Crazy idea for keeping chassis battery topped up?

[Boxster1971]

Originally Posted by FlyFishinRVr

I say it's a flaw because it leaves a gap. On paper it's a 0.4v gap, in reality it's about a 0.2v gap. On my rig, the solar keeps my coach batteries around 12.80-12.85v. There just isn't enough solar up there to push over the magic 13v mark to turn the relay on. As a result, this seemingly insignificant gap is a guarantee that my chassis battery will die if I don't intervene. Not smart......



I think if they changed the trip point on the solar charge controller from 12.4v to 12.6v, that may solve the problem because it should reduce that gap to zero, but personally I don't get why they limit the solar at all. It has its own built in charge controller so why not just let it do its thing and provide a charge any time there's sunshine?

The problem is not the BS/BIM it is the solar controller. Step one change the solar controller to one that does proper three stage charge profile and get full use of the sun energy available for the 100 watt panel.


- - Mike
2013 Lounge EXT on 2012 Sprinter

[FlyFishinRVr]

Originally Posted by Boxster1971

The problem is not the BS/BIM it is the solar controller. Step one change the solar controller to one that does proper three stage charge profile and get full use of the sun energy available for the 100 watt panel.


- - Mike
2013 Lounge EXT on 2012 Sprinter

I thought the OEM charge controller was a 3 stage unit....???

Do you have a recommendation for one that can handle higher wattage and is relatively plug and play with the existing control inputs/outputs? I realize the existing wiring is only good for 10A so it wouldn't need to be anything that can handle more than that. I don't camp in the sun so I have no intent to use solar to run my systems, just keep the batts charged up while the rig is stored.

Thanks!

[Boxster1971]

Originally Posted by FlyFishinRVr

I thought the OEM charge controller was a 3 stage unit....???

Do you have a recommendation for one that can handle higher wattage and is relatively plug and play with the existing control inputs/outputs? I realize the existing wiring is only good for 10A so it wouldn't need to be anything that can handle more than that. I don't camp in the sun so I have no intent to use solar to run my systems, just keep the batts charged up while the rig is stored.

Thanks!

No the Atkinson Electronics Inc. charge controller used by Airstream, which they call the "Sun Explorer Charger Controller" is a single stage on/off pulsed voltage controller. I could never find the exact operational technical details. The best document I found is attached.

There was a great thread earlier this year about changing the panels and controller. Here is the link to that thread:
http://www.airforums.com/forums/f240...-w-150403.html

Post #12 in this thread is from Lew Faber, our resident expert on solar upgrades. He recommends the Morningstar 10 or 15 watt basic controller. Here are his words quoted for your convenience:
==================
"The Atkinson controller should go the way of the Parallax converters supplied in the trailers........ THE GARBAGE BIN!!!!!!

I simple swap out to a Morningstar 10 or 15 amp basic solar charge controller will greatly improve your system's performance and WILL provide for proper 3-stage battery charging.

It's really a no brainier!!!! You can even add Morningstar's remote monitor if you like.


Lew Farber
RVIA/RVDA Nationally Certified Master Tech"
======================

Enjoy,
- - Mike

[Titus]

Here is an excerpt from Precision Circuits on how to troubleshoot the BIM. It helped me find a blown fuse by the coach battery:

Press Dash Switch. Relay should audibly click and Voltage from Chassis Terminal to Coach Terminal should be <0.2V. If Not, Check for 12V power from Dash Switch to Ground Terminal directly on Relay. (Do not use a Chassis Ground) If 12V present and Relay does not click or bring Chassis and Coach Battery Voltage close, replace Relay.

Release Dash Switch Start Engine & Turn on Coach LightsWait between 20 seconds and 2 minutes and Relay should click. Voltage from Dash Switch Terminal to Ground Terminal should be between 3.5Vdc to 6.0Vdc. If not check that Chassis Terminal >13.3Vdc, Coach Terminal <12.6Vdc, Ignition Terminal >12Vdc. (Check that Chassis and Coach Battery connections are not reversed)

Turn off Engine Plug in Shore Power & Turn on Battery Charger Turn on Head LightsWait up to 10 minutes and Relay should click. Voltage from Dash Switch Terminal to Ground Terminal should be between 3.5Vdc to 6.0Vdc. If not check that Coach Terminal > 13.3Vdc, Chassis Terminal <12.6Vdc, Ignition Terminal <2Vdc.

[FlyFishinRVr]

Originally Posted by Boxster1971

No the Atkinson Electronics Inc. charge controller used by Airstream, which they call the "Sun Explorer Charger Controller" is a single stage on/off pulsed voltage controller. I could never find the exact operational technical details. The best document I found is attached.

There was a great thread earlier this year about changing the panels and controller. Here is the link to that thread:
http://www.airforums.com/forums/f240...-w-150403.html

Post #12 in this thread is from Lew Faber, our resident expert on solar upgrades. He recommends the Morningstar 10 or 15 watt basic controller. Here are his words quoted for your convenience:
==================

Enjoy,
- - Mike

Great stuff, thanks Mike!

[Mcrid]

A simple solution without doing an extensive upgrade. You will have to run leads from the chassis battery.

http://www.morningstarcorp.com/products/sunsaver-duo/

[FlyFishinRVr]

Originally Posted by Mcrider

A simple solution without doing an extensive upgrade. You will have to run leads from the chassis battery.

http://www.morningstarcorp.com/products/sunsaver-duo/

I thought about that controller, but in order to get the temp compensation, you need to install the controller in the battery bay. That means you really need the remote meter to go with it, so that's $160 and you still need a solar panel. If I were going to go that route (something quick and temporary), I'd probably go with the Renogy Adventurer since it has a built-in LCD display and a temp probe on a fairly long lead (80"), and it's only $90.

I had hoped my little 5W panel would keep the chassis battery topped up, but given what I'm seeing with the set points on the Atkinson charge controller and Precision Circuits BIM, the chassis battery is getting way too low for it to even hope to keep up (about 12.4V, or 70% SOC). That means any charging solution I come up with for the chassis battery needs to make up approx. 30% SOC on a 80 AH battery, or up to 24A in a day!

That means one of two things: Get a 100W panel (and a suitable charge controller) and put it in the window of my rig when it's being stored to keep the chassis battery happy (very easy to install), or bite the bullet and permanently install a second 100W panel on the roof and replace the Atkinson charge controller with something else (maybe the Renogy 20A MPPT controller and Tracer remote meter.....only $180 for both!). The first option is really quick and easy and requires no permanent mods, the second is a bit more involved.

Of course there is option #3, and that's to pull the chassis battery disconnect to detach it from the parasitics that are pulling it down and see if my little 5W charger is able to keep up with natural discharge. I'd just have to direct-connect it to the battery vs. using the 12V socket in the dash. Hmmmm.......