Battery Charging Confusion

EL

Elk Prairie

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Joined
Jul 14, 2023
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Rolla
I have a 2018 Thor Axis 25.5. Last year I replaced both the chassis and house batteries. We went on a couple trips and had no problems. Over the winter the chassis battery was put on a trickle charger and the house batteries removed and put inside.

In the spring the house batteries were put back and recharged. The chassis battery was ok. After a trip I connected the shore power and left the refrigerator on. After a month I was going to take the RV out so I disconnected the shore power and tried to start the engine. The chassis battery was completely dead. I looked at the power level of the house batteries and they were dead also.

I thought if the shore power was connected the house batteries stayed charged.
I am now charging the chassis battery with a 2 amp charger. It seems to be charging OK and the house batteries are charging as well. I have had the RV three years so am still a newbie. Any suggestions would be appreciated. Thank you
 
Shore Power (SP) only charges the house batteries (and then the chassis battery) if the USE/STORE switch (MASTER POWER Switch) is in USE (ON). Otherwise the batteries are disconnected from the house DC buss and charger.
 
Yep... the question is - Did you leave the battery disconnect switch (use/store switch) in the ON (or USE) position?

I don't like the terms "use/store"... because "disconnect" is more specific. Either the batteries are CONNECTED or DISCONNECTED. You could technically "use" the motorhome with batteries disconnected.

As a note, I NEVER turn my battery disconnect OFF unless I'm working on the batteries. They are always charging from solar or shore power.
 
There is a switch to the lower left when I enter the RV labled "Main Power". I am assuming this is the master switch. When I am going to drive the RV I always turn this switch on (it is a rocker switch that returns to its original position after being pressed) and this light next to the switch comes on.

If I understand correctly, with the light on while the engine is on, the alternator charges the chassis battery first and then the house batteries.

Here is where I am confused. When I park the RV and turn the engine off, I press the Main Power switch and the light goes off. I then make my connections including the shore power. As soon as I flip the breaker to the connected shore power line the light next to the Main Power switch comes on. All the lights, AC, and fridge are powered. Are the batteries being charged or do I have to press the Main Power switch to make that happen?

If I press the Main Power switch after applying shore power I hear a buzzing towards the rear of the RV. Is this the converter running?

Thank you for your replys
 
Elk Prairie said:
There is a switch to the lower left when I enter the RV labled "Main Power". I am assuming this is the master switch. When I am going to drive the RV I always turn this switch on (it is a rocker switch that returns to its original position after being pressed) and this light next to the switch comes on.

If I understand correctly, with the light on while the engine is on, the alternator charges the chassis battery first and then the house batteries.

Here is where I am confused. When I park the RV and turn the engine off, I press the Main Power switch and the light goes off. I then make my connections including the shore power. As soon as I flip the breaker to the connected shore power line the light next to the Main Power switch comes on. All the lights, AC, and fridge are powered. Are the batteries being charged or do I have to press the Main Power switch to make that happen?

If I press the Main Power switch after applying shore power I hear a buzzing towards the rear of the RV. Is this the converter running?

Thank you for your replys
Click to expand...


Well there's your problem. With that switch OFF there is no connection between the house DC buss/charger and the batteries. Always leave that switch ON unless storing the RV for more than a few days without SP.

All that light tells you is that there is 12 VDC applied to the house DC buss. Your overhead lights would tell you the same thing if left on.

And BTW; you do NOT need to turn the MASTER POWER switch on for the alternator to charge your house batteries. That always happens.
 

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Axis25.2 said:
Install this on the steps and you'll always know if your use/store switch is on or off. NO GUESSING! I'm an ASE Certified mechanic and it drove me nuts...

I also installed one near my stereo because the stock Axxera drained my engine battery. I installed an on/off switch near the digital gauge.


https://www.amazon.com/gp/product/B07RDB6DXZ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
Click to expand...

How would a voltmeter tell anybody the status of their USE/STORE switch? It provides the same function as the LED light if you connect it to the DC buss side of the latching relay. If you attach it directly to the house batteries it will tell you the battery voltage and if they are/aren't charging.
 
On my panel, i have buttons to turn charger and inverter on or off

Charger must be on to charge batteries as well as the house battery switch

Chassis batteries disconnect must be closed to charge as well
 
I think the voltmeter is better than the light because you will know the actual status of the batts per the chart
 

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GeorgePal said:
I guess that depends on where you attach it to the 12v . I think I would put it downstream from the disconnect. So 0v in disconnect. I would only really want to monitor whenim using the RV anyway
Click to expand...

Downstream in which direction?

"Ov in disconnect" I think that means 0 volts when the disconnect is open? So on the house buss side? Except it will read converter output voltage when plugged in (or generator running) regardless of the status of the disconnect. So doesn't resolve the LED issue or the OP's issue.

The monitor I linked is connected to the batteries to monitor battery status. It measures all current in and out of battery as well as battery voltage at all times.
 
Total waste of money.

Turn on an overhead light. Light on, switch on. Light off, switch iff.

Also not all main power lights only show power at the switch.! With mine the light comes on when the relay closes and power is supplied to the coach.
 
Have to respect ACE, i bet this is the most asked question on this site. I missed this once, left the pwr switch on with radio on... I can tell you the emerg switch works great. I like the suggestion,... keep interior lights on. With no SP on turning the pwr switch off extinguishes everything, before exiting RV ensures you've done it right.
 
Last edited:
I have a Windsport 2015 with a similar problem, except my chassis battery does not charge the house batteries. There is supposed to be a management system, but I cannot find it. House batteries are charged by shore power or generator, but the alternator does not charge the house battery. Any suggestions?


Tom
 
tcyjby said:
I have a Windsport 2015 with a similar problem, except my chassis battery does not charge the house batteries. There is supposed to be a management system, but I cannot find it. House batteries are charged by shore power or generator, but the alternator does not charge the house battery. Any suggestions?


Tom
Click to expand...

Similar problem? Sounds like the opposite problem.

A 2015 may have a Battery Control Center (BCC) under the hood to handle this or a Battery Isolation Relay Delayed (BIRD) with a trombetta solenoid in the house battery compartment. Go to the Thor Owners Resource website and create an account with your VIN to view/download electrical diagrams to see what you have.
 
Thank you to all who replied. I've been more careful not to turn the switch by the door off and have been ok.
 
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