Lithium- based jump starter/battery packs

[kalniel]

So these are a thing - portable battery packs containing 12amps or so at 12V, designed to jump start a car with a dead battery and also charge phones etc.

See AE review of some here:
http://www.autoexpress.co.uk/accesso...rter-pack-2015

But would anyone actually recommend them? They seem to be largely rebranded imports, the insides of which from some you tube videos look quite scary. I'm not sure I trust a lithium-polymer pack to be anywhere near the alternator output of a running engine without some very reliable cut offs.

[peterb]

12 amps isn't going to do much to crank a cold engine.

That aside, I'd tend to agree with you about LiPo batteries, although it partly depends on the construction, but they do delivery a large instantaneous current, so if the output is shorted, they will be a very large bang, an arc, and probably a LiPo fire shortly afterwards.

I would hope that there is some form of protection built in, but it may be a vain hope.

Early versions of these used sealed lead acid cells, which did the job for a few times, until the abuse resulted in failure of the sealed cell.

Again, depending on the precise chemistry, LiPo cells have a nominal voltage of 3.7v, with a maximum of 4.2v (and a fairly flat discharge curve after the initial drop). A 3 cell batter at 12.6 V is probably just about OK, but it will soon drop to below 12, which may be a bit low.

The quoted number of charge/discharge cycles of 1000 for one unit seems wildly optimistic to my mind, especially if used for engine starting. 10 or 20 if you are lucky.

And bottom line, these aren't much less than a replacement lead acid cell, so if you think your battery is on the wavy out, get a new one!

A bit gimmicky to my mind.

[kalniel]

Sorry, 12Ah capacity, they can peak at around 400A for the cranking.

Agree about replacement battery if on way out, I came across them while looking into battery packs for phones, because people have quite obviously figured out if you're putting a battery pack for emergencys in the glove box, why not add some clips to it in case you have to start a car over a winter/light on moment. (Not an issue for my car, but wifes beat up Ibiza goes a bit funny at times and struggles to start - no-one has ever found any issue with holding charge though :/ )

[DanceswithUnix]

12 amps isn't going to do much to crank a cold engine.

I presume that is 12AH capacity, not 12A current rating. That should be plenty to get a car started, but you are right a lead acid that has been completely discharged is a dead lead acid so a device like this is only really a good idea to get you to the nearest car parts shop.

Edit to add: Looks like I need to type faster

[DDY]

I bought one from Costco some time ago for about £60 to keep in the car for emergencies, I've yet to use it on my own vehicles but it has twice saved stranded strangers.

First in a C3 and second in a 206, the former had a battery that could barely even turn the starter motor, using the lithium jump starter, the car fired up on the first go and that's after the jump starter had sat in my boot for 8 months.

There isn't any electronic protection on my jump starter, I think there is a bank of chunky diodes inline on the red jumper lead to prevent RP, but certainly nothing stopping the thing from shorting. On the bright side, the lack of any electronic gizmos means I could use the jump starter as a regular battery pack for some of my projects that require a fair bit of current.

[abaxas]

If your battery is flat there has to be a reason why.

Solve that instead of wasting money on things like this.

[kalniel]

If your battery is flat there has to be a reason why.

Solve that instead of wasting money on things like this.

Operator error? Doing too many short journeys and the temp hits -10 overnight?

It'd be nice if we didn't have to have seatbelts, crumple zones and airbags, but they all come about because of unplanned for reasons.

[Bagnaj97]

I currently use one of these to power my telescope mount, but whilst it's nominally 17ah I can't use all of that without flattening it - not good with a lead acid battery.

I've been considering hacking something together with a deep discharge leisure battery so I don't have to worry about killing it, but I wonder if one of these lithium packs would be a better idea?

[DDY]

I currently use one of these to power my telescope mount, but whilst it's nominally 17ah I can't use all of that without flattening it - not good with a lead acid battery.

I've been considering hacking something together with a deep discharge leisure battery so I don't have to worry about killing it, but I wonder if one of these lithium packs would be a better idea?

It's a bit of a faff charging lipo packs, but I find it's a good way of powering stuff out and about. Look in to DC-DC converter modules which can be found cheaply off ebay, Hobbyking is a good place to look for lipo packs, chargers and alarms which warn you if the battery levels are low, to prevent deep discharges.

[Butcher]

Operator error? Doing too many short journeys and the temp hits -10 overnight?

It'd be nice if we didn't have to have seatbelts, crumple zones and airbags, but they all come about because of unplanned for reasons.

Not to mention the first warning that your battery is on the way out is usually when your car won't start.

[peterb]

It's a bit of a faff charging lipo packs, but I find it's a good way of powering stuff out and about. Look in to DC-DC converter modules which can be found cheaply off ebay, Hobbyking is a good place to look for lipo packs, chargers and alarms which warn you if the battery levels are low, to prevent deep discharges.

If these are being sold as consumer devices, they should have an appropriate charger built in. Charging LiPo batteries requires a specialist charger, otherwise at best they are damaged, at worst, they catch fire.

[abaxas]

Operator error? Doing too many short journeys and the temp hits -10 overnight?

It'd be nice if we didn't have to have seatbelts, crumple zones and airbags, but they all come about because of unplanned for reasons.

Get to the root cause instead of trying to stick a plaster on it.

£60 is better spent on either a new battery or a decent conditioner/charger or maybe ever both.

[DDY]

If these are being sold as consumer devices, they should have an appropriate charger built in. Charging LiPo batteries requires a specialist charger, otherwise at best they are damaged, at worst, they catch fire.

Nope, they're bare lipo packs with nothing more than a few leads and shrink wrap holding the lot together.

Funnily enough, it's exactly because of the 'special' charger which makes it a faff;

http://www.hobbyking.com/hobbycity/s...CEL_manual.pdf

Of course, charging is done under supervision with a precautionary grope of the battery pack to check its temperature every so often.

[peterb]

Nope, they're bare lipo packs with nothing more than a few leads and shrink wrap holding the lot together.

Funnily enough, it's exactly because of the 'special' charger which makes it a faff;

http://www.hobbyking.com/hobbycity/s...CEL_manual.pdf

Of course, charging is done under supervision with a precautionary grope of the battery pack to check its temperature every so often.

Oh yes, I appreciate your DiY device is, I was talking about the one Kalniel referred to.

I have that self same charger, although I tend to use Hi-Tec H4 that will charge four packs simultaneously.

[DDY]

Oh yes, I appreciate your DiY device is, I was talking about the one Kalniel referred to.

Ah right, it was just 'these' that threw me off!

[bledd]

If your battery is flat there has to be a reason why.

Solve that instead of wasting money on things like this.

Meh, it's only £30 more than a good set of jump leads and you don't need a donor car.




Battery issues tend to present themselves once it's too late!