A question about 9v batteries

[CyberStrat]

Last week I bought a line 6 wireless guitar system.

It is fantastic, except for what all the reviews say...low battery life (4 hrs), and a cheap plastic transmitter.

I want to try to rechargeable 9v batteries, but had a couple of questions.

If a standard battery is 9.6v and most rechargeables are 7.2v or 8.4v what will that due to the charge life? Will it be long enough for a gig? Also what does the mAh rating mean to charge life? some are 150 and some are up to 500?

Help?

Cyber

[yankeerob]

I'd be inclined to get the highest mAH rated cells that I could get... I've had a coupla wireless systems in my time and don't like the worry of the battery crappin out when you'd least want it... a good cable never lets you down (my current cable, made from 10 metres of low capacitance Tasker mic cable terminated with a right angle Neutrik and their silent jack at the other end is 15 yrs old and still going strong - never needs recharging!)... but as you've bought it and like it most rechargeable cells store around 20% less voltage than their alkaline counterparts - as did merc cells when you could still get them - so I wouldn't worry about voltage - it'll likely be quieter in any case... just get the highest mAH rated cells you can get and keep one on charge...

[chuckocaster]

get the industial or commercial duracells. that's all we used to use when doing live sound.

[cdw2000]

Like others have said, the higher the mAH rating the better. Rechargeables have a much flatter discharge curve than your standard alkaline battery, which means they maintain a more constant voltage while they discharge.

If you can find NiMH batteries, buy those instead of NiCd batteries (just make sure you have a charger that is designed for NiMH). NiMH are much less finiky about charge/cycles and hold their charge better than NiCd.

Advantages of rechargeables:

1) Maintain a more constant voltage
2) No running out and buying batteries at the last moment
3) More economical

Disadvantages:
1) Abrupt loss of power - rechargeables don't have a graceful drop in voltage so you don't get much warning when they are about to give up the ghost.
2) Don't hold charge well for long periods. You should make sure you charge them up before every gig. NiCd is worse than NiMH but both types exhibit this.
3) Wearout - both NiCd and NiMH batteries wearout after a number of charge/discharge cycles. After a time you will notice that they won't run your equipment as long.
4) If you end up with NiCd batteries, make sure you fully discharge them before recharging or they lose capacity.