[Shop-talk] Cordless tool battery packs - the current state

[John Innis]

You can't really convert a ni-cad or nimh pack to Lithium easily  or
cheaply.  This is because with micad or nimh, you can just change all the
individual cells in the pack in series.  But to properly charge a lithium
pack you need to balance each individual cell.  For an 18v tool there are 5
cells in a pack and the charger needs to monitor and adjust each cell to
keep them all balanced.  So instead of 2 contacts between the battery and
charger (+ and -) you now need 7.  One way around this is to put all the
balance charger circuitry into the battery pack itself.  This makes the
battery pack heavier and more expensive, taking away any advantage of using
lithium batteries to begin with. When you buy a replacement pack that has
(or is supposed to have) lithium batteries instead of nicad, you really
don't know what is in that pack.  Does it really have lithium batteries?
Is there a built in balance charger?   Also lithium batteries (especially
cheap ones) occasionally bust into flames.  Not having a balance charger
increases this risk.

On Fri, Feb 3, 2017 at 10:31 AM, Matt <mbarre at juno.com> wrote:

> I have 2 questions for this august body, but for simplicity I will break
> them up:
>
> Time to repower my fleet of Porter Cable 18V tools.
> I have seen over the years the various options to rebuild the battery
> packs and it looks like there are services and do it yourself packs that
> are already assembled for the DIYer to put into their plastic housing.  THe
> rebuilder folks claim they use quality batteries and they produce better
> packs.
> EBay seems to have plenty of "new" options as well, mostly from China.  I
> currently have nicad chargers but the availability of dual nicad or li-ion
> widens the options.
> I don't use these every day, or even every week, but a couple of times a
> month I am working on something.
>
> Any guidance from the group re nicad vs li-ion.
> Off the shelf vs US rebuild or battery pack?
>
> Thanks!
> Matt in GA
>
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