Those mini jump start thingies...

[Hoofy]

The Spruce goose said:

i bought one off amazon for 30 quid, finally got to use it and....it didn't work..i suggest buy the expensive ones.

How do we know even those ones work?

[Magic919]

CABC said:

my DBPower unit is still at full charge even though it's been in the car for 2 months at sub-zero for much of the time where it sits. of course these are much bigger batteries than phones or cameras but those type of li-ion devices really suffer in cold temps. anyone know why the booster seems to hold charge better? is just size?

There's a difference between low temperature storage and low temperature performance.

[NickGibbs]

I've got a Junopower Jumper rated at 6000mAh. Peaks at 300A at 12v

Mostly used it on my motorbike, but last week it started a neighbour's dead Civic and only used a quarter of its power, which was pretty impressive.

[CABC]

Magic919 said:

There's a difference between low temperature storage and low temperature performance.

true, but whereas my phone shows low battery in the cold but then recovers in the warmth, the jump starter at least shows 100% when still cold.
maybe its power display is fooling itself.

[Magic919]

They can only really measure voltage and make a guess regarding capacity. You'd need to run a discharge cycle to get a better idea.

[CABC]

so i'm keen to keep it in good health. a quick google of "compact jump starter storage and recharge cycle maintenance" didn't help at first glance. any ideas on how to keeep these things good for when you need them? eg fully discharge/charge once a month?

[chopper602]

I've used mine to start my dead motorhome, with a 2.3 litre diesel engine and it did it with no problem. I tend to get mine out of the car boot about once every few months, check it over and charge it up (not that it needs it TBH).

[Skyedriver]

I have (had) a Clarke 9000 thing, big heavy and very reliable but it was destroyed a few months ago when I was using it to try and start the Volvo when the alternator was knackered and had a direct short.
It knackered the car battery too.
I bought an Energizer one from Aldi before Christmas (£49). Used it on the wife's Suzuki SX4 yesterday as the battery was dead after a long lay off. (and I used a tyre inflater, the damn radio was on and probably the heater fan as I cannot fathom out the controls!).
The Energizer started the car but not with the usual efficiency of a car battery.
Think I need something a little bigger for my use.

[SlimJim16v]

CABC said:

so i'm keen to keep it in good health. a quick google of "compact jump starter storage and recharge cycle maintenance" didn't help at first glance. any ideas on how to keeep these things good for when you need them? eg fully discharge/charge once a month?

I'm sure I read that lithiums don't like to be fully discharged, so best to keep it always topped up. Much like std lead/acid really.

[CABC]

SlimJim16v said:

I'm sure I read that lithiums don't like to be fully discharged, so best to keep it always topped up. Much like std lead/acid really.

Lithium hates both extremes, ideal is between 30-70% charge

[Hoofy]

Damn. That's not always possible!

[Jimmy Recard]

Hoofy said:

Damn. That's not always possible!

Plenty of batteries may say they're at 100% but they've kept the charge at a lower level. My Lenovo laptop does that for instance and maybe even most items we buy with rechargeable batteries

[Hoofy]

Jimmy Recard said:

Hoofy said:

Damn. That's not always possible!

Plenty of batteries may say they're at 100% but they've kept the charge at a lower level. My Lenovo laptop does that for instance and maybe even most items we buy with rechargeable batteries

I was thinking of the other side - your phone hits 0% and you don't have the opportunity to charge it for a day, for instance.

[Jimmy Recard]

Hoofy said:

I was thinking of the other side - your phone hits 0% and you don't have the opportunity to charge it for a day, for instance.

Just get it charged up when you can?

I'm guessing with decent quality cells a day or two won't have that much effect (especially if it's not happening a lot), but leaving it at 0% for weeks/months would bugger it

[DaveCWK]

If you fancy making a super cheap diy version, get a 4s lipo pack (1500-2000mah should do) from Amazon/eBay/banggood etc, an xt60 connector,a bit of 4 gauge wire & some spring clips.

[Mr2Mike]

DaveCWK said:

If you fancy making a super cheap diy version, get a 4s lipo pack (1500-2000mah should do) from Amazon/eBay/banggood etc, an xt60 connector,a bit of 4 gauge wire & some spring clips.

And a good fire extinguisher.

[Hoofy]

Jimmy Recard said:

Hoofy said:

I was thinking of the other side - your phone hits 0% and you don't have the opportunity to charge it for a day, for instance.

Just get it charged up when you can?

I'm guessing with decent quality cells a day or two won't have that much effect (especially if it's not happening a lot), but leaving it at 0% for weeks/months would bugger it

Damn. Thanks for the tip.

[HotJambalaya]

Well, I bought a high capacity one for £66 to jump the C63. Says it starts up to 8l, didn't think it was going to make it for a while, but after a bit of prodding and a couple of attempts, it started. Quite chuffed.

More annoyingly though I noticed an outdoor plug socket right next to my car just after I jumped it so could have actually charged it instead of jumping it, but oh well....

[eliot]

HotJambalaya said:

Well, I bought a high capacity one for £66 to jump the C63. Says it starts up to 8l, didn't think it was going to make it for a while, but after a bit of prodding and a couple of attempts, it started. Quite chuffed.

More annoyingly though I noticed an outdoor plug socket right next to my car just after I jumped it so could have actually charged it instead of jumping it, but oh well....

And that's a point lost on many people - rather than simply jumping a flat battery and driving it for 1/2 hour, you will do far more good giving it a long slow charge on a smart-charger overnight.

[Mr2Mike]

eliot said:

And that's a point lost on many people - rather than simply jumping a flat battery and driving it for 1/2 hour, you will do far more good giving it a long slow charge on a smart-charger overnight.

That misses the entire point of these devices; they are for situations where you need to get the car started quickly.