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Old 04-10-2020, 08:34 AM   #1
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Battery types discussion

I have been researching the newer battery types in anticipation of buying a newish RV with a marine type DC compressor fridge rather than the more typical absorption fridge. With this change, the DC requirements of RVs become very similar to our boats. So the following is a review of the various battery types that are available today with pros and cons of each:

Traditional flooded cell golf cart batteries:

I have long advocated that GC batteries provide the most bang for the buck for marine use and for many applications that choice is still the best.

1. Can only be charged at .25C
2. Should not be discharged below .5C
2. Slow to charge beyond .85C
3. Heavy and require periodic water checking and addition
4. Will sulfate if left at a partial state of discharge
5. Cost about $100 for 100 Ahs at 12V, more for premium brands

AGM batteries:

1. Same as FLAs but don't require water checking.
2. Some say they can be charged a little faster and discharged a little further than FLAs
3. Cost about $200 for no name to $300+ for brand name 100Ah at 12V

Firefly carbon foam batteries:

1. Can be charged at .4C with no harm
2. Can be discharged to .2C routinely with no harm
3. No sulfation risks and no maintenance
4. Cost about $500 for 100 Ah at 12V

Lithium batteries with integral BMS*

1. Can be charged at 1C and discharged to near zero with no harm
2. No sulfation risk and no maintenance
3. Light, about 1/2 of the above types
4. LiFePO4 chemistry, the only kind considered for marine or RV, use has very low fire risk
5. Requires a lithium specific charger for best performance as well as correct parameters for an externally regulated alternator
6. Cost about $1,000 for 100 Ah at 12V

*The only kind I would consider for a boat. External BMS lithium battery systems are for the technogeek IMO.

So GC FLAs give the most usable Ahs for the buck 100*(.85-.5) = 35 Ah or .35Ah/$. AGMs provide .18 to .1 Ah/$. Both have risks leaving partially charged for long.

Fireflys provide (100*(.85-.2) = 65 usable Ahs or .13 Ah/$. Lithiums provide 90 usable Ahs or .09/$. Note that this doesn't consider charger or alternator upgrades that Lithiums may require.

So I would go with GCs if I had lots of room, weight wasn't a real consideration and had decent access for maintenance. AGMs if maintenance was an issue but Fireflys are also competitive if you consider usable Ahs. And Lithiums if room and weight were big considerations.

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Old 04-10-2020, 08:41 AM   #2
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You forgot to mention gels. They charge and discharge at rates closer to FLA than AGM, but are more voltage sensitive. They're a bit less prone to sulfation and tend to have a longer cycle life than FLA or AGM.

The non-FLA options also have more mounting flexibility and less ventilation requirements, which may open up more options depending on your mounting situation.
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Old 04-10-2020, 08:44 AM   #3
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Generally a good post.
Other considerations depending on use would include:
Shortening of life expectancy if not completely recharging.
Expected duration of ownership relative to pay back.
Normal KW of available energy relative to size.

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Old 04-10-2020, 10:20 AM   #4
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Quote:
Originally Posted by DavidM View Post
AGM batteries:
2. Some say they can be charged a little faster and discharged a little further than FLAs

So I would go with GCs if I had lots of room, weight wasn't a real consideration and had decent access for maintenance. AGMs if maintenance was an issue but Fireflys are also competitive if you consider usable Ahs. And Lithiums if room and weight were big considerations.

I think (from memory) both Odyssey and Lifeline recommend charging at .4C. You might have a look at their specs...

Your conclusions look sound.

I'd maybe add a comment about AGM/Firefly batteries being a decent choice if off-gassing were to be a concern, or if some kind of non-traditional mounting might be required. I presume that applies to lithium, too. Lots of discussion on CF and here about lithiums needing a BMS...

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Old 04-10-2020, 11:44 AM   #5
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You are considering only initial cost. If you intend to own this RV only for a year or two, then that is appropriate. If you intend to own it at least through one battery replacement cycle, then lifetime cost is much more appropriate. In lifetime cost, you may find that the LFP batteries win hands down, as most studies show. Their other advantages then become icing on the cake. Frequency of use will be the biggest independent variable in lifetime cost, with more frequent use favoring the more expensive technologies. So for example, total AH delivered/$:

Flooded: 500 cycle life x 0.35AH/$ = 175 AH/$ lifetime
LFP: 3000 cycle life x 0.09AH/$ = 270 AH/$ lifetime

The LFP are much cheaper. But only if you own them long enough.
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Old 04-10-2020, 11:58 AM   #6
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Folks that are new to living on batts may find the old standby deep cycle LA batts are best to learn with.

Even with a SOC meter and low voltage alarm, enough "stuff" happens that you will kill the batts way down at least a few times.

Most of the batts have a warranty that can save you from financial harm as you learn.

Be advised the big chain stores are easy to return the batts to, but their computers all talk to each other , and eventually you will be turned away.
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Old 04-10-2020, 12:25 PM   #7
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I went through this same exercise for my boat. I echo the sentiment that if the batteries are in an RV that is going to be sold somewhat soon, then Flooded lead acids, hands down. But my electrical and electronics hero - Jeff Cote - talks about FLA's being murdered, not dying. He talks about the unwritten contract that you agree to be committed to properly maintaining the batteries, never discharged below 50 % and always fully charged. He says most start out honouring that contract but over time, life happens and you don't charge properly and thus your batteries are relegated to the palliative battery care unit.

I will link to a video that is quite long, but everything you wanted to know about batteries. With lithiums realize you are committing to a "system" not just the batteries and you best understand that statement or you could regret lithiums latter.

Here is a video I posted I don't think anyone watched, its over an hour and he will talk briefly at the end about the problem of lithiums and the alternators that most use (hint: they will burn out).

Fireflies when abused can last approximately 1200 cycles, if well maintained and only discharged to 50 % and recharged, they will last 3600 cycles. I went with Fireflies because I didn't want to get involved in the Lithium system.

https://www.youtube.com/watch?time_c...ature=emb_logo
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Old 04-10-2020, 12:34 PM   #8
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Hi DavidM,

I'm with DDW here. Consideration of simple cost per AH of battery capacity is misleading, should you desire to own your RV for more than a year or two. Unfortunately, life cycle costing is complicated, particularly when you factor in the real costs of items such as generator run time, engine run time, inverter/charger characteristics, efficiencies, etc. This is very difficult to do without some computational aids.

Some years ago, I tumbled on this lifecycle calculator, which you might find interesting. And while it predates battery chemistries such as carbon-foam AGMs, and Lithium, you may be able to edit it accordingly, if you can obtain the necessary input data from your battery vendors of choice.

Battery Cost Model Inputs and Outputs: Gel, AGM, Flooded

The von Wentzel website makes for a pretty good read, should you be so inclined!

Regards,

Pete
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Old 04-10-2020, 12:41 PM   #9
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When we purchased Stella there was a house bank of 5 Lifeline 8D’s, about 1,250 ah, split into two sub-banks. During our first cruising season (to/from Bahamas, 5 months) we quickly realized that they were near end of life. Voltage dropped quickly for an appreciable load and charge acceptance was low. Towards the end we had to start the generator to use the dinghy lift.

One of the 8D’s was separate and somewhat accessible. The other four - ‘how the hell did they get those in’. I just replaced the separate 8D with 3 Lithionics 280ah batteries with external BMS. The Lithionics weigh 45 lb/ea, so for the same weight and nearly same footprint I have 840ah vs. 250 ah. I rewired the remaining 4 8D’s into one sub-bank as backup and have the Lithionics as primary sub-bank.

I looked at other lithium brands and Fireflies but Lithionics and Victron were the only options which had sufficient capacity and fit in the available space.

Lithionics was very helpful with details. We were cruising past Clearwater (Lithionics HQ), stopped at a marina, picked them up with an Uber, and installed them in half a day. I had previously prepared mounting for switch, fuse, BMS and combiner.

Getting the 8D out was an adventure. With planning and mechanical lifting, I managed to remove it myself without much physical effort. Glad it’s gone and would not buy another battery that size.

Pleased so far after two months cruising, mostly at anchor. I did not replace my existing inverter/charger, alternator/regulator. Lithionics provided settings for the Magnusine charger and existing controller, which has sufficient options to meet requirements.

We run a 12K generator twice a day for an AC holding plate fridge/freezer, water heater, ... Batteries recharge well within the time to re-freeze the holding plates.

Next project will be to add enough PV panels to cut generator use to once a day.
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Old 04-10-2020, 03:15 PM   #10
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David
It was interesting reading your post re: RVs. After returning home (and having some time on my hands to fill) I washed & waxed (Polymer) the MH. Next on the To Do list was to tackle repair of my battery compartment / tray and replacement of my 8 GC FLAs. Battys are original equip - now ~ 8YO - no problems noted but I'd rather do it now when I have time than wait for failure to gain another 6-12 mos. While FLAs are lowest cost they are also highest maintenance not only cleaning, filling but compartment maint. I removed and cleaned the slide tray & compartment the last 2 days (see pic) . I have some POR15 and intend to recoat with that (when Wx warms back up) and reassemble. This AM entailed a trip to Sams Club to pick up 8 AGM GC2s.
My rationale is/was...
  1. RV / MH Mfg want the lowest $ so install FLAs in a steel compartment, tray, roller bearings - not concerned with longer term care & maint
  2. I will rework the tray once but don't want to do it again
  3. Size & Wt not an issue - little advantage reducing size/wt.
  4. We do relatively little boondocking and have a gen for recharging
  5. I've had good luck with East Penn Deep Cycle AGMs on the boat and Sams Club Duracell AGM GC2s made by East Penn.
  6. Availability of AGM GC2s is EZ in most of the areas we ntend to travel in
  7. Not sure how many more years we will be motoring and doubt we would benefit from the additional life of LiFePO4
Bottom Line I felt AGMs provided a reasonable cost premium (2X) to avoid the Batty & compartment maint of FLA's and could not come close to rationalizing the additional premium of LiFePO4 (another 4-5X$). If I used our MH differently I might, but only might have reached a different conclusion.
Be safe and Stay in touch
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Old 04-10-2020, 03:32 PM   #11
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...Bottom Line I felt AGMs provided a reasonable cost premium (2X) to avoid the Batty & compartment maint of FLA's...
I agree. We changed out the FLAs in our van and went to AGMs. No maintenance and a clean battery compartments. Yikes Don!!

David: Potentially how big a bank are we talking about?
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Old 04-10-2020, 05:35 PM   #12
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Don and Larry:

Well we still are a long way from buying, but i am thinking hard about the simple, no extended width body, Sprinter based RVs like the Winnebago Era. Torn between the simplicity of aft twin beds (the 70/170A) and the extra room of the forward slide couch that folds down and then you drop a queen size Murphy bed (the 70/170M). This allows a very nice dry bath aft. The Murphy queen does allow you to keep the bed made until we need to drop it.

I need to see both to know.

I understand that the Winnie Era and all others like it have a coach battery compartment aft of the rear wheels port and starboard. They are each big enough for a Group 31. That is why I am looking at Fireflys: for more usable capacity from 200 total nominal amphour G31s. Firefly gives you 160 Ah usable vs 100 for FLAs, AGM or not.

I know I asked both of you about getting filled up with LPG along the way and you said generally no problem. I have checked a few areas with Google Maps and found one or two refill places in each moderate size town. FWIW Tractor Supply usually has fill tanks that can do it. Wow, the things we do when we are sitting around the house bored stiff.

More to come. Hope y'all are doing well.

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Old 04-10-2020, 06:02 PM   #13
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Filling LPG no problem with our previous MHs. Pilot / FJ convenient, UHaul, Most private CGs, and lots of LPG distributors EZ to find with today's connectivity.
You guys have a real space constraint and different chemistry reqd to get batty capacity. With room & design for 8 GCs my choice was easier.
I'm starting to think & plan for what next for batty banks on the boat. At least thinking AGM GCs to replace AGM 8Ds but hopefully have a few more years left on my 8Ds.
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Old 04-10-2020, 06:52 PM   #14
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Dave, based on your calculation, the GC batteries cost $2.85/usable Ah (.35ah/$), and $2/Ah if you use the more simplistic 50% DOD guideline.


The LFP batteries I'm putting in my boat from MG Energy (turn-key system) cost about $4000 for a 280Ah, 24V pack. That's about $7.25/Ah.


That's certainly more expensive up front, but a good bit less than your earlier assumption. And the jury is still out, and will be for a very long time determining how many cycles one can get from LFP is boat service. But the rock bottom minimum is 2000 cycles based on dozens of studies pushing LFP to its extremes. Boat life if comparatively very gentile, and most people are figuring that 3000-5000 cycles is a safe bet. That's a LOT more cycles than you will ever get out of GC cells. But it's future value, not present value.


And the other consideration, which is what has me completely sold on LFP, is the way it works on a boat, and how carefree power management becomes. You don't have to worry about the batteries being at partial charge, or how long they have been there. It simply doesn't matter. And you don't have to fret over bringing them back to full charge, or worry how long it's been since you did it. You just use them. And generator time, assuming you use one, is a good bit shorter too, even with the same charging equipment you have today. Just getting rid of the absorption tape will cut the time to do a full charge by around 20%. At least that's what I have experienced. For me, this is worth paying more to get these benefits. How much more is an individual decision.
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Old 04-10-2020, 10:59 PM   #15
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I am looking at replacing my house bank soon. At present I have 6 x Odyssey PC1800-FT, which are 7.5 years old, for a total of 1284Ah. I have unintentionally flattened them completely a couple of times due to power outages at the marina. That likely took some of the life out of them, and I think I'm down to about half of their capacity.

One possible replacement that has caught my eye is the Victron SuperCycle AGM.
https://www.victronenergy.com/upload...battery-EN.pdf

Given my marina power outage issue is unlikely to go away, the potential of these Victron batteries to tolerate 100% DoD has some appeal. I have not been able to find any reviews of them, but would appreciate any comments from folks here.
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Old 04-11-2020, 01:01 AM   #16
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I'm not getting the dirty battery compartments with flooded batteries. I have had eight GC2s mounted in two battery boxes for four years. They are virtually as clean today as the day they were installed. Have I just been lucky? I have had to add about two ounces of water to each cell every two months since installation which, to me, is one of the easiest maintenance tasks aboard. I do have ready access. I have no particular affinity to any battery type but AGMs offer little to me except more cost. If my access was difficult then that would be a different story.
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I agree. We changed out the FLAs in our van and went to AGMs. No maintenance and a clean battery compartments. Yikes Don!!

David: Potentially how big a bank are we talking about?
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Old 04-11-2020, 06:12 AM   #17
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"I have been researching the newer battery types in anticipation of buying a newish RV with a marine type DC compressor fridge rather than the more typical absorption fridge. With this change, the DC requirements of RVs become very similar to our boats."


GASP!!! An electric reefer is fine plugged into a power pole , but the task of creating about 100ah per day to refill batteries is thankfully not needed with the RV system.


Most larger reefers will get 3 weeks to a month from a 20lb (now only filled to 15 lbs) . Even smaller RV have 2 tanks or a DOT cylinder that holds 30#.


So even with cooking the reefer will only require a trip to refill every couple of months.
My last propane reefer was probably 60years old , didn't look great (stored outside on aft deck) but worked fine , with never a dead battery onboard.


Many RV items are identical to boat gear but installing probably the worst , most power hungry boat gear , the DC reefer might not be an improvement for any RV.
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Old 04-11-2020, 06:33 AM   #18
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I'm not getting the dirty battery compartments with flooded batteries. I have had eight GC2s mounted in two battery boxes for four years. They are virtually as clean today as the day they were installed. Have I just been lucky? I have had to add about two ounces of water to each cell every two months since installation which, to me, is one of the easiest maintenance tasks aboard. I do have ready access. I have no particular affinity to any battery type but AGMs offer little to me except more cost. If my access was difficult then that would be a different story.
John
I'm guessing that at least part of the difference on MH vs boat is due to environment and containment material.
On MH the battery "bay" is usually open to the bottom of the chassis for obvious reasons where on boats they are in the ER
Your batty boxes are probably plastic? Where as on MH my tray slide and compartment are painted steel.
The battys get dirty from road dirt and I try to clean them periodically. The steel ends up rusting as the factory paint is not a great barrier and once the corrosion starts it just gets worse even though I wash down with a basic solution to neutralize the acid residue. It would be a major task to remove cabling and battys for a thorough and proper cleaning so there are areas that remain wet and likely still acidic.
The pic of my slide tray is after about 7-8yrs of use and 1st time battys have been removed. I have read about people topping each cell of a FLA with mineral oil as a way to reduce the acid loss through the fill caps. Also aware there are after market caps that reduce the emission as does a watering system. I have gradually started using AGMs and like the result. I do agree that the convenience comes at a cost but a trade off I'm willing to make. Everyone has their priorities and gets to decide which trade offs are best for them so I'm not trying to convince anyone but rather explaining my thought process.
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Old 04-11-2020, 07:35 AM   #19
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Thanks for the explanation. Makes sense now. AGMs, then, seem worth the cost in a motor home. Yes, plastic boxes.
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John
I'm guessing that at least part of the difference on MH vs boat is due to environment and containment material.
On MH the battery "bay" is usually open to the bottom of the chassis for obvious reasons where on boats they are in the ER
Your batty boxes are probably plastic? Where as on MH my tray slide and compartment are painted steel.
The battys get dirty from road dirt and I try to clean them periodically. The steel ends up rusting as the factory paint is not a great barrier and once the corrosion starts it just gets worse even though I wash down with a basic solution to neutralize the acid residue. It would be a major task to remove cabling and battys for a thorough and proper cleaning so there are areas that remain wet and likely still acidic.
The pic of my slide tray is after about 7-8yrs of use and 1st time battys have been removed. I have read about people topping each cell of a FLA with mineral oil as a way to reduce the acid loss through the fill caps. Also aware there are after market caps that reduce the emission as does a watering system. I have gradually started using AGMs and like the result. I do agree that the convenience comes at a cost but a trade off I'm willing to make. Everyone has their priorities and gets to decide which trade offs are best for them so I'm not trying to convince anyone but rather explaining my thought process.
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