Another Battery Inquiry

dlochner · Oct 26, 2021

The price difference between a Group 24 and 27 is small, so as long as there is room for 2 Group 27s then go for them.

You will be better off with "deep cycle" batteries than "start" batteries. Take a look at this site and search for the article on Deep Cycle batteries, also read the opening message from Rod's brother. www.marinehowto.com.

Two important considerations, it is not necessary to use a "start" battery to start our small marine diesels, a "deep" cycle battery will do just fine. Second, the less a battery as a percentage of its capacity is discharged and the more often it is returned to 100% charge the longer it will last. Thus, if you draw 10 amphours of power out of a 80 ah battery it will be less damaging to the battery than taking 10ah out of a 70ah battery.

There are many sources for marine batteries, some better than others. I prefer batteries made by East Penn, they are well made batteries with a good reputation, sold under the Deka brand and other house brands including NAPA and Worst Marine. No need to pay a premium to buy the same battery with a different label from a marine store.

FastOlson · Oct 26, 2021

Our boat came with an original M25XP. It would start on either our "emergency" 12 volt battery or our house bank consisting of two Trojan GC batteries. We got 9 years out of the last set of GC batteries, and hope to do as well with the current set. These are Trojan T-125+ batteries, and we run the whole boat on them, lighting, nav and radar system, fridge, and the furnace.
IMHO, it's worth some time and effort to install a set of decent house bank batteries.

I should add that our 'stock' configuration was a pair of group 24 12-volt batteries, with a 1-2-all switch.

jssailem · Oct 26, 2021

FastOlson said:
it's worth some time and effort to install a set of decent house bank batteries.

I agree

Why I sought out Dyno Batteries in Seattle. Selected 3 of 12volt 30 TMX Batteries-deep cycle 135AmHr capacity for my house.
So far 5-6 years old showing 88% capacity on new.

JohnShannon · Oct 26, 2021

AGM's are really fussy in my experience. It seems they are much more sensitive to being in an over discharged condition than a regular lead acid is.

Davidasailor26 · Oct 26, 2021

JohnShannon said:
AGM's are really fussy in my experience. It seems they are much more sensitive to being in an over discharged condition than a regular lead acid is.

They’re definitely more sensitive to sitting discharged. For the OP on a charger full-time except for day sails that’s probably not a big deal, but if AGM’s are not in the budget it’s not a big problem.

dLj · Oct 26, 2021

As a day sailor with the sailing schedule you've described, I'd recommend flooded lead acid deep cycle batteries. No need to go to AGM's. @dlochner 's recommendation seems spot on to me...

That's my 2 cents worth...

dj

Ward H · Oct 26, 2021

rpell1@msn.com said:
Should I buy two group 27 deep cycle or one group 27 deep cycle and one group 24 starter ( or combo) battery?

What @dlochner said.

Tally Ho · Oct 26, 2021

I replaced my 2 age ing group 27’s with 2) 6-volt golf cart batteries from Sam’s Club. These give me 215 Ah capacity at 12 volts.

i really like them.

I am still thinking about a start battery, but felt comfortable enough to go out on a 2-night, 3-day sail without a backup.

i installed this $80 battery monitor to keep an eye on the batteries..

Your needs are pretty light. You should be fine without a start battery, as long as you are charging up every day or 2.

I have fridge ( but did not run it on my 3-day sail). I have no solar or generator.

Greg

Scott T-Bird · Oct 27, 2021

If you have the room, I recommend that you purchase 2 Grp 27 lead acid batts to make a better house bank. Also purchase 1 Grp 27 or Grp 24 for your auxiliary (back-up). I'd put a fridge in your boat so you might want more ah in the house bank.

jeepbluetj · Oct 27, 2021

AGMs are usually not worth it for most sailors. On my C-30 I had a pair of GC-2s under the chart table, and put a G24 'start' battery under the starboard settee as battery "1". Used it maybe twice. Almost always started from the GC-2s. If I was doing it again I'd likely just have a lithium jump-starter instead of the G24

GC-2s are the best bang for the buck out there if you have room and will water em every quarter or so. Actual golf courses beat the absolute crap out of carts and batteries. You don't see them using AGMs.

Stu Jackson · Oct 27, 2021

Here's the issues with AGMs:

AGM Batteries - Making The Choice (from Maine Sail)

AGM Batteries - Making The Choice

AGM Battery Issues and the Blue Seas Dual Circuit Switch (from Maine Sail) "DARN AGM Batteries"
Darn AGM Batteries

Additional Observations on the Limits of AGMs Electrical Systems 101

DArcy · Oct 28, 2021

jeepbluetj said:
GC-2s are the best bang for the buck out there

^this is what I found as well

I researched different battery types a couple years ago before replacing mine. I had 2x group 31 for the house and 1x group 31 for the starter. From what I found, looking at performance curves and Mainsail's site plus various other reviews was that the advantage to AGM batteries is they an be charged much quicker. Since my main source of charging is from solar and a 30A shore charger paying more for AGM is a complete waste of money. The only place where AGM are worth the extra cost is for quick charging on either a generator or high output alternator, or where access is limited or you just don't want to check water levels regularly.

Mainsail convinced me that smaller (group 24, 27) "Deep Cycle" batteries are not truly deep cycle and they just won't last as long as gulf cart batteries. I ended up going with GC2 batteries for house and a group 31 for starter, although I could probably get away with smaller for the starter I like the extra capacity "just in case".

I would suggest for day sailing, lite load use just get the biggest deep cycle flooded cell batteries you can fit. If you only have room for 2 batteries then group 27 would work so you have a back up. If you are going to run on "Both" all the time then just get flooded GC2 batteries as you will have much better capacity and longevity.

jeepbluetj · Oct 28, 2021

DArcy said:
... From what I found, looking at performance curves and Mainsail's site plus various other reviews was that the advantage to AGM batteries is they an be charged much quicker. ...

I agree. If'n one digs through the links Stu provided the advantage of AGMs for charge rate pretty much stop at the end of bulk. Absorb and float are approximately equal to FLA. And most boaters spend a lot of time in absorb/float.

AGMs really get killed with partial state of charge charging - i.e. not getting to 100% after a discharge. Cruising sailors/daysailors often are forced into PSOC charge regimes: if relying only on engine or generator, nobody is going to continue to run either for 5 extra hours to get well into float. If relying on solar or wind - cloudy/calm days happen.

AGMs are great if one needs a non-spillable/maint free battery OR the ruggedness some AGMs provide. (i.e. Optima is the right battery for an off-road vehicle because the vibrations will kill cheap FLAs)

But for the price difference one could ruin 3 FLAs for every 1 AGM. Hurts a lot less when you kill a $100 battery than when you kill a $300 battery when the fridge is on and the marina guy unplugs your shorepower.

Another Battery Inquiry

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SBO Weather and Forecasting Forum Jim & John

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