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Old 04-10-2015, 11:01 AM   #29
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Originally Posted by timhortons View Post
there really seems to be conflicting information on the battery subject. Here's weird, at least to me ... My system goes to a higher final voltage charging off my TV than the converter from the AC/120-30 AMP hookup

can these batteries be fully discharged and recharged ? should they be for some sort of winter deep storage as described ? are they marine grade or hybrid marine/auto ? if you're in "Store" will the propane detector still run them dead in 2 weeks and "ruin" your battery anyways ?

Should you plug in a trailer you are storing in if you can, or only after you buy the magic "magnum" charger ? Or plug it in for short periods ? How long ?

it's a crap sandwich of contradictions to me.
The subject of batteries, chargers and charge/discharge cycles is confusing, and full of ifís andís and butís.

Let me add to the confusion with the hope of helping, but no guaranteeís.

Your TV alternator regulator is not the same as the one in your trailer converter/charger so the voltages will not be the same. The TV regulator is part of the computer regulated electrical package designed for the TV itself. When you connect it to the RV, the RV gets what the TV alternator regulator (computer) thinks is appropriate for the TV battery and electrical system. The RV connection is just along for the ride (no pun intended). Since the RV batteries are not really connected to the TV very much, whatever the TV supplies will probably not either help or harm the RV batteries. It will give them some charge while you tow.

Any lead acid battery should remain as fully charged as possible for as much of itís life as possible. The general recommendation is to not discharge a flooded cell battery to less than 40 to 50 % of itís total capacity for reasonable life. Yes, you can fully discharge a lead acid battery totally, and recharge it, but in doing so you put a huge strain on itís total number of ďcyclesĒ that is how often you can do it. You can cycle a lead acid battery a lot of times between 80 and 100% but very few times between 0 and 100%. This is especially true of the thin plate starting type batteries and also the compromise ďmarineĒ starting/deep cycle batteries. True deep cycle batteries such as golf cart types can stand more total deep cycles, but are still harmed by doing so, and total cycles are considerably limited.

And, if you leave a battery discharged to zero for any length of time (days or weeks) your chances of bringing it back to full charge and capacity are very slim. In addition, leaving a battery at say half charge (cycling between say 40 and 60% full) will cause damage and you will never be able to restore it to 100% capacity. This problem may take longer to develop but batteries should never be left at low levels of charge for weeks or months. Batteries are fussy!

The batteries I have seen supplied by Airstream are a variety of the compromise starting/deep cycle type. They are reasonable, but not great batteries for their use. AS supplies a different AGM battery for trailers equipped with their solar package. It may be a better quality battery, but I have no real experience with it.

The USE/STORE switch does not shut off all items in the trailer but certainly you should be able to use it for shorter shutdowns of up to a month without significant battery compromise. Several months is where the problem occurs. The Propane detector takes some current, but will not discharge your batteries in two weeks. For long term storage though, complete battery disconnect is the best policy.

Does your Sport have one or two batteries? With only one everything is even more critical as you have only half the capacity.

There are much better converter/chargers than the ones Airstream typically supplies. You can get them in the range of $200. The Magnum is a good unit, but far from the only one available. It is an inverter as well as a charger, but not everyone needs or wants an inverter. Progressive Dynamics makes a good three stage unit, as do several other manufacturers.

I thought I read somewhere that the only 3 stage converter/charger that AS supplied as original equipment was an off shore manufactured unit (maybe WFCO) put into the 16í Sport. I may be dreaming that, or the person who said it might have been in error, but based on that memory, you might even have a 3 stage unit in your rig.

I would not leave a single stage charger equipped Airstream plugged in 24/7 for weeks and months. If you do, check the water level in the batteries frequently, like every couple of weeks until you get a feel of the water usage for your unit. It can vary a lot.

You also could put a timer on the input to your trailer and have it come on for a little bit each day if you want. But unless you have accidentally left something on, your batteries donít need a constant charge/recharge and turning it on every couple of weeks to a month will be OK. If you leave something on, however, all bets are off.

I hope that helps you out a little.
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Old 04-10-2015, 11:33 AM   #30
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Thank you idroba, my plan for now is just to use it and see what happens.

The sport indeed has 1 83AH 12V battery that is supposedly somewhat deep discharge capable. I mean if it isn't, it shouldn't really be called an 83AH battery, should it ? After I destroy it, I may invest in an AGM lifeline of same rating with the intention of running it harder.

I'm not sure I fully understood everything you said about TV charging, I know there's a diode to prevent it reverse charging/draining when the TV is off, but I sort of assumed the voltage is whatever my cars' alternator puts out, which happens to be around 13.7V I guess. I was told the charge rate towing was about 10A, but is seems slightly higher than that.

two more questions for the intertubes:

- Does the factory 120V charger converter really just charge all day long till your batteries melt ?

- If I had solar, but no plug in where I store my AS outside for long periods would I be okay to leave it in USE position, with fans, lights and appliances turned off ? I know switching to use adds battery drain from the radio, to the parasitic draw from the detector, but would solar be able to keep up with that. Would there be any battery consequences of a very light charge drain over a long period of time say 93 to 100% cycle . The idea would be to leave a cell phone in there on USB for lojack purposes.

- Skipping the Generator altogether and using a TV as charging. I'm sure it's not the most efficient, but if I just plug in leave my TV running for 2 hours in the morning or afternoon to top up the solar charge if needed, can I forgo carrying around another 1k generator, fuel bottles, filling, mixing oil, cables and spilling, etc for light boondocking ? Or will I die of CO poisoning while I make breakfast?
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Old 04-10-2015, 01:18 PM   #31
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Ok, a couple of more comments:

The rating system of batteries is what It is. May not be the best, or most accurate, so that is why we try to ‘splain why you should not use your battery down to zero charge.

You will damage the AGM battery too, if you try to use it too hard. They are generally built better, but are not a miracle battery. Your “investment” will not pay back abuse.

The TV alternator voltage is controlled by temperature and load on the vehicle, as determined by the design parameters of the manufacturer. The voltage will vary and so will the charge rate available for charging the RV battery. On my Jeep and 2014 FC 20’ when the batteries are low after a boondocking time, I can get in the range of 10 to 12 amps charge. When the batteries are not as far down, it is lower. The same Jeep, and my old Argosy, seldom goes over a 6 amp charge.

The original converter/charger has a fixed voltage point which in theory will not overcharge the battery(s) but in actuality can under a number of conditions, especially as the temperature varies. The battery will not “melt” but if it evaporates the water in the cells, and it is not replenished promptly (no plates become exposed) the battery may develop internal shorts as the plates touch each other. In all the trailers I have had with all the single stage charging systems, this happened once to me. There was a strong smell of “battery” and it got hot and was of course irreversibly damaged. After that, I did not leave my converter/charger on 24/7 anymore, but manually controlled it. It is not something which will always happen, many have used their trailers and left them connected for long time periods with no problem. But it does happen a lot more commonly with a single stage charger, and almost never happens with a multi stage charger. So, if you want to pug and forget it, a multi stage charger is a better deal.

A solar system automatically has a better managed charger system, and, if you have the sun, will keep things up very well with the loads you mention.

You can use your TV for a charge system as you mention, but it is not very efficient. In the old Airstream manuals, what you propose was what they said to do to keep your battery charged.
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Old 04-10-2015, 06:20 PM   #32
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A quick note on battery charging from your TV. Of you intend to install Lifeline AGM batteries, the factors recommends that you DISCONNECT any voltage coming thru the trailer umbilical charge line before it reaches your Lifeline batteries.

The factory states that the constant 14.2 VDC output from the alternator reaching your Lifeline deep cycle batteries will overcharge them due to not allowing them to 'float' charge at 13.2-13.4VDC when full. In fact, they day that they will not cover warranty claims due to improper charging from a vehicle alternator.


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Old 04-10-2015, 07:07 PM   #33
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Quote:
Originally Posted by lewster View Post
A quick note on battery charging from your TV. Of you intend to install Lifeline AGM batteries, the factors recommends that you DISCONNECT any voltage coming thru the trailer umbilical charge line before it reaches your Lifeline batteries.

The factory states that the constant 14.2 VDC output from the alternator reaching your Lifeline deep cycle batteries will overcharge them due to not allowing them to 'float' charge at 13.2-13.4VDC when full. In fact, they day that they will not cover warranty claims due to improper charging from a vehicle alternator.


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so the AGM "upgrade" kills TV charging ? that's crappy. they should fix the design, even if they have to drop/step down anything over the max charge voltage in a z-diode circuit of some kind.

how would they know ? my AirForums posts ?
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Old 04-10-2015, 07:59 PM   #34
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so the AGM "upgrade" kills TV charging ? that's crappy. they should fix the design, even if they have to drop/step down anything over the max charge voltage in a z-diode circuit of some kind.

how would they know ? my AirForums posts ?
This is specific to Lifeline AGM batteries (and the new lithium battery packs as well). Lifeline has been dealing with this issue for many years. Alternators are great for maintaining voltage to run an engine and keep your STARTING batteries charged, but suck at placing proper required charge to a deep cycle battery that requires a 'float' charge once full.

There are several ways around this. One is to add a separate battery charging and regulator system from Balmar....they have a very large presence in the marine industry and have many components that allow for proper battery charging in a marine environment.

Next is to use a BIM (battery isolation manager) system like the new Airstream Interstates use. These have a voltage sense circuit and large solenoid that automatically combines disparate battery banks when a charging source is detected and one of the banks is at 80% depth of discharge or below. The solenoid is then disconnected after both banks are at full charge for one hour and the monitoring begins again.
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Old 04-12-2015, 09:46 AM   #35
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battery disconnect switch has no impact on jack

a long while back in the thread it was mentioned that the battery disconnect switch cuts power to the trailer jack. My trailer does not work this way - just went and checked it. My trailer is 2013 FC 30.

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And that adds just a little bit more security from being stolen as it would take the thief longer to do it manually.
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Old 04-12-2015, 10:32 AM   #36
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a long while back in the thread it was mentioned that the battery disconnect switch cuts power to the trailer jack. My trailer does not work this way - just went and checked it. My trailer is 2013 FC 30.
Same on my 2014 FC 20'. Jack is wired directly to the battery via a 30 amp fuse.
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Old 04-13-2015, 08:59 PM   #37
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Just back from taking Bambi 2 on the road for 6 weeks of travel. We stopped by Airstream of Spokane for a visit with Doug the Mechanic re: this 'n' that. He recommended two 6-volt batteries as having the longest boondocking capabilities.
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Old 04-13-2015, 09:35 PM   #38
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Just back from taking Bambi 2 on the road for 6 weeks of travel. We stopped by Airstream of Spokane for a visit with Doug the Mechanic re: this 'n' that. He recommended two 6-volt batteries as having the longest boondocking capabilities.
That's a good starting point, but there are many alternatives with far more sustained energy density.....like larger AGM 6VDC units and........ lithiums.
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Old 11-11-2015, 02:54 PM   #39
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Lightbulb TV will not charge Trailer batteries if TV Voltage falls much below 14V

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....Also if the tow vehicle charges the battery, my bambi battery was dead after towing north from Florida so that doesn't make much sense. Jeff T Madison WI
In nearly all modern vehicles, the alternator uses Voltage measured on a "Sense Wire" to judge whether the TV Battery is fully charged. Right after you start your truck (or SUV), the Alternator will use high voltage - 14.4 to 14.6V - to recharge the battery. But after a while, the alternator's controller will find the battery adequately recharged, and it will drop the alternator's output Voltage to a "float voltage" level. (In my own vehicle, the Voltage drops to about 13.6V.) This constitutes an "intelligent battery charger", and also raises gas mileage by running the alternator with less resistance.

First, let's view this from the perspective of the Trailer Batteries. As you know, there is a gap between "discharge voltage" (12.8 and lower) and "charge voltage" (13.2 and higher) on Lead-Acid batteries. *IF* the Voltage actually held up at 13.6V, there would be a tiny amount of charge going into the TV batteries, and also running the Airstream Refrigerator. That's not enough to re-charge low batteries, it's only enough to "maintain" them with Float Charging. To re-charge discharged batteries in a reasonable amount of time, you need at least a "Bulk" charge Voltage - something more than 14.2V (and more typically, 14.4V).

But next, let's look at the load created by the Fridge. When an absorption Fridge heater is running on electricity, it will draw over 10A. (With the bigger models of refrigerators, way over 10A). Your Pickup truck battery is creating only 13.5V. From there, "skinny wires" from the alternator, through the Bargeman, to your DC Distribution panel, and then to your batteries have increasing "Voltage Drop" whenever the amount of current goes up. When the current draw is high - it could easily lead to voltage along the Tow Vehicle wiring path to fall below 12.6V, 12.4V, or even 12.2V - unless the Fridge is connected to another power source at higher voltage.

Which it is, of course. Nearly all of the power which the Fridge uses (along with anything else running off 12V, or 12V->120V converters) will pull from the Trailer Batteries first. They won't be charged by the low Voltage TV supply, they'll be discharged from the loads.
- - - - -
The problem can be solved by purchasing a "Voltage Boost" Trailer Charging devices (from Redarc, or Ctek), or doing an equivalent "home-built" device from separate parts. What they all do is consume LOTS of TV power through the Bargeman, even at lower voltages, and then they "boost" the Voltage inside the Trailer to the appropriate Voltage for battery charging. (According to the current "State of Charge" in the Trailer batteries.) And, because they pull lots of power, they can also provoke the Tow Vehicle Alternator to "Sense" low voltage in the TV, and increase it's power output back to a higher supply level.

The "home built" parts are: a high-amperage 12V->24V "boost" device ($60-90); feeding a pair of extremely small 12V batteries in Series ($30), feeding a Solar Charge Controller ($40-60).
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Old 11-11-2015, 03:20 PM   #40
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Red face A switch to AGM batteries will not solve "the problem".

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A quick note on battery charging from your TV. Of you intend to install Lifeline AGM batteries, the factors recommends that you DISCONNECT any voltage coming thru the trailer umbilical charge line before it reaches your Lifeline batteries.

The factory states that the constant 14.2 VDC output from the alternator reaching your Lifeline deep cycle batteries will overcharge them due to not allowing them to 'float' charge at 13.2-13.4VDC when full. In fact, they day that they will not cover warranty claims due to improper charging from a vehicle alternator.

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Few (if any) modern SUVs and Pickup trucks currently equipped with alternators generating "constant 14.2 VDC output", because a scheme that stupid would also cook the TV Battery. They adjust output power and Voltage downwards, according to TV Battery "State of Charge", using a "Voltage Sense" wire and an internal (or external) controller unit.

But your post is making an important point: if you switch from SLA to those particular AGM batteries, you need to set ALL of your charging devices to respect the lower voltage requirements: external chargers, the Converter, and any "TV Charge Controller" devices which will actually charge the batteries.

By charging at a lower voltage, these particular batteries can slightly "mask" the problem (i.e., "Failure to charge from TV"). But the problem of unmanaged, Low Voltage input from the Bargeman 12V is not directly addressed by this very expensive change, so I'm labelling this "solution" as a non-starter (for this particular problem).
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Old 11-15-2015, 07:22 AM   #41
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Few (if any) modern SUVs and Pickup trucks currently equipped with alternators generating "constant 14.2 VDC output", because a scheme that stupid would also cook the TV Battery. They adjust output power and Voltage downwards, according to TV Battery "State of Charge", using a "Voltage Sense" wire and an internal (or external) controller unit.

But your post is making an important point: if you switch from SLA to those particular AGM batteries, you need to set ALL of your charging devices to respect the lower voltage requirements: external chargers, the Converter, and any "TV Charge Controller" devices which will actually charge the batteries.

By charging at a lower voltage, these particular batteries can slightly "mask" the problem (i.e., "Failure to charge from TV"). But the problem of unmanaged, Low Voltage input from the Bargeman 12V is not directly addressed by this very expensive change, so I'm labelling this "solution" as a non-starter (for this particular problem).

I don't know how you are measuring the voltage coming from your alternator, but using a Scan Gauge II in my 2011 Sprinter service van, the indicated DC system voltage is always indicating 14.1-14.2VDC any time I look at the gauge, which is often.

Do you have any empirical data to back up your blanket statement? The folks at Lifeline seem to feel that this situation has enough significance to address it directly.


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Old 11-16-2015, 02:05 PM   #42
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Yes, I have taken measurements. But you are obviously right, too.

I have not measured any GM equipment or full-sized vans. (But my next-door-neighbor owns a Chevy Tahoe, which I can check out if you'd like me to: just send a PM.) Many or most "Full Size Vans" may work exactly as yours does, with constant voltage (and perhaps no external "battery sense" connector at all). Although I don't know why those vehicle designers would want to cook their their batteries, when the "solution" has been in use for 20+ years. (?)

I have measured on several "midsize" and "fullsize" SUVs, small pickups, and regular cars in the neighborhood (while doing other bits of electrical work, and more recently - to specifically confirm my suspicions before posting). I found the alternator controllers (built into the OEM alternators) on midsize Toyota vehicles (4Runner, Tacoma) are especially aggressive at pulling down the voltage after sensing "good" battery SOC. Different alternators used in Subarus, and some Fords, also do the Voltage Drop, but do not take it down quite as far. (Those "little" Subarus are not capable of towing AirStream trailers, but the sense-based Voltage Controller technology is also used there).

I know people who have used another, very simple trick to push under-the-hood voltage back up (for the "problem" of insufficient Bargeman Voltage): To help with Refrigerator DC Loads and Trailer battery charging while travelling, those guys put a diode at the end of the "sense" wire, creating a voltage drop of about .5V along the path to the controller. That trick causes the alternator's controller to "see" an undercharged battery at all times, and respond by crank the output Voltage (and Amps) way up. But unlike Redarc, Ctek, and the homebuilt, the trick puts all of the batteries at a risk of being overcharged (if the diode is left in place for "too long").

Thanks!
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