Solar for 60AH/day usage w 2 DC220-6 Fullriver 6 Volt 220 AH AGMs

[Deanm]

Hello all,
Total newb here, Ive been immersed for last few days watching videos / reading forum posts. We upgraded our 2019 30’ Toy Hauler when we bought it a year ago and tested out the upgrades all last summer. Upgrades are as follows:
- 2 -DC220-6 Fullriver 6 Volt 220 AH AGM Battery wired in series in a RV Lock Box on the tongue
- Victron BMV 712 wired in the batter box
- EMS-HW30C EMS-HW30C 30 Amp Hardwired EMS with Remote Display
- PD 4655L Wildkat PD 4655L MBA WildKat 55 Amp Main Board Assembly to replace WFCO 8955 or Parallax 7155
All work great and I can’t believe I was able to install / make cables / etc. I had help from the electricians at my work with some tools and supplies and I still have access .
The RV also has 4k Onan built in generator.
We Boondock about half the time we go camping , mostly state parks / etc and usually 3-7 days. Using the Victron BMV and hand calculating ( without really trying to conserve ) we use about 35 -50 amp hours a day taking the batteries to about 55 or 60 % after 2.5 days or so. It takes the 4k Generator ~6-8 hours to get the batteries back up to 95-97 % and Ive only seen it back to 100% maybe once. The Gen is great for when we have to run AC or Microwave but I hate running the gen just to charge batteries ! Adding solar is a hard sell for the wife since we spent extra for the 4K Onan so I want to keep the cost low even though I love to go big for future. Maybe keep it less than $ 1k .
Here come the questions !
1. I want to add a 31” smart TV ( estimate 32 watts ) in the Bedroom and have the option to power it with an Inverter ( 32 watts / 12 volts = 2.7amps for at most 3 hours for a movie on occasion so Ill add that to my above usage and call it 60AH / day with is a high estimate probably. Maybe plug a low wattage fan or my 85watt 17" Macbook pro on occasion ) Is this correct for my daily usage???
2. I have plenty of room on my roof for two, four , ( or even 6 ) of the 40” x 27” Richsolar 100 Watt Polycrystalline 100W 12V Solar Panels that Will Prowse suggests ( but am open to other types/ etc). I plan on putting any solar / inverter components in the storage area under the bed . This would allow me to have an Inverter that I can just plug the TV into instead of wiring outlet (s). Based on this info , What Panels / MPPT / Inverter set up do you suggest for my smallish needs?
3. Side question, If I plug into shore power or start the Generator, do I need to manually switch off the solar charger and or Inverter ?
Thanks for any help !

[hobienick]

I used to make solar panels and I had a 30' sailboat I installed solar on as well for cruising. Here is some food for thought when you are configuring your system. Stay away from inverters if you can. Most likely a smart TV has a power supply that outputs a DV voltage. Use a DC to DC transformer to step your voltage up or down. It will be much more efficient than any inverter.

If you want to save money a PWM charge controller will work. They are not as efficient as the MPPT variety but will do fine.

You do not need to manually disconnect the solar panels if you have another charging source on. Your charge controller will keep the panels safe.

Also, for your AGM batteries you can run them down to 20% with only a minimal effect on life cycle.

Remember, on any type of lead battery technology, that last 15-20% of capacity takes much longer to recharge. It will probably be more efficient from a generator standpoint to stop trying to "top off" and run the generator more often to make up for the 20% loss.

Panels are commodities these days. The main difference is poly vs mono crystalline cells. Mono are somewhat more efficient, but that comes with a higher price tag. Your controller won't care. You can start off with poly at first and change to mono later. Just make sure you don't buy ultra cheap panels as the construction method may cause early failure.

The best way to get maximum efficiency out of your panels is to point them directly at the sun for as long as possible. Fixed mounting makes this hard to do. Remote mounting that will allow you to manually track the sun or even an auto tracking setup will help with this. Not necessary, but it will improve their output.

[Deanm]

Thnx for the reply and info hobienick !
Next question / clarification
If I'm using a 400w PV and have 12v batteries = 33.3amps. Does that mean I need a MPPT charger that is larger than 33amps ? Victrons online calculator spits out their 100/30 CC?

[hobienick]

You will need to get charge controller that is larger than the maximum amps your panel(s) output at 12VDC. I like to add ~20% just to make sure. Usually the cost for the next size up is not too much more. If you ever plan to expand your system you may want to oversize even more so you do not have to buy another charge controller when you do.

Don't feel like you have to stick with Victron for the charge controller. They make good stuff. I especially like their battery monitors. However, you can save some $$ by looking at other brands of MPPT controllers. Look at their reviews and ask the manufacturer/seller questions. This will help you save your $$ for other/nicer components.

One other thing that is often overlooked. Size your wiring correctly. You want to keep DC voltage drop to less than 2%. There are several calculators online. I usually use the Blue Seas website since I am on there looking at components for my systems. They are pricey but I know they can handle rough environments as I use their stuff on a sailboat in saltwater.

[Deanm]

Originally Posted by hobienick

You will need to get charge controller that is larger than the maximum amps your panel(s) output at 12VDC. I like to add ~20% just to make sure. Usually the cost for the next size up is not too much more. If you ever plan to expand your system you may want to oversize even more so you do not have to buy another charge controller when you do.

Don't feel like you have to stick with Victron for the charge controller. They make good stuff. I especially like their battery monitors. However, you can save some $$ by looking at other brands of MPPT controllers. Look at their reviews and ask the manufacturer/seller questions. This will help you save your $$ for other/nicer components.

One other thing that is often overlooked. Size your wiring correctly. You want to keep DC voltage drop to less than 2%. There are several calculators online. I usually use the Blue Seas website since I am on there looking at components for my systems. They are pricey but I know they can handle rough environments as I use their stuff on a sailboat in saltwater.

Ok will do, and I will adhere to the wire sizing. half the reason I'm doing this is to learn my RV electrical system. I have access to the electricians and their tools at work, funny though, When I told him what Im looking at for components, my friend suggested I buy everything form Harbor Freight waaayy less expensive !

[PSU Turf]

I have some Blue Sea bus bars on my set up and agree that they are well made.

If you are looking to keep costs down consider keeping your panels mobile on the ground. We mostly camp in state parks and the sites are shady. If your panels are mounted on top of the trailer they could be in shade for much of the day. 4-6 panels, on the roof, might have the same output as two panels on the ground that can be moved around for optimal sunlight. I have 2 panels on the roof and two on the ground with 30' of wire.

I shopped at Harbor Freight once. Bought a set of impact sockets. The first time I used one it cracked in half. Never went back again. You get what you pay for.

[hobienick]

When shopping for components, keep in mind you will be running several amps of current through them and they will be hidden in enclosed spaces. It might be nice to not go the cheap route. I like to do the job once then be done.

Blue Sea prices are better on Amazon.

[mnoland30]

It sounds like you have lots of battery, and your loads are reasonable. A simple solar system will take care of everything you need, except microwave and A/C. I quit taking my generator along once I installed solar. I hate the noise of a generator. I have a 100 watt panel on the roof, and another 100 watt panel that I can place in the sun with a homemade extension cord. I use the flat trailer connections (2 prongs) for connectors. You can see the red and white, so you don't reverse polarity. I have used a Morningstar charge controller (mounted outside in an electrical box) to control the charge. Simple and inexpensive. I upgraded to a Trimetric battery monitor which is fun, but frankly it is overkill. The beauty of solar is that it will work all day long and get that last 10 to 20% charge on your batteries. It also keeps your batteries charged when you're not using the RV. On most days, our batteries are up to 90% within a couple of hours. Your battery life will be extended by not discharging so much every day. Most days we discharge less than 20%. I bought my panels on eBay. I'm very happy with them.

[babock]

You will be fine with a 30A MPPT like a Victron. The controller will limit the current itself. With 400W, your theoretical max will be 30A or less anyway and you will likely never see that.


The way Victron rates the current is take the number of watts and divide by 14V. Using 12V is never accurate since you will always see over 12V while charging. Will be in the 13s and 14s which is why Victron uses 14.0V.

[pmsherman]

Another reason to get an MPPT controller is you can wires panels in series. Wire four 12V panels as 2S2P and you effectively have two 24V panels. (Actually a much higher no load voltage.) The MPPT controller will convert this down to the appropriate battery charging voltage. Doubling the voltage from the panels to the MPPT controller cuts the current in half which decreases power loss in those wires to 25% of what it would be by wiring the panels in parallel.


Depending on the specifications of the MPPT controller, you might be able to use three panels in series, gaining additional power loss savings. Of course, with three in series, the next jump up is six panels in series/parallel. Another option to add a fourth panel to three in series is to rewire them in the 2S2P configuration.


I'd expect 300W of roof mounted solar panels to provide at least 75A and probably around 100A of recharging at 14V on a sunny day. I'd also try to get panels with internal bypass diodes that allow a cell to be shaded without killing the entire output of the panel.



Phil

[rk06382]

Originally Posted by Deanm

Thnx for the reply and info hobienick !
Next question / clarification
If I'm using a 400w PV and have 12v batteries = 33.3amps. Does that mean I need a MPPT charger that is larger than 33amps ? Victrons online calculator spits out their 100/30 CC?

Charging voltage is 14.6v if you have Lithium. (400w / 14.6v = 27.4a)

My first year (Summer 2018) I had 600 watts with a 40a MPPT. I found out even on a sunny day I never saw more than 365 watts from the 600 watt solar array. I decided to order more solar panels for the roof. I calculated that the 50 amp solar charge controller could output about 730 watts. (50a x 14.6v = 730w) Since I have my solar panels are flat and not angled to the sun, they will never output at full power. I am too old to climb on the roof to ange the panels to the Sun. I posted a thread about having 10-20% more panels than the MPPT can handle.
Solar panel over sizing for rigid roof mount Thread Started 08-17-2018

I installed four more Renogy 100 Watt 12 Volt Monocrystalline Slim Design Solar Panels in March 2019. That brings the total to ten.

Because my panels are fixed on my roof & my MPPT rated at 50 amp, the solar array is limited to about 730 watts. On a trip in early June 2019 to the Fairbanks, Alaska area, I saw upto 49 amps. My solar was able to generate 3.5KWH per day. I could have generated more but the engine alternator is able to generate 90 amps. Once the batteries are fully charged the MPPT shuts off.

Note:

1. 50 amps is the limit of the solar input on my Samlex EVO-3012 Inverter/Charger.
2. Without a Victron BMV-712, SOC is a mystery with Lithium.
3. I love my Battle Born so much I purchased two more.

[pgandw]

Originally Posted by pmsherman

I'd expect 300W of roof mounted solar panels to provide at least 75A and probably around 100A of recharging at 14V on a sunny day. I'd also try to get panels with internal bypass diodes that allow a cell to be shaded without killing the entire output of the panel.

Phil

I think you have a math error. 20 amps at 14 volts = 280 watts. Since roof mounted is going to have losses from latitude and sun angle, 14 amps is about the max charging current, with 10 amps being typical on a sunny day.

Fred W

[mjbenedict]

Originally Posted by pgandw

Phil

I think you have a math error. 20 amps at 14 volts = 280 watts. Since roof mounted is going to have losses from latitude and sun angle, 14 amps is about the max charging current, with 10 amps being typical on a sunny day.

Fred W

I think he totalized it for the day. If you were charging at 20amps for 10hrs it would be 200amps for the day. 200amps (AH or amp-hr) added back to the battery. I thought the same as you then reread his post.

[babock]

Originally Posted by mjbenedict

I think he totalized it for the day. If you were charging at 20amps for 10hrs it would be 200amps for the day. 200amps (AH or amp-hr) added back to the battery. I thought the same as you then reread his post.

Typically, you get around 5 equiv sun hours a day in summer depending on where you are. 300W would give 20A in a perfect world with an MPPT controller aimed perfectly. His 75AH is probably slightly high.



Victron uses 14V when calculating charge current.

[Deanm]

Thanks for all the replies and help! I'm putting together blue print with wire sizing / fuse/etc .Almost ready to pull the trigger / will update ASAP
Dean