Rechargeable batteries and wireless

[Marco Leavitt]

Have checked some old posts, and a lot of people were saying not to do it. Is this still the case? Now that I'm using more and more wireless, this is turning into a burdensome expense. Are there AA rechargeables that can be trusted in a wireless system now? What are good brands?

[Chris Soucy]

You may want to test drive the new - ish NiMh batteries and see if they do it for you.

Their power capacity is much higher than NiCads and all round seem to be a better bet.

Whether they work for you, only you can tell.


CS

[Dan Keaton]

Dear Marco,

Things have changed since those old posts.

In the past, probably less than 10 years ago, a rechargeable battery usually meant a NiCd (Nickel-cadmium) battery.

NiCd batteries, in the AA size, did not have anywhere near the power of a typical alkaline battery of the same period. And the voltages were different. NiCds were typically 1.2 volts where alkalines were around 1.5 volts.

Today, good rechargeable, in the AA size are typically NiMH (but Lithium-Ion rechargeable are also available).

The 8 Energizer AA's plus 4 AAA's plus an adequate charger can now be purchased for under $40 at wholesale club stores.

These AA's have 2500 mah (milliamp-hour) capacity with a voltage of 1.38 to 1.40 when freshly charged. If you let them sit for days, then the voltage will decrease. This 2500 mah capacity is greater than a typical alkaline battery, but the voltage is less.

An alkaline battey is a better choice in any application where the battery has to sit for months before being used. Rechargeable self discharge, thus are best when recharged just prior to being used.

These work very well in the Sennheiser G2 wireless systems and Sound Devices 302 mixers.

I just recharge my Energizer NiMH AA batteries the night before each shoot. The latest Energizer charger has four lights that indicate the charging status of each battery. The only drawback for this relatively low cost system is that you must recharge the batteries in pairs.

To be safe, I test each battery after charging with a voltmeter. However, the Sennheiser G2 units have a built in battery level gauge that works just as well.

I find that some of my oldest Energizer AA batteries do not quite reach 1.38 to 1.40 volts. As someone said on this forum, you are more likely to lose the batteries than they are to wear out.

These batteries can be recharged hundred's of times.

If you purchase two of the Energizer systems, you will have 16 batteries and be able to recharge 8 at a time, which usually takes up to 8 hours.

Other NiMH batteries and more sophisticated chargers are available. Energizer has a 15-minute charger that works off of household current, or a car’s 12-volt dc power, but I have not found it at the wholesale club stores.

[Phil Bambridge]

Also, and especially if you aren't going out day after day, there's a new formulation of NiMH battery that doesn't self-discharge so quickly. Normal NiMH's have a tendency to lose charge when sat on the shelf, doing "nothing". This is why they're no good for emergency torches (flashlights) and the like.

But the LSD (Low Self Discharge) models from Sanyo (under the name Eneloop), Panasonic (Infinium) GP (ReCyko) amongst others, greatly reduce this effect. They claim that it will hold 80% of the charge after a year, and improve with use.

I'd like to seem the graph of remaining charge over time though- 80% after a year sounds very good, but what if it was about that only a week from being charge, then stayed the same for the next 51 weeks? Also, I couldn't find them in as high capacities, but this might be more that more respectable manufacturers are more truthful about their amp-hour figures.

[Jack Walker]

Here is another thread with a discussion of rechargeables, including some links to resources:
http://www.dvinfo.net/conf/showthread.php?t=112160