| [GMCnet] Electrical requirements questions - Newbie [message #245198] |
Wed, 26 March 2014 13:44 |
glwgmc
Messages: 1014
Registered: June 2004
Karma: 10
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Senior Member |
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Hi Randy,
It is simply not practical to run A/C off batteries and inverters. Starting amp draw will be close to or even exceeding 15 amps at 120vac for a short period of time. Running amp draw will be 12 to 15 amps at 120vac continuous depending on brand and BTU capacity of your A/C. 15 x 120 = 1800 watts. That means your batteries would have to be capable of continuously delivering 1800 /12 = 150 amps every hour of operation even if the inverter was 100% efficient (they are not, more like 70% to 85% depending on brand and honesty in labeling). A quality 12vdc battery will have a capacity of 90 (standard auto size) to 220 (8d size) amp hours of capacity. Given that battery capacity is usually measured at a 20 amp draw and with a heavier draw the amp hour capacity will drop significantly, and you can only draw down about 50% of the battery amp/hour capacity before greatly shortening its life, it is unlikely that even six 8d size batteries (which would weigh 1200 to 1500 pounds) c
ould keep just the A/C running for more than a few hours. You could not fit enough solar capacity on the roof to recharge that many amp/hours back into the batteries and a generator of significant size would have to be running full time to keep up. Better to just run the generator to run the A/C and eliminate the batteries and inverter from that task. Four Trojan size six volt batteries wired series/parallel will provide about 480 amp hours, plenty for boon docking with all loads other than resistance heat or large motors longer than your black tank and fresh water can hold out. You can download a presentation I have given to several GMC club rallies called "Living large in your GMC". That is available on the GMC page on my web site (http://jerrywork.com). That presentation will explain in some detail what you can realistically do and how to do it.
Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR
Visitors always welcome!
glwork@mac.com
http://jerrywork.com
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Message: 2
Date: Wed, 26 Mar 2014 09:45:20 -0500
From: Randy Meek <randallmeek@sbcglobal.net>
Subject: [GMCnet] Electrical requirements questions - Newbie
To: gmclist@temp.gmcnet.org
Message-ID: <3bd9b.5332e7ff@gmc.mybirdfeeder.net>
Content-Type: text/plain; charset="ISO-8859-15"
I am new to the whole RV experience, and looking to update/upgrade the 1978 Royale that I purchased. It is pretty much a blank slate, so the directions are boundless.
First question:
Assuming "boon-docking" was not an expectation, and if done would be accompanied with an external portable generator. Compressor type A/C a must, given I live in south/central Texas and the coast would be a common destination.
1. Would a bank of 4 to 6 quality deep cycle 12 volt batteries plus the house battery up front, be ample to run accessories and A/C unit while traveling?
2. Would some solar panels for in-route and passive charging be needed?
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Jerry & Sharon Work
78 Royale
Kerby, OR
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