Which is the better battery configiration

Blaster Man wrote:
I tried two 12 volts, but that was not enough juice to run the inverter...the third one fixed that.

How large was the inverter?

What type of battery bank?

I tried two 12 volts, but that was not enough juice to run the inverter...the third one fixed that.

Blaster Man wrote:
Call it what you like, my three 12 volt AGMs do fine on an all electric 45' coach if you do very little dry camping...we do virtually none.

If you never dry camp, buy a single flooded 12v as cheap as you can (around $100) and it will do fine.

There saved you an extra 120lb and probably $500-800 over AGMs which make zero sense in an RV unless you are doing barrel rolls on a regular basis with it.

Now back to your thread talking about actual apples to apples comparisons....

^^^ I've been thinking about this - if you never do any dry camping wouldn't it make sense to buy the cheapest battery you could buy? You're not looking for quality, you're looking for something to take the voltage, and nothing else.

I do this at our hunting camp - I don't need a good battery, I just need something that will take a charge, it doesn't even need to hold it for more than a few minutes.

Call it what you like, my three 12 volt AGMs do fine on an all electric 45' coach if you do very little dry camping...we do virtually none.

Blaster Man wrote:
One often forgot about fact is that the 12v are very much lighter than the 6 volts. I went from 8 six volts to three 12 volts (all AGM) and my total weight went down a bit over 300 lbs.

12v AGM battery weighs ~63lbs (google)
6v GC battery weights ~60lbs (google)

Two 12v AGM batteries (~100AH + ~100AH = ~200AH) weigh ~126lbs
Two 6v GC batteries (~210-220AH) weigh ~120lbs

Eight 6v GC batteries provides ~840AHs capacity and weighs ~480lbs.
Three 12v AGM batteries provide ~300AHs capacity and weighs ~189lbs.
Yes, your weight dropped ~300lbs, but your battery bank capacity dropped ~540AHs. Your weight didn't go down because you switched from 6v batteries to 12v AGMs, it went down because you cut your battery bank capacity down ~540AHs (which is certainly the right thing to do if you don't need that much battery bank).

-Chris

It looks like the motorhome I may buy has 2 12volts in it now and they are 2 years old. I will keep an eye on them and when it comes time to replace them, I most likely will go for 6 volts.

One often forgot about fact is that the 12v are very much lighter than the 6 volts. I went from 8 six volts to three 12 volts (all AGM) and my total weight went down a bit over 300 lbs.

pianotuna wrote:
Properly set up is not possible unless you wish to buy a special purpose alternator. Or add a diode type device to the existing alternator.

The computer in the engine "looks" at the starter battery voltage. When the starter battery has recovered--charging is scaled back. Once that happens there is little or no charging of the house bank.

A dc to DC takes the incoming voltage and boosts it to an acceptable voltage for charging the house bank.

My dc to DC charger does a maximum of 20 amps. That works out to less than 5 amps per battery.

Because I have a larger than usual bank, I chose to set the output voltage of the dc to DC at 14.7 volts. Don't do this unless you have researched what the ideal charging voltage is for the house bank.

Except the house bank is connected to the starting bank when running, so the engine computer sees a lower voltage and keeps the amps up...not 100-200amps but if properly set up, it's still sending maybe 20 amps back which will largely negate the draw from the fridge.

If you want to fast charge, you need to upgrade the pathway to the house bank and make sure the alternator is one designed for continuous high output. Used to be quite popular with boats to upgrade to a 300amp alternator...now it would be simpler to add 400w of solar since most people drive during the day when the sun s out.

Properly set up is not possible unless you wish to buy a special purpose alternator. Or add a diode type device to the existing alternator.

The computer in the engine "looks" at the starter battery voltage. When the starter battery has recovered--charging is scaled back. Once that happens there is little or no charging of the house bank.

A dc to DC takes the incoming voltage and boosts it to an acceptable voltage for charging the house bank.

My dc to DC charger does a maximum of 20 amps. That works out to less than 5 amps per battery.

Because I have a larger than usual bank, I chose to set the output voltage of the dc to DC at 14.7 volts. Don't do this unless you have researched what the ideal charging voltage is for the house bank.