Battery replacement time

[alcodiesel]

Hello all.

I am starting to look to replace the 4 year old batts on my boat.. Both are marine starting gp 24 batts and I have never liked how the house batt loses it's power when out sailing (powering a tablet, depth finder, autohelm) 6 to 8 hours

So I am thinking: a gp24 marine starting for engine and a gp27 marine deep cycle for the house.

Both from NAPA and made by East Penn.

Thoughts, contentions, opinions?

[joe_db]

See if you can fit a group 31 and the 24.
Another trick if you have room is to get an 8D battery case. That will hold 3 group 24s and you can use two for house and one for start.
BTW - make sure the house battery is a deep cycle battery, thin plate starting batteries die quickly when cycled.

[Dave Neptune]

Bill, batteries are a serious consideration. I used a deep cycle battery on both sides, house and start. The A-4 does not require a great deal of cranking amps so really no need. I did use a deep cycle U-2 on the start side just to try it out and not a single issue in about 6 months of use then I put the U-2 back in my hi-po buggie. I have always used 2 golf cart grp 8's for the house.

Put as much power on the house side as will fit and consider even going smaller with the start VIA a U-2. I used them in my 1940 cc 10:1 VW engine and on my 60Hp Yamaha in my Calibogie skiff. They work quite well.

Another consideration is AMG, not that they really have any more power. What they do have is more capacity to use. IE a L/A battery is safe to discharge to about 50% and the AMG can go to about 30% safely which is a lot more power to use when limited to size. They are more expensive but not that much when you consider the usable power.

I also used a deep cycle AMG a grp size smaller battery (don't remember the #) than the 24 and a bit bigger than the U-2 for my start battery in my Bene with a 56 Hp Yanmar, spun it nicely and I could fit it in a much smaller space around the engine.

Dave Neptune

[joe_db]

My start battery is a U1. They are about 250 amps cranking and about 30 AH. The A4 draws about 125 amps starting, the U1 is fine most of the time for that. If the engine has issues (see choke geometry thread) I can always start off the house.

[joe_db]

FYI - East-Penn Deka sells group 31 AGMs through Sam's Club with a goofy label. They are identical to West Marine AGMs for half the price

[sastanley]

Go as big as you can. I have 2 Gr29's as my house bank. I think the 29 & 31 are the same footprint, but I didn't have enough height for the 31s.

Joe, I had a friend with the same experience thru one of the "Batteries & Bulbs" places with his big 8Ds in his powerboat. What ever brand they were selling was the same battery and even built on the same line as the WM brand, they just peel off down the line in different directions with a different label, but 1/2 the price.

[Sam]

My favorite is Optima Blue Top Marine D34 [I think]. These are multi purpose AGM, lighter weight than deep cycle LA's and perform very well. I have two identical and switch back and forth regardless of needs. One was installed May 2008 and the other May 2018. Off season I store them in a basement and periodicaly put a low amp maintainer on them [ it pulses and supposedly disulfates them somewhat?]. They are more $'s but you can find them on line for less since they can be used and shipped in any position. Check them out.

[alcodiesel]

Thanks fellas. I don't understand some of the jargon, eg. U-2

But let me ask a couple of questions:

1. What about the batteries I described in my original post?

2. the pic shows the charger I have now. Will that charge AGMs?

Thank you and Merry Christmas

[Dave Neptune]

Merry Christmas Bill. No AGM's do require a bit more voltage for proper charging. If money is a big factor go for L/A and stick with "deep cycles" on both sides.

The U batteries are built for lawn equipment and small tractors and such. I like them for starting small engines as they can usually be placed closer to small engines in small spaces. That leaves the bigger space for the "house set" which does not need to be close. Just remember the batteries do not need to be where the factory installed them. I have even used them on "hot rods" with small blocks and big power :rolleyes!

I had an E-27 #174 which was an O/B model. I used the engine box as a pantry and moved the batteries from under the bunk to the forward cabin under the bunk next to the water tank. I found that "Easy" squatted in the stern and the weight up front helped to steady the bow .

Dave Neptune

[ndutton]

Merry Christmas to you too Dave, Bill and all forum members.

As Dave said, AGM's or other modern chemistry batts require different charging voltages and charging profiles than conventional lead acid batts for them to perform to their specs and after all, performance is the prime directive. Having a battery that fits in a space but does not perform is little more than expensive trim weight. Voice of experience here.

You'll change your shore charger to suit the AGM's but what about the engine alternator regulator? You should be changing that too to provide the higher voltage needed to charge the new batts. Then, what happens to your electronic ignition system current maximum of 4 amps?

Example:
Let's say your existing ignition system has an input voltage of 14.2 volts and 3.6Ω resistance, 3.9 amps system current. Then you make the change to AGM's with an AGM profile regulator. Now your charging voltage in absorption is 14.8 volts and your system current is 4.1 amps and supplemental resistance in the ignition circuit is indicated.

The point is do not forget your ignition system will be subjected to the new charging voltage too so don't overlook it.

[alcodiesel]

Thank you for that info! Happy Everything!

[joe_db]

Very useful info from East-Penn Deka.

[alcodiesel]

I am going with what Joe wrote: See if you can fit a group 31 and the 24.

[alcodiesel]

With these batteries installed, the 24 charges half a volt higher than the 31 with the Marinco charger. Is everything OK?

[Dave Neptune]

Bigger battery bigger draw, so less of a reading until full. Check the rest and "trickle" voltage when fully charged they should be very close.

Dave Neptune