soulmata turns 7AH ups into 80AH ups

[soulmata]

I hate most everybody here, but I figure for those DIY crowd, you might like this:

http://www.youtube.com/watch?v=HluzeHRjsLU

I essentially just replaced the stock batteries on a small home/office UPS with 2 gigantic deep cycle marine batteries


Normally when people do this they are using higher quality UPS, like APC brand. This piece of shit was $75 including shipping. It works OK, but the stock battery capacity got me maybe 2-3 minute if the power went out. With this I'll get well over an hour, probably even over 2 hours depending on current load


Next time I am going to put a 30A fuse close to the batteries. I calculated a peak continuous current of around 20A, which is also the suggested load for 10Ga wire, so I figure 30A will be more than enough. I have planned to remove the piezo buzzer next time as well.

[Gil_Hamilton]

I hate most everybody here...

Then we're doing something right!

[PHoNyMiKe]

I haven't bought a UPS in years but last time I got a nice APC for like $30 on sale at compusa. it lasts me a good two minutes or so with 1 pc and 15" lcd.

the only problem I see here is the charging circuit. your amateur wiring skills are on par with car audio. most heavy duty car audio setups use at least 1,000 watts on average (1,000watts / 12volts = 83 amps,) and peak at say 2,000 watts (166 amps.) in large setups like this, people often install several batteries in their vehicle, but keep them on a separate circuit independent of the alternator charging circuit. hook a bunch of batteries to your alternator and it will burn out real quick because it wasn't designed to charge that many batteries. so I would say the charging circuit in your pos ups, is not meant to handle those larger batteries, and as they charge, they will suck power through the charging circuit and burn it out.

as for a fuse yeah, say you dropped a free weight onto the wires, cut through the insulation and made them short together. if the wires don't fry, then the battery will heat up and explode. therefore I'd definately put a fuse on the red wire coming off the battery set. just one fuse is all that's needed on the positive, because they're in series. to really calculate what size fuse is needed, you can get yourself a decent multimeter that does current (30 amps or more dc). hook the red probe to the red wire going to the ups, and the black probe to the red wire from the battery pack (put it inline as the fuse would go.) set the meter to on and do your whole power outage thing, letting the pc drain as much as it can from the ups. the meter will tell you how much power for a precise measurment. it's pry higher than you think, because at 30 amps, you can draw 720 watts from the batteries (volts * amps = watts). say you have a 720 watt power supply, meaning it can output that many watts. the power supply is gonna take more power than that because it'll lose power in the form of heat. not to mention the power that's lost converting the 24 volts dc to 110 ac. but yeah, 20 or 30 amp fuse.

[soulmata]

I took all that into consideration phonymary. I have formal and informal education in working with analog circuitry. This was more of a test run to see how comfortable I felt with this particular setup. I already checked the draw of the batteries during a charge cycle - it's on par with the stock units. The only concern I have is that it the charging circuitry for the UPS (which amounts to an AC to DC transformer with a high voltage (probably 13.5V or less) relay) won't be able to withstand sustained charging, and will overheat.

So next round I'm going to identify that unit and see if I can either passively cool it better, or even see if it is possible to replace it altogether. Odds are it will be just fine.

As far as cars go, I know perfectly well what an alternator can and cannot do. I currently run dual batteries in my truck via a battery isolator. I replaced the alternator with a higher capacity unit, but not for charging purposes so much as operating purposes in the event I have a high-draw load when my truck is running. Even still, I have a fuse in between the alternator and the isolator, and between the battery and the inverter.


Also, the fuse is for a lot more than just if I'm dumb and cut the wires. It is also so that if the battery voltage gets too low but the UPS doesn't shut off quickly enough, the wires will not overheat due to the increased current. I'm assuming the UPS will not even operate once the batteries dip below 11V or maybe 10.5V, but it's better to be safe than sorry.

And what the fuck is this you trying to give me an apprentice tour of beginner electronics

I have been doing projects like this for the better part of 10 years

I'm estimating the efficiency of the DC to AC inverter inside the UPS to be at about 80% since it is a cheap unit. Average sustained load on the unit is less than 1.5A, which ends up being less than a 15A load on the batteries.

[casualsax3]

Formal AND informal?

[soulmata]

I took several analog and digital electronics courses in college, as well as getting some experience in the field when I first took my current job

[PHoNyMiKe]

soulmata: yo momma so fat, when she gets a sandwich, she takes a megabyte.

p.s. thanks for repeating everything I said in my post but trying to look smart while doing so. I was only trying to help. fuckface.

[creaothceann]

[soulmata]

you're still my lover phonymike

whether you want to be or not

[PHoNyMiKe]

8==D ~° ~° ~°

[adventure_of_link]

awesome stuff.

[Rashidi]

awesome stuff.

the awesome-ness of phOnYmIkE being soulmata's lover ?

anyway, i'm not realy DIY person, but i know some DIY-like person who'll like the video.

[adventure_of_link]

awesome stuff.

the awesome-ness of phOnYmIkE being soulmata's lover ?

no, just how he turned a 7Ah UPS into a 80Ah one

I always wanted to make my own UPS... heh, hey phonymike, whatever happened to you telling me that I can stand not looking at a computer screen for a couple hours when the power goes out