4500 mah SC Cells

Johnbear

10 kW
Joined
Jun 7, 2007
Messages
521
Location
Vancouver BC
TECHNICAL SEPCIFICATION

Dimension: Height 43 mm, Diameter 23 mm
Weight: 57g
Capacity: 4500 mAh
Voltage: 1.2V
Standard Charge: 15 hours @ 300 mA
Rapid Charge: 2 hours @ 3000 mA


30 cells at 57.g is 1.71 kg

90 cells 13.5 ah 5.130 kg (11 lbs)

Has anyone tried these cells. Seems to good to be true. http://cgi.ebay.ca/12-Pcs-of-Matched-Sub-C-4500mAh-NiMH-Battery-with-Tabs_W0QQitemZ330161139031QQihZ014QQcategoryZ34063QQtcZphotoQQcmdZViewItem
 
I'm using their C size 10AH cells. Here's my review:

http://endless-sphere.com/forums/viewtopic.php?t=1920&highlight=

I think for ebike C size cells barely cut it, and Sc would be worse. You'll have horrible performance if you draw more than 5 amps out of it in 1P config, and running NimH batteries in parallel is a pain. You need to have multiple chargers for that.

If I was starting a pack build now I'd go with a123. Expensive, but there's nothing else that works acceptably in my opinion.
 
I hear you man. I'm weary of out of the norm ratings too even if its from an established reputable company. They can make mistakes, and so can their suppliers.

If I did any kind of button top cell like a D, theres no way I'd do anything else but the stacked in PVC strapped to the frame thing, with the spring. Man, that'd be awesome. Whats the C rating of those D cells anyhow?
 
Ah, I didn't notice 40A rating. They don't publish ratings for D cells. They rate their F cells as 3C.

Sc batteries are used for tool packs that must be high drain, so I guess these cells are the high drain variety.

Still, if you draw 40 amps out of 4.5Ah cells, they'll be dead in 6 (more likely in 4) minutes.
 
I'm weary of the C size with a 40 amp drain. The F size cells can barely handle that, I don't see the C size living very long doing a 40a drain of them.
 
Sub C are some of the most high drain NiMH cells available. Like you said they are used for power tools and in the RC market. They can achieve high current due to low internal resistance so it is not exacly bad for them to be run a high current. Most of the C and D sized cells are rated for lower because they are usually only need in low drain device like flashlights and boom boxes.
 
im going to chime in with others here - using sub-c cells for a pack is a bit of a waste. You want larger cells. Sure they're high discharge,but their overall capacity is still low, you might also want to compare their capacity vs weight. smaller cells will have more protective surface area therefore have more weight for a given size pack.
 
I've been real disappointed with the performance of the larger sized Ni-xx batteries. If they were properly designed, I don't see any reason the larger capacity cells couldn't match the discharge C rates of the smaller cells, but the ones commonly available don't come close.

I'm sure performance varies with manufacturer and specific model.

To utilize the smaller cells, you'd really need to run several strings in parallel. If you had 3 or 4 parallel strings of these, the discharge rate of each string would be divided by the number of strings, so they could stay in the 'happy' range.

You would need to separate the strings and charge them separately. This could be done with a large multi-pin connector. You could use multiple chargers to charge all strings at the same time. The connector on the controller side could have jumpers to put the strings back in parallel for discharge. This could be done with switches or relays too.
 
Some of you will know I have tested a whole bunch of cells - to this day I am still using SC3700's - and for a reason.

They will do 30A individually and still deliver 3600mah+ back.

They have also stood the test of time - now with well in excess of 500 cycles - I stopped counting long ago!

As a rule D cells are just to big for high currents - they overheat too quickly.

As previously mentioned, there has been a lot of developement of SC sizes for the RC market where amp dumping is so important - but so is finishing the race!

However, not all SC are created equal.

I have tested 3500mah cells that don't ever do more than 2600mah
I have tested many 3000+ cells that only get close to that at .5C or less

I have never seen a pre-built (bike) pack made from good high discharge cells.

For comparison - one of my packs weighs 5.4KG - delivers 48V 7400mah at any rate up to 60A - continuously.

Not having seen any test data showing the 10AH D cells at more than 2C - and that after asking (the manufacturer and dealer) for the data, I'm not convinced they perform well at all. Anyone have graphs for any D cells at more than 2C??????????????????

Scott
 
I run this 1400 scr nicad pack for fun every once in awhile. I know I'm pulling at least 12 amps at 24-25 mph if not more so that would be like 8c. It good for about 2 miles.
 
Pro peak charger - charges up to 20 cells at 4A.

The pack is wired to a 4 way connector - with the centre taps being plus and minus of opposite packs - so shorted when its plugged into a bike.

It does mean they are charged in parallel - I used to check them every 10 cycles - then 50 or so. They were last checked 100+ ago. I did not see any real differences in the first 300 or so cycles so I am pretty relaxed about them.

I did have 2 cells short on the end of a pack (case to case) very early on (due to insulation rubbing through). Was obvious due to the cell heating.

Scott
 
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