House Batteries

2 house batteries only 2.5 years old. After whole day driving, if I turn on inverter for TV only, after 25 minutes inverter turned itself off.

Instead of turn on TV, if I plug in MAC book charger 85W charger, the inverter turned itself off after 10 minutes also.

Does it sound like that I need new batteries?

thanks,
2011 Agile

Have you checked for bad cable connection and battery isolator going bad? Have a garage charge and load test the batteries before replacing them

Are the coach batteries wet cells? If so, have you checked the liquid level under the caps? If low add distilled water and recharge them.

Have these batteries ever been fully discharged a few times and thus possibly damaged?

Perhaps your battery isolator has died. Check battery voltage at terminals while engine is running. Should be around 14.1 volts. If it's in the 12 range, then your isolator has stopped working. Mine gave up after 7 years in our 2008 RS. Replaced it and everything is fine. If isolator is not working, then your batteries won't charge when driving.

BTW, do your batteries get to full charge when you plug in to shore power? If not, then it's the batteries. If so, then it's the isolator.

along a little different line,, should i leave my adventurous on constant charge when not in use
thanks,

I leave my 08 RS Adventurous with the Tripp-Lite plugged in when at home, no issues for me.

Hi Trekker,

what is the voltage of a set of full charged coach battery suppose to be?

2011 Agile

Trekker said:

Perhaps your battery isolator has died. Check battery voltage at terminals while engine is running. Should be around 14.1 volts. If it's in the 12 range, then your isolator has stopped working. Mine gave up after 7 years in our 2008 RS. Replaced it and everything is fine. If isolator is not working, then your batteries won't charge when driving.

BTW, do your batteries get to full charge when you plug in to shore power? If not, then it's the batteries. If so, then it's the isolator.

Click to expand...

This resting voltage for a fully charged battery is what has me concerned.

This has all been posted by me in this forum but I will post here again. My brand new fully charged batteries read 12.7 volts and only 13.6 with the engine running. I read 14.4 volts to ground at the alternator but only 13.6 to ground at the battery. And I read a 0.6 volt drop across the cable from the alternator to coach positive terminal and 0,7 across the cable from the alternator to the engine battery stud in the engine compartment. Based on these measurements I think you all have helped me decide that my "Y" cable is bad, and if I do not replace it I will damage the new batteries.

I have called both Freightliner and my local Roadtrek service techs and both have said the readings I present are normal. Now I do not really know if I have a cable problem or not. Does 13.6 volts at the coach battery really charge the battery? This is a bit confusing. An then I read in this forum that the resting battery voltage should be 13.6 volts. What is right??
Below is a table I got online which says 12.7 volts.

12.7 or higher would be 100% charge on resting batteries. Specs vary from 12.7-12.8 for 100%.

In my experience:

Ditto what Greg said; IMMEDIATELY after taking off a charger, assuming the charger's working properly, you should see 13V or a bit over. AFTER the battery has "rested" a bit, 100% charge should be 12.6 or higher.

Another way to check on battery health is to monitor how quickly that 12.6+ bleeds off. All of my AGM batteries will hold at 12.6 or higher for a couple of weeks, minimum; most of my standard lead-acid flooded batteries will drop to 12.5 or so after about one week. A weak battery will drop down more quickly. Hope this helps.

PS-- when we had trouble with our "under hood generator" last summer, I was told by Adam Nations (the designer of aftermarket alternators used on Roadtreks) that I should see 14.2V at the batteries when the engine was running. Our problem was that I was seeing 16-18 volts. Naturally, the batteries got fried (but were all replaced under warranty by RT in Ontario:thumb up.

Trekker said:

Perhaps your battery isolator has died. Check battery voltage at terminals while engine is running. Should be around 14.1 volts. If it's in the 12 range, then your isolator has stopped working. Mine gave up after 7 years in our 2008 RS. Replaced it and everything is fine. If isolator is not working, then your batteries won't charge when driving.

BTW, do your batteries get to full charge when you plug in to shore power? If not, then it's the batteries. If so, then it's the isolator.

Click to expand...

Is the charging voltage at the battery always 14+ volts when the engine is running? Or when the batteries are fully charged does it drop off to some lower voltage to avoid overcharging. I can see how if the battery voltage/charge is low the charging voltage would be 14+ volts.

gte said:

This resting voltage for a fully charged battery is what has me concerned.

This has all been posted by me in this forum but I will post here again. My brand new fully charged batteries read 12.7 volts and only 13.6 with the engine running. I read 14.4 volts to ground at the alternator but only 13.6 to ground at the battery. And I read a 0.6 volt drop across the cable from the alternator to coach positive terminal and 0,7 across the cable from the alternator to the engine battery stud in the engine compartment. Based on these measurements I think you all have helped me decide that my "Y" cable is bad, and if I do not replace it I will damage the new batteries.

Click to expand...

0.6V is definitely too much of a voltage drop across the Y cable. Replace it, and also check/clean the connection points for the ground strap between the engine block & Sprinter chassis.

I have called both Freightliner and my local Roadtrek service techs and both have said the readings I present are normal. Now I do not really know if I have a cable problem or not. Does 13.6 volts at the coach battery really charge the battery? This is a bit confusing. An then I read in this forum that the resting battery voltage should be 13.6 volts. What is right??
Below is a table I got online which says 12.7 volts.

Click to expand...

12.6V to 12.7V is the correct resting battery voltage when fully charged. Not sure where you got the 13.6V, but that voltage is typical for the battery voltage soon after it has been removed from a charger. After a while the voltage will settle down to the 12.7V range.

bcislander said:

0.6V is definitely too much of a voltage drop across the Y cable. Replace it, and also check/clean the connection points for the ground strap between the engine block & Sprinter chassis.


12.6V to 12.7V is the correct resting battery voltage when fully charged. Not sure where you got the 13.6V, but that voltage is typical for the battery voltage soon after it has been removed from a charger. After a while the voltage will settle down to the 12.7V range.

Click to expand...

BC,
Thanks and I agree the "Y" cable is bad so I need to start there. In the table below you can see where I got the 13.6-13.7 volts. My battery resting voltage is 12.7 but when charging 13.6-13.7.
I do not understand the 12.75 volt readings with the Onan running . Thoughts??

I have also read other threads where you discussed the engine ground strap./ Have you replaced yours? If so, do you know the part number?

Engine off, no shore power or generator-resting
Coach - 12.7 volts
Engine - 12.7
Isolator and breakers - 12.7

Engine running
Coach - 13.6
Engine - 13.6
Isolator - 13.3-13.6

Shore power connected and coach power switch on
Coach - 13.7
Engine - 13.7
Isolator - 13.6-13.7

Generator running
Coach - 13.75
Engine - 12.75
Isolator - 12.75

gte said:

Generator running
Coach - 13.75
Engine - 12.75
Isolator - 12.75

Click to expand...

Gary,

As Greg has pointed out, shore power or generator input should not be any different. The 120 volt input from any of the 2 sources goes thru the Inverter/Charger where it is converted to DC current for charging, all the battery separator sees is the DC current from the Inverter/ Charger. Bottom line is, your separator has failed to engage for some reason during your test. Maybe a sign of failing battery separator, a separator system glitch, or maybe you tested the voltage too early before the separator gets activated. The separator has built in delay circuit to prevent chattering. You need to test it few more times on both shore and generator power to get a conclusive diagnosis.

I have found a very useful Roadtrek RV electric charger system simulator on the web. You can turn on/off engine/Shore power/generator, select the battery condition, and select the model/year on the left hand pane to see how your RV circuit is connected with the possible voltage reading.

http://www.metrotrekkers.org/utility/electrical.htm

2011 Agile

gte said:

BC,
Thanks and I agree the "Y" cable is bad so I need to start there. In the table below you can see where I got the 13.6-13.7 volts. My battery resting voltage is 12.7 but when charging 13.6-13.7.
I do not understand the 12.75 volt readings with the Onan running . Thoughts??

I have also read other threads where you discussed the engine ground strap./ Have you replaced yours? If so, do you know the part number?

snip......

Click to expand...

I haven't replaced the ground strap because the charging voltage increased to the 14.2V range from ~13.8V right after I changed the Y-Cable.

Before replacing the ground strap, I would remove it from where it connects to both the chassis & engine, clean the contact areas & cable ends before buying a new strap. I would only replace the strap if the conductors in the strap are showing signs of corrosion or deterioration, particularly where the conductors attach to the cable ends.

I cannot comment on the different voltages you observed using the Onan vs Shore Power because my GWV Legend has a different electrical system.