maximizing battery capacity

[nuckfan]

I have an 8 foot camper with a 100 watt solar panel and charger. Right now I have a group 24 12v battery and would like to increase the amp hr capacity, I was wanting to run two 6v in parallel but I cannot due to the size of the battery box being too small. the opening on it is 14.5" wide by 20" tall and 9" deep. What I would like to know is what type of battery can maximize the amount of amp hours given the limitations I need to deal with.I have looked at Interstate batteries but cannot find one that is not rated in cold cranking amps, as I was informed that this would not be an ideal application for a solar setup.

[Almot]

Lithiums and AGM are 2 different things.

If you can squeeze 2 AGM on its side for a total 200-220 AH, with moderate energy use and 200W solar you'll be OK. Can present technical difficulties though. The battery sides are not always perfectly flat.

Don't cheap out on AGM, get some reputable brand. Lifeline may not be the best choice for the reasons that people noted. Deka is a decent brand too, and costs less.

[nuckfan]

I have to say for myself anyway I find it a bit overwhelming how much there is to learn about an rv electrical system when solar is involved. Thank you Almot for dumbing it down for me a bit. I now have a better understanding and see that I do have some options for more battery capacity given the limitations of room I need to endure. The Torklift battery cradle thing is an idea but might be a hinderance when going off-road. I like the idea of AGM because the can be mounted on their side making the best use of space in my battery house. Too bad lithium batteries cost so much. Ton of amp hours in a smaller lighter package but cha-ching$$$

[pnichols]

The common 12 volt battery group sizes do differ in physical size and capacity.

For instance, here's a Group 27 deep cycle 12 volt battery:

http://www.fullriverbattery.com/product/batteries/DC105-12

And here's a Group 31 deep cycle 12 volt battery of the same series by the same manufacturer. Note that it has larger physical dimensions and greater capacity:

http://www.fullriverbattery.com/product/batteries/DC115-12

Both of the above two diffferent group size batteries have the same type of terminals.

[MEXICOWANDERER]

29, 30, 31

Same battery, different posts.

[SkiSmuggs]

When I upgraded my Grp 24 to a Costco Grp 27 Marine/RV battery, I went from 75AH to 115AH. And I think there are Grp 29 and 31 above that.

[pnichols]

Notice in MEXICOWANDERER'S post that he mentioned absorbed glass mat (AGM) batteries.

These batteries are "dry", in that there is no liquid in them. They do not have to be mounted upright. They can be mounted so as to lay on their sides.

The dimensions that you provided for your battery storage area should easily handle two deep cycle 6 volt AGM batteries (hooked up in series with each other), or two deep cycle 12 volt AGM batteries (hooked up in parallel with each other) - with the two batteries laying on their sides. You always want "deep cycle" type batteries in your RV. Either of these two setups should provide you with a total of 220 amp hours to 250 amp hours of RV battery capacity.

Interstate does offer 12 volt deep cycle AGM batteries, as do many other suppliers. I had two 12 volt Interstate deep cycle AGM batteries in our RV for about 8 years. I recently replaced them with two larger capacity Fullriver deep cycle AGM batteries. Lifeline (as mentioned by MEXICOWANDERER) deep cycle AGM batteries are also very good.

[Boon_Docker]

Still not working.

[Boon_Docker]

Canadian Rainbirds wrote:

Boon Docker wrote:
Trying to post, but server keeps timing out with post longer than one sentence. Help?

What I do where I have a slow internet combined with a slow typist (me 🙂 ) is write my post using Open Office then open RV.NET and copy and paste the text.

Tried that, didn't work either.

[Almot]

It's a server or host issue. Has been like this for a few weeks. Can read but can't post half the time. I go to Woodalls when it does this.

Nuckfan: sorry if it sounded cryptic. I'm still a dummy compared to top guns here.

C is a nominal battery capacity in AH, and recommended charging current is measured in %C. Ex., 0.15-0.2C (typical for wet battery) means 15-20A for 100 AH battery.

SOC = state of charge, or how "full" it is.

Absorption is the stage #2 in any (decent) charger: #1 Bulk (high current, voltage is rising to 14-something), #2 Absorption (voltage is kept at 14-something and current is tapering down), #3 Float (voltage stays at 13-something and current is very low).

When it goes into Abs, battery is 80-90% full and from that point on it doesn't need a lot of current, and small solar can handle this. Having a bigger battery bank helps, since 50 AH drawn from 100 AH bank leaves it 50% full, but same 50 AH off 200 AH bank means 75% full. If you do need to use a generator, do it during the 1st stage, to bring SOC to 80-85%.

[Canadian_Rainbi]

Boon Docker wrote:
Trying to post, but server keeps timing out with post longer than one sentence. Help?

What I do where I have a slow internet combined with a slow typist (me 🙂 ) is write my post using Open Office then open RV.NET and copy and paste the text.

[nuckfan]

Almot wrote:
People with generator and no solar tend to treat their batteries, er... "differenty" :)... I can understand this, given a difficult task of getting it 100% full without having to run darn machine all day and night.

It's not that 255 AH wet battery at 50% "demands" 52A. It can "accept" 52A, but recommended maximum rate is 0.15-02C or 40-50A. Exceeding it will shorten battery life. OTH, charging it at 20A would only result in longer charging time (which you don't want of course).

Keeping it for 2 hours at 14.4V Absorption is also not something curved in stone, this depends on battery and SOC. Majority of solar controllers - especially those with a fixed timer - have 1 hour Absorption stage, as engineers determined this to be sufficient in "most" scenarios.

In any event, 127 AH daily is pretty fat energy budget for a boondocker. With moderate use of microwave you can get by on 80 AH, and without MW - on 30-50 AH.

With planned 150 AH bank, 45 AH daily will put the OP at 70% full in the morning. 200W solar is perfectly capable of delivering that much in summer, even in places like Langley BC. As long as it doesn't rain. 8ft camper sounds like a truck camper - those tend to move around more often than big rigs, and can get some charging while on the road.

Yikes!:h
While I read the first half as my eyes glossed over and my A.D.D kicked in I was thinking sheesh I guess I really don't know squat about this solar/ battery / controller stuff, but after reading it twice I think I almost get it. Umm on the other hand I think I gots me some learnin to do. But yah seriously though it is a truck camper I have,and we do tend to move every 2-3 nights. I installed a Renogy 100W kit on the camper and hope that by adding another 100W and possibly a 150 amp hour battery we will be able to not need to use my gen. Of course that is if the rain ever stops and the sun comes back;)

[Boon_Docker]

OK, thanks! I will try later.

[westend]

Boon Docker wrote:
Server keeps timing out with post longer than on sentence. Help?

That is a local network issue, not RVnet generated. The website server is performing as typical, not fast but not slow.

[Boon_Docker]

Trying to post, but server keeps timing out with post longer than one sentence. Help?