I apologize for bumping this old thread, but I would like to share my experience in this matter, since when I was looking for good advice on this topic for myself

Personally, I'd prefer a larger capacity Li-ion bank like Xxxx even on foot. It'd be pretty disappointing to not have your jump pack have enough capacity when you're broken down on a cold night.

I don't have the data and calculations on hand, so I don't understand how a small capacity battery at 12.6v gives a sufficient boost to a dead battery. Eventually, they equalize, but that's not the main issue, it's that your 12.6v battery is reduced in voltage by the dead car battery (although it may give it some usable amperage). Semi truck starters operate down to 10.5 volts just fine, whereas a ninja 250 will have too slow RPM to start at 12.2 volts, so it also depends on your starter, temperature, oil weight, and engine size.

I could see if the battery had just started to get too weak, then you just needed a few cranks. But I've been caught many cold mornings where having the ability to crank for a whole minute is really what is needed, if your valves are maladjusted, water in your gas tank, ran out of gas, gas filler neck breathing hose is clogged, glow plug circuit malfunction, etc.

You wouldn't necessarily have to remove and replace the battery. What you could do is take your jump pack, a small car battery, or a 12.6v bank of some old laptop batteries soldered together, and wire that in parallel with your main battery, with a disconnect switch. Li-ions have the advantage of retaining 70%+ voltage over a year, and do better in the cold, according to this graph comparison. The idea definitely has merit and I'm not trying to bash it, just commenting on some possible improvements and possible scenarios it could be used in. Link deleted.

Edited by Avant on 14/09/2018 at 23:59

"Why are my suspicions aroused?"

Your suspicions are aroused probably because of the clickable link. (Don't expect that to last long, Meroll!)

Edited by Avant on 15/09/2018 at 00:00

(more names from the past above - most of which never to be seen here again...)

(or should that be "most of whom"?)

But allow me ask the question - who would buy a battery starter pack (or whatever it might be called) ? and why would they buy one? Having never used nor owned one I have zero knowledge of them. I would gues the money is better spent on a new battery if the present one is of a certain age or is showing signs of weakness, but presumably there's a market for them if you can still buy them?

I don't carry jump leads any more coz I fear damaging the electrics of either the donor car or the recipient vehicle ... which is unfortunate as I have two pairs of really stout cables languishing in the shed. But I do subscribe to AutoAid just in case it all goes wrong in some remote spot.

Don`t forget those that have battery/charging problems, and will not pay out to have them fixed, they would rather buy a booster pack and suffer the problems untill they get to breakdown point

I know someone like that who waits untill the problem causes a breakdown before (after moaning about the costs) gets the problem looked at, where if they had sorted it out before they wouldn`t have broken down. the cry then is they cannot/will not... afford it

I'm still not sure why - or when - you (not "you" obviously) are supposed to carry these things.

Obviously I understand the principle of jump leads - and, as mentioned above, am wary about using them nowadays for the reasons we all know about. But the "traditional pro type booster pack" is presumably big and heavy and, equally presumably, has to be kept charged in some way? ... and might only get used once or twice in the average driver's lifetime.

Although I've never seen one, I fully accept that a compact gadget that plugs into a ciggy lighter isn't likely to be any more use than a choccy fireguard when a battery is completely flat (and probably worn out).