# Backup power supply hack



## O'Zeeke (Mar 9, 2008)

JRP3 said:


> I thought some might be interested in this. I picked up a used APC 2200 UPS without batteries and hooked the battery inputs up to my 48 volt battery pack in the AMPhibian. I now have a portable 120 volt power supply with 1600 watt capacity, I was able to run my Makita electric chainsaw off it as a test tonight.  Not sure for how long, but I should be able to drive into the woods, cut a tree into log lengths, and drag them home, all on electricity


Cool JRP3, Ive got a couple of those laying around with dead batteries that i was just about to toss, (maybe you can cut down a Christmas tree while youre at it)


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## booksix (Aug 26, 2008)

Interesting. I was just about to pick a few of these up for free and see if I could get any good batteries out of them.


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## JRP3 (Mar 7, 2008)

Usually the first thing to go on these things are the batteries, and if they are giving them away I'd imagine that's what's wrong with them. Seems as if there are a lot of good electronics in them if you know what you're doing, caps, transformers, etc. At the very least you get a 48 volt battery charger of some sort and a 48 VDC to 120 VAC converter.


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## booksix (Aug 26, 2008)

I was thinking that too. He was originally selling them (i think they are working) and said he'd give them away free to help me out. Figured it can't hurt to check it out.


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## dtbaker (Jan 5, 2008)

what would have to be done to pull from a 96v battery pack? I poked around for a little and it seems that most of the dc->120vac invertors are for 48v. Is there a reasonably easy way to hack two 48v invertors into one that would handle 96v?


In case of power outage, it would be cool to use my car battery pack as temp power supply for essentials thru the night if need be. Daytime all I would need is enough juice to 'energize' the house once I disconnect from grid. My PV invertor would fire back up once it sees line voltage and allow the PV panels to come back online, which is more than enough to run my house and recharge the car batteries on a sunny day. This would kinda be like an optional off-grid deal...


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## major (Apr 4, 2008)

dtbaker said:


> what would have to be done to pull from a 96v battery pack? I poked around for a little and it seems that most of the dc->120vac invertors are for 48v. Is there a reasonably easy way to hack two 48v invertors into one that would handle 96v?


Hi dt,

It would be difficult, to say the least, to wire up 48 volt DC UPS units to run from 96 VDC. It would be easier to take your 96 V EV pack and wire in provisions to switch them to series/parallel and run the UPS at 48 VDC. You could just use half the 96 V pack, but then you'd have different SOC and trouble charging if using a 96 V charger. Using a S/P set-up should discharge them equally. Simply switch back to series for the recharge.

I've got several 48 V UPS units. Pretty neat. 3.1 and 4.3 KVA units that sold new for like $2 or 3,000. Paid like $50 to 100 each. One was never used. Just stored in a hospital basement for like 3 years. Yeah, the batteries were toast. But the inverters work great. I don't like the chargers that are built in the UPS units. Just a couple amps. The UPS units I have use a heavy transformer and open frame enclosures. Otherwise, I'd mount them right in the EV.

Regards,

major


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