House battery

[Patof]

I have an interstate ext 2014 and I want to know if it's normal that the house battery go down after only 4 days when the vehicle is unplug from shore power and battery disconnect switch to off position?

[73shark]

Welcome to the Air Forums.

Not if it's parked where the solar panel can receive light and the inverter is Off.

[lewster]

I just finished studying The BIM (Battery Isolation Manager) from Precision Circuits that the newer AI uses for another client. It specifically states that if there is no charging going on at either battery bank, that the solenoid contacts will open and effectively disconnect the 2 battery banks.

Since your 100 amp panel is connected to the positive buss bar leading directly to the house batteries and is probably not providing sufficient amperage for the BIM to 'see' a charging source, the batteries remain isolated from each other. This will allow your engine battery to be depleted and your house battery to remain full. You can still start the coach using the starting assist button on the dash, which temporarily connects the 2 banks for emergency engine starting.

If you add more solar to increase the charging amperage to the house batteries, the BIM will then see this amperage as a 'charging source' and re-connect the 2 battery banks and will allow the engine batteries to receive charge from the house batteries.

This is how your engine battery gets charge while connected to shore power. The BIM recognizes the charge from the inverter/charger going to the house batteries and will complete the connection between the 2 banks IF the engine battery is below 80% of it's charge capacity. It will the disconnect the 2 banks when both have reached float charge levels for an hour so that no overcharging can occur.

Hope this helps a bit.

[73shark]

Did your study of the BIM reveal what the minimum current was that it needed to see to charge one or the other sets of batteries?

[lewster]

OK,

Here is the operational overview of the BIM:

Overview:
The Battery Isolation Manager (BIM) monitors the Battery Voltage of both the Chassis and Coach Batteries over long periods of time. If it senses a charging voltage, it connects the two batteries together. If the charging system is drastically overburdened, the batteries will be isolated, however, if the BIM sees a long term charging of both batteries it will allow the batteries to remain connected and allow the charging system to do its job. Once the batteries have reached a Float Charge state for one hour, the BIM will isolate the batteries to prevent overcharging, and will only reconnect the batteries for charging if one of the Battery drops to approximately 80% charge, and the other is being charged. If the batteries are not being charged, BIM isolates the two batteries to prevent an electrical draw in one system from depleting the other battery. The long term monitoring of the batteries prevents the annoying Relay clicking that exists in simpler Isolation Modules today.

The line in bold explains that the batteries are connected ONLY when one battery reaches 80% charge level (20 % depth of discharge) and the other battery is being charged.

This 80% level represents approximately 12.6VDC on most batteries, but may slightly vary due to battery construction.

Hope this helps!

[Protagonist]

Originally Posted by Patof

I have an interstate ext 2014 and I want to know if it's normal that the house battery go down after only 4 days when the vehicle is unplug from shore power and battery disconnect switch to off position?

If you're parked where you have adequate sunlight, and have your house power users switched off, the house batteries should stay charged.

Something to consider: The 120vAC system is parallel to the 12v system. Turning off the 12v system doesn't turn off the 120v system. If your inverter/charger in on and in automatic mode, whenever it's not charging it could be inverting, drawing from your batteries, even with the 12v power switched off. For example, if the circuit breakers are on and you didn't turn off the fridge from the thermostat dial inside, you could be powering the fridge and not realize it. That by itself would deplete the batteries in about four days, even with daytime sunshine on the solar panel.

I make a point of shutting off the breakers as well as the 12v system whenever I put my toy away for a few days.

[Rapa Nui]

Hi guys... Thanks for all of the insights into the battery-charging. I contacted Airstream Jackson Center and here's there response to my question about shore power charging both chassis batteries:

If the battery disconnect switch is in the “use” position both batteries are being charged.


Airstream Customer Relations
937-596-6111 Ext. 7401

[73shark]

Originally Posted by Protagonist

I make a point of shutting off the breakers as well as the 12v system whenever I put my toy away for a few days.

Doesn't turning off the inverter kill all of the 120V drains precluding the need to turn the breakers off?

[Patof]

Thank you guys, you give me better answers than the dealer we have here in Quebec, I will test your suggestions this weekend!

[Protagonist]

Originally Posted by 73shark

Doesn't turning off the inverter kill all of the 120V drains precluding the need to turn the breakers off?

It should, but I have run my house batteries below 0% charge on more than one occasion, so I take a "bent-and-suspenders" approach just to be sure. In fact, I shut down the breakers one at a time from right to left BEFORE turning off the inverter/charger, to gradually shed loads one circuit at a time, and turn on the breakers from left to right when turning on my AC power, no matter what the source— inverter, generator, or shore power.

And for those with a Magnum instead of a Tripplite, they have a hard time actually turning the inverter/charger completely off due to the switch location, so the advice to shut off the breakers is more generally helpful regardless of model year.