Just ran into this thread,
great work guys, and I can really appreciate the fun of rolling your own.
I have been playing with grid chargers for hybrid battery packs lately and have come up with a modular approach that has a lot of possibilities.
We all have seen the small efficient switcher power supplies from China.
I got some isolated universal input 48V units that will run from 85-250 VAC.
They are short circuit and over temp protected with 1500V isolation. They are available with a wide range of output currents.
With the gradual appearance of high power LEDS, another type of high efficiency power supplys have started to show up. The LED power supplies have true constant current outputs and will adjust the output voltage to maintain the current from 3-48V.
By putting the isolated 48V switchers in series, one can get any base voltage that you want. Add an isolated constant current LED supply to the series string, and you have an adjustable max constant voltage(the 48V switchers can each be adjusted to between 40-54V output) And a constant current range of ~40V.
The LED supplies can be paralleled and will share load perfectly throughout the 40V CC range.
I started with a 350ma combination for charging my honda Insight 144V batteries, ( Schematic
http://www.99mpg.com/Data/resources/...balancer_2.pdf) and will be finishing a dual rate system that will output a bit over 1 A. The dual rate system has bypass diodes on the four 48V supplies, and the supplies can be turned on or off in any combination. This yields a constant current charger that can charge a battery anywhere between 7.2V to 256V, with a limit that is only limited by the 1500V isolation.
The led and switchers to make this supply were just a bit over $120 total.
Bigger 48V supplies with paralleled LED constant current supplies, and you can pretty much build any charger you want with well designed and protected off the shelf building blocks.
Some photos and the information is here, about half way down the page:
MIMA Pack Whack and rebalancing the battery - MIMA Honda Insight Modified Integrated Motor Assist
A simple max voltage detect,circuit will allow the 700ma to be shut off when nearly finished with the charge, which will drop the output current to a safe constant 350ma trickle charge which will safely top off the pack.