Battery/Solar Configuration

[brroberts]

Originally Posted by John in Santa Cruz

I have two Costco/Interstate 6V GC2 batteries in my solar-panelled E21.

My approach has always been 2 cheap 6V golf cart batteries too. It’s worked well, is economical, and fits the charging regimen of my truck. Even without solar, we can go 6 days in the summer. The heater and temps in the winter cut that to a day or two. I hope by having solar on the new Escape I can get a few days in the winter as well. AGM does have a winter advantage, but at not a whole lot more winter capacity, while still a whole lot more cost.

[padlin]

The OP has a 2015 5.0Ta, I had a 2014. I may be the only one but when the batteries got low the high charge rate would kick in and I could smell the batteries cooking. Also had the batteries set off the propane alarm many times. When the time came/comes to change batteries I could see no reason not to change to AGMs which do not off gas nearly as much as the flooded. The OP may be in the same boat.

[Effie]

Originally Posted by John in Santa Cruz

I have two Costco/Interstate 6V GC2 batteries in my solar-panelled E21...

As a retired computer professional I still like new tech around me, after taking delivery of the E19 (with two six volt and solar prep) I started planning the future Lithium & solar upgrade. I love what the Lithium batteries can do but the more I read about it the more I agree with John and Perry, for now I’ll stay with the lead acid. I did install 320w solar and some days I wish I had more. That said, I would have probably upgraded to AGM if I had the E21 trailer, I’m not sure how comfortable I’d be with the acid “bubbling” inside the trailer. I do understand most owners can make it work.

[John in Santa Cruz]

Originally Posted by padlin

The OP has a 2015 5.0Ta, I had a 2014. I may be the only one but when the batteries got low the high charge rate would kick in and I could smell the batteries cooking. Also had the batteries set off the propane alarm many times. When the time came/comes to change batteries I could see no reason not to change to AGMs which do not off gas nearly as much as the flooded. The OP may be in the same boat.

my e21, the batteries are in a sealed box under the rear dinette, with a vent line to the outside, you should not be able to smell ANYthing inside the trailer unless you've opened that box, or the foam 'gasket' isn't doing its thing.

most of the time, its my 160 watt solar doing the battery charging, rather than the converter. the converter acts as a battery maintainer when i'm plugged in.

[padlin]

You're right, I shouldn't, but at high charge, I did.

[Perry Butler]

In our 15 previous campers we always had standard flooded batteries. After ruining the battery in the third camper by not maintaining fluid levels I started checking. Some batteries only needed a little water once a year, but some needed it more often. Yes, that was because of a poor charging system. I didn't like the constant maintenance though. I guess I'm a little lazy.

Before we had solar in our Bigfoot we would drain batteries below 50% quite often, with a couple of batteries not making it two years.

After ordering a 21' Escape (later changed to our 5.0) we found that the batteries were under the dinette seat in a sealed box. There were a few threads on this here. Since I'm lazy, and my back isn't the greatest, I didn't want to go though the contortions of checking fluid levels monthly. Our friends have $700+ Lifelines in their Airstream. Our Crown AGM's were only $450 shipped to our door.

After two years with AGM's we'll never purchase standard flooded again. For us, the extra $250 over a cheap set of flooded batteries is well worth the cost. YMMV. At around $750 extra, lithium is not a good return in our minds. The longest we've ever kept a camper is six years, so with solar and no need for constant maintenance, our Crown AGM batteries should easily go six years.

Enjoy,

Perry

[drhoda]

Originally Posted by Vermilye

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. .

So if I have 150 w solar panel I need 150 ah battery? If I get a 225 ah the solar panel won’t be able to charge them?

Does this mean if I have two 6v batteries I need 75 ah each?

[Perry Butler]

Originally Posted by drhoda

So if I have 150 w solar panel I need 150 ah battery? If I get a 225 ah the solar panel won’t be able to charge them?

Does this mean if I have two 6v batteries I need 75 ah each?

There are many variables involved to make a 1 watt needs 1 amp hour battery hold true. That is merely a simple guide.

You can charge a 225 ah battery with your 150 watt solar panel. We charged our 220 amp AGM batteries just fine with a 170 watt solar panel. HOWEVER, if you are a heavy user, mostly by using an inverter for a microwave or Instapot, Keurig, etc., you'll need more solar to replace the extra ah's these devices use.

We also have a 100 watt portable and could use that to refill our batteries. Because portables are at an angle, and can be moved to follow the sun they are more efficient, but I find them a PITA to use. We use our portable only when our 170 watt panel is in the shade, putting out literally no amp hours.

We camp in the shade quite often in Minnesota. I'm mechanical and understand solar wiring, so I'm adding 2-3 100 watt solar panels to our 170 watt solar panel, giving us 463 theoretical watts after figuring combination loss from mismatched panels. And yes, we're looking at installing an inverter for a toaster.

You also need to decide if your batteries have enough usable amp hour capacity. Our 220 ah AGM batteries had 110 usable ah's (180 in a once a year pinch). I feel with any camper you should have at least 100 usable amp hour capacity, but that's only my opinion. Heavy users want more.

Enjoy,

Perry

[Centex]

Originally Posted by drhoda

So if I have 150 w solar panel I need 150 ah battery? If I get a 225 ah the solar panel won’t be able to charge them?

The "very general rule of thumb" Jon mentions is based on some inexact set of assumptions about the level of battery depletion and the amount and duration of solar exposure during a day. Any amount of solar panel 'rated watts', with at least some solar exposure, will contribute some charge to your battery / batteries, whatever the rated Watts to rated Ah ratio.

The question is whether or not that will be enough to 'keep-up' with your battery depletion over a period of time. In a very simplified example:

• Let's assume you start with a 100% charged battery and you want to never allow the battery to go below 50% charge
• Let's assume you deplete your batteries 30% each typical day
• Let's assume your PV panel and solar exposure will replenish 20% of that each typical day
• In that scenario you will run with a net battery depletion of 10% each typical day (-30%+20%=-10%/day)
• In that scenario you would be able to operate for about 5 days before you hit your 50% battery discharge 'limit'

Obviously much in that scenario depends on your actual battery demands per day, your actual solar harvest potential (panel rating), and your actual solar harvest (amount and duration of solar exposure per day).

You will not know how that will all 'actually balance-out' for you specifically until you experience your own actual use scenarios. But the "very general rule of thumb" Jon mentions is oft-cited by many different 'authorities', so likely is a decent indicator for a 'very general sample' of users / user scenarios (that's the nature of "rules of thumb"). YMMV.

[John in Santa Cruz]

Originally Posted by drhoda

So if I have 150 w solar panel I need 150 ah battery? If I get a 225 ah the solar panel won’t be able to charge them?

Does this mean if I have two 6v batteries I need 75 ah each?

when you connect batteries in series, you add the voltage, and the amps stay the same (so 6+6 = 12V.... typical golf cart 6V battery is 210-225 amp*hours).

its when you connect batteries in PARALLEL that the voltage stays the same but you add up the amp*hours, so 2 12V 100AH batteries in parallel would be 12V at 200AH.

that rule suggests the MINIMUM solar panel, more solar charging than you need doesn't hurt anything other than your wallet, it just charges the batteries faster, while less solar means they will take longer to charge but still may be sufficient.

I've been using 160W rooftop solar panels with dual golf cart batts rated at 220AH, and its worked just fine, but I avoid heavy current uses such as trying to microwave with an inverter.

[RangerMan]

I have the ETI installed Inverter and I use it for microwave, toaster, coffee maker, etc.... That's what it's for and why I got it.

That said, I wouldn't put a chicken in the microwave. That's asking a bit much!