Keeping batteries warm?

4394 Views 20 Replies 10 Participants Last post by Woodsmith, Feb 18, 2011

Woodsmith

Discussion Starter · Dec 5, 2010

A friend of mine works with a recycling collection crew in York, UK and they use a variety of pedal powered collection vehicles and also a Bradshaw FB2 EV van like one of these.

It runs on a pack of FLA batteries but is suffering from the cold to the point where it often needs to be pushed back to the depot.

I was wondering what options there might be to keep the pack warm that would be fairly low tech and low cost to do.
How warm would it need to be and when is it most important to keep it warm during the charge cycle given it will not be warmed while in use?
I have suggested adding insulation to keep any heat in while it is out in bad weather.

I will probably go and have a look at it in the new year to see what I could do to help it.

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DIYguy

· #2 · Dec 7, 2010 (Edited)

Hi Woody. I see no one has chimed in...

I guess there is the heat cable you bury to aid plant growth...whatever they are called. Theses have the thermostat built in and keep things around that 70 to 75 F mark I think. There are also the Farnam heating pads that seem to work for people. There are some 12 volt ones also that are made with adhesive to stick on RV water tanks. These are really nice if you go 12 volt. They are apparently also available in 120 volt apparently. I have a 12 volt one if you want a pic of it. I just bought it out of interest. It was at Princess Auto for $12 or something like that. One question that should be asked is.... do they want to heat just when parked....as in from the wall power? ...or heat whenever required when driving... in this case it could be 12 volt if battery and DC/DC were adequate...or some of the ones designed for AC could take pack voltage DC depending on what it is... some testing may be required here. Yes, insulate the boxes with covers to be removed in summer months. Some have talked about heating blankets...but I would be careful with this one... .perhaps too fragile.

Edit...to answer your question...70 to 75 F is a great temp for best performance and not shortening life of battery... (most important with AGM's)... Anything above 60 is pretty good.

Anyways, just thought I would chime in.

Also, just parking inside with some heat goes a long ways as they don't cool down too quick when in use.

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Woodsmith

Discussion Starter · #3 · Dec 7, 2010

Cheers, DIYguy.

I think the heating cable route might be worth looking at. The collection route isn't hugely long but the truck was really intended for more warehouse work then trundeling around city streets in winter snow.
I think the only option for heating would be during the charging period over night rather then while it is running.
I will see if there is a possiblity of keeping it at around 70-75F, 20-23C.

Here's a link to their recycling site http://www.stnicksfields.org.uk/recycling.php.

Thanks.

Jan

· #4 · Dec 8, 2010

I watched a non-jack-reckard show recently on his blog:

http://jackrickard.blogspot.com/

I know, it's about Li-ion, but maybe it is also possible with Lead. It's an interesting lecture, and he also tells how to heat up the batteries. Not by an externe heat source, but by pulling short bursts of high amps. This heats up the batteries internaly, right there where you need it.

Good insulation would then be enough.

dtbaker

· #5 · Dec 8, 2010

The farnum heating pads are supposed to be effective, but also a little expensive and you have to include a thermostat and relay to switch on/off. Examples I saw with the dirt heat cables are no good unless you just use them overnight with AC power.

I did find a product from heatline.com that has cut-to-length self-regulating cable which outputs up to 6 watts per foot, and down to about 1 watt per foot as it warms up. About $3.50 per foot I think I remember, and no switch/thermostat required right off direct DC pack power all the time. A fair parasitic load, but probably more than makes up for loss due to cold.

Woodsmith

Discussion Starter · #6 · Dec 8, 2010

Thanks guys.

This is going to have to be a simple solution that I will probably try to impliment myself for them.
The Bradshaw (she's called Beryl apparently) lives in an ISO container with a twin electric outlet inside limited to 13A overall at 240v (officially, at least).
It is charged on one of the outlets so I will have to see what the charger is drawing to see what is left for the heating.

Quite possibly there will be enough capacity for the parasitic load if the pack is more effective.

Not sure about pulling high amps to raise cell temperature, I don't think the collection route allows for it as it is very much stop start on fairly flat roads.

Duncan

· #7 · Dec 8, 2010 (Edited)

Hi Woodsmith,

How well are the batteries insulated?
Can you sneak in a couple of inches of foam?

Even just 10mm of foam under and around the batteries could make a big difference

You need to keep the batteries off the chassis - or you have a huge heat sink!

dtbaker

· #8 · Dec 9, 2010

or how about just a super thin space blanket? I plan to put a layer inside my box where I don't have room for foam on sides and bottom...

Woodsmith

Discussion Starter · #9 · Dec 9, 2010

I've not seen 'Beryl' in the flesh so to speak but I was looking at another couple of Bradshaws and the battery pack area is just a tin box over the rear axle.
I would think that there may be some space to wedge the the batteries tighter. I will report on that when I get to see her.
I might even contact Bradshaws directly and ask them. Not got time to drive the 140 mile round trip to look at 'Beryl's' battery box this side of Christmas.

Sunking

· #10 · Dec 9, 2010

DIYguy said:
I guess there is the heat cable you bury to aid plant growth...whatever they are called. .

If you can afford to do that, there is a less expensive more effective way to do it. Keep it on a float charger. Keeps the batteries warm and fully charged ready to go.

MN Driver

· #11 · Dec 9, 2010

dtbaker said:
or how about just a super thin space blanket? I plan to put a layer inside my box where I don't have room for foam on sides and bottom...

Space blankets rely on what is inside to create the heat and for the heat to be held in an air gap. Using a space blanket to keep cells warm likely won't do much for you.

Sunking

· #12 · Dec 9, 2010

MN Driver said:
Space blankets rely on what is inside to create the heat and for the heat to be held in an air gap.

Yes Sir wrap that ice cube in a space blanket with insulation and keep it frosty cold for days even when it warms up.

m38mike

· #13 · Dec 10, 2010

I use 110v soil warming cables under my FLA batteries in oak wood boxes to keep my batts warm. Even a thin layer of insulation under the batts makes a big difference, they don't get cold from the contact. They stay warm with the soil warming cables overnight. The charger helps to get the batts warmed up, and the cables keep them warm until I unplug. I can't hardly get 15 miles with 30 degree F batts. I can get over 20 miles with 70 degree batts. I got my cables online for about $10-15 for a 24 foot cable.

Woodsmith

Discussion Starter · #14 · Dec 10, 2010

m38mike said:
I use 110v soil warming cables under my FLA batteries in oak wood boxes to keep my batts warm. Even a thin layer of insulation under the batts makes a big difference, they don't get cold from the contact. They stay warm with the soil warming cables overnight. The charger helps to get the batts warmed up, and the cables keep them warm until I unplug. I can't hardly get 15 miles with 30 degree F batts. I can get over 20 miles with 70 degree batts. I got my cables online for about $10-15 for a 24 foot cable.

Thanks, Mike.
Real life results from soil cables. It really shows the difference when you get 1/3 more range.

Moving the charge time closer to the end of the night so that the batteries are still warm in the morning would also make some difference I guess. My friend mentioned this to me before.

dtbaker

· #15 · Dec 13, 2010

MN Driver said:
Space blankets rely on what is inside to create the heat and for the heat to be held in an air gap. Using a space blanket to keep cells warm likely won't do much for you.

the thought is there is a LITTLE heat from the cells charging and discharging, but I am also probably going to put soil cables or stuff from heatline.com underneath... the space blanket I would stick to the battery box with spray adhesive and it would have a little air gap, not in contact w/ batteries.

d

ElectriCar

· #16 · Dec 14, 2010

It's been in the teens and 20's here day and night for a few days. I insulated my pack on the sides and bottom using old political signs that made of plastic which looks like card board. This work well as my pack will only get down to the 40's during the day while sitting outside in the open air. The top of them is covered with a bubble wrap material in the winter.

Of course when you're driving and charging the pack is getting heated internally due to internal resistance.

At night it is charged in my garage which isn't heated but is better than being outside. It gets down to about 40 or so and the batteries read about 50-55 degrees in the morning after recharging the prior evening.

I think a good insulating job and storing it inside an insulated shed will help tremendously.

Good luck!

Woodsmith

Discussion Starter · #17 · Dec 17, 2010

Here is a photo of the Bradshaw's battery box.

I think there is enough room for insulation under and around it. The bottom of the box is an open frame so closing it off from the air would be good. There may not be enough space above the batteries but maybe the top of the battery cover could be insulated over the top.

Three of the eight batteries had to be replaced today as well as the onboard charger. It can bearly manage a single collection round now until the pack has been cycled a few more times.

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ElectriCar

· #18 · Dec 18, 2010

You've got enough room to glue/staple bubble wrap to the lid. That would be better than nothing! I just lay it on top of my pack.

Woodsmith

Discussion Starter · #19 · Dec 18, 2010

Hopefully there will be room between the terminals and the steel lid for a good thickness of insulation.
I was thinking of 2" of Kingspan PU foam insulation board all around.

I will get my friend to check the dimensional clearances.

socko

· #20 · Feb 18, 2011

hey woodsmith, did you take action to insulate or heat the pack? if so, what was the outcome? i'm trying to decide what to do about a build i'm doing right now. lithium-ion cells in metal boxes. room for thin insulation only and maybe some farmam pads... my lead-acid conversion drops at least 30% of its range at like 15 deg F. just fyi.

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