What to do with bottom of battery rack?

[sportcoupe]

Why don't you get a couple of semi-truck battery blanket heaters and wrap the whole pack? Or at the very least some home insulation?

[DaveTM]

Battery heaters would be OK when the cart is sitting out the nite before (if I'm someplace other than home. If I'm home it's in a heated garage.). But the problem then begins when I have to get away from a 110-V outlet...unless I have one really, really long extension cord.

I've looked at these seat warmers from Gerbing's http://gerbing.com/media/catalog/pro...scchgc_5_3.png as you can set the heat temp....but I don't think it would be the right thing to use. Just not enough "stuff" there to wrap around all the batteries.

[sportcoupe]

Power inverter. AC power on the go off a 12v battery.

http://www.harborfreight.com/automot...ter-66814.html

[yurtle]

I've questioned before whether the gain in keeping the batteries warm would offset the loss of having to heat them. I'm in the South so I didn't worry about it for mine, but in extreme cold...

I figured if it would, someone would be selling a 36 or 48 volt heater for hunting buggies. You could probably just insulate the bottoms and wrap the whole pack, and not worry about a separate heater for each battery. Would have to be made for wet, corrosive environments.

[DaveTM]

The inverter, IMHO I don't think would last all that long "out there." I have one for my Silverado and use it for a leg cramp "muscle beating" machine that I need. It works fine but I have my doubts that it would last long on a single 12-V battery in the cold.

Now, just searching around, something like this may work, http://www.omega.com/pptst/FCH-FGC0....=FCH-FGC00052R again, if properly hooked up, and if the compartment were sealed relatively well enough so large air drafts could not invade it.

Dave

[JohnnieB]

Dave, if you keep the cart in a heated garage overnight, you only have to keep up with the heat loss to retain battery capacity. So one way to mitigate the heat loss is to trap the air inside the battery compartment, which would lower the amount of heat that needs to be added. Maybe the 12V 40W heater you linked to would be enough to acceptably lengthen the time it takes for the batteries of cool off.

Sealing the battery compartment will trap the explosive gasses inside, but most of the Hydrogen is generated during charging and if you open the top and have a fan blowing into the battery compartment while charging, that should reduce the explosion risk to acceptable levels.

Blowing warm air into the battery compartment will also help to get the batteries up to the garage temperature. Batteries have a large thermal mass, so the don't heat or cool quickly.

[DaveTM]

JohhnieB...Yeah, that's what I was thinking. A small heater such as the one I referenced would likely keep enough heat in the "box" to keep the run time up. You know...prevent the batteries from losing their "garage heat" for a lack of a scientific word. (My college "science for business majors would be steaming right now if he saw me make that statement!!! ) And yes....sealing off the big gaps in the box would help do the trick also. I wouldn't sweat the small stuff so much, and as you say....keep the seat up (why yes....I am married ) when I charge the batteries.

The last time I sealed up everything I tried to keep it all warm with a kerosene heater. I had a slight accident!!!

Dave

[sportcoupe]

Originally Posted by DaveTM

The inverter, IMHO I don't think would last all that long "out there." I have one for my Silverado and use it for a leg cramp "muscle beating" machine that I need. It works fine but I have my doubts that it would last long on a single 12-V battery in the cold.

You mentioned running a small heater off a 12v battery to warm the batteries. A small heater will have much higher wattage then a few 80 watt battery blankets. You are looking at somewhere around 6 amps draw (plus inverter loss) to run one battery blanket. Maybe 3 blankets might wrap all the way around your pack so figure ~20 amps. A large deep cycle could run 20 amps for longer then your cart pack would last maybe.

[DaveTM]

Originally Posted by sportcoupe

You mentioned running a small heater off a 12v battery to warm the batteries. A small heater will have much higher wattage then a few 80 watt battery blankets. You are looking at somewhere around 6 amps draw (plus inverter loss) to run one battery blanket. Maybe 3 blankets might wrap all the way around your pack so figure ~20 amps. A large deep cycle could run 20 amps for longer then your cart pack would last maybe.

Well, I'm so far removed as any type of engineer....which is why I come here ....but when I look at the spec's for this http://www.omega.com/pptst/FCH-FGC0....=FCH-FGC00052R 10W heater, and then I go here: http://www.supercircuits.com/resourc...amps-converter to do the conversion, when I punch in 10 watts, and 12 volts, I get amps of .8333. Now, if I go to the next size up heater and put in a 20W 12V heater, and plug in the numbers, I get amps of 1.6666, both of which is much less than the 6 amps that your discussing, plus I don't have the issue of wrapping the batteries and or the concern of spillage of acid on the wraps and causing their demise.

I believe I could locate such a small heater in a place near the bottom where gasses don't rise, plus with the fan constantly on, the gasses wouldn't get back to the heating element.

Please "shoot" holes in my thinking. I welcome all shots. I have no toes that have not been stepped upon!!

Dave

[sportcoupe]

Dave,
My 6 amps was based on a single 80 watt heater. 80 watts using an inverter to 12v is ~6 amps. I didn't know that came in such a small size as 10 watts.

I didn't think about the acid eating the blanket heater. Good catch.

I probably would go a different path based on that.