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04-18-2014, 10:53 PM
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#21
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Senior Member
Join Date: Feb 2013
Location: Santa Rosa County, Florida
Trailer: 2014 Escape 21 Tow: 2024 Toyota Tundra
Posts: 3,097
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Steve's mention of his inverter reminded me of another question. I have the 1500W inverter supplied by ETI. I'm unfamiliar with inverters as well. Do they run full-tilt no matter what is plugged into them, or do they respond to load? That is, do they draw the same amount of battery power whether you are running a microwave or maybe a device that uses only 60W of A/C power?
Mike Lewis
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04-18-2014, 11:05 PM
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#22
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Senior Member
Join Date: Feb 2010
Location: Phoenix Metro Area, Arizona
Trailer: 2014 Escape 19
Posts: 767
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Quote:
Originally Posted by Mike Lewis
Steve's mention of his inverter reminded me of another question. I have the 1500W inverter supplied by ETI. I'm unfamiliar with inverters as well. Do they run full-tilt no matter what is plugged into them, or do they respond to load? That is, do they draw the same amount of battery power whether you are running a microwave or maybe a device that uses only 60W of A/C power?
Mike Lewis
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When turned on they draw some battery power with no AC load. Their power draw from the battery is roughly a linear function of the load - more AC power uses more DC power.
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04-18-2014, 11:10 PM
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#23
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Senior Member
Join Date: Feb 2013
Location: Santa Rosa County, Florida
Trailer: 2014 Escape 21 Tow: 2024 Toyota Tundra
Posts: 3,097
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Thanks Doug. In that case I'll try to use it soon, with a small load.
Mike Lewis
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04-19-2014, 12:26 AM
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#24
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Senior Member
Join Date: Aug 2012
Location: Portland, Oregon
Trailer: 2002 Escape 13'
Posts: 967
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Mike, my inverter draws 1.4amps with no load just because it is turned on but then the current draw is proportional to the actual load placed on the inverter + some loss factor. Consequently, I always keep it completely turned off when not in use. Because of the power loss related to voltage multiplication and sine wave generation, devices hooked to the inverter actually draw more power than their label states. For example, with my inverter, a 600 watt microwave actually draws 940 watts from the inverter. Because of this loss I use a fairly large inverter to meet any need that may arise...we never know how many margaritas may be needed at a moment's notice while simultaneously grilling some much needed bacon on the electric grill and charging my electronic toys while running my toaster!
Steve
Quote:
Originally Posted by Mike Lewis
Steve's mention of his inverter reminded me of another question. I have the 1500W inverter supplied by ETI. I'm unfamiliar with inverters as well. Do they run full-tilt no matter what is plugged into them, or do they respond to load? That is, do they draw the same amount of battery power whether you are running a microwave or maybe a device that uses only 60W of A/C power?
Mike Lewis
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04-19-2014, 08:20 AM
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#25
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Senior Member
Join Date: Feb 2010
Location: Phoenix Metro Area, Arizona
Trailer: 2014 Escape 19
Posts: 767
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Quote:
Originally Posted by hotfishtacos
Mike, my inverter draws 1.4amps with no load just because it is turned on but then the current draw is proportional to the actual load placed on the inverter + some loss factor. Consequently, I always keep it completely turned off when not in use. Because of the power loss related to voltage multiplication and sine wave generation, devices hooked to the inverter actually draw more power than their label states. For example, with my inverter, a 600 watt microwave actually draws 940 watts from the inverter. Because of this loss I use a fairly large inverter to meet any need that may arise...we never know how many margaritas may be needed at a moment's notice while simultaneously grilling some much needed bacon on the electric grill and charging my electronic toys while running my toaster!
Steve
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The Go Power 1500 is 85-90% efficient according to the manual. This means an appliance actually drawing 1000 watts AC will require 1111-1176 watts DC or 93-98 amps. If run for 1/2 hour it would use 46-49 amp hours from the batteries.
BUT microwaves are rated differently - by the cooking power, not the input power. So our 700 watt ETI installed microwave actually requires just under 1000 watts AC (8.3 amps according to the specs.)
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04-19-2014, 11:41 PM
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#26
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Member
Join Date: Nov 2012
Location: Forks, Washington
Trailer: Working on my build list
Posts: 93
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To get accurate reading of the battery state of charge using either a voltage meter or a hydrometer the batteries need to be disconnected and allowed to rest. This tends to be impractical in an RV. A amp-hour meter is the best solution. A good one will measure current coming out, current going in with an adjustment for the charging inefficiency of the battery, and be adjustable for the loss of capacity as the battery ages. A bad (cheap) one isn't worth the cost since it will lie to you. There are several on the market that will do the job.
If you like to camp away from hookups, consider making one your first purchase in an electrical system upgrade. Then go camping and watch it as you live normally. It will tell you what else you need and just as importantly what you don't need. It will also help ensure you don't overdraw, under charge, or over charge the batteries which shortens their life. That will save you money in replacement costs.
As for wire length, it is from the alternator to the batteries. You can't easily change it. Length, size and voltage drop are mathematically related. Decide what voltage drop is acceptable, measure the length and use an online calculator or table to find the smallest wire that will do the job.
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04-20-2014, 07:42 AM
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#27
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Senior Member
Join Date: Jun 2010
Location: Central, Pennsylvania
Trailer: Escape#5 2022 E19
Posts: 26,268
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Very concise explanation, WestEnder, thank you.
__________________
Jim
Sometime life gets in the way of living.......
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05-08-2014, 09:41 AM
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#28
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Senior Member
Join Date: Jul 2012
Location: Burlington, Vermont
Trailer: 2014 17b/ 2012 Chevy Colorado
Posts: 736
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WestEnder et all.
How, exactly, do you use a multi meter to assess 2 6v system? Do you place leads on the positive and negative terminals of a single battery, or, because they are in series, do you have to place one multi meter lead on the postive terminal of one battery and the other lead on the negative terminal of the second battery?
Also, a poster in another thread recommends this tester.
Amazon.com: INNOVA 3721 Battery and Charging System Monitor: Automotive
Any thoughts from this group about this item?
Thanks,
Nick
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05-08-2014, 11:58 AM
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#29
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Senior Member
Join Date: Feb 2010
Location: Oswego, New York
Trailer: 2017 Escape 21C, 2018 Ford F150
Posts: 5,363
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It depends on what you want to measure. Across one battery you should get a bit more than 6V, across the positive & the negative connections from the pair to the trailer you should get nominal 12V...
Many users are happy with the plug in meter. I prefer a monitoring system such as the Bogert Industries TriMetric 2025, however it is far more expensive, and requires installation.
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05-09-2014, 01:24 AM
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#30
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Member
Join Date: Nov 2012
Location: Forks, Washington
Trailer: Working on my build list
Posts: 93
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Measure as Jon said. To determine state of charge of the batteries, do it with no input/output on them and the batteries rested. The rested part is the hardest in an RV since we tend to be using them frequently and this will make the reading inaccurate. Get a table of voltages off the internet, preferably from the manufacturer of your batteries since they will understand the chemical and physical properties of the batteries the best. That will give you the charge of the batteries.
Measure at various points on your trailer to see if you are losing voltage anywhere.
To see what your charging system (solar, charger from shorepower/generator, alternator, etc.) is putting out, do it with the charging system connected and operating.
I'm a believer in battery monitors. In exchange for a little more money and an investment of a little of your time in learning to understand what it is saying, you will get a lot more information. If you can use one to figure out what you need, avoid spending money on stuff you don't need, and prolong the life of your batteries you will save the cost many times over. This is not a place to cheap out. New batteries are much more expensive than a good monitor. If you abuse batteries you will be buying new batteries much more frequently than if you treat them right. What is the difference between replacing your batteries every year and replacing them every 6 years? Good care and lots of money.
There is an excellent list of what's out there/poll of battery monitor ownership at the top of this thread on the CruisersForum. Unfortunately, the thread is long and wanders off topic but there is some discussion of people's experiences with various models. Which Battery Monitor ? - Cruisers & Sailing Forums
CruisersForum has a lot of good 12 volt threads as do many of the other boating forums. They have a number of 12 volt experts. I find them a good source of information. I should warn you however, they also have some opinionated non-experts so you have to be careful until you figure out who is knowledgeable and who isn't.
The best info I have seen on installing one is this: http://forums.hunter.sailboatowners.com/showthread.php?t=125606 . If you don't DIY it will at least tell you what is involved. The article also discusses what a monitor will show you. The rest of the thread is worth reading.
The Trimetric has a good reputation in the RV world. I've seen people write well of the Victrons and the Links. There are others that are well thought of too. Prices vary widely so shop around.
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