Anyone built a Lithium jump starter

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Re: Anyone built a Lithium jump starter

Postby offgridQLD » Sat Aug 20, 2016 5:53 pm

Yes there are overstated capacitys on some battery's. Though it's worth taking note of the lithium chemistry used and also the format.

Lifepo4 has the least energy dencity. Unlike the lithium cobult cells that are considerably smaller for the same capacity. A lot of the lithium cobalt cells are pouch style with a thin case. Prismatics like the calb wast a lot of space with the thick plastic case and low energy density chemistry.

I have a 18 ah 5v USB power bank that's very small about the size of a large smartphone but thicker.It is a true 18ah measured using a USB power meter gadget.

That said if the brick is the size of a packet of instant noodles and mentions 50ah it's stretch.
Offgrid 2008, Selectronic PS1 6kw/48v inverter, x 2 Midnite solar classic 150 MPPT, 3960w NE PV 24 x 165w BP panels, 4200w NW PV 21 x 200w DAQO PV, 16x400ah lithium.
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Re: Anyone built a Lithium jump starter

Postby dax » Sun Aug 21, 2016 6:29 am

I agree, the engine bay is not the right environment for a lifepo4 pack, but it still holds charge and is used for a light in the generator room. Got a couple of 12v jump starters which work very well, looking at a 24v one to try in the trucks and bus. Went back to lead acid for vehicles until someone comes up with a way to keep lifepo4 happy under the bonnet. Must admit for the 3+ years it operated, it was great, never a slow start always heaps of power, then in the middle of a cold winter, it started to die. Going from below zero to over 50deg under the hood, sure makes a big difference to their lives. Have thought of moving the battery position to somewhere the pack won't suffer dramatic environmental conditions, as we do with lifepo4 packs that have to live in big changes in their environment.

Against just about all the theories, in my experience floating a lifepo4 cell or pack in any way will reduce their lives dramatically and make then go out of balance. We bulk charge and that's it, use an active BMS, but on my own packs just the charge controllers, upper and lower cell voltage alarms and relay switches. After more than 8 years, my house pack is in wonderful condition and gets balanced once a year if needed.
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Re: Anyone built a Lithium jump starter

Postby Jimbo007 » Sun Aug 21, 2016 12:07 pm

For the cost of the batteries, I would be making a storage room from the same material as they use to make shop cool rooms and freezers, then installing a small inverter reverse style A/C to take care of them. Cost about five hundred diy ( not hard to do ). It would use minimal power but create conditions to give you maximum life from your batteries which could outlast you! :D
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Re: Anyone built a Lithium jump starter

Postby offgridQLD » Sun Aug 21, 2016 12:31 pm

Yes after doing that myself and running it for a while now. Battery's have never experienced temps over 24C.

I would make it standard procedure on large (full house size) offgrid systems in Australia. Battery's and power electronics sucking in icy cold air on a 40C day is very comforting feeling knowing you can hammer the system all you want and its going to stay comfortable.

The AC only operated on hot sunny days and you always have plenty of PV energy to spare on this kind of day so it works hand in hand.

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The only alternative would be to some how have your battery's deep underground to stay cool. Though you would then have to have your power electronics in a separate room or they would just heat it up. refrigeration gives you way more flexibility . Not to mention zero dust a big plus on a dirt road.

My room isn't cool room material but its solid concrete block walls, Concrete floor, ceiling is double insulated 3" foil blanket under the tin and 2nd layer of bats between that and the fiber sheet ceiling.
Offgrid 2008, Selectronic PS1 6kw/48v inverter, x 2 Midnite solar classic 150 MPPT, 3960w NE PV 24 x 165w BP panels, 4200w NW PV 21 x 200w DAQO PV, 16x400ah lithium.
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Re: Anyone built a Lithium jump starter

Postby Jimbo007 » Sun Aug 21, 2016 1:24 pm

He he,
I think that's more than adequate. The other thing I was thinking about is that in Canberra where I am, the winter temperature frequently falls below zero at night. This can't be good for batteries either. The small cost in extra panels would be worthwhile to ensue the batteries longevity.
My system is in its infancy at the present but still more than enough to cool my ten square house in summer from a single 1hp reverse cycle A/C ( Fujitsu ) it has not missed a beat but has dropped the power bill such that service charges exceed consumption.
When I add more panels and my 2Kva GTI, I'm sure I'll have power to burn and will try to dump the grid ( which incidently here usually sits around 256 to265 volts, very harsh on electronic equipment ).
My inverter provides exactly 240 volts, still higher than the 230 volt Australian standard but acceptably closer than the grid!
Also my neighbours house has lost all their appliances three times over the last twenty years from lightning strikes. They must be on a different phase to me fortunately though I hate to think what their wiring insulation is like now.
Much safer off grid if you do it your self, you can ensure everything is done properly and no shoddy work done by some lazy apprentice!
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Re: Anyone built a Lithium jump starter

Postby offgridQLD » Sun Aug 21, 2016 6:38 pm

I wouldn't suggest doing the AC work yourself unless your ticketed to do so. Though perhaps finding most of the gear yourself and designed your own system then perhaps working as TA for you your sparki would help make sure the standard is kept up to scratch and you get what you want.

Yes sub zero weather can be a issue for lithium cells. Only when you go to charge them . As in If you lifepo4 cells get frozen and you try to charge them frozen you can damage them. Though if the room is insulated and has the power electronics in it (inverter) then the heat from that over night in a small room would prevent the temp from dropping to low.
Offgrid 2008, Selectronic PS1 6kw/48v inverter, x 2 Midnite solar classic 150 MPPT, 3960w NE PV 24 x 165w BP panels, 4200w NW PV 21 x 200w DAQO PV, 16x400ah lithium.
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Re: Anyone built a Lithium jump starter

Postby dax » Mon Aug 22, 2016 5:50 am

Lifepo4 don't like having large currents taken out of them when very cold as well. You could build an insulated container for your cells and use a peltier unit with some temp controls, so it keeps your pack at a reasonable temperature. The amount of energy a peltier uses in this situation is very low, it's only on when needed and a well insulated box will retain it's temp for a long time.
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Re: Anyone built a Lithium jump starter

Postby Jimbo007 » Mon Aug 22, 2016 8:18 pm

Whilst I'm not ticketed to do A/C, I have assisted a qualified person with many split and ducted systems. The correct procedures must be followed not only to prevent loss of the refrigerant but also to maximise the life of the system. Failure to remove all the moisture from the system will result in highly abrasive ice crystals floating around in the sealed system, much to the detriment of the compressor!
I am no stranger to high voltages having been a ham radio operator for over 40 years. With valve transmitters, voltages can easily be 2500 volt or more at enough current to barbeque you!
My wiring practices and standards exceed most electricians.
I've seen some unforgivable errors made by apprentices such as reversing the neutral and earth on an outlet. The result being, any attempt to use that outlet tripped the earth leakage.
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