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[TheBoy]

As I have outlined in a previous thread, it is possible to recover from this low-capacity state due to being left discharged - IF it'snot a sealed or gel battery.. Messy procedure, involving emptying the acid out (and saving it), replacing it with distilled/demineralised water and repeat charge-discharge cycles several times. I suspect it ain't worf the effort, though!

Ron.

And repairing the plates? How?

[Bigron]

Nothing can replace active material shed from the plates and landing at the bottom of the battery's casing (and therefore likely to short the plated out too, TB, you are perfectly correcct; that technique is more to deal with reduced capacity due to sulphation, which can occur due to neglect and/or being left in a discharged state often.

Ron.

[omega2018]

wow some of those prices are extortionate.  shop around you should be able to get a basic one for £15 delivered from china.

i have 2, last one was £14, "1500mah".  First was £36 and is a little larger and came with a zipped bag and lots of extras.  that one claims to be 16800mah, not sure about that but i tried the ultimate test - disconnect the mig battery entirely and try and start just on the lithium one.    it works.  so it won't spin your engine for ever but if your only problem is the battery, even if the battery is totally flat, it will start you car.

here is the second one i bought http://www.ebay.co.uk/itm/232277190721

first one i bought looks identical to this one (green and black) http://www.ebay.co.uk/itm/122423663043

beware sellers with less than 50 sales.

I accidentally drained my old "16,800mah" one  last week and took it apart today to try and revive it.  turns out it is, under the case and with the wrapper removed, 3 x 3.7V 4amp batteries so actually only 4,000mah.    Still it has twice started my 2.6 on its own with the car battery removed. 

I've ordered a replacement "50,800mah" one in case I can't revive the one cell that has switched off. 

[johnnydog]

Still it has twice started my 2.6 on its own with the car battery removed. 
[/quote]

I was once told by an auto electrical that you should NEVER start a car with either a jump / booster pack or jump leads from another vehicle connected directly to the leads of the recipitant car without an actual battery connected. Even if the battery on the recipitant car is totally flat or knackered, you should still leave it in situ, and connect to either the terminals or preferably any built in terminals / earth point. Maybe the more knowledgable auto electrikery experts can expand on the reasoning behind this a bit more?

[omega2018]

if you remove the battery and connect another car battery via jump leads all you have is a car with a battery wired in but with longer connections.

a booster pack is slightly different in that the lithium ones are not designed to be charged at 14.7V so you shouldn't leave them connected after the car has started. whether you have disconnected the main battery or not. 

having said all that normally you would leave the original battery connected, unless it is shorted or damaged. I only removed it as a test of the boost pack.  I could have discharged my battery completely to test the boost pack but it wasn't necessary or good for the car battery and would take ages.

i don't know why your electrician said that, if anything i would say the danger is connecting jump leads to a battery in situ that is shorted internally.

[Kevin Wood]

I suspect it's because, if the connection were to become intermittent, you'd have a vehicle running with no battery at all. The battery does act as a buffer against the voltage spiking too high when you get a sudden change of load on the alternator or inductive loads such as injectors, coils, motors and so on are switched. You might well end up with a lot of dead electrics if that happened, hence it's regarded as a bad idea.

[omega2018]

surely if the connection fails the engine will stop, with no supply to the alternator therefore no output from the alternator. 

unless its a soot chucker.

in any case its the same as an intermittent connection to the original battery eg a loose earth connection.

[TheBoy]

wow some of those prices are extortionate.  shop around you should be able to get a basic one for £15 delivered from china.

i have 2, last one was £14, "1500mah".  First was £36 and is a little larger and came with a zipped bag and lots of extras.  that one claims to be 16800mah, not sure about that but i tried the ultimate test - disconnect the mig battery entirely and try and start just on the lithium one.    it works.  so it won't spin your engine for ever but if your only problem is the battery, even if the battery is totally flat, it will start you car.

here is the second one i bought http://www.ebay.co.uk/itm/232277190721

first one i bought looks identical to this one (green and black) http://www.ebay.co.uk/itm/122423663043

beware sellers with less than 50 sales.

I accidentally drained my old "16,800mah" one  last week and took it apart today to try and revive it.  turns out it is, under the case and with the wrapper removed, 3 x 3.7V 4amp batteries so actually only 4,000mah.    Still it has twice started my 2.6 on its own with the car battery removed. 

I've ordered a replacement "50,800mah" one in case I can't revive the one cell that has switched off.

As you have found, Lithium batteries cannot deal with over discharging.  In fact, the unit should have safety precautions to prevent that, but if it was cheap Chinese tat...

[Bigron]

migmog, oftentimes nicads, NiMH and lithium cells develop dendritic 0Needle-like) crystals internally and short the cell out, hence it appears to be dead.
I technique I have used successfully in the past is to clear (vaporise) those crystals by "flashing" the cell by connecting it VERY briefly across a car battery. Now, care is needed; do not attempt to connect it for more than a fraction  of a second. The best way is to hold the negative terminal of the cell and quickly brush the positive terminal of the cell with the positive wire from the car battery.
Pause, and check the cell's voltage; if it has ben restored - success!
If not, wait a few minutes and try again.
This member accepts NO responsibility for any conflagration, death or maiming as a result of your trying this!
Only joking, really.....I hope. 

Ron.

[omega2018]

wow some of those prices are extortionate.  shop around you should be able to get a basic one for £15 delivered from china.

i have 2, last one was £14, "1500mah".  First was £36 and is a little larger and came with a zipped bag and lots of extras.  that one claims to be 16800mah, not sure about that but i tried the ultimate test - disconnect the mig battery entirely and try and start just on the lithium one.    it works.  so it won't spin your engine for ever but if your only problem is the battery, even if the battery is totally flat, it will start you car.

here is the second one i bought http://www.ebay.co.uk/itm/232277190721

first one i bought looks identical to this one (green and black) http://www.ebay.co.uk/itm/122423663043

beware sellers with less than 50 sales.

I accidentally drained my old "16,800mah" one  last week and took it apart today to try and revive it.  turns out it is, under the case and with the wrapper removed, 3 x 3.7V 4amp batteries so actually only 4,000mah.    Still it has twice started my 2.6 on its own with the car battery removed. 

I've ordered a replacement "50,800mah" one in case I can't revive the one cell that has switched off.

As you have found, Lithium batteries cannot deal with over discharging.  In fact, the unit should have safety precautions to prevent that, but if it was cheap Chinese tat...

actually the problem is the cells are too clever - two are reading 4.3V and the third one is zero, yes 0.00, nothing at all.  the cell electronics seem to have shut it down.

bigron's trick is the first one i tried, no joy yet.  next step is the freezer then a re-charge.  then the bin.

[zirk]

If its reading 0 then sounds like its fuvked, you could try flashing that cell only or slowly recharge just that cell but sounds to me like its game over for that one.

[TheBoy]

actually the problem is the cells are too clever - two are reading 4.3V and the third one is zero, yes 0.00, nothing at all.  the cell electronics seem to have shut it down.

No, that's classic lithium failure mode when a cell is overdischarged.

I have a handful of Lipos that have gone like that, no electronics in the packs I've disassembled.

[TheBoy]

migmog, oftentimes nicads, NiMH and lithium cells develop dendritic 0Needle-like) crystals internally and short the cell out, hence it appears to be dead.
I technique I have used successfully in the past is to clear (vaporise) those crystals by "flashing" the cell by connecting it VERY briefly across a car battery. Now, care is needed; do not attempt to connect it for more than a fraction  of a second. The best way is to hold the negative terminal of the cell and quickly brush the positive terminal of the cell with the positive wire from the car battery.
Pause, and check the cell's voltage; if it has ben restored - success!
If not, wait a few minutes and try again.
This member accepts NO responsibility for any conflagration, death or maiming as a result of your trying this!
Only joking, really.....I hope. 

Ron.

Just remember that rechargeable lithium type batteries have a nasty habit of bursting into flames when even slightly misused

[omega2018]

actually the problem is the cells are too clever - two are reading 4.3V and the third one is zero, yes 0.00, nothing at all.  the cell electronics seem to have shut it down.

No, that's classic lithium failure mode when a cell is overdischarged.

I have a handful of Lipos that have gone like that, no electronics in the packs I've disassembled.

disassembled it, separated the batts from their personal circuit boards, two reading 4.2V and one 0.25V (as opposed to 0.00 with the electronics).  Have binned it.

[omega2018]

migmog, oftentimes nicads, NiMH and lithium cells develop dendritic 0Needle-like) crystals internally and short the cell out, hence it appears to be dead.
I technique I have used successfully in the past is to clear (vaporise) those crystals by "flashing" the cell by connecting it VERY briefly across a car battery. Now, care is needed; do not attempt to connect it for more than a fraction  of a second. The best way is to hold the negative terminal of the cell and quickly brush the positive terminal of the cell with the positive wire from the car battery.
Pause, and check the cell's voltage; if it has ben restored - success!
If not, wait a few minutes and try again.
This member accepts NO responsibility for any conflagration, death or maiming as a result of your trying this!
Only joking, really.....I hope. 

Ron.

thanks, tried that (with a fire extinguisher at the ready).  the duff cell got warm and its bag expanded but no revival this time so its binned