Using rechargeable batteries in a backup light?

[Lorenzoid]

I saw a mention in a GUE thread about not using rechargeable batteries in your backup light.

I'm glad you posted this, as it's a question I had been planning to ask my GUE instructor before buying a set of quality backup lights. I suspect, as others, that it's something GUE just hasn't yet taken the time to look into whether it needs to be updated. Then again, they do update things in the Standards manual, and yet this bit about "alkaline batteries" in backup lights is still (2015) in there.

. . .
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.

That's what I have been doing.

 

[stuartv]

I'm glad you posted this, as it's a question I had been planning to ask my GUE instructor before buying a set of quality backup lights. I suspect, as others, that it's something GUE just hasn't yet taken the time to look into whether it needs to be updated. Then again, they do update things in the Standards manual, and yet this bit about "alkaline batteries" in backup lights is still (2015) in there.



That's what I have been doing.

I think it was your other thread that prompted me to ask. I started this thread instead of derailing yours.

 

[stuartv]

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.

I hear you. You make a totally valid point. And I guess, really, I said that but the point is moot (for me). I don't own any dive gear that takes AA or C batteries. My Atom takes a coin battery, my other computer has a built-in rechargeable battery, and all my lights take 18650s or 26650s.

 

[KeithG]

My Atom takes a coin battery...

oops?

 

[stuartv]

oops?

Huh? My Oceanic Atom 3.0 computer takes a regular wrist watch coin battery. Nothing to do there but check the battery status on the computer and replace it as needed, then let the computer tell me that the new battery is okay. I've had it for over a year and half. I replaced the battery once and the current battery status still shows good.

Am I missing something here?

 

[fmerkel]

18650's and the like are Lithium Polymer batteries. They hold charge for long periods and are good for hundreds of recharge cycles if well treated. (As evidenced by phone batteries.)
However they have different characteristics to Ni-Cad or Ni-Mh rechargeable batteries.

The key points with Li-Po batteries are to always use 'protected cells', buy quality cells (NOT Ultrafire), use a quality charger designed specifically for Li-Po batteries and NEVER run them too flat.
Discharging these cells to below three volts damages the chemistry of the cell and can turn them into firebombs during the next charging cycle as evidenced by the spate of 'Hoverboard' fires in recent months. If you see the light start to dim in your flashlight - immediately turn off the light and check the battery voltage with a multimeter before recharging. If below 3v - recycle the battery and buy a new one!

There's some small errors there, though the general content is good:
They are mostly Lithium Ion (Li-on). There are several different chemistries of Li-on. Lithium Polymer (Lipo) are the soft package ones like radio controlled people use.

Protected cells (PCB) are not critical to have, but the requirement for knowing how to handle over and under charge fall completely to the user without them. In general a PCB cell will be safer than a non-PCB cell. Be aware that not all PCB protected cells are 'safe'. Just like there are junk Li-on cells there are cells with junk PCB on them.

The Anatomy of a Protected LiIon Battery

The Hoverboards probably had junk cells, junk charging circuits, and junk protection circuits.Hard to tell for sure what was bad.

Discharging a Li-on to 3.0v (single cell) will not automatically turn it into a bomb. They are far more robust than that, assuming it is a decent cell in the first place. In fact most PCB protected cells have a cut-off somewhere in the 2.5-2.8v range. I don't recommend you discharge your cells that low as it does do some harm, which accumulates over time. My recommendation is to not take them below 3.2v, and not store them for prolonged periods at full charge. Store at cool temperatures. Damage also occurs when the temp gets over 140*F (storage in a hot car, charging with a bad charger with poor air circulation).
Great article on over discharge - worth reading:
How far can LiIon be discharged?

As bergersau states, when using a lithium powered device, as soon as the device shows a distinct power drop cease use immediately. This is even more important if the device has multiple cells as there is always a 'weak' cell and the others may support the device function but that weak cell may get seriously over discharged. This is where PCB protected cells are very useful.

DO NOT BUY ULTRAFIRE BATTERIES OR PRODUCTS, NO MATTER HOW CHEAP !!!!!
If a 18650 cell claims to have more than 3500mA capacity it is guaranteed junk. There is no such thing.

 

[kensuf]

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?

Yeah to the first two questions, no to the third. I voltmeter them before installing them and I swap batteries in my backup lights out every 4th of July and every Christmas. That's close enough to a six month window for government work, and those are pretty easy dates to remember. I'll also usually do a "burn test" on one of the old batteries when I swap them out, just to verify what I'm anticipating meets reality. It looks like this:

Previously I used to swap them out at daylight savings time change since I had to change my clocks anyway, but I changed to the Christmas/4th of July when they moved the time window for DST.

 

[tarponchik]

You are not staying under long enough...

But seriously, you went through 2 sets of batteries in 1 dive trip. How can that be economical? I figure a set of rechargeables is good for at least 4 years with no issues. I still have a handful of 10 year old rechargeables that are used on a daily basis (keyboard wireless mouse, laptop wireless mouse, tv remote, roomba fence thingy,...).

Maybe But recharging the camera and strobe batteries is enough hustle for me already. I think this is a reasonable compromise. I do not overload my baggage with packs of batteries and do not leave them as toxic trash in some small tropical island. Wasting a single 6-pack is OK.

 

[bergersau]

There's some small errors there, though the general content is good:
They are mostly Lithium Ion (Li-on). There are several different chemistries of Li-on. Lithium Polymer (Lipo) are the soft package ones like radio controlled people use.

Protected cells (PCB) are not critical to have, but the requirement for knowing how to handle over and under charge fall completely to the user without them. In general a PCB cell will be safer than a non-PCB cell. Be aware that not all PCB protected cells are 'safe'. Just like there are junk Li-on cells there are cells with junk PCB on them.

The Anatomy of a Protected LiIon Battery

The Hoverboards probably had junk cells, junk charging circuits, and junk protection circuits.Hard to tell for sure what was bad.

Discharging a Li-on to 3.0v (single cell) will not automatically turn it into a bomb. They are far more robust than that, assuming it is a decent cell in the first place. In fact most PCB protected cells have a cut-off somewhere in the 2.5-2.8v range. I don't recommend you discharge your cells that low as it does do some harm, which accumulates over time. My recommendation is to not take them below 3.2v, and not store them for prolonged periods at full charge. Store at cool temperatures. Damage also occurs when the temp gets over 140*F (storage in a hot car, charging with a bad charger with poor air circulation).
Great article on over discharge - worth reading:
How far can LiIon be discharged?

As bergersau states, when using a lithium powered device, as soon as the device shows a distinct power drop cease use immediately. This is even more important if the device has multiple cells as there is always a 'weak' cell and the others may support the device function but that weak cell may get seriously over discharged. This is where PCB protected cells are very useful.

DO NOT BUY ULTRAFIRE BATTERIES OR PRODUCTS, NO MATTER HOW CHEAP !!!!!

Thanks for correcting that - Li-Ion is what I should have said.

 

[fmerkel]

Was just at a local dive shop. There was a light in the instruction room (not part of their retail line), that I looked at while the clerk dealt with a phone call. It was an 800lm (claimed), twisty, single mode, 18650 cell light. There was a blue 2400mA cell and a red 5300mA cell in there. I brought the cells home and ran them through my Opus test charger. The blue 2400 = 2175 @ 0.5A draw.
The red 5300 = 875 @ 0.5A draw. (pathetic, some NiMh AAA can match that)

A draw measurement from the light was around 2A. So, blue battery is barely good for 1 dive. The so called 'high capacity' cell would last maybe 15-20 minutes. They aren't Ultrafire, but they might as well be.

A local instructor is selling these on the side and thinking he is doing his customers a favor by providing better batteries.
I have an email in to him now about this. I don't know him personally, but doubt he is trying to bilk his customers.