Why can't I put rechargeable batteries in my Light

[diverdan214]

Hey All,
Just a quick question. What would be the problem with putting rechargeable C batteries in my light rather than disposable ones? If I can then what's the advantage of buying a rechargeable light?

-Dan

 

[bnajdrovsky]

Well, at least in case of NiMH batteries, your light may not be as bright as it can be since they are 1.2 volts instead of 1.5. Also, this type of battery has a sharp fall-off in discharge, so you may have light one moment, and no light at all the next when the batteries are drained. You didn't mention what kind of light you have, but in case it is the U.K. C-8 or the Light Cannon, then there is a rechargeable NiCad battery pack available for those lights. (which also tells me that stand alone NiCad C batteries would probably work fine with that light as well)

 

[DA Aquamaster]

NiCads have the same 1.2 voltage so they have the same potential problem with under volting the lamp. They also have the same very flat discharge curve where they put out nearly peak voltage right up until they put out nothing.

However, replacing a, for example, 6 volt lamp with a 4.8 volt lamp is an option on some lights and on others, the difference in voltage does not make that much noticeable difference.

If you are taking the light where you need a light, a backup is a very good idea whether you are using rechargeable batteries or not.

 

[diverdan214]

I have princton tecs to answer your question. A Shockwave II, Miniwave, an impact, and their red led locator light one. So yeah I dive with a backup(two really) just thought rechargeable batteries would be more economical and ecological over the long run (yes I realize I should have just got a rechargable from the outset). If I understand your comment right Aquamaster...I would need to change to different bulbs as well, other than that its just an issue of not being able to tell when I was about to lose power?

 

[Bobby_M]

Well I guess ignorance is bliss because I've been using NiMH batteries in my UK light cannon since the day I got it.

Bobby

 

[herman]

I looked at this a while back. You may not actually see much of a light output difference based on the voltage curves of both battery types (alkaline vs NiMH) after the first few minutes. At least according to all the graphs I could find, it's true that the inital voltage of alks is 1.5V, it drops pretty quickly to around 1.2V, roughly the same as the NiHM and then does a slow drop off. The NiMH tend to stay at 1.2V for a given time and then drop off sharply. Based on the graphs, it appears to me that you will get a brighter light for the first little bit with fresh alks but it would soon match then be less than the NiMHs. In contrast, while the initial few minutes of use the NiMHs would be dimmer, you would get a more even light output over a longer period with the NiMHs. This is based solely on looking at the graphs, it would be interesting to actually do a test.

 

[Charlie99]

I Based on the graphs, it appears to me that you will get a brighter light for the first little bit with fresh alks but it would soon match then be less than the NiMHs. In contrast, while the initial few minutes of use the NiMHs would be dimmer, you would get a more even light output over a longer period with the NiMHs. This is based solely on looking at the graphs, it would be interesting to actually do a test.

Another characteristic which makes actual brightness of NiMH and alkaline closer is that alkaline cells have higher internal resistance than do the NiMH cells. The output voltage of all batteries decreases with increasing load, but the NiMH drops less than alkalines. This isn't a big factor with light loads, but most dive lights drain the batteries over just a few hours and internal resistance voltage drop is significant.

I've used NiMH AA cells in both Ikelite PCa and UK Q40 lights without problem.

 

[diverdan214]

I've been using NiMH batteries in my UK light cannon since the day I got it.

This is really what I was looking for, it's not going to permanently screw up my light.

 

[JimC]

Rechargeable in your main light, non-rechargeable in your backups.

 

[jtivat]

Another characteristic which makes actual brightness of NiMH and alkaline closer is that alkaline cells have higher internal resistance than do the NiMH cells. The output voltage of all batteries decreases with increasing load, but the NiMH drops less than alkalines. This isn't a big factor with light loads, but most dive lights drain the batteries over just a few hours and internal resistance voltage drop is significant.

I've used NiMH AA cells in both Ikelite PCa and UK Q40 lights without problem.

This hit the nail on the head, and in fact higher wattage lights will often be brighter after a short time using rechargeable batteries as opposed to alkaline's.

If you get some really good NiMH AA's (RC car batteries) and put the UK 4AA Rechargeable Flashlight lamp in your Q40 you will have a really kickin light. It is a 4 watt lamp as opposed to the stock 2.1 watt it can be purchased at http://www.brightguy.com/detail.php?Sku=UND14824