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Old 04-22-2024, 09:41 AM   #1
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AGM compatibility with 2022 charging system

I have a 2022 forester, MBS 2401 and am thinking of changing out the lead acid batteries with AGM. The refrigerator drains the lead acid batteries in less than 8 hours. Batteries are a year old. Is the internal charging system compatible with AGM ( RENOLOGY) batteries. Lots of disclaimers on the web about needing a special charging system for AGM, however I think the disclaimers are for older model charging systems.
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Old 04-22-2024, 09:47 AM   #2
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AGM batteries are lead acid and will/should drain just as fast as your current flooded batteries. I know AGM is suppose to have higher charging voltages but I don't know if the stock convertor does or cares.

I'm not a lithium pusher but if you are going to spend the money on AGM lithium will be similar in price and give you more run time. Then of course you need to see if your convertor does lithium or if you have a solar panel to top them off.

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Old 04-22-2024, 09:57 AM   #3
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AGMs are lead acid, just in a different form.

Their performance is slightly better and are more or less, maintenance free but are also more expensive and heavier than the same footprint of vented LA.

IMO, at the current pricing and capabilities, now, even short term cost benefit, favors LiFePO4, by a long way.

But that wasn't your question. I know of no general compatibility issues for charges for LA vs AGM but could very well be mistaken on a case by case basis.
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Old 04-22-2024, 10:20 AM   #4
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To run the refrigerator, you are going to need more battery capacity.

FLA (Flooded Lead Acid) and AGM (Absorbed Glass Mat) are the same. Never discharge the FLA or AGM battery to less than 11.9 volts. Serious and permanent damage will occur to the battery.

The amp/hour capacity is the key. FLA and AGM batteries can be discharged to 50% of the amp/hour rating without damage. Thus a 100 A/H rated battery is capable of only 50 A/H useable.

You need a higher total amp/hour rating to power the refrigerator for more than 8 hours. Maybe two larger batteries.

I prefer AGM as they are maintenance-free, whereas with FLA one needs to check the electrolyte level on a regular basis.

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Old 04-22-2024, 10:22 AM   #5
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Lifepo4 200ah and a couple of solar panels

keeps the ice cream HARD and the beer chilled
can get 60 hours of fridge running

10 days in Ohio last week camping
turned on the battery charger (converter) once.

with decent solar you can also eliminate alternator charging (or modify the alternator charging to DC-DC or LI-BIM)
your results will vary depending on how much room on roof you have

BUT just getting the battery upgrade is worth it as long as you don't try and use inverter etc you can go a weekend / overnight camping on a 200ah lifepo4

they are also safe... won't catch fire like car batteries!
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Old 04-22-2024, 12:43 PM   #6
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Is the original inverter compatible with LiFePo4 batteries, if not what's the costs or change out effort ?
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Old 04-22-2024, 01:19 PM   #7
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Quote:
Originally Posted by ErnieSeabee View Post
Is the original inverter compatible with LiFePo4 batteries, if not what's the costs or change out effort ?
You'll have to check the model of your converter. If it is a WFCO brand and is lithium compatible, it will have AD after it's numbers.

If you have solar, it won't matter as much whether it is or isn't lithium compatible, as the solar controller will very likely have a lithium mode and will adjust the charge accordingly.

Since it is a motor home, the bigger concern is protecting your alternator.

If you can't find model specific info on your own, a call to your dealer and battery supplier is in order.

Difficulty of change out, depends on skill level. It is not difficult but does require at least some handyman / mechanical type skills.
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Old 04-22-2024, 01:29 PM   #8
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No. Only partially correct.

Quote:
Originally Posted by DJ252 View Post
You'll have to check the model of your converter. If it is a WFCO brand and is lithium compatible, it will have AD after it's numbers.
This is misleading and only partially correct.

One of the WFCO series models has the suffix AD, which stands for Auto-Detect, since it can Automatically Detect whether the battery(s) connected are Lead-Acid or LiFePO4.

Another series ends in REP which is a Lithium Converter REPlacement kit.

Yet another series ends in LiS which stands for Lithium Ion with remote Switch.

Another one that ends in L2 supports LiFePO4 only, not Lead Acid.
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Old 04-22-2024, 01:32 PM   #9
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Originally Posted by Larry-NC View Post
This is misleading and only partially correct.

One of the WFCO series models has the suffix AD, which stands for Auto-Detect, since it can Automatically Detect whether the battery(s) connected are Lead-Acid or LiFePO4.

Another series ends in REP which is a Lithium Converter REPlacement kit.

Yet another series ends in LiS which stands for Lithium Ion with remote Switch.

Another one that ends in L2 supports LiFePO4 only, not Lead Acid.
Glad to learn it.

Thank you.
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Old 04-22-2024, 02:03 PM   #10
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you could use your original charger to do a quickish charge... for the BULK of the work
a standard 13.6v converter will eventually charge the lifepo4 ... it's just a lot slower
if you are on shorepower, it is usually for all night.......
so the converter has enough time to fully charge a lifepo4


or you can add one of the below (in MY order of preference)
1) add some solar
2) OR a small 10amp lifepo capable charger top it off
3) OR you can buy a DC-DC to top it off as you drive ++
4) OR last choice would be to swap out the converter

++ a good DC-DC charger that will do lifepo4 at 14.2 to 14.4v will work better than modifying the a BIM style system (if you have one)
check the output of your alternator before buying a dc-dc as it may already be heavy duty atlternator that can withstand the extra stresses a lifepo4 can impose. If your alternator charges at over 14v it will work on lifepo4 for FASTER charging
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Old 04-22-2024, 03:29 PM   #11
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Quote:
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3) OR you can buy a DC-DC to top it off as you drive ++
In your motorhome, the alternator automatically charges your house battery as you drive.
Unless you have a smart alternator (not sure how you determine that), you're going to need a dc-dc converter to protect the alternator from overheating while charging the LiPo battery.

As to the AGM battery, you're not going to accomplish what you want with the AGM battery.
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Old 04-23-2024, 11:04 AM   #12
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I have the same exact issue as ErnieSeabee and making the same considerations and this is all good info but because I really don't understand all this stuff, I need clarification on Reverse Snowbirds comment about "you're going to need a dc-dc converter to protect the alternator from overheating while charging the LiPo battery"
How do I do that? Do I need a mechanic or an electrician to do that? (RV type is listed in my signature).
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Old 04-23-2024, 03:50 PM   #13
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Disconnect the BIM and your depleted lifepo4 battery will remain separate from the alternator /charging system....
a depleted lifepo4 can draw a lot of AMPS from your alternator.


If you want to use alternator for charging lifepo4 as you drive

check what alternator you have ... heavy duty ones often can be used
especially if you don't do a lot of stop, start, idling in traffic


light/medium duty alternators use a DC_DC charger to limit the amps being drawn from the alternator

OR get a Li_BIM
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Old 04-23-2024, 06:25 PM   #14
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How do I do that? Do I need a mechanic or an electrician to do that? (RV type is listed in my signature).
Any rv repair shop should be able to do the installation for you.
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Old 04-23-2024, 07:30 PM   #15
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I installed 2 LiPo4 460AH batteries as well as a 100 Amp DC to DC charger in my XL 37RB



Before doing so, I did a lot of research and will admit I found it a bit daunting. That said, I have an inner motto: "there is nothing I can't do". I am not a fan of tattoos but will admit to thinking about having that stamped on my arm. However, my SO asked me if I could fly a plane so I decided against the tattoo. I digress.


Anyway, I worked my way through it with the help of posts on this forum and research elsewhere.



I spent considerable money and time on this upgrade and the final result has been excellent. Most people have limited resources and I am no exception. What helped me decide if the investment in time and $ was worth it was the need to ask ourselves how long we might own the unit we have now or if we might be in the market for something different.



Although I am tempted to drive a Prevost just to investigate the option, in the final analysis ( because maintaining the Freightliner chassis and the Dynamax coach falls into my motto and the Prevost may be equivalent to flying the plane) we decided that our unit (which is the first RV we've owned and will most likely be the last) was a keeper and the investment was worth it.


So ask yourself how long you think you will keep the unit you have and decide if the expense is worth it especially when amortized over the period of ownership.



I think that with the help of the contributors on this forum and the OP's sharing of specific facts regarding the challenge at hand, he will find that upgrading the LiPo4 batteries could be the single best upgrade one could make.


FWIW, IMO, it would be folly to buy anything but LiPo4 batteries at this point. To the OP, take pictures, share details and you will successfully accomplish the task and be happy you did so.
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Old 04-23-2024, 10:13 PM   #16
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Quote:
Originally Posted by Bob K4TAX View Post
The amp/hour capacity is the key. FLA and AGM batteries can be discharged to 50% of the amp/hour rating without damage. Thus a 100 A/H rated battery is capable of only 50 A/H useable.
Bob
This is wrong. Seems to be a wive's tale that gets parroted a lot. FLA are fine to 80% Depth of Discharge (DOD). No damage will occur.

Best bang for the buck in FLA is probably 2x225Ah Golf Cart batteries in parallel.

50% DOD, 1150 cycles, 129,375 total Ah for the life of the battery
80% DOD, 675 cycles, 121,500 total Ah for the life of the battery

Compare that to a 100Ah LiFePO4

90% DOD, 3000 cycles, 333,333 total Ah for the life of the battery

The bigger deal is how fast you can get Ah back into the battery. Between my inverter/charger (70A), solar (100A) and DC-DC (18A), I can pump 188A into my batteries. That would boil those FLA batteries. C/5 is max for FLA charging. C/2 is recommended as a starting point for LiFePO4. Most can handle 1C. So you can recharge LiFePO4 a LOT faster than FLA.
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Old 04-24-2024, 09:14 AM   #17
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This is wrong. Seems to be a wive's tale that gets parroted a lot. FLA are fine to 80% Depth of Discharge (DOD). No damage will occur.

Best bang for the buck in FLA is probably 2x225Ah Golf Cart batteries in parallel.

50% DOD, 1150 cycles, 129,375 total Ah for the life of the battery
80% DOD, 675 cycles, 121,500 total Ah for the life of the battery

Compare that to a 100Ah LiFePO4

90% DOD, 3000 cycles, 333,333 total Ah for the life of the battery

The bigger deal is how fast you can get Ah back into the battery. Between my inverter/charger (70A), solar (100A) and DC-DC (18A), I can pump 188A into my batteries. That would boil those FLA batteries. C/5 is max for FLA charging. C/2 is recommended as a starting point for LiFePO4. Most can handle 1C. So you can recharge LiFePO4 a LOT faster than FLA.
Curious, you just said no damage will occur, yet then go on to show drastic decline in performance in cycle count. As the dod increases, so does sulfation of the plates, and not only does cycle count go down, but available output does also. It’s not as if it is binary, the performance decreases in a linear fashion as it ages.

I respectfully disagree that FLA is the best bang for the buck. Plenty of lithium choices now (some with integrated shunts and bluetooth that preclude the need for a different battery monitor) for close to the same cash. Spending money of FLA is, imho, very false economy. Maybe if you wanted something to get you through a season and then quit using an rv altogether FLA makes sense, but that’s about it.
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Old 04-24-2024, 09:45 AM   #18
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Curious, you just said no damage will occur, yet then go on to show drastic decline in performance in cycle count. As the dod increases, so does sulfation of the plates, and not only does cycle count go down, but available output does also. It’s not as if it is binary, the performance decreases in a linear fashion as it ages.

I respectfully disagree that FLA is the best bang for the buck. Plenty of lithium choices now (some with integrated shunts and bluetooth that preclude the need for a different battery monitor) for close to the same cash. Spending money of FLA is, imho, very false economy. Maybe if you wanted something to get you through a season and then quit using an rv altogether FLA makes sense, but that’s about it.
FLA will not be damaged by going to 80% DOD. Reduced cycle count and damage are not the same thing. Total Ah out are about the same. To say it does damage is wrong. Deep cycle batteries are meant to be, well, deep cycled.

And FLA is the worst bang for your buck. A 100Ah LiFePO4 will easily provide 333,333 Ah over a 3000 cycle life. You would need more than two sets of FLA golf cart batteries and still won't get that much energy. Nothing about FLA makes sense in the RV energy storage and production world.
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Old 04-24-2024, 11:09 AM   #19
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https://www.batteryzone.co.nz/the-zo...m%20of%2080%25.

“BATTERY TIP 4 - Never fully discharge a deep cycle lead acid battery!
The deeper you discharge the battery the more it will reduce the battery’s total cycle life. We recommend discharging a battery to no lower than 50% DOD, with a maximum of 80%. If you discharge the battery to 50% of its capacity instead of 100%, the battery will produce an extra 40% more amperes over the life of the battery.”
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Old 04-24-2024, 11:21 AM   #20
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Originally Posted by Half Ton Heavy View Post
https://www.batteryzone.co.nz/the-zo...m%20of%2080%25.

“BATTERY TIP 4 - Never fully discharge a deep cycle lead acid battery!
The deeper you discharge the battery the more it will reduce the battery’s total cycle life. We recommend discharging a battery to no lower than 50% DOD, with a maximum of 80%. If you discharge the battery to 50% of its capacity instead of 100%, the battery will produce an extra 40% more amperes over the life of the battery.”
Huge difference between 80% and 100% DOD on a deep cycle battery.
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