Cadilac never made a diesel engine.....Detroit diesel did.........

Well, you know what I meant!:rolleyes:

Be weary of eletronic (solid state) battery isolators. When I worked at the auto electric shop we had a lot of them come in bad.

The best way to do it is just put a large solenoid that connects the two batterie s when the car is running (or the key is on/start mode) and disconnects them when sitting.

You generally don't want two batteries in parallel sitting without any imput amperage to both of them. They will feed off one another (so to speak).

On our camper/truck, when you flip on the key it connects the two batteries in the engine compartment together (and one of those is connected to ANOTHER battery in the camper).

So you have 3 batteries all hooking up in parallel to fire the engine.

Now keep in mind...if you run one of your batteries down with a block heater or whatever you might be running off of it, you probably want the ability to get your car started WITHOUT connecting to two together becuase the 1st batt (charged) will feed the 2nd discharged one and all your power is going where you don't want it (when trying to start).

Sorry if that is confusing...I think two batts is a good idea but for where I live and whatnot, it rarely drops below the teens.

An intake heater might help your rig start (in addition to the glow plugs). I would look into that before putting 00 gauge wire from trunk to front...that stuff isn't cheap ;)

Yes, it does get cold up there!
 

But there are a lot of colder spots in North America then the UP of Michigan. I lived (as a child) just outside of the Soo as it is known, in the little town of Rudyard. Lots of snow and some dandy wind chills, and a couple of days a year ambient temperatures that will really try the soul of any diesel or diesel owner.
So how about this as a low cost easy solution. A quality battery in a case that has a handle, a pair of quality and short jumper cables and a small trickle charger. Keep the battery charged up and warm and when ready to fire up the SD, quickly hook on that warmed up battery with 650 CCA. When it has started and is running well, tuck the assistant battery in the trunk along with your jumper cables and later or the next day, while you do your studies, bring that battery back into the apartment and give it a charge. Batteries do vent a little acid vapor, but I don't think enough to be hazzardous if the charging is done while you are awake. I really think a small but warm "quality" battery could really make a difference.

A warm battery is much stronger than a cold battery that is a law of physics.
A person who carries batteries around frequently has bigger arm muscles than one who doesn't esp when a group 49 battery is involved. This law of nature.
If you decide to carry a battery in a battery box out to your car frequently, please be sure you install the battery in a battery box and lash it down using wide nylon straps over the top of the cover for it.
Otherwise, one quick swerve to avoid a pot hole or a car that tries to pull in front of you or something and you're likely to have a battery fly across the trunk and punch a dent in the trunk from the inside (I've see that before its not a pretty thing!)
Sorry but I have to vote against this solution.

Or chemisty :)

Would a basic Ford starter relay (or glowplug relay) that switches on with the key, work for starting and charging? Could I run the stock MB battery with a different model battery in the trunk (Think standard 700-800cca auto battery)?

But.......
 

I have to disagree, go and put a voltmeter on any hot wire in the car. When the gp's are engaged, voltage drops to any where between 10.5 to 8.5 volts. Having two batteries would mean twice the amperage supply, and half the load on each battery, which will reduce voltage sag, and increase voltage to plugs. Viola! more heat!

Simple logic....

It doesn't have to be a grp 49 battery
 

There are plenty of smaller batteries around that could give an large boost to any "nearly frozen" battery. And I think in the neighborhood of 20 to 25 pounds. But of course there are people who can hardly carry their own weight. I know that. But PawoSD seems to me to be a very active young man. And I would be surprised if he found carrying a small battery in a plastic case, say up to 1200 ft or two city blocks that difficult. But again maybe he would. That is his choice. But it is easily workable and not really expensive.
Regarding putting the battery in the trunk for a couple of hours, that too is a lot of hogwash. Batteries are tough and you can easily use the jel filled so there is no need to have battery acid running over the trunk. On his return trip he might be able to park very close to unload the battery back in Apartment or dorm. The cables will stay in the car. Now on my W123, there is a nice lower trunk floor on each side and that would nicely hold a battery from sliding around. I think PawoSD has a W124 and I don't know if that trunk floor has that arrangement. Also, I am old enough to know that these low tech "armstrong" solutions usually don't fly well. They work, but it's too simple.

I measured 11V at the GPs on my 300D while they were glowing, which is what they are rated for (with a single Interstate battery, about 1 year old). I suspect any modification that increased the GP voltage above 11V would also shorten their life. BTW, I have a small trickle charger installed next to my battery. Whenever it's cold enough to use the block heater, I also plug in the charge. It makes sure the battery is fully charged and keeps it warm.

On my 300SD I measure 11.5 or so volts at the glow plugs.

I think the losses here are not from the battery not having enough to put out but rather by the wiring.

If you want your glowplugs to get more V...then up the gauge of the wire feeding them.

Chances are you would only pick up a small amount of V if you paralleled another battery.

50amps vs 2 times 25-30 amps isn't that much difference for a good solid battery.

Now after the starter engages, that is another story...drawing 200-300amps to power the starter will cause a pretty decent vdrop and thus the glow plugs will see less v...

But unless you are going to be cranking for 10+ seconds, they aren't going to cool enough to care.

BTW for those interested, just go get a 100amp or larger 12v solenoid from your local parts place. Don't use a glowplug relay or something weird...just a plain old solenoid works fine. And they are pretty cheap.

If you find an old one off the firewall of a ford or something, go for it...just make sure it won't crap out on you :)

Ford Starter Solenoid:

Here's a thought I had concerning a second battery. Place it into the trunk with a starter solenoid in series under the hood. Connect a toggle switch to the solenoid and place under the dash. To connect the battery, you could use car amplifier wiring, or if you have the wiring already in place, tee into it with the solenoid in the trunk. Although I wouldn't try starting the car with this battery, it would be good to glowplug with, or give yourself a jump if the main battery gets low. Just let it sit for 5 or 10 minutes. Also would save you if you left headlights on, etc.

I'm certainly not an expert, but I have some experience with cold weather. I live in a climate that has is cold (-11C daily avg Nov-Mar, Extreem cold - -55C). I also have an uncle with a 2005 Ford PS in Tuktoyuktuk, NWT (find it on a map - you will like it) with the same practices. In both cases, without an electric block heater or a fuel-fired coolant heater, you are pretty much sunk. If you have ever tried to start a vehicle which has sat out for a length of time in the cold without being plugged in, if it does start, it isn't happy and unlikely that it is good for the motor.
My 7.3l (with the batteries the PO had in it 5 yrs ago) has dual batteries of differing ampacity with no fancy doo dads inbetween just a regular parrallel connection.
When the winter season decends upon us, I ensure the following - do the regular maintenance items (adjust valves, asess starter condition, change to lighter oil (or synthetic if you will), etc.) I also throw a very good set of booster cables in the trunk. Most northern places have plug in equipped parking spots, and I don't think I know anyone who has ever installed 2 block heaters. It usually only takes 3 hrs to warm up enough to start reasonably, unless it is very cold - at -40, I plug it in as soon as I shut it off. If you can't plug in, I would try to start and warm the car every 4 hrs as suggested by another poster, this is very helpful. I also have a cover over the rad to prevent wind from blowing through the rad and over the engine which will cool it much faster. I have also switched to synthetic transmission fluid and differential gear oil with no ill effects, as the transmission and differential aren't heated by the block heater.
I think that dual batteries is a good idea, if you find a good spot to install it. I don't think the isolator is a bad idea, I just don't know enough about it to comment.
I have been actively looking for a fuel fired coolant heater. If you watch e-bay long enough you should find one for around $500us. There are smaller ones that are better suited to our vehicles. This takes the pressure off of finding parking with electricity, and heats much faster than the electric model.
I think that the generator in the trunk might be a bit overkill, and possibly dangerous (fumes and so on).
Just my 2 cents.
Corey

Adding a Second Battery?
 

The 65 Amp alternator might have been big power back in their day but they are not these days, especially when there are so many of us converting to vegetable oil. Believe me, with a VO system, and all of the oil-heating power you need, more amps is a necessity. Don't know if you plan to convert to oil or not, but "Alternator & Starter" of Wichita, Kansas can build you a two-hundred amp alternator and match it to your alternator brackets. Thats what they just did for me. Give them a call at: (316) 265-8990. The owner's name is Nenad Dakovic. To keep his name simple, he goes by Ned. Tell him that Alfred Odom (owner of the Black 83 Mercedes) told you about him.

Peace.

Any problem with belts slipping or heat with that alternator? I guess you upgraded the wiring to match it.

...and the obvious question: How much $$$ did it cost?

Batteries, you don't need any extra stinkin batteries....
 

Just get one of the kero fired jet engine type heaters to carry inna trunk. That way you can just warm up the whole rig in one swoop. Just be carefull of melting anything you don't want melted, or burn yourself when loading it all back up into the trunk :silly: .

Regards

RUN-EM
HOWDY, from warmer than you, TEXAS, U.S.A.

My Suburban with the 6.5 had dual batteries from the factory and that thing started beautifully in the sub zero temps after sitting in the parking lot all day.
Most of the school buses that I've been dealing with have 2 or 3 batteries hard wired in parallel. The key is to get the same exact batteries and off the same pallet if possible with the same build date. Do yourself or the next owner a favor and punch out the dates on the new battery so someone has an idea of how old they are. I think dual batteries are a great idea. I also like the 115 amp alternator upgrade.