BATTERIES! How many types do you carry?

[Litehiker]

OK, we are in the digital age and many of us carry a GPS, digital camera, Steripen UV water purifier, LED flashlight/headlamp and maybe even a Burris LRF Eliminator rifle scope.

SO... do you carry batteries for all or most of these now "essential" devices?
If so are they lithium batteries or rechargeable Li-ion or NMh batteries?

Lithium batteries are the lightest, longest lasting and do best in cold weather and that's why they are my choice.

 

[HarryN]

I use a couple of types for ALL of my battery uses. Size wise, it is nearly all AAs now, but I do have a few things that use CR123s.

For higher power (as in kilo lumen) class flashlights, I use rechargeable AA NiMH, but that is just for around the house fun. They can do the job, and are lower risk than R Li types. You really have to pay attention to R Li type batteries and I don't trust my wife or kids to do this adequately.

For pretty much everything else I use AA Li primary energizers. When needed, I have adapters to go to other lights. There is nothing else similar on the market for the average consumer. I keep a stock of them.

I used to make custom LED flashlights (as a serious hobby) and what I learned is that it is really handy to have devices that can take both primary and recharge type cells. The recharge cells typically won't hold a charge that well, and the ones that do will not self balance.

If you are going on a 2 week trip, then it does start to get interesting to think about a solar panel + charger, but at least for me I would not do that without something to carry it (like an animal or ATV)

 

[Litehiker]

Harry,

A few questions since you are well acquainted with batteries.

1. How about Li- ion batteries for rechargeables? (If available in certain sizes.)

2. What are "self balancing" batteries.

I know that headlamps with regulated circuits do better with lithium batteries. I assume this would also hold true with Li-ion batteries.

 

[HarryN]

Batteries charge, hold charge, and discharge at different rates. Surprisingly, this is true even if the exact same cells are used every time, in series, in a device.

Over multiple charge / discharge cycles, one cell can easily end up fully charged, while another is only at 50% charge. If the cells are in series, the flashlight will still go dead after the 50% charged cell is empty, which is annoying.

If you keep trying to use the light with cells in series, and one is substantially lower, the cell can go into "reversal" and be ruined. For NiCd and NiMH, this is just annoying, but not dangerous.

If the cell is Li ion or LiPO, and it goes below its minimum voltage spec (even if not gone into reversal) it can be internally damaged. 2 -4 charge cycles later, it can fail catastrophically and the fumes are really bad for you. This is why you charge Li based cells in a steel bucket with sand - outside. They even sell "charging bags" for them.

If the cell actually goes into reversal, it nearly always will fail catastrophically. There are some other ways things go wrong as well, but maybe that is enough to make the point.

In order to reduce the probability of this happening, devices (like your phone, computers, etc) which use them have a number of safety features, for example:
- Temperature monitoring
- individual cell discharge voltage monitoring
- individual cell charge voltage monitoring
- Max discharge rate fuses
- over discharge voltage trip sensors (per cell)
- Ability to charge / slightly discharge individual cells in a pack during the charge cycle

This is why we can all safely use Li ion and LiPo cells in our daily lives, they are "nearly fully protected" and there are companies that make dedicated chip sets for this specific purpose.

 

[HarryN]

If you are going to use Li ion batteries in your devices and charge them, then I suggest reading something like R/C forums for a while and make sure you are really comfortable with the cells.

They are great performance wise, I just could not get my wife / kids to take them as seriously as I thought was necessary. Once my wife realized the effort, she rejected the concept as too much work. Probably she was right for her intended use, or maybe I am just OCD.

Plan to spend at least $200 on a quality charger or don't do it at all.

Most of the NiCad and NiMH will discharge / lead down a bit within a few hours of charging them up. This has the effect of sort of self-balancing a pack, or cells in series, so there is hardly ever problem as long as the cells are in good condition.

The exception to this is the Sanyo / Panasonic Enloop cell. Their advantage is that they have very low self discharge. Unlike normal NiMH, the charge holds a long time. This also means that it is more important to charge them correctly as they will not self balance.

 

[HarryN]

The best known Li ion cell is the 18650 size, which is nominally 18mm diameter x 65mm long. With the protection circuits, they can be physically slightly longer. Charged voltages tend to run about 3.5 - 4.2 volts, depending on the exact chemistry used.

There are AA size Li Ion cells, but they are also similar voltages vs. the traditional AA cell which is closer to 1.2 - 1.7 volts.

There are some D size Li Ion cells on the market, but for safety reasons, the FAA restricted the amount of Li per cell, so I don't know if these really perform as expected or not.

 

[HarryN]

The LED headlamps usually use drivers (led power regulators) with an input max at 5 volts. For that reason, you tend to find these with either 2 x AA (so max under 5 volts) or 1 x 18650 (so again, under 5 volts).

Usually, the 3 x AAAs are a more simple design (battery / resistor / led). They work well for that price point, and I have made some, just not quite as efficient and AAA cells are a poor value for the amount of provided power.

C123 (primary) and CR 123 (charge type) batteries are both in the 3 - 4 volt range, so that can make for a useful potential combination of primary and rechargeable cell. The 123s have similar lifetime, cold weather performance, and total power of the energizer primary Li. It is perhaps the most useful consumer cell out there for this reason. On line, you can get several good brand name primary cell C123s for reasonable prices, example surefire, streamlight, rayovac, Duracell, etc. Much cheaper than in the stores.

Spend some time reading about recharge type 123s though to make sure that the one you are using really is fully protected. I toss them after 5 cycles even though they are rated at 100s, just to error on the safe side. They are cheap enough that it doesn't matter, and unlike brass, you cannot tell what is going on when re-loading.