Parasitic Draw on RV?

[LipschitzWrath]

I am getting ready to add a small solar system to the top of my 5er to keep the batteries topped off when we leave the camper at the lake for extended periods. My wife and I generally pull the camper out on a weekend and then leave it there for weeks at a time. We pull it to a nearby dump station when we need to dump or add water. We cycle LP tanks to keep the fridge cold.

Last weekend, we returned to our camper after two weeks of leaving it unattended. The batteries were COMPLETELY dead. This seemed odd to me. I mean, assuming we turn everything off before we leave, the only draws are the LP/CO detectors and the little current draw to run the fridge in LP mode, right?

So how much juice do these items consume?

After doing some internet research, I found one site where some dude claimed these items add up to approximately 37Ah in a 24 hour period. I've seen other sites say the fridge pulls 17-20Ah per day by itself in LP mode. The fridge is a Dometic fridge/freezer, I don't have the model number handy but it's from 2004.

Do these numbers sound right?

I have 210Ah of AGM batteries installed. If these numbers are close, then that would certainly explain the dead batteries.

This brings me to the solar panel install. I guess a secondary question would be, do you guys think a single 100W panel would be sufficient for the sole purpose of keeping the batteries topped off when the camper is unattended?

I don't mind occasionally running the generator(s) when we are actually out there using the camper.

Thanks in advance!

[Almot]

pianotuna wrote:
two words

Voltage Drop

Yep. Rated cable ampacity, i.e. max current that the cable can carry before it melts down, is a different thing.

Voltage drop exists with MPPT controllers as well, but far less important than with PWM because currents are lower.
Ex, with MPPT #10 cable would suffice for arrays up to 700W if not more.
With PWM you'll need at least #8 for planned 400W - BFL is probably right about this, I never owned PWM - and you won't be able to expand to 600W that SC-2030 allows.
It's also nice to be able to use MC4 extension cable all the way to controller, and I doubt they come beefier than #8.

[pianotuna]

two words

Voltage Drop

LipschitzWrath wrote:

Kinda getting off-topic but I never understood this. Even at 12V, 400W = 33A. 10AWG is capable of that, and 8AWG, like I have, is rated to 40A. In reality, panel voltages are higher, which translates to less current, which only improves this.

I guess what I am driving at is I don't understand why people are running 4AWG cable to their panels when they have a 400W array.

Are they just doing it to minimze resistance?

[BFL13]

LipschitzWrath wrote:

BFL13 wrote:
You want the 500a shunt not the 100a so when you get the 2000w inverter that is coming next 🙂 you can pull over a 100a and have no issues.

Some places sell the Tri with everything, and some sell the items separately. If you use the 500a shunt as your buss/junction, be aware the bolts in the shunt are quite short and can only hold a few ring lugs stacked at a time, so you might still want the buss/junction to have more places to put ring lugs.

The solar controller that goes with the Tri has a shunt too ISTR and it gets convoluted for sharing shunts and all that. Was a thread about this recently. You are probably ok with the controller you have.

#8 to the roof should be fine, but you will be able to tell once you are out in the sun and check the controller's display for "expected amps"

Why on earth does the SC-2030 need a shunt? If connected to the TM-2030, why can't that information be shared? Seems stupid to have two shunts.

I have that wrong, thinking about that Kid (sp?) one. Sorry!

[LipschitzWrath]

BFL13 wrote:
You want the 500a shunt not the 100a so when you get the 2000w inverter that is coming next 🙂 you can pull over a 100a and have no issues.

Some places sell the Tri with everything, and some sell the items separately. If you use the 500a shunt as your buss/junction, be aware the bolts in the shunt are quite short and can only hold a few ring lugs stacked at a time, so you might still want the buss/junction to have more places to put ring lugs.

The solar controller that goes with the Tri has a shunt too ISTR and it gets convoluted for sharing shunts and all that. Was a thread about this recently. You are probably ok with the controller you have.

#8 to the roof should be fine, but you will be able to tell once you are out in the sun and check the controller's display for "expected amps"

Why on earth does the SC-2030 need a shunt? If connected to the TM-2030, why can't that information be shared? Seems stupid to have two shunts.

[BFL13]

You want the 500a shunt not the 100a so when you get the 2000w inverter that is coming next 🙂 you can pull over a 100a and have no issues.

Some places sell the Tri with everything, and some sell the items separately. If you use the 500a shunt as your buss/junction, be aware the bolts in the shunt are quite short and can only hold a few ring lugs stacked at a time, so you might still want the buss/junction to have more places to put ring lugs.

The solar controller that goes with the Tri has a shunt too ISTR and it gets convoluted for sharing shunts and all that. Was a thread about this recently. You are probably ok with the controller you have.

#8 to the roof should be fine, but you will be able to tell once you are out in the sun and check the controller's display for "expected amps"

[LipschitzWrath]

Almot wrote:
Somehow I missed this:

The good news is the solar kit I bought is easily scalable to 400 watts without any other modifications

Yes, if you route the cable from panels to controller beefy enough for 400W. Especially with PWM controllers.

Kinda getting off-topic but I never understood this. Even at 12V, 400W = 33A. 10AWG is capable of that, and 8AWG, like I have, is rated to 40A. In reality, panel voltages are higher, which translates to less current, which only improves this.

I guess what I am driving at is I don't understand why people are running 4AWG cable to their panels when they have a 400W array.

Are they just doing it to minimze resistance?

[Almot]

Somehow I missed this:

The good news is the solar kit I bought is easily scalable to 400 watts without any other modifications

Yes, if the cable from panels all the way to controller is beefy enough for 400W. This is particularly important with PWM controllers. That's why I don't like them 😉

[LipschitzWrath]

Almot wrote:
They are very legit and a popular place to go, if you ask anybody on this forum. Voicemail can be full, yes. Availability of panels in solar stores can be a problem these days, due to tariffs.

Fair enough, didn't mean to ruffle any feathers. My issue was that their website said free shipping and it wasn't giving me free shipping. The only way to correct would have been to call them. Couldn't do that, so I moved on.

Thanks for the tip on the SC-2030. I'll definitely be considering that.

[Almot]

LipschitzWrath wrote:

Except that place {Solar Blvd} is not legit at all.

They are very legit and a popular place to go, if you ask anybody on this forum. Voicemail can be full, yes. Availability of panels in solar stores can be a problem these days, due to tariffs.

My fridge, radio on standby and LP detector draw 11-12 AH a day.

With 400W on tap and our camping lifestyle, we'd probably never have to run the generators except when we want to use 110V appliances (mainly the blender) or the AC.

I suggest you get acquainted with some small inverter, to run a blender. Cost ~$100 for a good one.

Mostly, the reason to run a generator with solar of your size is microwave. If you can handle propane stove, you won't have to run a genny. Alternatively, you could expand solar to 400W (500-600W with some 30A controllers but they don't include those with cheap kits), get much bigger inverter and run microwave off the batteries as well.

Yes, A/C needs a generator. This is the only item that is difficult to have on solar.

A Trimetric {battery monitor} is certainly on the list

All the more reason to throw an entry-level controller away, and to buy Trimetric add-on controller. It is an add-on, doesn't work well without their monitor, but with the monitor it works perfect AND allows up to 600W array, if memory serves me well. It won't output 600/12.6=48A, only 30A, but it will use 600W nicely on cloudy days.

[LipschitzWrath]

BFL13 wrote:
The controller should go where the converter is if possible, up near the batteries. Controller to battery and converter to battery in parallel to the same battery posts. Or you can run the controller wires over to the converter's output terminals, which then share the wires going to the battery.

You don't need to see the controller display from inside unless you are "easily entertained", and you can get some of that solar info from your Trimetric display inside anyway.

If you get a battery monitor like Trimetric with the 500a shunt, now all your negs go to that instead of to the battery including the solar's and converter's, and the previous frame to battery neg wire.

This can affect the length of the various neg wires and how you do your neg buss bar if any. So make the decision to go with a Trimetric (or Victron) before you get too far along.

A Trimetric is certainly on the list, but I don't know when. If you read my other thread, you'll notice I used a ground junction block. One of the reasons I did so is that I should be able to easily replace the junction block with the TM shunt when I do get one. Put the battery negative cables on one side of the shunt and everything else on the junction block on the other and should be good. No battery lugs to mess with, all the work is already done.

BTW, does the TM come with the shunt, or is that a "sold separately" item? Reason I ask, unless there is a kit that already includes it, I could install it now. Wouldn't the 100A shunt be sufficient for me?

Anyways, my solar charge controller is located almost exactly between my converter and battery bank. The solar batt negative wire goes down to the frame ground 3 feet away. The positive goes to the circuit breaker feeding the batteries. I would think there would be VERY, VERY little resistance with the way I have it wired.

Now, I am still having an issue with my PV kit. It is a Renogy 100W with their Adventurer 30A PWM controller. I am adding a second panel tonight to bring it up to 200W. I had the converter shut off all day yesterday to remove that from the equation.

When I got home, the BT app was showing that the panel was generating 140W. Okay, whatever. The amps x volts did calc out to 140W. I figured maybe it was a comm error via the bluetooth, but the controller LCD screen is spitting out the same volts and amps coming from the panel. The nameplate on the panel confirms it is a 100W panel at STC's.

I thought no big deal until after the sun went down and it was saying the panel was still putting out 110W. The voltage was depressed but the amperage was multiplying out correctly.

Any ideas? I called Renogy and they were little/no help.

Something I wired wrong?

[BFL13]

pianotuna wrote:
BFL13,

The OEM converter for my RV is at least 15 feet from the battery bank. So my controller is no where near the converter. I ended up with a run of about 4 feet to the bank.

The OP has his converter already close to the batteries per his other thread.

[pianotuna]

BFL13,

The OEM converter for my RV is at least 15 feet from the battery bank. So my controller is no where near the converter. I ended up with a run of about 4 feet to the bank.

[BFL13]

The controller should go where the converter is if possible, up near the batteries. Controller to battery and converter to battery in parallel to the same battery posts. Or you can run the controller wires over to the converter's output terminals, which then share the wires going to the battery.

You don't need to see the controller display from inside unless you are "easily entertained", and you can get some of that solar info from your Trimetric display inside anyway.

If you get a battery monitor like Trimetric with the 500a shunt, now all your negs go to that instead of to the battery including the solar's and converter's, and the previous frame to battery neg wire.

This can affect the length of the various neg wires and how you do your neg buss bar if any. So make the decision to go with a Trimetric (or Victron) before you get too far along.

[LipschitzWrath]

UPDATE:

Got my solar system installed yesterday. Waiting for the other panel to be delivered tomorrow. So far, seems to be working good, except for the fact that it was showing output in the middle of the night.

I think the problem there is I forgot to switch off the converter.

I'm going to play around with it more tonight, but so far I am excited.

The install was pretty **** easy. I used the fridge vent to get the wires from the roof to the wire chase.

[LipschitzWrath]

allen8106 wrote:
I've actually done an energy audit of my 5ver using a battery monitor and my refrigerator pulls .5 amps, radio in the off condition pulls .2 amps, LP Detector is so small it read zero.

Cool, I wonder what mine uses.

Even at 0.7A, that's still 17Ah per day. Limiting myself to 50% DoD on a 210Ah battery bank, that means about 6 days. 2 weeks is obviously too much.

Solar should fit my needs nicely.