Solar Show and Tell

[AirMiles]

Here are the first 30 days of production numbers from 600W of solar operating on the Airstream Factory Prewire. There was never a full day of sunny skies while camping this month. Either I was under tree canopy or had overcast conditions. The system still met all my 12V power needs and produced a peak watt hour day of 2kWh with a morning of sunshine and an afternoon of mostly cloudy to overcast conditions. No generator or shore power charging was needed during the month. All but three consecutive days early in the month were at non-electric campsites. Those were three of the days that the system never made it to absorption because of nearly complete tree canopy as documented earlier. I’m done with consecutive 30 day camping periods for this season, with only long weekends planned for the winter months. Here are the chart and data table documenting the performance.

[billrector]

Interesting! What happened on the 11th? Massive production but never left bulk charge. That day seems less me an outlier.

[AirMiles]

Originally Posted by billrector

Interesting! What happened on the 11th? Massive production but never left bulk charge. That day seems less me an outlier.

I was load testing the system that day because it was forecast to be sunny. I ran the battery down overnight, I turned on the DC refrigerator at 7:00am, we vacuumed and used the hairdryer. Then we turned on all the lights and fantastic fans. We left it that way because we had sunshine until about 1pm. Then the overcast conditions returned for the rest of the day. We turned off the DC refrigerator and the lights. The system bulked the rest of the day, never bringing the battery up to 14.55V, so it never went into absorption or float.

Just because the system does not make it to absorption or float does not mean the battery did not get nearly charged if it produced around 1kWh for the day. You can see this happens on quite a few big production days. When you have a significant load on the batteries, it can be difficult for the solar to bring the batteries to absorption voltage. But the voltage on the batteries will still be nearly fully charged by the end of the day. On the big 2kWh the voltage was 12.75 and hydrometer readings were 1.275. On some of the other similar days, battery voltage was actually fully charged at 13.0V.

Big production days (1kWh) without absorption or float stages were days where I ran the DC refrigerator. As I've stated before, I cannot run my DC refrigerator continuously and keep my batteries charged. Way more than 600W of solar and 235AH of batteries would be needed to continuously run the refrigerator and maintain fully charged batteries.

[uncle_bob]

Hi

You also now are into the part of the year where days are getting shorter along with the sun angle getting lower. Both will make it harder to produce "front page news" sort of daily solar numbers.

We do a mix of shore power and off-grid. It's rare for us to be running solar for weeks on end. That said, the battery bank has yet to go below 50%. In three years we have never deployed a generator.

Bob

[uncle_bob]

Hi

Ok so we *almost* hit a record last night. With it at 27 degrees (according to the weather guy) or 32 degrees (according to the sensor on the battery) *and* the tank heater pads turned on *and* the furnace running all night *and* the 4A of "other stuff" we usually run ..... we hit 53% on the battery.

Indeed pulling 8 to 10A that's not an un-expected thing. We started at 74% yesterday evening. At 8AM I'm getting an entire amp out of the solar ... we can hope for more later in the day

So on that basis, no we can't go for weeks and weeks off grid. Indeed with a bit of care I can pull at least a third of that load out of there if we needed to.

With the fine old stock AGM batteries things would be a bit different right now, even with four panels on the roof.

Bob

[AirMiles]

Agree Uncle_Bob, we're are not in prime solar season.

During the summer, with long sunny days and short tree shadows, I could live indefinitely on 200W of solar panels. In the fall and winter, with shorter overcast days and long tree shadows, I needed the 400W of solar panels on my 25' Airstream to avoid generator charging. Now I put 600W on my 27' Airstream's roof. Occasionally, any number of Watts of solar panels is not enough - as evidenced by the overcast and rainy day when my 600W of panels only produced 190Wh of charging in last month's data with a peak of a whopping 93W.

I hope your solar panels find some sun today.

[Kanusport]

Originally Posted by AirMiles

Agree Uncle_Bob, we're are not in prime solar season.

During the summer, with long sunny days and short tree shadows, I could live indefinitely on 200W of solar panels. In the fall and winter, with shorter overcast days and long tree shadows, I needed the 400W of solar panels on my 25' Airstream to avoid generator charging. Now I put 600W on my 27' Airstream's roof. Occasionally, any number of Watts of solar panels is not enough - as evidenced by the overcast and rainy day when my 600W of panels only produced 190Wh of charging in last month's data with a peak of a whopping 93W.

I hope your solar panels find some sun today.

i

What type of batteries and how many amp hours are they? I looked back page or two in this thread but didn’t see the answer to my question. I’m thinking about expanding from my current setup or one 100 ah lifepo4 and a 200 watt suitcase. It’s meeting my needs but I’m only in the trailer in the morning or evening after playing outside all day and my trailer has no inverter so it’s all 12v stuff I’m powering.

[AirMiles]

I have a pair of Duracell EGC2 6V Golf Cart Batteries with 230AH from Sam's Club. Uncle_Bob has a four battery Lithium battery bank. You probably want to hear about his batteries. I like the performance of my $250 pair of golf cart batteries. They give a lot of AH for a small price. They are tough and can handle deep draw downs. They are good for 10 to 20A loads. If I needed a larger battery bank, I'd go with Lithiums like Uncle_Bob.

[uncle_bob]

Originally Posted by Kanusport

i

What type of batteries and how many amp hours are they? I looked back page or two in this thread but didn’t see the answer to my question. I’m thinking about expanding from my current setup or one 100 ah lifepo4 and a 200 watt suitcase. It’s meeting my needs but I’m only in the trailer in the morning or evening after playing outside all day and my trailer has no inverter so it’s all 12v stuff I’m powering.

Hi

The point that lithium's really start to get "interesting" is when you decide you need more than what a pair of good lead acid's will provide. A 100AH lithium really does not give you anything more than a stock pair of group 27 AGM's. Why? One reason would be space, the other would be weight.

I started off looking at a pair of lithiums to replace my virtually new AGM's. (they are still sitting over there in the garage for me to trip over .... we just got home). The more I looked at the numbers, the less I liked the "margin" that provided. The perfect example would be this morning at ~50% on a set of four. With two, that would have been game over.

Indeed if you are going to keep up with *any* type of battery, you will likely need more than 200W of solar.(or a generator) A lot of my charging is done while bumping down the road. That makes roof mount a very nice thing. I really *do not* like setting up and tearing down a lot of stuff. Simple is better

You *are* paying a big pile of money for four lithium's. There's no way around that. We spend a lot of time out in the trailer. We get a lot of use out of the whole rig. That makes the payback math a *little* easier. It still does not put it into the slam dunk category.

Bob

Sure wish I could find somebody to give the AGM's to. I can't stand the idea of turning them into the recycling shed ....

[cptdzl]

Originally Posted by uncle_bob

Hi

Bob

Sure wish I could find somebody to give the AGM's to. I can't stand the idea of turning them into the recycling shed ....

I'd be interested in them?
Rick

[CarterKraft]

Originally Posted by Kanusport

i

What type of batteries and how many amp hours are they? I looked back page or two in this thread but didn’t see the answer to my question. I’m thinking about expanding from my current setup or one 100 ah lifepo4 and a 200 watt suitcase. It’s meeting my needs but I’m only in the trailer in the morning or evening after playing outside all day and my trailer has no inverter so it’s all 12v stuff I’m powering.

The single 100Ah lifepo4 battery looks really promising on paper but when comparing $950/100ah of lithium to $225/210 ah of lead acid for long term low amp draws the math gets fuzzy. If you take the 70-80% DOC rule for flooded lead acid batteries you'll have 150-160 ah of power compared to 100ah of the lithium, maybe they are under rated so call it 110 ah.

According to BattleBorns own study lead acid batteries will perform better than lipo batteries if the amp draw is low and over a long period. IF the amp draw is moderate to high lipos will outperform lead acid easily and provide high current for the full 100ah rating, something lead acid could only dream of.
The lithium batteries will also charge must faster than the lipos getting you topped up sooner with less waste and theortically getting more AH per day than the lead acid counter part.
The rub for me becomes adding the second 100ah lipo battery pushed the cost up to near $2000 range for what I am getting away with using a $225 set from Sams.

Your research will let you know what works for you.

[uncle_bob]

Originally Posted by CarterKraft

The single 100Ah lifepo4 battery looks really promising on paper but when comparing $950/100ah of lithium to $225/210 ah of lead acid for long term low amp draws the math gets fuzzy. If you take the 70-80% DOC rule for flooded lead acid batteries you'll have 150-160 ah of power compared to 100ah of the lithium, maybe they are under rated so call it 110 ah.

According to BattleBorns own study lead acid batteries will perform better than lipo batteries if the amp draw is low and over a long period. IF the amp draw is moderate to high lipos will outperform lead acid easily and provide high current for the full 100ah rating, something lead acid could only dream of.
The lithium batteries will also charge must faster than the lipos getting you topped up sooner with less waste and theortically getting more AH per day than the lead acid counter part.
The rub for me becomes adding the second 100ah lipo battery pushed the cost up to near $2000 range for what I am getting away with using a $225 set from Sams.

Your research will let you know what works for you.

Hi

There is a *lot* of experience out there that suggests a 50% depth of discharge is the target for lead acid batteries.

Since you have a BMS on modern lithiums, the max discharge point is "the BMS shuts it off". That is a point that the manufacturer is confident is ok with their batteries. On a modern 100AH lithium, you get 100AH of usable battery.

Bob

[GMFL]

Wires ran. All that’s left to do is penetrate the roof for combiner box and lay out and Mount the 4 Renogy Eclipse 100 watt panels.

[skitger]

Ronnie,

The red power switch ? It’s for the solar disconnect right? It looks like it is between the solar controller and the pos bus bar, is that right. Nice wire job, I have been planning my system for this winter project, keep the pics coming!

[CarterKraft]

Originally Posted by uncle_bob

Hi

There is a *lot* of experience out there that suggests a 50% depth of discharge is the target for lead acid batteries.

Since you have a BMS on modern lithiums, the max discharge point is "the BMS shuts it off". That is a point that the manufacturer is confident is ok with their batteries. On a modern 100AH lithium, you get 100AH of usable battery.

Bob

I won't debate the experience that says 50% is the no harm number but I'll add that in my use case it doesn't matter. My 25 nights (if I am lucky) per year = approximately 30 charge cycles. That means the reduced charge cycle rate will last me 10 years... No I don't expect 10 years out of the batteries and at the current price I don't need them to, if I can get 3 years I'll be happy and gladly swap them out for some new ones when the time comes.
At the rate lithium cell prices are dropping I may be able to go lithium will a minor price increase.

[AirMiles]

Originally Posted by GMFL

Wires ran. All that’s left to do is penetrate the roof for combiner box and lay out and Mount the 4 Renogy Eclipse 100 watt panels.

Nice installation! Thanks for sharing your pictures which will be very helpful for others. What batteries will you use? Looking forward to seeing your rooftop layout and hearing how your system performs. I know you will be happy with 400W on the roof.

[farafield]

Originally Posted by CarterKraft

I won't debate the experience that says 50% is the no harm number but I'll add that in my use case it doesn't matter. My 25 nights (if I am lucky) per year = approximately 30 charge cycles. That means the reduced charge cycle rate will last me 10 years... No I don't expect 10 years out of the batteries and at the current price I don't need them to, if I can get 3 years I'll be happy and gladly swap them out for some new ones when the time comes.
At the rate lithium cell prices are dropping I may be able to go lithium will a minor price increase.

Thanks for this perspective. For those of us who are getting out occasionally and/or for shorter trips, this is an important point it seems.

[GMFL]

Originally Posted by skitger

Ronnie,

The red power switch ? It’s for the solar disconnect right? It looks like it is between the solar controller and the pos bus bar, is that right. Nice wire job, I have been planning my system for this winter project, keep the pics coming!

Rick,
The “Red” Blue switch is my solar array disconnect switch between the panels and the solar controller. It allows me to isolate the panels from the system.
The “Black” 40amp DC breaker is between the Victron 100/30 and the positive buss bar.

Can’t wait to see the pics. I LOVE WIRES!

[GMFL]

Originally Posted by AirMiles

Nice installation! Thanks for sharing your pictures which will be very helpful for others. What batteries will you use? Looking forward to seeing your rooftop layout and hearing how your system performs. I know you will be happy with 400W on the roof.

Thanks,
Long story long.... I’m currently writing a 4 part column for RV Life/DIYRV.com.
When I did my initial solar install it was 2 Renogy 100 watt panels for 200 watts total with Victron 100/30 controller using factory prewire. This system performed very well (No problems). But I did not document it as well as I needed to.
I was fortunate enough get 4 Renogy Eclipse 100 watt panels through my affiliate program with Renogy. This allowed me to work through a “Reinstall” of my solar on my 23D. I am documenting the install much better this time to help with my writings.
I’m running new wire from the controller to the roof because that’s what most RV owners would have to do with there installs.
I’m also going to use MC4 combining plugs under the panels pairs. This will allow we the ability to run a ALL Parallel system or Parallel Series just by how I have the panels plugged up. This will also allow me to run only two wires to the combiner box.
Anyway. I’m using the same charger controller, battery monitor, and hardware. So basically I’m just going the long way around to change the panels.
Batteries
My current battery set up is (2) 6 volt Trojan T105 lead acid batteries. These batteries are very well maintained and have performed flawlessly form day one.
My plan through this process is to convert to Lifeline AGM batteries and do a fair amount of testing and research of them vs Lithium, but this is a debate for another thread.

Look for my 4 part series on Solar to publish next month
Part#1 What is Solar and Do I need it?
Part#2 I need it, but What do I need?
Part#3 I need it, but How much do I need?
Part#4 DIY Solar installation!
Maybe a Part#5 if the installation goes long........


So basically I’m blessed with the opportunity to convert my solar for 200 to 400 watts, play with wires, and help others through the process.
This makes me happy!

[Fair_Enough]

Ronnie, very nice and neat indeed. Addressing needs first is beautiful. And, thank you for helping others. I will be following your articles.
Thanks
Clint