Sunday, September 4, 2011

Equalizing battery bank charger V2

The related projects:

LPH7779 Nokia display board
LTC4151 voltage and current measuring board
Mini 5V Step-down board
and the charger boards from Equalizing battery bank charger V1

came together in the V2 charger.

I chose a smaller box for this one. Screwed the PCBs to bakelite carrier boards and stacked the carrier boards on top of each other through 4 posts made from threaded rod like so:

From top to bottom we have Charging, Measurement then Power supply levels.

Charging basically just has the UC2906-based charger boards from V1
Measurement has a completely overkill ATMega16 (only thing I had at home) that drives the display, and talks the to LTC4151 Voltage and current measurement board through I2C.
Power supply has simple filter/buffers for the 3 separate charger boards and the 5v step-down for the uC and display.

Bottom level and measurement level:

Measurement level:

Power supply level:

The wiring isn't exactly pretty but whatever.

The finished charger looks like this:

I added few extra features to it in the end. The AtMega can be programmed through the DB9 connector on the back. The UART is also exposed there, and periodic measurements are printed (in case I ever want to do any charge characteristic graphs or something).

Here's the first test run on my old e-bike battery bank:

Bascom code for the measurement and display can be found here

(I'd give credit for the LPH7779 code but I don't remember where I found it)