Solar, Charging, Inverters, etc.

[ScottK]

As the weather is warming up, the days are letting longer and the snow is melting away, my mind is on getting the camper ready for the summer road trips! I am just in the planning phase to add 300watts of solar, upgrading the batteries, and adding an inverter to the camper. I have questions on inverters and how the charging system works. I know just enough about the electrical side of things to be dangerous! I know there are several of you that are very savvy with electrical.

I will be building the panels myself much like Norm did here. His build is where I got the idea from and I just love it! Right up my alley! I'll also be adding batteries like Frank did here. (I'm stealing all your great ideas boys) I'll be sure to keep you updated as I move along with the project.

Solar Panels (2):

• (40) 6"x6" 4w cells per panel
• Finished panel size ~ 66" x 28"
• 160 watts / 20 volts / 8 amps per panel

Batteries:

• (4) 6 volt Golf Cart Batteries
• 400+ Amp Hours

Cabling:

• I plan to use heavy gauge cables and good distribution to minimize the voltage drop.

Charge Controller for Solar Panels:

• ??
• What happens when I am plugged into shore power with my converter/charger (upgraded last year) charging the batteries AND my solar panels are also charging the batteries through their own charge controller? Will that harm anything to have 2 charging sources? I am inclined to think that multiple charging sources will just increase the speed (amps?) in which the batteries charge. But that notion falls apart when I think about the different phases (bulk, float, etc) the chargers go through. This is where lack my electrical knowledge comes really through obviously.

Inverter:

• ??
• I am thinking maybe a 1000 watt unit since so we can use the coffee pot and microwave a bit. This in addition to small items like laptop and camera battery chargers, etc. I know inverters should be sized properly for maximum efficiency and some people use 2 inverters (1 small & 1 big), but i'm not sure if a 1000 watt unit is a "happy medium" or if that would be considered "large and inefficient" for anything but the microwave or coffee pot.

What else should I be thinking about? Thanks for helping get my plan in line.

[JohnB]

Hi Scott

I have not yet ventured into the solar panel arena "yet". Too many other mods on the want list....

Thinking about your post I would be concerned about when you plug into shore power. You may want a disconnect switch on the charge line from the converter to the battery. Let the solar charge the battery and let the converter run the camper.

This would for sure eliminate any back feed concerns. The charge algorithm between the 2 controllers may be different like your where stating. And another reason is you may end up overloading the wiring unless it would be size for full load amps from both controllers on full output.

If the battery bank was 100% state of charge then both controllers may sense that and go into float mode with is fine. On the other hand, if the battery bank is way down then both may sense the resistance thru the battery and both kick into boost and that then creates a very high amperage situation. The battery may not like this either. And then there is the states of charge inbetween.

I do not know 100% if what I'm stating is accurate, more thinking out load but I do know before I would attempt it I would have to for sure contact each controller manufacture and explain the concern and see if their system can handle it.

For sure post away with pics of you journey. This is good stuff to think thru, learn and see.

John

[ScottK]

I'll talk with the Progressive Dynamics folks this week and see what they say. I did get some advise on Friday from solar rv a dealer/installer that basically said they are two independent systems and there is nothing to worry about. Well that may be true but I would like to understand more about why that is the case before I move forward. Best I talk with the manufactures...

I think the reality is, that most of the solar controllers aren't necessarily designed with RV's in mind, so they aren't considering the notion that there maybe another charging source. However there is one solar charge controller, that I have found, that does (Helitrope HBV-22B) and they say:

• A "Dry Camp" / "Shore Power" Selector Switch
  (When dry camping, you need all the solar power you can get. So, when this switch is set to "Dry Camp", the controller's charge set point is 14.3 to 14.4 volts. When you are plugged into shore power and have your inverter/charger or converter charging your batteries, you don't want your batteries to be held at that high of a voltage. So, when this switch is set to "Shore Power, the controller's charge set point is lowered to 13.2 volts. It will in essence be in a standby mode ready to spring into action should the shore power drop out.)

This sheds some light on the matter. I'll update as the project progresses through the spring.

[JohnB]

Originally Posted by ScottK

I'll talk with the Progressive Dynamics folks this week and see what they say. I did get some advise on Friday from solar rv a dealer/installer that basically said they are two independent systems and there is nothing to worry about. Well that may be true but I would like to understand more about why that is the case before I move forward. Best I talk with the manufactures...

I think the reality is, that most of the solar controllers aren't necessarily designed with RV's in mind, so they aren't considering the notion that there maybe another charging source. However there is one solar charge controller, that I have found, that does (Helitrope HBV-22B) and they say:

• A "Dry Camp" / "Shore Power" Selector Switch
  (When dry camping, you need all the solar power you can get. So, when this switch is set to "Dry Camp", the controller's charge set point is 14.3 to 14.4 volts. When you are plugged into shore power and have your inverter/charger or converter charging your batteries, you don't want your batteries to be held at that high of a voltage. So, when this switch is set to "Shore Power, the controller's charge set point is lowered to 13.2 volts. It will in essence be in a standby mode ready to spring into action should the shore power drop out.)

This sheds some light on the matter. I'll update as the project progresses through the spring.

Hi Scott

I will be real interested on what PD has to say. Please post back if you can.

On this thought

I did get some advise on Friday from solar rv a dealer/installer that basically said they are two independent systems and there is nothing to worry about.

That generic statement may be just a little too generic. One may run out of wire capacity depending on where the solar and on board converter connects into the system.

Interesting on the Dry camp/shore power switch from 14.4 to 13.25 volts. One is boost mode the other is float charge. I have not dug into the solar charging enough but putting 14.4 into the battery for long periods will gas off the battery especially if the battery really does not need it and is above 90% state of charge. What "might" be more help full is the solar runs at 13.25 float mode until the draw on the system kicks in and then go to a higher amp supply mode at 13.6 volts. Bascailly what the PD converter is doing and that it does so well. Only thinking out load here on this one.

I can see I really have to research this one when I get to the solar option upgrade....

Thanks for the info

John

[jhorne05]

Hello
Renogy solar has systems specific to rv, tt , home , business. I understand this a older blog . Considering 400 watt panels 30amp Lcd controler, with 2000wat inverter. Batteries are dual 8d's, 530ah. 12volt system all to be boondock capeable (12volt/gas furnace, 2way refrigerator 120volt or 12volt/gas, 2way hot water heater 120volt or 12volt/gas, 12volt water pump, 12volt/gas stove)
This would allow all systems to function all be it individually , but can cook and take a shower the Mrs and I. So far on the information I have received I will install a dual battery switch between solar controler and batteries , a dual battery switch between the converter and batterie allowing shore power or generator to charge the batteries, or use solar to charge the batteries.
Hope this helps with big picture of your question regarding dualing charge systems.

[mainah]

The controllers pretty much now PWM (pulse width modulation) controllers they sense battery voltage and if the panels are not need to charge a full battery they basically short circuit the panels. The voltage is pulsed on and off during the charge cycle the more often the pulse the greater the charge rate. So if the charger is on line they just think the battery is charged.