Community Forums

tinker.round · 08-20-2019, 03:46 AM

I am wondering if something is wrong or what...I had to have my alternator on my coach replaced. Now the engine battery is charging great, and so are the coach batteries 13.4 (per inverter display) with the engine running. I turned off the engine and turned on the generator. Now the coach batteries show a different setting of 12.5 when I turn on the inverter to see the charge. Is something wrong between the generator and the coach batteries or does it just take a long time for the generator to put out the same power that the engine does. Or do I need some work to get done in this area...

Sbrownstein · 08-20-2019, 04:21 AM

Quote:

Originally Posted by tinker.round

I am wondering if something is wrong or what...I had to have my alternator on my coach replaced. Now the engine battery is charging great, and so are the coach batteries 13.4 (per inverter display) with the engine running. I turned off the engine and turned on the generator. Now the coach batteries show a different setting of 12.5 when I turn on the inverter to see the charge. Is something wrong between the generator and the coach batteries or does it just take a long time for the generator to put out the same power that the engine does. Or do I need some work to get done in this area...

If you waited at least 30 seconds for the transfer switch (if you have one) your converter/charger is not functioning. House battery voltage should be at least 13.2, even if the batteries are fully charged. Assuming that you made no changes to the battery disconnect between running the engine and starting the generator and assuming that your inverter is not actually drawing current since the generator is running and supplying all 120 volt circuits directly.

twinboat · 08-20-2019, 06:04 AM

Your generator does not directly charge your batteries, it substitutes shore power to power all of the 120 volt systems including the battery charger.

If the air conditioners work with the generator running, then you have a charging issue.
May be as simple as the battery disconnect switch off.

If nothing 120 volts works, it could be a generator issue. May be tripped breakers on the generator control panel, out in the compartment.

Rumline · 08-20-2019, 01:52 PM

Quote:

Originally Posted by tinker.round

Now the engine battery is charging great, and so are the coach batteries 13.4 (per inverter display) with the engine running. I turned off the engine and turned on the generator. Now the coach batteries show a different setting of 12.5 when I turn on the inverter to see the charge.

To me this sounds "normal". Your alternator is supplying 13.4V to charge the batteries. You can't measure the batteries voltage while the alternator is charging them; all you'll see is the charge voltage. Once you remove the alternator charge you can measure the voltage. But if you then turn on the inverter, and presumably therefore your refrigerator or other loads attached to the inverter, they start discharging your battery and the voltage at the meter is again not accurate. I mean it's accurate from the sense of that's what's coming out of the terminals, but it's not an accurate state of charge (SoC) indicator. To get a somewhat reliable SoC by voltage alone, you need to measure the batteries with no current coming in or out, or as little out as possible. To get a more reliable SoC, you need to install a shunt-based battery monitor.

So when I say that it sounds normal, I mean that it is normal for batteries to meter at a higher voltage when charging than when discharging, and at yet another level (between the other two) when resting.

We need more information to determine if there is a problem or not, as the other two responses allude to. What loads are connected to the inverter and running when you took that 12.5V reading? I agree with twinboat that it could be a problem with your onboard converter/charger not charging the batteries from shore/generator power, but again need more info.

THenne1713 · 08-20-2019, 10:55 PM

Quote:

Originally Posted by tinker.round

I am wondering if something is wrong or what...I had to have my alternator on my coach replaced. Now the engine battery is charging great, and so are the coach batteries 13.4 (per inverter display) with the engine running. I turned off the engine and turned on the generator. Now the coach batteries show a different setting of 12.5 when I turn on the inverter to see the charge. Is something wrong between the generator and the coach batteries or does it just take a long time for the generator to put out the same power that the engine does. Or do I need some work to get done in this area...

From what I read, (factory) RV Inverters are INVERTER/ CHARGERS, and switch automatically when source changes? (Maybe) you are turning OFF Inverter, that turns off the Charger? Aftermarket installations is maybe a different story and procedures?

BWDog · 08-22-2019, 11:02 PM

Make sure that the heavy gage wires that connect to the converter charger are both held securely with the set screws, they connect to the house batteries and charge them. Make sure that the house batteries have electrolyte above the plates , add distilled water as needed to cover the plates. Check that the battery connectors are clean and tight making good contact. Your house batteries may be worn out if over 4 years old. Have batteries tested under load. Keep batteries charged and don't leave them discharged, it will shorten battery life drastically. If you leave rig connected to 110vac 'shore' power, check battery electrolyte level every 30 days and add distilled water to keep plates covered. The more you know about the batteries and charging system and how to maintain it, the better.

THenne1713 · 08-25-2019, 11:13 PM

12.5VDC is 90%+/- CHARGE STATUS** (12.6-12.7= 95%-100%), which I suspect is what you are seeing, like (possibly) by turning INVERTER ON, you are automatically disconnecting (GEN POWER/ SHORELINE) 120vac the CHARGER? (probably thru the ATS or relays in the Inverter?) Get a Meter that you can put directly to battery, SET TO DCV and check battery voltage w/ INVERTER OFF? (GEN or shoreline ON) (** Voltage Under LOAD from Inverter, too)

kayak70 · 08-30-2019, 05:39 AM

Quote:

Originally Posted by THenne1713

From what I read, (factory) RV Inverters are INVERTER/ CHARGERS, and switch automatically when source changes? (Maybe) you are turning OFF Inverter, that turns off the Charger? Aftermarket installations is maybe a different story and procedures?

To be clear, only some RV inverters provide the charging function. Not all inverters provide the charging. In smaller Class C rigs you typically have a small inverter to use off grid which provides 120VAC from the battery but has no ability to charge the battery. Normally in the small RV charging is provided by a separate Converter/Charger near the distribution panel for power. Older models are "built-in" and part of the distribution panel, new model converters are stand alone but near the distribution panel and offer mult-stage charging to lengthen battery life. A common 45amp converter in the past few years is the PD9245C. The inverter will have a small transfer switch internal or external so it will pass through shore or generator power and not provide 120VAC from the batteries at the same time.