NiMH Batteries

[Daryl Morse]

I just bought a UK D4 and I plan to get a set of NiMH batteries. I've looked around at some of the websites that sell batteries and I've noticed a wide range of capacities for a given size. For example, Thomas Distributing has D cells ranging from 4500 to 11000 mAH. The 11000 mAH D cells are from Powerex. They are almost twice as expensive as the 4500 mAH batteries.

Does anyone have any experience with these batteries? Are they worth the extra money?

 

[Mike Newman]

Sorry to seem obtuse - but define 'worth'. NiMh high capacity batteries are well worth the money if you are going to be placing demands on them for longer than average periods. For example, if you really enjoy digitial photography and take dozens of shots per dive, with preview screen in heavy use - consider higher capacity batteries well worth the expense. How frustrating to have your batteries run down just as you see the most appealing subject of the whole dive come into view.

Bear in mind that some batteries now have outstripped the capacity of chargers to cope with them. i.e. the timed charge (or safety cut-out in the case of peak-sensing chargers) stop charging before the cells are really at full capacity.

In my experience - particularly since NiMh have no real memory effect - and can be recharged daily, despite charge remaining - they are an excellent buy - and the higher capacity the better.

Hope that helps.

 

[Geddes]

IMHO, if the cheaper, 4500mAh Batteries will give you enough light to reach your dive limits, then why bother with larger capacity (and more expensive) batteries. I suppose if you dive someplace too remote to recharge during a long (overnight) SI then having a huge capacity would be sensible.

I agree with Mr. Newman, NiMH is the best battery technology readily available. Also, a high-quality charger will charge decent betteries to their max potential, a cheap charger won't maximize even the best cells, and may even cause damage. Bottom line, get a quality charger designed to charge NiMHs.

 

[fmerkel]

The "standard" NiCad batteries in the UK rechargeable pack for the D4 are 4400 maH. Those will give you an easy hour+ dive with a fresh charge using the 18 watt lamp. If you are doing 2 dives regularily without the opportunity to charge and don't want a second set of batteries then the higher capacity will be a better value.
I bought some 8500's from Thomas Distributing about a year ago. At first I felt ripped off because they didn't seem any better than the 4400's but they improved with a few cycles and will go 2 dives now.
I agree, get a good charger to go with it.
Add the 18 watt lamp for lots more light.
Fritz

 

[mleong]

Well, how often will you be using the dive light? Once a year, evey month or rather every 2 weeks. Of course it would make sense to spend the extra if the battery are to be used very regularly, if not just the normal disposable ones will be much better

 

[fmerkel]

Agree with the note on use. Rechargeables need to by cycled. If they go long periods without use they self-discharge (normal) and go dead-permanently. At least NiCads did. I'm not certain how NiMh will take to neglect. If you use them less than once a month or will have long periods of inactivity it actually may be better to stay with alkalines.

Fritz

 

[Daryl Morse]

Thanks everyone for the replies. My question was a little obtuse, so I appreciate that you read between the lines.

I'd like to be able to get in two full dives while using the light on "high-beam" so maybe I'll get some 9000 mAH batteries.

I already bought the 18 watt bulb because I planned to get the NiMH batteries from the start.

From my experience, NiMH batteries are much better than NiCad as far as "memory" goes. That's why I didn't go for the UK recharge kit. (That and the price.)