# Rechargeable batteries for flashlight

#### electronewb

Joined Apr 24, 2012
260
I bought this flashlight a few days ago. Either you can power it from the power supply or you can put "rechargeable batteries" in it. The problem is what kind of batteries!! I called the company and they don't know. And the manual has about 3 lines and doesn't mention the type of rechargeable batteries needed.

The best results I got so far is with rechargeable Alkaline batteries. I drained them to around .4V and was able to recharge them with the flashlight to 1.1V but at 1.1V that's around %20 less power than with the power supply or non-rechargeable alkaline batteries. How come I cannot recharge them to 1.5V? I've attached some pix (the black strips on the flashlight is just grip tape since the case is very slippery).

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#### bountyhunter

Joined Sep 7, 2009
2,512
Rechargeable alkaline batteries are a scam. They don't recharge to anywhere near full capacity.

Use NI-CD or NI-MH. Even though the cell voltage is lower, the light will probably be brighter because lower internal cell impedance (so less wasted voltage drop). You will likely need to add a series resistor to limit current from the wall wart.

#### crutschow

Joined Mar 14, 2008
23,487
Recharageable alkaline batteries do not like a deep discharge as noted here. The work best if only partially discharged.

Typically NiMH recharageable batteries are used in flashlights.

#### bountyhunter

Joined Sep 7, 2009
2,512
Yeah, I worked at NSC back when they trotted them out around 1994. They wanted us to do some charge IC's pro bono because they would be a "big seller". Took me five seconds to smell the scam. They can only be recharged fully as long as you don't discharge them..... seriously the stupidest product concept I had seen up to that time. They died a quick death in the marketplace but some company has trotted them back out again as a "green" solution. You can always shear the sheep as long as a product has a green leaf on the label.

here's why the concept of "rechargeable" alkaline is bogus:

The idea of recharging alkaline batteries is not new. Recharging these batteries is only effective, however, if the cells have been discharged to less than 50% of their total capacity. The number of recharges depends solely on the depth of discharge and is limited to a few cycles at best. With each recharge, the amount of capacity the cell can hold is reduced.

The reusable alkaline is inexpensive to buy but the cost per cycle is high when compared to other rechargeable batteries. Whereas nickel-cadmium checks in at $0.04US per cycle based on 1500 cycles, the reusable alkaline costs$0.50 based on 10 full discharge cycles.
http://batteryuniversity.com/learn/article/will_the_reusable_alkaline_battery_have_a_future

#### electronewb

Joined Apr 24, 2012
260
Second test I put 3 Enloop batteries I had to look online for what type of batteries they are since it doesn't say on the packages they are NiMh batteries the think is I found them in a drawer and probably haven't use them in over 3 years!!