AGM starting battery?

[gim]

I may need to replace my cranking/starting battery before May.  I recently bought a pair of AGM deep cycles last November on Black Friday for my bow mount.  Can I replace my traditional lead acid cranking battery with an AGM too?  I'm having some trouble finding a size 27 AGM cranking battery.  They all seem to say deep cycle which is not for starting an outboard.

 

Thanks

[MickD]

Cabelas/BPS has one on sale now that says starting/deep cycle.  Not sure of the size.  But I have one that is 7 years old and still going strong (starting battery).

[gim]

56 minutes ago, MickD said:

Cabelas/BPS has one on sale now that says starting/deep cycle. 

That's odd.  How can it be both starting and deep cycle?  I thought it was either starting/cranking/dual purpose OR deep cycle.

[MickD]

13 hours ago, gimruis said:

That's odd.  How can it be both starting and deep cycle?  I thought it was either starting/cranking/dual purpose OR deep cycle.

I don't know, just telling you what the advertisement says.  But starting/cranking is the same thing as dual purpose.  And "dual purpose" is most likely starting/deep cycle.  You have "dual purpose" linked with starting/cranking.   Check the ad. It states it will do both, and they have a size 27.  I'm not advocating this as the best solution, but just trying to point out an option.  

[TnRiver46]

56 minutes ago, gimruis said:

That's odd.  How can it be both starting and deep cycle?  I thought it was either starting/cranking/dual purpose OR deep cycle.

Dual purpose means starting and deep cycle, works for either.  I’ve had one or two over the years and they did fine. They are/were pretty common on the shelves of auto parts stores.  Not AGM tho 

 

to the original question yes people use AGM for cranking, not sure why you can’t find one tho. I haven’t shopped for batteries in a while but I might look around out of curiosity, gives me an excuse to walk thru academy 😂 

[gim]

52 minutes ago, TnRiver46 said:

Dual purpose means starting and deep cycle, works for either.  I’ve had one or two over the years and they did fine. They are/were pretty common on the shelves of auto parts stores.  Not AGM tho 

 

to the original question yes people use AGM for cranking, not sure why you can’t find one tho.

You're right I did kind of misword my original question.  Dual purpose means exactly what it says, deep cycle or cranking/starting.

 

I really can't find a specific battery in size 27 that is a cranking AGM though.  At least not locally I can't.  Wouldn't be the end of the world if I had to use another standard lead acid version.  I've had the current one for 3 whole seasons so maybe it's just time to replace it.  I replaced my deep cycles for my bow mount with AGMs in November and I'd like to do the same with my cranking one if possible.

[A-Jay]

27 minutes ago, gimruis said:

You're right I did kind of misword my original question.  Dual purpose means exactly what it says, deep cycle or cranking/starting.

 

I really can't find a specific battery in size 27 that is a cranking AGM though.  At least not locally I can't.  Wouldn't be the end of the world if I had to use another standard lead acid version.  I've had the current one for 3 whole seasons so maybe it's just time to replace it.  I replaced my deep cycles for my bow mount with AGMs in November and I'd like to do the same with my cranking one if possible.

If your cranking battery also runs your accessories (nav lights, live wells, vibrating seat massager) & any electronics, a dual purpose battery is not a bad idea. 

I use a 31M Blue top Optima.

They make a 27 too. 

https://www.optimabatteries.com/products/bluetop-d27m

Auto Zone & Advanced Auto Parts usually have them.

A-Jay

[airshot]

According to our local battery mfgr shop, the dual purpose battery was originally designed for motor homes where both cranking and long slow draws were needed.  They work quite well, I had them in my MH.  However, they are not quite as good as a straight deep cycle for long slow draw downs.  They designed an in between type battery that does both jobs but not as well as a stand alone deep cycle or cranking.    According to them if your engine is hard to start then don't use them but if it starts easy they are great.   Take it for what it is worth.....

[Junger]

I had a bluetop dual purpose in my old 14' Bomber and it worked well for cranking and my graphs. Optima's are quality batteries, so they're pricey. That being said, the price of LiFePO4 batteries have almost come down to the price of high quality AGMs.

 

Ionic has a 1100CCA 40AH group 25 starter battery for $500. https://lithiumhub.com/product/lithium-12v-1400ca-lifepo4-marine-starter-battery/

[MickD]

1 hour ago, Junger said:

Ionic has a 1100CCA 40AH group 25 starter battery for $500. 

Very close to making sense if they last as long as they say.  At my age, just might be my last battery.

[gim]

Thanks for the advice.  I cannot use a lithium because my chargers are not compatible.

 

I could not find an AGM cranking battery locally in the right size today.  I bought a standard lead acid one and installed it today.  Batteries Plus was having a 17% off sale for St Patricks Day and I also got a $24 core return which helped defray the cost.

[Bankc]

The difference between a starting battery and a deep cycle battery is that a starting battery has lots of thin plates.  Because the plates are thinner, they can pack more of them into the same space.  And because there are more of them, there's more surface area, which means they can draw more electrons out of the acid at once.  So you get more cranking amps, since amps. 

 

A deep cycle has thicker plates.  And since it has thicker plates, you can't put as many of them into the same space, which means less available electrons and amps.  What you get in return are the thicker plates that are more durable and won't be damaged with light corrosion.  And when you drain a battery, you basically corrode it.  The way a battery works is there are two different types of metals and an acid between them, and the acid causes one metal to corrode and stick to the other, bringing with it, electrons.  And then when you charge it, you basically reverse the corrosion.  That's over simplified, but you get the basic idea.  So thicker plates can go through the process more often before they become damaged beyond repair.  

A starting/cranking, dual purpose battery basically splits the difference with the plate thickness.  They won't hand deep discharges as well as a true deep cycle.  And they won't provide as many amps as a true starting battery.  But if you don't need all of those amps at once to start your engine, and you don't need all of that capacity in between chargings, then they're a good choice. 

 

You did fine with the standard lead acid battery for the starting battery.  Starting batteries aren't put under the same stress as trolling motor batteries, so they should last about as long and work about as well as an AGM.  They just require a bit of maintenance (occasionally checking water levels) and can't but put on their sides like AGM.   

[gim]

10 minutes ago, Bankc said:

They just require a bit of maintenance (occasionally checking water levels) and can't but put on their sides like AGM.   

 

That was the selling point for me.  I'm not putting it on its side but I do like the idea of maintenance-free.

[Capt Ed]

Batteries Plus carries X2 dual purpose batteries in group 24, 27, and 31 sizes.  I bought this *** years ago and other than the high price I paid, it's been great in every respect.  https://www.batteriesplus.com/productdetails/battery/marine-and-boat/dual-purpose-(starting_cycling)/sli27agmdpm  It has plenty of cranking amps and a lot of amp hours to run my electronics, livewell pumps, and other accessories.  Warranty is 4 years, if it fails anytime within the 4 years, they replace it free.  

 

Odyssey Batteries also makes an excellent dual purpose.  Warranty is 3 years with no pro rata.  https://www.westmarine.com/odyssey-group-27-dual-purpose-agm-battery-92-amp-hours-20084562.html?&utm_medium=cpc&utm_source=google&utm_campaign=[ADL][PLA] All Categories_Test&utm_content=autoag0000x21019836630x20084562&gad_source=1&gclid=CjwKCAjwwr6wBhBcEiwAfMEQs5UWQmNvgGeIPJbRs2rNU2j0ig2TOLLT-uacn_Mu7l4mHFsjbI4IuRoCpCUQAvD_BwE

 

A more budget friendly choice is a Duracell Ultra dual purpose:  https://www.batteriesplus.com/productdetails/battery/marine-and-boat/sli27magmdc  It has a 30 month free replacement warranty.  At 900 cranking amps and 620 cold cranking amps which should be ok with many engines.  

 

AGM batteries have many advantages over flooded cell batteries but for me, not having to check the water is the main reason I made the switch.

 

 

 

 

[gim]

@Capt Ed I bought a pair of the third ones you listed (Duracell) last November on Black Friday when they were having a 20% off sale.  They are my deep cycle bow mount batteries now.

 

My understanding is that deep cycle batteries should not be used as a cranking/starting battery.  I looked for one there specifically labeled as a cranking/starting battery in AGM and I could not find one.  So I ended up buying another lead acid Duracell version in size 27.

 

My first outing will be tomorrow using all 3 of these batteries.  The AGM ones have a 30 month warranty and the starting battery has a 12 month warranty.  The lead acid one has 800 cold cranking amps to start the outboard and run the graphs, lights, pumps, etc.