we think that you should not trash so many batteries. we made good experiences with those accumulators.
its so sad that the amplifiers do not feed the guitars (like the Paradis Avalon in the 90ies…)
to play a safe show, many musicians exchange their batteries before they are really used… understandable!
but much better is to charge them before every show!
we also saw that musicians do not use their instrument for some month and when they come back to it, the battery leaked and the contacts rusty… Lithium is much better in this than NiMg and others. they self-discharge very slowly!
and Lithium allows a bigger capacity than NiMg. they have a little lower voltage but for most guitars and especially for the Polybass equiped ones this is not a problem, we tested and use them in praxis!
use this charger made for it (an ordinary NiMg charger most probably does not work or distroy)