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Using 12 volt inverter to charge battery

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Using 12 volt inverter to charge battery

Old 05-04-19, 11:14 PM
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MarcusT
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Using 12 volt inverter to charge battery

Hello. Just picked up a Cube Stereo Hybrid with a Bosch CX/500.
I love it! It opens up an old world of riding that I gave up on because of age and lack of exercise.

My question is; Since extra batteries are stupidly expensive, I am considering other options for charging the on bike battery.
I know I can hook up a 12dv-220av inverter to my car, but looking for something portable. I have an old lead acid battery jump starter that I would take camping it weighs about 12 kgs and not very rider friendly. It would charge cell phones, air pumps and jump start a number of vehicles for several days.
Now, they have come out with the Li Ion jump starters that weigh much less and are much smaller. https://www.aboxtek.com/products/abo...w-jump-starter
Has anyone tried this method? I am looking at a a 18000 mAh battery, with a 300 watt inverter, (charger is 2 A) I believe it will work, but have no idea how much charge it will give my bike. (1 hour, 2, 3 charging?)
Tried google with very little results
I appreciate any assistance for this

Cheers
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Old 05-05-19, 06:16 AM
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The car starter is 18Ah. Divide maH by 1000 to get aH. It's 12 volts, so multiply volts x aH, and that starter pack is 216 Watt-Hour. I am not sure you could get 18Ah out of the starter battery. It drops in voltage as it runs down and the ad says it will not work at 25% charge, So figure you get 75% of that 216 WH. Call it 150 WH.

Your battery charger is 2A, so multiply by 48V and that's 100W. Divide 160WH by 100W and you get 1.5 hours. Figure electrical losses of 10-15% in the inverter/charger and that's like 1.3 hours? Just an estimate.

The number could be a little lower. The inverter might also shut off before the car starter pack runs down to 25%.

Edit/Update: See my later post. I don't believe this unit is really 18000mah,

Last edited by Doc_Wui; 05-05-19 at 12:11 PM.
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Old 05-05-19, 07:21 AM
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Originally Posted by Doc_Wui View Post
The car starter is 18Ah. Divide maH by 1000 to get aH. It's 12 volts, so multiply volts x aH, and that starter pack is 216 Watt-Hour. I am not sure you could get 18Ah out of the starter battery. It drops in voltage as it runs down and the ad says it will not work at 25% charge, So figure you get 75% of that 216 WH. Call it 150 WH.

Your battery charger is 2A, so multiply by 48V and that's 100W. Divide 160WH by 100W and you get 1.5 hours. Figure electrical losses of 10-15% in the inverter/charger and that's like 1.3 hours? Just an estimate.

The number could be a little lower. The inverter might also shut off before the car starter pack runs down to 25%.
Thanks Doc.
Thinking of asking a friend who has one of these starters to let me experiment a bit to get an idea. It's not a big expense (80 euro), and a charging time of only 2 hours would be worth it, if I am dry and need to get home
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Old 05-05-19, 11:28 AM
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I just couldn't convince myself there's 200 watt hours in that unit. I finally remember why. The people that market these things add up the amp-hours of all the internal cells. That inflates the true value.

It's probably three battery cells in series inside that pack. If each of them are rated at 6000 mah, they call it 18000 mah in the power bank world. In the EBike world, we call that that 6000mah because you can really only add the AH for cells in in parallel.

So divide every time I wrote by 3. You get 20-30 minutes of charging. Not worth your time. Do try to borrow that unit from your friend and see if its real world performane is as predicted.









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Old 05-13-19, 11:48 AM
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Thank you for the arithmetic. I'm new to the electrical/electronic side of cycling, and I have a related project. I have a 36v e-bike I'd like to use for long-distance travel. I'd like to use the car jumper I already have to charge a second battery if need be. I can use your arithmetic to see if that's realistic or if I need to settle for a 50-mile range between charges, go solar, or what.
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