Battery life: Lead acid vs. AGM?

[FryDog62]

So if a lead acid trolling motor battery is estimated to last approx 5 years (with normal use/maintenance) then an AGM starting battery should last approximately how long?? 

[MN Fisher]

Ummm...Chris - AGM is lead-acid...just a different method of containing the electrolyte (acid)...held in a glass mat instead of being allowed to 'slosh' around.

[FryDog62]

Yes, but does it last longer, if so how much..?

[MN Fisher]

No idea - tell ya what...I'm putting a small AGM in the F-9 as my starting battery (and only as the starting battery) for the 25hp.

 

Come back to me a in few years and I'll let you know.

 

(actually, I'd like to know this too.)

[gim]

There's plenty of members on this forum that have used AGM batteries.  I'm sure they'll chime in with their personal experience.  My understanding is that they cost approximately twice as much as a standard lead-acid battery, but they do not last twice as long.  Lithium batteries cost more than twice as much, but I think they are supposed to last 10 years.

 

I can't justify paying twice as much for something unless I'm going to get something that lasts twice as long.  I think the real benefit of a lithium battery is the weight.

[A-Jay]

52 minutes ago, FryDog62 said:

So if a lead acid trolling motor battery is estimated to last approx 5 years (with normal use/maintenance) then an AGM starting battery should last approximately how long?? 

I say the same.

But I don't have to mess with it all for 5 Years.

So normal mainainance for the AGM is pretty much nothing.

Big Fan of that.

There's plenty of deals in my life now that are NOT in that category.

I'll pay the extra $$$ just for that.

More time fishing.

A-Jay

[FryDog62]

So when I purchased the boat 5 years ago, it came with the standard group 27 trolling motor batteries. The dealer talked me into the more expensive AGM starting battery - in part because of the no maintenance advantage, but also because it lasts longer. But I can’t remember if he said it was significant longer life.  
 

I just replaced all 3 TM batteries this morning, but the AGM/starter battery still indicates a strong charge.  I’d prefer not to buy another battery this year but don’t want to go dead on the water either.  In the meantime, I’ll keep checking the AGM battery every time before I go out... 

[Deephaven]

Have to say that although I am super good at maintaining nearly everything I own there is no way in h#ll that I am going to pull the batteries in my boat to check their water level.  I am sure they will die more quickly because of it, but it is a monstrous job.  When they do die I will grab a lithium.  In my other boats the AGM & normal lead acid have lasted about the same time.  This tells me that either checking the fluid level isn't that big of a deal or that neither technology is really meant to last.  The biggest key I've found is making sure they spend as much time at the fully charged state versus worn down.

I would run what you have and instead of another battery just buy a cheap jump box or bring a set of jumper cables.  I carry one of these and it has started many a boat. https://www.amazon.com/gp/product/B07H58NP77/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

[FryDog62]

27 minutes ago, Deephaven said:

Have to say that although I am super good at maintaining nearly everything I own there is no way in h#ll that I am going to pull the batteries in my boat to check their water level.  I am sure they will die more quickly because of it, but it is a monstrous job.  When they do die I will grab a lithium.  In my other boats the AGM & normal lead acid have lasted about the same time.  This tells me that either checking the fluid level isn't that big of a deal or that neither technology is really meant to last.  The biggest key I've found is making sure they spend as much time at the fully charged state versus worn down.

I would run what you have and instead of another battery just buy a cheap jump box or bring a set of jumper cables.  I carry one of these and it has started many a boat. https://www.amazon.com/gp/product/B07H58NP77/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

Agreed... I have the battery tester and a charge ready to go. If I get another 1-2 years out of the AGM, may switch to Lithium then. All depends on how long you want to keep your vessel too. If you sell in 3 years then I would opt for another AGM most likely. 

[Woody B]

For automotive applications (I'm an auto tech) AGM's usually don't last......as long as they should.   AGM batteries are more sensitive to heat.  This is one of the reasons many autos have the batteries in the truck or under a seat instead of under the hood.  The AGM's under the hood usually have some kind of insulation around them.   However, for boating applications AGM batteries are tougher......less likely to be damaged by vibration.   Sometimes batteries last a long time. Sometimes they don't.  It's always been that way but seems even more so today.  

 

 

I went to lithium for my trolling motor.  

[Bird]

I've been slowly migrating to lithium as lead acid batteries expire.

I'm a supporter of technology advancement, why not ? Oh and the significant weight savings.

But must admit, although heavy, my lead acid batteries never required but minimal maintenance, add water above the plates once per year.

To my understanding, AGM batteries can be oriented in any position without comphromise to performance but why install one upside down? Lol

 

At the end of the day, I'd say lithium would be cost effective with the benefits it provides....... longevity, lethargic charge intervals and weight savings.

[MN Fisher]

4 minutes ago, Bird said:

To my understanding, AGM batteries can be oriented in any position without comphromise to performance but why install one upside down? Lol

Any orientation except upside-down. There's a pressure relief valve on the top...can't have that on the 'bottom'.

[Bird]

1 minute ago, MN Fisher said:

Any orientation except upside-down. There's a pressure relief valve on the top...can't have that on the 'bottom'.

You sir seem to be the battery guru on this site, much appreciated ?

[A-Jay]

16 minutes ago, Bird said:

I've been slowly migrating to lithium as lead acid batteries expire.

I'm a supporter of technology advancement, why not ? Oh and the significant weight savings.

But must admit, although heavy, my lead acid batteries never required but minimal maintenance, add water above the plates once per year.

To my understanding, AGM batteries can be oriented in any position without comphromise to performance but why install one upside down? Lol

 

At the end of the day, I'd say lithium would be cost effective with the benefits it provides....... longevity, lethargic charge intervals and weight savings.

My three 31M trolling motor batteries are under the rod locker, which is usually full of rods.

While I LOVE and prefer that battery location (centerline and low in the boat)

it makes 'servicing' them fairly inconvenient.

Enter AGM.

Thank you.

Just replaced mine when I pulled the boat for hard water (Nov 2021)

They were operating OK (with a bit of juice reduction)

but after 6 years - it was time.

I've been know to run in some sloppy conditions,

so having batteries that are very resistant to vibrations and leak proof,

adds peace of mind. 

A-Jay

[MN Fisher]

6 minutes ago, Bird said:

You sir seem to be the battery guru on this site, much appreciated ?

Na - I just read labels and instructions....my AGM's specifically state "Do not install upside down". I've seen that on others too.

[FryDog62]

24 minutes ago, Bird said:

I've been slowly migrating to lithium as lead acid batteries expire.

Curious how you’re doing this ... assuming you have more than one trolling motor battery?  Do the Lithium and lead acid batteries work together, do you have them in a series or parallel, different or the same on- bank charger, etc?

[MN Fisher]

Just now, FryDog62 said:

Curious how you’re doing this ... assuming you have more than one trolling motor battery?  Do the Lithium and lead acid batteries work together, do you have them in a series or parallel, different or the same on- bank charger, etc?

Sorry, Chris - you can't mix lead-acid and Lithiums in the same bank. The discharge properties are different and charging is completely different.

A charger that'd work on a Lithium won't properly charge a lead-acid, and a charger for lead-acid would scramble the control circuit of a lithium rendering the battery useless...and void the warranty.

[Bird]

2 minutes ago, FryDog62 said:

Curious how you’re doing this ... assuming you have more than one trolling motor battery?  Do the Lithium and lead acid batteries work together, do you have them in a series or parallel, different or the same on- bank charger, etc?

Should have elaborated, my bad.

Single battery operation, but have went to dedicated fish finder battery " lithium" and RV tounge mount " lithium " .

If I were to tie two 12 volts together to make a 24, they'd be of the same gender, type.

 

 

 

[FryDog62]

4 minutes ago, Bird said:

Should have elaborated, my bad.

Single battery operation, but have went to dedicated fish finder battery " lithium" and RV tounge mount " lithium " .

If I were to tie two 12 volts together to make a 24, they'd be of the same gender, type.

 

 

 

Yes that makes sense, thx

[WRB]

A marine cranking battery for 25 hp OB that starts easily (maintained, fresh plugs etc) doesn’t require a lot of reserve power, size gr 24 should work. How long depends on how often you use the battery.

I had 3 AGM’s in my last bass boat for over 10 years when I sold it. My boats were always garaged in ambient temperature, no hotter then 80 or colder then 50 degrees.

Very cold freezing temps and hot over 100 degrees is hard on the batter cases for example. Keeping the battery fully charged helps it’s life.

If the cranking battery is running sonar, anchor system, lights at night etc, go with a larger size.

Tom

[Big Hands]

On 6/6/2022 at 3:32 PM, Bird said:

To my understanding, AGM batteries can be oriented in any position without comphromise to performance but why install one upside down? Lol

IIRC, it is the gel cell batteries that can be mounted in all sorts of positions. AGM batteries are not gel cell batteries.

[MN Fisher]

13 minutes ago, Big Hands said:

IIRC, it is the gel cell batteries that can be mounted in all sorts of positions. AGM batteries are not gel cell batteries.

Gels and AGMs can be mounted in any orientation EXCEPT upside-down. Since the electrolyte is 'contained' in both, there's no leakage concerns...unlike a wet-cell where the fluid just sloshes around.

[NHBull]

I have 2 friends that went with automotive lead acids and both didn’t last 18 months.  The vibration killed them.  I have had AGM’s last 7+ years

[Way2slow]

Battery longevity is rated in cycle counts (a discharge and recharge is one cycle).  AGM's typically have a higher cycle count than flooded cell batteries, usually about 15% to 20%.  How deeply the battery is discharged also have a huge affect on cycle count.  A battery that is only discharge to 70% will last much longer (almost twice as long) than a battery that is discharged to 30%  How a battery is maintained also has a huge affect on the life of a battery, and the type battery charger used.  A good logic controlled charger can almost pay for itself with just the first set of batteries.  Then you have the battery construction itself, and the type alloy used to make the plates and how much lead they actually have in them.

There is a whole host of variables that have to do with the life span of a battery.  That's why you buy a good, well known brand name, a good, name brand logic controlled charger that's made in the USA and learn how to properly maintain them.  

Now, as far as run time for each trip, a good, flooded cell battery that has service caps on it has more reserve minute's and will give more run time than the equivalent size AGM.  

[TnRiver46]

On 6/18/2022 at 7:36 AM, NHBull said:

I have 2 friends that went with automotive lead acids and both didn’t last 18 months.  The vibration killed them.  I have had AGM’s last 7+ years

Clearly they’ve never driven an auto on interstate 59 in Alabama