Batteries losing charge while plugged into shore power

micro_jul · 11-10-2019, 03:15 PM

Our two new deep cycle batteries are losing power while plugged into shore power. Any ideas as to what would cause that?

AudiDudi · 11-10-2019, 03:17 PM

Is the battery switch turned on?

What voltage are you seeing at the battery from the converter?

micro_jul · 11-10-2019, 03:28 PM

Yes, the battery switch is turned on and the batteries are showing 80 percent and the light in the trailer is showing three instead of four.

**bikendan** · 11-10-2019, 03:54 PM

Quote:

Originally Posted by micro_jul

Yes, the battery switch is turned on and the batteries are showing 80 percent and the light in the trailer is showing three instead of four.

You need to test the batteries with a multimeter and not rely on the idiot lights.
And leave the RV unplugged from shore power for an hour or two, before testing.
AND normally when you turn a battery disconnect switch ON, it disconnects the batteries from the converter/charger so the batteries aren't getting recharged.

micro_jul · 11-10-2019, 05:04 PM

I apologize for not being clear. I don't know the proper terminology for any of this. We tested the batteries with the multimeter. That is where the 80 percent figure came from. I guess saying the battery switch is turned on is incorrect. The batteries were connected and should have been charging. This is how we have always kept the trailer and the problem only started when we replaced the batteries. We took the batteries to the place where we bought them and they tested the batteries and said they were just a little less than fully charged. They kept the batteries to charge them and we will have them back shortly. We cleaned the connections around the batteries. We will see if that fixes the problem.

boondocking · 11-10-2019, 05:49 PM

Check the voltage at the battery cables while plugged in and no batteries installed. If the voltage is below 13+ volts then the reverse polarity fuses at the converter are possibly blown. Possibly from the new batteries being installed incorrectly.

tomkatb · 11-10-2019, 07:18 PM

If you intend to depend on batteries much you need a good battery monitoring gage. I have a Bluetooth voltmeter from Amazon.

Fully charged batteries, several hours after charging are 12.6 volts.

When charging with a converter, onboard charger, they will be at several voltages.

Dead battery. 14 or so. Also most converters will employ a cooling fan.

Normal charge. About 13.5 volts.

Trickle charge. 13 volts or so.

They have a surface charge of more after charging. Got to know.

Plugged in you need to check it out. Maybe the converter is bad. Maybe there is a blown fuse. Loose wire.

You need to watch the gage. My voltmeter sends warnings.

All rv’s have some battery usage called parasitic loads. Like, carbon monoxide alarm, smoke alarm, radio time and others. This if the battery is connected it is always discharging.

So we flip the disconnect when parked in storage. Assumes you have one.

Furnaces are big power users. All refrigerators use power.

Got to learn what you need per day and get the right size batteries. Residental fridges eat batteries quickly.

Watts=amps x voltage. Got to understand the math. A single battery has about 40-50 available amps. Not a lot.

Everyone’s situation is different. Your situation is common. Find someone nearby to help.

**Bama Rambler** · 11-11-2019, 09:33 AM

Quote:

Originally Posted by micro_jul

I apologize for not being clear. I don't know the proper terminology for any of this. We tested the batteries with the multimeter. That is where the 80 percent figure came from. I guess saying the battery switch is turned on is incorrect. The batteries were connected and should have been charging. This is how we have always kept the trailer and the problem only started when we replaced the batteries. We took the batteries to the place where we bought them and they tested the batteries and said they were just a little less than fully charged. They kept the batteries to charge them and we will have them back shortly. We cleaned the connections around the batteries. We will see if that fixes the problem.

Don't worry about using the proper terminology. As long as you can convey what you mean we'll help you figure out the terminology as you go.

We normally look for actual voltage numbers when we ask for readings. so something like 12.5 volts would be expected and not 80%.

Saying the battery switch is turned on may be correct, if you're talking about the battery disconnect. If it was on (I prefer closed) then the batteries should be charging when plugged into shore power.

Now for the part I highlighted! We see problems a lot when people unhook and rehook or replace batteries. A lot of times they inadvertently get connected backwards even if for an instant. That blows the reverse polarity fuses in the converter, and then the batteries don't get recharged. Do you know where your converter is? Do you know where the power panel is?

Another thing replacing the battery(s) sometimes does is trip the resettable fuse near the battery(s). It's usually under to tongue or on the frame of the RV.

micro_jul · 11-11-2019, 11:51 AM

How do I reset the fuse near the battery? I took it out and it looked okay, so I put it back in.

AudiDudi · 11-11-2019, 11:56 AM

Quote:

Originally Posted by micro_jul

How do I reset the fuse near the battery? I took it out and it looked okay, so I put it back in.

Looks can be deceiving. Did you use a meter to check it? What voltage do you have on either side of the fuse?

boondocking · 11-11-2019, 11:59 AM

Did you check the voltage at the battery cables while plugged in and no batteries installed? If the voltage is 13+ volts then the reverse polarity fuses and the resettable "fuse" (circuit breaker) are okay.

**wmtire** · 11-11-2019, 12:08 PM

This may help explain the reverse polarity fuses

http://www.forestriverforums.com/for...ml#post2215949

**Bama Rambler** · 11-11-2019, 01:59 PM

Quote:

Originally Posted by micro_jul

How do I reset the fuse near the battery? I took it out and it looked okay, so I put it back in.

Was it a regular blade fuse or a resettable breaker type fuse.

If it was a resettable fuse like below, see the little black button? Press it in to reset it.

frozen · 11-11-2019, 02:34 PM

I have a new motorhome and am learning how to make everything work. For winter storage, I switched off the inverter. I plugged into shore power to charge batteries. Nothing happened until I remembered it's an inverter/charger. With inverter on, batteries charge.

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