Need help with Solar setup

The friendliest place on the web for anyone with an RV or an interest in RVing!
If you have answers, please help by responding to the unanswered posts.
See posts with no answers
C

Charchlo

Active member
Joined
Sep 8, 2014
Posts
26
Hey guys and gals, I have to admit all this solar stuff kind of gives me a headache. I have done a lot of reading and thought I configured my system appropriate to my needs but I'm now in doubt. I have a 96 Coachmen Santara 302SA

Here is my setup:
4 100 watt panels
4 225 AH 6V batteries
MPPT Solar Charge Controller
1500 watt Pure Sine Wave inverter

For now I have the inverter plugged into the shore power until I figure out the best way to tie in. (Help here would also be appreciated!)

My charge controller has a software interface and after finally getting everything connected, all looked good. I turned on everything I would be using during the peak sun hours and the inverter was reading about 400w and the charger was keeping everything running with no battery discharge. So at this point all seemed good. I checked the batteries before going to bed and all was good, turned everything off except for two Fantastic Vent fans on low (about 1AH each). Woke up around 2 am with my inverter alarm going off and it was indicating that my batteries were low.

So my question is this: How could just two fans deplete my battery bank in such a short time? I do have a a few parasitic devices but again nominal stuff here and do plan on phasing them out. Any help or thoughts would be appreciated. Thanks
 
Short answer is, the two fans couldn't run your batteries down overnight, unless the batteries were low to begin with or they were damaged. You said the batteries checked good before you went to bed, but do you know their actual state of charge (SOC)? If you were relying on a simple volt meter to determine that, what did it read? Volt meters alone are very poor indicators of a battery-bank's SOC - especially when there's any charging going on. Battery monitors are far more accurate.

Is your solar system the only charging source for your battery-bank? If it is, and your batteries were low to begin with, it could take a looooong time for solar alone to charge them. What kind of wiring did you use? You should use as thick a gauge wire as practical from the panels to the charge controller, and keep the wire run as short as practical. Your inveter and charge controller should be mounted as close to the battery-bank as possible, and you should run 4 gauge wire or thicker from the inverter to the batteries, and from the charge controller to the batteries.

Kev
 
Is your inverter wired into the 120 side?

What happened to me was the converter saw 120 volts from the inverter and was charging the batteries. It set up a cycle where the current was running from the batteries to the inverter to the converter and back to the batteries with all the loss involved. They way I cured it was a switch to turn off the the converter.
 
Thanks for the reply Kevin, these are brand new batteries and were tested at the store. So they were fully charged to begin with. Good idea on getting a battery monitor, all I have is a multimeter. I ran 10awg from pv to charger and 8awg from charger to batteries ( 8 was the largest size the controller would take) and 2awg for all the other connections between batteries (wired in series and parallel) and Inverter. All components are less than a two feet away from each other. My charge controller does have output for load, but I couldn't figure out how to use that.

 
Thanks for your reply halfwright, I do have the inverter plugged into shore power so it is feeding the 120 side, but all the dc connections in the old battery compartment are not connected to anything at the moment, so I don't think that could be happening. But I sure could be wrong, lol, still trying to figure this all out.
 
The converter is a good possibility as well as the fridge or water heater on 120v. Remember that a inverter uses power even when it isn't powering anything, some use quite a bit too. A big inverter at idle can use more power than a small one running our TV and satellite. You might consider smaller if 400w is all you will be using.

So your system looks balanced enough. What was the voltage while you were running the inverter during the day? What mode was it in at that point? Did the batteries make it through the cycles and were in float? Something is amiss and it's in the details.
 
Charchlo said:
Thanks for your reply halfwright, I do have the inverter plugged into shore power so it is feeding the 120 side, but all the dc connections in the old battery compartment are not connected to anything at the moment, so I don't think that could be happening. But I sure could be wrong, lol, still trying to figure this all out.
Click to expand...

How are the batteries connected to the rig to supply 12v power for the lights and such?  If the batteries are not connected then the converter is supplying the 12v for the rig.
 
I would also recommend Googling "Jack Mayer" and "Handy Bob" to get a pretty good education on solar power for RV's. Jack's systems are a bit more "top of the line" stuff and Handy Bob has a lot of baggage to read through, but is pretty straight forward on solar systems.
 
Charchlo said:
Hey guys and gals, I have to admit all this solar stuff kind of gives me a headache. I have done a lot of reading and thought I configured my system appropriate to my needs but I'm now in doubt. I have a 96 Coachmen Santara 302SA

Here is my setup:
4 100 watt panels
4 225 AH 6V batteries
MPPT Solar Charge Controller
1500 watt Pure Sine Wave inverter

For now I have the inverter plugged into the shore power until I figure out the best way to tie in. (Help here would also be appreciated!)

My charge controller has a software interface and after finally getting everything connected, all looked good. I turned on everything I would be using during the peak sun hours and the inverter was reading about 400w and the charger was keeping everything running with no battery discharge. So at this point all seemed good. I checked the batteries before going to bed and all was good, turned everything off except for two Fantastic Vent fans on low (about 1AH each). Woke up around 2 am with my inverter alarm going off and it was indicating that my batteries were low.

So my question is this: How could just two fans deplete my battery bank in such a short time? I do have a a few parasitic devices but again nominal stuff here and do plan on phasing them out. Any help or thoughts would be appreciated. Thanks
Click to expand...

I am not sure I can help, but I am confused by some of your statements.  When you say you "have the inverter plugged into shore power", do you mean that you have the shore power cord plugged into the inverter?

When your "inverter was reading about 400 watts and the charger was keeping everything running with no battery discharge", that would indicate to me that you were drawing 400 watts from your batteries, and when you say "charger" do you mean the charge controller for the solar, or do you have a separate charger?

 
Thanks for all the replies! Thought I had done enough research but apparently not. I am running an extension cord from the inverter to the shore power line so it is running thru the converter, not very efficient I know. The inverter was using 100w on it's own. I was planning to replace the two way fridge (which I do not have running at this time) with a high efficiency residential unit but wanted to make sure I had the ability to run it first hence this testing. I checked the voltage every hour during the day and it corresponded with what my charge controller was telling me, about 5.8 to 5.9 volts. So i had assumed that they were in float.

I had assumed the bigger the better with inverters, but I guess this may not be true? What I'm thinking now is to run a line from the batteries to the 12v connections in the old battery compartment to run the lights and such, and use the inverter for just my various electronics and the new fridge. Does that make any sense.
 
A six volt battery that shows 5.8 to 5.9 volts is essentially dead. You need to shut the converter off. The inverter should not use 100 watts with no load, that sounds like the amount of power your converter is drawing trying to charge the batteries that the converter drawing power from.
 
I'm thinking you may have your 6 volt batteries wired together incorrectly. Two of the batteries should be wired in series to make one 12 volt battery-bank, (X2 since you have four 6 volt batteries), then both 12 volt battery-banks should be wired in parallel with the other to make one larger 12 volt battery. If your charge controller is indicating less than 6 volts, it's only measuring the voltage of one 6 volt battery, or several of them wired in parallel. It should be indicating something in the area of 12 volts.

Kev
 
Nope first think I checked, batteries are wired correctly. When I put the positive lead on one battery and the negative on the other battery it does give me a reading of 11.5. Sorry I wasn't clear on that. I have shut the inverter off until I figure this out. On my rig there is no on off for the converter that I can tell. The main power box has just the main breaker and then breakers for the misc. 120 circuits.
 
Wow that's not good. I moved the connections from the charger controller on to the same series of batteries and it has already jumped up to 12.2 in five minutes, so maybe that was that part of the equation? Learning as I go ;)
 
You cannot have the inverter going through the converter through the shore power cord. It means you are trying to charge the batteries using battery power. This is not good.
Find the converter wire/breaker and disconnect. Mine was pigtailed with an outlet breaker. Run fridge and water heater on propane.
Soumds like you have the solar controller attached correctly now.
 
byrogie said:
You cannot have the inverter going through the converter through the shore power cord. It means you are trying to charge the batteries using battery power. This is not good.
Find the converter wire/breaker and disconnect. Mine was pigtailed with an outlet breaker. Run fridge and water heater on propane.
Soumds like you have the solar controller attached correctly now.
Click to expand...

This is also what I think is happening too.
Battery bank at 12.2 is considered 50%soc (state of charge). Never go below that if at all possible!
Now with my Lithiums I can go to 20%soc.
 
Thanks byrogie, got a rainy day here so not much charging happening. Although I did have the inverter plugged into shore power, the converter was not trying to charge the batteries because they weren't connected at all. I need to come up with a plan to power the 12 volt systems (lights, water pump etc...) and the 120 outlets without going thru the converter. Got some time today so I will be doing some research on that. BTW I'm plugged into my household power for now until I figure this out.
 
You must log in or register to reply here.

Latest posts

Members online

Total: 654 (members: 32, guests: 622)

Forum statistics

Threads
131,914
Posts
1,387,295
Members
137,666
Latest member
nativoacai
Back
Top Bottom