Every good battery needs a charger. As you may have noticed, I'm building a new charger at the same time.
Although I am using a 72V battery on my bike now, I'm setting up the charger and new battery to use 36V section. Each section is two 10AH 36V modules in parallel. This allows me to use the battery with my other bike (36V) or on my friend's bike (36V) or to charge my friend's bike. I have my 72V battery already set up so that I can use a 72V, or two 36V in series, chargers. I know, this is extra complexity, but really not that much. I like modular design.
So this power supply, as I posted earlier, uses four mean-well power supplies, open frame USP-225-24's. Two of these in series can be adjusted to produce 41 volts, just right for topping off a 12S LiFEPO4 or a 10S 18650. This works out handy, as I'll be running both chemistries for a while until the LiFEPO4's get tired. I wont run two chemistries in parallel, I'll switch between them using Anderson plugs. The old LiFEPO4's have lost 10% capacity already, which is why I'm building a new battery in the first place.
USP-225-24's are rated 225 watts each, have a wide input range of 90 to 305 VAC 50 or 60 hz. Later I may set these up to use 220, and hack things so I can charge from a car charging station, which could get me out of a jam. The power supplies are 9.4 amp max.
One problem with Mean-wells is inrush current. These supplies can pull 15 amps inrush current each, four could pull 60A briefly. Will that blow a 20A breaker? Don't want to find out when I'm out begging for a charge. I've added a switch that puts two 5 ohm 5 watt resistors in series witht he Mean Well input leads, then can be switched to connect them straight to the power lines. I can switch it to charge, which brings the output up to proper voltage in a couple of seconds, then switch to straight through for actual use. The switch on the front is not on-off, but on-charge.
I got some 24V ball bearing fans at Jameco, ball bearing being long-lasting and quiet, 24V to match my power supplies. They run fine on reduced voltage, a little less airflow. These are hooked up to opne of the supplies, running whenever the unit is plugged in.
I used a standard computer three-pin AC socket, like is used in the back of your computer, to allow quick changing from 120 to 240 if I choose to do so in the future. A little ammeter/voltmeter/power meter measures one of the 36V outputs (I was too cheap to buy two, one tells me what I need to know) and used some gland fittings as strain reliefs for the wire. Two three-pin mic jacks are the output cable, compatible with many commercial batteries, all my bikes are standardized on these as charging plugs.
I considered briefly building it watertight, but balked at the cost of Mean Well waterproof power supplies. This open frame supply can run without fans, but not at full power. The unit is not waterproof, a consideration when charging on the road, but usually a solvable problem.
Here is the voltmeter - 0-100V, 20A, internal shunt. Although it states that it saved energy measurement between uses, mine doesn't, which is just fine as I want to know how much energy I put in for each charge. Energy Meter
Next post a few pics.