Thread: Lithium Jump Starters

Originally Posted by LRD414

That’s a good option. So is that connected like the rough sketch attached?

Spot on. The light bulb is a non-ohmic resistance with a very high temperature coefficient, so it'll pass way more than 4A at low differential voltages while the filament is cold. If the car draws too much current the filament starts to heat up and its resistance rises limiting the current.
I've never bothered to try and characterize it. It's just the first time I needed to do it I happened to have a spare H4 in the tool box and it did the job.

One of my "get out of jail free" cards. A bit like the time I boosted my Volvo using 3 Duracell 6V lantern batteries in series. They have a relatively high internal resistance, so that was no worries. Just enough to put a surface charge on to get it going. Took about 20 minutes to put a sufficient charge in. The Ryobi does it in about 10. One of those things, the longer you wait the better the outcome is likely to be, and if you're in the middle of nowhere it's a good outcome you want!

Of course the second time I did it the results were not as good. Might have had something to do with me forgetting to turn the park lights off though.

Originally Posted by BradC

Most of them (like all the ones I've looked at) work by putting a very fast surface charge on the battery. Works great for a good battery gone flat, but not so much for a genuinely dead starting battery (like dropped one or more cells/high internal resistance).

I do the same thing with a ryobi one+ 18V battery. Put it in series with a 55w headlamp bulb and onto the dead battery. The headlamp bulb provides enough resistance to stop the ryboi tripping out on overcurrent and quickly puts a surface charge on the car battery. I always have at least one ryobi battery in the car.

My thanks to everyone who has responded to my query.

Brad I am almost a complete ignoramus when it comes to batteries so are you able to provide a bit more information as to exactly how you connect up the Ryobi battery to the cranking battery please? I assume that a 2.5Ah Ryobi battery would do the job, assuming that the cranking battery was not stuffed? Thanks

Originally Posted by rsp

.... bit more information as to exactly how you connect up the Ryobi battery to the cranking battery .....

It’s in the sketch I put a few posts up.

Scott

I have a Projecta lithium jump starter which cost about $200 and works just fine. Recently I used it to start a car whose battery was totally flat. I connected it, left it connected for about 10 minutes and then the car started. This was in Glen Innes in freezing cold weather. It also starts my Defender no problems.
I love it. It's compact, powerful and can charge phones and run LED lights. It lives in the drawer in the Defender. Great stuff! Buy one, you won't regret it.

This is another interesting & informative thread that while not having a need for a device has puzzled me how a stupidly small battery can start a car with a flat battery.
Minds eye I could only imagine an exploded battery & not having gone into this previously didn't realise it was only a surface charge that was being used & not the Lithium battery as the main cranking battery. Deeeeerr.

Thank you for this thread.

It also means I need not carry a 500 km extension lead back to my shed to use my normal battery charger.

BTW, this thread seems a hell of a lot easier to follow than Wiki wottsit.

Surface charge - Wikipedia

Here's a picture of my Projecta lithium starter. I put the roll of tape there for a size comparison. They come in several sizes.

I got this one as a freebie when I bought an iTechWorld 5KVA generator last year. They’re about $200 as a stand-alone purchase. Incredibly versatile gadgets. Had an earlier version a couple of years ago which started my TDV8 4.4 L322 easily. This one will also run my 40l Engel for several hours. Amazing bit of kit.

EDAE5359-B61D-4AE3-874C-806057BB4D6F.jpeg

Originally Posted by GregMilner

I got this one as a freebie when I bought an iTechWorld 5KVA generator last year. They’re about $200 as a stand-alone purchase. Incredibly versatile gadgets. Had an earlier version a couple of years ago which started my TDV8 4.4 L322 easily. This one will also run my 40l Engel for several hours. Amazing bit of kit.

EDAE5359-B61D-4AE3-874C-806057BB4D6F.jpeg

Same unit as my old man has that I mentioned up in post #7