270 batteries and shore power

rasbury

Have out our boat in a slip and want to replace the batteries. But that means it's in the water with no power for the pumps. Now I should be able to swap out but if something goes wrong with the plan..not that this would ever happen..anyway, does that run on shore power also? Seems like when I had the motor out, I was able to run the hatch off shore...lights and stuff I think? Also, with the batteries out and shore power on, are those terminals "hot"?

And not to re hash the battery type question, the last batteries I think I bought at auto zone and that was some time ago. 

Aqua_Aura

Buy the new batteries then take your old ones back for the core charge. The charger is powered from the shore power which would still get power to the 12V systems?

I just did two 6V batteries this time when I changed out the single house battery. Might be worth it especially if you don't have a generator. I have a generator but like to use the batteries over listening to it run. 

I can't completely remember when I had mine out but I think the 12V systems still had power. 

LaRea

It depends on how your charger is hooked up.  You could disconnect the batteries and flip the float switch to see if the pumps still run.  

Safest bet:  bring new batteries to the boat, and swap them one at a time.  Then take the old ones back to the store for the core refund.  That way, you'll only be disconnected for a few minutes at most. 

Willhound

Yep, what LaRea says. And get your wrenches and stuff ready ahead of time, but most importantly, take pictures of all the connections and/or mark the cables with tape. Do both. Sounds silly, but it's incredibly easy to get mixed up when you're crammed into the tiny space under a 270 hatch. After 4 seasons of pulling batteries in fall and replacing in spring I still managed to miss a cable last time around. The pic I had saved my butt.
Also, get a cable/battery cleaning brush and give the cable ends a good going over, and when you get the new batteries get a small tube of di-electric grease and coat the posts well.

rasbury

I think when I had no nattery in, shore power on 12v worked but seems like I figured the leads were hot because the charger had to be in to run 12v. I will get the batteries and then go back for the core refund...so what min CCA for the starter battery, 350 mpi and I only have the one house battery which should be a deep cycle but really don't know for sure what to get there, how those are rated...

YYZRC

Group 31 for house and Group 27 for starting. Just my opinion. 

raybo3

Willhound said:

Yep, what LaRea says. And get your wrenches and stuff ready ahead of time, but most importantly, take pictures of all the connections and/or mark the cables with tape. Do both. Sounds silly, but it's incredibly easy to get mixed up when you're crammed into the tiny space under a 270 hatch. After 4 seasons of pulling batteries in fall and replacing in spring I still managed to miss a cable last time around. The pic I had saved my butt.
Also, get a cable/battery cleaning brush and give the cable ends a good going over, and when you get the new batteries get a small tube of di-electric grease and coat the posts well.

Totally wrong. Do not coat the posts with di-electric grease. Di-electric grease is non conductive. Make a good connection then cover it with di-electric grease. That will keep it clean and dry. 

Willhound

Guess I just learned something. I was always told the opposite. Is there something else I'm thinking of?

Aqua_Aura

This had a big discussion over the Summer and I think we all assumed di-electric grease didn't hinder electric flow. It's more for a protective coating over the connection but not in between a connection if that makes sense. 

rasbury

interesting! Maybe if I get all the grease off my batteries would work!

Dream_Inn

rasbury said:

interesting! Maybe if I get all the grease off my batteries would work!

Worth a try!  I will say, I don't put anything on mine.  Once a year I remove the connections and clean.  

rasbury

I was just kidding but mine stay clean...part of keeping up!

raybo3

The history of di-electric grease is that it was made for spark plugs. Put it on the ceramic so the boot would not stick. Its not made for connections. @Willhound I think your thinking of No Ox Grease for aluminum wire that would be used on copper.  

Willhound

I think maybe graphite grease ?

GMSLITHO

KY jelly works 

rasbury

GMSLITHO said:

KY jelly works 

on just about everything

Cableguy Greg

@rasbury 1000MCA for the starting battery. Sam’s has group 31 AGM batteries for a good price. They are made in the USA by EastPenn/Deka 

rasbury

I don't have sams but my neighbor does...really a deal or can I get the same price anyway?

Grahamu

Providing your battery is isolated and starts the engine only a group 24  cranking battery is all that is needed.

rasbury

Well I'm lost trying to find batteries...and I'm not dropping 500 to a grand on batteries. If I were going out in the ocean etc....I see the prices range from 100 bucks to several hundred bucks for batteries that would seem to do "the same job." What am I missing?

rasbury

Grahamu said:

Providing your battery is isolated and starts the engine only a group 24  cranking battery is all that is needed.

What do you mean by "isolated"? I have two batteries on a switch....I need a starting and a house. I believe for the 350 MPI I need 850 CCA...the series of batteries are available in different CCA ratings so I guess I'm not to clear on what the group number really means...is there a batteries for dummies section here? I have seen so many discussions that seem to center around spending 500 bucks a battery or your just wasting your time....I will have to look and see what I have now which seemed to work OK...

GMSLITHO

I have 2 interstate marine /rv deep cycle 690 cranking amps they seem to work fine 

Grahamu

@rasbury, The normal set up is a start battery and a house which you say you have. Providing no one has changed the wiring and your battery selector switches are in the on or "1" position your start battery is isolated and only used for starting your engine and in some cases your bilge pump. An 850 CCA cranking battery is all you need. The house battery should be a deep cycle battery and if your present one has been meeting your boat's demand stick with a new one of the same type. Group 24 refers to the dimensions of the battery approx 10-1/4" x 6-1/2" x 8" Height, a group 27 is basically the same except 12" in length

rasbury

@Grahamu
I was looking on batter plus site and they talk about a BMI group?? Seems like the industry makes this more complicated than it should be!

Grahamu

Yes the more you look for information the more confusing it will become.
Here is BCI size list

BCI Battery Group Size Chart

Knowing the exact BCI group battery size helps to find new battery replacement, however, knowing just BCI group size is often not enough.

Batteries also differ by their:

- purpose: starting, dual-purpose, deep cycle,

- cell type: AGM, gel cell, flooded cell,

- chemistry: lead-acid, NiCd, NiMH, lithium, etc.

Other important information includes details like terminals number, type, and orientation, battery maintenance, housing material, etc.

Knowing all this information significantly helps to find proper battery replacement.

The most common battery groups and their dimensions in inches and centimeters are:

Group Size	LxWxH (inches)	LxWxH (cm)
Group 24 Batteries	10.25 x 6.8125 x 8.875	26 x 17.3 x 22.5
Group 27 Batteries	12.0625 x 6.8125 x 8.875	30.6 x 17.3 x 22.5
Group 31 Batteries	13 x 6.8125 x 9.4375	33 x 17.3 x 24
Group 34 Batteries	10.25 x 6.8125 x 7.875	26 x 17.3 x 20
Group 35 Batteries	9.0625 x 6.875 x 8.875	23 x 17.5 x 22.5
Group 51 and 51R Batteries	9.374 x 5.0625 x 8.8125	23.8 x 12.9 x 22.3
Group 65 Batteries	12.0625 x 7.5 x 7.5625	30.6 x 19 x 19.2
Group 78 Batteries	10.25 x 7.0625 x 7.6875	26 x 17.9 x 19.6

When replacing the old battery with the new one, be sure that the new one is of the same chemistry as the old one (or it is a verified "drop-in replacement" battery) and that it has the same or better electrical features

rasbury

so the group is only the size....so I buy one for starter with around 850 cca and then the house battery is a deep cycle....so as long as it fits in my battery tray that is really the only concern with the group number? How are the deep cycle then rated? The group has really nothing to do with the function?

YYZRC

How about you post a pic of what you have now?

rasbury

I will see if I can do that on the way home....appreciate the guidance. I know some on here will spend unlimited boat bucks on batteries and while I want something adequate, I don't want to go way overboard either... 

Grahamu

Deep cycle batteries are rated the same, by AH (amp hours). Your present house battery should be stamped or labeled with it's AH

rasbury

I will post what I have!

mbnarney

On myy 270 it came with 2 24group batteries. I went with the same Duracell from Battery Plus. The start battery is 800cca and 1000 ca. Those are now made by east penn that also makes Deka. Around $100 and never a problem.