Low Voltage

[Lfresin1]

In my 2020 FR3 30DSF I heard some clicking. It had been sitting for several days with the battery disconnect on. The clicking was coming from the fuse box where the house batteries are located. When engaging the battery disconnect, the ceiling lights were flashing in sync with the clicking. Master panels red lights were blinking next to the words low voltage, start the engine. I ran the engine a few minutes and all is well. Checked the house batteries charge level and they showed full. A week ago I ran the generator and engine for several minutes, so this was a real surprise. Any ideas why this would happen?

[babock]

Originally Posted by Lfresin1

In my 2020 FR3 30DSF I heard some clicking. It had been sitting for several days with the battery disconnect on. The clicking was coming from the fuse box where the house batteries are located. When engaging the battery disconnect, the ceiling lights were flashing in sync with the clicking. Master panels red lights were blinking next to the words low voltage, start the engine. I ran the engine a few minutes and all is well. Checked the house batteries charge level and they showed full. A week ago I ran the generator and engine for several minutes, so this was a real surprise. Any ideas why this would happen?

What was the voltage of the batteries before you stated the engine? You likely majorly discharged them. BTW, running a generator for a few minutes does close to nothing.

[Lfresin1]

I ran then generator for 30 minutes with the AC on to get heated up. Same with the engine. Both charge the house batteries, but they registered full on the panel before and after running the generator and engine.

[Hclarkx]

Old batteries that have essentially failed can behave this way. And as lead-acid batteries approach their end-of-life things go awry fairly quickly.

When charged the voltage of a weak battery can be near normal but the battery can't support load very long. It also can charge up very quickly because it has little capacity. I.e., the battery may run down in 10 minutes and re-charge in 10 minutes. So, maybe it's time to have an auto parts store do a load test on your batteries.

Or you can do this yourself by putting a known load on the battery and watch the voltage. Down around 12.1 or 12.2V the battery (lead-acid) is down around 50% charge. The ampere-hours you draw to get the battery down to that voltage will be about half the battery Ah rating with new batteries and much less with batteries that are near end-of-life.

[Lfresin1]

I would hope that's not the problem. The disconnect was engaged after the batteries were charged AND it's a brand new coach.

[babock]

Originally Posted by Lfresin1

I ran then generator for 30 minutes with the AC on to get heated up. Same with the engine. Both charge the house batteries, but they registered full on the panel before and after running the generator and engine.

You need to check the voltage many hours after you stop charging them. When you charge a lead acid battery, they get a surface charge that needs to wear off before you can accurately measure them. With 30 minutes of charging you might have only gotten 10AH into the batteries.

The disconnect typically doesn't disconnect everything. You will still have LP/CO detector on and possibly a radio in standby just to name two. They are enough to discharge the battery over time.

[Hclarkx]

Originally Posted by Lfresin1

I would hope that's not the problem. The disconnect was engaged after the batteries were charged AND it's a brand new coach.

Probably not, though I suppose bad batteries do slip through. And a deep discharge as you seem to have experienced takes out a lot of life. As Babcock noted, it takes a long time (at 14.4 volts typically) to charge a battery fully. If the batteries are 250 ampere hours and need a full charge, that's 10 hours at 25 amps plus losses so about 13 hours (somewhat less for AGM batteries) if your converter delivers 25 amps (this is typical).

Two amps from the truck will get the voltage back up but would take 125 hours to fully charge a 250 Ah battery.

[rk06382]

Originally Posted by Lfresin1

I would hope that's not the problem. The disconnect was engaged after the batteries were charged AND it's a brand new coach.

What BCC do you have? (Battery Control Center) I have a SDC-107A from RV Custom Products.

See my thread My coach batteries stopped charging from the alternator. (Bad SDC-107A)

If the BCC is working right you should get about 80 amps from the engine alternator. You will only get a maximum of 50 amps from the the converter. There is a 50 amp breaker inline with the converter. As mentioned above, The disconnect does not remove everything from the battery. But it does disconnect the converter from the batteries.

If it is not a SDC-107A, Can you tell me what replaced it? But if it is the SDC-107A:
Quote from Custom RV's SDC-107A Battery Control Center (pdf):

"For the purpose of charging the coach and chassis batteries, power for the control electronics is obtained from the ignition switch and coach battery through diodes D1 and D2. Underway, when the charging source is the engine generator, +13.2vdc on the ignition line triggers the electronics. After a 15sec. delay, the interconnect relay closes, paralleling the batteries. Should the battery voltage go below 12.7vdc, the interconnect relay will open after around a 15sec. delay. When the vehicle is parked and on shore power, when the converter brings the coach battery up to +13.2vdc, the interconnect relay will close after the 15sec delay, charging the chassis battery as well. As before, the relay will open when the battery voltage goes below 12.7vdc."

This was taken before I replace the lead-acid batteries.


FR3 Battery Control Center Schematic 5-31-16 117963A.pdf

[dward51]

It may be an auto-reset DC breaker. I know one time my battery ran down and when I plugged the trailer back in at the house, my auto-reset main DC breaker at the tongue kept clicking off and on (55 amp converter on a 50 amp DC breaker - initial draw must have been the full 55 amps?). Did this for about 20 or 30 seconds and once the battery had some charge, it stopped. I've since replaced that battery.

[rk06382]

The 50 amp circuit breaker.

[Lfresin1]

I just went back to the motorhome and the house batteries were dead. The steps wouldn't even come out. I ran the engine for 5 minutes and the batteries claimed they were fully charged and all was well. The only thing I can see that might still draw on the battery when the disconnect is engaged is the dash radio. I powered that off and now we'll see. Still, if the engine running can power the batteries up in just 5 minutes, something isn't quite right.

[babock]

Originally Posted by Lfresin1

I just went back to the motorhome and the house batteries were dead. The steps wouldn't even come out. I ran the engine for 5 minutes and the batteries claimed they were fully charged and all was well. The only thing I can see that might still draw on the battery when the disconnect is engaged is the dash radio. I powered that off and now we'll see. Still, if the engine running can power the batteries up in just 5 minutes, something isn't quite right.

And how soon after running the engine did you check the voltage of the batteries? What was the battery voltage at that time.


You need to use a meter and measure the draw when your vehicle is sitting. Then you need to add a true battery disconnect.

[Lfresin1]

Right afterwards. I checked the panel and it had all 4 lights on indicating a full charge. The steps came out, I could turn lights on, and a fan. But I know that running the engine for such a short time could not really charge the battery to full capacity.

[Mr. Dan]

Originally Posted by Lfresin1

Right afterwards. I checked the panel and it had all 4 lights on indicating a full charge. The steps came out, I could turn lights on, and a fan. But I know that running the engine for such a short time could not really charge the battery to full capacity.

On most of these beasts, using the converter to charge batteries causes all 4 lights to come on regardless of state of charge. You must use a multimeter or some such device. Those lights are not to be trusted without other verification.

[Chuck_S]

You can't charge a dead battery is less than several hours.

A "RV battery charge indicator" (volt meter) only displays the surface charge on a battery and a 5 minute "charge" will show 12.7v or higher -- full charge. Ain't so. Battery is still dead. An overnight charge is usually sufficient, 24 hours is better.

Engine alternator on a tow vehicle or motor home is an especially poor battery charger. Recharges the minute amount of power used to start the engine and then just trickle charges -- several hours needed to charge the house battery. There's a reason safety vehicles like ambulances have second alternators and boats have auxiliary generators.

-- Chuck

[Lfresin1]

According to Forest River, the LP detector draws from the battery even when the disconnect is engaged. So, I tried to turn it off. All it has is a green light showing power and a button to test it. Turning off all the circuit breakers didn't stop it either. According to the battery indicator, it's drawing 25% of the battery in 24 hours.

Short of removing the battery connections, defeating the whole convenience of a disengage button, what other options are there to stop the LP detector from drawing power?

[babock]

Rewire where the LP detector gets its power. Move it off of the battery side of the disconnect switch.

[Lfresin1]

Sounds good. Not an electrician. How is this done?

[babock]

Originally Posted by Lfresin1

Sounds good. Not an electrician. How is this done?

Need to trace the existing wire or add your own with a fuse. You may find it already at the battery side of the disconnect switch.


Someone else who has your model may already know where this is and has done it before.

[jdbunch1630]

Why don't you install a small batter tender on your RV, that was you don't have to keep it plugged in to 110vt to have your converter charge your battery's, the tender will do the job