Any reason NOT to use NiMH rechargeables??

[Chewie07]

Absolutely... You can always get an AA>C adapter and use AA instead of C batteries. But (my previous post was convoluted, sorry!!!) the only issue is runtime. You can get 2500mah AA and 2500mah C batteries (energizer, sanyo, duracell, etc.) and they are identical batteries (except for size).

I decided to go with the higher capacity C batteries (5000mah) so that I can have more runtime and more usage time between charges. You pay a little more, but I feel like I'm getting "more" from the larger battery.

I'm bad at drawing mental pictures, but here goes...

You can have a 1 liter bottle of soda filled with 1 liter of liquid (AA battery) or you can have a 2 liter bottle of soda filled with 1 liter of liquid (typical C battery). I opted to purchase the 2 liter bottle of soda filled with the ENTIRE 2 liters (5000mah C battery) of liquid. If you look at the cost of batteries in the store, I feel like I got my money's worth.

That's all I've got

 

[Hoosier]

A rechargeable option is definately more economical choice. But, the charge set only lasts a half of a shelf battery (non-rechargeable). For example, UK HID Canon hold 8 C cells. It will cost a lot if you keep using a shelf battery.

 

[ReefHound]

You can have a 1 liter bottle of soda filled with 1 liter of liquid (AA battery) or you can have a 2 liter bottle of soda filled with 1 liter of liquid (typical C battery). I opted to purchase the 2 liter bottle of soda filled with the ENTIRE 2 liters (5000mah C battery) of liquid. If you look at the cost of batteries in the store, I feel like I got my money's worth.

But if you've got a virtually unlimited supply of liquid and can replenish the bottle, it might be more economical to just go with the 1 liter bottle and keep refilling it as needed.:14:

 

[highdesert]

I just purchased two new dive lights (both UK) models. I opted to go with the nimh C rechargeables (these are 5000 mah capacity, brand name is "tenergy") and this charger:

http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=1652

This shop also has an ebay store as well (which is where I purchased my batteries and chargers):

http://stores.ebay.com/All-Battery-Center.

Just make sure you look at the battery capacities (mah) when buying rechargeables. You can get "C" batteries as high as 6000mah, whereas the energizer and duracell rechargeable "C" batteries you purchase at any store are only 2500mah capacity (which is the same capacity as their AAA rechargeable, so basically the AA and the C have the same run-time, in theory!).

My observations are that my lights running on alkalines or NIMH have the same brightness... The brightness on the NIMH lasts longer however.

So, Chewie07, if you read Charlie99's post #20, how does the label on the back of your charger compare? I do like the idea of paying $20 as opposed to $80-90, but that old "you get what you pay for" phrase is nagging at me ...

 

[Chewie07]

The big jump in improvement in chargers is when you go from the overnight chargers to the fast chargers.

Another, more subtle improvement is when you go from chargers which charge two cells in series up to the better chargers that individually charge each cell. It isn't always easy to tell if a charger monitors each cell individually. If a charger can only charger 2 or 4 at a time, then it charges two in series. If the label on the back for a 4 position charger say something like "Output: 1.5VDC 500mA x 2" then it charges two in series rather than monitoring each cell. This sort of charger can lead to overcharging of one cell while undercharging the other.

My favorite AA charger is a relatively cheap Panasonic charger than came bundled with a pack of AA and AAA cells -- part number BQ-390A. It has 4 charging outputs of 550mA each. Charging termination is on an individual cell basis. Very small, lightweight. Travels nicely. The other thing to look for is a charger that can accept 100V-240V, 50/60Hz. That means that it has an internal switchmode converter rather than a bulky, heavy transformer.

The next step up are chargers that start including more features such as automatic load testing and proprietary charge algorithms. IMO, the features are pretty much just cosmetic hype and aren't worth the price.

highdesert, I'll use Charlie99's quote again...

You're right, I am a HUGE fan of "you get what you pay for". I looked into the MAHA charger that I think you're referring to from Thomas Distributing. The MAHA charger does use a proprietary charging algorithm and the one I listed uses the tried and true negative delta v. The one I listed also can charge 1 - 4 batteries independently (and do some other fancy stuff with them).

At some point this is WAY beyond my comprehension of chargers (that would be right... about... now).

All I know is that I am having no problems with this charger and it works fine for my needs. I had to just accept the fact that these batteries and the charger will not last forever. I am not using them for a ventilator or some other life saving device (I know, I know, I keep a AA led backup dive light JUST IN CASE and I am using disposable batteries in that one) so I figured why buy the lamborghini of professional battery chargers when my needs do not require such a high end charger (just like I did not purchase a titanium dive knife either ).

But in the end it's just my $0.02.

P.S. I hope this is not against any rules but I've learned a LOT of information on rechargeable batteries from here:

http://www.candlepowerforums.com/vb/forumdisplay.php?f=9

 

[Charlie99]

The MAHA charger does use a proprietary charging algorithm and the one I listed uses the tried and true negative delta v.

Just a minor technical nitpick ---- while a negative delta V works well for NiCads at any reasonable fast charge rate, NiMH cells don't have as dramatic a drop in V as they hit full charge. It is more common to use a zero delta V, or even just monitor the delta V and terminate the charge when the voltage vs. time rate of change is still positive, but slower than during the main charge period.

Quite a few chargers will also go from fast charge to a topoff charge rate that is less than the fast charge, but greater than the trickle charge ---- the delta V charge terminations are quite often only at something like 80% charge.

The medium priced fast chargers are mostly based upon delta V charge termination. Works pretty good.

The overnight chargers don't charge the batteries fast enough to be able to have enough delta V change for reliable charge termination. They normally either just keep charging forever (not too bad with NiCds, but horrible for NiMH) or have a fixed period timeout of something like 14 or 24 hours. The one thing that overnight chargers ARE good for is periodically ensuring that AA cells normally charged with a fast charger are all fully charged -- this is of more importance if you are using a charger than only charges 2 or 4 at a time. A few hours on the overnight charger will top off any cell not fully charged when the two cells were being charged in series. A fancy term for this is "charge equalization".

I haven't designed any chargers for commercial sale. OTOH, I have written the design specification and supervised the design of the integrated circuits on which many chargers are based.

 

[highdesert]

OK, OK, peace, truce, all that good stuff, you guys! I'm just a poor diver unencumbered by money to burn who wants to charge his batteries!

That being the case, can I buy this ...

http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=1652

... and end up with a decent unit that will get the job done? Or, can someone point me to a comparably priced unit (let's say under $50 max, less is better) that will do the job better? I definitely want the ability to charge both AA and C cells.

 

[nereas]

Do you top up daily but do not use the batteries daily? If this is the case, you may be effectively shortening their life.

...

Meng is right, because the typical life cycle of a NiMH battery is 1000 cycles.

Therefore if you recharge it every day, it will last 1000 days (3 years).

If you recharge it every week, it will last 1000 weeks (19 years).

If you recharge it every month, it will last 1000 months (83 years).

I suggest weekly charging. This is what I do with mine.

My 24V/4A chargers cost me $125 each.

 

[RonFrank]

NiCad is pretty old technology in rechargeables. NiMh is the way to go these days.

I can not agree 100% with this logic. NiCad batteries have some issues with memory, but they work much better in devices that tend to deplete batteries to a zero charge. Nimh batteries don't like to be drained all the way down. Lion batteries are really the way to go for most devices these days, and is the technology being used in most laptops, digital cameras, and phones.

However you don't see NiMH batteries being used in high demand tools like Dewalt Drill drivers and saws. The main reason is that those devices tend to get used until the battery is full depleted. The appropriate tool for the job, so to speak.

 

[RonFrank]

If you want to charge C batteries, you are limited on what chargers are on the market, and the price. C and D cell charges (most C do D also), but they are nowhere near as popular as A/AA chargers, and therefore more expensive.

A cheap charger works, but you will spend more money in the long run as if charging is not done properly, you never get a full charge, or the battery may overheat during the charge cycle. Both deplete the life of a rechargeable battery and the performance during use.

Another downside of a C battery charger is that they don't travel well. They are large and cumbersome.

I like MAHA/PowerEX chargers. I did a lot of research when I first purchased a rechargeable system, and it was top rated. HERE is a model that will do all battery types, but it's not cheap.

The one you list looks good, and Thomas has a good rep as well. You should really be asking THEM what they think.

I personally like the idea of the AA to C converters, but this depends on what type of burn time you want.

Other have covered the voltage difference. Just make sure your light is designed to use Nimh batteries, because some are not. My old Nikon flash units for example go nuts when I attempt to use Nimh batteries. I don't know why, and the work fine with Alkeline, and Nicad batteries, but NOT with Nimh.