During Irma, another UPS started emitting the unmistakable smell of burning electronics. We shut it down to troubleshoot it after the storm. I pulled the batteries and did a life test on them with my Computerized Battery Analyzer (CBA-IV). The batteries were fine. Put the system back together and it ran for a while, then starting smelling like smoke again. Not good.
So the UPS itself was scavenged for useful parts and the batteries put aside. Yesterday, I put "2+1" together and put the two good batteries into the old but good UPS. It seems to work fine and doesn't stink. There's the small matter of the batteries being too big for the case, but that's kind of a feature. It gives more back up time than the original. If I wasn't quite as willing to live with the battery cover duct-taped on, I'd figure out how to make a new one. I know! I'll build a 3D printer from scratch to print a cover!
Is there any rule of thumb on how much larger a replacement battery can be in a UPS without taxing the charging system ?
ReplyDeleteThanks, TEX.
Can you deal with a really "seat of the pants" WAG? (WAG = Wild Ass Guess") I don't want to imply I know much about the design of these things.
DeleteMy guess would be around 50% larger. Maybe even double the capacity. Lead acid gel cells like this can be charged by applying a slightly higher voltage and allowing the current to be higher at first, then taper off as they charge. I don't know exactly what they do, but I think if you limit to something like 25 to 50% bigger, you end up just taking longer to charge. It's possible the display about how long the battery will last will be based on a look up, not measuring how much it discharges, so it will be very wrong.
Insert all the disclaimers you can imagine in here, like "I'm just some guy on the internet with a blog, I never worked for APC, I've never designed power supplies professionally" - anything you can imagine. I really don't know what I'm talking about here, but I'm experimenting with this UPS.
One of the limiting factors is the ampacity of the charging circuits. I read where a guy used two deep-cycle AGM automotive batteries as replacements, and the charging circuit couldn't cope with the demands of a battery capacity that high being deep-discharged. He had to "jump" the batteries with his automotive charger if they were too low for the APC charger to handle.
ReplyDeleteAbsolutely. I mean, take the absurd case of a room full of big storage batteries; you know it's not going to work for that. The other limit is the battery it was intended for, and you know it will work for that. Somewhere between those is a practical limit. I'd guess these are something like 25% bigger and my guess is it could be a bit bigger. I'm willing to experiment with it, but it's going to be watched. Plug in a 100W incandescent and see how long it thinks it's going to run, then how long it does run.
DeleteThe charging circuit will work fine on much larger batteries as long as the voltage matches. I.e. if there are (4) 12 volt batteries in series (48 volts) is replaced with the same "voltage" batteries (48). What will happen is, the charger will limit the current going to the batteries during recharging, and if the batteries are twice as big, it will simply take much longer for them to reach full charged state. On the flip side, the UPS will still draw the same current when running on batteries, the larger units will just offer longer protection. I was a UPS tech for 8.5 years.
ReplyDeleteThanks for the input! It's always good to have someone drop by who knows the products. And thanks for confirming the only likely issue is it taking longer to fully charge.
DeleteHow do you feel about the question of "how much bigger can we go with the batteries?" 50%? Double what it came with?
Why don't you move the electronics over to the bigger case?
ReplyDeleteIt's actually harder.
DeleteThere were four boards in the case that are designed to plug into each other and need some mechanical mounting points molded into the case. Everything was a different size between them. There would be much more kludging, bubble gum and duct tape moving the boards than moving the batteries.
The only thing I give up is having to mount the UPS differently. I could lie it on its side or stand it on something that supports the back at the same height as the batteries.
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ReplyDeleteI needed to correct the tone of my comment.
ReplyDeleteInstead of moving the electronics, maybe put the batteries into a separate box? Some sort of inexpensive storage box? It would be easy to extend the wires that connect the batteries.
And instead of moving the batteries, could you make a lid from some leftover clear plastic from the guitar rebuild?
I saw no reason to change the tone, but you're the author.
DeleteThere's nothing wrong with separating it into two boxes. That's a fine approach. The cover design is the problem, if I want it to be a "real" cover and replace the one it came with. I can't do graphics in a reply box, but the cover ends up being a compound curve having three right angles. The end that engages the snaps on the case has to have fingers that slip into those snaps.
I tried to do ASCII graphics, but the comment system wiped them out.
If I wanted a cover that really fit like it should, it's a complex little part, with a straight vertical side on the left (the view in the picture), right angle to a straight top, right angle to straight vertical right side, then right angle bends to the right (outward), straight horizontal with little fingers on it to match the taps on the box.
Each of those corners is sharp. It should also be capped on the ends, making it like a tub. It's well beyond any plastic fabrication skills I have, and nothing lying around looks like it could go there.
The duct tape serves a purpose here; keeping conductive things from finding the battery terminals.
Besides, if I didn't use duct tape it wouldn't be a true Bubba job.
It's not really a true Bubba job unless you also drank a six-pack of Shiner while building it...
DeleteI have a friend in Victoria. When I visit him, I stop at the Spoetzl Brewery. I'm not sure I'd call that "Bubba" beer - the Shiner Bock tastes pretty damn good to me. I want to try their Oktoberfest sometime, too. Have you had that one, Mark?
ReplyDeleteSome UPS's are designed to take much larger battery packs, I have a APC UPS that has a plug on the back for a external battery pack that is double the internal one. Some Libert units can take a rack full of extra batteries.
ReplyDelete-Joat