UPS at work needs new batteries, so I spent an evening doing this. Old ones from 2010 have degraded from the load shedding to the point that they only run for 10 minutes. So after buying a few new batteries ( 66 of them........... 2 were for the burglar alarm for the same reason) I took the UPS apart to install them.
Removed the old 220VAC fan, as it had quietly died sometime since 2010 and no longer was cooling. Did not make a difference with that massive heatsink inside there.
The old fan hanging around, while I was getting the new one in place. Had to change from the small faston terminals to wire leads on the new fan.
The main controller board, been there since 1999 when we bought this UPS. the model underwent a name change, but is still in production in Johannesburg. Wonder if I can get a firmware update for it.......
Mains in and out, with the spare 2 cores in the 4mm cable being used for the PE function. There is a redundant earth bond as well joining the 2 panels, just in case the UPS is disconnected.
Mains transfer switch, using a big set of SCR modules. Other side is a IGBT module for the inverter charger. Other side of the heatsink has a H bridge that makes the output AC when needed. At the rear you can see one of the output filter chokes. The others are similar in size and have around 20uF of filter capacitor with them.
4 banks of 12V 8Ah sealed lead acid batteries, so you have a few batteries to change.
Half way through the one bank, new cells in and half the link wires installed. I made new jumper leads in 2010 as a few had been damaged by leaking cell terminals.
Luckily this time there were no leaks. A 100m roll of 4mm flexible stranded wire, 2 boxes of the right size faston crimp terminals from Hellerman, plus a few hours of work with the crimp pliers. Still have 80m of cable left but this is slowly being used inside equipment. I made the jumpers beforehand as I had seen the corroded ones opening the unit to inspect.
Now I have 66 used batteries that have some life left, so used them in non critical places to replace old batteries. Plus made a UPS for my cordless phone, using 2 old burglar alarm power supplies. One used as is to charge the battery, the other had a few resistors removed and changed to change the TO100 LM723 regulator from a 13.8V charger to a 6V5 regulated power supply. Old battery will do fine with that low load to last the typical load shedding of 2.5 hours. I probably will add a second in parallel to increase capacity if needed.
30 are in another old 2kVA ferroresonant UPS, as it had cooked the last set to nothing. Originally used 3 12V car batteries in series, now has 10 sets of 3 cells. You know a battery has an issue when it has swollen to a round ball and melted itself to the neighbours. Even with that it held up for 30 seconds..........
Soon to the scrap yard to recycle them, $7 per box of 8
