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Old 01-19-2020, 03:55 PM   #1
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Is it a good or bad idea to leave your RV connected to shore power?

From a house battery standpoint, is it better to be on shore power or let your solar panels system keep your batteries charged?

My RV batteries have been a little strange the past few days...

First, they went down to 10.6 volts with just the fantastic fan on. I was plugged into shore power and then later disconnected it.

Now, it's charging normally and holding at 12.9 to 13 volts...

Yesterday evening when the sun went down, the system went back down to 11.9 volts...

I think that my AGM batteries are dying, they are only 30 months old.... which does surprise me... but, then again, many people who I know say that is normal?

I'm thinking, just replace the batteries again 😡.
Any ideas?
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Old 01-19-2020, 04:06 PM   #2
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Double-check to insure all cable connections are clean and tight,including at inverter/charger; especially ground connections to chassis. Reset all faults stored in the inverter/charger.

What is battery voltage when charging only with solar?
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Old 01-19-2020, 04:28 PM   #3
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Quote:
Originally Posted by MWeiner View Post
From a house battery standpoint, is it better to be on shore power or let your solar panels system keep your batteries charged?

My RV batteries have been a little strange the past few days...

First, they went down to 10.6 volts with just the fantastic fan on. I was plugged into shore power and then later disconnected it.

Now, it's charging normally and holding at 12.9 to 13 volts...

Yesterday evening when the sun went down, the system went back down to 11.9 volts...

I think that my AGM batteries are dying, they are only 30 months old.... which does surprise me... but, then again, many people who I know say that is normal?

I'm thinking, just replace the batteries again ��.
Any ideas?
As Ray says, check everything. If all seems well, this may help ..........

All lead-acid batteries last longest if maintained fully charged and at their rated float voltage. And, though we are talking about deep-cycle batteries, cycling does take life out. If there is any drain at all on your batteries, you are cycling them by using solar. It might not be deep cycling, but it is cycling. Plugging the RV in at home and keeping the converter on should hold your batteries at float voltage with the converter picking up all loads, parasitic or otherwise. This will maximize life because the battery sits at 100% 24/7.

Getting only 30 months out of lead-acid batteries is not unusual especially when using solar for most of the charging. The problem is not getting back to 100% charge each day. There are two key issues. One is that the second stage of charging, the "absorption" stage, typically takes more hours than the solar provides. On long summer days you might get back to 100% but likely not in the off seasons. What I've found is that the solar doesn't get up to full power until mid morning and so the bulk charging stage (faster charge, gets the battery up to about 85%) can take into early afternoon. That typically does not leave enough hours of sun to complete the absorption stage. The result is only 90 to 95% charge and a battery that is cycled between maybe 60 and 90% rather than 70 and 100% and this is a bit rough on the battery.

Adding more solar helps by getting the bulk stage done earlier, but still might not complete the absorption stage (which is only a few amps in the final hours). When I had lead-acid, I would use the generator first thing in the morning to get most of the bulk charge out of the way and maximize the solar hours available to absorption.

As well, the State of Charge monitor needs to see a true 100% often to be accurate. With not quite getting to 100% charge, most SOC meters will fall behind over time and read higher than actual thus leading one to operate the battery below 100%. The battery needs to be taken to the end of the absoprtion stage to calibrate the SOC meter and often solar isn't able to do that.

Having a good SOC meter and keeping it calibrated will help with battery life, or at least help understand why the life isn't great.
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Old 01-19-2020, 04:58 PM   #4
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As Ray says, check everything. If all seems well, this may help ..........

All lead-acid batteries last longest if maintained fully charged and at their rated float voltage. And, though we are talking about deep-cycle batteries, cycling does take life out. If there is any drain at all on your batteries, you are cycling them by using solar. It might not be deep cycling, but it is cycling. Plugging the RV in at home and keeping the converter on should hold your batteries at float voltage with the converter picking up all loads, parasitic or otherwise. This will maximize life because the battery sits at 100% 24/7.

Getting only 30 months out of lead-acid batteries is not unusual especially when using solar for most of the charging. The problem is not getting back to 100% charge each day. There are two key issues. One is that the second stage of charging, the "absorption" stage, typically takes more hours than the solar provides. On long summer days you might get back to 100% but likely not in the off seasons. What I've found is that the solar doesn't get up to full power until mid morning and so the bulk charging stage (faster charge, gets the battery up to about 85%) can take into early afternoon. That typically does not leave enough hours of sun to complete the absorption stage. The result is only 90 to 95% charge and a battery that is cycled between maybe 60 and 90% rather than 70 and 100% and this is a bit rough on the battery.

Adding more solar helps by getting the bulk stage done earlier, but still might not complete the absorption stage (which is only a few amps in the final hours). When I had lead-acid, I would use the generator first thing in the morning to get most of the bulk charge out of the way and maximize the solar hours available to absorption.

As well, the State of Charge monitor needs to see a true 100% often to be accurate. With not quite getting to 100% charge, most SOC meters will fall behind over time and read higher than actual thus leading one to operate the battery below 100%. The battery needs to be taken to the end of the absoprtion stage to calibrate the SOC meter and often solar isn't able to do that.

Having a good SOC meter and keeping it calibrated will help with battery life, or at least help understand why the life isn't great.
Thank you so much for your reply... I see that you wrote this;

"Getting only 30 months out of lead-acid batteries is not unusual especially when using solar for most of the charging. "

Are you saying that 30 months is pretty standard?

Yesterday, as a test case, I unplugged the RV all day and once the sun went down I discovered that my batteries with the coach unplugged went down to 11.9 and I plugged it back in. It took a while to get back to 100 percent...

Yes, I do have a battery monitoring system...see attached picture.

Okay, so, you're saying that keeping it plugged in is the best way. The only time I have left it unplugged for a long period of time was when I was away for 6 weeks and turned off the entire system with the battery disconnect switch.

I do have a 160 Watt Zamp Solar Panel system and two 6 volt AGM's - 224 amp hours batteries in series....

Yeah, I have had a couple occasions where the system went down to 10.6...on trips and the batteries came back to life..... I try to avoid this....

Finally, I have a small refrigerator drawing 2.2 Amps per hour when it's running....it has been cool so far, I'm concerned that in warmer weather it will be absolutely essential for me to get my batteries in top condition.....

I'm going to take the coach and have the batteries tested...if they are weak, and I expect that they are, I'll just have them replaced.
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Old 01-19-2020, 05:28 PM   #5
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Mine lived outside for two years and the solar panel kept the coach batteries at 100% per the solar management meter. I’ve now moved into my barn and plug in for a couple of days each month to keep the house charged. My coach just failed emissions because apparently I let my chassis battery drift too low and the emissions test requires me to drive 50-100 miles before the test can be done. I figure our upcoming trip to Florida and back will be far enough so I’ll get it re-inspected when we get back. Lesson learned though.
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Old 01-19-2020, 05:47 PM   #6
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Quote:
Originally Posted by MWeiner View Post
Thank you so much for your reply... I see that you wrote this;

"Getting only 30 months out of lead-acid batteries is not unusual especially when using solar for most of the charging. "

Are you saying that 30 months is pretty standard?

Yesterday, as a test case, I unplugged the RV all day and once the sun went down I discovered that my batteries with the coach unplugged went down to 11.9 and I plugged it back in. It took a while to get back to 100 percent...

Yes, I do have a battery monitoring system...see attached picture.

Okay, so, you're saying that keeping it plugged in is the best way. The only time I have left it unplugged for a long period of time was when I was away for 6 weeks and turned off the entire system with the battery disconnect switch.

I do have a 160 Watt Zamp Solar Panel system and two 6 volt AGM's - 224 amp hours batteries in series....

Yeah, I have had a couple occasions where the system went down to 10.6...on trips and the batteries came back to life..... I try to avoid this....

Finally, I have a small refrigerator drawing 2.2 Amps per hour when it's running....it has been cool so far, I'm concerned that in warmer weather it will be absolutely essential for me to get my batteries in top condition.....

I'm going to take the coach and have the batteries tested...if they are weak, and I expect that they are, I'll just have them replaced.
Most under the counter DC fridges draw about 5 amps when running. Is your fridge AC? Are you looking at 2.2 amps AC coming from your inverter? If so that is drawing about 20 amps from your batteries. Not an inconsequential load. And if it is not well insulated, it could be running 50% of the time.
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Old 01-19-2020, 05:48 PM   #7
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Allowing the batteries to drop to 10.6V will certainly reduce their life.

Ideally, you only want to allow them to get to about 12.0V (with no load on them), before charging them back up.
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Old 01-19-2020, 05:58 PM   #8
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Refrigerator is only 2.2 Amps when running, no inverter

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Most under the counter DC fridges draw about 5 amps when running. Is your fridge AC? Are you looking at 2.2 amps AC coming from your inverter? If so that is drawing about 20 amps from your batteries. Not an inconsequential load. And if it is not well insulated, it could be running 50% of the time.
My inverter is turned off..... the refrigerator is 12 volt.... doesn't need to be on the inverter...
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Old 01-19-2020, 06:48 PM   #9
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I understand....

Quote:
Originally Posted by 96 Wideglide View Post
Allowing the batteries to drop to 10.6V will certainly reduce their life.

Ideally, you only want to allow them to get to about 12.0V (with no load on them), before charging them back up.
You're right, and it has happened a couple of times.....

Once very early with these two new batteries in 2017, we were in a place with no electricity.... and before the Victron BMV battery monitoring system..... I was relying on the Zamp Solar Panel system display....by the way, Zamp Solar systems told me that they are NOT going to have this voltage monitor on their new units... they admitted to me that they are very inaccurate.....

Anyway, we were watching TV and I had the inverter on...it did go to 10.6 volts....😡😡😡. It did recover.... that was 2017.....

Now, the other day, I had the vehicle plugged in and just ran the fantastic fan... my refrigerator is on 24/7.....and I didn't expect any interruption in the shore power, but, there might have been a loose connection.....it went down to the 10.6 level.....

I plugged it in and it eventually charged up......so, it's been a little difficult to get a handle on what's going on exactly...

After I get the batteries tested, I will know more....

I don't know, maybe 30 months is just about what anyone can expect??? The batteries came with a 24 months warranty....go figure..
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Old 01-19-2020, 07:38 PM   #10
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Found this little information online

Found this information....

"There are a few things you can do as an owner to maximize the life expectancy of your deep cycle battery. To extend the lifespan, you should cycle the battery down to 50 percent discharge before recharging it every time. "

Is this constant trickle charging ruining my battery bank???

I'm always topping off the batteries with the solar panel system.... I hope this is not a bad idea???

I can't imagine this being bad with all the solar panel systems out there...
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Old 01-19-2020, 10:10 PM   #11
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That doesn't even agree with the manufactures.

Here is a depth of discharge chart. Shallow discharged equal longer battery life.

PS: trickle charging is not actually charging, its maintaining the charge.Click image for larger version

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Old 01-20-2020, 04:03 PM   #12
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Quote:
Originally Posted by MWeiner View Post
Thank you so much for your reply... I see that you wrote this;

"Getting only 30 months out of lead-acid batteries is not unusual especially when using solar for most of the charging. "

Are you saying that 30 months is pretty standard?
That is my experience. And you hear this in the forums from time to time. But this I think applies to those of us that cycle our batteries often. That's definitely the case for me.

If you are dry camping a lot and putting cycles on your batteries over some months of the year, then 30 months isn't unreasonable. If you cycle them only a dozen or two times per year and stick with 50% lower limit, 30 months is on the low side. With virtually no cycling and proper maintenance less than 5 years would be surprising.

Quote:
Originally Posted by MWeiner View Post
Yesterday, as a test case, I unplugged the RV all day and once the sun went down I discovered that my batteries with the coach unplugged went down to 11.9 and I plugged it back in. It took a while to get back to 100 percent...
If you find no other problems it does sound like your batteries are at end-of-life.

Quote:
Originally Posted by MWeiner View Post
Yes, I do have a battery monitoring system...see attached picture.

Okay, so, you're saying that keeping it plugged in is the best way. The only time I have left it unplugged for a long period of time was when I was away for 6 weeks and turned off the entire system with the battery disconnect switch.
Some battery disconnects leave some things like propane alarm and such connected. Was the battery still charged at the end of that 6 weeks? While letting a healthy battery sit for 6 weeks with zero load should do not much harm, letting a not fully charged battery sit for any length of time does do harm.

Quote:
Originally Posted by MWeiner View Post
I do have a 160 Watt Zamp Solar Panel system and two 6 volt AGM's - 224 amp hours batteries in series....

Yeah, I have had a couple occasions where the system went down to 10.6...on trips and the batteries came back to life..... I try to avoid this....
Ouch. 12.1-12.2 volts is around 50% charge and conventional wisdom is going lower eats up life quickly. You can take a battery down to 10.6V a few times and knock off only a year of life, but any more than that and it adds up quickly. BTW, as others have posted, if this 10.6V was with no load on the battery and the battery sitting a while, it was severely discharged. If 10.6V is with a coffee maker or some such operating, the battery is low but not near zero charge.

Quote:
Originally Posted by MWeiner View Post
Finally, I have a small refrigerator drawing 2.2 Amps per hour when it's running....it has been cool so far, I'm concerned that in warmer weather it will be absolutely essential for me to get my batteries in top condition.....

I'm going to take the coach and have the batteries tested...if they are weak, and I expect that they are, I'll just have them replaced.
2.2 amps over 24 hours is over 50 AH which is a good chunk of energy. Have you ever monitored your total daily usage when off-grid? Ideally you want to go no longer than 50% and get back to 100% the next day. Getting back to 100% is the tough part. I'm a 100% dry camper and doing about 4 months at the time when I had lead-acid, I usually did not get them back to 100%. Then there's the problem of keeping the SOC meter calibrated. Uncalibrated by a true 100% charge (not 100% as indicated by the SOC meter) an SOC meter can destroy a lead-acid battery.
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Old 01-20-2020, 10:43 PM   #13
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It's my guess that this isn't a "failure" but a good example of what happens in a mixed-use case. The OP described varied shallow and deep discharges and charge cycles, so the batteries have been operated at some less than ideal state of charge for an extended period.

In a perfect world you'd use batteries "gently" then immediately recharge them with a picture perfect data sheet charge profile. You'll never get them hot, you temperature compensate when cold, and below 50% SOC is a line you'll never cross or go straight to battery jail.

The real world doesn't match the data sheets. You're going to overcharge, undercharge, drain them dry and blast them full. Especially with solar, you're not going to get an ideal charge profile every cycle and if there are any loads on the bank at all, you'll be short cycling the bank every day. All of these little "insults" in concert, let alone just one of them affects battery longevity.

I'd be leery of letting a shop "test" my batteries unless they either have a sophisticated battery impedance tester with battery specific model profiles, or they do a full blown measured capacity test. You can do a capacity test yourself at home, and not have to wonder if they're just doing a quick once over which may not reveal the true merit of the batteries. You can always just shotgun it and replace them outright and see, but I would want to know how the batteries were performing and verify other operating parameters before I started swapping out things. If you don't investigate and understand why things are happening with the set you have, you'll only repeat the scenario with a new set.

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Old 01-20-2020, 11:37 PM   #14
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It's my guess that this isn't a "failure" but a good example of what happens in a mixed-use case. The OP described varied shallow and deep discharges and charge cycles, so the batteries have been operated at some less than ideal state of charge for an extended period.

In a perfect world you'd use batteries "gently" then immediately recharge them with a picture perfect data sheet charge profile. You'll never get them hot, you temperature compensate when cold, and below 50% SOC is a line you'll never cross or go straight to battery jail.

The real world doesn't match the data sheets. You're going to overcharge, undercharge, drain them dry and blast them full. Especially with solar, you're not going to get an ideal charge profile every cycle and if there are any loads on the bank at all, you'll be short cycling the bank every day. All of these little "insults" in concert, let alone just one of them affects battery longevity.

I'd be leery of letting a shop "test" my batteries unless they either have a sophisticated battery impedance tester with battery specific model profiles, or they do a full blown measured capacity test. You can do a capacity test yourself at home, and not have to wonder if they're just doing a quick once over which may not reveal the true merit of the batteries. You can always just shotgun it and replace them outright and see, but I would want to know how the batteries were performing and verify other operating parameters before I started swapping out things. If you don't investigate and understand why things are happening with the set you have, you'll only repeat the scenario with a new set.

Mark B.
Albuquerque, NM
I think you might be absolutely correct when you said that you were "guessing". I don't guess . I hire professionals to check things out....

What makes you think I won't get this as you stated below, I don't know what would make you so skeptical?

The batteries are 30 months old, and, I haven't cycled them as many times as you think.... doesn't matter.

They are not holding a charge after they are not on shore power; and under load.


I'd be leery of letting a shop "test" my batteries unless they either have a sophisticated battery impedance tester with battery specific model profiles, or they do a full blown measured capacity test.

It's true that I'm rather new to RVs, although, I'm learning something new all the time....

My 160 watt Zamp Solar Panel system keeps the batteries topped off and I just got the new 12 volt DC refrigerator in the last 4 months....up until recently I didn't have any issues...

As per "short cycling", the battery people told me that keeping them as charged as possible is always preferred....

Yeah, a few years ago early on I did run the system too low for a an hour or so...my error...

I'm going to get it all checked out.
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