Building A Ludicrous 14s2p SPIM08hp battery

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thorlancaster328   10 W

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Re: Building A Ludicrous 14s2p SPIM08hp battery

Post by thorlancaster328 » Mar 26 2020 11:31am

Looks like these cells don't like the cold at all. After storage in the garage overnight (overnight low about -8°c), the pack measures an abysmal 193 milliohms, even worse than my old recycled 18650 battery pack. Hopefully the internal resistance is a lot lower at 30°c.
Find weakest component, upgrade it, repeat until satisfied. Rome was not built in a day.
When in doubt, get bigger MOSFETs / Batteries / Motors / Etc.

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DogDipstick   1 kW

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Re: Building A Ludicrous 14s2p SPIM08hp battery

Post by DogDipstick » Mar 26 2020 11:47am

thorlancaster328 wrote:
Mar 26 2020 11:31am
Looks like these cells don't like the cold at all. After storage in the garage overnight (overnight low about -8°c), the pack measures an abysmal 193 milliohms, even worse than my old recycled 18650 battery pack. Hopefully the internal resistance is a lot lower at 30°c.
Gotta be a fluke measurement.

Like I said I got 24 of these cells comming in the mail from Tom and gonna do some Powerlab testing.

I try to baseline all my testing at 59*.

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Allota Watts @ 83.1v of raw QS power takes me everywhere on my Ironhorse DW link XC... :) Powered by Chevy. :D Broke 10 horses the other day. ( BTW; ...don't get hurt... :? )... (Currently building a battery datalogger.). :roll: Playin with (24) IRFB4115s now. :wink:

john61ct   1.21 GW

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Re: Building A Ludicrous 14s2p SPIM08hp battery

Post by john61ct » Mar 26 2020 2:26pm

That sort of cold radically impacts every LI chemistry.

Only LTO is OK charging at normal say 0.2C rates there, not sure about discharge rates

thorlancaster328   10 W

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Re: Building A Ludicrous 14s2p SPIM08hp battery

Post by thorlancaster328 » Mar 26 2020 2:44pm

After heating the batteries with a box and a hair dryer set on low until the internal 10k thermistor I put in the pack read a steady 29°c, I did another test of the battery's internal resistance. Hooking up a load (subwoofer) that drew 27 amps, I measured a whole-pack voltage drop of only 0.5 volts after 3-4 seconds.
That's 18.5 milliohms for the WHOLE PACK.
:flame: Eighteen. Point. Five. Milliohms. :flame:
Holy cow! That's really, really really good. 1.3 milliohms per cell group on average. Can't wait to finish the pack and take it for a test ride.

The extreme temperature sensitivity of these cells (-5°c to 29°c cuts the IR by a factor of TEN) is likely the reason people are getting wildly varying results on these when they measure the IR. Bet you'll have loads of fun with your BatteryHookup pack as well as long as you keep it warm.
Find weakest component, upgrade it, repeat until satisfied. Rome was not built in a day.
When in doubt, get bigger MOSFETs / Batteries / Motors / Etc.

john61ct   1.21 GW

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Re: Building A Ludicrous 14s2p SPIM08hp battery

Post by john61ct » Mar 26 2020 2:49pm

Are we sure that ESR vs temp variation is unusual?

thorlancaster328   10 W

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Re: Building A Ludicrous 14s2p SPIM08hp battery

Post by thorlancaster328 » Mar 26 2020 2:52pm

My pack of Samsung 30q doesn't sag near this bad, even when it's really cold. My 12s12p 30Q pack only sags about 5 volts when drawing 60ish amps after being stored in similar temperature conditions. The 30q is a more advanced cell than these old dinosaurs, cold affects them a bit but not near as bad as these old SPIM08HP cells.
Find weakest component, upgrade it, repeat until satisfied. Rome was not built in a day.
When in doubt, get bigger MOSFETs / Batteries / Motors / Etc.

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