How to test my GP3700 cells

[Mash Potato]

Hi,

Have some of the above, that have only been used a handful of time and sat in my batt box since.


Recently took them out again and noticed that on at least one of the battery bars there seems to be some blue/green crystalised stuff. Has the cell "vented" or leaked? What would you suggest?

Can I test the cell with a multimeter, if so what sort of readings should I expect?

If a cell is duff in my matched pack, can I replace with another 3700 cell that will obviously not match? I only plan to run a club level, so as long as they are reliable the'll be O.K for me.

And lastly, where can I still get GP3700 cells, both as single cells, and as packs?