Charging Engine batteries

[rlwhite]

Have a question on how to determine if engine batteries are charging while plugged into 20-amp shore power.
Twice now, while the coach has been in storage, I've gone out to start the coach and the batteries were drained down. Both times it had been just shy of a month since I had started the coach. Seems I read a previous post about a switch that is supposed to register shore power and send a charge to the engine batteries but I can't find the post. Is there anywhere I can use a meter to check and see if the batteries are getting a trickle charge while plugged in? Will be sending an email to Entegra tomorrow to ask but Any help would be appreciated.

[757driver]

Originally Posted by rlwhite

Have a question on how to determine if engine batteries are charging while plugged into 20-amp shore power.
Twice now, while the coach has been in storage, I've gone out to start the coach and the batteries were drained down. Both times it had been just shy of a month since I had started the coach. Seems I read a previous post about a switch that is supposed to register shore power and send a charge to the engine batteries but I can't find the post. Is there anywhere I can use a meter to check and see if the batteries are getting a trickle charge while plugged in? Will be sending an email to Entegra tomorrow to ask but Any help would be appreciated.

Rob,

While plugged into shore power there should be a charge going to your chassis batteries IF your house batteries are being charged AND the house batteries are at of above 13.3v AND your chassis batteries are below 12.6v. In this instance the chassis batteries will receive a charge for 1 hour and the pattern will repeat as necessary.

If you have the Onan EC-30 panel above the entrance door you can see the voltages for both house and chassis in that display by using the up/down buttons.

If you do not see any indication of a charge to the chassis batteries then I would suspect a bad BIM (battery isolation manager).

[foundwaldo]

I have 2 shutoff switches one for the house and one for the chassis. They both have to be on for the both batteries to charge. If I turn off the chassis battery it will not charge. My house batteries can not be turned off if the shore power is plugged in.

[Unplanned Tourist]

Bad BIM would be my first guess as well.

Happy Glamping.

[rlwhite]

Thanks everyone for your responses, I couldn't remember what the "BMI" was called or new that the EC30 could tell me that status of the engine batteries.

[rlwhite]

Is the BIM located behind the panel with the verticle row of breaker switches in the rear passenger side cargo bay?

[757driver]

Originally Posted by rlwhite

Is the BIM located behind the panel with the verticle row of breaker switches in the rear passenger side cargo bay?

Rob,

You should not need to remove the panel with the breakers and disconnects but inboard of this should be a panel to remove which will have the BIM behind it.

[Bobbafett]

Jumping on this. How can someone test if shore power charges chassis battery. not using ec panel.

[Gary.Jones]

If you have a volt-ohm-meter or a digital volt meter this is a simple test. Simply measure the voltage across the batteries with the shore power plugged in and with the coach unplugged. A fully charged battery should have a resting voltage of approximately 12.9 volts (and if it is discharged, obviously, below that).

A battery being charged by either the alternator or the an on board charger, should show a voltage significantly higher than that, often around ~13.5 - 14.2 volts.

If you can read the voltage through some other meter already on board the coach, then you can use that instead of a voltmeter. However, if you dont have one already, you should buy one.... there are a hundred things a good meter can help you solve. You can find a good one for about $60 at Harbor Freight.

Gary

[MoHoGo]

Originally Posted by Gary.Jones

If you have a volt-ohm-meter or a digital volt meter this is a simple test. Simply measure the voltage across the batteries with the shore power plugged in and with the coach unplugged. A fully charged battery should have a resting voltage of approximately 12.9 volts (and if it is discharged, obviously, below that).

A battery being charged by either the alternator or the an on board charger, should show a voltage significantly higher than that, often around ~13.5 - 14.2 volts.

If you can read the voltage through some other meter already on board the coach, then you can use that instead of a voltmeter. However, if you dont have one already, you should buy one.... there are a hundred things a good meter can help you solve. You can find a good one for about $60 at Harbor Freight.

Gary

Gary...good info, but you won't see any charge going to your chassis battery bank until your charged up on the house battery bank and the BIM switches to charge chassis. At least that is the way my 2017 works.

Also, good advice to get a VOM as that will help you get a handle on things.

[twinboat]

Originally Posted by MoHoGo

Gary...good info, but you won't see any charge going to your chassis battery bank until your charged up on the house battery bank and the BIM switches to charge chassis. At least that is the way my 2017 works.

Also, good advice to get a VOM as that will help you get a handle on things.

The BIM doesn't really switch to the chassis battery for charging it.
It combines the chassis battery to the house battery, at 13.4 volts, so that they all charge together.

As mentioned, its not a continuous charge, so it may not be in charge mode when your testing voltages. If you turn on the headlight, that draw should cause it to combine. Then test for charging volts.

I can hear my BIM cycle on and off at all different times of the day. It also causes my ScanGauge II to activate for a few seconds. Not sure if its during the combining or disconnecting cycle.

[Gary.Jones]

Jim

I appreciate the expansion. I knew that, but forgot to mention it in my post. Thanks. The principle is the same but the BIM has to have the batteries charging.

Thanks

Gary

[oneknight]

I simply must always know my battery voltage. Not sure why I feel this way, it's a thing with me.

I put these voltmeters in the dash.
They are made by Lascar, mount with a single 1/4" hole, and cost about $30.
Top one connects to house power at the lighter socket.
Bottom one to chassis battery power at the ignition switch.

I can clearly see the BIM switching, along with everything else battery.
There is a thread on the installation.

[brobox]

Jim, that was a nice Mod. Takes all the guess work out and very functional.