AGM battery life and solar panels

[Mark Meadows]

Hi all, What is the best way to make sure my AGM batteries last the longest. I saw something about turning the solar system off once the batteries reach 12.5 volts but Im not sure when (what voltage) I would start the Solar System to charge them up again. I keep my trailer at my home so its easy fro me to monitor . So far I’ve been allowing the batteries to charge with the solar panels non stop.   Thanks for any suggestions 

[MAX Burner]

Your solar charge controller should handle that charging profile for you.  Depending on the type of controller you have, MPPTs probably use a better AGM charging profile than the PWM type controller.  Either way, the controllers should be configured to their specific AGM setting.  

We had AGMs in our previous camper and used a Blue Sky MPPT solar charge controller wired with 10AWG wires from the controller to the battery bank.  Our solar modules would provide enough energy for a 13.6vDC bulk charge to the bank on a good sunny day then drop to a about 13.2v for a float charge after 13.6v was reached.  But all charging profiles and systems are not the same...

Suggest you contact the battery manufacturer and inform them of the type of controller you have and ask them for their recommendation.  

[Mark Meadows]

Thank you very much!  I’m glad to hear that and I’ll check with the manufacturer to be sure

[John Dorrer]

Mark, the one major thing that is the most critical with AGM batteries is that you never allow them to go below 12.2. All it takes is one time to damage or ruin them. Solar is a big help, and you should get A battery charging via the truck alternator when driving. It would also be good to have a generator, if you are boondocking.

 

I got 5 years out of my AGM's on my Truck Camper and did things by the book. When I stored the truck camper it was covered and the battery cut-off turned off. There are parasitic draws, so I eliminated that. Every 6 weeks I took a portable solar panel over and plugged it in. 6 weeks later, batteries were at 12.6.

If boondocking in cold weather and you let your batteries get too low, your furnace will shut down.

AGM's aren't forgiving, so never let them get below 50%. I used 12.3 as my safety bottom line. Hope this helps.

 

 

 

[skalywag]

I have also just let the solar panels maintain the Lifelines and on the average they show about 13.8-13.6 Volts. Going strong after 6.5 years now.

[SeaDawg]

I'm on year 7 with our DEKA/east penn AGM 12v batteries.  Ryan at Blue Sky gave us the correct setting for our controller. I think the solar panels actually help with the longevity of the batteries.  I'm not sure why anyone would advise you to turn off the solar. I try to not run mine below 70 per cent, keeping that last twenty as a safety net. Definitely keep them above 50 per cent.

Even our flooded lead acid 6v batteries on the boat have managed over 7 years, with six+ years of solar, even after flattening one battery bank of 6 when we lost our alternator on a 300 mile race. (We added the solar after that incident. We were very lucky to be able to bring them back to life,  as they were only a month old  then,  and not cheap. ) 

 

[Mark Meadows]

On 2/9/2024 at 12:34 PM, John Dorrer said:

Mark, the one major thing that is the most critical with AGM batteries is that you never allow them to go below 12.2. All it takes is one time to damage or ruin them. Solar is a big help, and you should get A battery charging via the truck alternator when driving. It would also be good to have a generator, if you are boondocking.

 

I got 5 years out of my AGM's on my Truck Camper and did things by the book. When I stored the truck camper it was covered and the battery cut-off turned off. There are parasitic draws, so I eliminated that. Every 6 weeks I took a portable solar panel over and plugged it in. 6 weeks later, batteries were at 12.6.

If boondocking in cold weather and you let your batteries get too low, your furnace will shut down.

AGM's aren't forgiving, so never let them get below 50%. I used 12.3 as my safety bottom line. Hope this helps.

 

 

 

Thank you John! That does help. I have this f-150 that I can plug into at night to keep my batteries charged.  Once I get back home I’ll start a routine similar to what you’ve outlined. 

[ScubaRx]

We got 7 years out of the original AGM’s that came in Hull #050. At home it was always plugged in and on the road the solar took care of it, always returning them to full charge everyday. I would never turn any of the chargers off. 

[dewdev]

On 2/12/2024 at 6:59 PM, Mark Meadows said:

Thank you John! That does help. I have this f-150 that I can plug into at night to keep my batteries charged.  Once I get back home I’ll start a routine similar to what you’ve outlined. 

 I keep the Ollie outside in the winter here in Maine and the solar panels get sun most of the day (when the sun is out). The batteries are almost always at 100%. or close to it. If we get more than 3" of snow, I brush off the snow so the panels are always providing peak power. It seems that even with 3" of snow or ice on the panels, they  are still providing some energy. When the sun is out, the panels warm up enough to melt the snow on the panels if it is not to deep on the panels. Even on cloudy days the panels are providing a small amount energy. 

Over the last 3 years of ownership, I have been very impressed with the solar panels  on my Ollie. So much so that I am adding solar panels to the roof of my home.

[SeaDawg]

Agm, and fla batteries really do best when not fully discharged to 50 per cent  limits, and fully charged daily. I think that's why our solar has given us "extra life" on both the boat and trailer batteries.  

Lithium is much more forgiving on deep discharge,  and only occasionally brought back to 100 per cent. Lithium, in my experience,  actually likes hanging out somewhere in the 75 to 80 per cent zone, which is a slow death for lead acid batteries.  Different chemistry,  different quirks.

 

[SeaDawg]

4 hours ago, dewdev said:

Over the last 3 years of ownership, I have been very impressed with the solar panels  on my Ollie. So much so that I am adding solar panels to the roof of my home

Smart move. You can still get significant tax credits. 

We haven't had a power bill in nine years since installing solar. (Just the connection/grid fees). My home system paid for itself a few years ago. I encourage all my friends to install rooftop solar, and many have. 

[jd1923]

When out in the wild, if you need to run your batteries less than 50% (lead-acid, AGM or whatever), just use the power you need for the night. An occasional down to 40% or less will not kill your batteries. Please just ENJOY your travels!

I have an old 1992 Lexus SC400, an amazing rear wheel drive luxury sports car, a DR HT, with a brand new battery. It is an old car, and sometimes if I or Chris do not close the doors completely, an interior light will be on overnight. I have often found this car, 2-3 days later, with the battery discharged down to 3V, DEAD! Then I charge it slowly over the next 1-2 days, and all is good! Drove it again today, even though this has occurred 4 times.

We all get hung up on what is BEST, but your batteries will be fine! Just try to enjoy your outing, without the anxiety.

[SeaDawg]

In my experience,  many systems will have a "safety cutout" somewhere around 10.6 to 12v.  Furnace won't work. 3way fridge won't work. To protect the battery.

I've actually never seen a battety at 3v. Good on you that you brought it back.

We have brought back batteries at 10 and 10.5 v.  They were fairly new, which probably helped. 

 

 

[MAX Burner]

JFWIW:  Regarding solar - surely we've all read many similar threads regarding the "output" of solar modules.  

However, for those who are new to this RV topic and are on their "front-end" of learning about solar modules, it's important to remember that a given module's output rating is under optimum conditions and in some cases purely theoretical.  

For example, the Oliver-factory flat-mounted modules on our Hull #226 are rated to 170w output each - 340w total.  On a good summer day at noon with high sun angle, no obstructions, we might measure 290w.  If we added the ability to tilt the flat modules (an easy mod/just haven't got around to it yet), we suspect that they'd yield an additional 20-25w.   For another example, at noon today (2MAR) we're experiencing a fairly low sun angle with no obstructions and the flat mounted modules were generating 236w, this was the highest yield during the day:

So, when you find yourself asking how much solar do I need for my style of camping - consideration should be given to the storage capacity (AH's) of one's battery bank, background DC power consumption during solar charging times, solar panel tilt, efficiency/type of solar controller, time of year most camping is done (sun angle factor), and even latitude above equator (another sun angle factor) most camping is done.  These considerations will guide you to correct balance of solar output and battery bank storage capacity for a given style of camping.  A given system will behave totally differently while boon docking during an Alaskan summer as compared to the same time of year in the Rockies.

There's many YouTube presentations regarding this calculation that can be found to help solve anyone's particular solar/battery size needs.  The below video could be a good start for a someone new to solar:

 

[Mark Meadows]

On 3/2/2024 at 1:08 PM, MAX Burner said:

JFWIW:  Regarding solar - surely we've all read many similar threads regarding the "output" of solar modules.  

However, for those who are new to this RV topic and are on their "front-end" of learning about solar modules, it's important to remember that a given module's output rating is under optimum conditions and in some cases purely theoretical.  

For example, the Oliver-factory flat-mounted modules on our Hull #226 are rated to 170w output each - 340w total.  On a good summer day at noon with high sun angle, no obstructions, we might measure 290w.  If we added the ability to tilt the flat modules (an easy mod/just haven't got around to it yet), we suspect that they'd yield an additional 20-25w.   For another example, at noon today (2MAR) we're experiencing a fairly low sun angle with no obstructions and the flat mounted modules were generating 236w, this was the highest yield during the day:

So, when you find yourself asking how much solar do I need for my style of camping - consideration should be given to the storage capacity (AH's) of one's battery bank, background DC power consumption during solar charging times, solar panel tilt, efficiency/type of solar controller, time of year most camping is done (sun angle factor), and even latitude above equator (another sun angle factor) most camping is done.  These considerations will guide you to correct balance of solar output and battery bank storage capacity for a given style of camping.  A given system will behave totally differently while boon docking during an Alaskan summer as compared to the same time of year in the Rockies.

There's many YouTube presentations regarding this calculation that can be found to help solve anyone's particular solar/battery size needs.  The below video could be a good start for a someone new to solar:

 

Thank you very much! Good information to have!