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Battery charger help Answered

As some of you may already know, I'm planning on building an electric car this summer. Its all planned out, but instead of using regular transformer based chargers I was wondering if someone could help me design a transistor based charger to reduce weight. Requirements 48 or 72 volts Needs to charge marine deep cycle batteries over night Needs to not have a transformer. Needs to be relatively small (under 1 cubic foot) Needs to be simple enough for me to build myself (I can do it if you can design it) Can anyone give me some links or some good schematics for this? Thanks


I'd charge the batteries in parallel off a computer PSU Or hack the PSU to add higher volt output Or just charge the batteries with pulsed 240 V DC thru resistor (wont be nice if something fails but the most lightweight solution ever)

Yeah, thats what I was thinking, except off of 120. I was also considering a PSU for each individual battery

You dont need PSU for each battery. They output some 10 A on the 12 V wire and maybe more if you improve cooling in the PSU I am looking now at the circuit board of a PSU like this It looks like if you connect a 4 diode bridge from the 2 12 V outputs on the large transformer you can get 24 V DC (with some relation to earth - not floating) Max current on 24 V with good diodes is 1/2 what you could get on 12 V

Yes I would, I need huge amounts of current if I want to drive it and fully recharge it every night.

I got a capacity charger for my EV. It has 3 large capacitors, a timer, and a multimiter. Paid $165.00 w/shipping. Got it from Nile Cole at evvolks.com. It charges my 90 volts system.

Battery chargers aren't really all that big or heavy, particularly if you're only charging a small 72V pack. I would recommend just buying a used 72V battery charger, as building your own charger will take up a lot of time that you could be spending modifying the car. Is that a Honda CRX?

I was thinking of individually charging the batteries, but your suggestion might also work. Yes, its a 86 crx (the most efficient model, forgot the name)

And why are you bothering hybridizing an '86 CRX? They already get better gas mileage than a Prius.

Prius is the biggest fake ever. I'm doing more of a plug in hybrid. The batteries aren't charged by the engine. I just want to have an electric and still be able to go to Albuquerque or Los Alamos or some other place farther than 20 miles. Actually, I might make it charged by the engine once I finish it.... If I was buying a new car I'd buy a VW golf TDI. 48 mpg!

Prius is the biggest fake ever.

It is not. The Chevy Volt is the biggest fake ever. You can go out right now and buy a brand-new, working Prius.

True, true. Let me rephrase that. I hate the prius. I hate chevy. Volt is a lie.

They did not! They had plans to enter full mass production! They only stopped due to lack of consumer interest!

Even though every car they made available for lease was taken, and everyone who leased one tried to buy it to save it from the crusher...

Oh my god, the balls! "Only 800 people were willing to lease the EV1". Bull. They had thousands upon thousands of people offering to buy them outright. Spin I can understand, but why stick their fingers in their ears and lie outright about how much interest there was in the EV1?

. Would you have anything close to the required voltage if you used half-wave rectification + filtering? If too low, could you use a DC-DC booster? . . Why are you so adamant about not using a transformer? If nothing else, they can improve safety. . I'm with guyfrom7up, something computer-PSUish would probably be your best bet. I've seen 1KW+ units advertised for computers, so they can be pretty compact and reasonably lightweight.

Yes, that would probably work. The reason I don't want a transformer is because of the weight. I'll be charging either 4 or 6 deep cycle batteries, and battery charges are heavy. I'll look into those computer ones. Any recommendations or schematics?

doh! Why didn't I do that! Yeah, I suppose I should wait until later for anything fancy

. BTW, if your weight obsession is because you will be mounting the PS/charger onboard, I'd suggest using the cheapest thing you can come up, regardless of weight/size. Use that "outboard" until you get past the proof-of-concept stage. Worry about mounting a light-as-possible unit onboard, later.

Please keep me updated on this project. I have a couple of vehicles that are good candidates for an electric conversion, and two pretty smart kids with too much time on their hands. Have you considered a hybrid project?

I'll definitely make an instructable for this project. Actually I am making it hybrid. I'm leaving the front untouched and adding an axle and differential in the back and having the motor in the trunk. Keep me posted if you make one

WIll do. I have considered that route. I also considered an add on electric drive-trailer.

Is that your grain truck in the background?

Do you want it to be yours? Let me check my wallet...

you could use a switch-mode powersupply, it still has a transformer, but it's a fraction of the size and weight of a normal transformer. PC power supplies are of that type.

Hmm, links don't seem to be working for me. Try googling transistor charger, and click the second link.

Thanks, it worked fine for me. This is a really good charger, but I was wondering if there is any way to eliminate the transformer Thank you so much!

look at the electric crotch rocket Instructable, thats about all i can do to help, good luck, it sucks they took away all those Saturn EV1's