750W Solar install on TT

RoyB wrote:
I haven't checked the specs on the 250WATT Panels but I know the 120WATT PANELS produce around 5-6AMPS DC current during high sun. With this in mind I am assuming the 250WATT PANELS will double that. Having three in parallel would give you a min of 36AMPS DC current to use for charging batteries.

My charging setup will need to produce 14.4VDC @ around 20AMPS per battery if I want the batteries to re-charge within a 3-hour time frame. Of course you will have high sun for a good 5-6 hours or so a day so that will be enough to get two T105s to float mode in the one day sun I would think.

Glad you are realizing that SOLAR is not the only answer and you really have to have a generator setup if you want to totally rely on keeping your batteries at their minimum of 90% charge state when you need to use them.

I am just now in SOLAR PANEL MODE thinking after camping off the power grids for the past few years with my 255AHs battery setup. I know exactly what to expect and when I need to do re-charge my batteries. They are still going good since being installed in 2008. I will most likely start out with two 120WATT PANELS on my POPUP ROOF and maybe add another 250WATT PANEL later on. That is about all the room I have on my POPUP ROOF.

The only real thing I have learned for my style of camping off the power grid is I MUST start each evening with a good 90% charge state if I want to make it through the night. This all then gets re-charged again starting at 8AM the next morning. I may also have to run my generator for around one hour to get over the smart mode high current period of BOOST MODE. Then I am hoping the SOLAR PANELS will take over and get me re-charged to at least to the 90% charge before i start using the batteries again that evening.

This requires a good monitor system to keep me in the know where my approximate battery Bank charge state is when nearing the loss of high sun. I can always go back to generator when allowed to run my generator at the camp site to get the battery bank where it needs to be at. I will not want to start my evening run off the batteries unless they are are at least at the 90% charge state.

These are my baby steps...

Roy ken

have you check out solar bobs info. he runs off panels with batteries and NO generator..

http://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/

might be worth a look

Looks like a pretty nice setup, but seems like that system is really going to be limited by the 2 batteries.

Have you looked at what you want to run and how many amp hrs you need? Running the AC is not really an option on 2 batteries. So, that leaves you the fridge, water heater, microwave, tv, and 110V outlets for stuff like a hairdryer, toaster, coffee pot.

Your diagram shows the entire electical panel being fed from the inverter. The other option would be a sub-panel powering only select circuits.

The easiest way to save on a solar setup is reduce your load. The fridge and water heater would run for a couple weeks or more on propane without a refill.

Just playing devil's advocate here, but 2800 watt inverter is a lot of power for a hybrid trailer. Depending on what you need to run, you might be able to go down to 1500-2000 watts.

And same thing on the pannels - 750 watts of panels is going to take up a lot of real estate (and be fairly heavy) for the roof of a 21ft trailer (or you have to carry them/set them up if they are portable).
And if you have them in series, you need to mount them in a way that avoids any shadows or you will loose a lot of output.

Food for thought, but if you downsize the system to power the basics, you could put the savings into a good generator. Even if you had to fire it up to run the microwave or coffee pot, it would still only run a short time each day. Or maybe even spring for a pair of 2000's that you can parallel. Run one as needed, and run both if you need AC.

Or if you stick with the current setup, a couple more batteries would really help maximize its potential.

hybridized wrote:
My (limited) understanding is that the MPPT will efficiently step to send maximum amps to 12V bank.

A quality MPPT controler will do three things that are all good.

1)Allow a higher input voltage allowing panels to be in series. This reduces the power lost in what is typically in an RV the longest wire run; and allows for much smaller gauge wire.

2)Not easily understood, and I'm to tired to tonight to try to put it into some analogy. Basically, as the sun changes, and the battery bank voltage changes, the MPPT gets the most energy from the panels into the battery bank as these conditions change.

A PWM controller simply LIMITS the both the solar panel output and battery bank input to regulate the battery voltage; while the MPPT controller maximizes the transfer of solar production into a discharged battery bank.

3)A good MPPT controller will also have multi-stage battery charging that is programmable for the batteries that are attached to the system. A really good one will also have a temperature sensor to attach to the batteries.

The only downside to a quality MPPT controller is cost. But, how much is it worth to get the most out of the monies spent for both the solar and the storage?

OutbackPower
More money maybe, but really take a look to see what you get.

Hope this helps.

hybridized wrote:
... may notice the error:

Your drawing appears to show a 50 amp service, so the existing converter input needs a method to have its 120ac OFF when the inverter is on. Otherwise, you are wasting power by trying to create a perpetual motion/energy type of system.

I would wire the panels in series if you can. In a solar installation in an RV, this is typically a fairly long wire run. The higher series voltage will allow for significantly smaller gauge wire without power loss.

I don't see the need for fuses on the solar side.

In my opinion, MPPT charge controllers are the way to go with solar.

In my opinion, your battery bank should be fused and switched. And I forget, but there is a general consensus of which of them should be first in the circuit.

In your drawing, you will lose charge current through the shunt. I recommend the MPPT connections directly to the battery bank.

Lastly, every connection creates a small bit of resistance. IF you ever increase your battery bank to more than two batteries, I recommend that the MPPT charge wires, are diagonally connected across the battery bank from the inverter wires.

Hope this helps.

Just for info on a sunny day I can get 19.2 amps out of my 250w conergy 250p panels in mppt. On the output fuse, you need 125% of the current rating going through them per NEC.

pugslyyy wrote:
It looks like you are prepared to invest quite a lot in getting the right setup.

If the obstacle to adding more storage is weight / space have you considered looking at Lithium Ion storage instead of lead acid?

You can fit a lot more storage capacity into a much smaller, lighter package that way.

If you do look at Lithium Ion, you will need to work with whomever you source them from to make sure that your hardware (particularly the MPPT) is set up correctly.

Great points, I never even considered Lithium Ion. I have purchased the 6V GCs already, I suppose LiIon will be phase 2 if I find the capacity lacking.

KJINTF wrote:


Why did you go MPPT? Vs PWM with panels in parallel?
That controller works great with 60voc input power - allows smaller easier to manage and lower cost wires from the array to the controller
What VOC do the panels produce?
Suggest you go a bit larger say 70 amp output fuse (and use a switchable breaker)
On good solar days you should easily see high 50amps from the PV array
(My little 550watt array easily produces 40+ amps and as you with only two 6Vdc GC batteries which work just fine for us)
I used switchable breakers for the array and load connections from / to the controller - makes it far easier to isolate the controller (it draws current from the battery when in long term storage, makes software upgrades easier, etc..
Suggest you hook up the voltage sense line and the Temp probe from the controller to the battery.
Plus the Ethernet and the serial data cable - you will need to setup the operational parameters via a computer
Strongly suggest you do not simply use the dip switches and set / forget the install
Any plans for the remote meter?

Panel ratings
Vmp: 29.8 volts
Imp: 8.39 amps
Voc: 36.9 volts
Isc: 9.09 amps

My (limited) understanding is that the MPPT will efficiently step to send maximum amps to 12V bank.

When you say 70A output fuse, do you mean in place of the 60A coming out of the controller?

What do you mean 'plans for the remote meter'?

I do plan on using voltage sense and temp probe.

Thanks for the tips on switchable breakers (they all are...the super-nice people at No AZ Wind and Sun set me up) and on not using the dip switches. Still figuring out the fine points of configuration and what/where I may need to isolate for maintenance, flexibility, etc.

Roy,
Stick 240w->250W on the roof, in sun, in the summer, and your batteries will be back to 90% by noon. They will be well over 90% by the end of the day. No generator needed.

I haven't checked the specs on the 250WATT Panels but I know the 120WATT PANELS produce around 5-6AMPS DC current during high sun. With this in mind I am assuming the 250WATT PANELS will double that. Having three in parallel would give you a min of 36AMPS DC current to use for charging batteries.

My charging setup will need to produce 14.4VDC @ around 20AMPS per battery if I want the batteries to re-charge within a 3-hour time frame. Of course you will have high sun for a good 5-6 hours or so a day so that will be enough to get two T105s to float mode in the one day sun I would think.

Glad you are realizing that SOLAR is not the only answer and you really have to have a generator setup if you want to totally rely on keeping your batteries at their minimum of 90% charge state when you need to use them.

I am just now in SOLAR PANEL MODE thinking after camping off the power grids for the past few years with my 255AHs battery setup. I know exactly what to expect and when I need to do re-charge my batteries. They are still going good since being installed in 2008. I will most likely start out with two 120WATT PANELS on my POPUP ROOF and maybe add another 250WATT PANEL later on. That is about all the room I have on my POPUP ROOF.

The only real thing I have learned for my style of camping off the power grid is I MUST start each evening with a good 90% charge state if I want to make it through the night. This all then gets re-charged again starting at 8AM the next morning. I may also have to run my generator for around one hour to get over the smart mode high current period of BOOST MODE. Then I am hoping the SOLAR PANELS will take over and get me re-charged to at least to the 90% charge before i start using the batteries again that evening.

This requires a good monitor system to keep me in the know where my approximate battery Bank charge state is when nearing the loss of high sun. I can always go back to generator when allowed to run my generator at the camp site to get the battery bank where it needs to be at. I will not want to start my evening run off the batteries unless they are are at least at the 90% charge state.

These are my baby steps...

Roy ken

Hi

I will limit my comments the MS MPPT 60

Why did you go MPPT? Vs PWM with panels in parallel?
That controller works great with 60voc input power - allows smaller easier to manage and lower cost wires from the array to the controller
What VOC do the panels produce?
Suggest you go a bit larger say 70 amp output fuse (and use a switchable breaker)
On good solar days you should easily see high 50amps from the PV array
(My little 550watt array easily produces 40+ amps and as you with only two 6Vdc GC batteries which work just fine for us)
I used switchable breakers for the array and load connections from / to the controller - makes it far easier to isolate the controller (it draws current from the battery when in long term storage, makes software upgrades easier, etc..
Suggest you hook up the voltage sense line and the Temp probe from the controller to the battery.
Plus the Ethernet and the serial data cable - you will need to setup the operational parameters via a computer
Strongly suggest you do not simply use the dip switches and set / forget the install
Any plans for the remote meter?