Lithium or AGM?

[suncoastdancers]

It's coming up to the time I have to replace my stock 6V lead acid batteries. The lithium option looks appealing however it would require a wholesale change-out of my power converter and my solar array controller, plus a significant amount of rewiring. AGM looks like a straightforward, maintenance-free alternative. Has anyone run on 6V AGM deep cycle batteries and what has been your experience with them?

 

[splitting_lanes]

I don’t see why Lithium would be a problem, you can run lithium on an AGM charging profile. I have my solar charge profile set to AGM for my lithium battery.

AGM’s are cheaper though, and might fair through really cold weather better.

 

[suncoastdancers]

I don’t see why Lithium would be a problem, you can run lithium on an AGM charging profile. I have my solar charge profile set to AGM for my lithium battery.

AGM’s are cheaper though, and might fair through really cold weather better.

Thanks for your reply. Have you had any issues with the stock DC power converter charging the lithium battery?

 

[NEWYORKHILLBILLY]

Being you Have 17 model I would stick with same as you have or AGM. I would not want the lithium batteries outside. Plus Do you want $2500 of sitting on back bumper. You can replace what you have for under 300 bucks. Have you found the maintenance you been doing too much of a hassle? I would think in a 17 model there pretty easy to check. Of course, with the AGM you can remove that maintenance. Because lithium cost more a lot of people think it's better. There are situations when it may be A better install. You have the advantage of having experience with the wet sells. The AGM would give you the same experience without the maintenance. Only you can decide if that's right for you.

 

[vermilye]

I'd go with AGM unless you use an inverter heavily & spend most of your time dry camping. If you do go for lithium, I'd move them inside both for cold weather & security.

A number of folks have replaced their stock batteries with AGMs with o problems. Helpful for those that have inside batteries with poor venting that set off the propane detector.

 

[rubicon327]

There is a tipping point where lithium makes sense but it’s not right for everyone. We took the plunge only because I added a 2000W inverter charger that can run mini-split A/C, microwave and all outlets and we wanted more useable amp-hours to prolong time between charging when off-grid. If you are just a low to moderate power user I would probably just stick with AGM. Much more economical choice. Lithium only really starts to make sense if you decide to increase your amp-hours because the energy density of lithium is incredible. Multiple pairs of lead acid batteries would just be too much weight and volume to accommodate in these smaller trailers. I have a true 400AH of energy in less space than two 6V lead acid in a battery box. Much lighter too. I had already moved them inside. As mentioned I would not want them outside permanently in a colder climate. The major limitation is that lithium cannot be charged below 32F/ 0C. I heard that Escape decided to move all batteries inside on all models which helps tremendously when choosing the lithium option. Not the best move though for standard lead-acid due to hydrogen off-gassing...they should be offering AGM’s inside in my opinion. They are still trying to figure out the 17 and I think they said it may remain an option to keep them on the bumper.

 

[splitting_lanes]

Thanks for your reply. Have you had any issues with the stock DC power converter charging the lithium battery?

Our DC converter auto senses for LA or Lithium. It used to ‘think’ it was LA because the wiring was so long. It worked ok with the LA profile, but it charges much faster with the lithium profile.

If you’re batteries are going to stay outside, and your trailer lives in an area that gets really cold ( below 20) for periods of time, like others have said, you might want to go AGM. I didn’t consider your battery location in my first reply.

 

[alanmalk]

...
Has anyone run on 6V AGM deep cycle batteries and what has been your experience with them?

I used AGMs - two 12V in parallel - for 7 years without any issues. When it came time to replace them (due to general old age) I went with Lithium's, also 2 12V in parallel. The big driver for me was the far lower weight. I was also attracted to the flat voltage discharge curve and better usable power (State Of Charge). On the other hand, I am not feeling wonderful about the new charging voltage requirements and the cold weather restrictions. The somewhat limited maximum amperage discharge is not an issue for me since my inverter is "tiny" at 400 watts.

There are quite a number of advantages for each type of battery. And a number of disadvantages, also. Your best bet is to do research and decide which type best fits your situation.

I know I am not providing hard, usable facts here, but a good education in various battery chemistries is your best friend when making this type of decision.

 

[John in Santa Cruz]

An old school lead acid converter, like an older Parallax or WFCO will be slower charging a lithium iron phosphate battery and it probably won't get the more than 85-90% charged. The PD4655L I replaced my WFCO with can recharge my 412AH LFP battery from 50% to full in about 7 hours. That's about a week of camping, compressor fridge, using the furnace at night, fan in the day, led lights, and briefly using a 2000W inverter to make coffee, wife's hair dryer, etc.

 

[daniel108]

Seems like it hasn't been mentioned yet - AGM or lead acid will be cheaper in the short term, but lithium will last much longer, like about 6x the number of charge/discharge cycles. We don't dry camp that often and when we do it's only for a couple days, so I'm doing fine with the lead acids my 21C came with, but when the time comes (probably another season), I'll likely replace with lithium just for the long term cost savings.

 

[suncoastdancers]

Seems like it hasn't been mentioned yet - AGM or lead acid will be cheaper in the short term, but lithium will last much longer, like about 6x the number of charge/discharge cycles. We don't dry camp that often and when we do it's only for a couple days, so I'm doing fine with the lead acids my 21C came with, but when the time comes (probably another season), I'll likely replace with lithium just for the long term cost savings.

Interesting. I found one LI manufacture that claims 2000 charge cycles (down to 80% DoD) before significant battery degradation. That works out to be a 360 KAh service life for a 225 Ah battery. I wonder how this compares to electric car experience?

For AGM, I found an interesting analysis on AGM DoD myths:

<https://tab-rv.vanillacommunity.com/discussion/9940/agm-battery-depth-of-discharge-myth-busted>.

The authors developed a “composite” AGM battery from data available from Harris, Trojan, Concorde, Odyssey and Rolls. According to their analysis, a 225 Ah AGM battery deep cycled to 50% DoD would have a service life of 72 KAh. 71 KAh if deep cycled to 80% DoD. The variable here of course is that you get fewer effective charging cycles at 80% DoD, but more of less the same service life.

Assuming this analogy holds, one would expect the LI battery would have 5 times the life expectancy of AGM. About what you noted. I typically replace my batteries every 6-7 years. If I go AGM, I will be approaching my 80's by next changeout! Who knows if I will still have the trailer?

 

[rubicon327]

Interesting. I found one LI manufacture that claims 2000 charge cycles (down to 80% DoD) before significant battery degradation. That works out to be a 360 KAh service life for a 225 Ah battery. I wonder how this compares to electric car experience?

My Bestgo 400AH LiFePo battery says charge cycles >or= to 3000 at 80% DOD, +/- C/3, 23 degC. After 3000 cycles can deliver >or= to 75% rated capacity. Since these are used for electric vehicles I can understand the torturous test. C/3 would be about 130A. For context this battery should be able to go through a rather large amperage discharge/charge cycle every day for over 8 years and then still provide 300AH of capacity. With relatively light use in the trailer compared to the daily torture of an electric vehicle the life with acceptable performance is hopefully 15 - 20 years (or more?). Lithium is still quite expensive. I didn't buy for lifecycle cost but it does look pretty good when you lay it out. You make a great point about how long you might have the trailer though. No use making large a large investment (batteries + other required upgrades) for the next owner unless you felt you would enjoy it for the remaining years and then could recoup it in the selling price.

 

[Nindy]

When it was time to replace my original 6V batteries I switched to AGM and have been perfectly happy with them. I'm not a big user of power when boondocking and mostly camp at my property with electricity. Lithium is tempting but I would lose the storage space inside for them. The AGMs more than power what I need and required no mental energy to buy and install.

 

[oldwave]

There is a tipping point where lithium makes sense but it’s not right for everyone. We took the plunge only because I added a 2000W inverter charger that can run mini-split A/C, microwave and all outlets and we wanted more useable amp-hours to prolong time between charging when off-grid. If you are just a low to moderate power user I would probably just stick with AGM. Much more economical choice. Lithium only really starts to make sense if you decide to increase your amp-hours because the energy density of lithium is incredible. Multiple pairs of lead acid batteries would just be too much weight and volume to accommodate in these smaller trailers. I have a true 400AH of energy in less space than two 6V lead acid in a battery box. Much lighter too. I had already moved them inside. As mentioned I would not want them outside permanently in a colder climate. The major limitation is that lithium cannot be charged below 32F/ 0C. I heard that Escape decided to move all batteries inside on all models which helps tremendously when choosing the lithium option. Not the best move though for standard lead-acid due to hydrogen off-gassing...they should be offering AGM’s inside in my opinion. They are still trying to figure out the 17 and I think they said it may remain an option to keep them on the bumper.

Agm’s can still off gas hydrogen under circumstances, they still should be vented.

 

[rubicon327]

Agm’s can still off gas hydrogen under circumstances, they still should be vented.

Thank you for the reminder. While it shouldn’t off gas under normal operation an AGM can vent if charged improperly. With the varying quality of battery chargers out there I could see a potential issue. From an article I found…”Charging too quickly produces hydrogen at a rate faster than it can be absorbed into the glass mat. If this occurs long enough, pressure will build inside the battery, and could force the valve to open. When this occurs, you’re suddenly releasing the accumulated hydrogen into the battery compartment. So you still need a location that’s free of ignition sources, and open to the atmosphere to dissipate the gas.”

 

[John in Santa Cruz]

a lot of AGMs I've seen don't have vent tube fittings. My wife's car has an AGM aux battery in the trunk, its essentially a 12V 17AH motorcycle battery, but it has a vent tube. 90% of the available replacement batteries don't have that vent tube.

 

[hugh]

a lot of AGMs I've seen don't have vent tube fittings. My wife's car has an AGM aux battery in the trunk, its essentially a 12V 17AH motorcycle battery, but it has a vent tube. 90% of the available replacement batteries don't have that vent tube.

Yeah, I think you'd be stuck having to put AGM's in a battery box, just like the flooded batteries. They've all got pressure relief valves, but if the valve doesn't have a tube attachment, there's not much you can do.

 

[Perry Butler]

It’s not like AGM’s are open like flooded and the gas is continuous. They “burp” a slight amount of gas, occasionally, and rarely, so by the time they burp again that gas has dissipated. Nothing to worry about. It’s kind of like all those explosions from running your fridge at the gas station that have never happened. The sky is not falling.

Enjoy,

Perry

 

[hugh]

It’s not like AGM’s are open like flooded and the gas is continuous. They “burp” a slight amount of gas, occasionally, and rarely, so by the time they burp again that gas has dissipated. Nothing to worry about. It’s kind of like all those explosions from running your fridge at the gas station that have never happened. The sky is not falling.

Enjoy,

Perry

Yep, nothing to worry about. That's why ABYC and others require AGM batteries to be installed in a vented box:


https://rvnerds.com/2017/11/01/electrical-myths-part-4-agm-batteries-dont-need-venting/

 

[John in Santa Cruz]

Yep, nothing to worry about. That's why ABYC and others require AGM batteries to be installed in a vented box:


https://rvnerds.com/2017/11/01/electrical-myths-part-4-agm-batteries-dont-need-venting/

yeah, and why cars like Mercedes come with AGM batteries that have vent tubes connected

to be fair, the larger car sized AGMs usualyl do have vent tubes, at least the H series euro batts. its the smaller motorcycle sized batteries that get sketchy