5.4 Starting and House batteries - do they need to match?

[Nomadcat]

I'm talking about the starting battery under the hood and the Ford-installed "house" battery that's slung on the frame beam under the passenger side.

I'm planning to replace them both and wonder if they need to match or if I could put a deep cycle in the frame-rail battery.

I'll also look at the owners manual tonight, when I get home, and post here if I figure it out, but thought I'd call on the mighty collective wisdom here first for any thoughts and experiences.

Thank you.

Paul

[86Scotty]

I would say no. I wouldn't think that could possibly matter. In fact, you definitely want a start only battery under the hood and a deep cycle only on the frame rail.

[daveb]

It's one reason we have separators. Batteries of different types or even those of different ages of the same types can cause issues if banked together all hours of the day especially while setting W/O any charge being applied. It's one reason why diesel engines have frequent battery problems. They always only replace the bad battery but the life of the other battery isn't up to par and soon it bites the dust. As it goes down, it damages the other newer battery. So the problem continues...and so on...and so on. I'm thinking those Ford spare batteries don't have any way to separate themselves from the starting system. If so, you should replace them with two fresh batteries similar to each other. I also think (JMO) that solar has a tendency to lightly boil off wet cell batteries more than AGM's. Whether that is true or not, I've found that adding similar type batteries together seem to age less. If the controller is set to AGM type it's not good for the wet cell types and visa versa. It's not a huge thing but it does matter over time. You also should factor in heat and cold. AGM's get hit hard by cold weather but it really doesn't damage them from what the experts say. It does make them hold less of a charge. Wet batteries are similar but because it's best to keep AGM's above 50%, sometimes wet types excel in really frigid temps.
So whether you go with AGM's or the standard wet cell types depends on many factors, some of which are minimal. Hard to beat a set of Die Hard Sears AGM batteries. Many AGM's are designed for starting but a good wet cell is also worth looking at and warranty is the main goal. Something from Costco is worth looking into if you don't mind the work pulling them.

[schluchtenflitzer]

I am complete with daveb, a very good desciption of it.
One point more for solar:
Best charging for AGM is 14,4-14,8 V (depends on brand), for wet batteries it should be less otherwise they are boiling.

[Nomadcat]

Thanks, all, for your time and advice.

FYI - my house golf cart batteries are separated from my starting and Ford house batteries. Yes, the alternator charges them both - and solar also charges the golf cart batteries, but they are usually separated.

The manual says the following:

"A 72 ampere-hour, maintenance-free battery, mounted in the forward RH side of the engine compartment, is standard."

It then says:

"The dual frame-mounted battery option includes a remotely packaged frame-mounted 78 ampere-hour, maintenance-free battery. The auxiliary frame-mounted battery is located on the RH frame rail to the rear of the B-pillar. The auxiliary frame-mounted battery is used to supply the trailer circuits with power when the vehicle is not running. The auxiliary frame-mounted battery is connected in parallel with the battery. The auxiliary frame-mounted battery uses the same cable as the standard battery."

[daveb]

Paul, if the original battery is fairly new and you haven't killed it in the past, adding a similar type cheap priced battery probably won't be too much of an issue. Try to find a place that has a good warranty. But if you've added a high dollar battery, then I'd be more concerned.

[carringb]

They do not need to be the same. They aren't even the same from the factory. The Charging relay won't even close if the starting battery is low and need high-level charge. Once the starting battery comes up the PCM will engage the aux battery relay to allow it to charge.

I switched my frame-mounted battery to a deep cycle since it does power the inside lights on the trailer.

[daveb]

Originally Posted by carringb

They do not need to be the same. They aren't even the same from the factory. The Charging relay won't even close if the starting battery is low and need high-level charge.

I'd agree provided they are separated while the vehicle sits. For that matter basically anything with a separator is no difference than a typical SMB build. Sounds like you're saying the spare battery is completely on its own system. Actually that would be a nice setup. I'd be interested seeing what kind of battery separator Ford uses.

Most of our house batteries are different than the starting batteries but even if it does not separate while sitting, it doesn't mean you must have the same battery, only that in the long run it's better to have similar age, type, and size batteries banked together. I connect a motorcycle battery to my house system while camping all the time with no issues but I don't let it sit for days at a time while the vehicle is not in use.

[carringb]

Originally Posted by daveb

I'd be interested seeing what kind of battery separator Ford uses.

It's a large continuous duty relay. I think it may be the same as the glow-plug relays in the diesels. It looks the same. I've never had a single problem with it, even though I've run the aux battery WAYYY down many times running the inverter, and rely solely on the alternator+relay to charge it back up. With all the problems SMBs and other RVs have with their separators, I'm surprised they don't just use the Ford factory setup.

[daveb]

Originally Posted by carringb

It's a large continuous duty relay. With all the problems SMBs and other RVs have with their separators, I'm surprised they don't just use the Ford factory setup.

If I had known about em I would have looked at them closely.