8D starting battery replacement

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NWboater2

Senior Member
Joined
Apr 28, 2021
Messages
124
Vessel Name
Ripple
Vessel Make
2005 Grand Banks 42 EU
Hi all. I have a still pretty new to me '05 GB 42 with a single JD 6068. It has lots of Lifeline AGMs, in three banks.

Bank One is the engine battery, only. It's an 8D in a fiberglass box, in the after port corner of the ER. I don't know how old the 8D is, but the original wiring diagram shows a 4D there. But the 8D box looks like all the others, heavy fiberglass with a slightly peaked top....makes me think it might be original, but why would someone upgrade from 4d to 8d, including a new box? 4d is ample. right?

Picture below...

Either way, Start/Engine/Bank One batt is charged thru a newer Victron 300 multiplus and an original Pathmaker, and the alternator, and the generator.

Ive always noticed a difference between house voltage and Engine Batt voltage on hte link 20 monitor (and the murphy gauge) when running. (I wrote a thread on it a year ago, but stopped worrying about it before I figured it out, cuz it had no symptoms).

Recently that discrepancy has increased, and (I think) the pathfinder has stopped connecting the start and house banks -- the remote light/switch by the helm is yellow, not green, even on shore power...

And the Engine has not started as strongly or as promptly - I got a voltage related warning on the murphy gauge, last time.

So I am going to replace the 8D. Not with an 8D, for sure, but I was thinking of a 4D lifeline AGM (on sale at fisheries, $705).

Questions:
--whatever I get, other than turning off shorepower do I need to do anything else to prepare to replace it? It has bundle of two big red wires and one black wire...3/0, maybe 4/0. Cables and connections appear to be in good shape

-- How do I get the 8D out? Seriously. There's a door into the laz right there (pic was taken through it), but then I have to get it up to the deck some I dunno three feet straight up through the hatch...onto the back deck, then over the side to the dock, into a cart. 160 lbs, small space...two highschoolers?...a pro?

I know the 4D is a lil better than an 8D, but still a pain to get in. I like the idea to two smaller batts in parallel - could be 27 or 31 lifeline AGM start batteries yes?

-- will they really fit in the 8d box? lifeline 8d is only 10.89 inches wide; the 31 is almost 13. Haven't measured my box, and quick google search did not turn up one just like it.

-- if i go that route, where do i buy a couple of properly terminated 4/0 Jumpers? (do they need to be 4/0?)

--any charging issues with them being start batts?-- better for cranking, but do i have to tell Victron?

--oh yeah. Am I likely correct that I need a new start batt??

Thank you!
 

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I'm going to replace (2) 4D house batteries with LiFePO4. Once I get the inverter in and the isolation installed and verified I'm going to take the boat over to the yard and have them remove the old and install the new.

I'm not going to risk my back trying to lift those heavy batteries bent over in the engine room.
 
Start Battery

You may want to investigate how many CCA’s your engine requires for a start bank. We have an 8.3L Cummins and use 2 group 32’s in parallel. We did this after removing 2 4D’s in parallel. You need to measure your box to see if they will fit and you will need to add/update the cables but much easier to move them than the 8D. We bought the Full River brand AGM as they were available from our battery supplier at the time.
 
NWB
Why not replace the 8D start battery with another, sealed non AGM for that matter. That way your box, wiring and switch gear all remains the same. I never have had a problem finding a young strong back or two to do the lifting in and out for a 50 dollar bill.
 
On a previous boat I had 5 8Ds in glassed in battery boxes that only had about 15” clearance above them. I hired a gut to come in and swap them out. I wasn’t there when he did it and it must have been a real PITA but he got it done and I didn’t have to rewire anything. I would look at hiring it done and be good for another 6 years or so.
 
Memory lane. About 5 years ago I pulled an 8D from the hold with a few grunts. Now, the 6v batts appear to be heavier as I stuggled to pull them for replacment. Getting old sucks.
 
IG copied lots of GB things, incl the 8D in a box. Despite the remove/refit weight issue, another 8D using existing wiring makes sense. Sometimes you can slide the box out to improve access. Plan how you are going to do it, both remove and refit. We 2 guys have done it a number of times with batts up to 60kg but the next ones (270Ah/1700cca) are 73kg, we`ll get help.
There are 8D AGMs with a cca rating, look for one of those. All AGM helps with the charger/battery setting.When choosing, check +/- polarity location is the same so the cables suit the connections without wrangling.
 
I have 3 8D AGM for start/ thruster & 2 house. When needed my plan is to replace 8Ds w a pair of GP 31 AGM very close for CCA and AH for both start & house needs.

In Mt motorhome my diesel start battyscareva pair of sealed LA GP31s and more than adequate for starting most diesels.
Handling 8Ds usually takes 4 people for boats 2 teams to get them aboard and get them below to ER. Never again...
 
OK! good insights thanks. My own novice research including here suggest the 4D has ample cranking amps -- 1360 MCA (vs 1650 for 8D) but i think the JD needs something far less than 1000.

I will re-use the existing cables and box, no matter what I do - the 4D is the same length and height, just 2.2 inches narrower. I was thinking of filling in the space with something inert so the 4D doesn't slide around and wiggle its cables?

I'm going to stay w Lifeline AGM cuz all the other ones already are (four 4Ds house, 31 gen start, plus 8Ds bow and stern for thrusters....8 total) and the Victron is set up to charge those, and so is the Balmar external regulator.

Yeah i guess ill just hire some kids to wrestle it out and the new one in. How about prep to do so. turn off power, disconnect and away i go?

thanks all.
 
Yes. As you said just turn off and disconnect. However be VERY cautious. Best to use insulated tools. If you drop a wrench across the terminals or contact a grounded point while you are removing the positive lead sparks can fly and worse. I like to find something to cover the terminals as quickly as possible. Be sure to clean up the terminal connections before you put them onto the new battery and there is also some battery terminal spray you can apply.
 
We filled space in the box left after replacing the genset 6D with an AGM a little smaller. Used foam packing at hand but I`ve used pieces of wood previously, just make sure the replacement can`t slide. Make sure the terminal locations are the same. Prep sounds fine.
Be careful using kids who may be susceptible. The main hazard is back bent while taking a load, popping a disc for a lifetime of trouble. Better use someone who knows safe lifting, some might use a block and tackle. We got away with it by careful planning but I have annoyed my old disc injury which fortunately settled, as expected(hoped).
 
How many revolutions to start your JD?
My boat had a 4D start on a pair of TMD40s and an old Onan Genset. It was completely adequate, on the main s that required 2 to 10 seconds of grinding to start. I re-powered to TAMD41s that start on less than 1 rev, and a Westerbeke genset that starts about as easily as the old Onan did. The last time I replaced my start battery, I couldn't get a 4D, so I bought a smaller battery, as that was what the marine store I was in could supply, as an emergency interim solution. That was 3 summers ago and that car sized battery has been totally adequate.
Gone are the worries about removing a much overweight battery.
YMMV.
 
JD used to start in 1-2 seconds, always fast. Still not close to ten secs (maybe 5?) but it sounds tired first. Murphy gauge doesn’t like the delay - can’t remember exactly what it says but something about low voltage. I can just cancel the warning when it’s running, then all good. But it’s getting worse hence the Q. I think it’s just an old battery….
 
JD used to start in 1-2 seconds, always fast. Still not close to ten secs (maybe 5?) but it sounds tired first. Murphy gauge doesn’t like the delay - can’t remember exactly what it says but something about low voltage. I can just cancel the warning when it’s running, then all good. But it’s getting worse hence the Q. I think it’s just an old battery….

Sounds like it cant handle the load much longer. If/when you do get a new battery I would expect to hear it starts faster again.
 
I have 3 8D AGM for start/ thruster & 2 house. When needed my plan is to replace 8Ds w a pair of GP 31 AGM very close for CCA and AH for both start & house needs.

In Mt motorhome my diesel start battyscareva pair of sealed LA GP31s and more than adequate for starting most diesels.
Handling 8Ds usually takes 4 people for boats 2 teams to get them aboard and get them below to ER. Never again...

4 people? Eat your Wheaties! Once in Anacortes 1 guy yarded my 2 8Ds in and out.
 
I just replaced my 4D starting battery with 2 group 24 batteries. I am not lifting 140lbs any more. A 4d has has about 1400 CCA. The total of the 2 group 24s is about 1600 CCA and 55lbs each.

As to cable size. I would go with the biggest cable 4/0. This will provide a better path for more amps to reach the starting motor
 
4 people? Eat your Wheaties! Once in Anacortes 1 guy yarded my 2 8Ds in and out.

Congratulations to the muscleman!
I've loaded / unloaded them into a SUV myself but those days are gone.
I'd like to see (hire) the one guy get them out the ER hatch on my boat... not to mention from swim platform to ground while on the hard.
 
I am now 75 yrs and no more fooling around.
Last two times I changed batteries I hired two movers. They are young enough to be strong and old and experienced enough to not be foolish. T'was not inexpensive but worth the help.
I set up lines to lift the old out and the new in while they stood in the saloon overhead..
They are all 8D so no more fooling around. THe lines took the strain off the guys, at least most of it and their backs were straight.
Once in the E.R. I then have a set of hooks overhead of the mountings and I use a small block and tackle setup to actually lift them into the containers with some pushing to swing them over the trays..

Once the batts are into place I then install pieces of plastic or wood, whatever is left over from the garage jobs, so the batteries cannot slide around. Need not be a tight fit but just so if the batts shift they can gain no momentum.
I then use ratcheting straps to hold them down.

Just my way to almost eliminate any opportunities to get hurt.
 
8D Replacement

Last year I removed and replaced the 2 8D batteries in our Mainship Pilot 34.

Used the same method as the prior swap, 8 years earlier. And the same Crown wet acid batteries.

The batteries are reached via a hatch in the cockpit. Using a plank (2x8 -6 ft long) I can slide a battery up the incline unto the deck, and then onto another plank across to the cockpit door. And then, using the first plank, from the cockpit, out the door to the dock. Used an appliance cart to transport the battery to the car and then used a plank to make a ramp for getting it into the back of a Toyota Matrix.

Reversed the process to move a new battery from the car to the cockpit.

Then repeated with the other battery - old out and new to the cockpit.

Cleaned the battery trays and connections and used the plank to slide the new batteries into place.

Only lifting required was raising one end of a battery so that my wife could push the end of a plank under it. She also helped steady things and helped pull to get them up the incline.

It's not easy - boat needs to be stern to the dock, need to be able to lift up half the weight (~80 lbs). It took about 4 hours elapsed time - and then we celebrated with a glass of red wine!
 
NWB
Why not replace the 8D start battery with another, sealed non AGM for that matter. That way your box, wiring and switch gear all remains the same. I never have had a problem finding a young strong back or two to do the lifting in and out for a 50 dollar bill.

+1 from me
 
It`s possible for the same 2 people to remove and replace the 8D beast. We`ve done it, requires planning, forethought, and step by step positioning of battery and people.
One time the son at our shipwrights, alone, with ease, loaded an 8D onto his workboat, ferried it to our boat, lifted it off the workboat, and lifted it into position in the ER. He trains as a weightlifter. And he`s gay.
 
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Be careful!
I recently dropped a brand new group 27 from West Marine when the handle slipped out of its slot. Glad it wasn’t an 8D.
My foot hurts!
 
The batteries are reached via a hatch in the cockpit. Using a plank (2x8 -6 ft long) I can slide a battery up the incline unto the deck

I used a 2X6 plank from ER diamond plate to cockpit sole pushed batteries up. Then used cardboard to pull batteries across cabin and deck. Only manual part was from deck down to swim platform, and from platform to dock. Keep back straight when lifting.

Once cracked L5 when bent over. Took years to heal. If it takes me hours to rig up a chain hoist to lift something, then it's time well spent.
 
I just replaced an old 8D Lifeline AGM with 3 x Firefly Group 31 110Ah / 770 CCA batteries in parallel. (I had them on hand after swapping them out for LFP.)

There isn't any good reason (that I can see) to use an 8D when it can be broken down into smaller batteries as a bank.

The Cummins 5.9 starts better than it ever has in the 9 years we've had the boat...
 
Late to the conversation as I only get the weekly update. I just replaced our lifeline 8D with the same, only $130 more than the 4d on the Fisheries site sale, not sure if that sale is continuing.

If you want to test the start battery, use the min/max function on your multimeter if you have one. Dropping under 10 volts indicates that you need to replace.

My wife and I lugged the beast down into the ER after several attempts to find young backs. Really not too difficult if you take your time.
 
Consider 6 volt replacements

The starting bank on our GB-49 is still a pair of 12v 8D AGM's but the PO replaced the 3 house bank 8D AGM's with 6 6v AGM's and they fit in what apparently are the OEM boxes.
 
I just replaced an old 8D Lifeline AGM with 3 x Firefly Group 31 110Ah / 770 CCA batteries in parallel. (I had them on hand after swapping them out for LFP.)

There isn't any good reason (that I can see) to use an 8D when it can be broken down into smaller batteries as a bank.

The Cummins 5.9 starts better than it ever has in the 9 years we've had the boat...

I agree. Can someone explain any benefits to an 8D over a paralleled group of 31's or similar power 6vs. Pretty sure 2 31's take the same footprint and provide the same AH and CA. Yes some very short cables are required, but otherwise why would you want to bother with 8Ds?
 
Pretty sure 2 31's take the same footprint and provide the same AH and CA.


I think not exactly. Two G31s will likely fit inside an 8D box with room to spare (and 3 G31s won't fit). Two G31s in parallel will usually give you about 200 Ah capacity, where a typical 8D might give you somewhere between 230-255 Ah.

For starting loads, a pair of G31s often (usually?) provides more cranking amps than a single 8D. (I think.)

For house loads, compare 6x 6V GC2s, which are said to fit inside an 8D box... and might give you something like 660 Ah.

-Chris
 
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