DIY Li-Ion Jumper Box (and battery bank)

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PHeller
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DIY Li-Ion Jumper Box (and battery bank)

I’ve got oodles of Li-Ion batteries around for my flashlights, and I want to put them into use in something productive.

Has anyone seen an empty battery box that can run 4× 18650 in series to jump a car battery, but also has a USB plug for charging devices?

Or, at the very least, seen a battery box that could be wired up with heavier gauge wires with batteries in series?

flydiver
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I think you would need a LOT more than 4S to deliver the amps required for car starting. The jump starter I have probably has at least 20 cells (4s5p) in it based on size alone, if not more.

To Air is Human, to Respire….Divine.

jf_smm
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4s might get you over the top if the battery is a little low. The motorcycle l-ion batteries look like they’re at least double that size.

L4M4
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Since you need hundreds of Amps – LiPo is the way to go.
Even the best 18650s don’t come over 30A or so, so you would need a lot of them in parallel.

itsonlyme
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People have posted here that they have used rc lipo packs

manithree
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Technically, this is what you’re asking for, but I agree with the previous posters that it likely won’t have the current to jump-start a car.

I have a couple, and they work pretty well. Just don’t put any battery in wrong, or the springs are toast. Well, I’ve heard that.

flydiver
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manithree wrote:
Technically, this is what you’re asking for, but I agree with the previous posters that it likely won’t have the current to jump-start a car.

That pack is a 2s2p (8.4v) so is unsuitable both from a voltage and an amperage ability.

To Air is Human, to Respire….Divine.

manithree
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flydiver wrote:
That pack is a 2s2p (8.4v) so is unsuitable both from a voltage and an amperage ability.

You are correct.

PHeller
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Hey thanks for shutting me down, guys!

Gotta learn and embarrass myself somehow!

BlueSwordM
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Well, unless you have a battery box that can hold 21700s to use Samsung 30Ts, you are out of luck.

Along with some very low resistance contacts, such a build would be quite interesting.

How many 18650s would you like to use in your design?

Something like a 4S4P arrangement would work pretty well for cranking with sufficiently powerful cells.

My very own high current Beryllium Copper springs Gen 3:
http://budgetlightforum.com/node/67401
Liitokala Aliexpress Stores Battery Fraud: http://budgetlightforum.com/node/60547

jf_smm
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PHeller wrote:
Hey thanks for shutting me down, guys!

Gotta learn and embarrass myself somehow!

On the other hand…I’ve seen someone trickle charge a car battery with a crap load of AA alkalines.

If you’re patient this might still work Wink

LouieAtienza
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I had one of those glove-box battery jumpers. It died on me, so I took it apart. It was just a 3s LiPo and a circuit board that handled charging, a USB port, and a multi-color LED. I was surprised to see that it actually charged the battery through the balance port. I bought it for $110 at the time (maybe 4 years ago at the NY Auto Show) but I could probably build a better one for about $50 in parts and an afternoon.