13 replies to this topic

[Cayuse]

I've been through the calculators and read through lots of threads both on here and on Expedition Portal and would like to get some advice.

 

I have a 2002 Grandby with dual flooded group 31 batteries.  Lights have all been converted over to LED, just put in an Isotherm 65 fridge.  There will also be times that the furnace will run and eventually I will probably add a fantastic fan.

 

Typically I will move the vehicle every couple of days and can charge from the alternator but am thinking I'd like to add solar for those non-typical times.  I know that 200W is probably overkill but that what I am looking at since at some point I could see wanting to charge a laptop or something else.

 

Now the big question, why the huge variance in prices?  solarblvd is $460 for a 200W system and windynation is only $325, both with PWM controllers.  It seems like someone else was around $460 with an MPPT controller but I left that information at work :-(.  All of these are monocrystalline panels, is one vendor that much better than another?  Should I just shop price?

 

Hopefully someone can help a solar novice out.

[MarkBC]

There can be a huge difference in the price of panels depending on where they're manufactured, like, Chinese panels can be a lot less expensive. 

 

If you're trying to save money, why not consider polycrystalline panels?  Yes, they're less efficient, but not that much less. (I'm talking about polycrystalline -- not amorphous, which are still-lower efficiency)

[Cayuse]

Saving money is always a good thing.  I'm not opposed to spending more if the value is there.  I may even consider the solarblvd 240W system at around $640.  It is more a matter of figuring out if one vendor's panels and controllers are really better than another's.

[photohc]

May want to checkout http://amsolar.com. I have had good experience with them and they seem to do a lot of research on products for the RV/Camper user. I have no interest with them other than my experience in dealing with a MPPT controller and mounting brackets I purchased from them, both very good products. Goodluck. Harv

[Cayuse]

amsolar came back much higher than the others but it also included install.  I haven't heard back from them yet on a quote without install.

[The Next Adventures]

I got my panels and controller from soldonsun.com. With that being said most electronics you will want to charge are 12 volt. Install a USB charger and charge most items this way so you dont use the inverter. Then for your inverter don't go huge. A lot of people get 1000watt or more inverters that just suck unnecessary energy. 300 watts is plenty unless you want to power a giant blender.

[ntsqd]

I would suggest putting in a battery monitor first. Much easier to size your solar if you know what your actual use is.

[RC Pilot Jim]

Do you mean a watt meter? or is there a special type of battery monitor? If special do you have a recommendation and link?

[MarkBC]

Do you mean a watt meter? or is there a special type of battery monitor? If special do you have a recommendation and link?

 

To REALLY know how much power or energy you're using you need an inline amp-meter/watt-meter (though where to put it depends on how your system is wired).

I love the Watt's Up meter.

 

You can get a rough guesstimate of how many amps-hrs you're using (and so how much you need to add via solar) by just measuring the battery voltage (which is a lot easier and cheaper than measuring current flow or watts).  There are charts that estimate %-charged based on battery voltage.  So if you know how many amp-hrs your battery is supposed to provide when 100%-charged you could calculate how many amp-hrs you used based on how much the battery voltage drops in a day (for example).

That'll be a rough estimate because:

1. Batteries lose their amp-hr capacity as they age, so it'll be more accurate with newer batteries.
2. As a battery is being discharged (like, if a compressor fridge is running) it's apparent voltage and state-of-charge will be lower than it really is.
3. For a while after charging the state-of-charge -- as indicated by voltage -- will be higher than it really is.

Here's one example of state-of-charge vs voltage, though I've seen some charts vary from this:

[ntsqd]

The more expensive option is the Bogart Engineering TriMetric. It uses a precision shunt to measure watts in/out and does all of the calcs for you once you set it up. The setting it up was something that I thought was going to be painful and didn't do, just had it wired-in more or less limping along when I really read the instructions. Setting it up took about 10 mins and I should have done it from the start.