https://www.halfords.com/motoring/battery-maintenance/jump-starters/halfords-advanced-lithium-jump-starter---up-to-2l-677444.html £48 with trade card. Sure I saw something like that (up to 2L jump pack) that fits in glove box and can be used as torch and it was less than £50. Yes I know that's far more than a set of leads but if your out in the middle of nowhere or early morning and no other vehicles to jump from then you can soon be on your way. IMO.
Nowadays, in an effort to save fuel, alternators do not charge all the time. Charging also comes from small generators on the wheels which activate when braking or slowing down (regenerative braking). Essentially the ECU calculates the charging current based on battery usage and current load. The end result is that the charging voltage will sometimes be as high as 15v - rather than the usual 13.5v in older systems. So when you connect another battery in parallel, the charging voltage will certainly hit the higher voltage. So your car may be OK with this, or it might not be. If you are happy to take the risk, go ahead.
I have a set of prof leads what cost me 60 quid, i've often used these on peoples cars after their 10,15,20 quid leads did nothing..... that said, better to have a 10 quid emergency set than nothing.... now, lets get to the biggest issue, your car turns over one morning very slow but starts, its great all day, but next morning it turns over slow again.... best to keep doing this until it won't start at all right? ;) seen it dozens of times...
Used it on a 2012 Vauxhall Zafira 1.6ltr and it jumped it fine
Ok, thanks (y)