# [EVDL] I build a low cost battery tester - yeah!



## EVDL List (Jul 27, 2007)

So I revised my first significant circuit board slightly and wrote some
software and am now testing my a123 batteries to find 16 to repair 2SSIC.

It is working well. The alligator clip attached is hooked up to a buzzer so
that I know when it is time to put the next batteries in.

It charges the batteries to set, stabilized voltage, discharges them
measuring time and current, and then recharges them. Takes about 3 hours
per set right now (1c charge discharge rate).

Screen has a counter telling me everything is working, current voltages of
all the batteries, and when finished amp hours (with 2 implied decimal
places) and time to discharge for each battery.

It is giving me predicted results, which is to say the batteries that have
like 2 cycles on them are showing a little over 2.3 amp hours and the
batteries pulled from car are showing a little over 1.8 amp hours. So 4
years of abuse = 78% original capacity.

I'm thinking about building a mark 2 version of the tester, make not almost
entirely out of parts I have laying around. Something nice looking, much
faster on switches, and producible. I've designed it to be very cheap and
I'm wondering anyone else wants them. 

With a kind of cool acrylic case, small display, button, USB connector with
virtual serial port I think I could sell a 4 cell unit for $75 or a 8 cell
for $125 plus cost of charging 5-6 volt supply if you don't have one. 

I could also write software to do cycle tests and give you average, min, and
max pretty easily. The case would hold 18650's, and 26650's and I could put
something on to connect other batteries to it. The hardware software would
be able to charge from 1- 4.4 volts, discharge to .25-4.3 volts.

I have a lot of batteries to go through (all of the batteries from the
GreenT that survived being sprayed with water based fire extinguishers), So
I'm going to be building a second one. I'm just thinking about how much
effort to put into it 

More pictures at http://picasaweb.google.com/SSIRacing/BatteryTester

Michael "KD" "TRex"
Not posting enough,
Not racing enough,
www.SSI-Racing.com

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

For smaller cells like A123 there is some pretty good off the shelf RC chargers with capacity testing built in. I purchased a Superbrain 989 a few years ago, and I think it does all the same things you just described. http://www.modelrectifier.com/search/product-view.asp?ID=6863
It does have some limits that don't work as well for higher capacity cells, and even though it claims a 10 amp discharge rate in the testing that I used it for which was 6 cell nimh sticks out of a Honda Insight it seemed to derate back to about 6 amp discharges. Higher voltages would probably cut back even more as it probably can't shed the heat fast enough.
damon
> From: [email protected]
> To: [email protected]
> Date: Sun, 8 Jul 2012 12:38:20 -0700
> Subject: [EVDL] I build a low cost battery tester - yeah!
> 
> So I revised my first significant circuit board slightly and wrote some
> software and am now testing my a123 batteries to find 16 to repair 2SSIC.
> 
> It is working well. The alligator clip attached is hooked up to a buzzer so
> that I know when it is time to put the next batteries in.
> 
> It charges the batteries to set, stabilized voltage, discharges them
> measuring time and current, and then recharges them. Takes about 3 hours
> per set right now (1c charge discharge rate).
> 
> Screen has a counter telling me everything is working, current voltages of
> all the batteries, and when finished amp hours (with 2 implied decimal
> places) and time to discharge for each battery.
> 
> It is giving me predicted results, which is to say the batteries that have
> like 2 cycles on them are showing a little over 2.3 amp hours and the
> batteries pulled from car are showing a little over 1.8 amp hours. So 4
> years of abuse = 78% original capacity.
> 
> I'm thinking about building a mark 2 version of the tester, make not almost
> entirely out of parts I have laying around. Something nice looking, much
> faster on switches, and producible. I've designed it to be very cheap and
> I'm wondering anyone else wants them. 
> 
> With a kind of cool acrylic case, small display, button, USB connector with
> virtual serial port I think I could sell a 4 cell unit for $75 or a 8 cell
> for $125 plus cost of charging 5-6 volt supply if you don't have one. 
> 
> I could also write software to do cycle tests and give you average, min, and
> max pretty easily. The case would hold 18650's, and 26650's and I could put
> something on to connect other batteries to it. The hardware software would
> be able to charge from 1- 4.4 volts, discharge to .25-4.3 volts.
> 
> I have a lot of batteries to go through (all of the batteries from the
> GreenT that survived being sprayed with water based fire extinguishers), So
> I'm going to be building a second one. I'm just thinking about how much
> effort to put into it 
> 
> More pictures at http://picasaweb.google.com/SSIRacing/BatteryTester
> 
> Michael "KD" "TRex"
> Not posting enough,
> Not racing enough,
> www.SSI-Racing.com
> 
> _______________________________________________
> | Moratorium on drag racing discussion is in effect.
> | Please take those discussions elsewhere. Thanks.
> |
> | REPLYING: address your message to [email protected] only.
> | Multiple-address or CCed messages may be rejected.
> | UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> | OTHER HELP: http://evdl.org/help/
> | CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.sjsu.edu/mailman/private/ev/attachments/20120709/c9c5371c/attachment.html 
_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev


----------

