Battery Disconnect Switch, Solar & AGMs

[SilverGate]

Originally Posted by SilverGate

Update: I continue to stand by the above statement and I continue to never intentionally use the switch in the disconnect position and I don't intend to get into a debate about this.
SilverGate

Update: I no longer stand by the above statement. When I had problems with my Parallax converter, I found that it was very useful in diagnosing my problem to turn the Battery Disconnect Switch to "Store" (which separates the battery power from the trailer). I then used a voltmeter on the converter DC output connections and found that it was producing insufficient power and needed to be replaced (twice!)

Just before replacing the Parallax converter with the Xantrex XADC 60A, I disconnected the AC shore power and disconnected the DC battery power to the converter by turning the Battery Disconnect Switch to "Store". (Note: although this worked for me, it is generally recommended that the batteries should be disconnected at the battery terminals to ensure safety.)

See: Parallax Converter Replacement with Xantrex

[RossFam05BH]

Hey All,

After reading the posts in this thread, I finally figured out why the batteries in our trailer never charged when connected to shore power. It is because the red LED when lit does not indicate the position of the solenoid when the trailer is connected to shore power. Therefore, I asked my 12 year-old son Alex to develop a electronic solution to this problem. He came up with the idea to use a CMOS 4013 flip-flop IC to control the lighting of new LEDS to indicate whether the battery disconnect solenoid is in the use (charging batteries) or store (not charging batteries) position. We drilled two holes in the face plate for surface mount LEDS and one for the toggle switch shown. In the pictures in this post, the trailer is connected to shore power. The blue LED indicates that the batteries are charging and the green LED shows that the batteries are disconnected.

So that the LEDS do not drain the batteries when off shore power, Alex included a DPDT toggle switch to cut power to the blue/green LEDS only. The toggle switch in the off position does not cut 12 volt power to the IC, thereby allowing the flip-flop to remember the solenoid's state.

In hopes that this will be useful to other Air Forum-ers, Alex has also included a photograph of the circuit board (attached with screws to the circuit board of the panel), and a circuit diagram. The brightness of the blue/green LEDS is easily adjusted by changing the resistance in series with the LEDS.


Bye,

Paul and Alex

[Ag&Au]

In my new 31D the battery disconnect is a large manual switch located next to the DC distribution panel under the front couch. As it is wired now, The batteries, converter output, and solar output are all tied together and the battery switch is between this common point and the distribution panel. Therefor when the battery switch is off, there is no converter power available for the 12 volt bus. I think this switch should be wired between the batteries and the common tie point. Anyone disagree? also I find no store/use switch near the door. I am guessing that I am not supposed to have one.
Thanks,
Ken

[Ag&Au]

Well,
I have discovered, after being directed to the diagram in the manual that it is wired correctly. My concern is, with it wired in that manner, will I stand the chance of overcharging the batteries, if I stay connected to shore power for a lengthy time.

[SilverGate]

Originally Posted by SilverGate

Thanks, Marc, for sharing your experiment and observations.

First, at least in my set-up when connected to shore power, the Battery Disconnect Switch red light is on (lit) no matter whether the switch is actually in "Use" (on) position or "Store" (off).
An audible click will be heard when switching from "Use" to "Store" and vice versa.

Second, for the record, my 2007 AS Owners Manual says:
"The disconnect switch is used to separate the batteries from the 12-volt distribution panel and converter charging system.

When the switch is turned "Use" (on) and the trailer is plugged into a 110-volt shoreline, the 12-volt distribution panel will receive power from the converter and the batteries will be charged through the converter charging system.

When the switch is turned to "Store" (off) and the trailer is plugged into a 110-volt shoreline, the 12-volt distribution panel will still receive power from the converter, but the batteries are disconnected from the system. The batteries will not be drained with the switch in the "store" position. The converter will not charge the batteries with the switch in this position.

The charge in the 12-volt batteries is replenished when towing from the tow vehicle alternator through the 7-way cord. This charge will go to the batteries no matter which position the Battery Disconnect Switch is in."

So, Marc, the Battery Disconnect Switch red light is not an indicator of whether the switch is actually in "Use" or "Store" position. The Battery Disconnect Switch needs to be on "Use" for your batteries to get charged when connected to shore power.

In my experiments, I found that the Battery Disconnect Switch does not separate my batteries from my Solar System (2, 53-watt Solar Panels). So in my set-up, even if the Battery Disconnect Switch is in the "Store" position, my AGM batteries will get charged by my Solar Panels… which is one of the benefits of having Solar!

SilverGate

Correction to the 5th paragraph above: The battery(ies) could be drained with the battery disconnect switch in "Store" position if you do not have solar panels exposed to the sun.

Also note that if you experience a sudden loss of battery charge percentage while connected to shore power with the battery disconnect switch set to "Use", it might be because your converter is failing, which happened to me and described here.

[SilverGate]

Summary of key concepts re: my 2007 Safari Battery Disconnect Switch

1. When connected to shore power, the Battery Disconnect Switch red light stays on in either "STORE" or "USE" mode/setting.

2. When disconnected from shore power, the red light is on only in the "USE" mode.

3. When in "Store" setting, the batteries do not receive power from the converter.

4. Even though it looks like a rocker switch, no matter where you push it, it only changes the mode from the one mode setting to the other setting.

5. I normally keep my setting to "USE". But I did find it useful to place it in "STORE" setting while diagnosing a failing converter and during the converter's replacement seen here.

[RichHog]

This should be inserted in every Trailer manual that comes with a trailer with "the Switch".

The PO had replaced only one of the factory batteries a few months back, Should the other battery be replaced as it is the weak link in the overall power in the system?

[Zigidachs]

The Prosine 2.0 converter/inverter ( three stage) has an automatic cut off mechanism to protect AGM batteries after they are fully charged.

[dznf0g]

Originally Posted by RichHog

This should be inserted in every Trailer manual that comes with a trailer with "the Switch".

The PO had replaced only one of the factory batteries a few months back, Should the other battery be replaced as it is the weak link in the overall power in the system?

Batteries should always be replaced in pairs (or entire bank, if more) unless all are just a few months old (ie. you got a defective new battery and it failed early in life).

In practice, I'm not sure what I'd do if my other battery was only a year or so old. I would do some extensive testing out of the coach before assuming the replacement and the "slightly used" one were performing differently.

That being said, I think pretty much all the "experts" will tell you to replace all hooked in parallel (12V) or series (6 V) should be changed out together.

[wbrownrr]

My experience is identical to SilverGate's (see posts #25 and 26). I also have a solar system on my AS.

[shucklemoon]

Originally Posted by RossFam05BH

Hey All,

After reading the posts in this thread, I finally figured out why the batteries in our trailer never charged when connected to shore power. It is because the red LED when lit does not indicate the position of the solenoid when the trailer is connected to shore power. Therefore, I asked my 12 year-old son Alex to develop a electronic solution to this problem. He came up with the idea to use a CMOS 4013 flip-flop IC to control the lighting of new LEDS to indicate whether the battery disconnect solenoid is in the use (charging batteries) or store (not charging batteries) position. We drilled two holes in the face plate for surface mount LEDS and one for the toggle switch shown. In the pictures in this post, the trailer is connected to shore power. The blue LED indicates that the batteries are charging and the green LED shows that the batteries are disconnected.
Attachment 79827Attachment 79828
So that the LEDS do not drain the batteries when off shore power, Alex included a DPDT toggle switch to cut power to the blue/green LEDS only. The toggle switch in the off position does not cut 12 volt power to the IC, thereby allowing the flip-flop to remember the solenoid's state.
Attachment 79829
In hopes that this will be useful to other Air Forum-ers, Alex has also included a photograph of the circuit board (attached with screws to the circuit board of the panel), and a circuit diagram. The brightness of the blue/green LEDS is easily adjusted by changing the resistance in series with the LEDS.
Attachment 79830Attachment 79838

Bye,

Paul and Alex

Thanks, forum, for this informative thread. It should be required reading for newbies.

1. Please tell me Alex got a full-ride scholarship to MIT. Or a job at the new Airstream factory.

2. Why, oh why didn't Thor install an actual switch, instead of a glorified button, and why'd they use a single red light (which stays on no matter what the switch does in shore power mode, even though leaving it in the wrong position stops charging the battery)? Does none of these guys have a light switch in their garage? Sheesh.

[thiel]

I just turn off the circuit breaker associated with the converter (it's labeled in mine: #3).

That way I can use shorepower for pretty much everything but use solar to (gently) maintain the batteries.

[RossFam05BH]

Originally Posted by shucklemoon

Thanks, forum, for this informative thread. It should be required reading for newbies.

1. Please tell me Alex got a full-ride scholarship to MIT. Or a job at the new Airstream factory.

2. Why, oh why didn't Thor install an actual switch, instead of a glorified button, and why'd they use a single red light (which stays on no matter what the switch does in shore power mode, even though leaving it in the wrong position stops charging the battery)? Does none of these guys have a light switch in their garage? Sheesh.

Hi All,

What a kind response!! Alex is in his senior year at Wake Forest majoring in Computer Science, with minors in Math and Studio Art. Next year he will be going to graduate school and has interviewed at NC state, Harvard and MIT and will be studying electronics and human/computer interfaces. He is also developing a smart electronic interface for our trailer and Interstate which will detail current flow, battery state and charging status, using a raspberry pi computer. I don't know all of the specifics, but he is having fun thinking about the possibilities. I will inform the Airstream community when he finishes the project. Hopefully he can market such a device.

Bye

Paul