Ypedal]

Seller lies...

A good high quality D cell can do 8ah, no way is that happening in C size..

Then we get into the discharge ability, unless you want to run a 250w motor ( and i'm being generous ) , forget these cells !

 

[hochdorf]

they probably have awful discharge rates

recommended discharge rate for nimh is 0.5c.
If i buy 60 of them = 684 w/h.
0.5c is 342 w. It is not little for ebike.

 

[hochdorf]

Seller lies...

But why he has 99.4% Positive feedback?

 

[Ypedal]

Seller lies...

But why he has 99.4% Positive feedback?

Because 99.4% of people who buy them have no equipment or know how to test them..

Flashlights and ebikes... not the same !!!

 

[Hillhater]

Only way to satisfy yourself is to buy a few ( 6) and test their discharge rate, before you by the full set of 60. :wink:

 

[deardancer3]

energy density is different than power.

most ebikes will need 350watts power or about 10 amps at 36 volts. and peak power of at least 5oo watts.

Ask the guy if the cells can deliver and hold 10 amps without significant voltage sag?

I really doubt it. especially with button tabs, not solder/welded ribbons.

also find your return shipping charges, signiture guarraanteed.


you could order three of these packs and put them in parrallel, might have a chance and you would have almost 30amp hours.

d

 

[icecube57]

Imma tell you once. I had some Tenergy Sub C High Discharge cells. They arent much smaller than C. These were only 4200mah but I only got 60% of the capacity at best. The cells were rated for 40A. I tried discharging them at 40A and it was voltage sag city. It took 4 cells in parallel to have a stiff enough voltage to be usable. The supposed 16.8ah I had was only good about 9AH at 40A until I had to reduce the discharge load so much until the pack finally gave out at a little over 11ah at 1A load. Even at a 1A discharge i couldnt get full AH. So dont go through with this... you will have a nice paper weight.

 

[hochdorf]

energy density is different than power.

I know. But nimh can give 0.5c continuously and 1-2c short time.
If my ebike need 200 watts then i use 400 w/h nimh battery pack.
Does nimh batteries need balancing if i use them in series?
Can i charge them in series of 10 (= 6 chargers fo 60 pieces) pieces?
I will buy them if i can charge them in series of 10 pieces without need for balancing.

Imma tell you once. I had some Tenergy Sub C High Discharge cells. They arent much smaller than C. These were only 4200mah but I only got 60% of the capacity at best.

If this seller lies 1,66 times too (100/60=1.66) then their energy density is 114 watts/hour only.
It is worse then lipo.
I can offer 1 piece and check it, but delivery time is about 3 weeks. And i need power analyzer

 

[icecube57]

Please just dont do this. You will be wasing your money. For the money you are going to spend on this shit you could have 2 to 3 bricks of lipo.

 

[icecube57]

Read this... this will be exactly what you will experience this is my review of ebay/cheap nimh.
https://endless-sphere.com/forums/viewtopic.php?f=14&t=10756&start=0&hilit=tenergy#p164609

 

[hochdorf]

For the money you are going to spend on this shit you could have 2 to 3 bricks of lipo.

Where i can buy from lipos with best price/quality ratio?
Does hobbyking's turnigy and zippy batteries have good price/quality ratio compared to other battery shops?

 

[icecube57]

Welcome to the forum but before you ask one more question I want you to read through this thread. http://endless-sphere.com/forums/viewtopic.php?f=14&t=26621 And if you have any questions use search... there is over 5 years of info here. If you cant find it in search im pretty sure your answer is on the first or second page in the related forum section. If you have exausted all of the above then post a thread.