6 or 12 volt batteries on towed unit

[WI_Jeff]

First of all, let me introduce myself. I'm Jeff from NW Wisconsin and West Central Georgia.Yep, a snowbird. I make at least 2 trips per year and camp on and off the rest of the year. I "tented" until I got old enough to need a little comfort. Owned 3 different "campers" in the past several years from a 1967 converted Chevy school bus to a class A Winnebago (for sale). I now have a 2006 Roadmaster Toy Hauler. I am in the process of upgrading to my needs. Now to the "meat" of this post.

This topic has probably been talked to death, but I really cannot find an answer. I have installed a 3000 watt (6000 peak) inverter and a power transfer switch. I have on order 400 watts of solar power and a WindyNation P30L Charge Controller. I have moved the batteries to the inside storage and I have room for four (4) batteries.

I need some insight, pros and cons and input on should I have four 12 volt deep cycle batteries in parallel or four 6 volt batteries in a combination of series and parallel to produce 12 volts?

[WI_Jeff]

Well, what I decided is 12 volt batteries. Got everything going... almost. I have to put the finishing touches on a little bit of stuff. If I can ever figure put how to attach a PDF, I will post my wiring diagram for the batteries and solar power. I want to thank you all for your help.

[pianotuna]

Is this the battery you wish to use?



There is an approximate way to get amp-hours from reserve capacity.

In this case, it works out to about 85 amp-hours. But since only 20% should be used, from a Marine "deep cycle", that means only 17 amp-hours capacity per battery. With 4 wired in a balanced manner that suggests a total usable capacity of only 68 amp-hour.

To put this in perspective, my coffee maker uses about 6 amp-hours to brew one pot. The fridge, with a 2:3 duty cycle, running on 120 volts would consume about 21 amp-hours in one hour.

I'm not saying you can't use Marine jars. I did that successfully for over 9 years. But I had 875 amp-hours of batteries in two banks and a modest solar charging system to maintain them.

[pianotuna]

Jeff,

It is a bit unusual for deep cycle batteries to have cold cranking amps listed. Is there at least a reserve capacity number? Marine jars do list CCA but depth of discharge is best kept to only 20%. "Real" deep cycle can do 50%.

Please explain what #2 battery cable is. (diameter?)

00 wire has an outside diameter of stranded copper at 0.450 inches and it may be too thin for a 3000 watt inverter.

[WI_Jeff]

AS for "Do mean #2 or do you mean 00?". I used #2 Battery cable. (The inverter came with #8 wire to use.) As for the batteries, they say on them that they are "deep cycle" and the description sure "implies" that they are. They also have batteries tat are labeled as starting and deep cycle/starting. I know you can't believe everything you read but, I hope if a national company states that their product is a "deep cycle" it is.

[pianotuna]

Do mean #2 or do you mean 00?

#2 at 280 amps makes a pretty good fuse.

Even 00 is on the light side for a 3000 watt inverter.

WI_Jeff wrote:
I used #2 wire and the longest run is about 40 inches.

[wanderingbob]

Just curious , what will you be running that will require 3,000 watts ?

[BarneyS]

This ^^^^^

It has always been my understanding that if a battery had CCA ratings then it was a starting battery and not a "deep cycle". I think that stands for "Cold Cranking Amps" which you wouldn't have on a deep cycle battery since they are not designed for starting use.

I also believe that the deep cycle type batteries have thicker and heavier lead plates and are designed to give out lower levels of electricity over a long period of time and can be discharged lower than the starting batteries. I think the starting batteries have more plates which are thinner and are designed to give out bursts of high energy for short periods of time but will probably have a shorter life due to the thinner lead plates and cannot be discharged as far before damaging the battery.

This is just my understanding of how things work in the battery world. I am not an engineer or electrical wizard so please take my words with a grain of salt. :B
Barney

[pianotuna]

What makes you believe they are deep cycle batteries? Nothing in your post suggests they are.

WI_Jeff wrote:
I'm still learning. I'm getting coupons for 20 to 25 percent off on AutoCraft batteries. They have a few that seem to be "true" deep cycle batteries. They are showing from 550 to 675 CCA and a price from $75 each to $88 each. I cannot find the hour rating. If I get 4 (four) batteries, that is not a bad price. I am a little worried about these being "wet" cell batteries and not AGM type. Thoughts? Ideas? Suggestions?

[WI_Jeff]

I'm still learning. I'm getting coupons for 20 to 25 percent off on AutoCraft batteries. They have a few that seem to be "true" deep cycle batteries. They are showing from 550 to 675 CCA and a price from $75 each to $88 each. I cannot find the hour rating. If I get 4 (four) batteries, that is not a bad price. I am a little worried about these being "wet" cell batteries and not AGM type. Thoughts? Ideas? Suggestions?

[DrewE]

35 Ah is a tiny battery, think riding lawn mower or maybe motorcycle size.

[WI_Jeff]

Harbor Freight Battery???? Has anyone ever tried the Harbor Freight "Thunderbolt Magnum Solar 12 Volt, 35 Amp Hour Sealed Lead Acid Battery" (Item # 64102). The specs are right with the VMAXTANKS VMAX V35-857 battery (one of the rvweb;s top 10). Price is great at $70 (56 bucks with the coupon) compared to $109. I know Harbor Freight does not make there own batteries. I checked around and cannot find out who manufactures HF batteries. It is almost worth trying 4 of these batteries just because of the price.

[WI_Jeff]

MORE INFO: The inverter is a "3000 Watt Reliable Pure Sine Wave Power Inverter". I used #2 wire and the longest run is about 40 inches. I will be storing the batteries in the pass-through storage (under the bed)) inside Rubbermaid storage bins with 8 (eight) 2 inch air holes. Reading through your posts I am leaning toward using 4 (four) Interstate (model DCM0035) AGM Deep Cycle Batteries or 4 (four) of the Odyssey PC680 Batteries and running them parallel. I am kind of stuck with 12 volt. THANKS AGAIN for any advice and input. Any other ideas let me know. I am always willing to learn.

[theoldwizard1]

IMHO, TRUE 12V deep discharge batteries are almost a scarce as hen's teeth ! Most are "dual purpose" marine batteries which are basically starting batteries with a different label. (TRUE 12V deep cycle battery - Trojan T-1275 Also available in AGM.)


I would go with the four 6V golf cart batteries. Likely to cost less and last longer. AGM batteries raise the cost a lot. If your compartment has ventilation to the outside and is reasonably well sealed from the interior I think you are okay.

[pianotuna]

2oldman raises a good point. High wattage inverters mated to 48 volts is a better "fix".

If I were able to start over I'd definitely jump to 48 volts.

Alas it is, for me, a case of champagne tastes but a beer budget.