Battery/Solar Configuration

[drhoda]

Proud owner of used 2015 5.0

It came with a 150 watt solar panel and two 12v Interstate deep cycle rv/marine batteries. Previous owner also upgraded the converter so it could be upgraded to AGM batteries when current batteries die.

Wife and I mostly shore camp but like to have dependable battery power for some occasional boondocking. We are pretty heavy users of power when we do dry camp.

I think the batteries are now in need of replacement. My question is what would be the most practical configuration with my existing 150 watt panel:

a) One 12 v AGM battery
b) Two 12 v. AGM batteries
c) Two 12 v. deep cycle batteries like I have now
d) Upgrade converter and add one lithium battery
e) some other configuration

I was about to decide on the two AGM Optima 31 batteries but not sure if two were necessary as they are $300 a piece. Would my solar panel even be able to keep two of them charged?

If I switch to lithium is one battery also adequate?

Any input on specific battery types and manufacturer is also greatly appreciated!

[Vermilye]

One more battery type to consider - Silicon Dioxide. Many of the advantages of lithium, but cheaper, and no low temperature concerns. Biggest downside is no lighter than lead acid (is is a version of lead acid), so you won't be saving any weight.

[Eggscape]

Interesting that the battery is available right here is my home town of Kelowna.

Not to impressed with their solar panel pricing at over $2 a watt. I guess someone has to pay for the store front.

[padlin]

Are you sure it has 2 12v Interstates? ETI usually installs 2 6V Interstates with solar.

I would get away from another set of flooded. For me it'd be a pair of AGM's.

[drhoda]

Originally Posted by padlin

Are you sure it has 2 12v Interstates? ETI usually installs 2 6V Interstates with solar.

I would get away from another set of flooded. For me it'd be a pair of AGM's.

Well each battery has 6 cells so that makes them 12 v batteries right? I assume the previous owner switched to 12v.

So would you replace with two 6v or two 12v AGMs or is one 12v AGM plenty?

[alanmalk]

Originally Posted by drhoda

Proud owner of used 2015 5.0

We are pretty heavy users of power when we do dry camp.

I think the batteries are now in need of replacement. My question is what would be the most practical configuration with my existing 150 watt panel:

I was about to decide on the two AGM Optima 31 batteries but not sure if two were necessary as they are $300 a piece. Would my solar panel even be able to keep two of them charged?

You pretty much answered your own question. A "heavy user" will run an inverter for coffee/microwave/hair dryer/toaster, etc. You will also camp in cold seasons which need the furnace for many hours, run your water pump frequently, perhaps a CPAP machine overnight, etc. A single 100 Ah battery will not give you two days of power without having a major source of recharge - lots of sun and multiple solar panels.

The best way is to start small - one new battery and your current setup. Then go camping and see how long your power lasts (camp near home and be prepared to bail). If you run out of power too soon then add a second battery and try again with charged batteries. If your power lasts as long as you need then see how long it takes for your solar to recharge the batteries. If it takes too long then consider adding second panel. Many of us like a portable that we can use in the winter to aim directly at the sun for efficiency. And it can be left home during warmer/sunnier months when not needed. Others like a permanently mounted second panel on the roof. Take your pick.

But the answer is not just one piece - it is all the pieces together: Your needs, your storage capacity (batteries), your ability to make electricity (panels), and the environment you camp in (warm & sun vs. cold & cloudy vs. heavy tree shade, etc.). You are going to have to experiment and see what works best for you. Your first few trips might be shorter than planned - or perhaps not.

--
Alan

PS. 100 Ah of AGM batteries will provide approximately the same amount of power as 100 Ah of deep cycle marine. 100 Ah of Lithium can give you more power but you flinched at $300. I expect cries of pain when you see the price of high quality Lithium.

[alanmalk]

Originally Posted by drhoda

Well each battery has 6 cells so that makes them 12 v batteries right? I assume the previous owner switched to 12v.

So would you replace with two 6v or two 12v AGMs or is one 12v AGM plenty?

Two 6V 200Ah batteries in series have roughly the same power as two 12 V 100 Ah batteries in parallel. (They also weigh about the same.)

[padlin]

Originally Posted by drhoda

Well each battery has 6 cells so that makes them 12 v batteries right? I assume the previous owner switched to 12v.

So would you replace with two 6v or two 12v AGMs or is one 12v AGM plenty?

If you stick with 12v'ers you can do a direct swap, 2 6v'er require a different cable arraignment. Go with 2 if you can swing it, much better for boondocking.

[drhoda]

Thanks for all the input. Sounds like I need to spring for two 12 v batteries and perhaps a second portable or permanent solar panel. I’m quite willing to pay the extra cost if it gives me more dependable power when boondocking....and keep the wife happy ��

[drhoda]

Any recommendation for a 12 v 100 ah AGM battery i.e a brand or link? So many out there claiming to be the best.

[Perry Butler]

I wouldn't waste my time with one 100 ah battery giving only 50 useable ah's. Do it right the first time. You spent a lot for your camper, enough electrical power is a must as far as were concerned.

There is a reason golf carts use 6v not 12v batteries. Six volt batteries are more robust, and last longer.

A single 100 ah 12 v battery will give you about 50 amp hours (ah's) of usable power. That's not even two nights of running the furnace (along with the other loads). You'll find most here have 100-120 usable ah's of power.

I don't feel a lithium at 100 ah's of usable power is worth $900. I also don't want the maintenance of standard flooded batteries.

We chose to purchase two Crown 6v, 110 ah batteries for $460, giving us 110 useable 12v ah's. AGMs will charge to 85-90% as fast as a lithium. We have no problem charging our AGMs to 100% at least once a week, so our AGM's will probably outlast our camper ownership anyway.

There are other problems with lithiums. The jury is still out if a lithium will actually last longer than an AGM. Will the lithium really hold up? Will the BMS survive over time as well? Lithiums won't charge if the battery's temperature is under 25 F and they degrade rapidly if stored at 105 F or over.

OTOH, if you have space or weight problems, want 200 or more available ah's, and have the discretionary income, lithiums make sense.

I believe the best bang for your buck is two 6v AGM's at under $500.

OTOH, if I were buying batteries today I would purchase a single Azimuth Silicon Dioxide 100ah, 12v battery at $450 US dollars. Silicon dioxide (SiO2) does not have the temperature problems of lithium, like lithium you only need one, but does weigh more than lithium. SiO2 also charge with the same/similar charge profile as lithium. Depending on how you read their charts a SiO2 gives you between 80-90 usable ah's.

Again, don't waste your time with one single 12v 100 ah battery giving you only 50 useable ah's. I would want at least 80 or more usable ah's at a minimum.

As always, YMMV.

Enjoy,

Perry

[drhoda]

So you would go with one 12v silicon dioxide over two 6 v agm...or did I understand that wrong?

[Perry Butler]

Originally Posted by drhoda

Any recommendation for a 12 v 100 ah AGM battery i.e a brand or link? So many out there claiming to be the best.

None are the best.

I wouldn't waste my time with one 12 volt battery when I know I'll use solar, unless it's SiO2.

You can buy two Crown 6v AGM's for $486, or two 6v Lifeline AGM's for $756.

You'll probably find 90% of those here with solar have two 6 volts, not two 12 volts.

Enjoy,

Perry

[Perry Butler]

Originally Posted by drhoda

So you would go with one 12v silicon dioxide over two 6 v agm...or did I understand that wrong?

Yes, but two 6v AGM's are fine too if a non-standard technology (SiO2) bothers you. We don't regret our two AGMs.

Enjoy,

Perry

[BruceW]

We also now have two 6V Crown AGMs. One of the best replacement/upgrades we’ve made. Very happy with performance and price was reasonable. About $440 as I recall. We have a single 270 watt 24 volt solar panel running through an MPPT charger with custom settings to accommodate the AGM charge characteristics. We now are much more likely to run out of black/gray water tank capacity than electrical!

[Vermilye]

Originally Posted by drhoda

Proud owner of used 2015 5.0

It came with a 150 watt solar panel and two 12v Interstate deep cycle rv/marine batteries. Previous owner also upgraded the converter so it could be upgraded to AGM batteries when current batteries die.

Wife and I mostly shore camp but like to have dependable battery power for some occasional boondocking. We are pretty heavy users of power when we do dry camp.

I think the batteries are now in need of replacement. My question is what would be the most practical configuration with my existing 150 watt panel:

a) One 12 v AGM battery
b) Two 12 v. AGM batteries
c) Two 12 v. deep cycle batteries like I have now
d) Upgrade converter and add one lithium battery
e) some other configuration

I was about to decide on the two AGM Optima 31 batteries but not sure if two were necessary as they are $300 a piece. Would my solar panel even be able to keep two of them charged?

If I switch to lithium is one battery also adequate?

Any input on specific battery types and manufacturer is also greatly appreciated!

I'm not a big fan of the Optima series of batteries. They are dual purpose, and true deep cycle such as a pair of 6V Crowns or Lifeline will provide more reserve & likely last longer. Unless you spend most of your time dry camping, it probably is not worth the extra expense of either SiO2 or lithium.

As to the amount of solar vs battery amp hours, a very general rule of thumb is one watt of rooftop solar for each amp hour of battery. Less if you only camp in the summer with more overhead sun than winter camping, more if you camp with low angle winter sun or with lots of clouds & shade.

I do extended winter dry camping with 200 amp hours of lithium batteries & 320 watts of rooftop solar. During December & January & often tilt the rooftop panels for a better angle, and add a 160 watt portable panel. With this combination I do not need a generator. I would consider myself as a heavy power user...

[alanmalk]

Originally Posted by Perryb67

None are the best.
...

I'll second that. There is no such thing as the perfect battery - only the best for your application & needs.

I installed a pair of 12V AGM batteries sold under the Sears label and made by Odyssey/Northstar. They were cheap back then, not so anymore. Another high-end brand is Trojan. Again, a big hit to the credit card - but you mostly get what you pay for. My very first AGM battery was also made by Odyssey and I bought it long before I even thought about a camping trailer. It is now over 8 years old and was working fine the last time I used it. (Now retired in favor of a Lithium - for reasons that are not relevant to camping.)

Pay attention to the battery size. Group 31 is a commonly sized 100Ah and weighs about 75 pounds. Less weight = less power in the lead-acid world.
--
Alan

[Perry Butler]

Originally Posted by alanmalk

Pay attention to the battery size. Group 31 is a commonly sized 100Ah and weighs about 75 pounds. Less weight = less power in the lead-acid world.
--
Alan

Besides being able to charge like lithium, SiO2 batteries can also go down to 100% DOD and still survive. That single 100 ah Azimuth has 100 usable ah's similar to lithium, but like lithium you really don't want to go to 100% very often.

The Azimuth battery weighs 59.5 pounds.

Enjoy,

Perry

[John in Santa Cruz]

I have two Costco/Interstate 6V GC2 batteries in my solar-panelled E21... They aren't quite the same capacity as the premium ones, but they also were only $85 each, and they are still going strong after 3-4 years... they are flooded cell, but I've never had to add any water to them. pretty hard to justify $500 each batteries vs $85 ones. sure, the $500 ones have 10% more capacity, and might last another year or two longer, but $500 can buy a lot of $85 batteries.

[Perry Butler]

Originally Posted by John in Santa Cruz

I have two Costco/Interstate 6V GC2 batteries in my solar-panelled E21... They aren't quite the same capacity as the premium ones, but they also were only $85 each, and they are still going strong after 3-4 years... they are flooded cell, but I've never had to add any water to them. pretty hard to justify $500 each batteries vs $85 ones. sure, the $500 ones have 10% more capacity, and might last another year or two longer, but $500 can buy a lot of $85 batteries.

You mean $170 for a pair, right?

Enjoy,

Perry