New 8D battery or two 6v golf cart batteries??

Unfortunately I think it's time for a new battery for my port engine. The existing one came with the boat when I bought it almost two years ago and it's time. Should I get another 8d or two 6v golf cart batteries. All this bank does is start the port engine and provide power to the windlass.. Any thoughts?? I'm on a super tight budget as I unexpectedly lost my main source of income and I'm living on my social security check alone.. ouch.

Thanks folks

8Ds were meant to start 7 liter DD 671s and bigger and be installed in 18 wheeler tractors mounted low and outside where they can be gotten at with a fork truck, or installed in new boat shops before the superstructure goes on.

Unless you have an engine bigger than 6 liters use a Group 31. I just bought on a Batteries Plus for $150 and it produces 1,000 CCA which is the spec to look at for starting (or MCA which is measure at a higher temperature). It will be less at Costco or Sams Club.

Golf cart batteries are great for house use but not for starting.

David

Bigfish said:

Should I get another 8d or two 6v golf cart batteries. All this bank does is start the port engine and provide power to the windlass..

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The 6 volt bats in series is a nice alternative, however they're a few inches taller than the 8D. So if you decide to go that route make sure you have the height clearance.

I didn't have the height clearance, my batteries are located under the engine room floor, so I swapped out my 8D's for 4D LA's and that was a nice compromise, less weight, fits the existing trays. Plus it allowed me room to replace the small generator battery with a 4D which starts the jenny and is a backup to the mains if needed.

Since you're on a budget, look at Pacific Power Batteries. I bought the 4D LA to replace the small automotive generator battery from them a couple of years ago and it's been fine. It was about $200 and they took the smaller old generator bat. for trade.

Bigfish, Check a local industrial and golf cart battery supplier.

Four years ago, I needed to replace my 8D that came with the boat. I found an 8D deep cycle that came out of an industrial application as a standby battery. It was kept in a fully charged state and tested great. I picked it up for $75 and it's only now starting to show one cell with a slightly reduced specific gravity. I thought 4 years for a $75 battery was pretty good.

I just looked into replacing that start 8D deep cycle with a Group 31 start battery. The local battery shop will reduce the price of the 31 with the larger 8D core. I can get a new Group 31 start battery for $75. I bet I can get 5-7 years out of this Group 31 start. The only negative to me is that this Group 31 is a "maintenance free" lead acid. The caps can be removed to add water, but they require a large screwdriver to remove and install the caps. I believe all LA batteries need the electrolyte level checked periodically and there is really no such thing as a true Mx-free LA battery.

Big,

I also replaced an 8D with a group 31 for my Perkins 6-354. Started first time every time.

Rob

djmarchand said:

8Ds were meant to start 7 liter DD 671s and bigger and be installed in 18 wheeler tractors mounted low and outside where they can be gotten at with a fork truck, or installed in new boat shops before the superstructure goes on.

Unless you have an engine bigger than 6 liters use a Group 31. I just bought on a Batteries Plus for $150 and it produces 1,000 CCA which is the spec to look at for starting (or MCA which is measure at a higher temperature). It will be less at Costco or Sams Club.

Golf cart batteries are great for house use but not for starting.

David

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This ^^^^

I'm doing this now, except I'm replacing 2 4d's with 4 6V GC's. My son lifted the 4d' out for me.

GC batts are not designed to start an engine. They will do it but for your application a group 31 would be better.

I use a group 27 on one of my Lehman 120s. Starts every time with no issue whatsoever. The cart batteries are for the house.

You might check out your local semi truck dealers. I used to buy rebuilt batteries Group 31 for about 40 bucks (last year) they tested fine. Worked well the times I used them. And in a couple years if you have to change it out again maybe $$ situation will have changed.

Some years ago we replaced the boat's two 8Ds with six 6vdc golf cart batteries. Four of the golf cart batteries replaced one of the 8Ds as our house bank, and gave us roughly double the amount of amp hours. The other two golf cart batteries replaced the other 8D and acts as our start bank, although all six batteries are connected together when a start button is pushed.

Three golf cart batteries fit in a single 8D battery box, so no changes were required to our battery storage or the boat's wiring. The only new wiring required were the short jumpers that connect the golf cart batteries together.

This has been one of the best and most useful changes we've made to our otherwise stock boat.

You have two conflicting requirements. Engine starting and running the windlass.

Have a look at this link. It is written by a very smart guy:
What Is A "Deep Cycle" Battery? Photo Gallery by Compass Marine How To at pbase.com


The windlass current is supplemented by the alternator, but there will be occasions when some cycle capacity is needed. The situation of the anchor failing to set first time. Retrieval and resetting will use some battery capacity. If the engine is then shut down the battery will be sitting at considerably less than 100% SOC.

As a general rule starting batteries have a very poor life if not kept close to 100% SOC. They are designed to start the engine (which uses very few AHrs) and then be rapidly charged back to 100%. Deep cycle batteries are not constructed to deliver the high currents for engine starting, but they still manage this task reasonably well.

There is no perfect answer, but my money would be on the 6v deep cycle batteries having a much better life in your application.

Bigfish said:

Should I get another 8d or two 6v golf cart batteries. All this bank does is start the port engine and provide power to the windlass.. Any thoughts??

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You can likely find your engine's minimum CCA/MCA requirements in your documentation somewhere, and your starter motor may also be labeled with some minimum MCA/CCA info.

I'd suspect a single Group 31 may actually meet your minimum needs, would be less expensive than either one 8D or 2x6Vs, certainly lighter than an 8D, might free up some usable space...

Unless you want to add a bit of safety net for anchoring, in which case a pair of G31s could still be a useful solution.

-Chris

Chris is correct with doing the research and I will add follow up with the math.....guesstimate or better measure the average amps used by the windlass and the average time it takes to recover your anchor.

With the engine high idling when pulling the anchor.....most of the time you could probably subtract half the windlaass amps so the drain isn't as drastic.

My "guess" is a group 31 will suffice for your service, I replaced an 8D with one for my 120 Lehman.

Starting batts are designed for starting.

They will work as a windlass fill in , esp if mostly used in the AM when some engine operation will follow.

I recently purchased 2 ser 31 to start my RV , price $125 at the DD dealer.

The last 8D cost $150 so is cheaper than 2 ser 31s.

The last price for a Trojan 105 (6V seep cycle) was $88 cash.

All pricing expects a trade in batt.

I would choose a good 8D start batt for your service , and a couple of 6 packs for the dock help on lifting.

The key to any battery is how much lead it has inside.

Find the weights and try to get the proper batt for your service , starting, at the lowest per pound cost.

Never ever use a start batt for deep cycle house service , although many times a set of deep cycles will do fine for warm weather starting.

You don't say what the other battery does but if you are worried about just using a gp31 can you switch the batteries??


Do you have big engines with big CCA requirements?




I would start with the simplest and cheapest solution, a GP 31 with sufficient CCA, keeping in mind that the engine will be sharing the windlass load. If you are not happy with that then add a second in parallel.

FF said:

Starting batts are designed for starting. They will work as a windlass fill in , esp if mostly used in the AM when some engine operation will follow.

I recently purchased 2 ser 31 to start my RV , price $125 at the DD dealer. The last 8D cost $150 so is cheaper than 2 ser 31s.
I would choose a good 8D start batt for your service , and a couple of 6 packs for the dock help on lifting..

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I agree. The windless on your starting battery is OK, if your main engine alternator is running when the windless is in use. You don't want the battery to be left sitting half full overnight. Really hard on start batteries and will shorten their life. I would worry about using a start battery that only meets minimum starting requirements. Get air in your injector lines that you can't bleed out, other than by rolling the engine over and you will want that reserve battery capacity. If you're going to go minimum, then you at least have a switch to bring your other batteries into the starting circuit.

Edelweiss said:

... I would worry about using a start battery that only meets minimum starting requirements. Get air in your injector lines that you can't bleed out, other than by rolling the engine over and you will want that reserve battery capacity. If you're going to go minimum, then you at least have a switch to bring your other batteries into the starting circuit.

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After we bought Hobo and were re-doing the battery configuration, I asked Norm Dibble, the PNW Ford Lehman guy, now retired, what we should do for the FL SP135. He said that a 4D is suggested but since we were in AK, he recommended an 8D or equivalent due to the routine colder starting temperatures. Just someone else's opinion but it made sense.

Larry M said:

After we bought Hobo and were re-doing the battery configuration, I asked Norm Dibble, the PNW Ford Lehman guy, now retired, what we should do for the FL SP135. He said that a 4D is suggested but since we were in AK, he recommended an 8D or equivalent due to the routine colder starting temperatures. Just someone else's opinion but it made sense.

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Cracks me up because when I called American Diesel what battery for my 120....they gave me some designation that could have been a good Group 24 Battery.

I checked the cranking amps required for the 120 starter motor....Around 500 was good enough so I went Group 31 (well something near it) that had 900+ CCA.

Battery CCAs seem to have gradually increased for the same battery size. A size that would have been inadequate for starting may not be now. Replacing batteries, I often notice CCAs have risen.

Guys, really??

The Cummins 5.9 in my truck that must start in well below zero weather (by design, mine does not need to). Has a grid heater that uses 100+ amps and cycles on and off to heat the charge air even after engine start when cold while the alternator is off line until the grid is done cycling due to the high amp loads.

Funny how the battery requirement for this vehicle is 2 group 24 starting battery's.

Now explain to me why you think a 120 Ford engine starting well above freezing, using no glow plugs or grid heater needs an 8D battery, the same as a 12+ liter over the road truck engine, I don't get it.

I think trawler owners way overdue the starting battery's and under equip the house side.

I use two 900 amp group 24 battery's to start ( more then enough IMO but I have the space to fill) and 8 6-volt GC battery's for the house, with a sep. group 27 to start the gen-set.

I can switch to the house to start if needed but have never needed to, I have jumper cables to use the gen-set batt. to start if all else fails. Thruster, windless and davits run off the house.

Solar keeps the house topped off and a Smart Charger off the house keeps the start topped off.
Balmar Digital Duo Charge

Very few of us need to buy 8D battery's for our starting requirements and there are only 4 company's* that make "Deepcycle" 8D's so using them as house is a dumb expense and heavy as hell when ya need to change them.

*
Charge voltage - SailboatOwners.com

Our setup is a 4D to start our Lehman 135 and power the windlass. Engine is always running when we anchor and the battery is connected to our house bank and alternator through a combiner relay, so it remains pretty fully charged by the time we shut the engine down. The charger then gives it more when we fire up the genny that night or next morning. So far, working great.

I agree with others, pull the 8D (actually get a strong kid to do it) and replace with a Group 31.

Better get two strong kids to pull those 8Ds! I am just in the process of replacing all SIX of my AGM 8Ds with twelve 6-volt golf cart wet cells (with watering system). Exactly the same setup that we used on all the Great Harbours - no designated starting batteries - just one huge bank for starting and house purposes. Plus a completely separate Group 27 starting battery for the 13kw genset.

BruceK said:

Battery CCAs seem to have gradually increased for the same battery size. A size that would have been inadequate for starting may not be now. Replacing batteries, I often notice CCAs have risen.

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Some technology changes in all battery components have improved capacity, but like engine horsepower ratings, different companies methods of determining and measuring capacity aren't always consistent with another.

"Group Size" 24, 27, 31, 4D and 8D is not the capacity of a battery, its the relative dimensions of the box H x W x L measurement (Although a larger box, greater volume, may contain more components material and more capacity.) If you don't like the weight of 4D or 8D batteries, then use two 525 - 600 CCA Group 24's, 27's or 31's in parallel, (like the example of the diesel pickup someone else mentioned), but don't skimp on capacity. If your anchored out in the islands, it's difficult to get a jump start from the local service station.

In LA batteries the weight of the battery is also a good gauge for comparing two similar batteries. I've handled 8D batteries of different makes that had significantly different weights. The lighter, cheaper batteries had significantly less capacity even though the Group Size was the same.

I just got 15 cents/lb. for my old 4D's at a recycle yard. They were just under 200lbs.

Having lived on 12V for many years in my sailing days, I'm going overkill on my (new to me) Boat...

(2) 31's for the start bank (existing 2 yr old batteries that came with the boat, though one was the House). Combined the 2 for the new start bank (200hp Volvo)

(4) 6V new GC's for the house bank = 420 amp hours or so

This set-up will easily fit, but no more (It's a small boat!). Should meet the cruising needs i envision, and keep the beer cold for a few days on the hook. My boat has limited 12V needs other than the Norcold fridge..I rather like the simplicity of it all.

This gives me plenty of house capacity and a big start bank for fallback..

Steve, will you have a way to charge at anchor besides the big motor alternator? Generator or solar or wind?

FlyWright said:

Steve, will you have a way to charge at anchor besides the big motor alternator? Generator or solar or wind?

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Al...Yes, when we start cruising I'll carry a portable 2000 Watt Generator/inverter with a 30 amp socket that will plug right into the boat for charging through the onboard Battery charger. I may, at some point, upgrade the stock (60 amp) engine alternator to a higher capacity Balmar.. We need to get out there this spring/summer and see how all this works.. We haven't cruised the boat yet having just recently bought it.....
A few 2-3 day overnights to start, then probably a month or so up on the Chesapeake this summer. I'm trying to detail in the systems to work the way we'll use the boat.

Great choice! I use mine similarly. I have a 55A shore charger that I power with the Honda. It leaves a little extra capacity if i want to make coffee or run the microwave at the same time. Plus, when just charging, it doesn't run the Honda at full throttle so it's quieter. I carry 2 power cords: one for the shore plug and the other runs to the generator on the FB. When I'm at on the hook, I just swap cords at the boat's 30A plug.

I did the Balmar conversion and it works well for us the way we operate our boat. I like seeing 80-100A flowing into the battery initially, but it ramps down to something less than 60A after a short while. If you motor for a couple hours regularly between anchorages, you might not see any real great advantage to the larger alternator. If you motor a whole lot more than that...maybe 6 or more daily, a smart regulator which provides a float charge might prevent overcharging.