RV Trip Planning Discussions

Go Back   iRV2 Forums > MOTORHOME FORUMS > MH-General Discussions & Problems
Click Here to Login
Join iRV2 Today

Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts.
Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on iRV2
 
Thread Tools Search this Thread Display Modes
 
Old 10-22-2019, 02:17 PM   #1
Member
 
murphylawe's Avatar
 
Fleetwood Owners Club
Join Date: Oct 2016
Posts: 41
The Long & Short of Battery Choices...

Hey Everyone,

I am working on a solar installation and had to do a lot of research on batteries. This is NOT an RV Solar System post, but rather a discussion regarding batteries in general.

In the world of RV batteries there are three major types based on technology and chemistry.

The first type are 'Wet-Cell', first invented in 1868... an absolutely reliable technology that is still used today. Wet Cell batteries are heavy, require weekly maintenance, and can only discharge ~40-50% of their load. This means to have 400 Amp Hours of storage you would need at least 800 ah of bulk storage.

They also require ventilation as hydrogen gas is created along with corrosion on the terminals. Additionally, of the three battery types, these have the fewest charge cycles.

The Wet-Cell's saving graces are its reliability and that they are much less expensive than the other three types.

AGM or Acid Glass Mat batteries were developed in the 1980's and use acid like 'Wet-Cells' but the chemistry is different, so these batteries are sealed and do not 'Out Gas' like wet cell batteries, requiring little ventilation. Like the wet-cell battery the depth of discharge is ~40-50%, so ya need about double or more of your usable amp hours. They are also even heavier than wet-cell batteries and cost twice as much.

They do have a wider operating range than wet-cell and can be place on their sides. However they will operate for much longer than wet-cell, thousands of charge cycles.

The final type, and Holy Grail for RV'ers is the Lithium-Iron Phosphate (LiFePO4) battery. It offers an amazing 80-90% depth of discharge and is about half the weight of wet-cell and nearly a third of the weight of AGM batteries. They offer a decade of service over and ten-thousand of charge cycles (in some cases). Wowie, zowie... my problems are solved!!!

Urrrkkk! Not so fast, LiFePO4 batteries are insanely expensive:
  • Wet-Cell 12V/100AH Battery = $110
  • AGM 12V/100AH Battery = $199
  • LiFePO4 12V/100AH Battery =$799

Additionally they require 'SMART' monitors to keep them from freezing, overheating, or overcharging. LiFePO4 batteries operate safely as long as nothing goes wrong... simply overcharging one turns it into a bomb. The fires they start are so hot they can't be extinguished with water. Seeing one burn gave me pause...

Their operating range is also hampered by aversion to cold.

So, after all of the wrangling and soul-searching I had decided on LiFePO4 for the coach... then I had one final thought. I don't know about the rest of you, but I often look at my RV as a 'Bug-Out' vehicle. Last year's forest fires in CA clearly demonstrated how being able to leave an area and still have a place to live is an advantage.

While thinking about this possible future use, I again pondered LiFePO4 and decided against them. I believe the BMS (circuit board) that monitors the health of the LiFePO4 batteries is subject to EMP which is an Achilles Heel. While it isn't much, it was enough to make the decision for AGM.

AGM also make excellent starting batteries!!!
__________________

murphylawe is offline   Reply With Quote
Join the #1 RV Forum Today - It's Totally Free!

iRV2.com RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!

Old 10-22-2019, 02:42 PM   #2
Senior Member
 
Join Date: Jul 2014
Posts: 19,500
Your wrong on a few points.

You can draw down lead acid ( flooded and AGM ) down completely. Leave 10% to 20% as a cushion. ( Same with Lithuim )
It shortens their life by about 1/2.
Check out a cycle life chart avalable online.

AGM batteries have about the same cycle life as flooded batteries, not thousands more.
Again, that will show in a cycle life chart.

Here is one brands chart.Click image for larger version

Name:	Capture%2B_2019-10-22-15-38-51.jpeg
Views:	31
Size:	49.7 KB
ID:	264428
__________________

twinboat is online now   Reply With Quote
Old 10-22-2019, 03:20 PM   #3
Senior Member
 
Join Date: Jun 2004
Posts: 1,034
Quote:
Originally Posted by twinboat View Post
Your wrong on a few points.

You can draw down lead acid ( flooded and AGM ) down completely. Leave 10% to 20% as a cushion. ( Same with Lithuim )
It shortens their life by about 1/2.
Check out a cycle life chart avalable online.

AGM batteries have about the same cycle life as flooded batteries, not thousands more.
Again, that will show in a cycle life chart.

Here is one brands chart.Attachment 264428
Yes you can discharge them below 50% but is it all that practical? The internal resistance of the battery rises sharply and thus the output voltage under load drops significantly. Everything that operates on 12 volts becomes that much more inefficient when forced to function on lower voltage. IMO one of the big advantages of LiFePO is that the voltage curve is relatively flat. And to correct the OP LiFePO's are inherently pretty stable. Fire from overcharging is unlikely. These are not the same chemistry as the batteries that are in your laptop. Lastly if your worried EMI you have a lot bigger concerns in your RV than the BMS in the battery pack.
__________________
2014 Southwind 32VS
2013 Nissan Xterra PRO-4X
PbdBlue is offline   Reply With Quote
Old 10-22-2019, 03:54 PM   #4
Senior Member
 
Join Date: Jul 2014
Posts: 19,500
Quote:
Originally Posted by PbdBlue View Post
Yes you can discharge them below 50% but is it all that practical? The internal resistance of the battery rises sharply and thus the output voltage under load drops significantly. Everything that operates on 12 volts becomes that much more inefficient when forced to function on lower voltage. IMO one of the big advantages of LiFePO is that the voltage curve is relatively flat. And to correct the OP LiFePO's are inherently pretty stable. Fire from overcharging is unlikely. These are not the same chemistry as the batteries that are in your laptop. Lastly if your worried EMI you have a lot bigger concerns in your RV than the BMS in the battery pack.
I wasn't comparing them to Lithium.

Of course they are better at everything.
twinboat is online now   Reply With Quote
Old 10-22-2019, 06:55 PM   #5
Senior Member
 
Join Date: Aug 2017
Location: Syracuse Ut.
Posts: 690
Interesting. EMP testing/certification has been a significant part of what I did for work over the last 40 years or so, but never once has it been a consideration on any of the choices I've made with my personal RV's. Should I worry about the BMS in a lithium battery as part of my solar power system that has a solar controller? The folks I would need to talk to to get my 5er tested are just down the road, but somehow, I can't imagine talking them into testing it, and really wouldn't want to suffer the costs of the test, or subsequent repairs.



Couple side notes:


There are many factors affecting battery life, but if you're just looking at cycle life, with comparable batteries comparing flooded lead acid to AGM, flooded will deliver more power through cycle life by about 12 percent than the AGM will.



Comparable rated AGM and Flooded, the AGM will be the lighter battery.


The 50% discharge thing is a crude value given for lead acid batteries. They degrade from temperature, time, use etc. What works best for regarding cycle depth is very situation dependent.


As far as Lithium batteries, LiFePO's are quite stable fire wise, and additionally are pretty good when it comes to not releasing toxic gasses like many lithium batteries can when they do overheat. Unfortunately, you can't expect anything resembling the life expectancy you seem to expect.


It will be interesting to see how you resolve the potential EMP vulnerability in the rest of your setup.
__________________
2016 Bighorn 3270RS, 2015 Ram 3500 CTD/ASIN
Searching_Ut is offline   Reply With Quote
Old 10-22-2019, 08:08 PM   #6
Senior Member


 
Join Date: May 2016
Location: Indiana
Posts: 444
After working in the battery industry for the better part of 30 yrs.

I have a few things to add:

AGM stands for Absorbent Glass Matt (think of it as fiberglass insulation batting that is inserted between the plates).

As already mentioned, AGM will not last a seriously longer amount of time or cycles over flooded as long as the flooded batteries are properly maintained.

I have never had to maintain flooded batteries weekly, but I guess if you boondock and daily cycle the batteries you might have to keep an eye on levels weekly until you figure out water usage. There is significant amount of "headroom" in a standard "golf cart" flooded battery so levels can usually drop as much as an inch before the top of the plates are exposed and real damage is done. Yes, boiling off water changes the specific gravity of the electrolyte, but long term life damage isn't done until the plates get exposed.

AGM's can out gas as well. They have a pressure relief valve that will open and release the pressure if charge levels are too fast or too high of a voltage. For that reason, make sure you change your charge profile for your new AGMs to match as closely as possible to what the manufacturer suggests.

With all the extra free electrolyte, flooded batteries are much better at expelling heat than a similarly sized AGM. It is easy for the inner cell(s) of an AGM to be 10 or more degrees hotter than the end cells. heat means outgasing, so charging rates and final voltage levels are much more important to AGMs than flooded.

Don't run an equalize cycle on your AGMs. Again, the high voltage and long period of an equalize cycle will probably cause the relief valve to open and once you lose that water you can't ever get it back inside. In an application like RV I would say AGMs probably die of drying out rather than the other causes of death of a flooded battery.

For the same reason, I'm not a big fan of AGMs as cranking/starter batteries. Yes they can make great CCA numbers due to lower resistance and other changes. But, if you want to use an AGM as a cranking battery, verify that it has been designed to handle the hours of ~14 volts that it will get from the alternator without outgassing. Most AGMs don't like alternator voltage levels over long periods of time. That is why RV manufacturers that have AGMs as house batteries add timing circuits to prevent the AGMs from being charged via the alternator for hours on end. Mine will only charge for an hour or so regardless of discharged state via the alternator before going into a long pause state to cool.

The one place AGMs are much better is handling vibration. The plate/glass mat sandwich is basically pressed into case, so there is significantly less room for the plates to move around. Plus the glass mat absorbs some of the vibration shock.

That said, the worse thing you can do to any lead acid battery is drive it down the road discharged. When the battery is discharged most of the acid is in the plates softening them. Vibration will cause bits of plate material to fall off and find it's way to the bottom of the cell. Not only does every piece of material lost reduce you capacity level, but eventually it will build up in the bottom of the cell leading to a shorted cell.

Bottom line, I would say just in the last 5-8 yrs would I recommend AGMs as RV house batteries. It took that long for the manufacturers to figure them out for deep cycle applications.

Steve


__________________
Steve & Tracy
2017 Entegra Aspire DEQ
photraveller is offline   Reply With Quote
Old 10-22-2019, 08:35 PM   #7
Senior Member
 
Join Date: Jul 2018
Posts: 1,435
Quote:
Originally Posted by Searching_Ut View Post
Interesting. EMP testing/certification has been a significant part of what I did for work over the last 40 years or so, but never once has it been a consideration on any of the choices I've made with my personal RV's. Should I worry about the BMS in a lithium battery as part of my solar power system that has a solar controller? The folks I would need to talk to to get my 5er tested are just down the road, but somehow, I can't imagine talking them into testing it, and really wouldn't want to suffer the costs of the test, or subsequent repairs.



Couple side notes:


There are many factors affecting battery life, but if you're just looking at cycle life, with comparable batteries comparing flooded lead acid to AGM, flooded will deliver more power through cycle life by about 12 percent than the AGM will.



Comparable rated AGM and Flooded, the AGM will be the lighter battery.


The 50% discharge thing is a crude value given for lead acid batteries. They degrade from temperature, time, use etc. What works best for regarding cycle depth is very situation dependent.


As far as Lithium batteries, LiFePO's are quite stable fire wise, and additionally are pretty good when it comes to not releasing toxic gasses like many lithium batteries can when they do overheat. Unfortunately, you can't expect anything resembling the life expectancy you seem to expect.


It will be interesting to see how you resolve the potential EMP vulnerability in the rest of your setup.
Curious about your knowledge on the life expectancy of Lifepo batteries. Can you point to any studies that indicate how long they should last?
__________________
Foretravel tag axle 40 ft. 500 hp/1550 ft/lbs ism 1455 watts on the roof. 600 a/h's lithium down below.
jcussen is online now   Reply With Quote
Old 10-22-2019, 08:48 PM   #8
Senior Member
 
Join Date: May 2017
Posts: 537
Quote:
Originally Posted by murphylawe View Post
AGM or Acid Glass Mat batteries ...
Picking a nit ... Absorbed Glass Mat

Quote:
Originally Posted by murphylawe View Post
... so these batteries are sealed and do not 'Out Gas' like wet cell batteries,...
Not truly "sealed" they can vent (without damaging the case) if the internal pressure gets too high. True, they typically do NOT release any gases.

There is something called a Sealed Lead Acid SLA battery and used to be used in emergency exit lights. They are sealed, until they split and leak !

Quote:
Originally Posted by murphylawe View Post
Like the wet-cell battery the depth of discharge is ~40-50%, ...
Not all flooded (wet) lead acid or AGM will achieve their maximum number of charge/discharge cycles if repeated taken down to 50% state of charge (SOC). Only TRUE "deep discharge" (NOT dual purpose marine/RV) batteries can take this. Standard (almost all 12V lead acid batteries) will achieve their maximum number of cycles if only taken down to no lower than 80% SOC.

Quote:
Originally Posted by murphylawe View Post
They are also even heavier than wet-cell batteries and cost twice as much.
From the Trojan spec sheets : T105 flooded, 62 lbs ; T105 AGM, 68 lbs. I don't know specifically about cost, but AGM do cost a lot more.

Quote:
Originally Posted by murphylawe View Post
... they (AGM) will operate for much longer than wet-cell, thousands of charge cycles.
I have never been able to find data backed by a manufacturer that states that AGM are capable of significantly larger number of charge/discharge cycle as compared to flooded cells.

Quote:
Originally Posted by murphylawe View Post
Urrrkkk! Not so fast, LiFePO4 batteries are insanely expensive:
  • Wet-Cell 12V/100AH Battery = $110
  • AGM 12V/100AH Battery = $199
  • LiFePO4 12V/100AH Battery =$799
Yes, they are, but you are leaving out the flooded 6V golf cart batteries. TWO GC2 batteries will give you about 220Ah and cost about $200.

Quote:
Originally Posted by murphylawe View Post
Additionally they require 'SMART' monitors to keep them from freezing, overheating, or overcharging. LiFePO4 batteries operate safely as long as nothing goes wrong... simply overcharging one turns it into a bomb.
Sorry incorrect ! LiFePO4 batteries can withstand over charging/discharging without fire/explosion. It is the Lithium-cobalt batteries (sometime called LiCo or LiPo) that have this issue. This is what you find in all portable electronics because they have higher power density than LiFePO4.

Quote:
Originally Posted by murphylawe View Post
I believe the BMS (circuit board) that monitors the health of the LiFePO4 batteries is subject to EMP which is an Achilles Heel.
Everything electronic has the same problem. I am all for "being prepared" but you can't protect against EVERYTHING and I put EMP in that class.
__________________
Retired. 31 year of automotive engineering for one of the Detroit 3, specializing in Powertrain Control Systems.
theoldwizard is offline   Reply With Quote
Old 10-22-2019, 08:56 PM   #9
Senior Member
 
Join Date: May 2017
Posts: 537
Quote:
Originally Posted by jcussen View Post
Curious about your knowledge on the life expectancy of Lifepo batteries. Can you point to any studies that indicate how long they should last?
According to Battle Born (one of the largest manufacturers of LiFePO4 batteries) :

Quote:
3000- 5000 Cycles*
.
.
.
*Approximately 75-80% of the battery capacity will remain after 3000 cycles in applications recharging at 0.5C or lower

We have seen life spans well over 5000 cycles in our lab testing.
So for maximum life, do not discharge past 50% SOC (0.5C), same as a deep discharge lead acid.
__________________
Retired. 31 year of automotive engineering for one of the Detroit 3, specializing in Powertrain Control Systems.
theoldwizard is offline   Reply With Quote
Old 10-22-2019, 09:06 PM   #10
Senior Member
 
Join Date: May 2017
Posts: 537
Quote:
Originally Posted by photraveller View Post
... if you want to use an AGM as a cranking battery, verify that it has been designed to handle the hours of ~14 volts that it will get from the alternator without outgassing. Most AGMs don't like alternator voltage levels over long periods of time.
Since the late 1990s/early 2000s all car, pickup and medium duty truck manufacturers have been using "smart charging" systems. None are exactly the same, but they have the same goal, charge the starting battery "just enough" to restore the energy used to start the engine.

Bottom line is, within 5 to 10 minutes of starting a vehicle, the alternator output voltage will be between 13.2V and 13.8V. You might see it go up when a larger electrical load is place on the system, but it will try to return to that "happy place".
__________________
Retired. 31 year of automotive engineering for one of the Detroit 3, specializing in Powertrain Control Systems.
theoldwizard is offline   Reply With Quote
Old 10-22-2019, 09:34 PM   #11
Senior Member
 
Join Date: Jul 2018
Posts: 1,435
Quote:
Originally Posted by theoldwizard View Post
According to Battle Born (one of the largest manufacturers of LiFePO4 batteries) :



So for maximum life, do not discharge past 50% SOC (0.5C), same as a deep discharge lead acid.
https://batteryguys.com/pages/lifeli...e-instructions
Looks like 1000 cycles for 50% discharge on a Lifeline AGM deep cycle.
Probably why Lifeline deep cycle offers 1 year replacement and 5 year pro-rated, while Battleborn offer a 10 year warranty.

https://lifelinebatteries.com/mcm_re...ited-warranty/
https://battlebornbatteries.com/terms-conditions/

According to BB, that is 3000 cycles to 0% SOC.
Think this would not happen very often, but if you did it more than a couple of times on a LA battery, would be a problem.
https://battlebornbatteries.com/dept...cle-batteries/
__________________
Foretravel tag axle 40 ft. 500 hp/1550 ft/lbs ism 1455 watts on the roof. 600 a/h's lithium down below.
jcussen is online now   Reply With Quote
Old 10-22-2019, 09:43 PM   #12
Senior Member
 
Join Date: Jun 2018
Posts: 232
Recognizing that the state of charge is causing a chemical change in the flooded lead acid batteries... I wonder exactly how the battery is being damaged by being discharged below 50%, and whether it is staying at that low level for any significant length of time that is actually doing the damage?

Example situation: Running the bank of GC2 golf cart batteries down to 20% SoC between sundown and sun-up with a continuous 5 amp (60 watt) draw for a 12v fan and a 120v fridge. The 20% cut-off is reached around 6am, just as the sun is coming up and the solar starts generating power within 20-30 minutes of the battery bank reaching 20% and the batteries are charged continuously to full power, reaching 80% (end of bulk charging) in about 3 hours.

What is the result on battery life?

Scenario #2: Same overnight situation, but instead of the sun coming up, it is a rainy day and the batteries stay down until the people wake up at 9am (so ~3 hours) and start the generator. Same charging.

Scenario #3: Something is left on by accident in storage and the batteries are pulled to 20% before the inverter cuts off and dies... And the batteries sit like that for a couple weeks.

I've read all the same reports that just say that draining batteries down damages them, but HOW FAST they are drained and how long they stay down MUST have a factor in this somewhere.

My hypothesis is that scenario #3 is certain to cause the most damage, probably severely affecting the batteries in loss of capacity that can be detected immediately. They may not even accept a charge at all, and have voltage values of only millivolts per unit. I have "rescued" some sealed lead acid batteries for recycling that have sat for unknown amounts of time, and most flat refuse to accept a charge at all. There are the odd few that do however, and self-discharge right after the charger is removed. Obviously shorted plates.

I am less confident in saying the same for scenarios #1 and #2, because the batteries haven't sat at low power long enough for any major chemical degradation to happen....Right?
__________________
03 40' Monaco Diplomat: 1020 watts solar / Victron / Magnesine 2800. TRW steering, 23 cuft Frigidaire, dishwasher, W/D, Magneshade, lots of other mods!
geordi is offline   Reply With Quote
Old 10-22-2019, 10:03 PM   #13
Senior Member
 
Join Date: Jul 2018
Posts: 1,435
Quote:
Originally Posted by geordi View Post
Recognizing that the state of charge is causing a chemical change in the flooded lead acid batteries... I wonder exactly how the battery is being damaged by being discharged below 50%, and whether it is staying at that low level for any significant length of time that is actually doing the damage?

Example situation: Running the bank of GC2 golf cart batteries down to 20% SoC between sundown and sun-up with a continuous 5 amp (60 watt) draw for a 12v fan and a 120v fridge. The 20% cut-off is reached around 6am, just as the sun is coming up and the solar starts generating power within 20-30 minutes of the battery bank reaching 20% and the batteries are charged continuously to full power, reaching 80% (end of bulk charging) in about 3 hours.

What is the result on battery life?

Scenario #2: Same overnight situation, but instead of the sun coming up, it is a rainy day and the batteries stay down until the people wake up at 9am (so ~3 hours) and start the generator. Same charging.

Scenario #3: Something is left on by accident in storage and the batteries are pulled to 20% before the inverter cuts off and dies... And the batteries sit like that for a couple weeks.

I've read all the same reports that just say that draining batteries down damages them, but HOW FAST they are drained and how long they stay down MUST have a factor in this somewhere.

My hypothesis is that scenario #3 is certain to cause the most damage, probably severely affecting the batteries in loss of capacity that can be detected immediately. They may not even accept a charge at all, and have voltage values of only millivolts per unit. I have "rescued" some sealed lead acid batteries for recycling that have sat for unknown amounts of time, and most flat refuse to accept a charge at all. There are the odd few that do however, and self-discharge right after the charger is removed. Obviously shorted plates.

I am less confident in saying the same for scenarios #1 and #2, because the batteries haven't sat at low power long enough for any major chemical degradation to happen....Right?
Think you are right on #3, left my charger off on two 8d agms for 2 weeks, had a constant parasitic load of about 60 watts. Batteries were down to 1 volt, and I could not recover either one.
__________________
Foretravel tag axle 40 ft. 500 hp/1550 ft/lbs ism 1455 watts on the roof. 600 a/h's lithium down below.
jcussen is online now   Reply With Quote
Old 10-22-2019, 10:15 PM   #14
Senior Member
 
Join Date: Jan 2018
Posts: 781
Quote:
Originally Posted by murphylawe View Post
Hey Everyone,

I am working on a solar installation and ....

That is your first mistake.

Second mistake is not analyzing your electric usage to determine how to minimize what you need batteries for.

A simple example is making coffee over a wood fire or with propane and a French press.

Third and common mistake is the KISS principle. Keeping it simple is a skill that seems to have been lost when new engineers stopped using slide rules.

So my MH has four GC2. I can cook breakfast with a microwave. I need to run the generator one hour a day. Add water to batteries every three months.
__________________

__________________
Kit & Rita
37 foot Ď98 HolidayRambler Endeavor diesel pusher
followingsea is offline   Reply With Quote
Reply

Tags
battery



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Choices choices help? X-RayNomad67 Class A Motorhome Discussions 14 08-19-2019 12:44 AM
Choices choices ArkansasRomr Class A Motorhome Discussions 97 08-15-2019 08:59 AM
Short bed camper on a long bed and a short bed Petes Dad Truck Camper Discussion 2 11-02-2018 06:53 PM
choices and more choices Campingkris Class A Motorhome Discussions 10 07-12-2013 10:11 AM
Rear Air Spring Replacement - Choices, choices, choices vtwinwilly Spartan Motorhome Chassis Forum 3 08-14-2011 08:52 AM

» Featured Campgrounds

Reviews provided by


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 03:36 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
×