Battery Agm Vs Lithium

Thanks for this!

I too am learning about batteries. I’ve not found a single source of all the small electrical system info we might want as CI owners who want to understand what’s going on with design, battery & charging equipment selections, service life, and alternatives.

Between this and several previous campers, here are a few gleanings:

An AGM (absorbed glass mat) is a type of Sealed Lead Acid (SLA) battery. We *must* use an SLA in our trailers, as the battery compartment design does not provide the ventilation required for a non-sealed battery.

My understanding is similar to what Steve and Karen has posted above - a dual-purpose battery (cranking and deep cycle) is inferior in service life to a true deep cycle.

All... ALL lead-acid batteries should not be taken below 50% depth of discharge (DoD) for good service life, and should likewise live on an intelligent charger. Somebody posted about minimum storage temps, that in colder climates it’s better to get the battery and charger out of unheated spaces. Could be, I myself am in relatively mild winters west of the Cascades in the PNW. Maybe it’s different in the Rockies or the upper midwest.

Except that two deep cycle manufacturers publish test figures showing impacted but not horrible service life for AGM batteries that are brought to 0% DoD and immediately recharged. These test figures only apply to specific lines, including Victron Super Cycle (not all their AGM) and some C&D Dynasty UPS batteries.

My own history with 2 Victron Super Cycle batteries:

I did some long-term value calculations, represented in my lengthy CPAP power for boondocking thread (link), and decided to pay a 1.75x premium to get a Victron Super Cycle 60ah as a pony battery for my CPAP use, and it has been working well. I’ve not yet had to take it below 50% DoD, but it’s comforting to know that the battery will likely age-out at 10+ years before it is impacted by occasional deep draw downs.

I later decided to be adventurous and also installed a Super Cycle 100ah as a replacement for the CI house battery (link). The adventure was that I wasn’t completely sure that the big batt was going to fit. It was a close thing, and I’d caution similar adventurers that some modification of the battery hold-down may be required. Which is complicated because the hold-down is part of an assembly that also gangs lots of electrical connections... In all modesty, I’d suggest that most people should stick to batteries of the same size as their original, which size has varied slightly over the years.

The end result of a few years and the move from a 550 to a 560 is that I have 160ah of Victron Super Cycle, capable of occasional deep discharges. I suppose it’s important to note that for me CPAP therapy without pause is extremely important to my life and health. Along the way I went icebox and LED lights throughout.

A later unexpected bonus was that Victron created new firmware for their battery chargers I’d installed, and I now get lots of current and historical discharge/charge info on my phone via bluetooth.

 

Seth: I was hoping someone would do a summary. Batteries seem to be the Achilles Heel of trailer ownership. We all have one, and will eventually need to replace it. But unless we are electrical engineers we'll likely have very little knowledge up our sleeve of exactly how they they should be properly used and/or replaced. This isn't a car battery.

Trial and error is a poor, and expensive, way to do things. I also like to be prepared for when the time comes, that I'm not scrambling to pick up whatever is close at hand, that may not be appropriate for my purposes, or economical in the long run.

I don't blame CI for not including any of this techy data above, of from the other threads,with their manual. Too much information can be a bad (or at least confusing) thing too.

Thanks for clarifying the "sealed" aspect as well.

Knowing there's some AGM products out there that can handle an occasional deep drawdown is very helpful. It may just steer a few away from thinking that they need a Lithium for that very purpose.

Which was what this posting was all about at the start.

What goes around...

 

Thanks. It’s taken me a lot of figuring & research in part because...

I too don’t fault CI for not providing more battery info. What they do provide in the manual and new owner orientation is great guidance.

Where it gets a little trickier is that batteries, unlike almost anything else on the trailer, can be easily damaged, do have a limited service life, and a replacement can’t be economically/safely shipped from Necedah. Batteries are hazardous materials as shipped; they go by truck freight. And some of us bought pre-owned trailers (no orientation, maybe no manual)... there is no national dealership or service network... etc.

Those who can do swing by Wisconsin for service! Those who can do so learn from this site and other research. Others have hit & miss experience with finding good RV service locally. Good shops do exist. Batteries are trickier...

I was glad to read that fernlane had a good replacement experience with a Trojan Group 24 AGM. Trojan has an excellent reputation, and has good distribution nationally. At 76ah fernlane’s batt matches the original capacity for those who originally ordered the large-capacity option.

For reasons given above, I was always looking for more capacity and a backup system, and am happy to have them!

PS. In various phone calls and emails Cary & Craig have always been supportive of my projects, consultative in their responses to my questions, and ready to help!

 

Seth: I am actually working on Battery Primer in a separate new thread, that will enhance and amalgamate what is included with the Manual, the many tidbits that we can "take to the bank" on this thread and other related battery/electrical UCIF threads. And some third party sources.

It will certainly be open for comment, additions, retractions, deletions... for all the reasons you pointed to above. I want to stick to the factual stuff, as opposed to the personal preference stuff, and make it as utilitarian as possible. So no one is wasting time and money getting a new battery every two years. Or finding that it doesn't fit. Or fit their trailering needs. Or doesn't meet their expectations. Or worse.

Stand by.

 

yep, the Trojan is over four years old at this point. Trojan may have an excellent reputation but the first one I received from N Arizona W&S turned out to be bad. After having killed the original AGM, that experience was a real hair puller. The Northern Arizona folks were great though and sent a replacement no problem.

We spent six nights last February dry camping in Big Bend with our dometic fridge and 85 watt panel with no issues. I never had to use the TV & Ctek to charge during that time.

I doubt I've ever taken it below 60%, at least according to the trimetric. I pay a lot of attention to the battery and try to squeeze whatever charging I can out of the sun.

I do wish there was an easy way to know what the actual capacity of the battery is. I'm sure it's diminished from new at this point but unfortunately even the trimetric isn't much help in this regard. It simply measures amp-hours used as a percentage of the total capacity I tell it. I use 70 ah (it wants increments of 10) so I do have a little fudge factor built in. There may be some way to tell the capacity with the the trimetric - if y'all know please tell me.

 

Ferlane: I didn't really see any CCA rating for your battery. But if it has one, and if you know it, and you ultimately found the TriMetric to be of little use in determining its remaining a/h capacity by itself (I don't have one myself), then you might want to get the battery tested under load. At the very least, if you found diminished CCAs, this might provide an additional indicator as to what stage in life it may be, in the absence of any way of obtaining accurate total a/hr reading at rest. This is also assuming that CCAs and total a/hrs diminish in a linear relationship in a Deep Cycle's life cycle. I don't know if a standard battery test will give you actual a/hrs remaining, having never seen or done one myself. Just spitballing that one at this point.

 

Ferlane: I was a little more curious about this as mine is about that age too. I discovered that only a sustained load test can give you a true a/hr reading. However I found this...

How to Determine the AH of a 12-Volt Battery

Seems to be do-able without taking it out, and having to take it to someone. Just need to get the resistor.

 

thanks for digging this up. I'd love to be able to do this process but the 550 is stored in a remote location (inside, plugged in to shore power) so given the length of time the process would take, it just ain't gonna happen.
I'm pretty confident that this battery is in decent shape so while I'm going to monitor it when camping I'm also not going to sweat it too much.
As a point of comparison, I've used AGM batteries for years in a small airplane and they seem to last a *long* time. I think I changed out the last one after 8 years just because I thought it had been long enough. I don't leave this battery on a charger all the time but do trickle it some in the winter.

 

NW. I might just try this for giggles. Just to see what a consistently-tended 4 yr old standard lead-acid battery might be doing. COVID project.

 

I'll be very interested in the results.

Here's a little more data for you. Today when I was in the hangar with the 550, I noticed that I hadn't plugged it in after the last trip. It was returned to the hangar on 10/6 and was almost certainly fully charged at that point.

Today the trimeteric said 12.4 volts and 84%. 84% of 70 (the full charge amp-hour value I put into the trimetric) equals 58.8 amp-hours. 12.4 volts is very close to 80% full charge so 80% of 76 amp-hours (the rating of the battery) equals 60.8 ah. If this math is reasonable, this says that I've lost a little more than 3% of full capacity over the four years.
I'm not sure this would hold for every state of charge but if it's even close I'm pretty happy. 3% capacity loss over four years sure doesn't seem like much to me.

Of course, another thing I need to think about is why the battery lost 16% in 12 days ...