Is there any reason why two batteries with identical specifications, but made by different manufacturers shouldn’t be used together? What about mixing up used batteries with new ones?
And finally, I bought a new set of rechargable batteries, and after the first charge, the plastic cover around one of them ‘melted’ away, leaving the shell exposed. Can I still use this battery? Do I need to buy a whole new set of rechargeable batteries for my digital camera?
In general, you want to use a matched set of batteries. That means not mixing different types, manufacturers or used and new batteries. Mismatched batteries can result in shorter battery life and damage/leakage of the weak batteries.
It’s a discharge rate issue. Batteries produced in a single batch, may differ in how they discharge power compared to batteries produced in a different batch. You want all the batteries putting out the same amount of power, at the same rate, over the use of the cell. If you have “flat” and “full” batteries in the same set, then those that are “full” are going to put out more current, and the “flat” batteries are going to absorb some of it. This can cause issues with overheating, and the leaking that mks57 speaks of.
In general, if you bought 3 packs of 4 batteries (same brand/model) each, and were using them at the same rate (assuming rechargables here) and recharging on a similar schedule, you could likely use them interchangably (sp?).
As for the one that has bubbled the outer casing, if this has happened on the first charge, then I’d likely return them for a replacement set. Modern battery manufacture is pretty good, but sometimes things slip past Quality Control.
If you are using rechargable batteries, the best practice is to use a set fully (full discharge) then charge completely. Using only “half of the charge” can result in some “Memory” and may reduce the running time of that set over the life of the cells.
Some battery chargers have a lid that can be closed, but if you read the fine print it says don’t close the lid while charging batteries due to excessive heat buildup.