Homemade lithium Jump Box or battery booster...whatever name tickles your fancy

[Checkthisout]

 So Im thinking. You need a bms for charging the thing up but there aren't really any BMS that can deliver the current I would want.

So I think the jumper leads should bypass the bms.

Has anyone constructed one of these things? A case for an old one would work great.

4 of these little guys right here.

EVE LF105 Grade A Cells - 3.2V LiFePO4 105Ah Battery

Shop the brand new EVE LF105 Grade A Cells - 105Ah LiFePO4 Battery for reliable and long-lasting power. Available now with fast shipping. Order today!

www.18650batterystore.com

 

[Checkthisout]

Perhaps only a balancer would be necessary for charging?

 

[BentleyJ]

Those type of Prismatic cells are typically for solar storage are rated at a relatively low 1C continuous discharge rate with momentary excursions up to 2C or maybe 3C. This would possibly be enough current for a 4 cylinder economy vehicle but undersized for larger gasoline engines and not usable on a diesel.
There are specialized high current LFP cells available such as these. Although they are only 40Ah so 2 cells in parallel would provide 400+ Amps at a 5C discharge rate.

High Discharge Rate 5C 10C Lifepo4 Prismatic Cell LFP 3.2V 40AH For Electric Vehicles Power Tools

High quality High Discharge Rate 5C 10C Lifepo4 Prismatic Cell LFP 3.2V 40AH For Electric Vehicles Power Tools from China, China's leading Lifepo4 Prismatic Cell product, with strict quality control 40AH Lifepo4 Prismatic Cell factories, producing high quality 40AH Lifepo4 Prismatic Cell products.

www.lifepo4batterycells.com

 

[Checkthisout]

Those type of Prismatic cells are typically for solar storage are rated at a relatively low 1C continuous discharge rate with momentary excursions up to 2C or maybe 3C. This would possibly be enough current for a 4 cylinder economy vehicle but undersized for larger gasoline engines and not usable on a diesel.
There are specialized high current LFP cells available such as these. Although they are only 40Ah so 2 cells in parallel would provide 400+ Amps at a 5C discharge rate.

High Discharge Rate 5C 10C Lifepo4 Prismatic Cell LFP 3.2V 40AH For Electric Vehicles Power Tools

High quality High Discharge Rate 5C 10C Lifepo4 Prismatic Cell LFP 3.2V 40AH For Electric Vehicles Power Tools from China, China's leading Lifepo4 Prismatic Cell product, with strict quality control 40AH Lifepo4 Prismatic Cell factories, producing high quality 40AH Lifepo4 Prismatic Cell products.

www.lifepo4batterycells.com

105AH x 3 available for 30 seconds = 315 AMPS, yes?

So correct me but that's 315 amps for 30 seconds which is enough to start something like a Cummins, Powerstroke or Duramax. This assumes the starting battery is stone cold dead. I assume the terminals themselves are a limiting factor (heating)?

Wondering what "damage" would be done if you carefully go over that rating?

Fawk it, run it and see what happens?

 

[Rednecktek]

105AH x 3 available for 30 seconds = 315 AMPS, yes?

Only if you're jump starting a 3v battery or have a 3p4s battery build. Remember, you need 4 of them in series to get up to a 12v battery, and the limit is still the 2c of the cell, so 105Ah cells @ 3.6v * 4 cells in series = 14.4v @ 200a for 30 seconds.

 

[42OhmsPA]

You might find these useful.
I've had 2 in series for months, I haven't tried starting a vehicle with them though.

Just found this amazing item on AliExpress. Check it out!
$32.96 42%OFF | Built-in BT JBD 3S 4S 12V LFP NMC Smart BMS 100A 150A Support Connected in Series Common Port Balance For Car Starting Power

https://a.aliexpress.com/_mObQuu6

Edit - it's been almost a year... Where the heck does time go.

 

[Checkthisout]

Only if you're jump starting a 3v battery or have a 3p4s battery build. Remember, you need 4 of them in series to get up to a 12v battery, and the limit is still the 2c of the cell, so 105Ah cells @ 3.6v * 4 cells in series = 14.4v @ 200a for 30 seconds.

The cells are 105ah so a 12V pack of 4 is 105ah @ 12 volts. The cells are rated to discharge at 3 X their ah rating for 30 seconds so that's 315 amps for 30 seconds, yes?

Per the Specs:

Maximum Charge/Discharge Rating (30 Seconds)

1C/3C

 

[Vigo]

Not against the idea but if you were trying to fit a lifepo4 replacement battery into the existing case of a jump box that used to have an SLA in it, you'd probably end up putting one of the many lifepo4 motorcycle starter batteries into it such as what i was playing with here: motorcycle battery in tiny tractor

 

[Checkthisout]

Not against the idea but if you were trying to fit a lifepo4 replacement battery into the existing case of a jump box that used to have an SLA in it, you'd probably end up putting one of the many lifepo4 motorcycle starter batteries into it such as what i was playing with here: motorcycle battery in tiny tractor

The prices dropped to $39.00 per cell!

That's a fawk it run it and see what happens price.