Anyone built a Lithium jump starter

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Re: Anyone built a Lithium jump starter

Postby dax » Sat Aug 20, 2016 8:19 am

All my lifepo4 cells have come in by air, lifepo4 seems acceptable as they are very safe compared to other lithiums, haven't built a lifepo4 starter, but have build a dedicated lifepo4 solar charge controller which works wonderfully well.

I've found if you are importing via sea, use an Aus based customs broker, if you use a chinese shipping company they tend to add extra charges when your good arrive in Aus and won't release them until you pay up. You have to pay straight away of they start charging you exorbitant storage fees.
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Re: Anyone built a Lithium jump starter

Postby Jimbo007 » Sat Aug 20, 2016 11:43 am

Thankyou for that vital info.
It looks like I'll need to prepare a flow chart to follow so I don't get bitten.
Incidentally, the LiFePO4 battery I bought was a drop in replacement for high end motor cycle battery. It can be recharged the same as lead acid providing one doesn't exceed a specific voltage. I can't recall whether it was 13.5 or 14.5 for the battery, presumably 4 cells inside.
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Re: Anyone built a Lithium jump starter

Postby dax » Sat Aug 20, 2016 12:41 pm

Unless your lifpepo4 battery has a built in BMS and even those seem to use lead acid parameters, using lead acid chargers will reduce it's life down to 2-5 years. Lifpeo4 only like bulk charging, not lead acid float, adsorb or other controls. Lifepo4 is nothing like lead acid and they have very different charge requirements, especially upper and lower parameters.

It's a very simple formula which if you stick to it, will give you at least a 15 years of use. Only use bulk charge, in a 12v system that means full charge to 14v then switch off charging, the pack will settle to 13.8v and recharging should start at 13.6v, or 3.4v per cell. Never take your cells over 3.5v and never under 3 volts, the majority of usable energy is stored between 3.1 and 3.4v. So 14v upper and 12v lower. Lifepo4 hate slow charging and floating a lifepo4 cell will render it useless in a few years, when you should be getting 15-20 years out of them at least.

It's the same with storing lifpepo4, with lead acid you have to keep a charge on them at full capacity and then you suffer from sulphication very quickly. With lifepo4, you can store them at 3.2v for years with no supporting charge.

I bought a couple of lifepo4 car batteries, which worked really well. One was in my car and the other was a spare until I worked out their lifespan, used the spare (20ah) for charging cordless power tools through an inverter in my workshop. Made sure the spare only got bulk charge and the other used the car settings. After 3 years the car one was getting stuffed and wouldn't provide the starting charge, whilst the spare is still in use and has lost nothing.
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Re: Anyone built a Lithium jump starter

Postby Jimbo007 » Sat Aug 20, 2016 5:20 pm

The one in the car probably suffered from a combination of heat damage in the engine bay and continued float changing while the car was running not to mention that a cold alternator will put out in excess of 14 volts on a cold morning intended for lead acid but not tolerated by lithium batteries.
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Re: Anyone built a Lithium jump starter

Postby Gordon-Loomberah » Sat Aug 20, 2016 5:37 pm

"Float" charging with a car alternator isnt the same as floating with a solar charge controller, the alternator maintains the high charging voltage, a solar controller drops it back to a lower voltage. High temps + high voltage may have killed it.
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Re: Anyone built a Lithium jump starter

Postby Jimbo007 » Sat Aug 20, 2016 5:59 pm

Precisely
I have some large 2.8 Ah Lion cells that came from an early laptop battery, configured as three series pairs, ie 5.6Ah 10.2 volts. I almost threw it away but fortunately curiosity got the better of me and I opened the pack to discover the BMS had failed and the cells were perfect, even now after 20+ years.
I now salvage all lithium cells from my computer batteries as it's always the BMS that fails.
A dedicated lithium battery charger is fine to charge the cells, just being careful not to over discharge them.
Closer to the original subject, have you noticed the outrageous claims regarding the capacity of the jump start packs on eBay?
My neighbour bought one that claimed 18000mAh (18Ah ) and its about a quarter of the size of the 14Ah bike battery.
Must have come from Dr Who's tardis.
Some claims are crazy at 52000mAh and the like.
Last edited by Jimbo007 on Sat Aug 20, 2016 6:17 pm, edited 1 time in total.
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Re: Anyone built a Lithium jump starter

Postby Gordon-Loomberah » Sat Aug 20, 2016 6:09 pm

The problem with the new alternator regulators is that they are not adjustable. I remember the old mechanical one on my GTR Torana, and it was the same one used on my parents EH holden when I was at school- very easily adjustable to whatever voltage you wanted! "Progress" isn't always a good thing, I wonder if you can still buy them, and replace the new improved modern non-adjustable one?
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Re: Anyone built a Lithium jump starter

Postby Jimbo007 » Sat Aug 20, 2016 6:18 pm

The ones that have en external box regulator in fact have an adjustable trimpot in them.
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Re: Anyone built a Lithium jump starter

Postby Gordon-Loomberah » Sat Aug 20, 2016 6:22 pm

Jimbo007 wrote: have you noticed the outrageous claims regarding the capacity of the jump start packs on eBay?



Haha yea, I commented on that to my wife, who bought one from a local auto shop. Talk about exagerations!
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Re: Anyone built a Lithium jump starter

Postby Jimbo007 » Sat Aug 20, 2016 6:36 pm

You could also make your own, I did many years ago.
Electronic regulator I should say.
Last edited by Jimbo007 on Sat Aug 20, 2016 7:22 pm, edited 1 time in total.
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