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I bought a Huffy electric bike but I don't have charger. The person at pawnshop where was bought said I can charge it with a car, like jump start.

enter image description here

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    I added a generic Huffy electric bike picture off the Walmart website. Can you confirm that your bike looks like that? If not can you delete that please. If you can add a photo of your actual bike that would help a lot. – Móż May 27 '16 at 9:54
  • Why don't you ask pawnshop guy what he meant? – Criggie May 27 '16 at 10:01
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    @Criggie I'm going to guess that what the pawnshop guy meant was "give me your money", and would say anything at all to make that happen. It doesn't sound even vaguely plausible to me, but I'm an electrical engineer who builds bikes. Rather, it sounds like the sort of thing a lying arsehole of a salesman would tell an ignorant customer in an effort to make a sale. I'm going to bet that the sort of salesman who says that is also not going to give a refund if the OP take the bike back. – Móż May 27 '16 at 10:03
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    It's possible that the pawnshop guy was just ignorant, but there are several reasons why you cannot "jump start" the bike from a car. However, presuming this is a standard "powered assist" bike where the battery charges as you pedal, you may (if the battery is not in too bad of condition) may be able to charge the battery by riding the bike. – Daniel R Hicks May 27 '16 at 11:38
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    @DanielRHicks many cheap e-bikes don't charge from going along. – Chris H May 27 '16 at 12:30
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DO NOT DO THIS!

You can't safely charge any battery using jumper leads from another battery. If the other battery matches the flat one, but is fully charged, the current will be so high that you will probably start a fire. You will definitely damage the flat battery, and probably both of them. Jumper leads work on cars by having enough resistance that the flat battery survives, but you should never leave them hooked up between two batteries in an attempt to charge one from the other. Car batteries are also designed to supply very high currents, so can accept high currents without too much damage. Bike batteries are not like that.

The main problem is that electric bikes, even really old ones, normally run at 36V, some older ones at 24V or 48V, but a single car battery is 12V. At best a car battery charger will do nothing for you. If your electric bike is old enough to have a series of lead-acid batteries (that work in a similar way to car batteries), a car battery charger might be able to charge those one at a time without damaging anything.

If your bike is a more modern one it will use lithium batteries and you won't be able to charge it at all with a car battery or battery charger. Unfortunately, if you open the battery case up and attempt to charge it, you could easily set the whole thing on fire. Look up some of the videos of hoverboard fires if you want to see what happens.

You really need to find the correct charger and use that. You can probably buy one from Walmart, but you may have to find the spare parts section on their website to do it.

I will edit this answer to be more useful if you can supply more details.

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    To make it worse, some systems have the charging control circuit built in to the battery pack (common on Li-ion), others have it built in to the power supply (common on lead-acid). – Chris H May 27 '16 at 12:33
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    The battery should have voltage, input and output current labeled. I agree, unless it is an electrical car, typical car dynamo nor battery will not pour voltage higher than 12v. – mootmoot May 27 '16 at 13:50
  • Even on a car, you don't connect the batteries directly to each other. You connect the host end of the -ve lead to earth not to the battery terminal. – Holloway May 27 '16 at 14:34
  • @ChrisH - You cannot imagine how bad it would be if lithium battery pack didn't have the charge/discharge control circuitry built in. – Daniel R Hicks May 27 '16 at 17:26
  • @DanielRHicks I've seen the videos. I've also come across pathologically bad design where (presumably to cut costs) last resort protection in a bought component is used for everyday control in the final product. Usually the risk there is only 230V not explosion, and I'm sure a reputable manufacturer would do it properly, but for a lithium system I'd check the specs on the manufacturers replacement part very carefully before going for a cheap equivalent. Hence my note of caution, not wanting to go further than "common". – Chris H May 27 '16 at 17:53
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DON'T CHARGE YOUR EBIKE BATTERY WITH CAR CHARGER

Most probably you have 36V Lithium-ion battery. Car charger won't match this battery and in worst case you can get an explosion in your garage:

enter image description here (this image is clickable and leads to Youtube)

Search "lithium battery explosion" on YouTube, you'll figure out that it can be very dangerous.

EBIKE CHARGER DC PLUG TYPES

To find a charger for your battery you need to take a look at charger plug on it. Most common plugs are:

enter image description here

After this, you can go to AliExpress or any shop you prefer and find charger for 36V battery with plug that matches your battery.

FIND CHARGER ON ALIEXPRESS

Aliexpress search results: http://www.aliexpress.com/af/lithium-ion-battery-charger-36V.html?ltype=wholesale&SearchText=lithium+ion+charger+36V

Average price for charger you need is $30.

36V CHARGER IS ACTUALLY 42V CHARGER

This is actually the most confusing part for beginners. When you open charger page you'll see this:

enter image description here

It's fine that voltage of "36V charger" is 42V. This is because the voltage of Li-ion and Li-Po cells is:

  • 3.7V for epmty cell
  • 4.2V for full cell

36V battery contains 10 cells, therefore battery voltage goes from 37V when it's empty to 42V when it's full. You'll ask - why it's called "36V charger" and not "42V charger" and I don't have a better answer than: for historical reasons.

OUTPUT CURRENT

Finally, some words about output current which is 2A on screenshot above. 2A means that if your battery has 10Ah capacity, it will be charged from empty to full in 5 hours (10Ah / 2A = 5h). 2A is most common output current for average ebike batteries like yours.

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    nitpicking units: the battery capacity is rated in Ah rather than A, which indeed gives you 5h when dividing 10Ah / 2A – njzk2 May 27 '16 at 19:07
  • thank you @njzk2 for that clarification, I amended my answer. – Limon Monte May 27 '16 at 22:06

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