My AGM to Lithium conversion

[Rbertalotto]

Here is a quick article I wrote on my adventure going from AGM batteries to Lithium.

http://rvbprecision.com/rv-projects/rv-lead-acid-agm-to-lithium.html

http://rvbprecision.com/rv-projects/rv-lead-acid-agm-to-lithium.html

[BFL13]

Itinerant1 wrote:
StirCrazy brings up a fair point that the agm pack has to made larger to equal the lfp pack. I think but could be wrong that 800ah lead would be equal 500ah lfp, it's been along time ago researching this so I could be mistaken.

Over the past 6 years with my lfp and using it in whatever SOC with high draw items for long periods of time and not needing to get them back to full like a lead pack should be also be thought about when comparing "price". With lead how often is a rv park needed or home needed to full charge on occasion to get longest life. Or long generator time to get back to full. How often is the equalization charge needed for long life.

All good points for that scenario.

You could do your daily 200AH with 500 of AGMs ok but as noted need to keep getting them to full. Having more than 500 of AGMs would just make it harder to get to full

To meet the 20% charging rate spec means 100a charger and big enough gen for it

It depends on scenario for each RVer if any advantage with LFPs. No use for me where 4 sixes are just right

[3_tons]

Upon a re-read of what’s now this 10 pg thread, and reflecting upon many past, exhaustive LFP threads (e.g. indictments?…), one might now sense the subtile paradigm evolution that’s taken place over a time which typically goes from ‘idea rejection’ to ‘idea acceptance’ and which ultimately leads to ‘idea adoption’ 🙂 …This, the predictable signature of a paradigm shift (often seismic) - may the former recalcitrant narratives finally R.I.P…

3 tons

[pianotuna]

With sufficient solar, a part time rv'er using agm may start every trip with the battery bank at 100%.

If shore power is limited, as it will be on my next trip, the battery bank will be totally full by morning. My main use is doing load support as needed.

I have a dc to DC charger waiting to be installed. That may help with charging while trundling down the road. The way things are now--my house bank sends energy to the engine battery. I'd be better off not having the dual charging circuits active.

The best bang for the buck are "reconditioned" agm from places such as the local Interstate store. These are batteries used in cell phone towers. When one battery in a string goes bad--they are all replaced.

Cost 5 years ago was $1 per amp-hour.

No one attempts to get to 100% state of charge using a generator unless they have no other possible choice.

Itinerant1 has proved that he can run anything on his RV as though it were connected to shore power, including the air conditioner.

I just wish I could afford my beloved SiO2 jars. Revenue Canada is clawing back every penny of the assistance from CRB that I collected in good faith. $8460.10 would have purchased a rather nice battery bank.

[Itinerant1]

StirCrazy brings up a fair point that the agm pack has to made larger to equal the lfp pack. I think but could be wrong that 800ah lead would be equal 500ah lfp, it's been along time ago researching this so I could be mistaken.

Over the past 6 years with my lfp and using it in whatever SOC with high draw items for long periods of time and not needing to get them back to full like a lead pack should be also be thought about when comparing "price". With lead how often is a rv park needed or home needed to full charge on occasion to get longest life. Or long generator time to get back to full. How often is the equalization charge needed for long life.

[StirCrazy]

BFL13 wrote:

StirCrazy wrote:



considering a 80AH agm is over 450.00 bucks up here, and have been for over 4 yers now, I wouldnt say there was much of a cost risk. two of thoes in my camper would give me 160AH total for about 1K including taxes.. for 900 I did 300AH of LFP, droped from 130 to 49lbs, and was able to put it in the original battery space for the old camper freeing up my outside storage space which was taken up by the GC2's

Steve

Battery pricing varies but around here the 100AH AGM I got five years ago for $230 (Can) is now $330 and a T105 has gone up from about $155 to $255.

So 300AH of AGMs is now $990 before tax and core fee. Meanwhile a drop-in LFP price (not for sure typical as they vary) is about $1,500 for a 150AH so two would be $3,000

Somehow by rolling your own you got 300AH of LFP for $900 so that is quite a saving.

http://www.wegosolar.com/categories.php?category=Deep-Cycle-Batteries/CAN-BAT-Lithium

ya bare cells I got for 150 each plus shipping. happened to catch a sale. don't forget though, to get as much life as you can out of thoes AGM batteryies you need double the 300AH I got with the LFP cells and still won't get as much life. so that makes the AGM much more expensive, and even compared to the off the shelf ones, they are a lot closer in price. but there are several places in canada you can buy 100AH prebuilt ones for around 500 each now so that would be 1500 for 300AH capacity. the prebuilts are slowly coming down in price but I am worried whats going to happen now that electric cars are starting to switch to LFP. might get more expensive due to demand or may get cheeper due to increased production. only time will tell.

[BFL13]

StirCrazy wrote:



considering a 80AH agm is over 450.00 bucks up here, and have been for over 4 yers now, I wouldnt say there was much of a cost risk. two of thoes in my camper would give me 160AH total for about 1K including taxes.. for 900 I did 300AH of LFP, droped from 130 to 49lbs, and was able to put it in the original battery space for the old camper freeing up my outside storage space which was taken up by the GC2's

Steve

Battery pricing varies but around here the 100AH AGM I got five years ago for $230 (Can) is now $330 and a T105 has gone up from about $155 to $255.

So 300AH of AGMs is now $990 before tax and core fee. Meanwhile a drop-in LFP price (not for sure typical as they vary) is about $1,500 for a 150AH so two would be $3,000

Somehow by rolling your own you got 300AH of LFP for $900 so that is quite a saving.

http://www.wegosolar.com/categories.php?category=Deep-Cycle-Batteries/CAN-BAT-Lithium

[Itinerant1]

Weight can certainly be a factor. My 500ah weighs 143#, a quick search showed the average 100ah agm was 65# (some lighter, some heavier) total 325# +/-.

The entire system (batteries, panels, scc, inverter, wiring) on the trailer is 500#.

[StirCrazy]

BFL13 wrote:
I used to say itinerant1 could have done equally well with 500 AH of AGMs by swapping them out as required. Now it is not so clear.

The difference now is that he is taking advantage of the LFP high draw ability to run his air conditioner.

It may be that the AGM option would only do that at higher SOCs while the LFP will at lower SOCs

That and the shifting money side where replacement AGMs are going up in price is tilting the balance for his scenario IMO.

How it plays out for recent RV LFPers will not be known for several years yet whether their LFPs were worth it vs another five years or so with another set of FLAs.

considering a 80AH agm is over 450.00 bucks up here, and have been for over 4 yers now, I wouldnt say there was much of a cost risk. two of thoes in my camper would give me 160AH total for about 1K including taxes.. for 900 I did 300AH of LFP, droped from 130 to 49lbs, and was able to put it in the original battery space for the old camper freeing up my outside storage space which was taken up by the GC2's

Steve

[01tundra]

BFL13 wrote:
How it plays out for recent RV LFPers will not be known for several years yet whether their LFPs were worth it vs another five years or so with another set of FLAs.

Losing 90 lbs off the tongue, fast recharge rates, zero maintenance, warranty duration, performance....I can save several years and say without question that is was well worth it to me.

[BFL13]

I used to say itinerant1 could have done equally well with 500 AH of AGMs by swapping them out as required. Now it is not so clear.

The difference now is that he is taking advantage of the LFP high draw ability to run his air conditioner.

It may be that the AGM option would only do that at higher SOCs while the LFP will at lower SOCs

That and the shifting money side where replacement AGMs are going up in price is tilting the balance for his scenario IMO.

How it plays out for recent RV LFPers will not be known for several years yet whether their LFPs were worth it vs another five years or so with another set of FLAs.

[Itinerant1]

pianotuna wrote:
I meant daily consumption of electricity--in watt-hours or kwh's

The best I can do is the percent used (1% eqauls 5ah) recorded from when the SCC goes into sleep mode, that's the battery SOC% evening to when the SCC wakes up in bulk mode, battery SOC% morning. The only reason I keep track of that is it will give me a rough idea of what my 500ah lfp batteries did when it gives up the ghost.

I could back to 1/1/17 when I started keeping records of everyday production/ consumption of power and where we boondocked not that it helps anyone but gives me an idea. Plus when I'm posting information its factual from my records not from fading grey matter.

It really is amazing to see the punishment lfp can take on a daily basis. 😉

Edit: when I mention % that's capacity of my 500ah battery bank.

[BFL13]

pianotuna wrote:
I meant daily consumption of electricity--in watt-hours or kwh's

Not all that clear between daily AH and battery high and low with solar taking some load

Impressive that he foresaw how to set up back when less was known about LFPs. I like how he keeps track of it all. My kind of guy 🙂

No "fire and forget" there!

[pianotuna]

I meant daily consumption of electricity--in watt-hours or kwh's

[Itinerant1]

Or a period of time from Nov 2021.

[BFL13]

PT I think he means 40% of his 500 AH and Sig says about 35% DOD so he is operating between about 35-75 SOC

He can do that range for long battery life because he has the big battery bank as mentioned above.

I am curious if the 14.1Vabs is related to the 75% SOC at all.