Jump start battery from the RC world?
 

How about this for a ultra-light jump-start backup battery?
Apparently this crazy 8Ah battery has a 40C (40 x capacity) burst current rate, meaning it could deliver 320A to the starter for a few seconds.
And it only weighs 0.64kg!

http://www.hobbyking.co.uk/hobbyking...arehouse_.html


Beats the price of these,

http://www.cnet.com/news/pocket-sized-jump-starters/

Although I'd like to see a nice compact capacitor based hand-crank jump start pack?
(not that I ever needed one for the D2, even with a almost dead 8 year old lead acid battery it still started eventually)

I have a 4 cell version of one of these in the starter box for my toy car's .21 cubic inch engine! The big problem with lipo batteries is you really don't want to deep discharge them - they don't like it and tend to swell up before self igniting!

Although the current draw capacity is ace the storage capacity will soon be used trying to start anything of a decent size

Li-fe cells are slightly safer as they will take a deep discharge and I use them for in car electrics - they don't mind a bit of knocking about either :)

yes the general rule of thumb is to not discharge them below 80% although several guys in the States on Rcgroups discharge them down to 3.0V which is close to 100% and apparently they haven't had any longevity issues. This is with a very low % of capacity current I'm guessing.

The 8Ah one should be able to deliver 3600x8x0.8/320 = 72 seconds of 320A
Although it wont live at 320A for long and may heat up and burst if used for too long at that sort of current. Starting a car should only take 5 sec max so it should be fine, unless the car asks for more current than 320A.

p.s. - Lipo only overheat if over discharged by a high current. I killed a few, one 850mah, with a low current of 3A all the way down to 0.0V with no drama, no heating at all.

I have one of these and they are amazing it’s about the same size as my phone iPhone 7 Plus but thicker, very lightweight it starts my car no problem, even if the battery is that flat that there is no sign at all of life! And only £29.99 my friend has been using a similar make for over 12month in a garage and found these cheaper ones that are the same. If it helps you once it could pay for itself.

https://rover.ebay.com/rover/0/0/0?m...2F272343099971

When I picked up the "project", the previous owner was an electric RC enthusiast and had a number of those batteries.
We had an idea to power the drivers window up using one, for the journey home on the truck. (Really should start a project thread on this one...)
Didn't end up doing it, but they certainly look promising as a jump start pack. You still have to manufacture a method of plugging it into the battery.
320A is plenty. Most jump packs that claim 300-400A rarely get above 200 anyway and I've started the S8, two different 4.0 L6 Falcons, and a 4.5 L6 Nissan Patrol on them.