On Sunday, October 22, 2017 at 1:07:26 PM UTC-7, Ian Field wrote:
"Jeff Liebermann" wrote in message
...
On Fri, 20 Oct 2017 21:40:42 -0700 (PDT), Sir Ridesalot
wrote:

A while back I asked about using an external NiMh battery instead of an
external
Lithium Ion battery on a light that came with a Lithium Ion battery. Due
to a
problem with the Lithium Ion battery pack of mine not holding a charge or
for
some other reason battery related for the light suddenly going out I put a
Tamiya connector onto the light's wire and used my NiMh battery. Guess
what?
It works perfectly and my battery run time is a LOT longer now than what
it was.
Seeing as I have a few of these 5000Mah NiMh batteries from my RC boats I
can
now ride VERY FAR at night with no worry about the light going out
suddenly
or dimming drastically at low speeds or when stopped.

My guess(tm) is that there is either something wrong with your LiIon
battery pack, or the LiIon battery pack was assembled using cheap junk
LiIon cells. I've seen both, mostly from 18650 cells. Identifying
counterfeit cells is difficult:
https://batterybro.com/blogs/18650-wholesale-battery-reviews/104619270-can-you-identify-the-fake-lg-hg2-18650-battery
I used to weigh the cells and compare them with a known good cell, but
that hasn't worked since the counterfeiters started adding waxes sand
to the cell to increase the weight.

All my 18650s were rescued from discarded laptop packs - if I get any duds,
there's no point complaining to anyone.

The 3W Tesco headlamp uses one, but my biggest application is my e
cigarette. That's been in service well over 5yrs and I've only had to swap
out a couple of battery sets.

The one that came with the Tesco unit is only 1800mAh - I get a lot more
running time from salvaged cells.

Laptop battery packs used to be great sources for core cells. The big laptop battery recall in 07-08 sent case loads of new packs to large companies. Problem with the packs that was causing fires was cheap charging controllers, and poor design that put groups of three cells in parallel without regulating charging between each cell. That resulted in some cells being forced to absorb power beyond safe charging capacity if one cell was substandard or dropped off a tenth of a volt after many charges.
Instructions were given NOT to return old packs, to dispose of locally. That gave me a huge harvest of 2800 Samsungs and Panasonics from Lenovo and Dell packs, for my early lights.