Are 3-12 Volt batteries better than 2- 6 Volt

[TimLoon]

In earlier thread, it was determined that my Dometic fridge cooling unit is probably blocked. Moving to a Hot Point 9.7 residential as dry camping is sporadic.
I have 2-6 volt golf cart batteries currently and will be installing a separate PSW for the fridge, most likely 1000 watt. Realize battery setup is not optimal even with 220 watts of solar but have on board generator and carry a Honda 2000 for some trips.
Here is the question. My battery box under the steps is set up to hold 3 batteries. Would there be any advantage to moving to 3-12 volt deep cycle?
I am not interested in Lithium type as camper is 21 years old and although in great shape, almost time to say goodbye.
Anyone with personal experience in setting up the residential fridge, I would welcome your additional insight.

[ViperJD]

If you have two 6volt batteries, with room for a third, then yes, I would switch to 3 12 volt batteries. If you can add two more batteries, the four 6v or four 12v would be better. Hope that helps.

[SJ-Chris]

Try it with what you have, and then you will know. Very little risk of ruining your vacation too, since you have an onboard generator to keep your batteries charged up if needed.


Your two 6V batteries probably have 220AH of total capacity. You can safely use 75-80% of that each cycle, so that's ~160-170AH of usable capacity. Your 220w solar might generate ~60-70AH worth of charge back into your system each day, if it is getting sunlight.



I don't know how many AHs your fridge will use up in a 24hr period. If it is 100AH then it means your solar is covering much of that and it's eating into your battery bank just 30-40AHs/day. So you would have plenty AHs left for lots of other "regular" camping things (ie. lights, fans, pumps, phone charging, TV, etc).


Try it out. Do a test and see if you can last 2-4 days. When it gets low, you will have your answer. Then just fire up the generator for a few hours and get things charging back up.


Note: Adding an inexpensive Battery Monitor would give you much better insight into exactly how much battery power you use/need.


Good luck!
Chris

[d23haynes57]

Do you not have an inverter now? Can you use that. Besides the solar, how are you charging the GC-2? As the fridge is in the kitchen and you touch it and other appliances and the sink, be sure the inverter you get is rated for an ac RV application and properly switches the ground- neutral for pass through and when it is the source.
Going from 2-GC 225 A/H to 3 12 volt, 100 A/H each will give a bit more capacity. Be sure to get a real deep cycle 12 volt. Most of the store brands are not. The GC-2s can be good for a theoretical 300 to 500 cycles. The 12 volters are in the 100 to 300 if lucky. As you dip below 50% SOC or do the full charge over 80% off gas finish charge, that counts as a cycle.
Since using solar you should give thought again to going Lithium. A single 300 A/H will simply work much better.

[SafariBen]

A 300AH Li will have the huge advantage of faster charging when you run the generator. Your current 6V's may work fine as explained, and charge fine with the solar. If you need the generator, run it early morning to put a faster charge in and then let the sun struggle through the day to keep up or a little better. Or run the generator when you have a big load, like cooking.



Three typical 12V will have more capacity than two 6V, but generally speaking, two 6V in series will be less trouble than three parallel 12V lead acid.

[TimLoon]

Thanks for the input.
Will try all of this out while still in the driveway.
Answers to some of the questions:
- Yes, I have a battery monitor, That is a must have for me
- When camping, solar usually keeps my batteries charged, Once and awhile, will start the on board generator to top them off. The only heavy draw is my wife's hair dryer each morning
- Current inverter is 3000 watts, not PSW or MSW. Really don't need that much pull so may just replace that with a 2000 Watt MSW since it is already wired in

[Persistent]

Originally Posted by TimLoon

Thanks for the input.
Will try all of this out while still in the driveway.
Answers to some of the questions:
- Yes, I have a battery monitor, That is a must have for me
- When camping, solar usually keeps my batteries charged, Once and awhile, will start the on board generator to top them off. The only heavy draw is my wife's hair dryer each morning
- Current inverter is 3000 watts, not PSW or MSW. Really don't need that much pull so may just replace that with a 2000 Watt MSW since it is already wired in

There is no point in replacing the inverter with a modified sine wave inverter. The MSW is obsolete technology. Definitely get pure sine wave technology.

Many people get an inverter just for the refrigerator. Size it to be a little higher capacity than the refer requires. Double check the surge power the inverter can provide to start the refrigerator motor. This prevents loss of power to the refer if some other appliance overloads or otherwise compromises the main inverter.

A small additional inverter can also power the refer when the main inverter is "OFF" to conserve battery power.

Some RV compressor type refrigerators have a built in inverter. They also tend to be very miserly about using 12 volt power. Better than typical residential refrigerators.

Depending on the refrigerator, an extra 100 amp hours of battery power should cover daily use.

[hamm2018]

Originally Posted by TimLoon

In earlier thread, it was determined that my Dometic fridge cooling unit is probably blocked. Moving to a Hot Point 9.7 residential as dry camping is sporadic.
I have 2-6 volt golf cart batteries currently and will be installing a separate PSW for the fridge, most likely 1000 watt. Realize battery setup is not optimal even with 220 watts of solar but have on board generator and carry a Honda 2000 for some trips.

If installing a dedicated inverter for the fridge, I would also install a dedicated transfer switch for the fridge. Use a transfer switch like this: https://www.amazon.com/AC120V-15Amp-...34&sr=8-6&th=1

With this, find the power line for the outlet to the fridge from the breaker box, add the transfer switch in line next to the inverter.

[TimLoon]

Hamm,
I appreciate the suggestion however it may not work for my set up. When I installed the current inverter 10 years ago, I simply ran an extension cord (10 Gauge) back to my power plug. When we leave for trip and do not expect to have power, I simply plug the camper into the inverter and turn it on when needed. I turn on the breakers for the items we want to run and the inverter can support.
My concern is that if I have the automatic switch as suggested and I turn on the non-PSW inverter, it will then be feeding the PSW invertor indirectly.

[Stircrazy1]

Originally Posted by TimLoon

In earlier thread, it was determined that my Dometic fridge cooling unit is probably blocked. Moving to a Hot Point 9.7 residential as dry camping is sporadic.
I have 2-6 volt golf cart batteries currently and will be installing a separate PSW for the fridge, most likely 1000 watt. Realize battery setup is not optimal even with 220 watts of solar but have on board generator and carry a Honda 2000 for some trips.
Here is the question. My battery box under the steps is set up to hold 3 batteries. Would there be any advantage to moving to 3-12 volt deep cycle?
I am not interested in Lithium type as camper is 21 years old and although in great shape, almost time to say goodbye.
Anyone with personal experience in setting up the residential fridge, I would welcome your additional insight.

no one can tell you really with out knowing exactly which batteries you are thinking of.

are the 12V batteries the "deep cycle 12V" like the one you get from the rv dealer when you buy the rv, or are they "true" deep cycle 12V batteries, or are they marine starting deep cycle batteries. each one of these will have a different answer to your question.

to complicate things even more there are many different grades of 6V golf cart batteries, which brand / model do you have as this is going to effect the answer also.

a few people have suggested going LiFePO4, I am in that camp also, but you have to decide on your inverter first and then hunt for the LiFePO4 batteries that will have enough amprage output to power it. not hard to do but somthing to keep in mind, I don't think any single battery will power a 3000 watt inverter but two 300Ah batteries would and give you a ton of capacity. also if you are buying a inverter anyways look at a inverter / charger that is Li compatable.

finaly I know your reason for not wanting to go Li is the age of the rv, but to me that isn't a factor unless its your age that is saying this will be your last rv. if you get Li batteries and a inverter/charger you can always move them to your next rv.

[d23haynes57]

Originally Posted by hamm2018

If installing a dedicated inverter for the fridge, I would also install a dedicated transfer switch for the fridge. Use a transfer switch like this: https://www.amazon.com/AC120V-15Amp-...34&sr=8-6&th=1

With this, find the power line for the outlet to the fridge from the breaker box, add the transfer switch in line next to the inverter.

Note the operation of the ground conductor. Should not be used in an RV.
Use an inverter with a proper transfer switch built in and use the bypass.

"Safe DPDT circuit switch design (Double Pole Double Throw). Live and Neutral wire are switched at the same time. The Ground wires of the two inputs and output are connected together internally and will not follow the switch on and off."

[TimLoon]

The simple answer to "last" RV is that after 45+ married years of camping and RV'ing, we have become dismayed with it here in the Northeast. Finding it much easier to simply go Air BnB. We are slowly getting to the point of letting this go.
Now back to the fridge.
I have 2 "MidState" brand 6V batteries that have served us well for the last 3 years. Hardly ever use the generator when dry camping thanks to the little bit of solar. The genny has 125 hours mostly from exercising it.
Trying to keep this conversion as simple and cheap as I can. We only have two dry camping trips this year at 3 days each so I think I can stretch through them.
I decided not to put in an inverter with a bypass. Going to put in a simple 2 way switch that will allow me to switch over the hot leg only when on either shore power or invertor power. That would mean that the neutrals would be connected between the inverter and shore power. If someone smarter than me can tell if that would be a bad move, please let me know as this is not my strong point.

[d23haynes57]

Originally Posted by TimLoon

The simple answer to "last" RV is that after 45+ married years of camping and RV'ing, we have become dismayed with it here in the Northeast. Finding it much easier to simply go Air BnB. We are slowly getting to the point of letting this go.
Now back to the fridge.
I have 2 "MidState" brand 6V batteries that have served us well for the last 3 years. Hardly ever use the generator when dry camping thanks to the little bit of solar. The genny has 125 hours mostly from exercising it.
Trying to keep this conversion as simple and cheap as I can. We only have two dry camping trips this year at 3 days each so I think I can stretch through them.
I decided not to put in an inverter with a bypass. Going to put in a simple 2 way switch that will allow me to switch over the hot leg only when on either shore power or invertor power. That would mean that the neutrals would be connected between the inverter and shore power. If someone smarter than me can tell if that would be a bad move, please let me know as this is not my strong point.

It is an extremely bad move. When that inverter is supplying power the neutral and ground has to be bonded. That bond also needs to be disconnected when connected to an outside power source. If using generator, the neutral-ground bond is in the generator and switched by the transfer relay. Particular car needs to be taken for the refrigerator as it since it is in the kitchen and you could touch it and some other grounded appliance, or the sink bad things can happen. Do it right.

[TimLoon]

Appreciate the advice.
That's why I asked.