House batteries - spreadsheet comparison of difference sizes and technologies

[Tmbouman]

Hi Everyone,
I currently have two batteries on my 305, but want to use those as dedicated starter batteries and add house battery capacity (~400RC). I found it rather confusing to figure out which battery was the best for this application, so I made a spreadsheet:
https://docs.google.com/spreadsheets...#gid=672549354

It looks like interstate AGM is current the best bang for my buck. My questions:

1) is my spreadsheet taking into account all of the important factors
2) Are there any battery manufacturers I need to add to my list?

Notes:
-I take into account the difference in depth of discharge (DoD) for acid vs agm vs lithium
-I take into account i'll need 2x 6Vs to make a 12V system
-I do not take into account that lead acid requirement more routine maintenance and handle vibration worse
-I do not take into account the actual cycle life, just assume each battery has the same cycle life for a given DoD. For example, it assumes lead acid at 50% DoD has the same cycle life as AGM at 80% DoD.
-I boat in Lake Superior and will maybe cycle these things 20-50 times a year, so the theoretical large cycle count capacity of lithium is not really worth it to me.

Thanks!
Troy

[2850Bounty]

It’s tough to beat “true” wet cell Deep Cycles batteries for a HLBB (house load batt bank).

With a shunt resistor style battery monitoring system you’ll be able to track Amp Hours in, and Amp Hours consumed.
The system will allow you view real time Amp Hour status and to prevent depletion greater than 50%.


.

[Alex_Mahon]

Nigel Calder's "Boatowner's Mechanical and Electrical Manual" (4th Ed.; (c) 2015) includes an excellent in-depth analysis of this issue. His bottom line is that properly-maintained lead acid batteries (never discharged below 50%; 4-stage charger with desulfation phase) are more economical over the long haul. As a result of considering his analysis (and other research), when the time comes (this summer?), I plan to replace my current Group 27 flooded house batteries (4 x AquaEdge 27DC120; 120Ah; 700CCA/825MCA; 165 Mins. RC; 57 lbs.; $86) with Group 31 flooded batteries sold by O'reilly's, which I believe are manufactured by East Penn (Deka) (4 x SuperStart Marine Deep Cycle Group 31; 31DCMJ; 105Ah; 675 CCA/845MCA; 210 mins. RC; 63 lbs.; $99.99). Included in Calder's analysis is the assertion that the heavier a battery is = more lead = more storage capacity. Included in my rationale is that O'Reilly's stores are all over the U.S. and they stand behind their batteries, which are very attractively priced, and Grp 31 batteries are only slightly larger than Grp 27 batteries (= easy refit). I concur with 2850 Bounty that a "must have" is a battery monitor that indicates battery status, use/draw, and remaining capacity in real time (e.g., Xantrex LinkPro). As an aside, I also recommend that every boat have Calder's 944-page tome on board - it's a very comprehensive single-source tutorial that covers the waterfront (Amazon; $46).

[Alex_Mahon]

One further comment. Troy - excellent chart; well-researched and presented. Thank you.

[MacPhid]

Our Trojan T-105's are rated for up to 80% discharge maximum, I presume fewer cycles at that level, but realistically in normal use 80% is probably not a normal discharge level when cruising from my experience. The point is it might affect your spread sheet results. The 50% discharge, while recommended as optimum, obviously doesn't mean they can't be discharged lower as required.

James

[Tmbouman]

Thank you everyone for your comments.

Bounty, I already purchased a BMV-712 from Victron. Thanks for the note

Alex, I'll order a copy of that book. Thanks for the tip. I added your battery selections to the spreadsheet. The O'Reilly compare well to the interstate's especially given your comment about warranty/ease of replacement. I live in a rural area so I have to see if I can even source an interstate. If not, O'Reilly might be a good option.
https://docs.google.com/spreadsheets...#gid=672549354

James, I tried to take this into account with columns K & L which reference cells B35-37


Someone recently suggested I look into USED lithium iron phosphate LiFeP04. I guess you can get them on eBay cheaper with 500ish cycles. So i'm going to explore that too. Thanks everyone!

[kwb]

Great Chart - I use the graduated colors for the key characteristics to make quick comparisons. It just makes it faster to look at this sort of wall of numbers.

[Alex_Mahon]

An additional thought: Since being a BOC member for quite a while now, I have followed the technical issues/questions postings of many other Members and Guests. Jeff Cote at Pacific Yacht Systems (www.pysystems.ca) is an absolute treasure-trove of extremely available and valuable marine electrical information, yet I have never seen his website cited as a source of assistance. His expertise in things electrical is vast, his informational posts are comprehensive, and his you-tube "how to's" are superb. Spread the word. The only downside is that if Jeff answers all our questions, we may not ask each other, and the depth of our exchanges may be diluted. Worth the risk, I think.

[purduepilot]

Agreed, Jeff's youtube videos have been awesome.

[Tmbouman]

Hey everyone,
So I updated the spreadsheet (including gradients, thanks kwb) to include the LiFeP04 option. If you are willing to spend the extra money upfront, it seems like a really good option:

LiFeP04 from eBay:
https://www.ebay.com/itm/Valence-U27...RoAAOSwPGNe7me 3
$1.45 $/Ah/1kCycles
-At 3000 cycle life, it would last me over 70 years at 40cycle/year.
-Have to buy a bms or buy something to talk to the internal BMS ($250?)
https://www.ebay.com/itm/U-Charge-Xp...M0AAOSwhZhdzpw m
-Have to add battery charger between alternator and batteries ($139)
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
-Weight: 84lbs for 250 usable aH
-Total install cost is $1,400
$500/batt x2
$400 for BMS and alternator charger
=1400

Lead Acid from O'Reillys:
-$1.90 $/Ah/1kCycles
-1 year warranty
-At 500 cycle life, it would last me over 10 years.
-6mo maintenance required
-Weight: 250lbs for 210 usable aH
-Total install cost is $400:
$100/batt x4

Just something to consider. Here is the updated spreadsheet:
https://docs.google.com/spreadsheets...#gid=672549354

[Norton_Rider]

..................... Here is the updated spreadsheet:
https://docs.google.com/spreadsheets...#gid=672549354

Thanks for the charts. Consider adding the Firefly Oasis Carbon Foam batteries to it. They are AGMs that can sustain an 80% to 100% discharge without adverse effects.

https://oceanplanetenergy.com/advanc...asis-group-31/

[Tmbouman]

Hi Norton, I added the Oasis batteries to the spreadsheet. At 3,800 cycles at 50% DoD, they are more expensive than O Reilly's lead acid. The benefits I would see for the additional cost is 1) don't have to top up with water every 6 months 2) better vibration durability 3) Don't have to replace them as often. Thanks for bringing them to our attention! Do you know their reserve capacity?

https://docs.google.com/spreadsheets...#gid=672549354

[ksanders]

I jist made a really simple Excel spread sheet comparing a Crown CR4 430 FLA to a Battleborn 100AH battery

I calculated the Watts available for each battery according to the manufacturers data and multiplied it by the number of cycles of life expetancy to 75% original capacity, again using manufacturer supplied data.

The crown is listed at 1200 cycles at a 50% Depth Of Discharge
The Battleborn is listed at 3000 cycles at a 80% Depth of Discharge

Again this is data provided by the manufacturers.

The Crown FLA had a cost of $0.22 per KWH produced over it's lifecycle
The Battleborn had a cost of $0.34 per KWH produced over it's lifecycle.

Not how I thought the math would work out, but there it is.

An interesting thought not just for boats, but for those considering home solar installations that store energy for use at night.
The cost of the energy storage alone exceeds what my local utility sells me energy for, not even counting the price of the solar gear. That is just energy storage.

[Tmbouman]

Hi Ksanders, thanks for the tip on crown and battleborn. I added them to the spreadsheet. Crown is $2.64/Ah/1kcycles Battleborn is $3.75. So you'd be better off buying O Reilly's FLA for the cost per Ah/1kcycles. Similarly the used Valence would be cheap than the battleforn if you wanted to do LiFeP04. Excellent comment on looking at storage cost vs shore power cost for those that dont anchor out much! Thanks for posting.

https://docs.google.com/spreadsheets...#gid=672549354

[Alex_Mahon]

As a semi- "gold-plater" of my 3270 via too many of the quite expensive modifications/upgrades I've made, I attempt, but too often fail, to add in a "reality-check" factor - i.e., at 76 years old with [hopefully] 10 years of active boating left, how much money can I/do I want to invest into boat improvements/modifications that I will never fully use? Troy's chart is instructive, e.g., lithium batteries, at about $1,200 each, have 4,500 life cycles at DoD. How many years of average use is that? It seems to me that one can easily build a system that will outlive our grandchildren. Reverse-engineering, starting with my 10-year "boat-life expectancy," my over-built gas 3270, optimistically valued at $40,000 in 2021 dollars, only needs about $1,000 in batteries (4 x house; 1 x start; 1 x bow thruster/windlass; 1 x emergency spare) over the next 10 years. My goal is to breath my last breath at the precise moment all my toys die and the IRS takes my last dime - a super-sophisticated battery bank buried deep in the bowels of an old boat makes a poor headstone. This is a long-winded version of the eternal "Can I do it/should I do it" conflict. Let new technology steal our hearts, but not our brains.

[Tmbouman]

Hi Alex, excellent point and I definitely agree. Interestingly enough, I am on the other side of the coin. I am 31 so would likely benefit from a long term solution, but I am still debating 1) how long will i have THIS boat and is it worth the upgrade 2) Lithium (even LiFeP04) prices are decrease significantly as manufacturers see the benefits of economy of scale so maybe I should just spend $400 now on FLA and see what prices look like in 5 years. Thanks for your continued contribution to this thread!

[Alex_Mahon]

Ah, to be 31 again. Even 60...

[cfoss]

One thing that has not been discussed is the charging system. A Lithium Ion battery will not charge properly and will likely be dangerous if just hooked up to an altenator.

For me, its AGM all the way. The big thing is the slow self-discharge rate as compared to a flooded cell. On a boat with infrequent use, and even less frequent attention (Just being honest), this has been a godsend.

My Marathon AGMs are entering their 6th year of service and still going strong.

Just NEVER discharge them all the way flat. They will not come back as well as a flooded cell.


Chay

[Tmbouman]

Good point Chay. A battery management system is needed with Lith (like $400 for LiFeP04s that I saw) and the charge restrictor between an alternator and Lith is like $139. This is needed because Lithium batteries will take all the power you can send them so it would run your alternator at max output frequently, which is obviously not ideal.

[watchthis]

I bought two of these 255 AH pigs five years ago. https://www.batteriesplus.com/productdetails/sligc145ut
With a young kid who likes to leave the fridge open and watch movies, we crush them every weekend and they have been fine. They were heaviest and largest AH capacity I could locate. In our area you can't swing a dead cat without hitting a batteries plus. Batteries plus always has an online coupon as well.

[Tmbouman]

Hi watchthis, thanks for the comment. Looks like they rank about 10th on the list. You can get similar spec'd 6V duracell golf cart batteries at sams club for half the price. These are $90 at my Sam's:
https://www.samsclub.com/p/duracell-...c2/prod3590228

https://docs.google.com/spreadsheets...#gid=672549354

[watchthis]

We don't have Sam's Club here and at the time, Trojans sold locally cost over $200 each. No complaints though as these have taken a pounding.

[watchthis]

The Duracell you linked to is only 215 AH whereas mine are 255 AH. Keep an eye on that rating as it is a detail that matters.