We have some rechargeable batteries that are used on our Nagra LB's (8 in total) They are not the best and many of them are now refusing to recharge. There have been a number reasons for and my question is this: When recharging, can you just leave the batteries in the recharger for as long as you want or will this process eventually damage the batteries lifespan
Older/cheaper batteries can be damaged by "overcharging", but good ones won't be. Also depends on your charger. "Smart" chargers will stop charging once the battery is full, and can keep them full over an extended period of time. Check the manufacturer's specs on the batts and charger to figure out which boat you're in.
Also, how long have you used them? Rechargeables are only rated for a certain number of charges before they "die".
Yep - leaving batteries in the AA charger was a no no while I had rented Fostex and Maranz. Specifically said to not leave them in past when the light turned green - the batteries would then start to drain life.
I like the lithium ion battery packs - the kind that look like they go on camcorders - but they are for the Sound Devices portable recorder line. Those wont drain back down, and you can charge them with the wall adapter plugged into the device, or with a battery charger for the wall as well.
Sometimes you can find what I guess could be called "logs" that fit into certain devices that are hooked to a larger battery source/brick. Might try looking for one of those if one exists for the Nagra.
Best of luck!
modern day chargers will switch off after a certain amount of time. this can be up to 16 hours. (this variable amount is one of the reasons why you don't mix different brand chargers&batteries). NiMH batteries are fiddly and in addition to a varying memory effect usually self-discharge. Only brand (AA) that I've seen perform well over a long period of time is Eneloop (now licensed and branded by Apple too).
The whole issue of battery "memory" and decreased capacity over time has to do specifically with the battery's chemistry. Eventually, any rechargeable will dry up, it's simply a matter of how fast they do it (and "memory" affects that particular variable). NiMH and Lithium Ion are two of the chemical types least susceptible to battery memory. But, like I said, sooner or later everything dies.