House batteries

[Cajun2Stepp]

just wondering...why do I need four 6 volt house batteries to power up the coach?
I always run the generator while under way to power the a/c's and residential refrigerator, and NEVER dry camp.
Why couldn't I save $400.00 and just run a deep a single 12 volt deep cycle battery?
Thoughts?

[ArtJoyce]

If you have a propane fridge? I don't see why you need those batteries. One 12v deep cycle would be fine.

[RonandDeb]

Since you never dry camp and are always on either generator or shore power, you could easily downgrade to just one battery.

Just remember that you've done so moving forward as your battery power could deplete very quickly.

Otherwise, you're good to go.

Personally, I thought about replacing my two deep cycle batteries with one lithium.

[Teamfoxy]

We have run on two 6v golf cart batteries for 3 years now. They still check out fine with a hydrometer. I would not change mine to a single 12V of any type.

[andy29847]

On my coach, the batteries are the sole source of 12v DC power. You need 12v to run the refrigerator, furnace, ACs, the stove, some lights, and maybe some other stuff I am forgetting, even when hooked to shore power. Your inverter/charger supplies charging voltage to the house batteries to help them keep up with the demand.

One function of the house batteries that I haven't used but one time is to assist starting the engine when the chassis batteries are low. If you are lucky, you never need the boost button. If you are unlucky, you will probably want at least 2 batteries.

I made this illustration of how the power works in my coach. I expect yours is similar.

[RonandDeb]

Originally Posted by andy29847

On my coach, the batteries are the sole source of 12v DC power. You need 12v to run the refrigerator, furnace, ACs, the stove, some lights, and maybe some other stuff I am forgetting, even when hooked to shore power. Your inverter/charger supplies charging voltage to the house batteries to help them keep up with the demand.

One function of the house batteries that I haven't used but one time is to assist starting the engine when the chassis batteries are low. If you are lucky, you never need the boost button. If you are unlucky, you will probably want at least 2 batteries.

Good stuff!! Thanks for sharing

[Judge64]

You don't say what type of coach you have but.....

The house batteries provide power for slides and leveling jacks. Depending on the slize of slides and weight of the coach, the engine needs to be running to boost the house battery voltage (or shore or generator power so the charger can boost the voltage) so there is enough consistent voltage available to power those items properly.

I have a full wall slide (electric) and hydraulic leveling jacks. The coach came with two 6V batteries and I added two more for some boondocking once in a while. I would stick with the 6V golf cart batteries and you can down-grade to two and still be ok. The 6V golf cart batteries and deisgned for deep discharge and can last longer.

[creativepart]

Originally Posted by Cajun2Stepp

just wondering...why do I need four 6 volt house batteries to power up the coach?
I always run the generator while under way to power the a/c's and residential refrigerator, and NEVER dry camp.
Why couldn't I save $400.00 and just run a deep a single 12 volt deep cycle battery?
Thoughts?

Actually, you only have two 12v “batteries.” Each pair of 6v batteries is one 12v battery. Don’t think of it as 4-batteries think of it as two. I bet you’ll agree that for your motorhome that two house batteries is just about right.

You could save 100 pounds of weight and replace the 4-6v with 2-100 aH 12v batteries and probably have a similar size bank that meets all your needs.

[wolfe10]

Originally Posted by creativepart

You could save 100 pounds of weight and replace the 4-6v with 2-100 aH 12v batteries and probably have a similar size bank that meets all your needs.

While I agree that if not dry camping, battery capacity is not as critical, the math-- I don't understand:


Two 100 amp 12 VDC batteries= 200 amp-hrs.


Typical 6 VDC batteries are around 220 amp-hrs @6 VDC. SO, four of them in series/parallel= 440 amp-hrs @12 VDC.

[creativepart]

Originally Posted by wolfe10

While I agree that if not dry camping, battery capacity is not as critical, the math-- I don't understand:

Neither do I apparently. I knew that was the amperage for 4-6v batteries but lost site of the math along the way. 4-12v batteries would be needed obviously.

Oh well, it was early morning. Not my strong suit.

[wolfe10]

Originally Posted by creativepart

Neither do I apparently. I knew that was the amperage for 4-6v batteries but lost site of the math along the way. 4-12v batteries would be needed obviously.

Oh well, it was early morning. Not my strong suit.

No problem-- sometimes I even have to take my shoes off to count past 10.


Just didn't want to lead the OP astray.

[Persistent]

There is a rule of thumb. Connecting batteries in series increases (doubles) the voltage. Connecting batteries in parallel increases current capacity (doubles the amp hours).

Two six volt batteries in a series connection double the voltage to 12 volts but does not change the current capability.

Two twelve volt batteries in parallel double the current, but leave the voltage unchanged.

A pair of 6 volt batteries connected in series is the equivalent to a 12 volt battery. Two such pairs connected in parallel (4 batteries) behave the same a two 12 volt batteries in parallel. Voltage is unchanged. Current doubles.

There was a time when battery technology was more limited. Using 6 volt flooded cell for large capacity deep draw applications like RV house battery banks made good economic sense.

Battery designs have changed over the years. GEL and AGM lead acid batteries have come a long way. The economics of using higher priced AGM batteries now exceeds use of flooded cell batteries in most deep draw situation.

The reasons for using 6 volt flooded cells in RV's are no longer valid except in very short term situations. For instance, if you plan to sell your RV soon, installing lower priced flooded cell batteries can provide an initial cost savings.

AGM, GEL, and lithium 12 volt batteries work as good or better than their 6 volt versions.

For long term use in RV applications, overall cost will be lower for AGM's. Of course bargain prices for purchase can change the results of the analysis.

These same economic analysis apply to lithium batteries. Lithium cost less in the long term and initial prices are dropping fast. However, the pay back time for lithium has been in the neighborhood of 10 years. The initial cost has been high. This detours many buyers.

In all cases if you are installing AGM or Lithium batteries, 12 volt versions will work as well a 6 volt versions or better, and the installation configuration is simpler and understanding how they combine is easier.

I wish you good luck and happy trails ahead!

[ArtJoyce]

Originally Posted by ArtJoyce

If you have a propane fridge? I don't see why you need those batteries. One 12v deep cycle would be fine.

Just thought of one thing. If you go to one battery. I would be connected to shore power, or start the generator before opening or closing slides.

[wolfe10]

Originally Posted by ArtJoyce

Just thought of one thing. If you go to one battery. I would be connected to shore power, or start the generator before opening or closing slides.

Agreed, with smaller than OE battery bank, some source of charging is needed for high-amp loads.


That source could be shore power (powering your converter or inverter/charger).


It could be your generator doing the same.


It could be your engine running and the alternator helping with the load.