New Wiring for Engine Batteries

Topic: New Wiring for Engine Batteries (Read 1239 times) previous topic - next topic

New Wiring for Engine Batteries

November 11, 2015, 07:51:03 pm

My Foretravel has two yellow tops for the engine battery bank. They have been acting a little squirrelly and it is about time to replace them. I had hoped to wait until the Spring, but they may already be past their working life, through no fault of their own (long story).

I am planning to replace them with three red tops. The new ones and my old ones both come with top terminals and side terminals. The Foretravel design used the top terminals. I have never had a vehicle that uses the side terminals.

Since I am going to have to rewire them, anyway, is there any benefit or reason to use the side terminals, instead of the top terminals? How does the bolted on side connector compare with the traditional tightened collar type of connection? I am wondering if there is any benefit (or contraindication) about the passage of current through the side contacts versus the top?

I have already decided to use 4/0 copper cables for the new wiring. This determination of how to connect them to the batteries is the next of several decisions in designing my new wiring system.

I would appreciate any feedback, suggestions, or advice from all my Foretravel buddies. Especially those that have BTDT.

Thanks,

Trent

Re: New Wiring for Engine Batteries

Reply #1 – November 11, 2015, 09:33:53 pm

Trent,

Look at the two choices-- I suspect there is more surface area using the top connectors.

And assuming these are 3 12 VDC batteries:

Battery 1 positive to battery 2 positive to battery 3 positive to engine positive.

Battery 3 negative to battery 2 negative to battery 1 negative to engine ground.

Re: New Wiring for Engine Batteries

Reply #2 – November 11, 2015, 10:08:13 pm

I like the top terminals on my 3 Optimal Yellow Tops. I got these because that was what was in there and that is what FT recommended. Lots of small parasitic loads if you are storing for any length of time without a battery minder smart charger. Lots of folks like the red tops.

Top terminals seem easier to access in my coach. Many are using one + cable from each battery to a bus bar and one - cable from each battery to a bus bar and then very big cables (or even two) to the starter. Dave M did something like this.

Re: New Wiring for Engine Batteries

Reply #3 – November 12, 2015, 12:43:42 am

Having heard no words of encouragement for the side posts, I plan to use the traditional top posts.

Brett, thank you for the description of the battery connections. That is the way my two battery system is configured (with the obvious difference).

Since I am going to three batteries, I will use two bus bars. At the moment, I am thinking 1/2" x 2" x 6" copper. I will have six equal-length 4/0 cables made up, 3 red and 3 black. Originally, I figured about 3' each, but I have stumbled on a really great idea, if it will work. Since the batteries are hanging out in an unprotected neighborhood, I will see if I can install the bus bars on the lower portion of the foot of the bed, where the isolator and boost solenoid hang out. That will REALLY simplify the rest of the engine battery wiring (I hope).

Has anyone tried wiring their engine batteries like this? Do you see any down side other than longer 4/0 runs to the bus bar?

Since I am having the cables custom made (or getting into that business),

I can choose my ring size. Is there an optimum size for bolts to attach cable lugs to a copper bus bar? What material; steel, stainless steel, brass, copper, unobtanium? I assume flat washers and not lock washers, right?

If I want to isolate a particular battery, it will be easy to disconnect it at the battery. If I want to disconnect the engine battery bank, it seems that a disconnect between the bus bar and the main wires would be simple, since I can reach it from the end of the bed. Should this be on the plus side, minus side, or both?

Okay, that is enough homework for tonight. Please continue this brainstorming session with your ideas and advice.

Thanks,

Trent

Re: New Wiring for Engine Batteries

Reply #4 – November 12, 2015, 06:24:19 am

FYI. I added a 3rd house battery and therefore had to redo my cables. I had Foretravel make a set to print since U295s/U320s of my vintage came with 3 batteries. I would guess that you could order your new cables from Foretravel if other coaches of your vintage came with 3 chassis batteries.

Rich

Re: New Wiring for Engine Batteries

Reply #5 – December 18, 2015, 11:56:53 pm

Bus Bar Update:

I have purchased my bus bar from eBay; it arrived yesterday. Unfortunately, it is one piece of copper, 1/2" thick, 4" wide, and 8" long (and *very* heavy; amazing what you can ship in a small USPS Priority Flat-Rate box). I plan to cut it in half, creating two bus bars, each 1/2" x 2" x 8".

The cutting part is what I need some coaching with. I have never worked with copper sheet or copper bars before. I know it is a soft metal, and expect it to cut similar to aluminum. I have cut aluminum with my miter saw, but that was only 1/8" thick. What would be the best approach to cut this 1/2" thick copper? I am using a sliding 10" carbide-toothed woodworking blade. It cannot cut the full 8" in one pass, but it will cut most of it and I can just flip it over and cut the final part.

Would it be better to try to make several shallow cuts, or just one all the way through? I know to go slow and let the blade do the work If it appears to be getting too hot, I can stop and let it cool off.

Is there a better blade to use? Would a saber saw with a metal blade be better for cutting it? Or should I give up on the electric power and just use a hack saw to cut the copper in half?

I could cut my work in half by making two 4" x 4" bus bars. I could then route the battery cables in at the bottom, and run the engine wiring out of the top half of each bus "square." I'm just brainstorming here (hard to do alone). What do y'all think?

Anybody BTDT? Any suggestions? All feedback welcome.

Thanks,

Trent

Re: New Wiring for Engine Batteries

Reply #6 – December 19, 2015, 01:36:12 am

A deep throat portable band saw is what I used...
Don

Re: New Wiring for Engine Batteries

Reply #7 – December 19, 2015, 02:35:54 am

metal bandsaw is by far your best bet, that is one massive chunk.

I used 1"x1/4" and bought a six foot length. It is small and cut very easily, and it is rated at 450 continuous amps.

Re: New Wiring for Engine Batteries

Reply #8 – December 19, 2015, 02:41:34 am

John,

I considered a band saw. In fact I own one; a brand new Craftsman 12" Electronic Band Saw that I bought at Sears about ten years ago. It has never been used. FTR, I had good intentions, but never got 'roundtuit.

It is one of the many hundreds of items I will have to dispose of before I can go full time. Right now, I can advertise it as never used. If I use it to cut the copper, then I could say "Used one time to make an eight inch cut!" Besides the mounted blade is probably not the right one to cut 1/2" copper.

Thanks for the suggestion. I'll put that on the list, but right now it is on the bottom (and the top).

Trent

P.S. Sorry about the flash flare on the picture; it's dark in my survivalist salt mine.

Re: New Wiring for Engine Batteries

Reply #9 – December 19, 2015, 08:00:16 am

Quote from: TulsaTrent – December 18, 2015, 11:56:53 pm

Or should I give up on the electric power and just use a hack saw to cut the copper in half?

That's what I would do, but I'm "Old School".

Re: New Wiring for Engine Batteries

Reply #10 – December 19, 2015, 08:34:07 am

Quote from: TulsaTrent – December 18, 2015, 11:56:53 pm

Bus Bar Update:

I have purchased my bus bar from eBay; it arrived yesterday. Unfortunately, it is one piece of copper, 1/2" thick, 4" wide, and 8" long (and *very* heavy; amazing what you can ship in a small USPS Priority Flat-Rate box). I plan to cut it in half, creating two bus bars, each 1/2" x 2" x 8".

The cutting part is what I need some coaching with. I have never worked with copper sheet or copper bars before. I know it is a soft metal, and expect it to cut similar to aluminum. I have cut aluminum with my miter saw, but that was only 1/8" thick. What would be the best approach to cut this 1/2" thick copper? I am using a sliding 10" carbide-toothed woodworking blade. It cannot cut the full 8" in one pass, but it will cut most of it and I can just flip it over and cut the final part.

Would it be better to try to make several shallow cuts, or just one all the way through? I know to go slow and let the blade do the work If it appears to be getting too hot, I can stop and let it cool off.

Is there a better blade to use? Would a saber saw with a metal blade be better for cutting it? Or should I give up on the electric power and just use a hack saw to cut the copper in half?

I could cut my work in half by making two 4" x 4" bus bars. I could then route the battery cables in at the bottom, and run the engine wiring out of the top half of each bus "square." I'm just brainstorming here (hard to do alone). What do y'all think?

Anybody BTDT? Any suggestions? All feedback welcome.

Thanks,

Trent

Trent,
here is a thread you may want to read first.......

Cutting copper on table saw?

hope the link works,

Re: New Wiring for Engine Batteries

Reply #11 – December 19, 2015, 10:07:47 am

If you used a hack saw it would have been done by now. Simple. Safe.

Re: New Wiring for Engine Batteries

Reply #12 – December 19, 2015, 10:42:42 am

Quote from: FourTravelers – December 19, 2015, 08:34:07 am

here is a thread you may want to read first.......

Thanks for the link, it was a good read.

Bottom line is that a table saw is too dangerous. A band saw would be less dangerous and easier to control, but still dangerous.

Trent

Re: New Wiring for Engine Batteries

Reply #13 – December 19, 2015, 10:46:24 am

Chuck and Roger,

Hack saw it is!

Thanks for the reality check. Besides, it might be a thinner blade cut.

Trent

Re: New Wiring for Engine Batteries

Reply #14 – December 19, 2015, 01:45:17 pm

Sometimes hand tools are the most efficient way of getting things done. Easily overlooked in these times of power tools and battery operated everything, good hand tools and the knowledge and skill to use them are being lost.

Re: New Wiring for Engine Batteries

Reply #15 – December 19, 2015, 02:23:20 pm

Quote from: Roger & Susan in Home2 – December 19, 2015, 01:45:17 pm

Sometimes hand tools are the most efficient way of getting things done. Easily overlooked in these times of power tools and battery operated everything, good hand tools and the knowledge and skill to use them are being lost.

I'm going to move your great comment to another thread.

Re: New Wiring for Engine Batteries

Reply #16 – January 03, 2016, 06:11:49 pm

I am ready to cut my 1/2" copper bar into two busbars, 2" x 8" each. But I started thinking again. My original plan was to use three 4-foot 4/0 wires from the positive and negative engine battery posts to the busbars.

In order to be able to disconnect the engine battery bank from the system, I decided to put a cutoff switch between the negative cables and the negative busbar. These will all be installed on the wall under the bed so I have easy access to them. I am looking for a battery disconnect that can handle 300-400 amps continuous, with 1,000 amps peaks. They are not cheap, and I need three of them!

So, I am back at the drawing board. If I cut the negative busbar in half, I would have two 2" x 4" busbars. Now I can have the negative battery cables go to one of these mini busbars, and all of the ground connections go to the other. I can then put ONE battery disconnect between those two mini busbars and be able to disconnect the entire engine battery bank, by turning one heavy duty switch.

Has anybody tried this? Do y'all think it would work?

One of the goals was to have equal length paths for all of the battery cable leads. If I went with the three disconnects, would I need to make the positive battery leads a little longer to keep the current paths the same length? If I go with my split negative busbar with one disconnect switch, would I have to extend the positive battery cables?

That's enough for one message. Please mull this over and let me know what y'all think.

Thanks,

Trent

Re: New Wiring for Engine Batteries

Reply #17 – January 03, 2016, 06:17:14 pm

You have the 8.3 but the M11 had starting issues. As you are under there anyway, I would make sure the ground wire is done again. Take it out and wire brush and use a flat washer instead of the star washer. On my coach I used the side terminal and ran them directly to the starter and let the other cables go the standard way thru that black junction box. That box robs amps from our coaches and in the heavy M11 especially in the winter you need all the amps you can get to turn the engine and the starter faster.

Re: New Wiring for Engine Batteries

Reply #18 – January 03, 2016, 06:54:33 pm

Quote from: TulsaTrent – January 03, 2016, 06:11:49 pm

I can then put ONE battery disconnect between those two mini busbars and be able to disconnect the entire engine battery bank, by turning one heavy duty switch.

Trent:

I wouldn't advise having the engine starter current go through a switch. Even though the switch may be rated to "handle" the current, it will introduce some resistance, and reduce current to the starter. Plus there will be 2 extra terminal connections in the circuit, with additional resistance from those.

If you want to be able to disconnect the engine batteries from the coach, it would be better to switch the positive cable that connects the engine batteries to the coach and leave the starter directly connected.

Re: New Wiring for Engine Batteries

Reply #19 – January 03, 2016, 07:49:15 pm

There is a 3 battery cable harness available that is a duplicate of the FT setup..
PENN BATTERY makes the setup. It comes in a Negative and a Positive (2) straps.
Amazon has them listed and w/shipping about $100 for the pair,
or call Penn and save yourself the aggravation.. pc

Re: New Wiring for Engine Batteries

Reply #20 – January 03, 2016, 08:06:48 pm

I'm not sure what you had in mind for using a switch but I installed an adjustable handle on the main output cable that allows me to disconnect the battery bank without tools but doesn't have the extra connection resistance of a switch. My reasoning is in the event of a severe short I can disconnect the battery bank in a hurry. The kind of event I'm speaking of is where you smell smoke don't know where it's coming from and need to stop it ASAP to prevent a fire. It happened to a fellow Foretraveler when his engine starter solenoid stuck and his starter stayed engaged even though the engine had started.
Here what I mean by an adjustable handle: McMaster-Carr

Re: New Wiring for Engine Batteries

Reply #21 – January 03, 2016, 08:24:18 pm

Quote from: JohnFitz – January 03, 2016, 08:06:48 pm

I'm not sure what you had in mind for using a switch but I installed an adjustable handle on the main output cable that allows me to disconnect the battery bank without tools but doesn't have the extra connection resistance of a switch. My reasoning is in the event of a severe short I can disconnect the battery bank in a hurry. The kind of event I'm speaking of is where you smell smoke don't know where it's coming from and need to stop it ASAP to prevent a fire. It happened to a fellow Foretraveler when his engine starter solenoid stuck and his starter stayed engaged even though the engine had started.
Here what I mean by an adjustable handle: McMaster-Carr

Not sure what you have the handle on, must be on a switch, or disconnect?

Re: New Wiring for Engine Batteries

Reply #22 – January 03, 2016, 09:11:13 pm

Quote from: jcus – January 03, 2016, 08:24:18 pm

Not sure what you have the handle on, must be on a switch, or disconnect?

Sorry for my poor description. I replaced the normal battery terminal nut with the handle.

P.S. @ the OP: I don't mean to imply that a switch is a bad idea. There are good marine battery switches that would work well. I would just make sure they will handle the current requirement for you engine.

Re: New Wiring for Engine Batteries

Reply #23 – January 03, 2016, 09:31:06 pm

@John

Thanks that pic tells the whole story.

Clever idea. I'll probably have to steal it.

see ya
ken

Re: New Wiring for Engine Batteries

Reply #24 – February 07, 2016, 04:29:07 pm

The busbar (first photo) is ready to be split and I think I have found the ideal placement for it.

The second picture is the passenger side of the engine bay looking from the open engine door. The location is the engine side of the under-bed electrical connection/equipment box. I have shown the two busbars staggered, because they might not fit side-by-side in the allotted space. I will probably add some backer material to make the installation more secure. Several of those big 4/0 cables and lugs do get pretty heavy.

Anyone see a problem with that location?

Thanks,

Trent

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