I have an old (very old!) style (green) Ozito 18v lithium ion drill. One of the two battery packs died some time ago but I have survived with using the second one until it too has just died. It appears to charge but runs out of puff after a very short time. After charging it's reading over 20v. I'm assuming it's the battery and not the charger. 1 - is that a reasonable assumption and how can I test? 2 - if it's the battery pack, then how can I test if it's the BMS or the batteries? 3 - If it's not the batteries, can I deconstruct both packs to get one working unit? 4 - if it's the batteries, is it best to simply buy a new unit (not sure if they are still available) or buy some new batteries to install in the unit. 5 - if the latter, then what do I need to look out for? Lots of questions! Any advice welcome. Thanks.
Battery could read 20V but hold little to no current, therefore dies unload load, can easily happen to any battery, especially over time. Test it under load to see what it drops to and you might get your answer. If you can de-construct Ozito batteries you might be able to make a single battery but it will depend on how many cells are dead in both batteries. You'll have to do a cell test of each one if you can get them out. You may be able to replace the cells individually (from somewhere like Fleabay) and make a new battery, I've never owned Ozitos so I don't know but I have re-constructed other batteries from dead ones over the years.
Yes. Charge it, open the battery pack up and measure the cell voltages. If some are lower than others, they're likely bad cells. Replace the cell (likely 18650). I highly suspect it's the batteries. If you want to test it before buying anything, swap a "high" and a "low" cell around, drain them manually (hook up a load to the individual cells) Only if it's not the same fault on both. If it's 18650s, just replace the batteries, you can get them in old laptops, power tools (obviously), e bikes, scooters, etc. They start at around $2/each and an 18V will have 5 cells. Wear gloves in case you're allergic to nickel, make sure you don't short or puncture any of the cells, good way to start a fire. If you're careful, you'll be fine.
It'll be the batteries, you'll be the proud owner of packs with a lazy cell or two in each. Could be a tad fiddly to replace but not un-doable, no worse than rebuilding the 2 packs for my little 12 volt Ozito drill last year using cells out of a sick genuine Dyson cordless vacuum pack. If they're also 18650 cells in yours there, have a look at Yum Cha-brand cordless battery packs for 20-odd volt Dysons off evilBay and disembowel one of those. Last 18 volt pack I had to Do The Deed, a new cordless vacuum pack here in Oz cost me $24 delivered, and the cell capacities were very schmick indeed. Other source for cheap cells, used but tested - Farcebook's Marketplace. Occasionally there'll be someone in there selling tested cells at sane prices, usually in quantities of dozens.
