Ebikes.ca 18Ah pack tests out at 19.55Ah.

Lowell · Apr 6, 2007

Now here's something you don't see every day... batteries that exceed their advertised capacity! I put one of my 24v 18Ah packs on a CBA II, and using a 0.9v/cell cutoff voltage it tested out at 19.44Ah on a 0.2c discharge. (unfortunately the CBA II only dissipates 100W) This pack has been used pretty hard for 15 cycles so far.

During discharge all 20 cells showed no more than 0.002v variation, and after full discharge only 0.019v variation.

EDIT: Using a 1.0v/cell cutoff capacity checks in around 19.3Ah for the picky

D-Man · Apr 6, 2007

Thats pretty good. Maybe the packs and others are under-rated for a reason.

So how many battery packs to you have on that bike now? Are they all the same or is it mixed?

Lowell · Apr 6, 2007

D-Man said:
Thats pretty good. Maybe the packs and others are under-rated for a reason.

So how many battery packs to you have on that bike now? Are they all the same or is it mixed?

Battery ratings seem to vary a lot depending on manufacturer. Perhaps the worst offenders are some of the NiMH AA cells. I don't really know what is normal for the larger cells, but it's good to know I can pull 15.5Ah out of these cells and still only be at 80% DOD.

The setup I've been running to date is a pair of 24v 18Ah and a 36v 18Ah all in series for 84v. In series with that is a 2s lipo booster pack of 7.4v.

Matt Gruber · Apr 6, 2007

Nice try, but i use cruising amps (15a) for reaL world tests.
they always read higher at low drain

Lowell · Apr 7, 2007

Matt Gruber said:
Nice try, but i use cruising amps (15a) for reaL world tests.
they always read higher at low drain

Like I said, the CBA II will only sink 100W. Low C discharge ratings are standard in the industry... show me a manufacturer who advertises their cell capacity at 15A discharge. They might include it in the spec sheet, but the cell will be named at a more favorable C rate. A GP330SCH has a capacity of 3300mAh "when discharged at 660mA to 1.0V at 20 deg C". This cell will go 5 hours at 0.2C and 29 minutes at 2C.

http://www.batteryspace.com/productimages/nimh-cell/MH-D10000.pdf

Note that they rate theirs at the same 0.2c discharge that I tested the Ebikes.ca pack at.

http://candlepowerforums.com/vb/showthread.php?t=79302

Good NiMH batteries don't drop much in capacity up to 2c+. For example the Energizer 2500 cells I use in my 1W LED lamp lose maybe 250mAH between 0.2c and 2c.

Lead bricks on the other hand drop capacity like boat anchors if you even draw 1c out of them. Perhaps that's your confusion.

http://www.batteryuniversity.com/partone-16a.htm

Lowell · Apr 7, 2007

Matt Gruber said:
Nice try, but i use cruising amps (15a) for reaL world tests.
they always read higher at low drain

Btw, how many amp hours do you get at 15A compared to the rated capacity marked on the packs?

Reid Welch · Apr 7, 2007

:wink:

Score one for Lowell!

grrrrr/ouch!

I like Matt's reality checks too.

Lowell · Apr 7, 2007

Reid Welch said:
:wink:

Score one for Lowell!

grrrrr/ouch!

I like Matt's reality checks too.

Just the facts. The test was run at 0.2C and about 20 celcius which I understand is an IEC standard. In no way did I attempt to misrepresent the product, and the test speaks volumes for the quality control Justin does on each pack before it goes out the door. As one member recently discovered with a lithium pack, some companies will ship you packs that have never been analyzed.

Reid Welch · Apr 7, 2007

Lowell said:
As one member recently discovered with a lithium pack,
some companies will ship you packs that have never been analyzed.

:lol:

Tweetybird chirps, "Twue!"

:lol:

Lowell · Apr 7, 2007

Well my second 24v 18Ah pack just passed the 18Ah mark but is about half a volt down compared to the first pack.

Some info on the analyzer I borrowed:

http://www.westmountainradio.com/CBA.htm

For $110 I would say it's a must have for anyone with money invested in battery packs. As can be seen in that candlepowerforums.com battery shootout, a lot of cells don't meet advertised capacity, and some companies simply lie out their asses. I'd be a little upset if I bought AccuPower D 11.5's and they only tested 10.6-10.7 at 0.2C.

Lowell · Apr 7, 2007

2nd pack: 19.55Ah down to 1.0v/cell, 19.72Ah to 0.9v/cell!

Matt Gruber · Apr 7, 2007

dont get upset, get some halogen bulbs 10 for $3.50 cat #LP-65 also get some 5/$1 switches ISW-4 better hurry, only 41,000 left! allelectronics.com

agreed, they are fine matched cells

Lowell · Apr 7, 2007

Matt Gruber said:
dont get upset, get some halogen bulbs 10 for $3.50 cat #LP-65 also get some 5/$1 switches ISW-4 better hurry, only 41,000 left! allelectronics.com

agreed, they are fine matched cells

What do you use for an Ahr meter and low voltage cut off? I used to connect halogen bulbs to RC lipo packs but I always worried about overdischarging them, and watching batteries discharge isn't that exciting.

Matt Gruber · Apr 7, 2007

i use a stopwatch for ahr. say it runs 20min at 50a. 20/60min=.33hrx50a=16.5ah
a hi amp test goes by fast as u check each cell and write it down.
and check for hot spots!
u wont doze off w/14 bulbs @ 35 amps. it won't take long ~1/2 hr.
maybe 20a is fast enough? maybe ~45-54min. maybe a lot quicker if u stop at 1.00v

Ypedal · Apr 8, 2007

I use a DrainBrain and a bunch of 200w lightbulbs mounted to a piece of 2x4 lumber.

With 4 x 200w bulbs i get 4 amps discharge.

After one full season of hard " ab " -use i get 7.4ah before i hit 1.v per cell from 8ah cells. ( After 4 cycles over 3 days ) . curious how Nicad takes a full charge much better than nimh.. i'm liking the nicads so far.

Lowell · Apr 15, 2007

No more light bulbs and graph paper! Come back to your computer and you get this:

Matt Gruber · Apr 15, 2007

i see a curve!
can't read #'s way too small.

Lowell · Apr 15, 2007

Maybe you need a bigger monitor? Looks fine to me.

TylerDurden · Apr 15, 2007

Webbies have only TV rez. 640x480 through NTSC...

Lowell · Apr 15, 2007

TylerDurden said:
Webbies have only TV rez. 640x480 through NTSC...

Woah, didn't know that. I'll see if I can export to excel, as that pic was a screen capture.

bobmcree · Apr 25, 2007

this year i purchased 4 of the 18 Ah DD packs from Justin, and they all tested out at well over 19 Ah both on my West Mountain CBA2 at 2A and on my homebrew load tester at 10A. Real world performance is similar; at an average of 20A on my bike I discharged down to 17 Ah and had plenty of capacity left. My experience with quality NiMH cells is that there is virtually no Peukert effect. My 3800 maH GoldPeak cells provide over 4Ah@35A and this is fairly typical for matched racing packs.

Justin has always rated his cells conservatively, these same cells from Forsen, another distributor, are rated 20 Ah. One reason they may deliver lower capacity in initial testing is that they often improve after a few cycles. Another possibility is the 6 hour cutoff in the HiPower chargers. Unless you restart after a few hours a totally discharged 20 Ah pack will not get fully charged-bob

Matt Gruber · Apr 25, 2007

bob
that't great info, thanks!
i'd like to try some NiMH 2100ma AA's in my drill. But i don't use it often. How many years could it last(1 cycle/month) if i keep the pack in my fridge(39F),
or my freezer 0F
Thanks!

bobmcree · Apr 25, 2007

keep em in the freezer but in an airtight container to keep humidity out and warm them up before use. NiMH are typically good for just a few years but in the freezer can last much longer. i would expect 5 yrs or so.

-bob

Ebikes.ca 18Ah pack tests out at 19.55Ah.

100 kW

100 kW

100 kW

1 MW

100 kW

100 kW

1 MW

100 kW

1 MW

100 kW

100 kW

1 MW

100 kW

1 MW

Moderator

100 kW

1 MW

100 kW

100 GW

100 kW

10 kW

1 MW

10 kW

Similar threads