Solar / Batteries/ Controller

[PhilGrunder]

I am doing research on how to best upgrade or update my current RV system. My current setup
2 interstate 60 amp hour batteries
10 amp go power controller
2 100 watt solar panels
Norcold fridge works only on 12 volt power.

I want to get to a point where my fridge stays running all night without the E3 code. And the USB ports charge my phone.

What size battery or batteries do you recommend? What size controller should I go to, a 20 or 30 or 60amp. Do i need to add more solar?

[bikendan]

Moved thread from the Modifications and Updates section to the Electrical, Charging Systems and Solar sub-forum since the OP's questions are specific to that sub-forum.

[Aussieguy]

I have 200ah of lifepo4 (Lithium)
it will last about 2 days without a charge powering..... 12v fridge , furnace and other normal 12 volt stuff
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400-450 watts of solar should be a good start use a 30amp MPPT controller
600 -800w is better .... 50amp controller

if you going to pay for a controller work out best panels you might get on your roof (future upgrade)
buy controller for max panels you can put on roof so you don't have to keep buying new controllers

you might even be better to use 2 x controllers
my rear panels on roof 2x 370w residential size .... run a 50amp controller
the front panels ... if I ever put them on, 800w will need a 60 amp


controller manufacturers will specify max solar panels you can connect to a controller
quick math method is.... multiply charging voltage (14.4) by controller amps 50
14.4 x 50 = 720w of panels

My 740w of solar have worked well for me traveled to Northern Ohio down to Everglades

your results will vary depending where you camp... pick camping spots with afternoon shade if possible
my solar finished charging around 1:30 -2:00pm
HAVE NOT use converter or generator to charge the batteries since adding the solar

Again.... measure your roof and plan what panels you can put up there. May be better to remove old panels and controller and start anew!
you can re-use the old stuff for a ground panel or two.


solar will work while driving , stopped for lunch or camping

[Aussieguy]

Forgot...
my MPPT paid 85.00 for it off amazon
Batteries 400.00 Amazon 2x 100ah Elfhub
Both have BLUETOOTH so don't need a screen etc


If you are building a 12v system that does NOT use a big inverter the Amazon Budget stuff works

bought my panels locally through Facebook Market place
no shipping

[GoingNoWhereFast]

Lithium has dropped in price so much, I would recommend with that 12 volt frig a 300-400 Amp hour LiFePo battery. You can get one for under $1000 These days and it isn't as heavy or as big as your 2 lead acid batteries. A 400AH LiFePo battery will run your frig for 3days if you get caught in a rainstorm and no solar is available.


You can save your self a lot of headache and prayer just getting a small genney to recharge the batteries off. $300-$500 will get you an inverter generator that will run your A/C and charge the batteries and you don't need to spend the $1000 on solar panels, wiring, Controllers, Switches, fuses, and convertors. And still not have power when it rains for a few days or you park in the shade. Just my Opinion.

[tomkatb]

Understand the math.

When the sun goes down you have roughly 60 or so available ah.

A 100 watt panel in North America on its best day produces 25 ah of power to your battery.

Likely your usage is roughly 100 ah of battery per day.

It is likely day one you will run out of battery. No hope for day two. The math does not work.

Immediate solution is as much lithium as you can. 400 is what we have. With your solar it is likely you might make 5-6 days. No furnace or exhaust fan.

We can go four days on our 400 ah of battery. Then we charge with a 2200 watt generator. Typically we charge every other day. The DW likes to use the convection oven and sometimes the dryer.

More solar and a new solar controller might work well. I am not a solar fan.

We travel year round. So we purchased the SOK batteries. They have a built in monitor and heaters so they work down to 0 degrees. Others do not.

You need a battery monitor.

[JimM2109S]

Originally Posted by Aussieguy

Forgot...
my MPPT paid 85.00 for it off amazon
Batteries 400.00 Amazon 2x 100ah Elfhub
Both have BLUETOOTH so don't need a screen etc


If you are building a 12v system that does NOT use a big inverter the Amazon Budget stuff works

bought my panels locally through Facebook Market place
no shipping

Aussieguy, which model of Elfhub batteries do you have? With or without internal heater? I tried to send a PM but your inbox is full.

I've given up on my two Li batteries. I ran two independent tests on each and they are only providing appx 75Ah of power, this after a short two years of use. Time for a different brand.....

[Aussieguy]

Originally Posted by JimM2109S

Aussieguy, which model of Elfhub batteries do you have? With or without internal heater? I tried to send a PM but your inbox is full.

I've given up on my two Li batteries. I ran two independent tests on each and they are only providing appx 75Ah of power, this after a short two years of use. Time for a different brand.....

No heater... not/never/noway going anywhere near places that get cold enough to need one..

Elfhub now selling for $175 with Bluetooth


I have NEVER done a full on capacity test other than to see how long it will power the fridge.
I don't want to be the guy that is constantly looking for every little lost amp hour ...

am Using the OVERKILL solar app
not using the generic app they have listed to use.

Only setting I modified was to allow balancer to work while charging or discharging

whether these last 5 or 10 years or more......... is not an issue
they have already allowed me to boondock/travel worry free enough times that I am happy with them.

They do their job without any issues ... use to be anal about checking the capacity each morning , now I just look once in a while.
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before you lash out and buy another "brand"
Do the batteries perform the duty you want from them... ?

my criteria is simple I want ABOUT 2 to 3 days of 12v power
really don't care if I am getting the stated amp hours

I have all the generators , converters and solar to replenish the batteries in any circumstances.


I have re-read the post you have on the your battery
unless you want to buy more expensive testing equipment your reliance on a shunt is kinda prone to error

Have you got a DC current clamp on multimeter that can independently confirm your setup/readings



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Inbox now empty

[tomkatb]

Due to a bms failure I purchased the Victron 15 amp battery charger.

It is one of the few that can wake a sleeping lithium battery. Lots of other features. I am a car guy. My 40 year old garage battery charger was ready for the trash anyway.

All of the battery monitors can be a bit goofy. Your batteries might be ok as Aussie guy said. There are all kinds of set up procedures for them that are often ignored.

Be careful! Mixing solar panels and batteries of different brands or generations can cause issues. Ask. Be specific.