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

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Lowell   1 MW

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

Post by Lowell » Apr 06 2007 9:08pm

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 :)
Last edited by Lowell on Apr 07 2007 3:50am, edited 2 times in total.

D-Man   1 MW

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Post by D-Man » Apr 06 2007 10:18pm

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   1 MW

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Post by Lowell » Apr 06 2007 10:50pm

D-Man wrote: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   100 kW

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Post by Matt Gruber » Apr 07 2007 1:56am

Nice try, but i use cruising amps (15a) for reaL world tests.
they always read higher at low drain
ASE CERTIFIED IN ELECTRICAL SYSTEMS 1984- retired
Converted window AC's to central system.
Testing various foods.
Finished testing JB Weld cell fuses. No more soldering to a bare cell for a repair.
Why build a pack from scratch? I buy tool packs instead.

Lowell   1 MW

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Post by Lowell » Apr 07 2007 2:50am

Matt Gruber wrote: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/productimag ... 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   1 MW

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Post by Lowell » Apr 07 2007 2:52am

Matt Gruber wrote: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?

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Post by Reid Welch » Apr 07 2007 2:52am

:wink:

Score one for Lowell!

grrrrr/ouch!

I like Matt's reality checks too.

Lowell   1 MW

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Post by Lowell » Apr 07 2007 3:08am

Reid Welch wrote::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.

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Reid Welch   10 MW

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Post by Reid Welch » Apr 07 2007 3:10am

Lowell wrote: 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   1 MW

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Post by Lowell » Apr 07 2007 3:35am

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   1 MW

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Post by Lowell » Apr 07 2007 3:48am

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

Matt Gruber   100 kW

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Post by Matt Gruber » Apr 07 2007 6:00am

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
ASE CERTIFIED IN ELECTRICAL SYSTEMS 1984- retired
Converted window AC's to central system.
Testing various foods.
Finished testing JB Weld cell fuses. No more soldering to a bare cell for a repair.
Why build a pack from scratch? I buy tool packs instead.

Lowell   1 MW

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Post by Lowell » Apr 07 2007 11:07am

Matt Gruber wrote: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   100 kW

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Post by Matt Gruber » Apr 07 2007 2:56pm

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
ASE CERTIFIED IN ELECTRICAL SYSTEMS 1984- retired
Converted window AC's to central system.
Testing various foods.
Finished testing JB Weld cell fuses. No more soldering to a bare cell for a repair.
Why build a pack from scratch? I buy tool packs instead.

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Ypedal   100 GW

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Post by Ypedal » Apr 08 2007 5:05pm

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.
ES site status page:
http://www.ypedal.com/ES/ES.htm
----------------
http://www.ypedal.com

Lowell   1 MW

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Post by Lowell » Apr 15 2007 10:11am

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

Image

Matt Gruber   100 kW

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Post by Matt Gruber » Apr 15 2007 10:23am

i see a curve!
can't read #'s way too small.
ASE CERTIFIED IN ELECTRICAL SYSTEMS 1984- retired
Converted window AC's to central system.
Testing various foods.
Finished testing JB Weld cell fuses. No more soldering to a bare cell for a repair.
Why build a pack from scratch? I buy tool packs instead.

Lowell   1 MW

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Post by Lowell » Apr 15 2007 11:05am

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

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TylerDurden   100 GW

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Post by TylerDurden » Apr 15 2007 11:22am

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

:(
Have a Nice Day,

TD

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Lowell   1 MW

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Post by Lowell » Apr 15 2007 11:30am

TylerDurden wrote: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   10 kW

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Post by bobmcree » Apr 25 2007 11:45am

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

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Post by Matt Gruber » Apr 25 2007 12:02pm

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!
ASE CERTIFIED IN ELECTRICAL SYSTEMS 1984- retired
Converted window AC's to central system.
Testing various foods.
Finished testing JB Weld cell fuses. No more soldering to a bare cell for a repair.
Why build a pack from scratch? I buy tool packs instead.

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Post by bobmcree » Apr 25 2007 12:25pm

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

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