Using rechargeable batteries in a backup light?

[tbone1004]

you really have to remember how dated many of GUE's stances on things are and while they were all completely valid at the time, they haven't come around with the technology. This is certainly one of them. At the time this was implemented, rechargeable batteries were not reliable. Times have changed. Just because UTD is run by AG doesn't mean they are selling high quality products and those batteries are on that list.

I dive only with li-ion batteries though I'm not quite as paranoid about them as you are. They get charged the night before a trip, and only charged if they get turned on more than the initial light check pre-dive. I also only use real Panasonics because I have had failures from the cheap li-ions

 

[stuartv]

How do you test these specific batteries please? I have a sophisticated battery tester but it doesn't test these types.

I use an Opus BT-C3400 charger/tester. It has several modes. One of them charges the battery, then completely discharges it, to measure the capacity, then charges it up again. It reports the capacity at the end. It allows you to choose from several options for the current it uses during the test. I think it has 500mA, 700mA, 1000mA, and (can't remember for sure) maybe 2000mA.

 

[KeithG]

you really have to remember how dated many of GUE's stances on things are and while they were all completely valid at the time, they haven't come around with the technology. This is certainly one of them. At the time this was implemented, rechargeable batteries were not reliable. Times have changed. Just because UTD is run by AG doesn't mean they are selling high quality products and those batteries are on that list.

Agreed. It is fairly easy to perform your own reality check on this one.

Think about a few modern "critical life support" systems and see what type of batteries they use. I first thought of general purpose computer / electrical UPS. Maybe not so critical? Move on. Then I considered emergency flashlights in commercial airplanes (we all walk by one mounted on the wall everytime we board). Not sure what that technology is. It could be out dated as well? Move on.

Then I went to something that really is life support: infusion pumps used in the Intensive Care Unit of hospitals. My father was on one of these for several weeks. It used rechargeable batteries. I was able to find a reference from a manufacturer that stated rechargeable batteries are mandatory.

 

[cerich]

Policies based on the quality of a technology need to be updated as the technology improves.

yup... it is not 2000 when that policy was sound.

 

[kensuf]

While lithium cells do hold a charge better than older nicad or nimh batteries, they still have a few things to consider.

A deep discharge will damage the battery, this can be prevented by having a circuit to stop the battery from discharging too deep. The electronics to protect the battery can be a failure point.

Unlike alkaline, lithium cells will deliver a fixed voltage until they are close to the end, and then drop out very quickly. In terms of a light this means your light will be nice and bright and then it won't be working. Alkaline gives a steady/slow decline in voltage as the cell is discharged, which means your light gets periodically dimmer as the dive progresses (warning you of impending failure). At the very least, you need to periodically test those lithium cells so you know exactly how long they'll burn -- the simplest test is to put a fully charged one in a bucket of water and start a stop watch.

IMHO, alkaline cells are cheap, readily available almost anywhere in the world, and reliable, so I'm in the "throw them away once every six months camp".

 

[KevinNM]

Agreed. It is fairly easy to perform your own reality check on this one.

Think about a few modern "critical life support" systems and see what type of batteries they use. I first thought of general purpose computer / electrical UPS. Maybe not so critical? Move on. Then I considered emergency flashlights in commercial airplanes (we all walk by one mounted on the wall everytime we board). Not sure what that technology is. It could be out dated as well? Move on.

Then I went to something that really is life support: infusion pumps used in the Intensive Care Unit of hospitals. My father was on one of these for several weeks. It used rechargeable batteries. I was able to find a reference from a manufacturer that stated rechargeable batteries are mandatory.

UPS batteries are lead-acid for big ones, some sort of polymer rechargeable for the single-phase ones. You can get a decade+ out of lead acid and a very long life for the UPS, the single phase ones two to three years battery, with the single phase UPS having a life of 4-7 years typically.

Medical gear gets formally serviced at least once a year, where batteries get replaced, gaskets get changed, etc and the whole system is tested.

 

[KeithG]

IMHO, alkaline cells are cheap, readily available almost anywhere in the world, and reliable, so I'm in the "throw them away once every six months camp".

Do you test you "new" batteries? Do you have a process that makes sure you replace them EVERY 6 months? Sounds a bit like a "trust me dive" approach?

I used to have a dive computer that used coin cell batteries. When i bought new batteries I wrote the date on a tiny round piece of paper (the same diameter as the batteries) and stuck it into the battery chamber. Between dive trips I placed the paper in first to isolate the batteries so that the computer was OFF. Before each dive trip I moved the paper to on top of the batteries so that the computer would work. I also checked the written date. This was fool proof in that I had to move the piece of paper to get the computer to work - so I could not forget to check the date and I could not forget the date. What it did not do was give me any idea of how much power was left in the batteries.

With rechargeables I no longer have that problem. They are fully testable. Kind of like analyzing the gas in your tank.

 

[stuartv]

IMHO, alkaline cells are cheap, readily available almost anywhere in the world, and reliable, so I'm in the "throw them away once every six months camp".

If I had a light that sat for 1 or 2 months with alkalines in it, I would want to open it up and inspect the batteries before taking it on a dive. Just to make sure no battery sprang a leak while it was just sitting. Just verifying that it turns on is not good enough, I don't think. And if I'm opening it anyway, why not just go ahead and put a freshly charged rechargeable in there that I know is good?

It may sound like I'm trying to change your mind or rationalize my own approach as superior. I'm not. I'm just trying to view both sides of the coin (in text form). I would trust a new alkaline battery without testing it. But, I've seen alkaline batteries leak after sitting for a while, so I'm just not inclined to trust ones that have been sitting for more than a month or two. I wouldn't trust rechargeables that have been sitting a month or two, either.

I suppose if I still had a Shearwater computer, I might be more inclined to have lights that also used AA batteries and just keep a big pile of alkalines on hand. But, my computer has to be charged every few days, so I won't be traveling anywhere to dive where I can't run a charger anyway....

 

[PfcAJ]

Do you test you "new" batteries? Do you have a process that makes sure you replace them EVERY 6 months? Sounds a bit like a "trust me dive" approach?

Personally, I check the voltage when I open the package, write the date on them with a sharpie, and update the excel file that has service dates of all my gear in it (and there's a lot of gear).

 

[KeithG]

I would trust a new alkaline battery without testing it.

By "new" I assume you mean "from an unopened package". Any idea how long the package has been sitting there? Especially if you are in some remote backwoods place? Has it been stored properly?

Sorry if I appear to be fixating on this. But this approach to "use new alkalines, they'll be fine, trust me" seems very similar to the approach most people used to take in regards to the (unknown) gas in their tank.

Technology has moved on. We have means of testing gas and batteries.