Any reason NOT to use NiMH rechargeables??

[Meng_Tze]

I don't understand, in your example, the difference between recharging right after the previous dive, or a week later right before the next one. Are both not the same?

In the first instance, topping up right after a dive, you charge once right after the dive, and then again right before the next dive. That is twice. This however does ensure you store them with a charge. If you have a long time between charges, or usage on dive one was heavy (70% discharged) this may be your best approach.

In the other scenario, you leave the batteries as they are after the first dive and only top up right before the next dive. That is one time. If your time between charges here is less than the self discharge to reach less than 30%, this may be your best approach

 

[Meng_Tze]

After doing some reading yesterday, my "topping off" days are essentially over. I got the impression from reading, though, that NiMH were the most resistant to that practice.

What they mean by this resistance is the memory effect. Yes NiMH is far less prone to building memory effect. But they still have a life cycle, be that 500 charges or whatever.

 

[HenrikBP]

NiCad is pretty old technology in rechargeables. NiMh is the way to go these days. The latest and greatest in NiMh is rechargeables that retain their charge better - can't remember the exact times, but from vague memory about 90% of the charge after about a year.

Thomas Distributing has a bunch of different brands, but the Sanyo Eneloop batteries is one brand of slow discharge batteries.

Henrik

 

[ReefHound]

Lithium rechargeables will soon make NiMH old technology.

 

[Charlie99]

Lithium rechargeables will soon make NiMH old technology.

Lithium ion batteries of many different chemistries have been in use in things like notebook computers for years. In this application they have completely displaced NiMH. The advantages are much higher energy density both on a volume basis and weight basis.

The disadvantages of lithium ion for general purpose use are that the chargers are very specific to the chemistry and sometimes even the manufacturer of the the lithium ion battery. The output voltage has a large variation during the discharge cycle --- good for battery charge estimation, but bad if you want to drive a simple load without having a DC-DC converter. The output voltage of lithium ion cells vary with the exact chemistry, but are typically well over 3V.

These disadvantages aren't of much importance in a notebook computer or a cellphone, but are big disadvantages when trying to use lithium ion as direct replacements for alkaline cells.

 

[highdesert]

In looking for a NiMH combo charger for AA and C cells, I'm finding something like $90 at Thomas Distributing. Is that my only choice, or is there something less expensive but still "smart" available? And while on the subject, does anyone have any thoughts on the Maha vs Sanyo cells available there? Or are there better options yet? Bear in mind that I'm so tight I squeak when I walk; I will pay for quality, but it still must be a good value.

 

[Chewie07]

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.

 

[Damselfish]

I read someplace that many C rechargeables basically have a AA inside, and you you could simply use rechargeable AAs in an adapter and get the same result as the fake-like Cs. The adapter was http://thomasdistributing.com/shop/...erbradapts--aa-batteries-to-c-size-p-616.html

I would have thought I read about this here, but if I search on Nexcell I find a few mentions of batteries/chargers and nothing about this adapter. Anybody tried this? It would be a way of using only a AA charger and having only one type of battery. (For reduced burn time, of course.) I was thinking of trying this since we've wound up with a surplus of AA rechargeables.

 

[ReefHound]

AA rechargeable batteries sure are a lot cheaper and easier to find.

 

[Charlie99]

In looking for a NiMH combo charger for AA and C cells, I'm finding something like $90 at Thomas Distributing. Is that my only choice, or is there something less expensive but still "smart" available? ........ Bear in mind that I'm so tight I squeak when I walk; I will pay for quality, but it still must be a good value.

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.