Solar Questions from a Solar Noob

[Larry-NC]

Originally Posted by Flybob

I think what is confusing things is you are using amps at several different voltages. 80A (this is actually 80AHr) in an entire day is 3.3A or roughly 6.5A for an item that only runs 50% of the time ( as you stated earlier). This current X the number of hours it is drawn is the number of amp hours. The problem is this is 80AHr at 120VAC. The 12VDC current needed to supply that is ten times that number or 800AHr at 12VDC. As suggested, I would get a Kill-a-watt and actually measure the fridge power consumption.

This is why it makes sense to work in watts and only convert to amps at the end.

The principle of Conservation of Energy is why you can treat the inverter as watts-in = watts-out.

[IchLiebeBier]

I'm tracking, and I appreciate all the responses. I just can't understand why https://gpelectric.com/calculator/ would say the residential refrigerator uses only 120 amp hours for the daily draw (10 amps for 12 hours).

The math is so far off from that it's just unbelievable to me that a site would put that on there. I guess they realize if the answer is that you need 14 solar panels no one would buy one.

EDIT: it occurred to me that MAYBE they're basing their number off of 1 amp running current, which, after multiplying by 10, gives you the number the calculator returns. Don' know, and can't find it on their page.

Anyway, I just ordered the Kill a Watt to test the fridge on our first trip this year. Then I'll know.

[tomkatb]

Salesman talk!

Got to get good with the math.

Remember solar panel data is from Mexico City on a sunny day for an hour. On the equator.

Refrigerator information used is not from south Texas! Manitoba maybe,

Got to learn the math. Kentucky windage!

For us in the Midwest who travel during the summer, the solar math does not work.

For folks in California who camp in the mountains, works a treat.

I think you will be running a generator every other day or more.

I assume the salesman told you this about the fridge. These fridges are really nice and cheaper than a gas electric fridge. My 12 cu ft fridge was about ,$2400 vs your fridge which I would guess was way short of $1000. $500.

You would need 6 or more solar panels to charge a lot less.

I would pack your generator now and get camping. Love those batteries. You have 24 hours between charges.

Used my Honda 2200 yesterday to top up my batteries. Heading to Pigeon forge at the end of March.

[IchLiebeBier]

tomkatb,
I didn't have a problem with the fridge when we bought it because we usually camp with shore power. I only changed things up to allow me the flexibility to boondock for short trips, particularly in good fly-fishing areas.

So based on my equipment, you think I'd have up to 24 hours? That lines up with the online calculator.

I wanted to camp on the TN side, but Elkmont doesn't support my trailer length apparently. Shame too. I like fishing that river. Plus more to do in PF than Cherokee.

But the NC side has pretty good fishing, too. I've just fished almost all of them. I was looking for something different this time.

[tomkatb]

Yes. Most of the time.

I would assume you have a good monitor for the batteries. It will warn you via Bluetooth when getting low.

You are good.

I would think about solar. No matter how much you put on the roof it will not always be enough.

We went to Townsend last year. Cruddy campground. Our trip was Rainey.

I have been a fly fisherman in the past. As I am getting old and whimpy, I thought fishing there would be too much. Will look into it more. Are Tennessee fishing permits are cheap?

[IchLiebeBier]

I got the Victron BMV-12, so good to go.

I figured I'd start with 200 watt portable solar suitcase and see how it does. I want to park in the shade, so portable is probably better for me in the long run.

License costs aren't too bad. https://www.tn.gov/content/tn/twra/l...ml#nonresident

You may or may not need a trout stamp. Last time I fished the Smokies you didn't. And if you fish the Smokies, you can get either a TN or NC license, and fish on either side of the line (reciprocity). I'd go with whatever is cheaper and/or more convenient. If you fish in the Gatlinburg area off park I think you need the trout stamp.

Most of the fishing in the Smokies is in smaller streams. Not really difficult to wade, but rocks are slicker than snot. Felt wading boots help. Low hanging trees, too, so I usually fish with a 6' fly rod, 5 weight. Makes line management a bit of a challenge, but fish are in the water, not the trees.

I also have a 5', 3 weight rod when I go after the brookies at higher elevation. pretty fun.

[tomkatb]

Something approaching a 200 watt suitcase would be fun to try.

40-50 amps perday.

I think the factory solar plug in would be heavy enough. Not sure. Close I think.

I have fished mostly with a 6' ultralight rod. We meet the kids in Missouri once a year to fish.

Last year I used a 7 1/2' heavier rod. Boy, is casting easier.

In most of the US felt soled boots are against the law. They say it allows microbes of invasive species to travel between areas. The wading concerns me. Crossing a lot of fast water I ask for a kid to be near.

We were somewhere last year in a rest spot that was inspection out of state boats for growth. So I guess it is serious.

[IchLiebeBier]

I think I would just hook directly to the batteries. I may have said it earlier in the thread...I think the factory furrion plug is only rated for 10 amps.

But I would be interested in knowing how to connect the suitcase. My batteries are in parallel with the victron shunt. Should I just attach both cables to one battery, or should I attach positive to 1 and negative to the other? Or, option 3, should I attach positive to one, and negative to load side of shunt?

I don't know if not factoring in the shunt will throw off the Victron's data.

Also, connecting solar panels to the batteries is like connecting another battery in parallel, correct? I mean, it doesn't up the voltage or amps any to connect 200 watts of solar to the battery, right? I don't want to fry anything because I did it wrong.

I'm leaning towards the Renogy legacy panel suitcase right now. One thing I can't figure out from website is if I get another suitcase later (or just the panels), can I connect them in parallel together? It doesn't seem like the suitcase controllers allow that. Plus, they may not come in enough amps to do it. May have to just connect the two independently, one to each battery.

Thanks for your help.

[hobienick]

I don't think your batteries are in parallel with the Victron Shunt. It should have one side connected to the battery negative and one side for all other negatives (load side).

If you want to track how much energy you are gaining from solar you will need to make sure you connect solar controller neg to the load side of the shunt. Otherwise, you will not read how much the solar is charging.

You need to connect the solar panels to a charge controller, then connect the charge controller to the batteries. The controller will keep you from frying anything if connected correctly.

If you connect the panels to the battery without a controller you will be upping the volts if in series or upping the amps if in parallel.

There is plenty of info on this forum, YT, and the internet on how to wire up solar. It may be worth a few minutes of time to make sure you have everything organized.

[IchLiebeBier]

My batteries are in parallel, with a victron shunt attached, is what I meant. It is wired correctly to the shunt. I meant to say attach the negative to the battery side of the shunt, not load side. My mistake.

For the panels, I meant that if I had two suitcase kits, each would have its own controller, so I would hook the suitcases independently to the batteries. I can't figure out how to buy two suitcase kits with one controller from Renogy. I can't find the option.

Plus the controller that comes with the 200w kit is 20 amps. I'd need more amps to attach another suitcase panel to it. But I'm seeing that the higher amp ones don't seem to be waterproof.

BTW, the problem with telling people to do more research is that you assume that they haven't. Unfortunately, I can't find any good online info about how to attach the panels to two batteries that are in parallel AND that have a Victron shunt in it. One site will say one thing, another will say something else. While this type of activity may make sense to some people, it doesn't to others. That's why people ask questions on the forums.

Now, if this site is not intended to help people out without fear of being belittled, I guess us noobies should learn this sooner rather than later. This seems to happen too frequently for my liking.

[babock]

When you hook up the solar controller to the batteries, the negative side of the controller has to be on the load side of your shunt so that the BMV can measure all current put back into your batteries.

When you say the 200W kit is 20A, I am assuming you mean the controller that comes with it is a 20A controller...is that correct? A 200W kit will put out around 14A max assuming it is a PWM controller. Most of these kits are PWM.

What a lot of people do instead of buying the kits is to mount a large controller next to the batteries, buy 2 panels and install a hinge between the panels so they fold onto themselves.

I have a 700W system mounted on my roof with a 50A Victron MPPT controller. I can help you with a lot of your questions. You can PM me if you want.

Once you know the actual amount of power your fridge uses in a day, That will help you a lot in determining the amount of battery and solar you will need.

[GoneSouth10]

Originally Posted by babock

When you hook up the solar controller to the batteries, the negative side of the controller has to be on the load side of your shunt so that the BMV can measure all current put back into your batteries.

Yup, 2X on this. Just did this exact hook up yesterday (330W "kit" with an El Cheapo 20A PWM controller). Positive feed from the controller to the positive battery terminal and negative feed from the controller to the "load" side (i.e., opposite of the single cable from the negative battery terminal to the shunt) of the Victron shunt (I have the BMV-712). Works like a charm!

[IchLiebeBier]

Thanks babock and gonesouth.

Yes, 20 amp controller. I'll start looking at piecing together the panels and see if that would work better for me. I'd rather hook it up like that anyway, since I lock up my batteries with lock bars, and it would be a pain to have to unlock them every time I connect the alligator clips. I'll probably take you up on the PM thing.

The load side thing makes sense to me. I had it right the first time. Just got confused reading the comment I guess. My lack of confidence with this topic doesn't help any either

I wasn't sure if the shunt prevented backwards flow either. I guess not.

[babock]

Originally Posted by IchLiebeBier

Thanks babock and gonesouth.

Yes, 20 amp controller. I'll start looking at piecing together the panels and see if that would work better for me. I'd rather hook it up like that anyway, since I lock up my batteries with lock bars, and it would be a pain to have to unlock them every time I connect the alligator clips. I'll probably take you up on the PM thing.

The load side thing makes sense to me. I had it right the first time. Just got confused reading the comment I guess. My lack of confidence with this topic doesn't help any either

I wasn't sure if the shunt prevented backwards flow either. I guess not.

Take a look at your BMV when your converter is charging your battery...should see current going back into the battery

[hobienick]

Originally Posted by IchLiebeBier

My batteries are in parallel, with a victron shunt attached, is what I meant. It is wired correctly to the shunt. I meant to say attach the negative to the battery side of the shunt, not load side. My mistake.

For the panels, I meant that if I had two suitcase kits, each would have its own controller, so I would hook the suitcases independently to the batteries. I can't figure out how to buy two suitcase kits with one controller from Renogy. I can't find the option.

Plus the controller that comes with the 200w kit is 20 amps. I'd need more amps to attach another suitcase panel to it. But I'm seeing that the higher amp ones don't seem to be waterproof.

BTW, the problem with telling people to do more research is that you assume that they haven't. Unfortunately, I can't find any good online info about how to attach the panels to two batteries that are in parallel AND that have a Victron shunt in it. One site will say one thing, another will say something else. While this type of activity may make sense to some people, it doesn't to others. That's why people ask questions on the forums.

Now, if this site is not intended to help people out without fear of being belittled, I guess us noobies should learn this sooner rather than later. This seems to happen too frequently for my liking.

I had no intention of belittling you. If I came across that way I am sorry. We can only go by the information you provide in your posts when you are asking questions. As you mentioned above the information provided was incorrect. It sounded as if there was some foundational learning that needed to happen before diving into the troubleshooting. Once you provided correct information you got some very good answers.

Feeling belittled is up to each individual. As I said that was not my intent nor do I feel I came off that way. Mentioning that more research is needed should not make anyone feel bad. When I was learning how to do this 10 years ago I did the research. It took time and experience. Making mistakes is not bad. Not learning from the mistake is bad.

Babock and GoneSouth have given you good advice. Babock has many posts on this forum about 12 V systems that have good information in them. Those posts would be a good place to learn some of the things you are looking to learn.

[formerFR]

I find that the numbers for 'residential fridge' amperage draw can be overstated, since many times the manufacturers are using 'maximum' draws, which is not realistic, day to day, or hour to hour.
Much will depend on the outside temps, the inside temps of your coach, how often you open the door, what temp setting you have it set to, how much you have within the fridge,etc...
Ours, on medium temp, will run several times per hour, for maybe 5 minutes or so each time, but certainly does not run constantly, or even 1/2 of the time, unless you are in and out of your fridge all the time.

Just today, while watching my Magnum inverter panel when the fridge compressor kicked on, it only dropped 2 volts on the battery level while running, and when finished several minutes later, the battery voltage went back up to the same overall voltage reading it was at before the fridge kicked on.
If you have 2 12v batteries, you'll experience faster drops, of course, and if you have 2 6v deep charge batteries, you'll get more time before needing to charge. If you have 4 6v deep charge batteries, in series and parallel, and they are newer or are fully charged and in good overall condition, you may go 12 hours or more before recharge.

[GoneSouth10]

Originally Posted by IchLiebeBier

Just got confused reading the comment I guess. My lack of confidence with this topic doesn't help any either

Speaking of confusion (and why even research doesn't necessarily help), one thing I did discover yesterday in the process of working this through was that the documentation with the BMV-712 is confusing, if not misleading.
I had wanted to use the second monitoring port (the B2 input on the shunt) to monitor voltage of the chassis battery, which is about 6-8 feet away from the house batteries (and from the shunt). I understood it would simply be a voltage monitor (not current), but that was enough and I'd be able to access it on my phone app. However, when I looked at the wiring diagram provided by Victron, it showed the voltage lead (18 AWG) from the positive terminal of the chassis battery, but also showed a full on battery cable (I'd need 2/0 for that length, maybe?) from the negative terminal of the chassis battery to the shunt. It wasn't worth it to route that heavy of a battery cable up and over two bays, so I just said "Forget it" (or something like that ). In the (very) back of my mind, I thought, "Hmmmm - Wouldn't I only need the negative connection to the shunt if I was measuring current? Isn't the whole coach a ground if I just want to measure voltage? " Well, I assumed the Victron documentation was correct so I forgot about it and just installed the temperature sensor into Input B2.
Lo and behold, curiosity got the better of me yesterday and I just connected the single wire to the positive terminal back to Input B2, switched the accessory function in the app to "Starter Battery" and voila - I had visibility on my chassis battery voltage.
I've now got a three position rocker switch (A - Off - B) where I can switch back and forth between temperature and chassis battery. The only glitch is I have to reset the "Auxiliary" selection app on my phone each time I switch over from temperature to chassis battery, but at this point (whole 'nother story), I'm more concerned about my chassis battery than about the house battery temperature.
Bottom line, even researching the source documentation can lead you astray!!

[Flybob]

Keep in mind that if the panels are mounted at a distance from the batteries ( portable). It is best to have the controller close to the batteries and have the longest run between the panels and the controller. The panel will output in the 17+ volt range so a little loss in the wiring to the controller will still allow good operation. If the controller is on the panels, the output to the batteries will be around 14V so a loss going to the batteries will impact the charge capability.

[babock]

Also keep in mind, If you use a Victron solar controller, they can talk to your BMV and the BMV will tell the solar controller the exact battery voltage that is sees so the solar controller can adjust its output voltage to account for line loss between the controller and the battery. The Victrons are also MPPT controllers so more efficient than the PWM controller you will get with a portable solar panel kit.

[IchLiebeBier]

babock and flybob,
Both great info to know. I wouldn't have though of either.

Gonesouth,
I agree, the Victron manual and quick connect guide are very lacking. I even emailed Victron with a question about hooking the negative leads because I was confused about something with their diagram. Instead of answering me, they said I should ask a local installer. Real helpful.