12v or switch to 6v? Still not sure

[glarior]

I have installed two deep cycle 122ah 12v batteries last month to replace the pathetic stock battery that came in the aframe. On my last camping trip my batteries depleted slowly over 4 days. I used a 140w panel which is not enough to charge the batteries. I decided to make two changes... first, have 3 portable 140w solar panels. Second, install more batteries.

My dilemma is price for batteries. From what I have read 6v Trojan batteries are the way to go. I found one that does 300 something amp hours but expensive ($300+ each). Now, either I add two more 12v deep cycle 122ah batteries for ~$180 or I switch now and buy 6v batteries that will have similar or more amp hours.

My current draw is not much except the fridge can draw 8amps when not on propane. I always draw .05amps at idle. I run a blender, water pump, tv, and charging items (cell, laptop, camera batteries). During winter I will use the propane furnace off and on which draws ~2 amps (still need to verify that number). I want to least last a week with no shore power.

Does my purpose justify the cost to switch or stick with 12v? Save the money, add two more 12v batteries and switch later on? Do nothing?

[Bluepill]

Since your 12 volt batteries are new, now is the time to add extras if you are going to.


Question: Why would you choose to run 12 volts on reefer rather than propane?

Info: Actual draws:

I just received a random email bump from the forum, and as it turns out I have some valuable info to share. I just spent the morning with a Fluke Multi Meter attached to my Surveyor sport, have taken these load readings.

For my base line I had to pull both 40 Amp fuses on the DC side of my converter to get Zero Load. The Converter has a 0.011 amp load with no other loads. I disconnected all other loads, and found there values by reconnecting them One-at-a-time...............

Nat Gas detector (hot all the time)......... 0.07 amps dc
Radio (hot all the time) off at idle........... 0.03 amps
Radio on FM at half volume................... 0.42 amps
Water heater calling on propane..............0.7 amps
Frig calling on Propane..........................0.81 amps
Fantastic fan on low..............................0.93 amps
'' '' med.............................1.22 amps
'' '' Hi................................1.54 amps
Water pump on, but satisfied..................0.025 amps
Water pump calling...............................3.0 amps
Furnace fan only...................................2.8 amps
Furnace calling ....................................3.3 amps
One incandescent bulb in my outside lite...1.56 amps (that's one bulb!)
dbl head overhead inside lite...................3.20 amps
I have LED lamps in my interior fixtures now, and
each lamp draws only ...........................0.20 amps


Have you considered a small generator to recharge the batteries?

[johnbryanpeters]

My Suburban NT20SEQ furnace is specified at 2.7 Amperes.

[glarior]

I do not want to run propane while driving so I use DC. The truck wasn't supplying enough power to charge the batteries while driving. That is another action item on my list to resolve.

Those numbers are similar to what I was showing on my setup and very informative.

I plan to purchase the 3000w Honda generator once my old generator dies. The old one is so loud you can barely hear the TV. Plus, most places I camp at do not allow generators.

Originally Posted by Bluepill

Since your 12 volt batteries are new, now is the time to add extras if you are going to.


Question: Why would you choose to run 12 volts on reefer rather than propane?

Info: Actual draws:

I just received a random email bump from the forum, and as it turns out I have some valuable info to share. I just spent the morning with a Fluke Multi Meter attached to my Surveyor sport, have taken these load readings.

For my base line I had to pull both 40 Amp fuses on the DC side of my converter to get Zero Load. The Converter has a 0.011 amp load with no other loads. I disconnected all other loads, and found there values by reconnecting them One-at-a-time...............

Nat Gas detector (hot all the time)......... 0.07 amps dc
Radio (hot all the time) off at idle........... 0.03 amps
Radio on FM at half volume................... 0.42 amps
Water heater calling on propane..............0.7 amps
Frig calling on Propane..........................0.81 amps
Fantastic fan on low..............................0.93 amps
'' '' med.............................1.22 amps
'' '' Hi................................1.54 amps
Water pump on, but satisfied..................0.025 amps
Water pump calling...............................3.0 amps
Furnace fan only...................................2.8 amps
Furnace calling ....................................3.3 amps
One incandescent bulb in my outside lite...1.56 amps (that's one bulb!)
dbl head overhead inside lite...................3.20 amps
I have LED lamps in my interior fixtures now, and
each lamp draws only ...........................0.20 amps


Have you considered a small generator to recharge the batteries?

[mikakuja]

Just out of curiosity, why do you choose to run on DC instead of propane while driving? We are the exact opposite mindset and always run on propane.

Have you considered wiring your vehicle with a dedicated charging system for the RV batteries? Basically not much more than HD wiring direct from the vehicles alternator to the RV batteries with it's own plug at the bumper. This would enable you to supply enough power to make up for what the fridge uses while traveling. You will never get enough power through the factory wiring at the trailer plug.

As for your batteries, I personally prefer the 6v route but you already have two new 12's. Why not just add two more if you have the room, that alone will double your amp hours.

We purchased a Champion 3100w inverter gen for when the solar panels don't supply enough power and couldn't be happier with it, very quiet for it's size, and runs everything in our RV... Champion makes a decent product worth considering IMO...

[hbillsmith]

Originally Posted by Bluepill

I just spent the morning with a Fluke Multi Meter attached to my Surveyor sport, have taken these load readings...

Nice real life numbers that I can use. Now I just need a similar report for the current generation LED TV's. I've run my FURRION 39" and 32" off of a modified sine wave inverter and was surprised at how fast they drew down my old 12v deep cycle battery. The only thing on the little cheap Harbor Freight ($25 I think) was a single TV. I've since swapped out the 12v Deep Cycle for a Group 31 AGM that's rated for 90 amp hours (I'm adding a second one soon as I can find a vented battery box that will hold 2 Grp31's that doesn't cost over $100).

When I was watching the 39" I had a Kill-A-Watt meter between the TV and the Inverter and I thought I would last 10 hours, nope only made it about 2.

[Jamnut]

hbillsmith, the current draw you want to measure is Inverter Input current from the battery. That will account for inverter efficiency.

Glarior, I have similar battery capacity with 2 6v Trojan T105 batts in series. With 2 fixed 165w and 1 portable 165 watt PV panels. I have no problem going 4 days camped under trees, but it's hard to compare our loads. Since you already have the 12v batts, I agree with the others to just add more of the same. You could add one at a time, just continue to parallel them. Remember you can only use about 50% of your rated capacity.

[glarior]

Originally Posted by mikakuja

Just out of curiosity, why do you choose to run on DC instead of propane while driving?

Have you considered wiring your vehicle with a dedicated charging system for the RV batteries?

As for your batteries, I personally prefer the 6v route but you already have two new 12's. Why not just add two more if you have the room, that alone will double your amp hours.

1.) Just a preference. I always lean to that what if scenario. I have no proof of one way or the other is better.

2.) Yes, I have that on the list of things to do. Its way down on the bottom of the list at the moment lol.

3.) Seems like that is the better choice. When they all go bad I can upgrade to 6v.

Originally Posted by hbillsmith

Nice real life numbers that I can use. Now I just need a similar report for the current generation LED TV's. I've run my FURRION 39" and 32" off of a modified sine wave inverter and was surprised at how fast they drew down my old 12v deep cycle battery. The only thing on the little cheap Harbor Freight ($25 I think) was a single TV. I've since swapped out the 12v Deep Cycle for a Group 31 AGM that's rated for 90 amp hours (I'm adding a second one soon as I can find a vented battery box that will hold 2 Grp31's that doesn't cost over $100).

When I was watching the 39" I had a Kill-A-Watt meter between the TV and the Inverter and I thought I would last 10 hours, nope only made it about 2.

Hrmm, I have a 32" Samsung LED TV I use off a 2000w pure sine inverter. I have not checked to see the power it draws. In theory my monitoring system should be able to show the current, amps used and watts used. I should test it. If I have time this weekend and remember too.... I will test the LED TV for you.

Good luck on finding a box. Why use one box? What is wrong with having two boxes? I use group 29 batteries and two boxes. They were $10 a piece.

[glarior]

Originally Posted by Jamnut

Glarior, I have similar battery capacity with 2 6v Trojan T105 batts in series. With 2 fixed 165w and 1 portable 165 watt PV panels. I have no problem going 4 days camped under trees, but it's hard to compare our loads. Since you already have the 12v batts, I agree with the others to just add more of the same. You could add one at a time, just continue to parallel them. Remember you can only use about 50% of your rated capacity.

That 50% capacity through me for a loop first time I discovered it. All my calculations were based on 100%... pesky real life scenarios lol.

I am leaning towards just adding more 12v batteries.

[larryandamy]

I agree that you should stay with 12V since you have 2 new batteries.
I did a lot of research and once you get past the "opinions" and look at the facts... The only advantage of the 6V batteries is that they will last longer since they do have larger plates in them. Not sure how much longer because use and charging varies... but could be as much as twice as long.

But the main disadvantage of a 6V is that you have to have two 6v batteries in series. So if a cell goes bad in one battery, then you have 0 volts output.
With two 12V in parallel you would still have 12V if a cell on one of the batteries.

I won't pay $300 for battery... I buy them at Costco for $75 and I don't mind checking the fluid level in them twice a year. Yeah, they will only last about 2 to 3 years, but I can buy 4 of them versus one $300 battery that could last 5 to 6 years. The same $300 gets me 8 to 12 years.
But if you don't like maintaining your rig yourself, like I do... Then the $300 batteries might be better for you. I am 60 and I love working on my rig now.
As I get older, I am sure this will change.

For solar I have 2 100W fixed panels to charge 3 12V RV/Marine deep cycle batteries. And in 6 weeks in Alaska, I never had to worry about battery power. Of course daylight was over 22 hours a day...
I was going to add another 100W portable panel, but never needed it.
I am convinced that fixed panels running 7X24 (well not at night...) are better than portable that only run when you set them up. I did it both fixed and portable and the advantage of charging the whole time I am driving provided higher battery levels and trumped the advantage of not having the fixed panels in direct sunlight all the time.

I always run the fridge on gas and never had an issue. Yeah... I know some say to never drive with fridge on gas... But that is just to cover their *****.
Just like they say to check your tire lugs before each drive... Just CYA...

[grumpyoldman]

Originally Posted by larryandamy

I agree that you should stay with 12V since you have 2 new batteries.
I did a lot of research and once you get past the "opinions" and look at the facts... The only advantage of the 6V batteries is that they will last longer since they do have larger plates in them. Not sure how much longer because use and charging varies... but could be as much as twice as long.

But the main disadvantage of a 6V is that you have to have two 6v batteries in series. So if a cell goes bad in one battery, then you have 0 volts output.
With two 12V in parallel you would still have 12V if a cell on one of the batteries.

I won't pay $300 for battery... I buy them at Costco for $75 and I don't mind checking the fluid level in them twice a year. Yeah, they will only last about 2 to 3 years, but I can buy 4 of them versus one $300 battery that could last 5 to 6 years. The same $300 gets me 8 to 12 years.
But if you don't like maintaining your rig yourself, like I do... Then the $300 batteries might be better for you. I am 60 and I love working on my rig now.
As I get older, I am sure this will change.

For solar I have 2 100W fixed panels to charge 3 12V RV/Marine deep cycle batteries. And in 6 weeks in Alaska, I never had to worry about battery power. Of course daylight was over 22 hours a day...
I was going to add another 100W portable panel, but never needed it.
I am convinced that fixed panels running 7X24 (well not at night...) are better than portable that only run when you set them up. I did it both fixed and portable and the advantage of charging the whole time I am driving provided higher battery levels and trumped the advantage of not having the fixed panels in direct sunlight all the time.

I always run the fridge on gas and never had an issue. Yeah... I know some say to never drive with fridge on gas... But that is just to cover their *****.
Just like they say to check your tire lugs before each drive... Just CYA...

X2 on the highlighted paragraph.
I have 4 12 volt AGM batteries in parallel. If one goes bad I would just disconnect it and still have 12 volts.

[bclemens]

I will 2nd what was posted here on 12V vs 6v as it is something we looked at as a company. I talked in depth to the battery mfg.

I was thinking we could get more amp hours out of 6V but that is not the case. A 195ah rated 6V battery...is at 6 volts. Put 2 together in parallel and you have 390ah at 6v...or more importantly only 195ah at 12V.

What we run in our motorhomes is (2) 12V AGM batteries that are 105ah each for a total of 210ah at 12v.

The primary issue is that many mfg's will use a "hybrid" 12V battery. So it is a starting battery and deep cycle battery. Frankly to save cost, lighter plates, etc. They go bad and people suggest 6V because they only come in deep cycle. So someone will do that and low and behold they are much better!...but that's not the whole story.

Our battery rep said if it was his coach he would want (2) 12V AGM's. One, they are much easier to find. 2. As mentioned, if a cell goes bad, they will still operate. If they are true deep cycle, then they will last just about as long.

The only real advantage to the 6V is that you always know it is deep cycle. Because the plates are then heavier (fewer of them) they do tend to last longer if properly maintained (but at a higher price of course). So if a normal battery lasts 3-4 years, a 6v might last 4-5 years.

Pros and cons to both of course, but seems to be more pros on the 12v side.

[Less is More]

Talked to a couple that mounted a 100 W panel to the roof and have 2 12 volt batteries and they stated that they never have a problem with the batteries running low. They also said they stopped using their generator because the direct DC is not multi-state and does not properly charge a deep cycle battery and they object to the noise even though its a Honda inverter generator.

What is critical is that the panel charge continually during daylight hours. I did not ask them what type of equipment they were running, but I suspect that they were serious campers/outdoors people and did not use a lot of entertainment equipment.

[glarior]

I never thought of the what if a 6v battery goes bad! Very good point. I called around for pricing and its almost double the cost to do a 6v setup vs the 12v. I will add the 12v batteries and save the money. It will work great for my setup.

I want to mount one or two of the panels... have not figure out how to mount them to the A-frame yet.

[pgandw]

I started with 2 12V batteries. One went bad and severely discharged the other before I even realized what had happened.

In pricing replacements, I found 6V golf cart batteries were cheaper and had more capacity than 2 12V that would fit in my battery box. I bought. 2 Interstate 6V batteries at Costco for $150 including tax.

Just my experiences, yours may differ
Fred W
2014 Rockwood A122 a-frame

[325BH]

Around here, T105's run about $130 after tax. Their durability is well known vs 12 volt batteries.

[metalsideup]

I've read all the replies so far, but what hasn't been addressed yet, to me the most important consideration, is starting a thorough evaluation of your recharging system. Too many think they've "gone solar" only to be disappointed and then assume the fix is to buy more panels and batteries wherein the real issue is poor design using tiny cabling, poor connections, and junk controllers. If you want to improve your situation, begin researching your solar system and bring it up to top specs. You might be surprised at how some changes can save you lots of battery money, not to mention the additional weight of the extras. Adding a good battery monitoring device like a Trimetric can go a long way in determining what is a power hog or letting you know when something is amiss within your system. Double checking your basic circuitry for starters costs a whopping Zero.

[camaraderie]

I think the best approach for a system that will keep the OP out for a week using solar and batteries needs to be based on his actual amp hours use daily...which is apparently an unknown. The way to fix that and something you NEED anyway if you are gonna be running full time on batteries is a TRUE BATTERY MONITOR...like the Trimetric or Victron which cost around $150 bucks and are easily installable in an hour or so and you can just go out for a weekend with your existing system and take a reading (from your full existing batteries) of how many amp hours you use in 24 hours. Lets say you use one hundred a day as an example. This means that you need to recharge your batteries 100amphours per day to keep them falling below 50% (assuming the 200 amp hours you have now.NO...you don't really have 122 amp hours in your batteries...there is no such deep cycle battery. It is a marketing dept claim!)
So... the solution is EITHER add 400watts of solar panels to provide 100amp hours a day (in sunny weather). 4 watts per amp hour needed is a good average to use.
OR add battery capacity to give you more time before charging is needed.
Obviously this latter can get expensive...so figure out how much wattage you CAN provide with panels on your particular rig...divide by 4 and know that is the max you can count on being supplied daily. The rest of your goal will need to be met by adding twice the battery capacity as amp hours you still need to follow the 50% discharge rule.
I agree you should keep your 12V deep cycle batteries. But based on the amp hour rating...I'm wondering if they really are deep cycles and not dual purpose. Have you got a brand, model and size I can take a look at?
All best of luck with this!

[pmsherman]

Wiring two 12V batteries in parallel has lots of problems which are totally ignored by all RV manufacturers. I've held a number of discussions about batteries with my neighbor who used to design electrical systems for aircraft; systems with multiple power sources and a mandated requirement to function on battery power when all of the sources fail. He's forgotten more about battery and power systems than most of us will ever learn.

1. If one cell of a battery shorts, all batteries wired in parallel with it will drain their power into the battery with the short. You'll need to unhook all of the batteries and charge them individually to locate the one with the bad cell. If you don't discover that a cell shorted for over 12 hours, it's likely that you will have damaged the other batteries.

2. You can't replace one of a pair of batteries without causing problems. A new and an old battery will have slightly different charge/discharge characteristics that effect the ability to fully charge the batteries and the amount of power you can draw from them.

3. Batteries with slightly different internal characteristics, when wired in parallel, have a parasitic relationship where the battery with a slightly higher charge discharges into the one with the lower charge. They also accept charge at different rates which means that one will always reach full charge before the other.

4. Wiring multiple 12V batteries in parallel needs to be done very carefully to equalize the load and charge rate to the batteries. My Georgetown's two 12V batteries, as wired from the factory, are NOT wired properly to equalize the load on them and I doubt that FR ever considers this when building a rig. I have an off-grid remote solar/wind/battery powered building and the commercial battery system that powers the building was, as designed by the manufacturer, not wired properly to equalize battery loads and charging. Correctly wiring the batteries added at least 20% to the system's capacity. (Note: this is a lot larger than a two battery system.)

Golf cart batteries use solid lead plates which are much sturdier than the coarse grid hybrid 12V wet cell batteries that are usually installed in a rig. The downside of them is that they are very poorly suited to provide 200+A for a starter motor. One upside is that the 50% rule is usually more like 80% for them. A 12V hybrid battery's reserve capacity is measured with a 25A load on the battery while golf cart batteries are measured with a 75A load. For those of you who play golf using electric carts, how often have you seen a golf cart stranded with dead batteries?

A lot of this decision boils down to what you need for your individual use of the rig. Would you rather have two 12V batteries giving you 160-180AH of battery capacity or two 6V batteries in series giving you 220AH? The cost of the batteries is almost identical. The weight is similar and the 6V batteries need less interconnect wiring. The remote fill systems to keep the water level correct for a pair of 6V batteries is also significantly less expensive than one for two 12V batteries. I don't know where your batteries are located but in my Georgetown, you either need to be less than 4' tall, over 9' tall, or an accomplished contortionist to be able to check the fluid level in the house batteries.

My two 12V house batteries are pretty much shot now, being 4.5 years old. I'm replacing them with two 6V golf cart ones before the next trip.

Phil

[glarior]

Woah, y'all jus took this discussion to the next level.

Locally bought the trojan t145 are 214 each. Has 260ah per mfg website.

My exact amps used per trip is unknown. Each trip has had its own variables and ive not made a average number.

For my battery install I can install them anywhere I want. Im not afriad of chopping up the camper and rewiring. Currently i have two batteries on the tounge and if i installed more they will be in the front cubby hole on a slide out setup.

My wiring wiring connections are soldered. Wiring length from panels to controller is 4ft. I do not know exact guage of the solar panel wires. The controller is one item ive planned to possibly upgrade with the additional solar panel. Thats on the to do list

Ill get the battery information tomorrow.

Interesting point of a short in one of the batteries.

Another good point if i replaced a battery.

Why do 6v not have the issue with a new battery being replaced in the series? Or do they have the same issue?

What do you mean wired properly in parallel?