Warm Batteries

[greenpower dude reloaded]

I've been struggling to come up with a way to heat our batteries for our next race then it hit me! Why don't I ask those plucky, resourceful young men (and women) on F1technical, I'd ask you most things so why hadn't I already asked you this.

Basically batteries work better the hotter they are, within reason of course, and so I want to take the batteries up to a maximum of about 50degC I know that they are fine to go hotter but then the level of safety drops plus its nice to know that you could go better should the competition warrant it.

So any quick easy suggestions? I've tried a number of things but to know real avail.

So.. what shall I do?

[CarsonAu]

Are you using lithium ions/polymers or lead acids?

[greenpower dude reloaded]

Very good point why did I not mention that. They are Standard Lead Acid batteries 70a/hr but only deliver a geniune 35-40a/hr at the current we draw. hence the heating get it right and we could have up to 55-60a/hr

[marcush.]

would it make sense to look into the sources of waste energy in your vehicle? I guess the motor does produce a fair amount of heat...I´m thinking towards the ideas how rocketengines are cooled by their fuelsupplylines (see Eugen Sänger),of course you would need to find a ways to move the cooling liquids without using too much of energy .....

also you could coil up the Battery cables a few times and put these coils
around the batteries...it is just immaculate what a coil can produce in terms of heat... ,just a little joke,couldn´t resist...

[greenpower dude reloaded]

Interesting thought, but if you're any good you don't have much in the way of waste energy. The trick is to heat them up whilst charging... Any ideas?

[EDIT] this is an area that is not at all restricted, I'm just looking for a good way of heating these batteries up a bit. i'm sure there must be something simple i can do!

[jon-mullen]

Reptile heat pad? A lot of them are flexible so you can shape them to your batteries. There are heating cables also made for reptiles that might work.

Google results for "reptile substrate heater"

[marcush.]

you could as well take floor heating cables or do the same with copper/aluminium tubes to pass hot water thru the battery box.....could be disconnected just before the start of the race....

to retain the heat as long as possible ,what about doublewall stainless thermo insulated bottle priciple ,not that big project to weld up a double wall thin gauge
stainless steel batterybox and cover...put in double seals for the lid and weld in two tubes to route the cables thru ..and you could even put some heat packs underneath the battery to retain the temps .

Heatpacks.Active Charcoal,Ferrous powder react when exposed to air..-these are small packs you just shake them up a bit
-gives 57-69°C heat for 7 Hours according to the distributor ...self adhesive body warmer available
http://heatpack.de/index.php/en/ for example. and fairly cheap as well.you could try that almost instantly,could you?

[greenpower dude reloaded]

Haha Great minds, the batteries are at home at the moment being charged sat on a large reptile heat mat, not sure its anywhere near enough though. They need to be REALLY hot.

It could be marcush, that, that is the way to do it.

At the moment I have very limited time until the race so I'm wondering about boiling water, pouring that into an insulated box with them in... What do you think? it all depends on if i can find a box man enough.

[BreezyRacer]

Are the batteries out of the car, or left in the car?

[marcush.]

the hot water thing is not going to help in the car,as you will need a lot of water or a proper circulation system to bring up the temps of the batteries in the first place.. one of those batteries weighs in at something like 20 kilos i estimate so thats a considerable mass to heat up.If you put say 2 Litres of water around the batterie I don´t think this will help your case very much very long..especially when air is conducting heat worse than water wich is very good at conducting heat.So once in the car and outward energy sources disconnected I see no reason for having water ,
because you will not be able to use it as a heat sink ,you simply don´t want the mass.
With the heat packs you rely on oxidation process ,I did not bother calculating the energy you might get out of the reaction ,but sure this will NOT add much mass to your vehicle ,so if it works it will be a net gain.So at least you might be able to retain heat you fed into the system for a longer time.

Brings me to the next idea: Are you allowed to open the batteries during the contest ,say for maintainance??? You could dump the cold Batterie water/acid and refill with hot water/acid ,this would at least make sure you got the whole batterie heated from inside out.Batteries are shipped dry but fully charged ,so this is something that should work with a used batterie as well.One could also think of a small pump circulating the acid water thru a boiling tank outside...
stinky business ,gogglesand all other safety measurements necessary, lots of high grade material (pump packings) etc involved ... so I ´m not sure if this is ever going to be faisible..
what about induction of heat wwith something like a induction hob(?), here in Germany you get small portable induction cooking stations for around 30€,of course without iron in the batterie this aproach might be of very limited effectivity..

[greenpower dude reloaded]

Sorry breezy, good point, they are out the car at this point. Charging at the track is banned so it's all done out the car at home.

You can gain by putting in a stronger concentration of acid the only problem is isn't easy to acquire such acid and I don't particularly fancy switching it over.. and so heating it all up seperatly although more effective isn't something i really want to try.

I used to use such heat packs when I used to go fishing during the winter and they never seemed to make much difference to me, mind you thats when winters were cold and summers were hot. Not the year long mild days we get now

[tarzoon]

while the batteries are being used, can you place them inside an polycarbonate casing? Besides being bullet proof, if hit by direct sunlight it may be quite nice and warm.

[marcush.]

short google trip gave me some hints :you can effectively stop the reaction when no Oxigen is present to feed the rection:put hte heat pack in a bag and all stops.
so it is of utmost importance that the heat pack can breath to keep the reaction going..
The same heat pack (for putting into a shoe will make 40°C in its designed place but up to 60°C in free air) .So you might want to actually have a Oxygen source in your battery case to get the most out of this...

[tarzoon]

the casing cannot be fully sealed. Oxygen and hydrogen are generated by the chemical reaction inside the battery and it can be a dangerous mixture if enclosed.

But combining the heat mat with the enclosure might help.

[flynfrog]

how hot are we talking?