one deep cyle battery or 2?

[MtnDon]

It's a matter of several factors. How well you maintain them, how deeply you discharge, how many amp-hours you need to use before recharging(or watt hours if you think in those terms). IMO, two 6 volt golf cart / industrial batteries give you higher quality batteries than than what you get with the 12 volt RV/Marine type. But if you abuse them; let the fluid level get low, discharge very deeply and let them sit in partial charge for extended periods you will ruin any battery.

Start with how much power you need to have on board. If you are running AC devices through an inverter you may need the higher capacity of 2 batteries. If all you have are LED lights you likely only need a small 12 volt battery and have the added bonus of dragging around less weight.

It all starts with hpw much power you need. Only you can figure that.

[Shadow Catcher]

As long as everything else is equal it make no difference if they are two or one, 6V or 12V.
Marine "deep cycle" are a compromise between a true deep cycle and a starting battery, not a good choice.
I chose a single Lifeline 150AH AGM, because, it is in the tongue box does not have to be vented, I do not have to add water and has a low self discharge rate. It was however expensive.

[glenpinpat]

On the trailer I am presently building I will be running 2 - 12volt agms. This way if one fails the other one can still keep running things for a short period and in an extreme situation(offroad and away from service stations) if your TV's battery dies you could use one of the AGMs from the trailer in the vehicle.

[Esteban]

I'd favor mounting a solar collector to the roof instead of using two batteries. The price can be competitive. It facilitates boondocking when/where shore power is unavailable. It may save weight and or storage space too.

Grape Solar sells a 12 volt 160 watt panel that is 58" long and 26" wide which may fit on a five foot wide teardrop's roof. It's $229.99 from Home Depot. With one of these you can have power for a luxury like an ac/dc fridge/freezer, lights, a fantastic fan, outlets, and other electrical goodies.

If you need a shorter solar panel UL-Solar sells a 12 volt 125 watt panel that is 48.5" long and 26" wide. It costs $239.00 from ul-solar.

The physically smaller Grape Solar 12 volt 100 watt panel is 40.8" long and 20.7" wide. Home Depot sells one for $139.99. It should be able to fit on just about any teardrop trailer's roof.

There are many more choices for solar panels.

I like the glue-on solar panel mounts from Instapark Instapark® ZJ-34W Universal Drill-free Solar Panel Rooftop Mount, Color White They are kind of aerodynamic looking, do not need screws to penetrate the roof so there is less opportunity for a water leak, and if used with theft resistant bolts solar panels are unlikely to "walk away."

Amazon.com has two lower cost MPPT solar controllers: MPPT Tracer1210RN Solar Charge Controller Regulator 12/24V INPUT 10A for $72.00 or a MPPT Tracer 2210RN Solar Charge Controller Regulator 12/24V INPUT 20A for $135.00. MPPT controllers can harvest more power than PWM solar controllers. PWM controllers can cost as little as $22.00.

My bottom line point is that solar power is no longer too expensive to use on a teardrop trailer. It allows you to camp in comfort without shore power. Or the need for two batteries. IMHO.

[glenpinpat]

If you use solar you still need to store it in a battery. Solar panels collect energy but the batteries store it so you can use it when the sun goes down to run lights, radio and for me the fridge.

[Esteban]

If you use solar you still need to store it in a battery. Solar panels collect energy but the batteries store it so you can use it when the sun goes down to run lights, radio and for me the fridge.

I plan to use one 100 amp hour battery in the teardrop while using an ac/dc fridge freezer, LED lights, fan, dc outlets, etc. The fridge/freezer I intend to use will either be an ARB 37 or (more likely) a more affordable TruckFridge TF41 (made by indelB). They can run for days off the power stored in one 100AH battery. I intend to have a 30 amp shore power inlet, solar power on the roof, and a 7 wire plug to the tow vehicle so the teardrop's battery can be recharged when the tow and tear are on the road.

If I need more power stored in the battery, and am willing to pay for it, I could buy a 105, 125, or 150 AH battery instead. I don't anticipate a need to do so. Not only do they cost more. They weigh more.

To each our own solutions to our wants, needs, and budget.

[48Rob]

Steve,

You state you have a 100 Amp hour battery, and that is all you will need to run your fridge, and other powered items for a day (24 hrs).
If the battery is 100 Amp hour and you follow the 50% discharge theory, then you have only 50 Amp hours available.
I'm guessing at around 5 amps at 1/3 per hour for the fridge, if so that is 40 Amp hours in a day, not counting the other usage.

Is this how you calculated it?

Rob

[len19070]

Slow its not a difficult answer.

You impress me as a Camper. One who doesn't bring a DVR, Lap Top, TV, no Microwave, Electric Coffee maker, Electric Water heater, Toaster Oven or any of that Stuff.

Your a Camper, as am I.

I run a fan when needed, a few lights and thats it.

I've been out for 2 weeks with only a Group 27 Deep Cycle Battery....as have others.

With No problems.

Happy Trails

Len

[Redneck Teepee]

Slow I would stick with a 12 volt "True" deep cycle battery or even better since you are building to suit, would be 2-6 volt golf cart battery's in series.You'll get more out of them as far as amp hrs at a 50 to 70% discharge level. I just purchased a 12 volt true deep cycle group 24 last week for $109 plus tax.

[Woodbutcher]

Same here Slow, I have 1 deep cycle marine battery and that is it. I charge from the tow vehicle while on the move and can make it several days without a re charge. Most of my internal lighting is LED battery units. I get more then a full season with the batteries each year. I do have a converter for when I have shore power. But I too have been out for 2 weeks at a time without shore power and made it just fine.

[bobhenry]

I run a fan when needed, a few lights and thats it.

I've been out for 2 weeks with only a Group 27 Deep Cycle Battery....as have others.

With No problems.

Happy Trails

Len

Just an FYI the O2Kool fan draws 1/2 amp thats 6 watts at 12 volt. I have mine wired to a double pole double throw switch which can reverse the polarity. This make the fan run in reverse and acts as an exhaust fan as well. Of course the blade design is to move air forward so the exhaust mode is not as strong but still a decent breeze. If you combine this draw with a few 12 volt LED lights you have gobbs of power for the duration.

[dguff]

Two.

[Epbowen]

I put two series 31 deep cycles UNDER the tear, harder to get to but balances the weight better. I do run a tv/bluray and lights. I'm looking at a solar panel to add to the top, because ???

[martymcfly]

One thing to consider. Most 6v deep cycle batteries are the wet ones that are made by Johnson controls. They are marketed as Energizer and such. They weigh about 82 lbs each and cost about $80. If you need to charge one to balance the two, then you need a 6v charger. This set up is only as strong as your weakest battery. I think the Trojan batteries are a little better, but cost more.

[MtnDon]

If you need to charge one to balance the two, then you need a 6v charger.

IMO, not true as long as we are talking about using them in series to provide 12 volts, and as long as there are no 6 volt devices wired in to draw from only one of the 6 volt batteries.

A 6 cell 12 volt battery is nothing more, nothing less than the cells from two six volt batteries connected in series and in a common case.

Large well designed off grid battery banks commonly use strings of wet flooded cell 6 volt batteries to make up 24 and even 48 volts. There are also battery banks assembled from a series connected set of 2 volt cells; 12 cells = 24 volts. That would be my ideal system. None of these examples require a battery charger for less than the overall system voltage; 12, 24 or whatever it may be. Cells or batteries in series are superior to those in parallel. Parallel connected batteries is where inequalities in internal cell or battery resistance can cause problems with uneven charging and discharging. The cells all drain and charge together. There can be slight differences in cells in a healthy battery.

Our system uses some parallel strings of series connected batteries. I try to head off issues by doing an annual shuffle and periodic equalization charges. Equalizing is performed at the system voltage of 24. Five years on our golf cart batteries next month and all is still well. We've also run series connected and series - parallel connected golf cart batteries in RV's since the early 90's. Never needed a 6 volt charger for the RV as they are always used in series pairs.

If anyone wants to discuss further I'm up for it.