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Old 08-15-2020, 02:29 PM   #1
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Max solar/battery system on 16RB

My wife and I are seriously considering picking up an Airstream Caravel 16RB for a mix of dry/wet camping. Sometimes we enjoy dry camping for an extended period of time 1-2 weeks. I’m trying to figure out what kind of solar/battery system I’ll need in order to support running the 12v fridge (at a minimum) for that amount of time with the goal of completely avoiding a generator (will have one as backup in worst case scenarios) to charge the batteries. From what I’ve read so far, the optional “stock” 90w solar system and battery set up will not support this.

So, I imagine I would need to upgrade to lithium batteries (as much capacity as it will hold) and the maximum amount of panels/wattage that will fit on the roof.

Does anyone have any experience maximizing solar/battery on their 16RB? What are the best specs I can hope to achieve?

Thanks in advance!
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Old 08-15-2020, 07:59 PM   #2
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The fridge will likely use an average of 30 amps per day. The two lifeline batteries included with the solar package will give you at least 2 days if your only feeding the fridge. So your question is tough to answer. If you camp in sunny spots and get 6 hours of good solar a day then adding another 90 watts to the optional package would allow you to go indefinitely and make the lithium overkill. So it’s all dependent on lots of variables. Figure out how much power you will consume and where you will mostly camp and go from there.
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Old 08-15-2020, 10:00 PM   #3
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Originally Posted by Shiny16 View Post
The fridge will likely use an average of 30 amps per day. The two lifeline batteries included with the solar package will give you at least 2 days if your only feeding the fridge. So your question is tough to answer. If you camp in sunny spots and get 6 hours of good solar a day then adding another 90 watts to the optional package would allow you to go indefinitely and make the lithium overkill. So itís all dependent on lots of variables. Figure out how much power you will consume and where you will mostly camp and go from there.
Thanks for the replyóthatís really good info! So, are two 90W panels generally thought to be the max amount of panels that can be installed on the 16RB?
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Old 08-16-2020, 06:04 AM   #4
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On my 2020 only 1 90 watt Zamp fits on the road side. On the curbside I used two 45 watt Zamps. The bath exhaust gets in the way for a 90. The 45 Zamps are also a slim version. Basically 1 90 cut in half. The 90 watt came with the unit. If I was doing it on my own I would use 4 of the Zamp 45s. You can get marginally better placement and reduced shading with 2 45s rather then 1 90.
I’m sure if your creative you can fit more. Just remember no matter how much you add or money you spend there are still rainy and cloudy days. There is no shame in running a generator.
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Old 08-16-2020, 09:12 AM   #5
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Experience from my last trailer, my suburban furnace could drain my battery in 24-48 hrs, easily. Have not done any research, some off grid experience in the mountains, it seems that my Caravel furnace draws less amps and I can barely hear it. Very good. You're further north and with a cooler climate, more trees, clouds, & sun lower in the sky. Solar results will be different. I've had a 3way (gas) fridge on other trailers, for years. After 6 months using my compressor fridge I would not go back to a 3way. My past dometic fridges produced heat to cool. Solution add electric fans. Kind of silly when you thing about it. Yesterday it was 103 here, plus you have gas/electric ammonia fridge running, doesn't make for a cold fridge. Seems to me, Airstream gave me a better fridge that uses a few more amps, but might have made up the difference with a more efficient furnace. Not sure about your climate, but you might do some research on the furnace and it amp use.

My only complaint on the NovaKool fridge is sometimes at night I can hear the compressor hum.

Looks like to me, without sun I would need to run my gen for a couple of hours, every 48 hrs to keep my fridge & heater going which is the same as my last trailer. With full sun and another 90W strip probably would not need the gen.

I got a 90W strip on top and when home for awhile I going to order another portable 90W and still mulling about the 45W above the door.
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Old 08-16-2020, 06:10 PM   #6
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We have a 2018 16" Sport with two 90amp Zamp panels. Two interstate wet 12v batteries. I changed out the solar controller to a Renogy mppt. With any sun we can get a minimum of 4-6 days off the batteries. Our limiting feature is the combined black grey tank. With careful water use we can get 4-5 days before we have to dump. Batteries are three years old and going strong, waiting for them to die to get a lithium replacement.
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Old 08-17-2020, 08:55 AM   #7
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So you want to go for 7 to 14 days on battery without using a generator.

You figure that the most solar you can have is 180 watts. 180 watts will provide max 15 amps per hour (amp hour) (180w/12v=15A). Unfortunately, you will likely never see the full 15A - more like 8-10A for maybe 8-10 hours = 70 to 100Ah total incoming. But for fun - let's use 15Ah.

For a fridge to use only 30 amp hours per day (on battery alone without using solar) - it would draw only 1.5 amps on average. That is a pretty low number. I would recommend that you verify the fridge draw. If you have a battery monitor - such as a Victron 712 - you can use it to estimate useage. For fun - let's use 30Ah per day.

So - let's do the math for the fridge only.
usage:
30Ah per day x 7 days = 210Ah.
30Ah per day x 14 days = 420Ah
Odds are you will use twice that.

input:
15Ah per day x 7 days = 105Ah
15Ah per day x 14 days = 210Ah.
Odds are you will get less.

So in 7 days the minimum draw will be 210Ah (no lights, no radio, no TV, just fridge) and the maximum charge will be 105Ah leaving you with a minimum battery discharge of 105Ah.

Now, let's talk batteries.

Lead acid batteries are only good for 50% of rated amp hours if you want them to last. Otherwise, expect to replace them every few years. Buy a quality battery like Lifeline or Trojan. A Group 27 12v battery is 80Ah, a Group 31 12V battery is 105Ah. So based on the math, you will need (2) 105Ah G31 12V batteries to last 7 days.

A couple of issues to consider:
1. Flooded lead acid (FLA) or AGM need to be brought to 90-100% charge daily or they will develop lead sulfate crystals on the plates (sulfation) which will reduce capacity (less amp hours). So you will need to figure this into how many amp hours you want in the bank.
2. FLA/AGM are nominal 12V which means when you see 12V you have used 50% of the battery capacity.
3. Motors and compressors (water pumps, fridges, etc.) work harder, hotter and less efficient at lower voltages.
4. FLA/AGM batteries charge slowly. The bulk stage (up to 80%) allows higher voltage and higher amps to charge. The last 20% (absorption) reduces voltage and amps. It can take 8-10 hours to fully charge due to internal battery resistance and reduced voltage/amps so not to boil off the electrolyte. There is also a 15% efficiency loss - for every 100 watts charge, 15 watts is lost to chemical energy conversion and only 85 watts is absorbed by the battery.
5. FLA/AGM both require maintenance. FLA should be charged to 90-100% daily and should be equalized monthly. FLA need to have the electrolyte water level monitored. AGM should be charged 90-100% daily.
6. FLA/AGM batteries have cycle life between 300-1000 cycles depending on the manufacturer. This cycle life is is based on 100% maintenance and ideal temperature conditions. This never happens. A cycle life is a 100% discharge based on discharging only 50%. Discharging a FLA/AGM will kill the battery quickly.

Lithium Iron Phosphate (LiFePO4) batteries are good for 100% rated amp hours. However, it is recommended that only 80-90% be discharged. Purchase only lithium batteries with a BMS (battery management system). The BMS protects the battery. BMS come in different amp ratings. The most common is the 100A BMS. That allows 100 amp discharge and 100 amp charge ability. Some batteries offer 150A, 200A, 300A BMS which allow for higher discharge rates and less BMS stress.
So, based on the math, you need (1) 105Ah lithium battery to last 7 days.

A couple of issues to consider:
1. Lithium batteries are 1/2 to 1/3 the weight of FLA/AGM.
2. Lithium batteries are available from 100Ah to 400Ah and all weigh less than 100lbs.
3. Lithium batteries are nominal 12.8V. This means that you still see around 12.8V at 50% capacity and beyond.
4. Lithium batteries require no maintenance.
5. Lithium batteries can stay at a partial state of charge indefinitely without damage to the battery. Lithium batteries can be 100% discharged without damage to the battery.
6. Lithium batteries have 99% charge efficiency. Basically, every watt that the solar panel produces will be stored in the battery. This is important especially on low sun or short days.
7. Lithium batteries have a cycle life of 3000-5000 cycles depending on depth of discharge. The lower DOD, the longer the cycle life. A 25% average discharged battery will have longer cycle life than an 100% average discharged battery. In real terms - if you discharge the battery 100% on a daily basis, 3000 cycle life/365 days = 8.2 years. 50% daily discharge = 16.4 years. At the "end of life" a lithium battery still holds 80% of capacity. That means a 100ah battery still has 80Ah of usable energy.

You have a lot of LFePO4 options.

Potential suppliers include:

AMPS Lithium
https://lithiummarinebattery.com

Battleborn
https://battlebornbatteries.com

GoPower
https://gpelectric.com/product-category/batteries/

LiFeBlue Battery
http://www.lifebluebattery.com

ReLion
https://relionbattery.com

Renogy
https://www.renogy.com

SmartBattery
https://www.lithiumion-batteries.com
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Old 08-18-2020, 11:17 PM   #8
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Thank you for taking the time for this detailed post. I am not familiar with batteries and have read it a few times. Would you mind recommending the best battery for a 16RB that I should consider. I am ok paying more if the battery is that much better. I looked at your links and don't even know where to start.
Again, thanks for all the time in your analysis. I'm hoping one day to understand it
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Old 08-25-2020, 01:31 PM   #9
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Originally Posted by Lockie View Post
Thank you for taking the time for this detailed post. I am not familiar with batteries and have read it a few times. Would you mind recommending the best battery for a 16RB that I should consider. I am ok paying more if the battery is that much better. I looked at your links and don't even know where to start.
Again, thanks for all the time in your analysis. I'm hoping one day to understand it
I am sorry for the complicated explaination but it gives you a lot to chew over.

Basically, all you need to do is:
Figure out is how many watts you plan to use on a daily basis. Some things run all the time. Others only for a short period.
Figure out what you can expect for charging from solar (in watts)
Figure what you can expect from a generator / charger combination (watts)

I have 600 watts of solar - (2) 300 watt Renogy 24v panels. ($600 at Home Depot)
I have (2) 30A 24V to 12v charge controllers (300 watts puts out 25A @ 12v) and it is cheaper to buy (2) 30A charge controller than (1) 60A charge controller - plus the redundancy if one fails.
I have (1) AMPS 400Ah 8D lithium battery with 200A BMS.
I have the Victron 712 battery monitor - my wife loves it because she can lie in bed and know how much energy/Ah we have.
I have a 30A Progressive Dynamics converter charger.

This cost less than $5000 installed.

I have had the battery for 3 years and still wake up in the morning to 13+ volts. It is an AMPS 400Ah battery with a 200 amp BMS. ($2800) lithiummarinebattery.com Based on my history report from my Victron battery monitor I have consumed 29,566Ah with an average discharge of 139Ah and deepest discharge of 286Ah. ($2800)

The 600 watts will generally provide 25-35 amps charge. (2) 24v 300 watt Renogy panels ($600)

I have (1) AIMS 30 MPPT charge controller ($160) and (1) cheap chinese PWM charge controller ($50). Probably will upgrade to another MPPT controller as the efficiency of the PWM is 75-80% and the MPPT is 99%.

The Progressive Dynamics lithium 30A converter charger ($175) is a great product. I could have up to 60A converter charger for the 400Ah battery.

I have a 2200w Westinghouse generator ($500). I sometimes run a 5500 btu air conditioner and charger at the same time on hot days. The genny can only handle a 30A charger and the A/C running at the same time or just a 60A charger. Most often I will just run the A/C on the genny (runs at lower rpm and uses less gas) and just let the solar charge the battery.

I have a 2000w Voltec pure sine wave inverter. ($250 - no longer made) It is enough to run the microwave or A/C.

Sometimes we will run the A/C at night. It usually runs 25-35Ah per hour. My wife fell asleep the other night with it running and she ran through 160Ah. We got most of it back the next day and topped off the day after.

This is my real life experience. Hope it helps you some.
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Old 08-25-2020, 02:23 PM   #10
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Like Shiny16 and Sport_16_STL said, add some extra solar to the roof if you can, a good MPPT with batteries that fit into your battery location, will be a big improvement. I have 240 Watt on the roof of my 16' and two 6Volt GC batteries, we use 20-30 ah a day and we are topped off in the morning with sun. I went with a budget plan, my 2018 only has the front rails to store the batteries, so location and size are issues picking batteries, my 2 Interstate batteries works fine for the first 2 years also. Check out the Solar Show and Tell thread, lots of good DIY info there. GMFL has a new 2020 30FB and has the new frig, he is a great resource for info too. Good Luck, Rick
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