12v lithium battery thoughts

[John in Santa Cruz]

panels are apparently rated based on a theoretical sun. The peak output I've seen from mine, 300W, is 20% lower than the rated output of 360W.

and yes, at 5000 feet you are above something like 15-20% of the atmosphere. In the SFBA, almost entirely at sea level, you're also quite close to the Pacific Ocean which means in many locations you're in the influence of the marine layer, very moist air, this also has an attenuating effect.

[CarlD]

You also have to consider the temperature of the panel. Output drops as the temperature rises. Also, some technologies perform better than others at higher temperatures.

[Jane P.]

Originally Posted by Jane P.

I believe you cannot wire your solar panels in parallel if you use a DC-DC charger with MPPT built-in.

But the technology is changing and expanding all the time.

LET ME CORRECT THE ABOVE QUOTE:

This is regarding the Renogy DC-DC Charger with MPPT.
The max solar input for this device is 25 - 30 AMPS. To get around this limitation, you’ll need to connect your rooftop solar panels in parallel. I mistakenly wrote in series. So very sorry …


I seriously considered getting this product, but in the process of researching it, came across Will Prouse’s YouTube review. Because I have three 100w 12V panels, I needed to wire them in series. Consequently, product would not work for me and I opted to purchase a RICH SOLAR 40 Amp MPPT Solar Charge Controller. BTW, I am very happy with this product.

Will discusses limitations with solar input at 4:28 In the video.

https://m.youtube.com/watch?v=JtAUrS4zNSA

Here is a link describing how to integrate the Renogy DC - DC Charger with MPPT into your solar system.
https://www.mobile-solarpower.com/si...-charging.html

[Jane P.]

Originally Posted by John in Santa Cruz

a DC DC charger *is* a form of MPPT device, but are you saying someone makes a DC DC thats also a solar charger ?

re MPPT controllers, the one I got for my solar panels can take up to 100V of max PV, so two ~40 volt PV panels like the one I have could be run in series, OR in parallel. Except I think I'd exceed this controller's power ratings, which is max 440W PV (my panel is 360W)... I'd have to upgrade to the 100/50.

@John Thanks for your followup question. It forced me to recheck my notes & realize a huge error with that post.

Yes, Renogy has a product that combines an MPPT Solar controller with a DC-DC On-Board Battery Charger.

Check out the links in my #43 post for more info.

[chrisblessing]

Originally Posted by MrJohn

@chrisblessing & @parmm



We have a 13' Scamp we want to put 100Ah into.



Did you use the same 12g/14g wire from the battery compartment back to the converter? Or did you re-run thicker guage wire?



Also, did you swap out the delivered scamp controller with the Progressive Dynamics 9130LV?



Thanks for your help!

I mounted my battery, charge controller, invertor and everything else under the front, passenger-side bunk. It is mostly isolated from the house with no charging from the converter. When I am connected to shore power I have a 5amp LiFePo4 permanently installed to charge the battery. I pulled 10 gauge wire for the furnace and 12 volt-only compressor fridge. To date it has worked flawlessly.

[John in Santa Cruz]

Originally Posted by chrisblessing

I mounted my battery, charge controller, invertor and everything else under the front, passenger-side bunk. It is mostly isolated from the house with no charging from the converter. When I am connected to shore power I have a 5amp LiFePo4 permanently installed to charge the battery. I pulled 10 gauge wire for the furnace and 12 volt-only compressor fridge. To date it has worked flawlessly.

so what does the converter run?

even the *big* compressor frdige I put in my Escape 21 only uses 5 amps max, so 14 or even 16 gauge would have been fine. I left the original DC wiring from the converter fuse panel to the original absorption fridge, and its running the Norcold N2175 just fine. I swapped out the WFCO power converter core for a PD4655LI, which will charge my batts at 50A (and replaced the battery wires with AWG 4).

[chrisblessing]

The converter allows for 110v devices via the house plug, powers the LiFePo4 charger and the one florescent lamp above the sink. I also carry a small space heater.

[John in Santa Cruz]

In RV terms, a Converter takes 120VAC campground power and turns it into 12V operational and charging power, while an inverter takes 12VDC battery power and generates 120VAC

2000W Renolgy Inverter,

[John in Santa Cruz]

Originally Posted by John in Santa Cruz

In RV terms, a Converter takes 120VAC campground power and turns it into 12V operational and charging power, while an inverter takes 12VDC battery power and generates 120VAC

2000W Renolgy Inverter,..

currently that inverter just goes to this RED outlet,

[John in Santa Cruz]

but, I;m thinking of wiring a subpanel and transfer switch so it can run everything in the camper except the rooftop air conditoner. and of course the converter that is the battery charger

[Raspy]

I'm starting to get some real practical use form my AC running from my house batteries. I have 480 AH of Expion lithium batteries, 660 watts of solar and an 8,000 BTU AC that draws about 600 watts when actually cooling.

The most practical use pattern is being able to run the AC day after day, and not just one day while depleting the batteries, and then not being able to do it the next day.

When first turning on the AC, the trailer is hot inside and the AC compressor runs steady for about a half hour. Then it begins to cycle the compressor and run it about 1/2 of the time. This means the real energy draw is about 50-60% of 600 watts, over time, or about 360 watts average.

By this time, the air in the trailer is cooler inside, but the hard parts, like walls and counter and other objects are still warm. So, the AC must keep working. After about 1 1/2 hours, everything it pretty cool and the AC can be turned off for a while, or the thermostat will cycle it clear off and not even run the fan. At night, this might translate into about 20% of battery capacity. During he day, with an average of about 300-360 watts coming in from the solar, over a window of about 6 hours, the solar will roughly match the energy used by the AC in about 1 1/5 hours. This is not enough to keep the trailer cool inside for 24 hours, but it is certainly enough to cool it after a long day of driving, or take the edge off the heat for a longer time if the thermostat is set a bit higher.

It is very nice to arrive at a boondocking spot, late in the day, when the trailer is hot inside, and turn on the AC. Or to stop for a lunch break, and maybe a nap, and turn on the AC. All from the batteries.

The primary goal of this arrangement was not to run the AC, but I can see it is becoming practical in some situations and I still have room for about 300 more watts of solar.

We were recently in Alabama and had shore tie power. But during the 2,400 miles home, with stops in Texas, Arizona and southern Nevada, we never had hookups. All boondocking. And we got some good use form the AC which made it much more comfortable. If someone started out with AC run from solar in mind, they could do much better than I have and get much greater performance.