Another member told me he bought one Odyssey battery and then purchased the second one a month or two later. despite all the criticisms by others it worked out well and didnt hit pocket book so hard.

 

I ordered a F350 7.3 with a single battery because I have never had a single battery fail without warning on my HD gas trucks. For the last 13 years I have had diesels with dual batteries and alternators. Diesels require more CCAs especially in the cold. I have had one battery go requiring both to be replaced. I have had alternators on gaser and diesels fail, but not recently.

I do not believe dual batteries and alternators are needed on a 7.3 unless you are running several high amp accessories a lot. The 7.3 comes with a better alternator than I ran with old 460s pulling trailers, using winches and auxiliary lights. I never had problems in the past as long as the single battery is good. A weak battery will usually let you know with slow cranking before completely failing. I wanted the weight savings and simplicity of only one battery and alternator.

 

As shown in the wiring diagram example in this reply the factory installed dual batteries are wired in parallel, through the wires going down to the starter.

Whenever batteries are placed in parallel, it is very important that they are as identical as possible. That is identical manufacturer, part number and date code.

When batteries are not identical, then both the current drawn from the batteries and the recharging current provided to the batteries are different, with one working harder than the other.

 

I don't know if the alternator is mandatory with dual batteries as I didn't order. Truck came off dealer lot stock. But they show as separate options, with dual batteries $210 and the 397 amp alternator $115 on my window sticker.

 

I think it was when I added the snowplow/ camper package and the upfitter Switches together when it was forced to 397a & dual batteries.

 

Now that you mention it, I do also have snowplow package and upfitters. No camper package. But I haven't ordered a truck in some years so I can't really say which options mandate another. I do recall that sometimes if you tick one option, others automatically are added.

 

Thanks, but I am seriously considering a couple Walmart batteries. 5 year warranty (3yr free replacement, prorated after), and Walmarts are everywhere and have an easy return policy. Even if I have to replace them every 4 years as a precaution, I'll be ahead.
I bought one for my Bronco about 3 years ago now. Bronco had a faulty alternator, which drained the battery twice before I realized what was going on. Trans died in the Bronco, so I pulled the battery and have used it for the winch on my trailer every since. It lives on the floor of my garage for months at a time, and I hook a battery tender up to it a couple days before I use it. Still load tests perfect...

 

I guess I am in the minority on the single battery/alternator recommendation and the KISS ideology. I may even add a winch and air compressor to my truck, but have run both in the past with single batteries without issue. For me it works. A winch may be used once in a blue moon (when I or someone else gets stuck) and the compressor for airbags while occasionally camping if I add them. Truck levels out nicely stock right now so no air bags unless I get a heavier 5er. By all means if you a running heavy draw accessories all the time or plowing snow you need to get duals. If not I consider duals a liability and waste of payload. Also, the 2021 order guide is posted on another thread and specifies which options require duals. I am pretty sure snow plow package and diesel engine both require them, but not sure beyond that.

 

For a gas engine, I would stay with a single battery unless there are high amp loads from aftermarket devices.

Just for the record, I'm running RAID 5.

 

Resurrecting this thread with a related question:

I have an F350 6.7 on order. I'll be adding some auxiliary lighting, fridge, and a few other accessories. Rather than adding a third battery for the accessories, a friend (former automotive engineer) suggested I use the stock second battery for my accessories, and install a MPPT controller to keep that battery charged via solar when not driving.

Any overarching reason not to take that approach?

 

The OEM dual setup has both batteries paralleled. If you drain one, you drain the other. If there is any chance that your equipment could drain the starting batteries far enough to jeopardize starting the engine then a third battery connected via an isolator or a DC-DC charger would be the way to go.

 

I think for that you would want a 3rd battery.


Also on the gas you can add the second battery after purchase and isolate it and you have more options. The factory dual battery and dual alternator is good for like snow plows.

 

Maybe. Warranty. At least for the first 3 years 36,000 miles.

Since the stock batteries are wired in parallel, how do you plan on using only the second battery for for your auxiliary lighting, fridge, and a few other accessories?

If you separate the batteries, to where they no longer are in parallel while you are using the accessories, how do you plan to combine the batteries for when the high compression diesel engine needs the battery cranking power to turn over in cold weather?

Assuming you've got that all worked out with continuous duty relay that is flyback suppressed, let's get back to using those accessories... focusing on the fridge, since fridges are copious consumers of electrical power.

With the fridge loaded with whatever you refrigerate, you drive to wherever you go, and upon arrival, you disconnect the two batteries that are in parallel with each other, and run the fridge off of the second battery. The only available parking space is shaded by buildings or trees, and at this time of year the sun is low on the horizon, and, assuming that the truck mounted solar panels are fixed, and not mechanized to raise, tilt and swivel to track the sun, the production of replenishing current could not compete with the power consumption of the fridge all day. Or, even if in the middle of summer, and you camped all night someplace with no trees and no buildings in site, and the fridge kept the milk cold for breakfast the following morning... there was no sun at night.

So, next morning rolls around, and it's time to start the truck, during the coldest part of the day. Early morning. Since you separated the batteries, you know you have one good battery, even though the diesel engine calls for two batteries in parallel for starting. You tie in the second battery back again in parallel, even though you know it's depleted from running the fridge all day or all night, just so whatever is left of the second battery can help with the starting, and, so that once the engine is started, the alternator can charge it back up again during the drive home.

But, an overarching issue to consider is that once you parallel a good battery with a depleted battery, the good battery goes to work and it's higher charge of electrons starts moving over to the depleted battery at the speed of light. That's a load. The good battery is now charging the bad battery before turning the key. Add to this, another load that is imposed on the good battery before turning the key: Glow plugs. And a third load: Intake air heater. Fourth load: Electric fuel pump. Now start your engine... that's the fifth load, without even counting the gee whiz electronics loads that make everything tick.

The two batteries which are paraleled in a diesel engine application should be thought of and considered as ONE battery. One BIGGER battery, where a single battery has been determined to be inadequate by the manufacturer, that is why two batteries come standard, not optional. Larger diesel engine trucks come with 3 or 4 batteries, all wired in parallel, and all treated as ONE battery. The reason for multiple batteries being called to act as one battery is simply due to the fact that if the power potential of all those individual batteries were put into one case, a human being couldn't lift it or replace it. At least with lead acid chemistry.

With current (haha) Ford truck batteries of factory issue being famous for premature corrosion that wicks up and mucks up the oem battery connections and cables, all of which have been reported by FTE members on this very forum as needing to be replaced under the original bumper to bumper warranty... Ford may take advantage of your extracurricular wiring set up to point the finger at your rewiring as the root cause for a problem that likely would have occurred anyway, but you provided Ford an overarching reason to deny what would otherwise have been a legitimate claim.

But let's pretend none of that bothers you. You've put on the big boy pants with big pockets, and you'll happily pay for new batteries, even upgrade them to AGMs while your're at it. New cables, no problem. Make 'em 0000 and good to go. Just fine on my dime. That's all well and good, so let's talk about the MPPT that your automotive engineer proposes that you deploy.

A non linear Maximum Power Point Tracking charge controller "is a high-frequency DC to DC converter that changes the DC input from the solar panels to high-frequency AC, and then converts it back down to a different DC voltage and current to exactly match the panels to the batteries. MPPT's operate at very high audio frequencies, usually in the 20-80 kHz range. The advantage of high-frequency circuits is that they can be designed with very high-efficiency transformers and small components. The design of high-frequency circuits can be very tricky because of the problems with portions of the circuit "broadcasting" just like a radio transmitter causing radio and TV interference. Noise isolation and suppression becomes very important." (Quote paraphrased, with bold emphasis added.)

To the extent that there may be numerous Hall Effect sensors incorporated in the Ford powertrain, from camshaft position sensors to turbine speed shaft sensors to ABS sensors to any number of other rotational counting sensors that make the Ford truck know how to to go... the broadcast of stray AC, and the near field emission of high frequency noise, can cause interference with the signalling and communication from sensor to processor in the PCM, which may cause changes in power train behavior from the bad data received. That could be an overarching risk with the use of certain MPPTs, depending on which type and how it is deployed.

 

Why?

..............

 

Thank you for the detailed reply...lots I hadn't thought about.