pindokhan123 wrote: you are very much like me,i like recycling old things,even tho it means spending a bit of money to get em working again rather than going out and buying something new which is hard to afford nowadays.
Thanks Pindokhan123 - an also interesting experience was when I bought a faulty UPS Apollo 1140DJ for 5 € about 3 years ago. The owner told me that the batteries inside were dead. I took it apart & I saw that the primary reason was 3-4 failed MOSFET "IRF-something" transistors (themselves all black; burnt as well as damaged copper leads on the PCB). I managed to recreate the missing copper leads on the PCB & replaced the damaged MOSFETS with new ones for les than 5 $ (I think) on eBay.
However I also looked in my shed if i could install some better copper or aluminum cooling sinks to fit on all 6 MOSFETS. I suspected that they were not cooled enough during operation. I found the proper part, put everything together & greased the MOSFETS with some nice silver cooling paste.
The UPS was powered on by two 12 V 9Ah Pb-gel batteries that, if the owner had disconnected them when/after the MOSFETS died on the PCB, they could surely have been preserved. Especially if he would have put them to some other use. So instead they stayed locked in that UPS for 2 years (as I remember from the owner's info) & became badly dehydrated & sulphated.
I managed to rehydrate the batteries, however the sulphation problem was beyond repair. After a year of using a home-made desulphator, I didn't make any progress. I suspected fractured cathodes inside the batteries. So I filled those 2 batteries with the most of tap water I could fit inside those 6 fill-ventilation holes & took them to the local junkyard. I got a few Euros back so at least I covered the costs for buying those new MOSFETS off eBay.
A couple of months later, I came across some free 12 V 7Ah Pb-Gel batteries, tested all of them for capacity, rehydrated them & put 2 (of the best among the stack) into this UPS. It's been working like a charm ever since.
If I was to (re)sell the UPS, the price would be around 50-70 €.
My next project is building & selling custom PowerBanks for the new craze that has also hit Slovenia - PokeMon chasing (using SmartPhones). A nice niche to capitalize on (mass stupidity that is).