Start Battery

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Start Battery

May 31, 2017, 09:57:54 pm

Our Cat 3126 had a 4 year old 8D for the start batt. Previous owner changed the 3 Optima's out. It would normally start OK, but 1/3rd of the time, it would act like a low battery, until you boosted it. Then no problem.You could be driving for hours, and it would be fine, then a few hundred miles later (charging fine) it wouldn't start unless boosted.
This winter while parked in Yuma,I did a bunch of checks, Voltage was fine, connections all clean.I came close to pulling the starter to get rebuilt, but didn't have the right wrench, and the coach was sitting low in the rocks. So I decided to wait till I got home.
I did a load test once home, passed with flying colors. Then I did a Hydrometer test. One cell was weak. My friend went through this with his 1999 270 Cummins. He advised me to change to two group 31's.
I made a new tray that comes out if needed, and installed them with 4 ought welding wire. We can now drive the coach on the starter if needed!

Re: Start Battery

Reply #1 – May 31, 2017, 10:02:31 pm

I hope you meant 8D battery I would hate to see a bulldozer in that compartment.

Re: Start Battery

Reply #2 – May 31, 2017, 10:11:05 pm

Quote from: craneman – May 31, 2017, 10:02:31 pm

I hope you meant 8D battery I would hate to see a bulldozer in that compartment.

LOL, it's late. Thanks Chris

Re: Start Battery

Reply #3 – June 01, 2017, 09:31:41 am

Chris,

Need to move one wire:

Ground to battery #1.
Hot to battery #2.

Currently looks like both ground and hot are to the same battery.

Re: Start Battery

Reply #4 – June 01, 2017, 11:00:17 am

I downloaded and processed the battery photo a bit. The OEM cables look like they are attached to the rear batteries with a couple of big cables connecting the rear battery to the front one. While Brett has made the correct call here, perhaps the OEM cable at the back will not reach the front battery. If it will, it should be moved.

Pierce

Re: Start Battery

Reply #5 – June 01, 2017, 06:39:53 pm

I'm thinking that is how Foretravel configured the cables...mine is the same. I understand why Bretts comment makes sense though.
By the way my Dodge diesel is wired the same and the batteries are separated by the width of the vehicle.

Re: Start Battery

Reply #6 – June 01, 2017, 06:57:33 pm

Mine are wired the same,do we need to get with Foretravel to find out why?Was it something they missed?Not sure if one wire would
reach farther as they are cable tied together.What are the negative effects of this wiring?

Re: Start Battery

Reply #7 – June 01, 2017, 07:35:32 pm

Quote from: John44 – June 01, 2017, 06:57:33 pm

Mine are wired the same,do we need to get with Foretravel to find out why?Was it something they missed?Not sure if one wire would
reach farther as they are cable tied together.What are the negative effects of this wiring?

It's slightly more efficient to do it the way Brett suggested and more electrons may get delivered but very unlikely you would notice the difference. If my cables would not reach as shown in the photo, I would not worry about it. The cables from one battery to the other are huge.

Pierce

Re: Start Battery

Reply #8 – June 01, 2017, 08:35:57 pm

Taking the power off the end battery of a string for whatever reason cycles that battery harder than the rest.

Rotating them regularly would compensate for the tap location

Re: Start Battery

Reply #9 – June 01, 2017, 09:23:55 pm

With both positive and ground off the same battery, that battery is worked MUCH harder than the other battery.

Best for electrons to flow through the whole battery bank.

If neither cable is long enough to reach the second battery, all you need is a short additional cable. Install a bolt on any solid piece of metal near the batteries. Wire the OE ground cable to it. Install the new, short cable from that new "ground stud" to the second battery. Couple of bucks and 15 minutes of work will well extend battery life.

Re: Start Battery

Reply #10 – June 04, 2017, 11:24:31 pm

Quote from: Pierce & Gaylie Stewart – June 01, 2017, 11:00:17 am

I downloaded and processed the battery photo a bit. The OEM cables look like they are attached to the rear batteries with a couple of big cables connecting the rear battery to the front one. While Brett has made the correct call here, perhaps the OEM cable at the back will not reach the front battery. If it will, it should be moved.

Pierce

Thanks, they are 4 ought made from welding cables. NOS government surplus. $11.00 each on Ebay. Came in sealed package, already made up.

Re: Start Battery

Reply #11 – June 04, 2017, 11:28:07 pm

Quote from: wolfe10 – June 01, 2017, 09:23:55 pm

With both positive and ground off the same battery, that battery is worked MUCH harder than the other battery.

Best for electrons to flow through the whole battery bank.

If neither cable is long enough to reach the second battery, all you need is a short additional cable. Install a bolt on any solid piece of metal near the batteries. Wire the OE ground cable to it. Install the new, short cable from that new "ground stud" to the second battery. Couple of bucks and 15 minutes of work will well extend battery life.

Thanks. Makes sense. Most people don't realize, dc goes to ground, not to positive. I will say it started 20 times, hot and cold this weekend, on a 800 mile trip, with no boost.But I am all for battery life. I think one will reach the further post

Re: Start Battery

Reply #12 – June 04, 2017, 11:32:23 pm

Quote from: John44 – June 01, 2017, 06:57:33 pm

Mine are wired the same,do we need to get with Foretravel to find out why?Was it something they missed?Not sure if one wire would
reach farther as they are cable tied together.What are the negative effects of this wiring?

When I was a FT tech, we installed many like this. I even went to FT school several times, it was never brought up. Not meaning to change the subject, I do remember clearly the big discussion at FT battery school (via interstate) that sitting batteries on cement is OK.
Needing to sit on a piece of wood is a old wives tale. With that said, I still sit mine on wood...LOL

Re: Start Battery

Reply #13 – June 06, 2017, 10:30:50 am

I find that I confuse very easily. My start batteries are wired like the photo. Is that wrong and if so where should the wires go?

Re: Start Battery

Reply #14 – June 06, 2017, 11:14:59 am

Quote from: wolfe10 – June 01, 2017, 09:23:55 pm

With both positive and ground off the same battery, that battery is worked MUCH harder than the other battery.

Best for electrons to flow through the whole battery bank.

If neither cable is long enough to reach the second battery, all you need is a short additional cable. Install a bolt on any solid piece of metal near the batteries. Wire the OE ground cable to it. Install the new, short cable from that new "ground stud" to the second battery. Couple of bucks and 15 minutes of work will well extend battery life.

Done, both cable's reach the outer post's. Switched the positive's around. Had to play this one through in my mind a few times. The reality is, it makes sense.

Re: Start Battery

Reply #15 – June 06, 2017, 12:59:59 pm

In a perfect world every battery cable would be exactly the same size, lenght and condition both in and out.

Three shorter identical lenght cables on the positive side even if you have to coil the middle cable.

Same on the negative side.

Then two exact lenght cables from the junction points of the positive and negative cables to the load distribution area.

In absence of exact cabling lengths battery rotation can help equalize the batteries wear from cycling and loads.

Less work to make the cabling as perfect as possible I think. Especially when new batteries are being installed

Re: Start Battery

Reply #16 – June 06, 2017, 01:37:03 pm

It's the most important on the house batteries that cycle a lot, especially for dry campers like us. The start batteries are only used for just that and if they have a trickle charger connected when on shore power, they cycle very, very little. So, I doubt if the connections pictured would effect the lifespan. Our trickle charger is also hot with the inverter so while dry camping with the solar and inverter on, they are kept at 13V+. Nice to have it exactly right but in the start battery case, not as important.

Pierce

Re: Start Battery

Reply #17 – June 06, 2017, 01:52:55 pm

Quote from: lgshoup – June 06, 2017, 10:30:50 am

I find that I confuse very easily. My start batteries are wired like the photo. Is that wrong and if so where should the wires go?

With two 12V batteries wired in parallel like this (Pos-to-Pos, Neg-to-Neg, to make one larger 12V battery), the ideal wiring scenario is have the red wire coming from the engine to connect to the first battery in the chain, and the black wire connect to the last battery in the chain. Or vice versa, doesn't matter which. Either way, power is flowing through the whole bank, both during the discharge and the charging process.

If you wire the black and red from the engine to the first battery only - the 1st battery does the majority of the heavy lifting, both when charging and discharging, and only pulls from (or gives to) the 2nd battery when there is voltage differential.

You actually don't lose that much starting power when wiring both sides to the first battery, but that first battery will wear out more quickly (which, in turn will wear out the 2nd battery quicker unless you immediately recognize the 1st battery is on it's way out).

As others have said, it's more important for your house battery not to be wired like the photo (because of slow discharge, and more time at float charge). Engine batteries, you can get away with it for longer (although I still feel Brett's suggestion should be followed if at all possible).

Re: Start Battery

Reply #18 – June 06, 2017, 02:27:25 pm

Quote from: Blinded04 – June 06, 2017, 01:52:55 pm

With two 12V batteries wired in parallel like this (Pos-to-Pos, Neg-to-Neg, to make one larger 12V battery), the ideal wiring scenario is have the red wire coming from the engine to connect to the first battery in the chain, and the black wire connect to the last battery in the chain. Or vice versa, doesn't matter which. Either way, power is flowing through the whole bank, both during the discharge and the charging process.

If you wire the black and red from the engine to the first battery only - the 1st battery does the majority of the heavy lifting, both when charging and discharging, and only pulls from (or gives to) the 2nd battery when there is voltage differential.

You actually don't lose that much starting power when wiring both sides to the first battery, but that first battery will wear out more quickly (which, in turn will wear out the 2nd battery quicker unless you immediately recognize the 1st battery is on it's way out).

As others have said, it's more important for your house battery not to be wired like the photo (because of slow discharge, and more time at float charge). Engine batteries, you can get away with it for longer (although I still feel Brett's suggestion should be followed if at all possible).

Exactly right if you do the wiring from scratch or you can move the one of the cables to make it one big battery. Deep cycle coach batteries can see 40% discharge so very important to have them wired correctly. Our start batteries see less than one tenth of one percent discharge to start the coach so the "heavy lifting" is for perhaps two seconds, not enough to be noticeable. After starting, the batteries are up to float voltage in a couple of minutes.

Foretravel incorrectly wired our three start batteries with both cables coming off the middle battery. I ran another ground cable off the middle battery but otherwise, have left it alone. I installed the three Duralast 34 series coming up on eight years ago and they are still reading the same voltage on each one and still start the coach like the day I installed them. Sometimes the perfect world runs up against the real world.

Jimmy is very happy with his three 31 series and loves the way the engine turns over. Everyone's engine should turn over and start like his. If it does not, you have a starting system fault. You should never, never, never have to use the boost switch/solenoid. If you do, you are masking a problem. Failing to address the fault will shorten the life of starting system components from the batteries to the starter motor.

Pierce

Re: Start Battery

Reply #19 – June 06, 2017, 02:54:55 pm

My guru buddy had issues with auto combiners masking bad engine batteries where the newer combiner dis connects when starting under auto so the engine start batteries true condition can be shown

Re: Start Battery

Reply #20 – June 06, 2017, 03:20:04 pm

Quote from: Caflashbob – June 06, 2017, 02:54:55 pm

My guru buddy had issues with auto combiners masking bad engine batteries where the newer combiner dis connects when starting under auto so the engine start batteries true condition can be shown

Bob,

If you have adequate engine batteries, why in the world would you need any kind of auto combiner? My diesel tractor, several diesel cars only have one battery and do fine without a "spare" battery. Our fire trucks had two 8Ds for starting but also no spare.

To me, it's a case of the owner not doing any engine battery and related components maintenance so they use the boost switch to mask the shortcoming. Do it like Jimmy and maintain it then you will never have the need.

Pierce

Re: Start Battery

Reply #21 – June 06, 2017, 04:44:35 pm

That's the point. He no longer uses the auto combiner on starting designs that were the only ones available.

The new units on auto do not combine the batteries anymore.

That's we he installed on ours.

He has 17 years of customers and things evolve.

Re: Start Battery

Reply #22 – June 06, 2017, 05:01:01 pm

Quote from: Pierce & Gaylie Stewart – June 06, 2017, 02:27:25 pm

Our start batteries see less than one tenth of one percent discharge to start the coach so the "heavy lifting" is for perhaps two seconds, not enough to be noticeable.

Pierce

Maybe so on your Detroit without a air intake
manifold heater. Probably not a bad idea to use the Boost switch on a cold day with the Cummins. If not just extra work for the alternator to bring back the chassis batteries.

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