Newbie questions about battery management

[StephensNC]

I will apologize in advance for asking a question likely answered many times before though I have been unable to find those answers.

I have purchased a 2014.5 Interstate, replaced the house batteries with new AGM's, and all seems to be working well. However, I am unclear about the information provided on the various monitors particularly how to know when the batteries are in fact fully charged. Can someone point me to what I need to read to get up to speed? Thanks!

Jim

[Boxster1971]

Originally Posted by StephensNC

I will apologize in advance for asking a question likely answered many times before though I have been unable to find those answers.



I have purchased a 2014.5 Interstate, replaced the house batteries with new AGM's, and all seems to be working well. However, I am unclear about the information provided on the various monitors particularly how to know when the batteries are in fact fully charged. Can someone point me to what I need to read to get up to speed? Thanks!



Jim

Jim - I can understand your frustration. There are three ways to read the battery voltages and it can be confusing. The only way to get an accurate state of charge is by open circuit voltage of your batteries as described in the attached page from the Lifeline battery manual.

Unfortunately you can't get that accurately without completely disconnecting your batteries and placing a volt meter across the terminals. But you can get close.

The solar control panel readings are the least useful because this meter is not accurate and if you read it when the sun is shinning it just gives you the charge voltage.

The voltage readout for the battery voltages, selected buy the switch on the tank monitor is useful if checked when not charging and everything turned off.

Another option is the Magnum inverter/charger control panel display. The voltage shown is also accurate.

Start by fully charging your batteries by being plugged into shore power overnight. Then the Magnum display should show "Float" and a voltage of 13.4. Then stop charging by unplugging in the dark so there is no solar charging. Have everything turned off, use a flash light to see what your doing. The voltages shown then on the Magnum display and tank monitor panel should tell you your state of charge based on the attached page as close as you can with what Airstream provided.

Hope this helps,


- - Mike
2013 Lounge EXT on 2012 Sprinter

[StephensNC]

Mike - Thanks for the info on the batteries. I will check the voltage tonight as it is parked in the sun now. I do not have any info on the tank monitor. What batteries are referred to by Main and Aux?

[Protagonist]

Originally Posted by StephensNC

Mike - Thanks for the info on the batteries. I will check the voltage tonight as it is parked in the sun now. I do not have any info on the tank monitor. What batteries are referred to by Main and Aux?

Main is the engine starting battery under the driver's footwell. Aux is the house batteries.

[Silver Hawk]

1. What's DOD?

2. The Lifetime chart - is it good for wet call batteries and AGM batteries?

Thanks

[Protagonist]

Originally Posted by Silver Hawk

1. What's DOD?

2. The Lifetime chart - is it good for wet call batteries and AGM batteries?

Thanks

DOD = Depth of Discharge. 10% DOD is 90% charged.

[Boxster1971]

Originally Posted by Silver Hawk

1. What's DOD?

2. The Lifetime chart - is it good for wet call batteries and AGM batteries?

Thanks

That Lifeline chart is only applicable to Lifeline AGM batteries, although it probably isn't far off for any lead-acid battery.

A quick search on the phrase "battery voltage vs depth of discharge" produced this link to a copy for the East Penn Technical manual.
http://www.evdl.org/docs/deka-vrr.pdf

It contains this chart that covers the major types of lead-acid batteries.

[Boxster1971]

Originally Posted by StephensNC

Mike - Thanks for the info on the batteries. I will check the voltage tonight as it is parked in the sun now. I do not have any info on the tank monitor. What batteries are referred to by Main and Aux?

You should have a TouchSensor tank monitor panel like the one I attached below. In addition to the "TANK TEST" rocker switch there should be a two position rocker switch labeled "BATT MAIN" for the engine battery and "BATT AUX" for the house batteries. The voltage is displayed in the "BATTERY VOLTAGE" display when you hold the rocker switch in either position. In my experience this seems to be a fairly accurate voltage reading.

Your 2014 Owners manual should have this same information on page H-17. If you don't have a manual or want a soft copy PDF version go to the Airstream web site at this link under Service-Manuals, select the year from the pull down menu year and download the manual (s) you want.
https://www.airstream.com/service/manuals/

I've found that the 2015 and later manuals are the best as Airstream finally did a major upgrade to their owners manual. The systems have not changed much between 2013-2015.

Let me know if you don't have this panel as I thought all Interstates since 2011 have it.