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09:34 am - hardware hack: UPS Battery Upgrade

I replaced an old UPS's worn-out sealed lead-acid battery with a very large marine deep-cycle battery. The result: probably a day's worth of off-grid runtime for our house server, for about the cost of a replacement UPS.



You need:



* Old UPS that is bitching about a replacement battery, but otherwise works.

* Deep Cycle marine battery, about $90, from your local megamart.

* Ring connectors that can screw down to the battery's terminals, about $3, near the battery display at the megamart. Don't use clips!

* Probably: A length of extension cord to make your UPS battery wires long enough to reach the battery's mount location.



How to:



1. Cut the connectors off the old UPS's battery wires and strip the ends.

2. Get a length of at-least 14 guage dual-conductor polarized zip cord (as an extension), strip the ends, and fasten to the UPS battery leads (observing polarity) with solder or crimp-on connectors.

3. Crimp battery ring terminals to extension conductors and solder thoroughly.

4. Securely mount the battery so it can't tip over, and place it where any possible leakage will be contained (in a tray, or over a sink or drain)

5. Paying strict attention to polarity (+ to +, - to -), screw down ring terminals to battery. Mind nothing metal touches both battery terminals at the same time!



Your UPS should be able to generate off-grid power now, as lead-acid batteries come fully charged from the store. Plug in a lamp or something and give it a test. Assuming everything works, plug your equipment in to the UPS, plug the UPS into the wall, and never worry about grid failures taking out your server again.





Addenda Whys and Wherefores:



"Don't use clips": Ring terminals can be screwed down for secure electrical contact. Clips tend to wiggle loose and can oxidize, resulting in intermittent connections.



"Use polarized, dual-conductor, 14-gauge extension wire": Polarized wire helps you keep the + and - conductors distinguished. If you get the polarity backwards, you will kill your UPS. 14-gauge is a good size for a standard desktop UPS. Speaker wire is ideal and inexpensive.



"Put the battery over a tray": Lead acid batteries can, very rarely and under extreme abuse or catastrophic failure, leak a dilute sulfuric acid solution. You don't want this on your carpets.



"Solder when possible": A crimp connection is generally reliable but subject to pull-out and possible oxidation, but a soldered and crimped connection will never fail.



"Deep Cycle Marine": Regular or "Starting" lead-acid batteries cannot tolerate repeated full or near-full discharge. They are made to put out lots of power to start an engine, not run low-power electronics. Golf Cart, Deep Cycle, and Trolling batteries are made to be discharged slowly and fully -- so use them for your UPS.



"Why not just buy a new UPS battery?": They're not stock items at any store I live near, which means mail-order and shipping, which means paying to move LEAD around, which means they're expensive to buy and expensive to ship. I'd rather spend a little more and get a very large battery with much longer back-up time.



"What do I do with the old UPS battery?": Give it to the store you buy the marine battery from. They're required by law in most US states and Canadian provinces to accept old lead-acid batteries for recycling if they sell new ones. DO NOT THROW IT AWAY.