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Re: 1920 WATTS OF SOLAR POWER

Reply #25 – May 07, 2017, 01:08:13 pm

Couple of comments:

Will change or remove the boost circuit.

I have not had any requirement for this circuit since we did our mods.  Kind of a tech left over from another time for us.  I did run a 2/0 cable from the chassis batteries, two red tops, to a three way switch and connected the gen set starter.  Removing the lithium completely from starting duties.  The marine switch can engage either or all of them if needed but in five months we have never been close.  The 100w panel and 6a Morning Star controller keeps starters healthy.  (Ours follows Johns design)

Also removed the alternator from lithium by removing isolator and using simple Marine switch.(Brett)  Even on cloudy snowy winter days on the road, the solar kept up with underway 12v house charging and I haven't switched to the alternator yet.  I did test, during that time, the speed of the gen set in bringing the lithiums back up.  Have data on that if you are interested.  It is awesome to go from bulk to float. 

We decided to not go to residential but may go 12v marine.  We are however going to continue to use our greatest power hog...the uline which I won't be without.  Glad you are open to questions as I am learning a lot from your posts.  Push that envelope!

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Re: 1920 WATTS OF SOLAR POWER

Reply #26 – May 07, 2017, 01:35:36 pm

I agree with you. There is a balance of technology liability: complexity, maintainability, reliability and performance. I decided to enhance boondocking in the woods over the shore powered camping experience. So the 120VAC capability for the microwave/convection oven, AC, entertainment center, laptop charging, Nissan Leaf charging, etc... is favored over the 12 volt appliances: heater, fridge and LED lights. In the summer, the heater won't be used much, so the 80% efficiency 120 VAC to 12 VDC converter won't be loosing too much power.

In the end, we pay a price to reduce "energy anxiety". When boondocking in a wooded campsite, the solar panels would be lucky to be generating 100 watts, so we'll be conserving energy regardless. It's all good.

We will still have the generator if all else fails.

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Re: 1920 WATTS OF SOLAR POWER

Reply #27 – May 07, 2017, 03:15:46 pm

I had checked into li-ion systems when we got our coach five years ago,  not mature enough tech then for my budget.

Plus my needs were not high enough.

Great info

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Re: 1920 WATTS OF SOLAR POWER

Reply #28 – May 12, 2017, 01:42:46 pm

Tim
Here is a screenshot of house bank of one day on our run home.  Partly cloudy and no use of alternator circuit.  I have 800w and was running the uline etc.  We were on the post before and after.  Nice to be able to switch it in if needed but over last 6 months have kept it isolated.

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Re: 1920 WATTS OF SOLAR POWER

Reply #29 – May 13, 2017, 05:24:42 am

Nice graph.

I am pleased to report that the upgrade has been installed and is operational. Successfully tested the 48VDC LiFePo4 battery, BMS, solar, 2KW pure sine wave inverter/charger, main engine, generator and alternator operation. Important core changes include:

- Generator starts with engine battery, not the house battery
- Removed diode isolator from alternator charging circuit
- Bypassed / removed boost solenoid

Photos to follow. It was good to see only about one volt of sag (50V vs 51V) on the lithium pack when the convection oven was used, or about 1800Watts of power.

Plan for next week:

- Battery hold-downs
- Secure wiring
- Test drive

My only question is: Without starting boost, will a 1400 CCA AGM battery (two 6Volt golf cart) start a 32 degree F 8.3 Cummins diesel engine? At 60 F, it took about two seconds of cranking to start, with the dash / instrument panel lights flickering.

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Re: 1920 WATTS OF SOLAR POWER

Reply #30 – May 13, 2017, 04:00:19 pm

Sounds like you need more starter battery power. Our 8.3 had 2 red top optimas might be room for 2 group 31 batteries.

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Re: 1920 WATTS OF SOLAR POWER

Reply #31 – May 13, 2017, 04:47:11 pm

Two 31 series. 1900 CCA About $120/ea.

Pierce

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Re: 1920 WATTS OF SOLAR POWER

Reply #32 – May 14, 2017, 07:06:42 pm

Bought two group 31 batteries: from NAPA, P/N BAT 7235 Commercial type with 2250 CCA total. One fit oddly but OK, but I had to make a mount for the other one. They are secure and the engine starts in one second. 

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Re: 1920 WATTS OF SOLAR POWER

Reply #33 – May 15, 2017, 09:08:15 pm

Test drove the rig with all systems functioning and solar panels attached. There was some wind noise at 70MPH of relative wind, but not too loud. At a stoplight, a fellow yelled out his window: "That's America!"

Here are some photos, annotated with the major updates performed. The 48 Volt LiFePo4 battery receives about 1500 watts in full sun.

I just ordered an intelligent charger module for the 12 V DC charger that will provide four-stage charging for the engine battery, including equalization every seven days.

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Re: 1920 WATTS OF SOLAR POWER

Reply #34 – May 15, 2017, 09:15:41 pm

If you just got rid of those silly air conditioning things, you could get on an extra 700 watts!I
I have dry camping envy.

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Re: 1920 WATTS OF SOLAR POWER

Reply #35 – May 15, 2017, 10:59:33 pm

Tim, with the height of some of those panels I would imagine that you are getting wind noise. I also think that there is a lot of "turbulence" under them.
JohnH

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Re: 1920 WATTS OF SOLAR POWER

Reply #36 – May 16, 2017, 05:29:13 am

The highest panel is about one inch below the AC. Perhaps an aerodynamic device can be designed to smooth airflow over these 3/8 inch thick frameless, semi-rigid panels. Being a pilot and President of the our local EAA (Experimental Aircraft Association) Chapter 1250, I hypothesize that there is a market for such a device. For example, aircraft owners pay thousands of dollars for vortex generators, which direct airflow over aircraft.

Another example of this is the Nissan Leaf, which has vortex generating headlights that reduce wind noise at the side view mirrors. Maybe the motorhome industry would be interested in the research.

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Re: 1920 WATTS OF SOLAR POWER

Reply #37 – May 16, 2017, 06:41:33 am

This whole discussion is way over my head. But I want to learn. Do any of you know of a good book to recommend as a base to start?

We have 400 watts and a controller that are each apparently 15 years old. We go full time in 3 years. The next 3 years are for building experience and working to make the coach "right"... and fun.

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Re: 1920 WATTS OF SOLAR POWER

Reply #38 – May 16, 2017, 10:12:06 am

There are a bunch of practical ideas from Technomadia at: Lithium Batteries for RVs - LFP / LiFePO4 - YouTube
I am not much of a book reader, but perhaps I should write one.

Technomadia has a lot of lessons learned from five years of owning LiFePo4 batteries. For example, they taught me about:

1. CLIMATE CONTROL
Put the batteries in a climate controlled area, so I insulated and added a fan and return duct to the battery bay fed from the passenger compartment. This is hidden, of course. Batteries are like humans with regard to temperature because their longevity is increased if used between 40 and 80 degrees Fahrenheit.

2. NEVER CAN HAVE TOO MUCH SOLAR
Boondocking in the woods / shade requires as much solar power as one can afford. This will reduce energy anxiety.

3. NEVER CAN HAVE TOO MUCH BATTERY
Since LiFePo4 batteries longevity can be increased by keeping them between 20 and 80 percent State of Charge (SOC) and reducing charge cycles, the larger the battery, the longer the life. I plan on getting 10 years out of my batteries.

Granted that the above considerations apply mainly to winter boondocking, but it's based on a worst-case analysis with the following factors:

- Low sun angle
- Low temperatures
- High demand (From furnace and modern appliances)

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