Battery Replacement

[bobm]

I think it may be time to replace the batteries on the boat I bought in march. I have a 35' Ericson sloop with a 25HP Universal diesel. The previous owners notes indicated the house bank is 1 and the starter bank 2. I looked at each of the two banks and am a bit confused by what I found.

House Bank 1 - Three LifeLine Starting AGM GPL-3100T units
Starter Bank 2 - One West Marine AGM 79 Ah group 24 unit

Looking up the LifeLine models their information specifically states these are NOT deep cycle batteries and are "specifically designed for the rigorous cranking demands". The West Marine unit is listed as 'dual use', deep cycle and starting power.

I would think bank one should be three deep cycle batteries and bank two is OK since it is dual use? Is it common for people to install starter batteries for 'house' use?
Thanks

 

[Loren Beach]

Observation: The more you learn about batteries, the more cynical you may become about some marine product vendors.

I am too uneducated, so far, to even start to reconfigure my boat's charging and storage scheme. I have two 6 volt GC flooded batteries for our house bank, and one 12 volt spiral-cell AGM for the emergency backup--- kind of "old school." Stock alternator. Solid state shore power charger.

Is there a reason to replace the present batteries? (I presume that your alternator, shore power charger, and power management electronics are all technologically matched to you present AGM chemistry.)

 

[steven]

Best battery configuration really depends on your use cycle.

do you really need to draw down 50% or more, over a 2000 times ?
I daysail + an overnight locally say 10 times a season and require very little house power- so its cheaper to use starter (or dual use whatever that is) batteries on both banks.
And also that way #2 is a backup starter.

But if you do lots of multi-day or multi-week outings and need lots of house power, then it might lean towards deep cycle for #2bank.

Live aboard or distance voyaging are whole different stories.

From https://www.power-sonic.com/blog/deep-cycle-battery-everything-you-need-to-know/

 

[G Kiba]

I am under the opinion that a deep cycle battery will start my 2 cylinder M18 just fine. I replaced both batteries with two identical deep cycle AGMs. Seems to work great and I don't have to worry about setting different charging profiles.

 

[Jerry VB]

Why I can only justify buying flooded lead acid batteries.​

Soooo, running my seasonal numbers against the PowerSonic graph.

Given:

• A battery needs to be replaced when it can only provide 80% of its rated capacity (Generally Accepted Number, also indicated in the graph above).
• The graph is based on 100% discharge for every cycle.
  • Rule of thumb: if you discharge to 50%, you get more than twice as many cycles (200 cycles => 400).
  • Rule of thumb: if you discharge to 75%, you get more than four times as many cycles (200 cycles => 800).
• We mainly day sail so our battery use is keeping the refrigerator running while sailing. Semi-arbitrary estimate is 5 amps current draw.

From our sailing log, we sailed an average of 18nm per excursion at (roughly) 5kts => ~3.6 hours x 5 amps => ~18 amp-hours per discharge cycle. We have two Group 24 batteries (~80AH each). This indicates we discharged our battery down to about 80% per sailing outing so we should be getting more than 800 cycles before replacement.

We went sailing 28 times this year, which means we put 14 discharge cycles on each battery since we use the two batteries alternately. With an expected life of 800 cycles, they should last 57 years. The battery will die of old age before I come anywhere near using up its cycling capacity.

In practice, my batteries have typically died of old age aggravated by abuse (not topping off the water regularly). Looking in my historical logs, I see a replacement after 10 years, 7 years, and then another 7 years. My current batteries came with the boat and, according to the PO, were purchased in 2009.

YBLMV

 

[Pete the Cat]

Some really sensible advice here on batteries. The boat show guys would have you buying lots of exotic stuff and some folks seem to just love outfitting their boast for cruises they will never take. Simple for most of us is best. If you are going for an extended cruise or big passage, more attention is required.

 

[Tin Kicker]

I'd begin with making sure the batteries are connected as described, with Bank 1 to Switch 1, & vice versa.

I have the same West Marine Group 24 and motor. As you wrote: "The West Marine unit is listed as 'dual use', deep cycle and starting power." What is not stated is that the battery has 500-550 cold cranking amps (CCA) (depending on whose specs you use) and the Universal MX25 only needs 190 CCA.
Motor spec sheet: https://www.westerbeke.com/advanced specs/universal m-25xpb (2012).pdf

That's why the single battery works fine as a starter battery. It also has slightly thicker lead plates, which is why it is called a "combo."

The LifeLine batteries are designed for higher CCA but don't suffer when discharged at lower rates. Having three for a total of 300 Ah is a bit of overkill but I'd guess the previous owner did it so that the bank has about 150 Ah of usable power, since about half the rated Ah for lead-acid is usable without damaging the battery.
Spec sheet: http://lifelinebatteries.com/wp-content/uploads/2015/12/GPL-3100T-Rev-A.pdf

You didn't mention which battery needs replacing, but if it's the LifeLines there are less expensive ways to get 150Ah of usable power since they are $400+ each. That's about the price of a single 100Ah Li-Ion name brand these days, and you can get LiFePo4 trolling motor deep cycle batteries for less than $300. Just don't turn the selector to "Both" if there's a lead acid wet or AGM on the other bank.

 

[Nick J]

I'd begin with making sure the batteries are connected as described, with Bank 1 to Switch 1, & vice versa.

I have the same West Marine Group 24 and motor. As you wrote: "The West Marine unit is listed as 'dual use', deep cycle and starting power." What is not stated is that the battery has 500-550 cold cranking amps (CCA) (depending on whose specs you use) and the Universal MX25 only needs 190 CCA.
Motor spec sheet: https://www.westerbeke.com/advanced specs/universal m-25xpb (2012).pdf

That's why the single battery works fine as a starter battery. It also has slightly thicker lead plates, which is why it is called a "combo."

The LifeLine batteries are designed for higher CCA but don't suffer when discharged at lower rates. Having three for a total of 300 Ah is a bit of overkill but I'd guess the previous owner did it so that the bank has about 150 Ah of usable power, since about half the rated Ah for lead-acid is usable without damaging the battery.
Spec sheet: http://lifelinebatteries.com/wp-content/uploads/2015/12/GPL-3100T-Rev-A.pdf

You didn't mention which battery needs replacing, but if it's the LifeLines there are less expensive ways to get 150Ah of usable power since they are $400+ each. That's about the price of a single 100Ah Li-Ion name brand these days, and you can get LiFePo4 trolling motor deep cycle batteries for less than $300. Just don't turn the selector to "Both" if there's a lead acid wet or AGM on the other bank.

What kind of 100ah lithium batteries can you buy for $400? I've seen some on Amazon for around that with good reviews, but I wouldn't say they are name brand. Are they Li-Ion or LiFePo4? A good reliable LiFePo battery for $400 is a great deal compared to AGM or FLA. Paired with a DC to DC charger to minimize the changes to the charging system, and lithium would be within reach for most.

 

[Loren Beach]

I am under the opinion that a deep cycle battery will start my 2 cylinder M18 just fine. I replaced both batteries with two identical deep cycle AGMs. Seems to work great and I don't have to worry about setting different charging profiles.

According to an experienced mechanic friend of mine, you and I could both start our small diesels with something like a motorcycle battery.... It's a lot of current, but only for about 3 to 5 seconds. And that's why he also said we should never worry about a "need" to have a starting battery. A spare battery bank, yes, but for starting, the house bank will do fine.

 

[u079721]

According to an experienced mechanic friend of mine, you and I could both start our small diesels with something like a motorcycle battery.... It's a lot of current, but only for about 3 to 5 seconds. And that's why he also said we should never worry about a "need" to have a starting battery. A spare battery bank, yes, but for starting, the house bank will do fine.

That was pretty much my approach. I had a couple of the largest 12V batteries I could fit (group 31?) as my main bank, and used it for everything, house and starting. Worked just fine. I did have a separate size 27 starting battery as a back up in case the main bank somehow got run down to the point where it wouldn't start the engine, but fortunately that never happened.

 

[Christian Williams]

That's my approach too.

 

[jtsai]

Great point Loren. Many of us spent more time and energy researching and improving our boat systems to meet these illusive "best practices" than on-the-water time enjoying the pure joy and challenges of sailing.

Jerry VB, my experience with energy consumption is similar to yours during my time cruising the Chesapeake Bay. With the refrigerator running the entire day/night (cycle on/off) and operating engine roughly 1/2 of the time, the batteries need to be charged at marina every third night. However I can go one to two weeks not visiting marina if not running the refrigerator. Diet does get boring though.

One observation from my recent visit to the beautiful SF Bay area, it seems most of the sailings there (and at other beautiful CA coastal areas?) are day-sail, marina hop, or offshore. There isn't many protected anchorages like at the east coast where our sailing destinations are remote anchorages. In that regard, concern with energy consumption is mainly about starting engine, whereas the east coast sailors/cruisers require more robust energy management system.

The geographic locations have much to do with how we sail, how we use the boat and how are boats constructed. That is why Island Packet have abundant open ports, PNW boats have pilot house, and New England boats have lavishly varnished wood.

 

[Christian Williams]

A bigger alternator with a smart regulator would replenish batteries much faster for such cruises--especially when motoring a lot, as is usually the case. My installation on the 32-3 is here.

 

[TrueBlue]

Yeah that 32-3 setup is clean although I don't see the batteries or charger or controller. So hard to visualize the whole setup.

Also what really helps is having a DC to DC Charger like this:

https://www.renogy.com/battery-chargers/

This will allow you to recharge your "House Battery Bank" via the alternator and/or attached solar. Without draining or killing your Main starter battery.
Many of these allow you start your engine off of the house power bank in case main battery dies.

I do a lot of low voltage setups for work and have learned that usually the more simple you make the system the more reliable and easier to trouble shoot it is. I do plan on at least having one folding or mounted solar panel to get a charge in a pinch.

 

[Pete the Cat]

A bigger alternator with a smart regulator would replenish batteries much faster for such cruises--especially when motoring a lot, as is usually the case. My installation on the 32-3 is here.

Actually, I will take issue with that statement's factual basis. While it is certainly true that a bigger alternator will--for a short period--when operating at rated output (which they very seldom do, due to heat and resistance) using a "smart" regulator will put out more amperage initially, but over the whole cycle of charging, a smart regulator will more likely lengthen the time that it takes to get even the largest alternator to fully charge any battery bank. Smart regulators generally taper the charge delivered after a short period of full output and most often have heat sensors on the battery, the alternator. or both so that the alternator output does not put so much current into the batteries that they get too hot and so you do not burn up an alternator. A smart regulator actually limits the output and tapers the charge output of your alternator to be kind to your batteries--tries to keep them from heating and gassing when they are significantly discharged. So it is going to take longer (and be safer and nicer to significantly discharged batteries) to fully charge batteries with most smart regulators. I have used smart regulators and high output alternators for about 30 years of cruising and only when I got a battery monitor system did I begin to understand how my system actually worked. There is a lot of "more is better" and "bigger is better" and more technology is better in sailing (as just about everywhere else) but this is one of those exceptions for most folks. Folks with very large alternators, sophisticated smart regulators and huge battery banks who are not knocking their batteries down to 50 or 60% of capacity and who do not motor daily for hours on end--are probably chronically undercharging their batteries--unless they get to shore power charging at some point. Not sure how far I want to go with this. If you have batteries with very large acceptance rates--as a few of the very latest most exotic types do--there may be an exception here, but with most FLS and AGM batteries a limiting factor of charging is the acceptance rate of the batttery and the smart regulator tries to keep your output inside those parameters by limiting the charging outputs. It will take longer to fully charge your batteries with a smart regulator but you will have less likelihood of burning up your batteries or your alternator. I agree with the sense of others in this thread that you need to start with sizing your batteries to your actual usage and work backwards from there with the rest of the system capability.

 

[Kenneth K]

Also what really helps is having a DC to DC Charger like this.......

This will allow you to recharge your "House Battery Bank" via the alternator and/or attached solar. Without draining or killing your Main starter battery.

Why would a DC to DC charger be required for that? Mixed battery types?

 

[Christian Williams]

Pete, what's a stock Motorola alternator put out, 15 amps steady?

I discharge my two group 31 batteries to 60 percent and recharge them to 85 percent in less than one hour with a Balmar 100.

The monitor shows 60 or more amps output at first, quickly diminishing to 20 or so, at which point the monitor shows 85 percent charge and I turn the engine off.

You're saying a car alternator does better than that?

 

[Loren Beach]

I wonder if the alternator controller is the key. My old Motorola 50, was the stock item on the M25XP, but it was internally regulated, so the charging undoubtedly dropped off before the battery bank received a full charge.
Our new diesel has the optional 70 amp, but likely would have the same problem. I suspect that most of us "casual users" get by because our boats live on shore power at a dock most of the year, and we are out cruising for a month at most, and a lot of that involves nights at marinas with power.

 

[TrueBlue]

Why would a DC to DC charger be required for that? Mixed battery types?

Well you can mix battery types if you want like a AGM Starter and Lithium house batteries but it allows the house batteries to charge more effectively and also acts like a isolater so you can never run down your starter battery. So when your engine is running it will charge the House Battery via alternator when engine is off and your sailing it will charge off solar.

Here's a video that explains it pretty well just substitute RV for Boat and Driving with Motoring

 

[Christian Williams]

I suggest anybody considering an upgraded alternator and "smart" regulator do their own research.

Maine Sail is a place to start at https://marinehowto.com/category/alternators/