Best winter battery storage tips


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Alas, winter weather has arrived here in the Berkshires in Western Massachusetts and it is too cold/treacherous for enjoyable and safe Radrovering for the next few months. I have removed my battery and placed it in heated storage for the winter. Does anyone have further recommendations? My plan is to hook it up to the charger every 3 weeks or so and keep it fully charged until spring. I was wondering what others do/recommend?
I'm sure others will chime in but I don' think it's best to store it fully charged. Around 80% is what I hear.
I would charge to 50% and insulate it. Monitor charge periodically throughout winter and top-off if needed.
I use the 18650 batteries for flashlights and bike lights. Keeping the 18650 around room temperature or cooler and 50%-80% charge seems to prolong life. I couldn't ride to work and back on a 80% charge level; but, it should be easy to do if I wanted to store the battery pack for a while. I would plug something into the USB port like my iPhone to drop the charge to that range before storage. I think Luna Cycles sells a smart battery charger for $100 that you can set to 80%/90%/100% charge to help with battery life:

There seems to be a big risk with 18650 being a fire hazard if damaged. Might look into maybe a something fire resistant for storage in your house just to be safe. I've dropped my battery pack by accident once and was afraid it would burst into flames when I put it on a charger.

I don't know by how much extra life you get down the road if you do this. I'm only expecting 2 1/2 to 3 1/2 years of use from my battery pack before needing to replacing. Anything above that is a bonus for me.

I've heard getting the batteries extremely cold for prolong periods, very low charge in the 5% range, or zero battery charge really hurts longevity of the 18650 (there is some chemical change that may effect battery life). If the batteries do get near freezing cold, they need to warmed to room temperature before charging or using for best results.
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Hey RonDog1957, here's what one of the guys at Rad Power told me...

We recommend storing your battery inside as close to room temperature as possible when not in use. If you are not using the battery for an extended period of time, deplete the battery to between 50-75% capacity and store it inside off of its charger. There is no need to periodically plug the battery in during this time as the cells will keep well at this charge level.
Hi RonDog 1957, I feel your pain. I live in Marshfield, Ma. and it's 19 degrees out here. Usually we are warmer than you guys as we are on the coast. Too early for these temps. Don't charge your battery every few weeks. Read the link above.
Thanks again to all. I now have a good handle on winter storage (working on getting my battery level down), but this all now begs a different question. During the riding season I typically run my battery down to about 50% on a 15 mile ride and immediately plug my bike in upon my return, leaving it plugged in until my next ride (hopefully the following day or two but unfortunately sometimes a week or more). After reading the above reference, I am thinking perhaps a better practice would be to leave the battery at the ~50% level, and wait to recharge the battery until just before the next ride (within reason). Is this what we are saying is best for battery health/longevity? Of course the down side to this practice is it requires a little more foresight and planning for rides as the bike isn't ready at a moment's notice. Thoughts?

hfk2 - glad to here there's another Rad fan in Massachusetts!!
I top off when I get to work in the morning (purchased a 2nd charger from RPB for work). I then top off when I get home for the next day of bike commuting. There has been times going home in a stiff +25 mph headwind, 4900 ft to 5400 ft for 6.5 miles, and my power was down to 1 bar after being at a full charge when I left work (weighing 265 lbs+30 lbs of riding gear/work clothes doesn't help range either going uphill).

Unless I have plans to ride over the weekend; I just leave the bike at whatever charge over the weekend from my Friday commute. I just recharge the bike on Sunday afternoon or night for the Monday morning 5:30am commute.
I buy lots of Li-Po batteries for my rc heli's and they are stored at the factory 46-48% and they keep for along time. My charger has a storage mode so they can be stored like that. just my take