2d battery or 2d panel?

[Newbie]

We've got an 85-watt solar panel from Go Power! and an Optima D31M (75 AH) battery in our Scamp that has done well so far powering our Fantastic Fan, water pump, LED lights, 3 automotive charging outlets, and an infrequently used 600 watt inverter. We are about to add an Engel fridge with a rating of 2.7 amps, and I'm wondering whether it's time to upgrade the system. Currently, the 85-watt panel brings the battery up to full charge by early to mid morning on most days, so I'm thinking an extra battery might be the best choice.

What are folks' experiences with adding an extra battery versus an extra panel?

[Paul Braun]

By asking about a second battery, are you planning an additional 12 volt or replacing both with 6 volt? The six volt would be the preferred option if you have the room and can handle the weight. Adding a second 12 volt may have implications with the need to have exact or near exact batteries, depending on how you use the second battery.

There is a thread on the Escape forum from someone installing a 12 volt Nova cool, my recollection is they found they needed a second panel even with dual 6 volt batteries. They did use a different model of refrigerator. Here is a link.

[Rob V]

Consider this calculator. It (or one of the many available) will actually answer your question based on just the facts:

http://www.batterystuff.com/kb/tools...-tutorial.html

[Gordon in Idaho]

Since you are investing in a high-end fridge, why not go the whole 9 yards? It made my head hurt trying to work through the formulas to calculate exactly what I needed when I set up my "solar system". And who can say what your future needs might be? Impossible.
So, my free advice: Buy all you can afford/fit/carry, and don't look back.

Gordon

[steve dunham]

Originally Posted by Paul Braun

By asking about a second battery, are you planning an additional 12 volt or replacing both with 6 volt? The six volt would be the preferred option if you have the room and can handle the weight. Adding a second 12 volt may have implications with the need to have exact or near exact batteries, depending on how you use the second battery.

There is a thread on the Escape forum from someone installing a 12 volt Nova cool, my recollection is they found they needed a second panel even with dual 6 volt batteries. They did use a different model of refrigerator. Here is a link.

Paul ; When I took a class on solar ,we were told that there is a correlation between the amount of solar needed , the storage capacity of your batteries and usage.
We were told that having a large battery storage capacity coupled to a too small solar system does not work well. The inverse , having an overly large solar system with limited battery storage capacity was not the answer either .Am I missing something ? Should the batteries and solar panels be in line with one an other?

[sokhapkin]

Originally Posted by steve dunham

We were told that having a large battery storage capacity coupled to a too small solar system does not work well. The inverse , having an overly large solar system with limited battery storage capacity was not the answer either.

You were told absolutely right thing. Everything needs to be balanced.

[Briantb]

How old is the original battery? You can't just add a battery to a system - the old battery will drag the new one down to the level of the old one

Sent from my SM-T230NU using Fiberglass RV mobile app

[rick in arvada]

I've been trying to get a handle on the solar thing for a decade now and have concluded that the best advice is to get close to a balance of 1 watt of PV panel to 1 AH of battery. I'm not quite there since I ran out of roof room. C'est la vie. The other important standard is "big wire".

[Huck]

I think the frig means you will need both another panel and another battery and that still might not be enough.

[MCDenny]

I've got two 6v 225 ah batteries, a 100w panel and a 12v truckfridge that uses about the same power as yours. In sunny weather, in the spring I'm fine, in the winter I need to aim the panel at the sun to keep up with the drain. I can go 3-4 days with no sun.

2.7 amps with a 1/3 on time duty cycle is 22 amp hours, probably about what your panel would produce without tracking the sun. If you get behind due to bad weather you don't have enough panel power to catch up.

More battery capacity will let you get through a longer cloudy period.


Denny Wolfe
Wanderingourway.wordpress.com

[Byron Kinnaman]

Both.

[Mike Magee]

Jeff, what are you replacing, an LP fridge? Is that why you're thinking ahead about the extra power consumption?

You could start by installing the new Engel and leaving the rest as it is. Run the fridge and the stuff you normally would, with the panel collecting sunlight, for a day or two. Monitor the battery's voltage 2-3 times per day and see how it's doing. (You could do this in your yard at home, or at a campground.) 12.1V is about the halfway mark on the battery's state of charge, and full is roughly 12.8V. Check it first thing in the morning, maybe at midday, and definitely again late in the day. If the battery is getting charged back up close to full by day's end, super. If it's staying above the halfway mark at its low point (early a.m.), it's still doing well enough that your battery won't be harmed.

If you find that the solar input cannot keep up with your usage, under your circumstances (existing battery with some age) I'd suggest adding another panel and see if that keeps you in good shape. If it does not, the next step would be to replace the battery with a matched pair of new batteries.

[Timber Wolf]

I vote both, which is my plan if I ever get around to actually installing the solar system I bought last year. That said, do you have other options for charging if you do a staged approach and just upgrade your batteries now? In other words such options as, moving and charging from the TV while on the road, small genny, etc?

[ckayaker]

I run much the same items as you are AND have an Engel fridge. I run totally on solar with a 50 watt panel and a 105 amp/hour battery. Last summer, my first running this system, I only had one iffy stretch of cloudy days where the battery got down to 60%, otherwise I was fine. I'm installing a battery monitoring system to keep closer tabs on the battery this year.

[MCDenny]

Summer vs winter makes a huge difference.


Denny Wolfe
www.wanderingourway.wordpress.com

[Night Sailor]

The rule of thumb is one watt of Solar for every AH of battery capacity. After months of study I found the number to be 1.5 Watts of solar (or more) for every AH in cloudy areas.

My goal was to recover a full charge on a bright overcast day. I know get 1-2 Amp of charge-- not much, but something, on dark heavy rain days. In this case it doesn't matter where your panels are pointing.

My point being that while there is a rule of thumb, someone full
Timing in a camper will always appreciate extra charging capabilities. Extra panels don't hurt.

Finally while I have a mix of flexible panels and rigid. The rigid are slightly more efficient charging, and provide shade for my camper, at the expense of increases wind drag while moving.

One 100 watt panel should provide for your Engel fried/ freezer and another for the house loads with the surplus helping with the fridge. 200 Watts of panels and 200 AH @ 12V for the batteries. Add an extra solar panel in a cloudy area. Leave room to expand as power is addictive and will prolong your battery life.


Sent from my iPhone using Fiberglass RV

[Timber Wolf]

Originally Posted by Night Sailor

The rule of thumb is one watt of Solar for every AH of battery capacity. After months of study I found the number to be 1.5 Watts of solar (or more) for every AH in cloudy areas.

That fits well with what I surmised last year when studying this issue. I finally came up with the "double everything" rule of thumb. It starts with the batteries. Since you don't want to go below 50% charge, you need twice the battery capacity right off. Cloudy days or poor panel orientation, you might need twice the panels calculated. And so forth. In any event you pays your money and takes your chances. Luckily most of us don’t start out camping weeks on end and depending on a system right off. Most can ease into things with a possibly too small setup and still get by for a few days until they learn their actual usage and needs.

[Larry,C]

Of course it depends on where you plan to camp and the weather and your energy needs. With conservative use you should be able to get by with 100 watt solar panel and 1 - 12 volt battery. If you depend on your battery for your electricity (boon docking for more than a couple of days) I recommend additional battery/s. If you go with a permanent panel installation I recommend additional panels because they will not always be in an optimal position to catch the sun. I have set mine up for any conditions. 2 - 6 volt golf cart batteries with 3 - 100 watt panels and 2 - 50 watt panels fixed and oriented in different directions to be able to collect some energy no matter how or where I park. So far I have had enough electricity to meet my not so conservative consumption needs.