Car Jump Starter as backup pedelec battery?

[peterjd]

Hi, I've got one of those 'Car Jump Starter' batteries which is doing very little most of the time. Its stated capacity is ~ 70Ah at 12V. If I had a suitably rated step-up converter to say 40V would it be feasible to use it as an 'backup' supply for my nominal 36V pedelec. I can already run my pedelec for limited runs on my 3 - 5 Ah 36V tool batteries. Peter

 

[saneagle]

Hi, I've got one of those 'Car Jump Starter' batteries which is doing very little most of the time. Its stated capacity is ~ 70Ah at 12V. If I had a suitably rated step-up converter to say 40V would it be feasible to use it as an 'backup' supply for my nominal 36V pedelec. I can already run my pedelec for limited runs on my 3 - 5 Ah 36V tool batteries. Peter

70Ah at 12v would weigh about 6kg. Is that how big it is? Most of the ones I've seen are probably around 100wh.

 

[peterjd]

I agree it sounds implausible, given it's tiny and weighs about 280g, but its label has 'Battery capacity: 69900mAh' Chinese hype? Worked brilliantly as a car jump starter on my Jazz hybrid.

 

[lenny]

150W 20A Battery Capacity 4-wire Tester DC USB Tester Electronic Load Lithium Di | eBay

Constant current operation（CC）2. Constant resistance operation（CR）3. Constant power operation（CP）4. Overload protection2.Overcurrent protection3. High temperature protection Device background settings (Chinese / English settings) 1.

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[saneagle]

I agree it sounds implausible, given it's tiny and weighs about 280g, but its label has 'Battery capacity: 69900mAh' Chinese hype? Worked brilliantly as a car jump starter on my Jazz hybrid.

280g is about 50wh max. I would translate the Chinese as 6 x 3300mah 3.6v cells. For comparison, the average 18650 cell weighs about 50g and has around 10wh in it. Lipo and LiFe have a bit less. The jump starter I opened had a single 3S lipo in it.

 

[sjpt]

Maybe it meant 'Battery capacity: 69900mWh'. Or maybe it's just a random number.

 

[Nealh]

Certainly not 70ah most likely nearer 6000mah .

 

[Nealh]

280g is about 50wh max.

I agree my calcs would put it at max 72wh.

 

[Nealh]

I use a graphene lipo for the odd jump starting . it is only 52wh,
4.4ah x 12v.

 

[Az.]

Don't complicate simple things. It sounds like you need a bigger bike battery. Bike battery, not a pocket size powerbank.

 

[Nealh]

The small pocket power packs are ideal for instant punch often 600a or more , but not much use other wise unless using at a default 12v supply.

 

[Ghost1951]

I agree it sounds implausible, given it's tiny and weighs about 280g, but its label has 'Battery capacity: 69900mAh' Chinese hype? Worked brilliantly as a car jump starter on my Jazz hybrid.

I bought an ebay mini torch with a useful pen clip to keep it in your pocket, that claimed some vast luminescence (1.2 million Lumens).... It's not a bad pocket torch for the money - a touch over 4 quid, delivered, but it isn't a searchlight for sure.

 

[Benjahmin]

I've got one of those jump starter things. Claims to turn over a 3litre diesel or 6 litre petrol engine. It's a bit smaller than a brick. I use it to power a sat nav when I'm away camping - sits in my Carradice handlebar box.

 

[saneagle]

I've got one of those jump starter things. Claims to turn over a 3litre diesel or 6 litre petrol engine. It's a bit smaller than a brick. I use it to power a sat nav when I'm away camping - sits in my Carradice handlebar box.

There are different ones with different sized lipo batteries in them. That's all they are, with a charging system and something to protect them from being reverse connected.

 

[peterjd]

OK, I get the message. I will be satisfied with its use as a fairly effective torch in addition to its proven car starting ability. Thank you for the advice.

 

[harrys]

Efficiency might be poor with one and a DC booster. I once bought three on clearance, and hooked them in series, It worked OK for a 250W ebike, although I didn't know at the time that a total voltage from a series combo might blow out the BMS circuits.

That never happened, but I left the bike out in the rain and that destroyed the charger circuits,