Preparing Battery For Winter

 In various places I've noted my first motivation for this little endeavor was so that I can bike year round with out getting cold and wet. I've been a lot more active on bike Twitter recenlty, and I get there are lots of clever jackets and other devices to keep you warm, dry, and visible, but I'm an engineer and I think I and we can do better. 

So I'm working on bringing these trikes to market. The point of the three wheeled platform is that it will give me the opportunity to put a cab on my bike. I'm hoping to start that little project this weekend, and blog post will follow. 

But there is another issue for 'winter ebiking' and that is battery protection. 

Lithium Phosphate (LiFePO4) batteries are some of the best performing batteries in cold weather but they have their limits. And the biggest bummer is, those limits are far far before the abuse Chicago will put them through in the winter. 

Specifically- LiFePO4 batteries will discharge at 70% of their rated capacity, where lead acid is closer to 45%. For this and a number of other reasons is why we will always use LiFePO4 over lead acid.

Cold Weather Charging

The first issue is cold weather charging. Specifically you should never attempt to charge Lithium Phosphate batteries that are below freezing. Well... you can but you have to do it really slowly and carefully. 

There are some manufacturers who make batteries that can be charged when they are as cold as -4F (-20C), which if you live in Chicago means you'll still likely kill your battery come January, if not sooner. 

But how do the batteries die? Well Lithium Ion batteries can die from something called litium plating. In short, at extremely low temperatures if you try to charge your lithium ion batteries they can short circuit and otherwise be irriverably damaged- NASA did a fun write up on the details- read it here if you care. 

There are some methods to overcome this. Amazon (and others) sell battery blankets to warm up the battery. You could put a little space heater in your garage, etc.  And if you live in a place that never drops below freezing- good on you. Read the rest of the post for entertainment, but you can keep your battery below the bed. 

In the image above, you see the new Lithium Ion battery I installed after Riot Fest to the left and the controller box to the right. While it isn't too tedious to open up the bed like this, it's not something I want to do when it's freezing cold out- hence this post. 

 Another method is to charge the batteries extremely slowly- I calculated on my 40AH battery I could charge it at about 2 amps, and it would take 3 days to charge. 

An upshot, is that once the battery is under load, it will internally heat itself up a bit. The moral of the story is don't go hot rodding around in the middle of a polar vortex. 

 Extra Long Range

Another benefit of this mod- is that occassionally I might want to go on an extra long ride, like over 40 miles. I can't think why off the top of my head, but it's possible. In such cases, I'd like to be able to swap the battery out. At the time of writing- BtrPower, who make pretty OK Lithium Ion batteries are charging around $660 for a 40AH battery, which also happens to be the one I installed after Riot Fest.  So if I want to go visit some friends out in Wheeling, it might not be a horrible idea to bring a spare. 

The Mod

So the purpose of this mod was really just to put a container in the bed, which then will house the battery. This is a pretty simple mod- I did it with:

  • A Husky 5 Gallon Heavy Duty Storage Container from Home Depot
  • A 1/2" Metal Drill Bit / Drill
  • A couple feet of 10 gauge black and red wire and a couple feet of 14 guage for the charging wires
  • Corresponding waterproof spade connectors - I like Hasstronica
  • A few bolts. 

All we do is bolt the container into the bed then drill some holes to bolt the container in place, and a hole to run the wires. I drilled two since I'm also going to put a significantly larger power inverter in the box as well for running heaters and other accessories (more on that in a later post). 

I chose to hook up the original charging port, but it wasn't necessary- hooking up the charging port lets me hook the entire rig up to a charger with out removing the battery. Which is nice in Fall/Spring, but in the dead of winter I'll pull the entire battery inside and let it warm up for an hour or two before I charge it (or better yet, have a spare battery and just swap them when one dies). 


The admitted downside of this rig is that somone now could in theory steal my battery with significantly less effort- so it may be worth adding some security features like a lock or something. 

Another note- you can see in the picture, I butt mine right into the corner which prevents me from using one of the latches- I did this because the saddle bag was in the way- looking back on the entire thing, I would probably use a more secure box (maybe an Army Surplus Ammo Can?) and mount it in the center. But the important thing is- I won't end up accidentally

Another note: I've put some links for various products in this article- I am not an affiliate marketer and get no kick backs from anyone. That said, I may be one day, and if I am I'll delete this paragraph. Since you're reading it, just know I'm only putting links in for convenience, buy whatever you want. 

 



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