Reply
 
Thread Tools Display Modes
 
Old 05-22-2018, 01:28 PM   #1
Skoolie
 
Join Date: Oct 2017
Location: Texas
Posts: 120
Year: 1992
Coachwork: Ward Senator
Engine: 7.3
Rated Cap: 78
Solar Power for The Derelicte Bus

Part of me typing this is for myself, BUT another part of me wants to sanity check the hell out of this, so here we go:

I have 1.6kW of solar power. Output from 5 panels @ 24V is 65Amps. What I'm planning on doing is having an MPPT (60A) charge controller for my panels. It will feed at 12V at 130A to the battery bank.

The battery bank will be composed of 8 of these Crown Batteries and they'll be wired in parallel to deliver roughly 1600aH at 12V (800aH useable). I'll use 4/0ga wire to connect the battery bank to the Inverter and the batteries themselves. The battery bank will be monitored via this Tristar readout. There will also be a DC bus with switches/fuses/cutoffs for distribution to series lighting systems within the cabin. The Inverter will flow out to an AC bus with fuses/switches/cutoffs to the outlets that will be placed throughout the cabin.

My plan for boondocking is to not have a generator. My plan if my solar system fails is to get to an RV park and hook shore power into the inverter. I think I'll have enough solar and battery bank power to survive long enough to get to one, and worst case scenario, if the bus breaks down at the same time then I'm probably stuck anyway.

The surge on the Inverter should be enough to handle the compression stage of a 5,000btu air conditioner with residual amp usage should be well within acceptable ranges, not to mention the only other major appliance I will have is a refrigerator and a laptop.

I'm looking for constructive feedback from the forum, so any help is appreciated. Maybe I should add in another battery? I know that my 5 panels are pretty much at the upper limit of the capabilities of the TriStar MPPT charge controller (assuming they're putting out 100% power). I have read that TriStar MPPTs can be wired in parallel to feed into the battery bank. (It's just going to cost more.)

Thoughts?
__________________
Follow me at: facebook.com/derelictebus for more detailed information on the conversion.
Velocipedic is offline   Reply With Quote
Old 05-22-2018, 01:49 PM   #2
Bus Nut
 
Join Date: Jun 2013
Location: Picton,Ont, Can.
Posts: 820
Year: 1997
Coachwork: Bluebird
Chassis: GMC
Engine: Cat 3116
Rated Cap: 72
Good plan but how can you survive anywhere with just 5000btu's of aircon?

I know your bus is well insulated and well put together but you must handle the heat way better than myself.
Thanks,

John
__________________
Question everything!
BlackJohn is offline   Reply With Quote
Old 05-22-2018, 01:55 PM   #3
Bus Geek
 
Join Date: May 2016
Location: Eastern WA
Posts: 2,501
Year: 2002
Coachwork: Bluebird
Chassis: All American RE (A3RE)
Engine: Cummins ISC (8.3)
Rated Cap: 72
If I understand correctly, you are planning on running 5 320watt panels in parallel to feed a 60 Amp MPPT charge controller to charge 8 12v batteries in parallel.

If that is correct, I see an number of issues.

Lets start with charge controller capacity: 60 Amps. That is the maximum current that it will pass to the batteries. Configured this way you will not be able to properly charge the battery bank you spec'd. You would need to feed your batteries something close to 150 amps.

Batteries: Paralleling 8 batteries is a bad idea. Read up on parallel strings and equalizing. Also, for the capacity system you are considering you would benefit from going with a 24v or 48v battery bank.

Panels: As you will rarely, if ever, get the full rated power out of the panels your 1600watt array is undersized for this battery bank.

I am going to pause here and ask: What is your energy budget?

That is the very first question to answer in the solar design process. Figure out as best you can what your loads will be and size your system to fit.

There are a number of worksheets online that will help you list all of your loads, what their power consumption is and duty cycle. Once you have added up all of your power needs you can properly size your solar array, charge controller and battery bank.

I would suggest a bit of reading to guide your design decisions:

http://jdfinley.com/energy-audit-watt/

https://handybobsolar.wordpress.com/

https://www.solarpaneltalk.com/forum/off-grid-solar

https://www.solarpaneltalk.com/forum...your-batteries

https://www.solarpaneltalk.com/forum...tteries-part-2
PNW_Steve is offline   Reply With Quote
Old 05-22-2018, 02:23 PM   #4
Skoolie
 
Join Date: Oct 2017
Location: Texas
Posts: 120
Year: 1992
Coachwork: Ward Senator
Engine: 7.3
Rated Cap: 78
Quote:
Originally Posted by PNW_Steve View Post
If I understand correctly, you are planning on running 5 320watt panels in parallel to feed a 60 Amp MPPT charge controller to charge 8 12v batteries in parallel.

If that is correct, I see an number of issues.

Lets start with charge controller capacity: 60 Amps. That is the maximum current that it will pass to the batteries. Configured this way you will not be able to properly charge the battery bank you spec'd. You would need to feed your batteries something close to 150 amps.

Batteries: Paralleling 8 batteries is a bad idea. Read up on parallel strings and equalizing. Also, for the capacity system you are considering you would benefit from going with a 24v or 48v battery bank.

Panels: As you will rarely, if ever, get the full rated power out of the panels your 1600watt array is undersized for this battery bank.

I am going to pause here and ask: What is your energy budget?

That is the very first question to answer in the solar design process. Figure out as best you can what your loads will be and size your system to fit.

There are a number of worksheets online that will help you list all of your loads, what their power consumption is and duty cycle. Once you have added up all of your power needs you can properly size your solar array, charge controller and battery bank.

I would suggest a bit of reading to guide your design decisions:

Energy Audit - Watt For? - JdFinley.com

https://handybobsolar.wordpress.com/

https://www.solarpaneltalk.com/forum/off-grid-solar

https://www.solarpaneltalk.com/forum...your-batteries

https://www.solarpaneltalk.com/forum...tteries-part-2
I know that handybob gets a lot of credit, but I can't stand reading his rants (which are all he writes). There's so much stuff that he references which I simply will not get because he's so deep in the industry.

I digress...

So, I was afraid that would be the case, so that means that I'd need two MPPT charge controllers.

I've got a 12V inverter, so a 24V bank is less than ideal. I have no problem downsizing the bank size to 6 (?), which would be alright in parallel then? If I'm buying less batteries, I can buy another MPPT. The panels I got for a great price, so I'm stuck with 'em.

I do, handle heat well, but more than anything 5,000 btu is perfect for my setup.
__________________
Follow me at: facebook.com/derelictebus for more detailed information on the conversion.
Velocipedic is offline   Reply With Quote
Old 05-22-2018, 03:00 PM   #5
Bus Nut
 
Ninjakitty's Avatar
 
Join Date: Jan 2018
Location: Brevard County, FL
Posts: 273
Year: 1990
Coachwork: Bluebird
Chassis: Ford
Engine: 6.6 New Holland Dies
Rated Cap: 60 kids, 10 window
Check out this sizing tool.

http://www.midnitesolar.com/sizingTool/

I have 4x350 watt panels. I'll be running 2 pairs in series parallel. I have a MPPT Midnite Classic 200 that will support this.
__________________
Nick
Ninjakitty is offline   Reply With Quote
Old 05-22-2018, 07:53 PM   #6
Bus Geek
 
Join Date: May 2016
Location: Eastern WA
Posts: 2,501
Year: 2002
Coachwork: Bluebird
Chassis: All American RE (A3RE)
Engine: Cummins ISC (8.3)
Rated Cap: 72
1) Don't buy anything else until you have a proper design completed.

2) Read, study and learn.

3) Perform a thorough energy audit.

4) Design a system that will serve your needs. We will help you with this.

5) Now that you know what you need, buy the components that you need to complete the system you designed to serve your needs.

If you insist on installing 5 panels in parallel and keeping your 12v inverter you may find yourself with a system that does not meet your expectations. I'm not trying to be harsh. You kind of got ahead of yourself when you bought components for a system that you had not designed yet.
PNW_Steve is offline   Reply With Quote
Old 05-22-2018, 10:15 PM   #7
Skoolie
 
Join Date: Oct 2017
Location: Texas
Posts: 120
Year: 1992
Coachwork: Ward Senator
Engine: 7.3
Rated Cap: 78
The panels won’t be in parallel. The batteries would originally have been. The inverter is the limiting factor for the batteries. I could do more batteries at 6 volt wired in series/parallel. I was at roughly 13% amp output to battery capacity. My energy audit left me with a daily usage of no more than 70ah.

What would not meet my expectations as planned? The usable amp hours?
__________________
Follow me at: facebook.com/derelictebus for more detailed information on the conversion.
Velocipedic is offline   Reply With Quote
Old 05-23-2018, 06:41 AM   #8
Bus Nut
 
JDOnTheGo's Avatar
 
Join Date: Feb 2017
Location: The West
Posts: 621
Year: 1998
Coachwork: MCI
Chassis: 102 EL3
Engine: DD 60
Rated Cap: 50k
To your most recent question, a long parallel string of batteries is almost guaranteed to work "poorly" due to the long string and nature of how batteries work (basically). I am a little less suspect of properly connected parallel battery installations. Read this. I am not an EE and the largest lead-acid bank I have ever worked with was four batteries so no experience with a large one. I started down the path of creating a large lead-acid battery bank (12-14 batteries) and quickly decided that lithium was an easier/better option. It does come at a price though.

Quote:
Originally Posted by Velocipedic View Post
It will feed at 12V at 130A to the battery bank.
As already noted, The Morningstar TS-MPPT-60 controller will limit its output to 60 amps (regardless of the voltage). Bumping up to a 24VDC battery bank is very helpful in this regard (twice the 'bang' from the controller).

Quote:
Originally Posted by Velocipedic View Post
The battery bank will be monitored via this Tristar readout.[/URL]
The charge controller (panel/meter) does not monitor the battery bank. It may monitor voltage but that is a poor indication of SOC. To have decent info, you need a battery monitor that watches all of the electrons flowing into/out of the bank using a shunt. We seem to mention this repeatedly - generally I mention the Victron (ok) and Trimetric (better); Steve mentions using a hydrometer (best but most inconvenient).

Quote:
Originally Posted by Velocipedic View Post
My plan for boondocking is to not have a generator. My plan if my solar system fails is to get to an RV park and hook shore power into the inverter.
It must be an inverter/charger? I don't have a generator and spend nearly all my time boondocking. The idea of living (normally) using only power from the sun is very realistic. Obviously, there are many factors that can effect this.

Quote:
Originally Posted by Velocipedic View Post
My energy audit left me with a daily usage of no more than 70ah.
70ah at 12VDC?? This sounds off a bit - especially if you have a refrigerator. This is a very small bit of power at 12VDC, obviously twice as much at 24VDC but still not a lot for the size of system that we are discussing. My refrigerator alone (it is a big one) uses nearly twice that much each day (120Ah).

Follow Steve's advice - it is rock solid!
__________________
JD - Full timer out west
Missy - 1998 MCI 102-EL3 - 1.7kW Solar - 10kWh Lithium
My Adventures & Build
JDOnTheGo is offline   Reply With Quote
Old 05-23-2018, 10:01 AM   #9
Skoolie
 
Join Date: Oct 2017
Location: Texas
Posts: 120
Year: 1992
Coachwork: Ward Senator
Engine: 7.3
Rated Cap: 78
Right, so two MPPT's to feed into the bank. So I've looked for battery bank configurations and would have 12 6V's wired in series, to make 6 12V's with approximately 1200aH (maybe less?)... is this what you're suggesting?

Trimetric battery monitor. Copy.

It is an inverter/charger. Best of both worlds, but limited to 12V DC input.

I'll have a tiny mini-fridge. Most of the time I don't have stuff in my fridge anyway, so I unplug it. The A/C will only be used infrequently during the day (since I work away from home), so daytime on weekends only, with fans as needed during the night. During the winter, possibly electric blankets. TV/Electronics at a minimum, with a few LED lights. A hairdryer if/when I ever have a girlfriend.
__________________
Follow me at: facebook.com/derelictebus for more detailed information on the conversion.
Velocipedic is offline   Reply With Quote
Old 05-23-2018, 12:09 PM   #10
Bus Nut
 
JDOnTheGo's Avatar
 
Join Date: Feb 2017
Location: The West
Posts: 621
Year: 1998
Coachwork: MCI
Chassis: 102 EL3
Engine: DD 60
Rated Cap: 50k
Quote:
Originally Posted by Velocipedic View Post
Right, so two MPPT's to feed into the bank.
If sticking to 12V battery bank, yes. Be sure you have the type that can be "networked" - or whatever the right manufacturer term is so they work together.

Quote:
Originally Posted by Velocipedic View Post
So I've looked for battery bank configurations and would have 12 6V's wired in series, to make 6 12V's with approximately 1200aH (maybe less?)... is this what you're suggesting?
No, I'm not suggesting that. I agree with Steve that a big lead-acid battery bank is generally a bad idea (not optimal for our typical RV style use). However; if you are going to do it, look closely at the connection information in the link I provided.
__________________
JD - Full timer out west
Missy - 1998 MCI 102-EL3 - 1.7kW Solar - 10kWh Lithium
My Adventures & Build
JDOnTheGo is offline   Reply With Quote
Reply

Tags
air conditioning, charge controller, design, electrical, solar

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 02:12 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2018, vBulletin Solutions, Inc.