Alternatorless & preparing for winter

[Daox]

I've been working on the alternatorless modification a little bit lately (installed an onboard charger) and the thought has occurred to me that I will probably need to do something more for it to enable me to use it this winter. Last winter I didn't use the modification at all due to having an older battery that just didn't have enough capacity to do what I needed it to. However, now I have a new deep cycle battery and now is the best time to try to make it work during winter.

To enable good winter operation, we need to get the battery warmed up a bit. So, the first step to do this will be to get some insulation around the battery. I'll be able to fit ~1/2" polystyrene around the sides of the battery (unfortunately not the top or bottom as I'm space limited) to hold the heat in. In addition to that I'm looking at heating wraps for the battery. Kats makes a few, but the reviews on amazon aren't the best. Does anyone have any other recommendations?

Alternatively, it would be ideal to heat the battery with engine coolant, but that is a much more complex project unfortunately. Darin also mentioned to me a while ago about moving the battery into the cabin to share the heat from the heater. This definitely would allow me to keep the battery warmer during the day while the car is in the parking lot (not able to plug in anywhere). Also, any relocation of the battery would allow me to add more insulation around the battery to retain the heat better through the day.

Any other ideas are welcome!

[GeneralAnarchy]

About 10 years ago I was trying to make something similar in an old truck where I had dual batteries with an isolator and onboard charger along with a block heater. The way I got "around" the cold problem was I reserved the deep cycle for running and a standard battery for starting. Often you can separate the starter and accessory +12V lines easily. That's actually where I got my idea for the brake pedal mod idea for the Enginer. If you step on the brake (or even use a turn signal) it would make sense to re-connect the alternator on a non-hybrid so the forced spin of the engine while decelerating is at least doing something beneficial. Step on the gas however and the battery should be doing all the 12V work and let the alternator spin free. I never did get the relay hooked up. But 50 amps from the alternator while braking could theoretically recover a bit and I figure I could always lightly ride the brake or use hazards if I needed an emergency 12V boost. This brakelight-switched relay charger wouldn't work if you actually rip out the alternator, which maybe you can't do with a serpentine belt.

By the way, JC Whitney once has a vacuum switch that would cut out the AC compressor during acceleration. It was marketed as a horsepower booster, but it could also save gas. While braking it seems good to grab all the kinetic energy you can even if it's just compressing your freon. Why shouldn't cars of non-hybrid variety by default auto-defrost & defog your windows while the brake lights are on? Heck wash your windshield and play with the power windows too 'cause it's free.

[Weather Spotter]

I like the relocation idea. the cabin will stay a lot warmer and you can add a second battery if needed (or swap that one out).

[Daox]

I just ordered the katz 80W heater this morning. The bad thing is, I don't think its going to work very well now that I did the calcs (of course AFTER I ordered it).

First, I assumed the whole battery was made of water. I know this is not correct, but we're just getting a ballpark figure here. So (10-1/4" x 6-13/16" x 8-7/8") = ~2.6 gallons or 21.7 lbs.

80W heater will give me 80Wh in an hour (duh ) = 273 btu.

273 btu / 21.7 lbs = ~12.5 degree F increase.

Since my block heater is sized to heat up as quickly as possible, I only have about an hour to preheat. So, it looks like I may need some additional heat somehow, and insulation is going to be very important.

[comptiger5000]

That 12.5* will still be a good start. Plus, it will absorb some engine heat once the engine is warmed up.

[RobertSmalls]

By mass, your battery is mostly lead, which has a very low specific heat: 0.031 times that of water.

A large, deep-cycle battery holds about 6qt of acid, so perhaps yours holds a gallon / 3.8kg. Add in 0.4kg of water to represent the lead, SO4, and PP, and you have 4.2kg. So 80Wh would raise its temperature about 16°C / 30°F.

That should bring you above freezing. How hot do you need?

How much heat is generated in the battery during charging?

Edit: I just realized there are THREE reasons you need insulation. One, since there's a thermal insulator between your heater and battery (the PP battery case), you'll need a much better insulator between the heater and the environment. Two, if heat is generated during charging and discharging, you'll need to retain that. And three, a fully discharged battery has H2O instead of H2SO4, and can freeze slightly below 0°C. Perhaps that third point was obvious to you, but not to me.

[Daox]

Well, thats kind of the thing. Do I leave it uninsulated to absorb engine bay heat and just let it cool down faster? Or, do I insulate it as best I can to keep in the heat it does have? I'm not sure.

Here is an image from the Kat's catalog. I'm not worried about having enough cranking power, but this pretty much shows me that 12* isn't worth anything.

[Weather Spotter]

It still will help, each degree is about 1% more cranking amps. If you need more heat you can buy a second one have two.

[comptiger5000]

Try to insulate it from the outside as much as possible. You can insulate the side closest to the engine less, as that side needs less insulation to keep warm, and will allow heat to be absorbed from the engine.

[Phantom]

For some good cheap insulation use neoprene the stuff that wetsuits are made from. Diving in 50F water with a 3mm wetsuit on is chilly but bearable.
Neoprene - Wikipedia, the free encyclopedia

Look up a dive shop in your area and ask them if they have any wetsuits that are worn out (rentals/class used). Worn out ones will have holes in the knees and arms but you just need the chest part (I would let them know what you are doing with it). You could then sew a pouch/cover for the battery there also is a glue that is made for neoprene but probably not needed.

If there is not a dive shop in the area to try and get free neoprene you can get some here Seattlefabrics.com if you want to buy it and you can even pick your own colors.