Need the solar/power pros to weigh in

dreadlocks

Well-known member
There are cheaper SOC monitors than Victron, you dont have to invest in that high end of a unit.. but its got alot of really nice features that do make it worth that much, especially if you stay within the Victron Ecosystem.
The shunt is my Kill-O-Watt, I just turn everything off but the one thing I want to measure the power consumption on.. it shows me how many watts is being used, and I can do long runs over several hours/days and then average the total consumption.
 

TantoTrailers

Well-known member
I’ll do a bit more digging on that. I put together my controller box and got to a bit of testing. I’ll post up the detailed pics of that when I get time. I got the Bluetooth adapter so I could monitor things on the Renogy App. I think I need to run a battery down to see how well this charges and how much power my panels are producing as my batteries are topped off and both my 70w and 120w panel were only showing about 20 watts in the app. Excited to learn more about all of this and find my sweet spot! Thanks again for the input.

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120w
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70w
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TantoTrailers

Well-known member
I ran my kayak sonar battery down until the headunit shut off yesterday. It’s a 12Ah 12v Neptune battery for the sonar. When I hooked up the battery to the controller without the panel it read at under 20% capacity. I used my “120w” panel for an hour. It generated 4Ah and reached a max of 62w in the app. I’m going to buy an Aims Power 120w since someone already did the homework on testing several of the budget brand panels available on Amazon.

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Photobug

Well-known member
I don't know that your test gave you any more info other than your panel and controller can recharge a 12ah battery in a day. A 12ah battery would likely keep a fridge less than a day, you need to run down a larger battery to test the true capacity of your solar system.

You could also try running something off of the 12 ah battery while charging it so the solar has to provide power to the load you are running as well as recharge the battery to get a better idea of your solar capacity. I look forward to your tests with the 120w panel.
 

dreadlocks

Well-known member
a 12ah battery wouldn't run my fridge and base loads for more than ~6h, thought you said you had a 100AH?
 

TantoTrailers

Well-known member
The 12Ah battery test was just to see how well the panel and controller work as well as checking out the stats in the app. I wanted to see how many watts were registering in the system coming off the panel. It was bluebird sky with about 65-70 degree temps. This was not intended to be a true test of my end environment. Im still waiting for my watt meter to see how much draw my current electronics have on my battery. Im wondering if the 62 watts is an accurate meausurement of the power of this panel. I need a few other 120w models to compare I suppose. Anyone know how accurate the controller stats for the panel wattage would be?
 

dwh

Tail-End Charlie
The panel will only produce what the battery can accept.


Not knowing how deeply you've discharged that battery, or how many times you've done it, I can only guess.

Taking a 12ah lead-acid down to the point where some electronic device shuts off...well I would guess that's going to be somewhere below 50% charge on the battery. So, recharging it should have taken somewhat more than 6ah. But your test showed only 4ah to get back to full. That would seem to indicate a significant capacity loss, which would normally indicate a worn out battery.

In which case it wouldn't surprise me to also see the battery resistance choking down the solar output to 60w.

I would say try it again with a battery that can actually suck up some real power. Or put an extra load on it while charging - say a small inverter powering a laptop - that way you can pull all the solar is capable of producing to find out exactly what it is capable of producing.
 

dwh

Tail-End Charlie
Also, voltage doesn't tell you if a lead-acid battery is full, it only tells you what the voltage is. With a lead-acid, you have to get the voltage up and let it sit and absorb until it won't absorb any more.

Since the solar controller only knows what the voltage started as, what the voltage is now, and how many amp*hours it supplied and at what rate...but doesn't know how big the battery is...the best it can do is take an educated guess as to whether the battery is actually full.
 

TantoTrailers

Well-known member
I posted the 1 hour stats for the battery recharge which was the 4ah. I let the system run the rest of the day not paying attention to time and the controller ended in float mode with 9ah supplied before I unplugged it. I will try out the inverter test later this week when I get some time thank you for that suggestion. Still waiting on my watt meter that I ordered mid week from a supplier 20 miles from home...
 

TantoTrailers

Well-known member
Alright I finally received my watt meter and hooked it up between the battery and my fuse panel.

With nothing on except for the LEDs behind the USB outlets and the volt meter output on my dash the meter was showing 0.0 watts of usage as I hoped.

With my rear galley light on full blast, my two interior lights on, and with the MaxxFan running at top speed (10) I was pulling 50.8 watts and 3.8 amps. I never run my equioment this way.

With just the fan running at level 3 (3rd from lowest) which is how the camper runs 99% of the time I was pulling 2.7 watts and 0.21 amps.

With the fan at the same speed, my rear galley light at its lowest setting (the way I use it) and 1 interior light on I was pulling 5.1 watts 0.4 amps.

My guess is that my current normal consumption is somewhere between the second 2 tests.

The fridge I decided to purchase consumes about 45w of power when running. I purchased the thermal cover for it to help ot stay cool when its hot out. I do not have the fridge yet to see how much it actually pulls.

My plan is to have 2 of the 120w Aims Power solar panels hooked up to the Renogy MPPT controlled at all times when at camp. Im assuming the Aims Power panels will be better than the EcoWorthy panels but thats yet to be tested. Panel and fridge in the mail!

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TantoTrailers

Well-known member
Need some help here....series or parallel for my 2 panels going into the MPPT? Reading this it sounds like series is the way to go. My wire runs are short, around 10 feet, can I get away with 18g lamp cord? Seems that’s basically what is used In the 2 panels I already bought for testing.

 

dreadlocks

Well-known member
Series until you approach the high voltage limitations of your MPPT, then parallel until you reach the current limitations of your MPPT.. for various reasons.

18awg is a bit skimpy IMO..
 

luthj

Engineer In Residence
For panels in series, you are just losing output with the wire drop. So at the panels output (say 8A?) you can work out the voltage drop and power loss. If running in parallel you will double the current (double the wiring losses). But in addition you run the risk of the panels voltage minus the wiring drop, being too low to properly charge your battery.

On the battery to controller side you want less than 2%, ideally 1% voltage drop. Otherwise the battery will not charge very quickly, as the controller needs to see the true battery voltage.
 
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TantoTrailers

Well-known member
For panels in series, you are just loosing output with the wire drop. So at the panels output (say 8A?) you can work out the voltage drop and power loss. If running in parallel you will double the current (double the wiring losses). But in addition you run the risk of the panels voltage minus the wiring drop, being too low to properly charge your battery.

On the battery to controller side you want less than 2%, ideally 1% voltage drop. Otherwise the battery will not charge very quickly, as the controller needs to see the true battery voltage.
I'm an electrical newbie (as well as a newbie to the whole camper/overlanding thing imo) so bare with me, but is there an easy way to measure voltage drop with what I already have? I have a good multimeter as well.
 
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