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Old 04-07-2018, 03:07 AM   #1
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Default AGM Battery Charging and keeping the battery charged from AC continuously

Hi everyone,

I'd really like advice on if I can keep my new Class B constantly plugged into shore power. I like the idea of being ready to go at a moment, but the tech guy at our dealer said that wasn't a good idea for the batteries.

When he told me this, I was rather disappointed - I'd had sailboat for 30 years and always plugged into shore power at the marina to keep the batteries in top shape.

Thanks for your comments, please go easy on me...this is my first RV, I've had a sailboat for 30 years.

Rebecca
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Old 04-07-2018, 03:16 AM   #2
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It depends on what the RV is using to charge/maintain the batteries. Get that information and post it here so folks can help. My RV uses a converter made by Progressive Dynamics. I leave my van plugged in whenever I'm not driving it.
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Old 04-07-2018, 04:17 AM   #3
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We keep ours plugged in when parked in the driveway. As Eric said, it depends on the charger/converter. The one in the toyhauler we had before the Winnie would start out at 14.7 volts, and after several hours drop to 13.3. Better than staying at 14.7 all the time, but too high to leave an AGM battery connected all the time. But the converter in our Winnie drops to 13 volts and stays there once the battery is fully charged. 13V is perfect for maintaining an AGM battery.
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Old 04-07-2018, 04:54 AM   #4
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If you park outdoors, even a modest solar panel with a good controller will keep your battery healthy and ready to go. Our old rig did not have solar, so I kept it plugged in whenever possible. Now that we have a panel, I don't bother.

This assumes you have flooded or AGM batteries. If you have lithium and park in cold weather, you will need shore power when it is cold to protect the battery. This is one of the major disadvantages of lithium.
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Old 04-07-2018, 06:43 AM   #5
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.

The new 3-stage chargers will go into trickle-charge maintenance mode once the battery is fully charged. You can leave the RV plugged in all the time.
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Old 04-07-2018, 04:52 PM   #6
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If you park outdoors, even a modest solar panel with a good controller will keep your battery healthy and ready to go. Our old rig did not have solar, so I kept it plugged in whenever possible. Now that we have a panel, I don't bother.
We have solar, but living in the PNW where the days get really short in the winter, and the sun is obscured by clouds for months at a time, solar isn't going to keep the battery topped off.
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Old 04-07-2018, 05:25 PM   #7
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We have solar, but living in the PNW where the days get really short in the winter, and the sun is obscured by clouds for months at a time, solar isn't going to keep the battery topped off.
I'm not sure I believe that. Maintaining a float on a fully-charged battery does not take a lot of power, and your solar is never going to go to zero (except during snow-cover).

I recommend giving it a try next winter. You might be surprised.
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Old 04-07-2018, 05:32 PM   #8
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It depends on what the RV is using to charge/maintain the batteries. Get that information and post it here so folks can help. My RV uses a converter made by Progressive Dynamics. I leave my van plugged in whenever I'm not driving it.
The Galleria 24 has a 2000 Watt Xantrex Freedom XC Series Inverter Charger, the battery is a 330 AMP AGM Battery REV-8D-330, R4000 series (Relionbattery.com).

There's also a 100 Watt Solar panel.

Thanks everyone for your input! For those who leave the RV plugged in to shore power, do you leave the refrigerator/freezer on all the time?
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Old 04-07-2018, 05:54 PM   #9
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I'm not sure I believe that. Maintaining a float on a fully-charged battery does not take a lot of power, and your solar is never going to go to zero (except during snow-cover).

I recommend giving it a try next winter. You might be surprised.
I wasn't sure if the solar could keep up with all of the little things in the van that can't be turned off unless you hit the battery disconnect switch: the stereo display, the little blue LED lights in every USB outlet, the control panel, the propane gas detector, etc.

It is really dark here in the dead of winter. The sun is very low on the horizon, and my house is on the north side of a hill, plus my back yard is shaded by tall cedars and hemlocks. Add in the constant cloud cover, and there really isn't much light.
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Old 04-07-2018, 05:55 PM   #10
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The Galleria 24 has a 2000 Watt Xantrex Freedom XC Series Inverter Charger, the battery is a 330 AMP AGM Battery REV-8D-330, R4000 series (Relionbattery.com).

There's also a 100 Watt Solar panel.

Thanks everyone for your input! For those who leave the RV plugged in to shore power, do you leave the refrigerator/freezer on all the time?
Fridge off, doors closed, with a box of baking soda in fridge and freezer.
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Old 04-07-2018, 06:17 PM   #11
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I have 230Ah AGMs, 300W solar, electric fridge. After cold night, with the D2 diesel heater going, batteries are at 100% SOC before noon next day on average in Oregon. Certainly, open sky campsite is a must.
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Old 04-07-2018, 07:47 PM   #12
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If you park outdoors, even a modest solar panel with a good controller will keep your battery healthy and ready to go. Our old rig did not have solar, so I kept it plugged in whenever possible. Now that we have a panel, I don't bother.

This assumes you have flooded or AGM batteries. If you have lithium and park in cold weather, you will need shore power when it is cold to protect the battery. This is one of the major disadvantages of lithium.
But why a major disadvantage? It depends on where you live. If you live in any where it stays basically above -4 degrees F with LiFePO4 batteries you would not have to plug in because you don't need battery heat. Newer lithium technologies in RVing like LiFeMgPO4 batteries can withstand cold equal to AGMs. Even in Minnesota it is a rare day where you would absolutely have to plug in when the coldest average January 24 hour temperature is 12 deg. F. Seems most all with lead acid flooded or AGMs when stored outside plug in to shore power for convenience anyway. Heck I keep mine plugged in in a heated garage now just for the many conveniences. I suspect most all by code have a 15A outlet on the outside of their house and that's all that is needed and not the RV standard of 30A. Lithium batteries don't accept a charge when the batteries are below freezing. That's may be an inconvenience but Winnebago says the Revel should heat the batteries above freezing in a couple of hours after you run the engine. So maybe you would be inconvenienced for the first two hours of a trip. I imagine that would be an extremely rare occurrence. Of course you have to have lithium battery technology to experience and know this.
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Old 04-07-2018, 07:58 PM   #13
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I do think that being plugged in all the time is fine, but I would also say that many of the smart chargers have a float voltage that is a bit high for continuous float use. It appears the voltages have been chosen based on older specs or perhaps because in cyclic use it does a better job of getting the batteries more full and longer lasting. Whatever it is, it is good to be aware of what is going on. The current specs for the better AGM batteries, like Lifeline, have been slowly lowering the float voltages or even recommending a separate, lower voltage for "storage" with occasional recharge bump ups. There are numerous chargers around that do it various ways, everything from settable float voltage, to storage stage, to shutting off charging completely and then doing a recharge periodically, etc. I think all of that kind of charge works well. I don't think I would want to float all winter at 13.5-13.6v continuous though. I have our charger set to float at 13.1/13.2v on our Lifeline batteries.

There is also a caution to be aware of if you use solar to keep your batteries topped off over the winter. Many of the solar chargers do a full charge cycle every day, regardless of how full the batteries are. That can mean a full absorption voltage charge of 14.4v or so for 4 hours every day on top of full batteries. This is not good for the batteries at all, and there have been folks that have destroyed their batteries this way while sitting over the winter. It can be particularly bad if you are plugged in to shore power besides, as you guaranty that the batteries will get a charge cycle on top of full from the solar. If any of these situations apply to your solar charger, you may want to get a different one that won't overcharge this way, or disconnect it if you are going to be plugged in.
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Old 04-07-2018, 10:32 PM   #14
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I wasn't sure if the solar could keep up with all of the little things in the van that can't be turned off unless you hit the battery disconnect switch: the stereo display, the little blue LED lights in every USB outlet, the control panel, the propane gas detector, etc.

It is really dark here in the dead of winter. The sun is very low on the horizon, and my house is on the north side of a hill, plus my back yard is shaded by tall cedars and hemlocks. Add in the constant cloud cover, and there really isn't much light.
I have our rig wired such that two things are wired upstream of the main battery disconnect: (a) the solar charger; and (b) the Trik-L-Start. During storage, I shut off the main disconnect, so nothing is powered except those two items. That way, all batteries are kept at float. I am still betting that ambient daylight would be enough with such a setup. It certainly is in Pennsylvania, which doesn't exactly have sunny winters, either.
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Old 04-08-2018, 02:41 AM   #15
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...Thanks everyone for your input! For those who leave the RV plugged in to shore power, do you leave the refrigerator/freezer on all the time?
Fridge off, door open. The door latch has a second position that secures the door open about an inch. Roof vent open a crack. It has a cover that keeps rain out even when it's open.
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Old 04-08-2018, 08:24 AM   #16
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I have our rig wired such that two things are wired upstream of the main battery disconnect: (a) the solar charger; and (b) the Trik-L-Start. During storage, I shut off the main disconnect, so nothing is powered except those two items. That way, all batteries are kept at float. I am still betting that ambient daylight would be enough with such a setup. It certainly is in Pennsylvania, which doesn't exactly have sunny winters, either.
My solar charge controller is also wired upstream of the main disconnect relay. Last year I left the van in the garage but forgot to disconnect the solar charge controller and after 3 month of absence my house batteries were almost dead. Since, I disconnect the solar controller, in fact I have a check list before the trip:

1. Disconnect Sprinterís main battery
2. Disconnect batteries with Intellitec main relay
3. Disconnect PV controller.
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Old 04-08-2018, 10:36 AM   #17
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My solar charge controller is also wired upstream of the main disconnect relay. Last year I left the van in the garage but forgot to disconnect the solar charge controller and after 3 month of absence my house batteries were almost dead. Since, I disconnect the solar controller, in fact I have a check list before the trip:

1. Disconnect Sprinterís main battery
2. Disconnect batteries with Intellitec main relay
3. Disconnect PV controller.
Our solar controller is also on the the battery side of the main disconnect.

There was a very long and interesting discussion of where the controller should connect on here a number of years ago. The determining factor that took precedence was that you never wanted the solar controller connected to the van unless it was being powered by the batteries first so that you will not get a big voltage spike when it is connected. What apparently can happen is that if you are in the sun so the panels have output, but the controller doesn't have a battery connected to it, the controller output can go to higher than desired voltage and damage things that are connected to it. Even if it connects to the coach with the battery disconnect switch so a battery comes online at the same time as the connection to the van, you can get a big spike, it appears.

For the above reasons, our controller is always connected to the batteries, unless we pull the fuse to it so no power used in the van. We also have a toggle switch on the panels, so we can turn them off as an added layer of caution if the controller is disconnected from the batteries.
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Old 04-08-2018, 03:16 PM   #18
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I sure been learning a LOT in a short amount of time! On our new Galleria, the Go Power solar is always on and connected to the battery, in fact there isn't an off switch. The Battery Disconnect switch doesn't affect the solar charger.

Taking a look at the Owner's Manual, the section on the batteries says:

"It is important to keep the batteries fully charged at all times. Take time to turn off all lights or other 12VDC conveniences when not in use. To prevent draining the batteries, connect the motorhome to a 120VAC power source whenever possible.

The charge condition of the batteries is displayed on the Go Power! Solar monitor panel located in the Control Center, mounted on the wall. To check, press the "B" button to toggle between coach and chassis battery levels and voltage."

Thanks everyone for taking the time to reply!

Rebecca
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Old 04-08-2018, 03:42 PM   #19
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I live in massachusetts and store my agm battery zion outside in winter. i check my solar panel controller lights once weekly. 5 months of winter for 3 straight winters has kept my agm topped off.

I do not know how sunlight in winter differs from pacific northwest to massachusetts.
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Old 04-08-2018, 04:04 PM   #20
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I just took a quick look at one of the Go Power solar controllers to see what they say about charging profiles and controls.

Here is the part of the manual that gives a bit of information about the profile.



If I am reading this correctly, it will only charge at bulk/absorption for 30 minutes a day, unless the battery is under 1/2 full approx, then it will go for an hour. It is possible they lost something in the writing and it might really mean 30 minutes of absorption after the bulk gets it to the absorption voltage, but doesn't say that. It is still a short time for getting batteries full, but it also going to run every day, even if plugged in, so then too long. If plugged in, I would pull the fuse on the solar if it is outside in the sun.

It also will float at 13.7v, which IMO is to high for long term storage, so another reason to not have the solar on in storage if you can get plugged into shore power.

The unit does appear to have a "boost" feature to put it back into absorption voltage manually, which would be good to use when you need to get your batteries full while camping, but you would need to have a battery monitor to tell if they are really full or not.

Perhaps someone who has one of the Go Power controllers will have some better information of how they actually control the charging.
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