AGM or LiFePo4?

[Anhedonic]

I have been planning my electrical system (as some of you may have seen in other posts.) I was set on a small AGM setup with some solar and a connection to both starter batter and shore power with a generator to do the AC and wheelchair charging related heavy lifting. 

My family has been helping me to get things going and I have been told that, if it really is better, that I would be given the money for a LiFePo4 battery. This of course blows all the research I've done and brings chaos to my planning.

So, should I go with lithium or stick with AGM given the choice? If lithium, what changes will I need to make to my setup to make it work and not kill the roughly cube-shaped killobuck I might end up with in my van? Any recommendations for good batteries? I'm hoping for either a 200 or 300ah battery as it may be the only battery I end up using in the build and I have no clue when I'll be able to afford another. 

Thoughts?

 

[Anhedonic]

One example of things I wouldn't have needed but now probably do is a battery level monitor to keep track of amps in and amps out because the voltage in LFP stays steadier.

If you had these options, what would you do and how would you do it?

 

[Moxadox]

I'll be interested to hear what others have to say. I'm in the process of building my solar system now. What I've learned so far: if you have the resources, definitely maximize your system. Talk with experienced others about your needs, both today and in the future. What do you want to be able to run? What do you **need** to be able to run? Where will you be travelling and what conditions will you encounter? Remember that lithium batteries cannot be charged at or below freezing temperatures. That said, LiFePO4 batteries can be located inside your rig because they do not off-gas. They are also considerably lighter! And, of course...very expensive.

Looking forward to reading the rest of the thread, and seeing what you decide.

The Dire Wolfess

 

[picopat]

Hi Anhedonic,

When I designed my system a year and a half ago I had my heart set on using lithium batteries but ended up going with AGM after I did the cost analysis.

Assuming you're up for the added complexity of safely implementing a lithium system, which I was, it comes down to cost.

Pros:
Lithium is lighter and therefore cheaper to haul around (better fuel efficiency)
Longer period of time before you have to replace them

Con:
Way more expensive. Be sure to count the battery manager and cell balancer's cost when you add it all up.

For my system and expected driving I figured it would take 5 years of fuel efficiency savings to break even on the cost of lithium. I'm not sure what I'll be doing 5 years from now so it didn't make sense for me. If you read Technomadia's article though it did make sense for them.

Hope that helps!

Patrick

Sent from my Nexus 6P using Tapatalk

 

[Anhedonic]

I've already been through figuring out sizing. The big stuff won't run on batteries at all, so the battery bank in my build will be running small stuff. CPAP, vent fans, charging for phones and other such things, etc. Eventually, when I can afford it, probably a fridge as well. Ideally, when I was planning for AGM, I was ultimately going for 600-800ah so that I could do things like power a large screen. Occasionally running a small microwave might be nice too. I think a 300ah LFP would do that just as well because it can be discharged more deeply.

I'm figuring on keeping the batteries inside and keeping them warm. When parked and on shore power, I am going to keep the temperature inside stable using an electric heater.

 

[Anhedonic]

Hi Anhedonic,

When I designed my system a year and a half ago  I had my heart set on using lithium batteries but ended up going with AGM after I did the cost analysis.

Assuming you're up for the added complexity of safely implementing a lithium system, which I was, it comes down to cost.

Pros:
Lithium is lighter and therefore cheaper to haul around (better fuel efficiency)
Longer period of time before you have to replace them

The fact that they can be discharged most of the way instead of halfway is the big draw for me for lithium. The cost made me dismiss them as a possibility until just a couple of days ago. Now I have to re-think everything. The added complexity you mention is the one thing that really gives me pause; everything I've been reading is for AGM and SLA.  Will I need a cell balancer with only one battery, are we talking about internal cells? Also, some sites seem to think balancing Li cells can lead to problems with overcharging? 

The other thought is just to do what you did and go with a bigger AGM bank along with solar, all for the same cost as the one LFP battery. I mean for the same $2,000, I could put in 600ah of AGM and a couple of hundred watts of solar on the roof...

 

[QinReno]

....
That said, LiFePO4 batteries can be located inside your rig because they do not off-gas.

I imagine there are multiple opinions on this, and some very strong opinions, no doubt. FWIW, see what these guys say about AGM outgassing. Enter " vent" in the search window.
https://batteryuniversity.com/learn/article/absorbent_glass_mat_agm

"[font=Arial, Helvetica, sans-serif]yes, AGM and Gel batteries are safe for use in enclosed spaces.[/font]
[font=Arial, Helvetica, sans-serif]only in serious overcharging situations do they vent some gas".[/font]

- re under the bed.
[font=Arial, Helvetica, sans-serif]"Yes Michael, AGM will be perfectly safe for you.[/font]
[font=Arial, Helvetica, sans-serif]both Gel and Agm vent a tiny bit when being charged hard, but it’s not enough to be considered even remotely dangerous or a risk".[/font]

 

[lenny flank]

The pros of lithium:

They can be discharged more deeply than AGMs.

They can be stored at partial charge.

They're lighter in weight.

The cons:

They cost an effing fortune (not a problem if someone else is paying though).

They do not like very hot or very cold conditions.

They require special electronics to run them.

 

[QinReno]

.........
Also, some sites seem to think balancing Li cells can lead to problems with overcharging? 

I don't know the specifics of Li batteries for RVs, but ....

I have it exactly the "other way around". I have model RC cars, and the battery chargers for Li all use balanced charging **ONLY**. There is a special connector on the RC Li batteries that allows measuring every single cell separately for proper balancing. Plus they also recommend always putting your Li battery inside a fireproof pouch when charging. There are of course a bazillion RC cars that use Li and only so many RVs at this point, so I'm with the RC world on this. 

You pays your money and you takes your choice. FWIW, I would not have a Li battery in my van. My van is too precious. And a battery is just a damn battery.

 

[QinReno]

The cons:

 They are known to catch fire, in certain cases.
- https://www.google.com/search?q=lithium+battery+on+fire

 

[Anhedonic]

 They are known to catch fire, in certain cases.
- https://www.google.com/search?q=lithium+battery+on+fire

That's why I plan to use only Lithium Iron Phosphate batteries. That chemistry is considerably less prone to exploding than other lithium batteries; thermal runaway isn't a problem for these like it is for those used in RC cars (and actual electric cars for that matter.)

 

[picopat]

Will I need a cell balancer with only one battery, are we talking about internal cells? Also, some sites seem to think balancing Li cells can lead to problems with overcharging? 

Cells and batteries are not the same thing but the terms are commonly interchanged (I'm guilty). LiFePO4 cells are 3.2V and you use 4 in series to get 12.8V. Building it from scratch like this is the cheapest way to implement but you need to know what you're doing.

Sounds like you may be talking about a drop in replacement type LiFePO4 battery. These have cell balancers and battery management systems built in so you can treat it like any lead acid battery.

Patrick

Sent from my Nexus 6P using Tapatalk

 

[Anhedonic]

Cells and batteries are not the same thing but the terms are commonly interchanged (I'm guilty). LiFePO4 cells are 3.2V and you use 4 in series to get 12.8V. Building it from scratch like this is the cheapest way to implement but you need to know what you're doing.

Sounds like you may be talking about a drop in replacement type LiFePO4 battery. These have cell balancers and battery management systems built in so you can treat it like any lead acid battery.

Very good. I thought so. You had me concerned for a moment.

 

[RogerD]

Here is an interesting video I recently watched regarding AGM vs Lithium.

 

[QinReno]

That's why I plan to use only Lithium Iron Phosphate batteries. That chemistry is considerably less prone to exploding than other lithium batteries; thermal runaway isn't a problem for these like it is for those used in RC cars (and actual electric cars for that matter.)

I hope so, they better be for 4-5X the cost of AGM. Info on safety of LiFePO4:
- https://relionbattery.com/blog/3-essential-lifepo4-battery-features-that-promote-product-safety

I wonder if Elon will go to safer batteries.
- https://www.teslarati.com/inside-tesla-model-3-2170-lithium-ion-battery/

 

[John61CT]

 They are known to catch fire, in certain cases.
- https://www.google.com/search?q=lithium+battery+on+fire

Total crock, very misleading.

LFP is one of dozens of "lithium" chemistries, all vary wildly in all their characteristics, just a catch-all umbrella term.

And LFP does not suffer from the thermal runaway problems many of the others do.

To the point it is the only non-lead chemistry suitable for House bank use in a mobile context.

Please stop such ignorant scare-mongering.

I wonder if Elon will go to safer batteries.
- https://www.teslarati.com/inside-tesla-model-3-2170-lithium-ion-battery/

Tesla does not use LFP.

 

[QinReno]

Please stop such ignorant scare-mongering.

As I said ---> you pays your money and you takes you choice. 

Buy what you want, but check out the all the issues. I would do a LOT of research before switching.

 

[max+sophia]

Would this be a good battery to use in my SUV to set up for house-type plugins?
https://www.amazon.com/EarthX-ETX12...d=1538508806&sr=8-10&keywords=LiFePo4+battery

or would this SYSTEM be better
https://www.amazon.com/dp/B07216H7X8/ref=sspa_dk_detail_4?psc=1

 

[John61CT]

Yes drop-ins are "easier" in some ways, and treated properly may last a long time.

But they are very limited performance compared to a proper system built on 4S prismatic cells, which for sure will last **much** longer if cared for properly.

5x the cost is a very low estimate, and it is possible to kill them dead pretty easily.

Compare to Deka, quality deep cycle FLA at $1 per AH. Much better value, can last 8+ years cared for properly.

Double the weight though.

My perception of the OP tech knowledge, recommend sticking to lead, but might mean getting a bigger / stronger vehicle.

A really good LFP bank that big will cost many thousands.

 

[Anhedonic]

I hope so, they better be for 4-5X the cost of AGM. Info on safety of LiFePO4:
- https://relionbattery.com/blog/3-essential-lifepo4-battery-features-that-promote-product-safety

I wonder if Elon will go to safer batteries.
- https://www.teslarati.com/inside-tesla-model-3-2170-lithium-ion-battery/

From that first link, third paragraph: "LiFePO4 technology is widely regarded as one of the safest ways to power a battery-operated application"

So I'm feeling pretty safe with that choice. :

I looked at getting a Tesla battery and using it a while back, but the cooling and charge balancing are pretty close to rocket science and I didn't feel up to the task of using one safely, putting aside the enormous costs involved.