Electric Bikes - Astro "Blinky" Battery Balancer

I just bought an Astro Battery balancer board from a local RC model airplane store yesterday.
You are supposed to be able to leave it plugged into your lithium battery pack, and it will relentlessly balance your batteries before charging, during charging, and after charging. It can also discharge any battery cell that is overcharged beyond 4.25Volts

you can find a full description of the product here:
http://www.astroflight.com/index.php?main_page=product_info&cPath=34&products_id=20


BTW, this board cost me $36 cdn

Anyways, I have a YW lithium battery pack that I started to test last night.

Here are the results of my test so far:

Before
Blue 0V ( this is my ground reference)
Green 3.997V (cell 1)
Yellow 4.022V (cell 2)
Orange 3.961V (cell 3)
Red 3.961V (cell 4)
Brown 3.964V (cell 5)

- plugged in the balancer at 8:20pm (24 Apr2009)


the next day(25 Apr2009) at 10am:
blue 0V
green 3.960V
yellow 3.972V
orange 3.954V
red 3.942V
brown 3.953V

The blinky is supposed to stop blinking when the cells are balanced. at 11am ( the time that I am writing this) they are still blinking.

Update:
25 Apr 2009 3:50pm
- the board is no long blinking when I checked it, ie I don't know exactly when the board finished

blue 0V
green 3.957V
yellow 3.950V
orange 3.953V
red 3.939V
brown 3.949V

Not bad! that looks like a 10mV acuracy in less than 24hours.

I'm going to put my yardworks batteries back into use. I'll use the existing BMS boards while charging and discharging, but I'll cycle this balancing board through the battery packs so each battery gets balanced every 3 or 4 day. If I get good results, I'll pick up a few more of these 'blinkys'

Second Battery test:

blue 0V
green 4.048V
yellow 4.042V
orange 4.042V
red 4.044V
brown 4.042V

- plugged in the balancing board at 4:01pm 25Apr2009 and it started to blink right away

- IMO, this battery is already well balanced, so I'm interested if the blinky is going to screw it up before it stops blinking.

4:03pm 25 Apr 2009

- within a few minutes of plugging the board in, the blinking stopped for close to 30 seconds, and now its blinking a little bit here and there. looks like a good sign.

I am going to turn my back on this thing for a few hours, and see what happens.

Update:
Second Battery 25 Apr 2009 9:43 PM
- approximately 5.75 hours connected to a battery that was - imo - NOT in need of balancing.

blue 0V
green 4.043V
yellow 4.036V
orange 4.041V
red 4.031V
brown 4.037V

Hmm....that's a shame. Although its still balanced within about 10mV, the Blinky board actually screwed up a perfectly balanced battery pack.

for curiosity sake, I am going to let this battery go all night to see what happens...

Test results for second battery:
12noon on 26Apr2009

blue 0V
green 4.032V
yellow 4.028V
orange 4.032V
red 4.020V
brown 4.031V

It definitely seems like I would not want to leave this board plugged into a battery that is in storage because it was a way of slowly discharging the cells. However, the discharge is so subtle it would not be a problem with a battery that is actively being used on my bike.

BTW, I put this board under the microscope to see how easy it would be to clone.

The circuit board is extremely simple, and the board uses a MicroChip PIC16c770 with very little of anything else.

I have a programmers card for PIC microcontrollers but unfortunately its not compatible with the PIC16c770

I've been using these for my LiPoly e-bike for a while now. However, they're kinda slow so I just simply use a balanced charger.

Thats a good idea. I've only bought one of these boards so far. If I buy another 3 to match with my batteries, I might even save some money if I buy a balanced charger instead.

One thing is for certain, I have to continue to look into this over the next few weeks. I'll be happy to post updates so the thread stands as a record for anyone searching the topic.