In article ,
"Norbert Thistlethwaite" writes:


"Andrew Gabriel" wrote in message ...

I use one of the portable jumpstarter packs with a built-in sealed
lead acid battery and compressor. The trouble is finding a good one;
many of them are complete crap, and have fake batteries which are a
tiny fraction of the capacity which their size and markings claim,
and some of the compressors and tyre valve couplers are crap too.

I bought a Clarke 910 jumper/compressor, after about 2 years, I was unable
to charge the unit.

Lead Acid batteries need care.
Stick one on the shelf for 2 years, and it will likely be
dead, especially if it wasn't fully charged to start with.
I always try to recharge mine as soon as possible after use.
Flattening one is bad news too, for its longevity.
You need to periodically top it up, but overcharging (as
some of the cheap chargers which come with these can easily
do) will also wreck a SLA battery. I usually charge mine
from an accurate voltage and current limited bench supply,
and never used the wallwart which came with it and has no
voltage or current limiting (other than its own internal
resistance). Some come with crap batteries, as I said.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]