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View Full Version : I need advice on battery warming for charging and riding



picaroon
16 April 2012, 1345
I've been looking into batteries for my lambretta, its going to be my daily ride to work and so temperatures for charging will probably be less than 10 degrees celsius for at least 4 months of the year :(

So i'd like to know if anyone has any ideas on a setup to warm my battery pack before charging and before use???

My thoughts are along the line of an electric blanket ( I saw this item on ebay (Saft America Inc. - Thermal Electric Blanket Battery Heater))


3043

And then maybe a temperature sensor in the battery pack which will switch off the heater and switch on the charger. Maybe have a timer on the charger then too. So then I can just plug it in and go and fill my hungry belly with dinner :)

Is there already something I can buy or use?

I'd really like to know what you have all done, or is there any advice you could throw my way?

Gavin.

picaroon
18 April 2012, 1417
The batteries I am thinking of getting are the A123 20Ah prismatic cells from Victpower.

I have read a few times that charging at a temperature below 0 celsius (32F) will damage the cells which cannot be reversed. So a better charging temperature would be above 10C (50F} as to not reduce the cycle life or Ah capacity of the cells.

I would like an enclosed weather proof battery box which is climate controlled, so warm enough to charge and then able to be cooled when I’m riding.

My soggy English climate may be a lot different to yours of course! Its wet and cold here today and we only get over 30C (90F} just a few weeks in the year and it dip below freezing at nights for a few months :eek: My garage is attached to my house but it’s not heated.

Any suggestions would be good
Do I even need to worry about cooling?
Or make changes to the box for winter/summer?
Can anyone share if/how they warm their batteries?

ARC EV Racing
18 April 2012, 1522
I've never considered warming lithium cells prior to charging to be honest, usually we're concerned with making sure they stay cool but that's during a race. I don't think you'll need to worry too much about heat while running from what I know of your build.

Some of our enclosures have electric fans built in to force air across and around the cells. I guess you could build in some way of using the fans to circulate warm air prior to charging, then run the fans for cooling (ambient air, no need for air con!) if things get hot while you're riding. That way your warm air source doesn't need to be on-board, it could be a small fan heater with appropriate ducting. Use warm air rather than hot though!
There'll be some degree of heating due to internal resistance during a charge anyway.

It may be possible to build a totally sealed enclosure and use conduction to heat/cool things inside but you'd have to be very careful about regulating the pressure. Otherwise if a cell were to go up you'd be looking at a bomb rather than a fire. In reality it can be fairly weather proof as long as the enclosure is behind a fairing so that there's no direct path for spray to enter the pack through the vents. We've raced in some terrible conditions but never had an issue with water ingress.

As you mentioned you'd need some sensing and control system to regulate the temperature and kick in the charger when it's ready. Not so much need for a timer on the charger - the BMS should take care of ending the charge for you.

picaroon
19 April 2012, 0709
Thats good to know I dont need to worry too much, cheers :)

So when I get around to measuring up for whatever batteries I coose, I can just allow for the pack to have fans added if needed and somewhere I can attach warm air pipes to.

An old hair drier set to warm plugged in next to my charger sounds the easiest for starters.

ARC EV Racing
19 April 2012, 0944
I think that might work in principle, although you'd need to think about how to distribute the warm air without causing hot spots anywhere inside the pack. Perhaps if the control system was built with several temp sensors you could monitor for that.

The image of an old hair drier left alone to warm a lithium battery pack sounds kinda scary to me somehow!

picaroon
19 April 2012, 1101
Haha yeah!

Now I have re-read my post it sounds scary to me too!

I could just draw warm air from my house and pump it through the pack, that sounds safer :)

ARC EV Racing
20 April 2012, 0327
Yeah that sounds better! If you're charging after riding it home you're not going to be starting with a cold pack, so it's just a matter of keeping the chill off.