On Wed, 02 Dec 2015 13:33:06 +0000, Dave Plowman (News) wrote:

In article ,
Tim+ wrote:
Dave Plowman (News) wrote:
In article ,
Adam Aglionby wrote:
Again mate in commercial garage has li-on starter pack , size of a
paperback , just shy of 200 quid, on his second unit and third set
of leads on warranty...

What I'd guessed.

The majority will be bought as a 'just in case' and perhaps even as
presents. So they might well be able to replace the few that are
actually used more than a couple of times under warranty.

Like most things, if it sounds too good to be true, it likely is.

I'd say a pair of jump leads are better value as a 'just in case'.


But you're ignoring the fact that these are sold as power banks for
charging any number of whatnots. You might struggle to cover all their
functions with just a pair of jump leads.

The OP only asked about their use for jump starting.

As regards other uses, I find a lead acid jump start pack with built in
tyre compressor very useful. And does double up for the very rare
occasion I need a portable power supply.

Can't really think of where a much smaller one would be a killer reason
to pay out that much more money for. Except for specialised stuff like
model aircraft and so on.

If my experience with a 12AH SLA is anything to go by, that's probably
all you'd need (along with short 'jumper leads' - in my case, half a
metre's worth total).

I'd stopped off at our local chippy two or three winters back on our way
home from a 20 mile round trip outing. I knew the battery was on its last
legs but still made the mistake of switching the engine off on our
automatic 1.6 Astra whilst waiting for the missus to get served. It was
late afternoon and dark so I had the side lights on. When the missus came
back, ten minutes later, the battery was too flat to restart the car.

The emergency 1.4AH celled jump starter pack was, as expected, too flat
to do any good (NiCads eh? if you don't keep them on charge between use,
they're flat within a week or two from self discharge). Since we were
only 5 minutes walk from home, I decided to push the car into a parking
'bay' which had opportunely become free so we could head off home to
enjoy our fish 'n' chips tea and for me to put the 'emergency' starter
pack on charge.

After we'd had tea, I realised that unless I left the car parked where
it was overnight, there was no chance of the 'emergency pack' being
sufficiently charged to attempt even just a single starting attempt so I
cast around for an alternative 'battery' I could bodge into jump start
service and spotted the 2nd hand 12AH SLA I'd left parked on the office
window ledge ever since it had received its one and only charge from a
couple of 12v 1.2Wp solar panels the previous summer.

My initial test with a borrowed DMM in the fleamarket where I'd
purchased my "Five Quid Bargain"(tm) which had indicated a good state of
charge had proved to be optimistic - probably low battery in the borrowed
DMM - the battery voltage was only just over the 12 volt mark when I
measured it with my fluke DMM at home. However, despite this, it had
slowly charged up over the next few weeks of intermittent sunshine that
summer, reaching 14v before I decided 'enough was enough' - it doesn't do
an SLA any good to leave it floating higher than 13.8v for any length of
time.

Anyway, a quick test revealed it was still showing 12.77v and a 55W 12v
halogen capsule lamp lit up nice and bright confirming it might just be
up to the job so I made up my 'jump leads' and walked back to the car
with my 30 year old son in tow for moral support (actually, it may have
been that my son gave me a lift in his car, I can't really recall for
sure but he might even have had a set of jump leads to jump start from
his own car).

Regardless of whether I could prevail upon my son to jump start the
Astra, I attached my SLA to the car battery terminals and tried the
starter. Much to our amazement, the engine spun into life as if I'd
fitted a new car battery (I'd already tried an abortive start on the
car's own 'rested' battery - so knew the success was entirely down to my
"Five Quid Bargain"'s own efficacy).

I still have that battery and it still shows a resting voltage of 12.76v
some 4 or 5 months after its last annual 'summer solar charge' :-)

The point of this anecdote being that if a 2nd hand 12AH SLA flea market
purchase can jump start a 1.6 litre automatic, a new 12 or 15AH SLA might
be all you need to carry around in your boot in between 4 to 6 monthly
freshening charge cycles (along with a set of short jumper leads with
spade connectors for the battery terminals).

If you're going to trawl your local flea market or boot sales for a
decent SLA, take your own DMM (or at least a fresh PP3) to check any such
prospective purchase. :-)

--
Johnny B Good