Cummins swap/frame question
FTE Legend
Joined: Jul 2010
Posts: 32,875
Likes: 48
From: Northeast, OK
Placing two batteries in parallel causes current between them since their resting voltages will never be exactly the same. As long as both batteries are good there is little harm, but even a weak cell on one battery can cause the good battery to lose charge. So many systems use a continuous-duty solenoid to parallel them when the engine is running.
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Post Fiend
Joined: Dec 2007
Posts: 8,521
Likes: 16
From: Lost
I know there is always the chance that 1 battery going bad can drain them both, but it's the simplest and most dependable setup in most any other case. It's not too hard to disconnect a battery (or both) to prevent a weak one from killing the stronger one.
FTE Legend
Joined: Jul 2010
Posts: 32,875
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From: Northeast, OK
I was just curious what your plans are. And I've not been around automotive battery systems for diesel vehicles, just recreational vehicles where you have to disconnect so you still have a starting battery the next morning. But in my experience years ago with a power company which had stationary batteries, leaving batteries in parallel was a no-no. Whether the guys were paranoid or really knew something I'm not sure, but they just would not leave batteries in parallel.
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Post Fiend
Joined: Dec 2007
Posts: 8,521
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From: Lost
The factory dual battery option in the 70's, had an isolator system. Worked well, most of the time........
I know that since 1983, when the first IDI powered Ford rolled off the line, they have not had any isolator system and have had 2 batteries.
I've been down the route of a large single battery in a diesel powered vehicle. The 80 VW diesel I owned. Thankfully, it was a manual trans and I lived where there was a hill to park on top of. On really cold days, that 1 battery was well taxed by running the glow plugs, and couldn't always spin the engine fast enough to start. A little assist by rolling down the hill and unloading the clutch, while cranking (no clutch interlock) would always bring it to life.
The boss's 05 F350 will start on cold mornings, but it sure doesn't crank as fast as it could. He plans to go back to a dual batteries, and hook up the intake grid heater, to make it start even better in cold weather.
I failed to mention this, but the engine I bought came with the entire underhood wiring harness, which means it will be uber simple to wire up the grid heater, using factory relays, and a manual control.
Haven't sorted thru that box of wiring enough to know if the battery cables and/or starter relay are there. If they are, they may be utilized in part or whole.
I know that since 1983, when the first IDI powered Ford rolled off the line, they have not had any isolator system and have had 2 batteries.
I've been down the route of a large single battery in a diesel powered vehicle. The 80 VW diesel I owned. Thankfully, it was a manual trans and I lived where there was a hill to park on top of. On really cold days, that 1 battery was well taxed by running the glow plugs, and couldn't always spin the engine fast enough to start. A little assist by rolling down the hill and unloading the clutch, while cranking (no clutch interlock) would always bring it to life.
The boss's 05 F350 will start on cold mornings, but it sure doesn't crank as fast as it could. He plans to go back to a dual batteries, and hook up the intake grid heater, to make it start even better in cold weather.
I failed to mention this, but the engine I bought came with the entire underhood wiring harness, which means it will be uber simple to wire up the grid heater, using factory relays, and a manual control.
Haven't sorted thru that box of wiring enough to know if the battery cables and/or starter relay are there. If they are, they may be utilized in part or whole.
Hotshot
Joined: Feb 2004
Posts: 11,697
Likes: 3
From: Marengo, Iowa
Dodge didn't use a starter relay, so you would need to add that. The heater grid uses two relays and heavy cables. This was for two stage heating. Our 92 IC starts in the winter on one battery with the grids currently non functional due to other issues. When it gets really cold, it does need to be plugged in, but that is just a diesel for you, they often won't fire if it is too cold no matter how well the spin.
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Post Fiend
Joined: Dec 2007
Posts: 8,521
Likes: 16
From: Lost
Dodge didn't use a starter relay, so you would need to add that. The heater grid uses two relays and heavy cables. This was for two stage heating. Our 92 IC starts in the winter on one battery with the grids currently non functional due to other issues. When it gets really cold, it does need to be plugged in, but that is just a diesel for you, they often won't fire if it is too cold no matter how well the spin.
I have seen the grid heater relays in that box, as well as the cables for the heater. With all that stuff on hand, might as well put in on, and hook it up, just in case I want/need to use it. It does help when the temp gets really cold, and most other diesels don't want to light off without a block heater and/or ether......
I don't even need to look to know the grid heater is still in place, since the intake pipe from the turbo is still attached at both ends, but I did look anyways......
Been tossing around an idea taken from some japan cars with turbos. A top mounted IC and hood scoop. I know they aren't as effective as a front mount, but room is rather limited up front. Besides, I think the truck would look rather cool with a scoop modeled after a 67 shelby hood scoop........
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Hotshot
Joined: Feb 2004
Posts: 11,697
Likes: 3
From: Marengo, Iowa
For your plans an IC isn't all that needed. That is more for when you are really working it. The IC is the same dimensions as the radiator. I was able to get it in on the 92, but with how the grill rakes back at the bottom, you run out of room.
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Post Fiend
Joined: Dec 2007
Posts: 8,521
Likes: 16
From: Lost
The grill issue is partly why I was thinking about going with a top mount. Of course, a front mount also reduces the ease of airflow thru the radiator.
I can find several disused top mount IC, and if I find one just the right dimensions, it should be a rather simple mod.
At this point, it's just a thought for down the road. Make it run/drive, then tinker with making any adjustments later.
Moderator
Joined: Jan 2001
Posts: 57,027
Likes: 2,762
From: Virginia
I was just curious what your plans are. And I've not been around automotive battery systems for diesel vehicles, just recreational vehicles where you have to disconnect so you still have a starting battery the next morning. But in my experience years ago with a power company which had stationary batteries, leaving batteries in parallel was a no-no. Whether the guys were paranoid or really knew something I'm not sure, but they just would not leave batteries in parallel.
You are correct also about isolation. If you are running different loads on each battery, yes they should be isolated, they will be in different states of discharge. But on these trucks, they are always connected together, they see the same loads and are drained the same amount, so they are both charged the same amount.
Basically they are one big battery split in two for mounting reasons. You could accomplish the same goal(enough capacity for glowplugs and starting) by putting one big battery in the bed of the truck.
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Post Fiend
Joined: Dec 2007
Posts: 8,521
Likes: 16
From: Lost
In these diesel trucks(and big rigs for that matter) the multiple batteries are considered one battery. That's the reason why when they are replaced, you should replace both at once. When he gets his project going, he should go out and get two brand new batteries. When you put a old battery with a new battery, the new battery is only good as the old battery that it's connected to.
You are correct also about isolation. If you are running different loads on each battery, yes they should be isolated, they will be in different states of discharge. But on these trucks, they are always connected together, they see the same loads and are drained the same amount, so they are both charged the same amount.
Basically they are one big battery split in two for mounting reasons. You could accomplish the same goal(enough capacity for glowplugs and starting) by putting one big battery in the bed of the truck.
You are correct also about isolation. If you are running different loads on each battery, yes they should be isolated, they will be in different states of discharge. But on these trucks, they are always connected together, they see the same loads and are drained the same amount, so they are both charged the same amount.
Basically they are one big battery split in two for mounting reasons. You could accomplish the same goal(enough capacity for glowplugs and starting) by putting one big battery in the bed of the truck.
The radiator has been on it's last legs too, didn't replace either due to the planned swap. I did replace the heater core since it was leaking, but I had already factored that into the swap. Just one, of many, items I can check off the list.
Pretty sure that's what the boss has in his 05, and it's mate is still hanging around the shop.
I may go with a pair 27 series, or 65 series. just depends on which are the better value at the time. I just put a new 27F in the 74. Starts much better now.
Postmaster
Joined: Mar 2013
Posts: 3,066
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From: Over There
FWIW I had the dual battery drainage issue. Two Optimas of different age/condition. They would take about 2-3 days to drain each other to the point that the engine wouldn't start. Optimas are unique in that they have low resistance so the problem is made worse. I solved it with a 500 Amp constant duty relay, figured good thing to have anyway vs two new batteries.
Intercooler in the hood, I think it could work well done right but it doesn't jive with your stated goals. You're not after power/high boost/EGTs and it hurts economy.
Intercooler in the hood, I think it could work well done right but it doesn't jive with your stated goals. You're not after power/high boost/EGTs and it hurts economy.