Adding to my solar setup

[jbsiii]

Hi,
I currently have 200 AH of Battle Born batteries and two 200 watt Rich solar panels, using a cheapo Renogy PWM charger, I went with this charger for cost, and the fact that it fits into the panel on my Jayco trailer where they would normally put their GoPower charger. My experience last year showed that 200 AH is not enough, given my residential fridge and the power demands of running fans on hot days, furnace on cool nights, etc. I'm planning to add another 100 AH battery to the mix, and am considering the following:

• Replace the PWM charger with the Renogy DCC50S MPPT combination unit.
• Running the necessary cable (probably 1/0) from my truck battery (it's a long truck), where I have well over 300 amps of charging current available, thanks to dual heavy duty alternators on my F350 with snow plow/camping package.
• Adding an additional Rich 200 watt panel, running parallel solar connector and sets of cables down to the DCC50S, so as to not overload the existing 12 gauge wiring that Jayco used when they pre-wired for solar.

This should give me 600 theoretical watts of solar input along with the alternator current to allow me to charge with up to 50 charging amps on cloudy travel days and sunny camping days.

Thoughts?

 

[HarryN]

You are still going to be far short with the new arrangement.

- The renogy MPPT controllers use a lot of power in standby - so just about anything else will be better.

- For MPPT controllers in general, this will only help you if the panel array voltage is at least ( battery voltage ) + (12 volts or more).

The nice thing about PWM controllers is that they can turn on when the panel voltage is only 1 - 2 volts higher than the battery, but MPPT needs at least 5 volts and to gain any real efficiency - at least 12 volts more.

I would try to fit 3 panels on top, wire in series and then feed that down through the wire to the MPPT controller. (example victron or midnight solar)

Four batteries will help a lot over three. It might take 2 batteries of power per day just to run the fridge.

If you are spending a lot of time in overcast areas, consider to use poly panels instead of mono - but adding a third will help either way.

___________

If you want to move power from the engine to the load in the trailer, one method is to use a thick cable and a DC - DC charger in the trailer near the batteries. Without the DC - DC charger, not much current will move reliably. Dealing with a 1/0 cable set between vehicles is doable but a pain.

Another path is to put an inverter in the truck and run it using 120 vac in 10 awg back to the trailer. That way it is just normal ( as in marine grade or similar ) 120 vac wiring and plugs. This is done pretty commonly in vans.

______________

 

[Rednecktek]

What are the specs on those panels? You say you've got 400w of panels but since PWM's just cut off the extra voltage, check the Imp and multiply that by 14.4v to see how much wattage you're really able to get. I'd say that a proper MPPT controller in the 40a range will net you quite a boost over what you have now, but go for a 60a if you're looking at adding a 3rd panel.

Rule of thumb is 10a of SCC per 100w of panel @ 12v nominal, so 400w should have a 40a controller on it.

 

[littleharbor2]

.

• Running the necessary cable (probably 1/0) from my truck battery (it's a long truck), where I have well over 300 amps of charging current available, thanks to dual heavy duty alternators on my F350 with snow plow/camping package.

Keep in mind that the BMS's of your batteries have a current limit that if exceeded will shut down the batteries. Also, typically there's a limit to how many batteries can be ran in parallel and/or series.

 

[HarryN]

What are the specs on those panels? You say you've got 400w of panels but since PWM's just cut off the extra voltage, check the Imp and multiply that by 14.4v to see how much wattage you're really able to get. I'd say that a proper MPPT controller in the 40a range will net you quite a boost over what you have now, but go for a 60a if you're looking at adding a 3rd panel.

Rule of thumb is 10a of SCC per 100w of panel @ 12v nominal, so 400w should have a 40a controller on it.

He has 2 battle borns (plans to add 1 -2 more ) , and they can charge at up to 50 amp each, so that is not a problem.

BBs can be run up to 48 volt - not sure how many in parallel but a lot more than 4 strings. I build 24 volt and 48 volt packs with them all of the time.

________________

Rich solar web site - Imp = 9.8 amps @ Vmp = 20.4. Count on getting a lot less most of the day.

3 panels in parallel would at least in theory be nearly 30 amps via PWM but would start running very early in the day and late into the evening.

The Vmp isn't high enough to run consistently in parallel into a MPPT unless he switches to running them in series.

A lot of van / rv customers want to run the panels in parallel because it is common for them to be park in partial shade - so tricky.

The main limitation is that 12 awg solar wire but that is just resistance loss, not a serious issue. 12 awg / 30 amps is within the ampacity, but of course non ideal losses wise for all of us perfectionists.