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Old 05-17-2007, 08:22 AM   #29
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Originally Posted by campadk
Interesting thread.

After a week without hookups, I was disappointed to find on our new unit that I had to run our generator for 4-5 hours a day just to keep the batteries topped up! There isn't much load on the generator at all except for the first 10 seconds or so, and measurements show the recharge current is only about 5 or 6 A. A good 3 stage should charge initially at a much higher current and eliminate having to run the generator so long.

I am considering a Progressive Dynamics 3 stage converter/charger and the Xantrel Link 10.
a 3 stage charger will definitely make a difference in battery charging.

concerning charging, one thing i don't know if you are aware of (i wasn't) is that, even with a 3 stage charger, generator charging is only efficient to charging a battery to around 80% charge. the reason is once a battery gets to 80% it will only accept so many amps (absorption stage). so, while a 3 stage charger will get your batteries to 80% relatively fast during the bulk stage, the last 20% will take a long time (solar systems, i understand are the best choice for charging that last 20%).

for generator charging, the "managing 12 volts" book recommends to use the batteries to 50% or so, then charge to 80% to minimize your generator usage. to keep the batteries healthy, once a week or so, fully charge the batteries to 100%.

what this means is you really only get about 30% of your total Ah battery capacity during regular use, so when figuring out your battery capacity, you really need 3 times the capacity of your calculated Ah requirements. since Airstreams are typically pretty limited on battery capacity (space and weight), frugal electric use is the key to long-term boondocking. jk
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Old 01-25-2010, 01:56 PM   #30
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This may sound dumb, but I would just like to know how to tell if the batterys are fully charged? Without Them with a Hydo. How accurate is the Panel Indicators? Is their a more accurate meter I can install on the Panel?
Charlie
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Old 01-26-2010, 10:41 AM   #31
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Originally Posted by charlie g View Post
This may sound dumb, but I would just like to know how to tell if the batterys are fully charged? Without Them with a Hydo. How accurate is the Panel Indicators? Is their a more accurate meter I can install on the Panel?
Charlie
I would like to understand this as well. I found the LED panel on my 2007 AS to be frustratingly coarse. I bought a 12v meter that plugs into a lighter socket from Camping World and that provides a more granular reading. Still, what do these numbers mean in terms of 50%, 80%, 100% and charging rate and so low as to damage the batteries and so on? Also, the voltage numbers are somewhat higher while charging, falling immediately when the generator is shutdown. What should we expect from voltage while charging vs voltage while discharging?
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Old 01-27-2010, 12:04 PM   #32
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I remember when I was somewhat younger, the cars had a "Amp Meter" rather than a "Volt Meter", which doesn't tell me a damn thing. I wonder if I mounted a "Volt" and a "Amp" meter on my Monitor Panel, would it give more or better Information, as to the condition of the "Charging System" and the "Batterys"?
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Old 01-27-2010, 05:06 PM   #33
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I have this installed:
TriMetric Battery Monitor
It will answer these questions.

I have also heard good thinks about this family of products:

Link 20

There is/was a link 10, somewhat less expensive I think.
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Old 01-28-2010, 06:41 AM   #34
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There has been lots posted on monitor devices in various threads.

I agree the monitors in the Airstream don't tell you much, neither do voltmeters or amp meters.

I have a Link 10 monitor that I installed that tells me everything I need to know which mainly boils down to how much I use daily (amp hours) and how much I put back in charging via our generator. So if I use up 25AH one day, I try to put back 25AH with the generator the following day.

Of course it shows battery voltage and current (amps) which is useful to monitor what items are sucking all the power. It also is a great device for checking whether you have forgot to turn something off that might slowly discharge the batteries.

For anyone who boondocks, I wouldn't go without a Link 10 (or similar monitor).

Besides the fact that the system monitor (Micro Pulse) that comes with the new Airstreams is very vague in regards to the state of the batteries, it is also pathetically slow (toggle the status button and wait for it to reset and slllooowwwly scan each system). Its like something out of the 1980's!
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Old 01-28-2010, 06:54 AM   #35
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Below is a chart that corresponds volts and specific gravity to level of charge. To be accurate, when measuring volts, the battery cannot be under a load (voltage will measure low) or within 15 minutes of charging (voltage will measure high).

Volts Sp. Gr. Charge
12.6 1.265 100%
12.4 1.225 75%
12.2 1.190 50%
12.0 1.155 25%
11.8 1.120 0%

An amp meter is valuable for telling you how much power you are using but will not give you the state of charge of the battery(s).

Highly recommend the Trimetric Battery monitor, available from BestConverter.com if you really want to accurately track your battery power and usage. I live in my trailer and am boondocking 80% of the time. The Trimetric or a similar battery monitor is an invaluable tool to keep accurate track of your battery usage, state of charge, power remaining, etc.

Also recommend the book Managing 12 volts for an in depth understanding of how your battery works and how to manage it. I knew next to nothing about living off 12 volts before I got this trailer and this book really helped. There are other resources available on the web as well. jk

Hope this helps.
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Old 01-28-2010, 10:49 AM   #36
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Volts Sp. Gr. Charge
12.6 1.265 100%
12.4 1.225 75%
12.2 1.190 50%
12.0 1.155 25%
11.8 1.120 0%
I'm not disagreeing with the above stats but obviously a battery can be below 11.8v. Interior lights and stuff will still work albeit a bit dim. My 12v>110 inverter has an alarm that sounds when the voltage hits 10.5. What does this all mean?
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Old 01-28-2010, 11:51 AM   #37
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I'm not disagreeing either, but I agree with Lumatic. According to that chart (as measured by voltage) I almost always take my batteries below zero before charging, and I'm not sure I can get them past 50% even when on shore power overnight. I just don't see how those numbers can be right, although I have to admit I am constantly disappointed by my batteries' performance. So maybe something in my system is hosed.
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Old 01-28-2010, 03:41 PM   #38
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I'm not disagreeing with the above stats but obviously a battery can be below 11.8v. Interior lights and stuff will still work albeit a bit dim. My 12v>110 inverter has an alarm that sounds when the voltage hits 10.5. What does this all mean?
I believe those voltages are for batteries without load. If the battery has a load on it you will get lower values. You need to remove all loads, then measure voltage.
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