100% discharge rate capacity

john61ct said:

In fact storing them cold is much better for longevity.

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Ianhill said:

Goatman, you don't have to heat the battery all day it's ok to store cold as long as you warm it before use so have a heat pad warm it hour before you go out depending on how much mass the battery has,
Obviously a single cell will warm faster than a load of them.

I tend to use my ride just after I've charged it normally so I'll bring it indoors for hour or two charge it and then ride it of it was a cold work scenario I'd try to mimic that walm the pack to charge it then keep it warm once charged ready to go and possibly wrap it in a heat blanket or emulate a thermos type environment double wall battery box with a good air gap

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goatman said:

john61ct said:

In fact storing them cold is much better for longevity.

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then I think you have to wait a few hours to use them if the air temperature is different its in the data sheet somewhere around section 7.6

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eMark said:

john61ct said:

And if you do want warmer batteries to get better performance

as above **do not** rely on the harmfully internally generated temp rise

but pre-warm the pack before setting out.

Ideally by having a design that makes it essy to snap in and out so you can bring it inside.

Insulation + an active warming circuit will help in extreme conditions

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AGREE! :thumb:

Ianhill said:

... I used to cycle a Lipo pack on a small scooter charge in the warm and allow the pack to settle first but discharge at negative Celsius temps for 40 mins or so in cold weather, and even when there was ice about I'd get home and my packs would feel warmer than if I'd been riding around 15c or warmer and it's because I was over stressing them and they didn't last more than 80 cycles till cells started to fall like dominos.

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Well, one thing we'd like to know is how many lost cycles would be forfeited by continual use in cold weather when a Lipo packs high drain keeps it above freezing, say 60 F ?? When the pack feels warm to the touch it may be +95 degrees ... depending on how cold your fingers when you touch the Lipo pack.

Same with RC pilots flying their planes in the winter on a frozen lake. Flying aggressively enough to keep Lipo pack temp above freezing, but hopefully not so warm as to drastically shorten its cycle life. The question arises with say a VTC6 (20A rating) pack if the drain rate (e.g. 10-12A) is enough keep the battery above freezing (e.g. 50 F), while not drastically reducing the charge/discharge cycles.

Isn't this basically one aspect that goatman is getting at with lower or higher pack temperature and its affect on discharge rate of capacity; while still achieving a reasonable cycle life longevity? For example with a Kenda etrike with a large Plano container mounted between rear wheels it's perfect for placing say a DIY VTC6 pack, or any pack, in the container with (or without) provision for auxiliary heating. However, a DIY VTC6 pack with aggressive use could keep the pack above freezing (say 50 F) without any provision for auxiliary heating even if the outside temp is well below freezing. But ideally not a good idea to warm the cells with aggressive drain.

Any possible interest in using a high drain cell as a means of providing its own warmth is interesting, but how practical? What would be of some interest is knowing whether a VTC6 pack with aggressive use in cold weather makes sense ... OR ... are high drain cells like 30Q and VTC6 more useful for vaping and powerful flashlights than for a DIY ebiking build? Has anyone built a pack using VTC6 cells and how many useful charge/discharge cycles? The bottom line seems to be not to build either a low drain or high drain pack with one purpose being aggressive winter use so that the pack provides enough warmth to keep it above freezing (say at least 40 F).

goatman's thread is interesting in that it raises the question whether either 30Q cells or VTC6 cells or 50E 21700 cells are practical for building a DIY ebiking pack. Hopefully, this will be discussed at sometime on docware's ageing thread as he's testing those three cells. 50E has 9.8A rating, so possibly it offers the best of both worlds (aggressive use and longevity) for future DIY builds that aren't as restricted to most ebike's triangle space. Maybe, the 50E is just the ticket for an electrified motor cycle.

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