Evaluation of a 36V lead-acid battery charger

[TheAmmoniacal]

I have a 36V motor on my bicycle that I power by three 12V lead-acid batteries wired in series, which I've been rewiring in parallel every time I charge it. But I want to make a "sealed" battery package which I could use in the rain and would plug into a charger without rewiring. (Of course it's not completely sealed, gassing etc)

So I was looking for a 36V charger that would let me charge the batteries in series, although not optimal I'll give it a shot. I came across this cheap one.http://www.ebay.co.uk/itm/131311730942

Despite all the overhyped sales-terms, is it any good? Safe?

Main board:
Main board traces/underside:
MCU board:

MCU diagram: https://dl.dropboxusercontent.com/u/15526481/36vcharg/diagram.JPG
MCU spec sheet: https://dl.dropboxusercontent.com/u/15526481/36vcharg/SH79F081A%20CV1.0.pdf

If you have other information on series-charging lead-acids, feel free to share

[macboy]

I had a similar problem with a 24 V lawn mower battery, which is 2 x 12 V in series. I hated charging in series. This battery pack happens to use an IEC socket as a connector(!), and only used the outer two poles of the connector. I connected the third pole to the center tap so that I could plug in my custom charger* and charge the two batteries separately.

If you bring out the two intermediate connections, then you can do the same and charge the three batteries separately (not in parallel). You can use three 12V chargers, provided that their outputs are floating, i.e. transformer isolated and not grounded.

*my "custom charger" is simply a dual output lab power supply with each output set to 13.8 V and 2.0 A. Occassionally I do a top-up charge to 14.4 V but only when I know I will be around to manually stop it (set back to 13.8 V) at the appropriate time. Otherwise, it is set-and-forget.

[bktemp]

At first the boards looks good, but looking at some details I would not trust it:
- The fan cable going from the secondary side through a hole on the primary side is a really bad design: It can easily make contact with some pins on the primary side if they punch the insulation.
- The mains fuse looks a bit small.

[sunnyhighway]

- The fan cable going from the secondary side through a hole on the primary side is a really bad design

Would't say the design is bad. I'm more inclined to think the folks responsible for component sourcing and/or assembly were trying to save 2 cents on connectors for the fan cable.