Group 27 or 31?

A

aroos

Active member
Joined
Aug 29, 2013
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37
Fluid Motion Model
C-24 C
Non-Fluid Motion Model
Cutwater 30
My apologies for double posting but I need an answer quickly. We gave a 2014 Cutwater 30 sedan. I need a new starting battery. Is it Group 27 or 31? Thanks for your help.
 
Our 2014 R27 uses group 31. Not sure about the C30 but I would assume the same.

Curt
 
the volvo D4 260 uses group 31. you need high marine cold cranking amps for these engines.

seperately but related I also think the standard factory installed AGM's are at their CCA limit at 90% wear in cold conditions.

not sure if you are AGM or wet cell. but with the chargers and wiring installed you need to keep the chemistry the same across all batteries. i.e use the same battery as your house and thruster.
 
If you have AGM batteries they're a group 31.
 
I've been considering replacing the original equipment group 31 AGM batteries with group 27 AGM batteries on my 2011 R27. The group start battery will match the CCA requirements for the 4BY2-180 Yanmar, and I'll lose about 30 amp hours across the two deep cycle house batteries and the thruster battery (10 ah ea), but I'll take about 62 pounds of weight out of the port corner of the stern. Maybe bring the stern corner (and exhaust) about a half inch (?) higher out of the water. I seem to remember from a separate post on this forum that Knotflying uses group 27 flooded lead acid batteries on his R27. Since I currently don't spend more than two weeks out of the year on the hook, maintaining the charge levels is not a problem and the lower amp hour totals aren't a concern, since I also have the generator and solar panel. Any feedback is welcome.
 
Trisailor":1di91cud said:
I've been considering replacing the original equipment group 31 AGM batteries with group 27 AGM batteries on my 2011 R27. The group start battery will match the CCA requirements for the 4BY2-180 Yanmar, and I'll lose about 30 amp hours across the two deep cycle house batteries and the thruster battery (10 ah ea), but I'll take about 62 pounds of weight out of the port corner of the stern. Maybe bring the stern corner (and exhaust) about a half inch (?) higher out of the water. I seem to remember from a separate post on this forum that Knotflying uses group 27 flooded lead acid batteries on his R27. Since I currently don't spend more than two weeks out of the year on the hook, maintaining the charge levels is not a problem and the lower amp hour totals aren't a concern, since I also have the generator and solar panel. Any feedback is welcome.
Click to expand...





I agree with you on the weight differences. It does make a difference. My C26 came with flooded lead acid maintenance free batteries (Centennial) all group 27. Weight of cranking battery 49lbs (1), weight of deep cycle 44lbs (3) total weight 181 lbs. I had 3 full seasons of use with theses batteries when the two house batteries failed. I have always preferred flooded lead acid maintenance free batteries. I needed to replace my house batteries this year. After researching batteries, I was leaning toward purchasing Deka flooded lead acid batteries (adding 10lbs more weight total 4 batteries) then the originally installed Centennial batteries. Total weight with Deka 191lbs

I changed my mind and switched to AGM. Main reason, advertised quicker recharge time and advertised over 900 cycles of 50% discharge. I use an inverter a lot and discharge the house batteries to 50% and even lower then that at times. I purchased Northstar AGM. The only concern I had was the weight. I was told that fluid motion uses group 31 if AGM batteries are installed. When I saw the weight I was amazed 75 lbs each group 31. I then looked at group 27 68 lbs each. Installing 4 group 31 added 119lbs (total weight 300 lbs)to the aft section of the boat and Group 27 added 92lbs ( total weight 272 LBS) to aft section of the boat. I chose group 27. When I launched the boat I could see the difference in the way the boat floats. The AGM's added benefits come with a cost, twice the price of flooded maintenance free and a slight performance loss to the boat because of the added weight to the stern. I believe the Northstar batteries will live up to their reputation but the battery weight increase to a weight sensitive boat makes me second guess my decision.
 
Hi Brian,
Thanks for the input. You've confirmed my thought process. I plan on keeping with the AGM's. We have a local place here that deals in Crown batteries that have a reasonable price, compared to West marine Deka batteries. I am tempted by the maintenance free flooded lead acid, but will probably stick with the AGM's, due to the better discharge forgiveness of them. weight is the same reason I took that blasted dinghy off the swim step. Not to mention that it also acted like a big bucket and wind catcher. Removing it brought the stern (and exhaust port) 2 inches up out of the water.
Again thanks for the input.
v/r Brian
 
I recently had to replace my factory AGM batteries. Went with Optima D31 and D34 AGM's, similar performance but a lighter weight, but a bit more money.... So far so good, port stern is a little more balanced.
 
Thanks all. I'm going to go with the group 27 AGM's. As I was upside down, doing the boat yoga, installing a galvanic isolator and performing some clean up of cable runs, I was also reminded that the smaller footprint of the group 27's along with less weight would be a good thing.
 
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