Adding a Second Battery?
 

I noticed a couple months ago when I was at the auto-show here in Grand Rapids, that all of the bigger diesel vehicles on Display had DUAL 100amp batteries in them, such as the Dodge Cummins Pickup, the Chevy DuraMax, the Ford Powerstroke.....and such. They all had two 100amp batteries up front in the engine compartment, from what I could tell by inspecting it, is that they were rigged in parallel, to produce the normal 12.5-13 volts, but with twice the amps. I've heard powerstrokes and Cummins trucks start up, and their starters sound insanely powerful :eek: I've always wondered what advantage it would give on a car such as mine, with a 617, to have a parallel battery setup like that, as it gets real cold here, and in the fall I'll be going up to the edge of canada for school, and I'm still going to need my car, but the chances of having an outlet for the block heater at school are pretty slim, so I was thinking that if I set up a dual battery system like that it'd give me a lot more juice on startup, the glow plugs would get hotter since two batteries would be sharing the load, and the starter would have a whole lot more amps to work with allowing it to crank faster and longer. Mainly I'd like to make the chances of not being able to start it in those conditions very low or non existant. I'll be doing a valve adjustment and stuff before I go there, but I need it to start in temps probably as low on occassion as -10, maybe lower, I hope not. So what boost would a dual/parrallel battery system give?

First off, I think that you mean 1000 amp batteries in those cummins you speak of...

They sell kits you can buy to rig up a two battery system, last ones I saw were on the JCwhitney website.

Yeah thats what I meant, the "1000 cranking amp" ones. My MB OEM battery that died in December just said "100 amp" on it. My new Diehard says 1000 cranking amps. What I wonder is though, how much advantage would it give to have the dual setup, I'm thinking it'd be quite beneficial since quite often when its that cold my battery holds out alllmost long enough to get it going, but then it reaches the point where its coughing and starting to fire, but then it slows down and looses it when the battery gives out, with two it'd keep it up and get going.

Wouldn't give any advantage.. if you have problems starting your car, you need to find the source of those problems (glow plugs, starter, compression, etc). Mercedes designed the electrical system to work perfectly starting the car.

The trucks have two batteries for a reason, it takes ALOT of energy to fire the glow plugs and spin that much bigger diesel engine over in sub zero temperatures to get it running. Also, these trucks were designed for towing, and alot of trailers have electric brakes and alot of lights. As a side note, most big rig trucks have high pressure pneumatic starters.

My question is... where would you put the second battery? :confused:

I really don't see the need for dual batts, just get a strong single and a good alt. I found a place that'll build a 90A in the stock case... not great but better than 65A. Vehicle was engineered for a single battery

Sorry John, got to strongly disagree with you on this one. If this fellow is going to routinely be starting in below 0°F. ambients, a single battery is definitely marginal unless the engine compression is absolutely at the top of its range.

For an older vehicle with some hours on the engine, it may need 15 seconds of crank time at these (or lower) temperatures. A single battery is very much up against the wall under these conditions. The battery output is severely reduced due to the cold and the requirement from the engine for the maximum possible crank speed is increased due to the heavy suction of heat by the cold block.

Two batteries can maintain a higher voltage for a longer period of time. This benefit cannot be easily dismissed when starting these engines at 0°F. without the benefit of a block heater.

Alot of people have these cars in VERY cold climates.. you don't see them installing an additional battery. Even parts of Europe get extremely cold, where many more diesels lived than over here. I've never had a problem starting any of my diesels in 0F temperatures.. The car is designed to start with one battery if all systems are operational. Sure, a 2nd battery couldn't hurt, but it isn't needed if all systems are in working order, in my opinion.

If the temps were -5 or higher I wouldn't be worried so much, but I'm talking about being parked 2 miles from lake superior, I may have days where its -15 out and I need to use the car. Mine is able to get going fairly quickly when its -5 or higher, but below that seems to be the threshold where the battery gives out before I can get it firing good enough to start.

They generally use a block heater, and/or don't shut the engine off for more than four hours so there is residual heat in the block.

I can't imagine attempting a cold start every morning at -10°F. without the benefit of a block heater. It would have to be touch and go with 15-30 seconds of crank time.

I still recall starting the SD around 8°F. Slow crank speed and at least six seconds before it would fire. Every degree below this makes a significant difference.

To attempt to start a diesel under these conditions is absolutely brutal for a battery. Using two batteries would provide a higher initial voltage to the starter, thereby increasing crank speed, and would additionally provide double the crank time before the juice runs out.

I've been reading the weather almanac for Sault Ste Marie MI to see what the temp extremes usually are, and some of the records for the winter have been as low as -40!!!!!!!!!!!!!!!!! :eek: :eek: :eek: I wonder if a gasser would even work at those temps, probably not. Most of the "averages" however seem to be between 2 degrees and 10 degrees between november and february....thats still pretty low though. I bet I could start on one battery in those temps with a fresh valve adjustment, but I am also paranoid, and having a second one in there with extra available crank time would give a piece of mind too, since I will be in college parking lot, and not at my house where it not starting wouldn't be as big of a deal. I don't want to be sitting out in that parking lot with a dead battery.

I have seen a dual battery equipped W123,
 

but the second battery was there to power a 12 volt block heater which was controlled by an automatic timer clock on the dash, to the left of the steering, and the electical system had one of those camper type isolating systems so that the block heater couldn't draw down the main battery. I've been told that these kits are fairly common in the northeastern states and provinces and Scandinavia, especially for people who have to park all day in an open company parking lot. The extra battery was positioned symmetrically with the regular battery on the driver's side under the cowl, so I suppose that the regular fuse box had to be moved a bit, etc.

My guess is that the space at the extreme forward part of the trunk would be a good place for a second battery. You'd want huge cable, bigger than stock to reduce resistance. That being said, you really owe it to yourself to cover the other bases too, such as glow plugs, valve and IP timing, compression check, a proper oil, etc. The compression check is, IMHO, the thing you really have to do. If it's not strong, you might want to rethink the whole thing.

my 2 cents for 2nd battery
 

The second battery I carry in my trunk has helped me through a cold winter here in Peterborough, northeast of Toronto. On really cold mornings (below -15c), even with the block heater running for 2+ hours, my battery just doesn't have the juice to turn the engine fast enough to get going. I keep a battery in the trunk and "jump" it to my car battery on these occasions. It gives me enough cranking power to start on these cold days.

For next winter, I'm making it official and running a wire back to the trunk where I'll mount this battery in a marine-type battery box and ground it locally in the trunk.

In other words, I say DO IT!

And keep in mind....if you run parrallel batteries remember when replacement time comes you have to replace them in pairs...even if one dies becasue the weak battery will drain the strong battery.

Yeah that's reason I have heard why batteries don't like to be connected in parrallel. One battery may pull the other battery down. That's why most battery banks are connected in series. Too bad they don't make super duty 6 volt batteries...

I recommend you move south....

Actually, the worst thing that can happen with a parallel dual battery system
 

is not that the bad baddery pulls down the good one, but that the bad baddery keeps the alternator overcharging too strongly and boils the fluid out of the good battery very rapidly. I discovered such problems back home in Minnesota about 40 years ago when I dropped a '64 1/2 260 Mustang V8 with cast iron Cruisomatic from a police car into my '40 Ford Pickup and tried to use two very narrow 12 volt batteries ('56 Ford style?), one on each side of the engine.

The Good battery tries to bring the weak battery up to a parity (charge it)...which does pull it down....when its not running.

Yeah both batteries would be new if I went ahead with it, at the very least I'll carry a second one in the trunk to jump it like 80benz does. That way if it turns out being sufficient to do that then I won't bother with installing two. I'll probably only do an actual installation like that if it is really truly needed. My other alternative is to buy a bucket, with a lid, or a container with wheels, and just fill it with 5-10 gallons of hotwater and head on out to the car, pop the hood, and pour away.... :D :D :D Holding up my tradition of what I do around here when its that cold. :D

For what it's worth I have seen a couple of 617s converted to two batteries. the one battery affecting the other during charge could be dealt with electrically by isolation methods if required. In my humble opinion it's going to help but not totally overcome all the very low ambient temperatures where you are going. The two cars I saw had the extra batteries under their respective hoods. The four hour restart and warm up mentioned in earlier post would still apply on some days. Have always thought a 1000 watt generator mounted in trunk with exhaust plumbed out would have to be incorporated in any 617 that had to be used in a really cold climate where electricity was not available. They are small and pretty quiet plus the right current to drive the block heater. Only for those places where you cannot plug in. Of course that would mean having to go out and start the generator a couple of hours before departure or even longer if -30 that day. I think that size gas generator can be had for a reasonable price and consumes little fuel. Only thing I would want to be sure of is that the generator was capable of starting at that low a temperature before purchase. I know if that generator did not start when needed ones normal vocabulary might increase somewhat. Also aids in overcoming the engine not quite as good as new effect. :sun_smile

Buy a gas car.

I had no problem -2 this year without the block heater, she fired right off. My new battery cranked the engine over with plenty of speed.

If you want to run two batteries you will have to put them in the trunk. Then run some massive cables up front. It shouldn't be to hard, it will just cost a few bucks. Also buy two large marine batterys, something with a lot of reserve power.

But this is only the begining:
Get a rebuilt starter
adjust your valves
make sure your compression is very good
Mobil 1 5w-40 or 0w-40
Replace your glow plugs
Use a lot of anti gel

Get rides in friends gas cars. :D

portable charger??
 

couldn't you use the 12v charger that is sold at places like sears and checker? these are charged and used if the battery is not strong enough to start the car. reading the box it says to charge it and put it in the trunk.

I want to see the proof of cars that start at -10F. I want to see one of those cars sit for more than 24 hours and then start. I have 5, 617's that don't even sip oil in 3k (good compression) and all of them have their limits on a cold, 24-hour start up. Some limit out at 5 degrees and some near 14 degrees but they all have their limits.

I considered the dual battery hook up (like an RV with isolation) to drive the block heater (with timer), but it didn't appear to be able to kick out the juice.

So, with my daughters being away at college, we have this rule. If its under 10 degrees at night, you let the beast run all night.

It only happened four times this winter where we needed the car in running order early in the morning.

Idle..........its the benefit of running a diesel :)

Otherwise, I like the 4 hour rule.

dp

If I left my car running at SCSU it would either be stolen or the cops would give me a ticket.

Bummer on getting a ticket for idling.

My brother is a long-haul trucker and they get tickets now out on the West Coast for idling. The other day an officer came up to him (in CA) and knocked on his window. The officer informed him that he was going to get a ticket. As he started to write the ticket, my brother's small poodle jumped up on the dash.

The officer noticed the dog and said, 'oh, I didn't know you had a dog in there. I guess you had to keep the cab cooled down for the pup' and preceeded to walk away.

So far, that stinkin dog has saved us 3 tickets. Two for idling and one for speeding.

Its ok to idle for a dog but don't you dare idle for your own comfort :)

I could have installed a cord into my car but decided against it. The car already has a block heater there. Remove the cap and install the cord if you want. Winters are not that harsh here anymore. You know, my diesel contributes to the global warming and all that crap from some whacko evironmentalist. Wait, redundency there. shoulda stopped at either whacko or environmentalist. Anyways, the way we figured it, the car sits in a garage and never has to sit outside. It is always above freezing in the garage. Even if we had the cord installed, if the wife parks it at a parking ramp, they have no electrical outlets. No help. Besides, I have batteries in the garage. In fact, I even have a battery out of my wrecked C280 that anyone here can have for the low, low price of "YOU PICK IT UP" and a bottle of Coke, not crapsi, Classic Coke.

http://www.peachparts.com/shopforum/mercedes-benz-used-parts-sale-wanted/118475-battery-99-c280-almost-free.html#post845668

Some places in Minnesota do have outlets on the parking meters,
 

specifically for car engine heaters, block, tank, or whatever, and they're popular even with the gasburner drivers, because the heater and defroster then perform instantly. I think they have them at Bemidji State College, for instance. Years ago already it was 25 cents per hour, though. Some apartment complexes in Minneapolis/St. Paul also having things that look like decorative hitching posts from the horse and buggy days, but are really mounted outlets, each wired into the appropriate apartment's electric meter.

I'm not sure that this will solve your specific cold start power dilemma but I do know that this method works for installing twin batteries.

Use an isolator to automatically select the battery that needs charging. Use a battery selector switch also. This way you can select bat #1, bat #2, or both. It even has a switch position to cut off both batteries.

I use this rig on my truck since it often sits for months without being driven or started. The alarm and clock will eventually drain the #1 battery flat enough that it won't start the engine. Simply select bat#2 and it starts right up.

I am going to send off an e-mail or maybe ask them the next time I call if there'd be a place I could park that has an outlet within reasonable distance, and if I could use it to power a block heater, especially since it'd only be for the 3-4 hours prior to having to use the car, I'd have no problem with going out there and plugging it in ahead of time, everywhere on campus can be walked to in less than 5 minutes, so thats no problem. Aside from that, I'd probably put an extra battery in anyways, for piece of mind. I'd also be switching to a lighter oil and I'd have my valves and such adjusted. I don't think I'd have much problem if I equipped myself like that. I was wondering though, is there more than one coolant plug on the engine where one could install a second block heater? So I could have two of them....doubling the speed/heat capacity...... I have been looking at small generators, and this is also a very likely path I'd take, A good Coleman Powermate 1000 or 1500 watt generator costs not much more than a battery would, so I am highly considering that instead, one of those could power everything from a charger to a block heater to a heated battery blanket, making startups very easy. Piping the exhaust out of the trunk wouldn't be too hard either.

Just buy one of those outlets that screws into a lamp socket. That way you can borrow some power at night from an outside light...

Ha, I wonder what campus patrol would do if they saw me plugging my car in like that :D

Two batteries would definitely help winter starting. Mounting the 2nd battery in a marine box in the truck with heavy cable, like 00 welding cable for the + going forward and a good solid ground cable of at least 4gauge. Inspecting/replacing and/or increasing the battery cable diameter is a overlooked area. Poor cable condition will not allow enough juice to the starter and result in slow cranking. I have custom cables on the truck and the Jetta that doubled the cable size. The difference was noticeable. Another overlooked area is the engine ground. Increasing cable size or battery capacity ain't worth a hill of beans if the juice can't get through. Inspect and replace the engine ground as well. I have (2) 2gauge grounds on the truck. Lastly, you may be better served by a fuel-fired engine heater. They are small and pricey but they can be moved from vehicle to vehicle so it should serve you a long time. Check out: http://www.espar.com/htm/Specs/water/D4Wspec.htm
http://www.lubricationspecialistllc.com/index.php?cPath=8&html=espar.htm&osCsid=8968ff3a8dc7e8a7f8afe2cd1418d460

RT

Those are a bit expensive :eek: If I can't get my hands on an outlet then I'll just get a generator, they're way cheap on ebay. I am fairly confident I'd be able to find an outlet though, its so cold up there, they'd have to be a bit lenient in letting me use one for that.

Dueling battery syndrome I believe it's called...

Would an isolater alleviate this problem? I believe Painless wiring has one...

You must use a Isolator to employ two batteries with one charger, just hard wiring them in parallel is inviting disaster. Cadillac used 2 batteries in parallel on the diesel Biarritz, I had a friend that experienced an explosion in one when one of the batteries shorted and blew its guts, I believe they were in the trunk space. A proper isolator charges each battery independently. If one battery has a shorted cell, it must be isolated from the other battery by the diodes in the isolator, to preventing excessive current discharge that may occur.

Out of pure curiosity, is it possible to put two of the standard block heaters on one engine? Or is there only one spot for them, I just placed an order at fastlane for a set of all new (rubber) brake lines, a couple liters of brake fluid, an extra caliper mounting bolt, and a Block Heater Kit. If its possible to install two block heaters I would do it, when I am up north I'll need all the heat I can get! :D

Do you plan on being the first Benz to drive to the north pole?

Don't think there are any outlets there to plug into.

Santa has outlets on the outside of his workshop for sleigh heaters, so he'll just let me use one of those, he's a giving guy anyways. :D ;)

On the North Slope there are a lot of diesels, including pick-up trucks,
 

but they just never shut them off unless they take them inside a heated building for service. The service shops have heated concrete floors, too. Diesels can be cozy in the Arctic, but it requires extreme measures.

Brain Fart!
 

How about this....

I'm going to add an intake air heater from a 5.9 cummins to the 240D when all is said and done by welding a mounting flange to the intake (Lucky I know somebody that can weld aluminium :D ).

Insted of another 850cca+ battery, would a small 200-350cca (Think lawn tractor) battery connected ONLY to the glowplugs and IAH work? With an isolator and proper cabels...

That would be 80A + another 80A(?) at once that the cranking battery at 5*f would not have to give up.

Everyone has forgotten to address his issue of glow plugs
 

I don't think his glow plugs are going to get any hotter....

Right now I just need help in how to remove the oil cooler lines from the oil filter housing.....tips in doing this would be great.....


As for the glow plugs, I'd think they'd work better with twice the powersupply since the load of the other plugs on the single battery is cut in half, thus making more voltage/amps available to each glow plug, so how would they not get any hotter?

The heat the glow plugs radiate is determined by
 

the current flow thru the filament. The current flow is determined by the resistance of the filament and the voldage applied to it. In the case of two batteries connected in parallel, the voltage to the filament remains the same, so also does the current thru said filament.

Now, is you really want to heat things up then connect the two batteries in series - - - 'course you will immediately burn out at least one glow plug and any other 12v device that happened to be hooked up/turned on at time(since there would be 24v. applied rather than 12v....

I do agree with the other folks that your starter will rotate faster and longer with them hooked in parallel. :)

What is all the hoopla about 2 batteries. I have had 2 GMC 6.2 lt. Diesel trucks. Both have 2 batteries, neither has any sort of isolation switch, and the system seems to work well.

Instead of getting 1000 CCA batteries it is better to get as large as possible a battery that will fit into your battery box but with about 650CCA. Lower CCA batteries last longer, esp in the heat of summer.

My 107 450slc (which is the same chasis as my 115/300D) has the battery in the trunk and it works well. The 115 has the battery in the engine compt. but I see no reason why a second one couldn't be added in the trunk. Both battery cables could be attached at the starter solinoid.

I installed my battery in the trunk of the 220 (W115) when I needed room for the Crane Ignition modules (CD ign). It was fun, running the hot lead (2 GA?) in a liquitite conduit along the bottom of the car. Second photo shows the air storage tank and compressor. The sound system is next.

Can an optima red top battery be combined (in parallel) with a standard sears diehard without one attempting to drag down the other?

Love the on board air. What are you using it for? does your small compressor and tank provide enough for short bursts with air tools? Are you just inflating things? I've been thinking about a compressor & tank set up for my truck for inflation of float bags (canoe) tires...What sort of compressor do you have there?

AS for dual batteries? I like the idea but need to get my car running properly with 1 first:rolleyes:

Not unless they are electricly isolated from each other...

The optima charges to a slightly higher voltage than your average lead-acid battery...

Pairs of batteries hardwired together need to be same age and same type....

How do I know...read my sig....I have a Truck with dual batteries..(and an electronics degree)

better watch your daughters.


:D :D

I bought a 12 volt Thomas compressor on eBay that will push up to 120 psi. The tank was a small one that I bought locally and its great for an air horn. You can also fill tires with it and I use it for blowing leaves out of the places where they love to fall and get trapped (every Mercedes I've ever owned has several places for leaves :( )
I have no plans to even try using an air tool on it, unless it was a nailer maybe, because anything that uses lots of air will cause the compressor to run all the time, and these are intermittent use compressors. Besides they draw about 15 Amps, they run hot and the motor will die if it runs continuously.
There are two ways to plumb air up to the front (unless you wanted rear facing horns?) One is to send pressure up front and put the solenoid valve on the horns, its short wiring hop. The other way (which I am using) is to place the valve at the compressor and run wires back to it from the existing electrical horns, this way the pressure is not on that line all the time and I think it will be happier and last longer in the long run. Either way you have a small hose to run. I used 1/4 in black cpvc because the white semi translucent pvc hose isn't any good because it will crack from exposure to UV

The use of a second battery is no problem as long as you use a battery isolator. The two batteries can be different as long as they are charged through the isolator and they require the same or very close to the same charging voltage. Sure Power makes a good isolator.
One important note: DO NOT hard wire batteries in parallel, that's askling for a disaster when/if one shorts it will pull the other down and one of them usually explodes and spurts acid all over everything. This was a big mistake that Cadillac made in the '83 Diesel Brougham (besides trying to make a diesel engine!). I knew someone who had that happen in one and it wasn't pretty!