batteries

Gasman

Gasman

Member
May 30, 2015
80
Great Lakes
Boat Info
2001 29' sun dancer sold
2000 340 sundancer
Engines
Twin 5.0 mercruiser
7.1 v-drives
i have 2 questions about batteries... The first one is how often do you need to replace them??? i bought my boat 2 years ago so this will be my third season with the boat... I haven't had any issues with the motors starting or not holding charge... When at the dock i leave the boat plugged in and charger on to keep them charged and in the winter who while in storage i leave them on the charger also so they never go dead.... My next question is has anyone used an agm deep cycle marine battery??? they are almost double the price but from what i have read they last 5 times as long.... any feed back or advice would be great
 
Gasman

Apologize in advance for the long-winded response.

First a few truths:

Battery life is a function of
1. quality of the battery
2. quality of the charger
3. rate/frequency of discharge and depth at discharge
4. charge profile settings
5. type of battery
6. environment of battery

So... If you want the longest life you need to maximize all 6. Specifically speaking to your question, AGM's do NOT out last a Wet Cell. My comments (opinions) relating to items 1-6 now.

1. For simplification I will say there are 3 "classes" of batteries. Let's call them Standard, Premium, Super premium. Standard's are any battery you can get at an auto parts store with maybe the exception of Optima, Premium, are Oddsey, Trojan, Optima, maybe a few AGM's at the local stores, Super premium are Rolls Surrette (I think these cannot be beat), Mastervolt (Including some of the West marine made by them), Northstar(Good specs but not truly proven).

2. Regardless of the battery, if you have a basic charger it will not do them any favors, Premium charges put out specific voltages/amps as a function curve and if properly matched to your battery manufacturer will make your batteries last longer because you are doing what the manufacturer suggests. Just as an example If you buy a new truck and that truck say average gas mileage 15MPG, and you drive it like you stole it, we all know it will get worse mileage and overall the truck won't last as long, same concept with a battery, they need to be charged at a specific rate with a specific profile. (I'll stay away from brands but I will say this if it costs less then 300 bucks it not a premium charger)

3. Batteries are manufactured to be discharged at a certain rate (say the 20/hr rate) to a certain depth of discharge (say 80%). This must be set in the charger/charge profile to maximize battery life. You need to design your system around how you plan to use it and have the capacity to discharge at the set rate and be able to accomplish what you want before getting to the depth of discharge percentage (in our case, it's typically I want to spend a night on the hook without the genny running)

4. different charger brands will have different charge profiles, just make sure you buy one that closely matches the battery manufacturer's recommendations.

5. 3 basic types, I will let you make the decision.

1. Wet Cell Lead Acid: These have the longest life overall, with the most charge cycles with a BIG IF, they must be charged correctly and watered regularly, say once a month. They do offgas some, so if they are in the cabin this may be a bad choice, these batteries are still the best for 75%+ of boaters
2. Absorbed Glass Mat AGM: These are still wet-cell batteries but they are sealed, they do not have as many charge cycles as standard wet cells BUT they require no maintenance at all. The downside is they MUST have a specific charge profile AND if you damage them by overcharging then they are ruined. Being sealed, they are good for inaccessible places or interior spaces, in addition some can be mounted on their side or upside down.
3. Lithium Ion: I'm not going to spend much time here, but in the next 10 years these will be the way to go as they are light and take almost any charge profile BUT They can melt, catch fire and burn your boat to the waterline. No realy choices for boats unless you want to spend $10K+

6. We can't control this much but batteries love room temperature, dry places, and don't like vibration... sound like your boat? Really though, it is something to keep in mind.

With all this being said, if you want the longest life, buy a great charger, super premium batteries (at least premium), and make sure you don't discharge them too fast or past the discharge rate.

I'm sure I have left something out, but as you can see I am fairly passionate about batteries because I hate seeing people struggle every 2 years with this, then go to the closest autozone and wonder why in 24 months they have to do this again.

For reference, with the Rolls Surrette's, a Promariner charger many boats in our area will keep these batteries for 10+ years and I know of one who replaced his at 14years.
 
So are you saying we should preemptively replace our batteries every third season? Or is there a "go/no go gauge" of sorts?

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i have the charger that was installed from the factory so i do not know the recharge rate or any settings...
 
Importmonkey, I am saying you shouldn't have to replace your batteries for many more years but you have to make some decisions when you buy batteries and a charger.

Gasman: what is the make and model number on your charger, I'll look up the manufacturer and give you the information.


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If you do not use the charger for your engine batteries
and IF you fully charged them at layup, they should be able to start your motors in the spring.
. If not there bad
If your engine charging systems are up to the task, you do not need to keep a charger on them when not in use TO START THE ENGINES. Keeping it on a charger all the time prevents that last start from showing up as a bad or weak battery.
Just keep your house batteries on charge, you dont care if they go dead.
 
Agree with Notherdecision. To balance that a bit, Deka and Interstate make good wet cell batteries. I have been boating for 25 years now, and I typically get 5-7 years out of those batteries using a run of the mill charger in the various boats. I have never had one fail, I replace for peace of mind in that window. So for $100 a battery, I think the cost per season is very reasonable. I do keep them charged all season, and stored indoors fully charged before layup for winter.
Could I get another few years out of them, probably, but I stagger the replacement so I only replace one at a time.
 
paulswagelock said:
Agree with Notherdecision. To balance that a bit, Deka and Interstate make good wet cell batteries. I have been boating for 25 years now, and I typically get 5-7 years out of those batteries using a run of the mill charger in the various boats. I have never had one fail, I replace for peace of mind in that window. So for $100 a battery, I think the cost per season is very reasonable. I do keep them charged all season, and stored indoors fully charged before layup for winter.
Could I get another few years out of them, probably, but I stagger the replacement so I only replace one at a time.
Click to expand...

Ditto on Interstate, they are not the super-premium type of battery, but their Marine AGM was a nice balance of price/performance when I was replacing all 4 batteries on my 340DA. When I bought it a couple years ago, it had 3 different style batteries, all wet cells, group 27's. I decided to start off with a set of new Group 31's for extra capacity, and went with AGM's to reduce maintenance a bit in the tight confines between the 8.1's in that engine room. I was able to set the charger to the AGM setting. It's been nice to spend the night out with both fridges, stereo, lights, etc running and not worry about problems the next morning. When it's really hot, and the admiral wants A/C, well, that genny is running, but mostly we like the quiet nights.
http://www.interstatebatteries.com/m/product/agm/marine-agm
 
I have (5) Interstate 27M-XHD batteries on my 2010 350. I'm about to replace them for the first time.
http://www.interstatebatteries.com/...0&Title=Pure+Lead+27MXHD+replacement++battery

I tend to run my generator when we're out on the hook for the day 5-6 hours at a time, mainly to keep the AC running. My battery charger is always on at the dock. I don't leave my batteries on when I leave the boat, but my charger is always on when I'm on shore power.

I thought about replacing them last spring, but after testing them, determined they were still performing as required.

I just priced them with my local Interstate shop and they're $125/ea when I turn in my current batteries.
 
Interstate and Deka are both good quality brands. Being there are so many options I would just advise you to check the number of cycles and the depth of discharge they can accept. If you are not using a deep cycle then it will severely reduce the life when you discharge it to say 20%. If you are using a deep cycle then just make sure you have an abundance of cranking amps if you are using it to start your engines. The gas boats will find this much easier then a diesel boat.


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My last batteries lasted 6 seasons. The key for me is not draining them dead, keeping them charged and I do run the generator on the hook and charge them. I also top them off with distilled water.
 
Last edited:
Thanks just went down to my boat to get the charger spec it's a pro-tech 4 charger...advanced 4 step battery charger
 
I have a 1 deka deep cycle marine batter, 1 interstate marine deep cycle battery, and 1 Napa deep cycle battery
 
Gasman said:
I have a 1 deka deep cycle marine batter, 1 interstate marine deep cycle battery, and 1 Napa deep cycle battery
Click to expand...
Are any of these tied directly to an engine (or both?) for starting only? If yes, it may be worthwhile to consider replacing that battery with a starting or combination battery instead of deep cycle for better performance and longevity.

We have a 3 battery setup: 1 starting battery for the port engine (on its own switch) and 2 combination batteries (on a second switch) for the starboard engine/house. The port battery never gets involved in running the stereo, fridge, etc. If needed--like if we draw down the 2 battery bank too far to crank the starboard engine--we can tie the starboard engine over to the port battery with the dash switch; we like having this insurance. (If our genny was functional, THAT would be our mitigation against draw down, but we do the best we can!)

Doesn't answer your question about brands, but hope it helps with your overall power management plan.
 
The pro tech 4 is a known issue within itself. You can google for all the details but simply put it doesn't recognize different charge states of different banks. This means it is constantly overcharging or most likely undercharging the batteries.

You will need to upgrade the charger for the best performance when you replace batteries.

The newer pronautic 1250 would be a good choice but you may need to upgrade the wiring from the battery charger to the batteries to stay in compliance. The 1250 is a dedicated independent 3 bank charger so it can make a huge difference. Frankly, you may be surprised in the capacity of what you have just by upgrading the charger because it will charge each bank to the full capacity.

Can you clarify what each battery you mentioned is for?


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For what it's worth Batteries Plus is still running a 10% off deal if you order online, pickup in store. Their Duracell batteries seem like a pretty solid deal at sub $100 each.
 
Every 2 years I replace 2 of my four... So, it is every four year on a pair... I like to have two newer, so they don't all go at once.
 
If you will follow my advice you should be able to get to 7 years fairly regularly.

Josh
 
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