sub freezing temperatures: how to keep battery warm

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martyL1000
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Joined: 10/24/2011
Points: 6

I hope to find a way to keep riding my new Trek FX plus even after temps here in Madison, Wisconsin dip below freezing and stay there for three months. Any suggestions?

I was thinking all I'd need is some kind of extension-connector (e.g., a ten-inch cable that would allow me to carry the Trek batterey pack in a wind-proof pannier stuffed with insulating materials, rather than in the standard open-air rear rack), then I could slow the battery's drop in temperature long enough to make my 45-minute commute.

But I have no idea where to begin looking for the parts, nor for the person with the skill to build this extension-connector.

Any ideas would be greatly appreciated.

Martin L

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alan in tempe
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Joined: 04/04/2009
Points: 31
Re: sub freezing temperatures: how to keep battery warm

martyL1000 wrote:

I hope to find a way to keep riding my new Trek FX plus even after temps here in Madison, Wisconsin dip below freezing and stay there for three months. Any suggestions?

I was thinking all I'd need is some kind of extension-connector (e.g., a ten-inch cable that would allow me to carry the Trek batterey pack in a wind-proof pannier stuffed with insulating materials, rather than in the standard open-air rear rack), then I could slow the battery's drop in temperature long enough to make my 45-minute commute.

But I have no idea where to begin looking for the parts, nor for the person with the skill to build this extension-connector.

Any ideas would be greatly appreciated.

Martin L

If the cells start out warm, are kept working during the commute, and kept warm inside during the day, I would think they will be fine. They should generate enough internal heat while pushing a few amps to avoid dangerously low temperatures. Wrapping a pad around the pack on the rack to help contain the self generated heat and keep out wind should help, too. It is important to start the battery working as soon as they go outside. The hardest part of the cold on the cells are when the cells are fully charged. A full charge at low temps is less than a full charge at warmer temps, so just cooling down fully charged Li cells can cause them to be overcharged.

-- Alan

Jagwire
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Joined: 02/01/2007
Points: 2
Re: sub freezing temperatures: how to keep battery warm

Hi Martin,

Check out these guys:

http://www.pacorinc.com/

Cheerio,

John Egan

martyL1000
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Joined: 10/24/2011
Points: 6
Re: sub freezing temperatures: how to keep battery warm

Hey, Guys, thanks very much for your replies. Alan, I'm elated to know I probably won't have to reinvent the wheel to keep riding into the colder months. You inspired me to look around more, and sure enough, lots of people do keep on out there, despite serious Canadian blue northers.

THe reason I started this thread is when I bought the FX+, my local Trek dealer essentially said I'd be moth-balling it starting around December b/c the battery won't be usable most days. Maybe that's just what they have to say, liability-wise, and what not. I'm sure it's not a good idea to leave one of these expensive batt's out in the cold for long, but they had me totally discouraged. I'm happy to know all I really need to do is start out each day with the battery at room-temp, bring it in with me when I get where I'm going, and charge indoors overnight.

I think I will, over time, rig up some kind of windbreak to shelter the battery on the otherwise wide-open rack. THat openness might work to my advantage if I end up devising something more serious, like what John E. pointed me to on pacorinc.com (Thanks, John!)

But the good news is, unless I"m planning on some serious multi-hour trekking in single-digit temps, I'll be fine without much hassle, at all, in keeping the battery pumping.

Thanks, again.

Martin

alan in tempe
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Joined: 04/04/2009
Points: 31
Re: sub freezing temperatures: how to keep battery warm

I think it is safe to take your BionX out for multi-hour trekking at a time. The important things to remember are 1) keep it in use to keep it warm when it is charged and out in the cold, and 2) do not charge it when it is cold (or hot). It should be fine to keep the battery on the bike after it is out of charge (it turns itself off long before its charge is too low that you need to worry about too deep of discharge). Cold is only harmful if it is near full charge, or where it might freeze the cell (colder than you will be able to take!). Take the battery inside with you, and let it warm up before recharging in. You probably should leave the system off after the battery is empty, and not try to use regen in very cold temps after that point. On the other hand, if your multi-hour treks are more than ten degrees C below 0, you may want to disregard this advice!

-- Alan

cyclepete
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Joined: 05/27/2008
Points: 64
Re: sub freezing temperatures: how to keep battery warm

I was unaware there was an issue.

I live in NJ and it sure doesn't get as cold as Wisconsin, but I ride every day year round a bike with a Bionx 350 PL on it and have taken no special care. My battery is the type that mounts in the bicycle triangle rather than the rear rack style you have.

I do charge in a garage where the temp is generally over 50 degrees, but I leave my bicycle and battery outside all day at work.

Many days I have ridden to work in 15 degree F weather, left the bike out all day in low 20s temps and then ridden home in mid-20s degree weather with no problem at all. There is some reduction of range but it's not much. I've also gone on multi-hour rides in low-20s with no problem. The only precaution I take is to let the bike sit in the garage for 30 minutes or so when I get home to warm up before I turn on the charger.

Been doing this for three years now with about 11,000 miles on the Bionx system.

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