Solar replacement and 2 agm batteries

[Deancamp]

I initially thought I was going to convert to lithium batteries when replacing my solar panel but after continued research I have decided to replace my no longer working 160w solar panel with 200w. I am also installing 2 90ah amg batteries. I have my batteries and I am looking at solar panels. I'm not looking for the best panel but more of a good quality panel for the money. I have been looking at the Renogy 200w bendable panel and Bougerv 200w curve. Any thoughts on those 2 or other options? Also when mounting my batteries, can they be right next to each other, touching? Thanks for any help. More questions to come as the project moves forward.

 

[Wandering Sagebrush]

I see nothing wrong with your plan to stay with AGM batteries and get a larger solar panel. My ATC Cougar is similarly equipped. I’m into simple.

Not so sure about the batteries physically touching. My preference would be to have them in separate battery boxes, well secured to prevent movement.

 

[Vic Harder]

The batteries can be touching. Securely mounting them as Wandering... suggests is a VERY good idea.
Myself and others here have found that bendable panels are not as durable as the heavy commercial/glass units.

 

[Deancamp]

I did think from my research that the rigid panels are more durable. I have roof mounts already so I would not be putting additional holes into the roof. Do you do anything to account for the additional weight, for when raising the roof or just deal with it? My wife struggles with it now but is determined to raise the roof herself. Stronger struts??

 

[Deancamp]

Any particular brand of solar panels anyone has had good luck with to research?

 

[Wandering Sagebrush]

Regarding raising the roof, consider using a speaker lift to do the heavy lifting. There are a number of threads on building one. Guitar Center sells them for about $170.

 

[Vic Harder]

Stronger struts help, speaker lift is good. I have 80# struts and it is relatively easy to lift the top. Relatively.

 

[Jon R]

Just another comment on batteries touching being OK: lots of residential solar setups in the past had large banks of automotive style lead acid batteries tightly packed together.

 

[Deancamp]

Thanks guys, that will help me save space in my battery box.

 

[Deancamp]

If I decide on a rigid (heavier) solar panel, I will be looking into both of the roof lift options.

 

[Deancamp]

When comparing solar panels what do these things mean?
1) Open Circuit Voltage
2) Short Circuit Voltage
3) Optimum Operating Voltage
4) Optimum Operating Current

 

[Jon R]

1) open circuit voltage is the highest voltage the panel will generate in full sun with nothing connected to it other than a volt meter. No load current path, hence the circuit is “open.” You need to make sure your solar charger can handle the open circuit voltage of your panel network. For a Victron MPPT 100/30, that’s what the 100 is referring to.

2) short circuit current is just that - short the panel terminals through an ammeter when the panel is in full sun, and measure the current. This is the highest current the panel can put out. You need to make sure your panel wiring can handle this current without overheating.

3) optimum operating voltage is the voltage at which the panel can deliver the most power (watts)

4) optimum operating current is the maximum current that can be delivered at the optimum voltage, resulting in the greatest power output. You want to make sure your wiring can handle this current without excessive voltage drop.

 

[Deancamp]

Thanks Jon for the explanations. I have chosen the Renogy 200w panel. With factory wiring and the Overland Solar MPPT 100/15 I think I am covered but please confirm. The Renogy panel is rated at 23v Open Circuit Voltage, 11.05A Short Circuit Current and 10.42A Optimum Operating Current. How do I check the polarity to see if it is correct when plugging in? I also want a battery monitor. Nothing special, I would like to mount it in the battery box and get a digital read out of battery life. Can you point me in the right direction for that?

 

[Vic Harder]

Your existing/factory wiring will be fine with that panel. Use a voltmeter to check polarity. For a battery monitor, the Victron Smart Shunt is ideal, especially since you want it tucked away in the battery box.

 

[Deancamp]

Thanks Vic, the project moves on.

 

[Deancamp]

Has anyone upgraded the wire size from the truck battery to truck/camper plug without upgrading the wiring within the camper to the house batteries? How much could I expect to gain by only upgrading this portion?

 

[Wandering Sagebrush]

Dean, unless you’re dealing with a very heavy load/draw, I don’t believe there is much gain from upsizing internal wiring.

 

[Deancamp]

To be clear, if wiring from truck battery to plug is upsized, I can gain the truck charging batteries faster but no big advantage to inside camper?

 

[Wandering Sagebrush]

That is my opinion. Internal circuits are sized by the the amperage draw of the device.

 

[Jon R]

When you are charging a 12 volt dc battery from an alternator that is 25 to 30 feet away via the wire, the voltage drop along that 50-60 feet of overall circuit wire will limit how much charging current you can achieve. Using 10 gage wire (typical truck and camper factory wire size for this circuit) for that entire run is likely to be inadequate to charge your camper battery. Anything you can do to reduce the overall voltage drop and increase the voltage applied to the camper battery will increase the charging current. So running larger wire from the alternator to the camper connector will help. It would be best to increase the size of the whole run, but it’s not required as long as the smaller wire is of adequate size to prevent excessive heating from the resulting current level.

A DC to DC converter charger is another way to address this issue, although you’d still want to increase the wire size somewhat.