Battery replacement question - gb trawler

[JESSEDIVER49]

I have an '84, 42ft GB trawler, with Ford Lehmans and it has 3-Deka 908D (lead acid, 1700 amp) batteries for starting and 2 of the same for the inverter system. Each battery weighs 130 lbs.
For my first time owning the boat (5 yrs), I need to replace the batteries. I am leaning toward placing in kind with the Deka 908Ds rather than making a switch to AGMs but want to hear back from the more seasoned owners if I'm making the right decision.
Also, I'm a do-it-yourself owner for most maintenance but I see these 130 lb lifts may make doing at a boat yard more sense. Any comments on that appreciated.

 

[bayview]

Dockmasters often know some guys who will lift the batteries for a reasonable price if you get everything ready.

 

[Xsbank]

You don't need batteries that large for starting your Lehmans. I used 2 group 31s from Costco (no maintenance) and they worked for years until I sold. I am using two of those now to start my 8.3 Cummins.

House bank, use golf carts. Once you get those old things out it is relatively easy to wrestle those golf carts around.

 

[ranger58sb]

I have an '84, 42ft GB trawler, with Ford Lehmans and it has 3-Deka 908D (lead acid, 1700 amp) batteries for starting and 2 of the same for the inverter system. Each battery weighs 130 lbs.
For my first time owning the boat (5 yrs), I need to replace the batteries. I am leaning toward placing in kind with the Deka 908Ds rather than making a switch to AGMs but want to hear back from the more seasoned owners if I'm making the right decision.
Also, I'm a do-it-yourself owner for most maintenance but I see these 130 lb lifts may make doing at a boat yard more sense. Any comments on that appreciated.

1700 amps? Maybe that's cranking amps?

I'd guess a single G31 would start your engine, or maybe you'd need a pair... You can check engine specs to see what minimum cranking amps are, but lifting a single G31, even if you have to do it twice to install two, would likely be easier than the 130-lb 8D.

Your 8Ds might be rated at approx 245-Ah (20-hr rate) -- for a total of approx 490-Ah on the house bank (you can check that). Another way to get there would be pairs of 6V GC2 golf cart batteries, each individually weighing less than an 8D. Two pairs would be about 440-Ah, and 3 pairs would be about 660-Ah, and each individual battery would weigh much less than an 8D. Generally 6V GCs are designed for deep cycling, whereas the 8Ds would more likely be a dual-purpose design (guessing, a bit).

You mention AGM, but if you can easily (enough) service the batteries periodically and if you don't mind doing the work... flooded lead acid would be less expensive.

-Chris

 

[DavidM]

The 1,700 amp value you stated in your OP is the 32 deg cranking amps, sometimes also called marine cranking amps. It has nothing to do with deep cycle amp hour capacity. In fact that Deka battery is a starting battery and not really suitable for routine deep cycle discharge/charge cycles.

You can keep the Deka 8D as a starting battery but as others have said, a good group 31 has enough cranking amps to start your Lehman and weighs half of the 8D. Look for one with at least a 1,100 MCA spec.

The only sure deep cycle battery except for a few really expensive 12V ones is golf cart 6V batteries and similarly constructed floor polisher batteries. There are millions of these batteries in service and if someone made a non deep cycle version it wouldn't last and they would quickly be run out of the market. Most deep cycle batteries are about the same quality with a nod to Trojans.

You have to wire two GC batteries in series to get 12V and a pair has an amp hour capacity of 220. A pair of GCs will fit in the space of a single 8D so you have room for four pairs which will give you 440 amp hours of capacity.

Sam's and Batteries Plus have them at a decent price.

David

 

[dhays]

I am a bit confused about having 3 x 8D batteries for starting two engines?

For a house bank, I’d ditch the 8Ds and go to flooded GC2s as has been mentioned. The Golf Cart batteries will perform better as a deep cycle battery than the 8Ds. Making the switch is actually pretty easy and can be relatively inexpensive. I like the GC2s that you can find at Costco or Sam’s Club for about $90 each.

Getting your existing batteries out is a pain, but can be accomplished with a 6 pack of beer and a couple friends. I was able to remove a couple off my boat by myself using some block and tackle and my crane.

 

[jungpeter]

Hi Jessediver49,

I'm a tad confused. You say you have three Deka 908D batteries for starting two Lehmans, with two additional 908D's dedicated to the inverter. This seems odd to me. First, how does one connect three batteries to two engines as start batteries? Secondly, it seems like even a single 908D is gross overkill to start a Lehman. Thirdly, it appears from the Deka literature that the 908Ds are 8D starting batteries. So why would one use them "...dedicated to the inverter."?

There are an infinite number of ways to wire a boat's electrical system, including what batteries to use and how to configure them. You will probably be deluged with an equal number of opinions on just how to do so from the participants on this forum. Personally, I'm not going to engage in that debate.

However, since you asked, I suggest you have a marine electrician come aboard and help you fully understand exactly how your boat's electrical system (AC and DC) is configured, what your true storage capacity is, and what configuration and battery capacity you might need to operate your boat the way you wish. From there, hopefully you can read up on your options (AGM vs flooded, 8D's versus Group 31's, 6V vs 12V, etc. ) and then proceed to optimize your electrical system for your convenience.

For reference, see Ample Power Primer. I believe there are a huge number of books written on this subject by authors such as Nigel Calder, articles by such as Steve D'Antonio (Steve D'Antonio Marine Consulting | Your advocate for a safer, more reliable and less costly boating experience , and web sites such as Panbo.com. All are well worth reading. As is listening to a marine professional!

Regards,

Pete

 

[FF]

A big hassle with changing out batteries is lifting them.

If like many 8D there are handles , great!!


If for car starting Ser 31 , or the usual Golf card batt they may not have have a way to grab them

The local NAPA will have handles that look like there made from fan belts with universal post grabbers on either end.

These are cheap and make it lots easier for a couple of dock mates to give you a hand.

https://www.amazon.com/EZGO-609628-Battery-Lifting-Strap/dp/B00699WCUM

 

[dhays]

When I swapped out the batteries on my sailboat (replaced 2 x 4Ds with 4 x 6v GCs) I made some battery carrying handles with a spare length of light line and a 4” length of 1/2” PVC. Worked great for the batteries I had and was cheap since I had the scrap material around.

Over a decade ago my son decided he wanted to make a bunch of marshmallow guns (it was a “thing” for the kids back then”). He bought a 10’ length of 1/2” PVC and used a couple feet of it. Since then I’ve found a bunch of good uses for pieces of that PVC.

 

[ranger58sb]

You have to wire two GC batteries in series to get 12V and a pair has an amp hour capacity of 220. A pair of GCs will fit in the space of a single 8D so you have room for four pairs which will give you 440 amp hours of capacity.

Typo, I think?

One pair, 220-Ah at 12V. Two pairs, 440-Ah. Three pairs, 660-Ah. Four pairs, 880-Ah. Ah all approx.

I think three GCs will fit in the space of one 8D? I was off-track in an earlier thread somewhere (or maybe on another forum) and I think that was the correction that was offered...

-Chris

 

[Nightsky]

Typo, I think?

One pair, 220-Ah at 12V. Two pairs, 440-Ah. Three pairs, 660-Ah. Four pairs, 880-Ah. Ah all approx.

I think three GCs will fit in the space of one 8D? I was off-track in an earlier thread somewhere (or maybe on another forum) and I think that was the correction that was offered...

-Chris

Yes, 3 GC's will fit in an 8D battery box. I swapped out a single 8D with a 4D to start a pair of Cummins 5.9's. Lots of cranking power (I think mine is 1200CCA), you just won't get as many tries on a difficult to start engine. Perhaps the three 8D's for starting the OP refers to is one for each main and one for the generator?

 

[FOG]

NAPA makes a Marine/RV Deep Cycle 8D battery, part # BAT276. Says it has
1400cca. Don’t know the amp hours, but maybe around 200.
Should work as a dual purpose for house and starting. Anyone try them?

 

[Bacchus]

NAPA makes a Marine/RV Deep Cycle 8D battery, part # BAT276. Says it has
1400cca. Don’t know the amp hours, but maybe around 200.
Should work as a dual purpose for house and starting. Anyone try them?

Dual purpose is the optimistic marketing story.
In reality it means not the best for either start or deep cycle.

 

[JDCAVE]

I use a couple of Group 24’s in parallel for my Lehman 135. They’d easily start both of your engines.

 

[foggysail]

I am a bit confused about having 3 x 8D batteries for starting two engines?

For a house bank, I’d ditch the 8Ds and go to flooded GC2s as has been mentioned. The Golf Cart batteries will perform better as a deep cycle battery than the 8Ds. Making the switch is actually pretty easy and can be relatively inexpensive. I like the GC2s that you can find at Costco or Sam’s Club for about $90 each.

Getting your existing batteries out is a pain, but can be accomplished with a 6 pack of beer and a couple friends. I was able to remove a couple off my boat by myself using some block and tackle and my crane.

I am with Dave’s suggestion. Too easy to get hurt lifting heavy batteries and those youngsters that you can hire will be upset if they get any battery acid on their clothes.

 

[Bacchus]

"youngsters that you can hire will be upset if they get any battery acid on their clothes."

Just offer them an opportunity to custom etch their jeans.
Those w big holes demand big $$$

 

[koliver]

You see what is happening here? Nobody in favour of keeping the huge sizes you have. Everyone wants you to ditch the 8Ds. Nobody sees any need to have 3 for starting.
I start a pair of Volvo 6 cyl diesels and a 3 cyl genset from a single 4D. I know, I don't need that much battery to start them, but that is what the boat came to me with.
I did get rid of 4 big house batteries, in favour of 4 GC 6v. Those are more than I need. When getting rid of the big format house banks, I bought a nice plastic battery box designed for the 4 GC batteries that then became my entire house system. It came with a lid, so acts as a storage location for some extra tool boxes between water checks.
Sometimes less is much more.

 

[BruceK]

We have 2 8Ds(220AH), one to start each Lehman, and they automatically parallel for starting. That`s how IG designed the boat. Batteries have come a long way since Lehmans were getting fitted into heaps of boats, so something smaller could work.
A word about flicking the job of lifting an 8D to someone else. They might be young and strong, but if you understand the mechanics of a disc injury, anyone who bends while lifting 130lbs is at risk. I believe those batts were designed to be lifted with a forklift into truck battery compartments.
We have done it manually, probably will again, but it is in confined space, with multiple lifts involved, down stairs or from deck down into the ER, a recipe for back injury unless done carefully with pre-planning. There may be the odd gorilla who can do it risk free, but for us mere mortals, and those we delegate to, be careful.

 

[FF]

"Dual purpose is the optimistic marketing story.
In reality it means not the best for either start or deep cycle."

Its add words like Hi FI or Heavy Duty , race tested, meaningless.

 

[CharlieJ]

NAPA makes a Marine/RV Deep Cycle 8D battery, part # BAT276.

As others have said; marketing hype. Diametrically opposed design criteria.

One 85' boat I work on uses 4 x Group 31 batteries in series (24VDC starters) to start 1200hp MTU engines. No problem for them at all and when it is time to change them; 50# a piece is far easier than 164# a piece!!

Here is an interesting exercise:
> It takes 3.6 sec to start a big diesel (usually takes far less but, bear with me)
> It takes 1000A to crank this big diesel
>> 3.6 seconds x 1000A = 3600Asec.;
>> There are 3600 sec/hr so: 3600Asec/3600sec/hr = 1Ahr!!

So a big diesel takes a significant impulse of energy to start it, but not many Ahrs.

 

[CharlieJ]

BTW, full disclosure, in my job as a marine electrician, I have made it my lifetime goal to banish 8D and 4D batteries from the marine industry!!!!

 

[DavidM]

BTW, full disclosure, in my job as a marine electrician, I have made it my lifetime goal to banish 8D and 4D batteries from the marine industry!!!!

8Ds and 4Ds were developed to start 18 wheeler and construction equipment 10+ liter engines that had to be started in zero degree temps. They are stored under the cab step and can be replaced by swinging one from a pickup truck bed to its storage spot with very little lifting.

Somehow boat builders started using them, maybe for the big DDs that go in sport fishermen.

They are not needed for a marine diesel of 8 liters or less. A good group 31 will work just fine.

David

 

[dhays]

BTW, full disclosure, in my job as a marine electrician, I have made it my lifetime goal to banish 8D and 4D batteries from the marine industry!!!!

I’m with you! I currently have 3 8D batteries on my boat. All were there when I bought it and are Lifeline AGM batteries in good shape. Two of them are for my windlass/thrusters. One is the engine start battery for the Cummins 5.9L.

When they die, I won’t replace them with 8Ds. The thruster/windlass bank may just get wrapped into my house bank and I likely will use AGM scissor lift batteries like I have in my house bank. The start battery will probably be replaced by whatever it is that the Dodge Ram pickups with that engine use. I believe it is two group 31 or 24 batteries.

 

[foggysail]

BTW, full disclosure, in my job as a marine electrician, I have made it my lifetime goal to banish 8D and 4D batteries from the marine industry!!!!

Charlie—- you have more work to do.

 

[porman]

Aside from the argument about which batteries to use, here's my experience with replacing five 8D batteries in our engine compartment. I made an A-frame out of 2X6's and plywood and used a come-a-long to lift them out of the engine bay and into the main cabin. Then I used two 2X4's as slides and the block and tackle from our Lifesling to get them up to the aft deck. Then I cheated and had a friend that lifts weights put them on the dock. Reversed the procedure to get the new batteries down into the engine compartment. No lifting (at least by me) involved.