Building a home charger?

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Jazzyrigged
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Building a home charger?

Has anyone attempted to build their own charger or controller. I've been looking at the zivan 72v charger and Alltrax controller and am just wondering if anyone out there has built their own charger or controller. I'm trying to keep my project to an affordable cost (I do social work and while emotionally rewarding, it's lacking fiscally). Any ideas or links would be very welcome.

mr_exon
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Re: Building a home charger?

I have a curtis controller that is open right now, it is a thing of pure crazyness in side, if you can make one your self my hats off to you....

it is way over my head, inside looks like somethinf out of a NASA space project, lol
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andrew
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Re: Building a home charger?

There are controller chips available from Digikey and other electronic suppliers. A light dimmer with a bridge rectifier might work for charging.

It may be easier to buy a defective controller/charger and work from there. Controllers "blow up" often and need rebuilding.
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Fechter
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Re: Building a home charger?

Do you want to build a charger for lead-acid?

I've seen some pretty beefy regulated switching power supplies from some of the surplus places.
These could be modified into a decent charger in most cases.

Old computer power supplies are pretty good too. If you can find a souce for them cheap, several of them could be put in series to get the desired voltage.

Building totally from scratch is not very cost effective these days. It's cheaper to start with junk.

Jazzyrigged
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Re: Building a home charger?

I would have never thought of using old computer power supplies. Anyone have anythought how many would be needed for a 72v system. Perhaps I just need to get off my hind quarters and tear apart some old machines. I'm wondering if it could be just 6? As always, andy ideas or comments are well appreciated.

Along those lines, I wonder about hacking up old computer UPS? May be too low of amperage to make it worth it.

reikiman
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Re: Building a home charger?

Another possibility is to get a Variac. These are, as I understand it, a variable transformer. I don't have one but a guy I know in San Francisco does, it's a biggish box with a big knob that you turn to get the desired voltage. The idea is if you know you need X volts, you twist the knob on the Variac to get that voltage. You just have to remember to disconnect it after N hours or you'll overcharge the batteries. There's no automatic shutoff circuit, the shutoff is controlled by you. And of course overcharging is not recommended for lithium batteries.

But Fetcher's thought of raiding power supplies is sure interesting. Sounds like if you want varying voltages you just string together the correct number of power supplies.

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ILBCNU
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Re: Building a home charger?

You can stack power supplies to get different voltages. The trick is the output of each power supply MUST be isolated. NEITHER of the power supplies ground or positive connections can be connected to the input of the power supply. The ground can NOT be connected to the power supply case. When I was in the Air Force and worked on radar there was a requirement for 1000-volts for the klystron tube. The power supply was designed by stacking voltages to get to 1000-volts. What they really did was build 3 smaller supplies, 250-v, 350-v, and 400-v, then stack the voltages for the 1000-volts. The other voltages were also used in different parts of the radar system, so taping into the different voltages may also be done, you just have to be sure the supply you tap into has the current capability to preform the task you want done.

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Jazzyrigged
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Re: Building a home charger?

Well I went home last night and found an old power supply still in the box. It's rated at 430 watts and the manual says it will put out 12v at 12 amps. The problem is to charge a battery you need to have 13.6v-14.2v. Does anyone know if there is a way to step up the power output on a power supply?

Fechter
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Re: Building a home charger?

As with computer power supplies, there is a voltage regulator circuit. Usually there's a way to change a resistor somewhere to trim the output voltage. Some even have a potentiometer right on the board. It would take a bit of reverse engineering to figure out how the regulator works.

tortuga0303
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Re: Building a home charger?

If you are using a 72 volt system which I am assuming is 6 12 volt cells in series, it may be way way way easier to find a way to quickly switch from a connection of the cells in series to a connection in parallel, that way you would drop the effective voltage to 12 and could use a standard charger, or several

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