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Old 05-18-2019, 11:09 AM   #1
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Battery questions... and suppliers?

Hi all - thanks in advance since I'm sure this has been answered before, but my forum search skills are lacking....

My batteries are toast. Currently I have two banks:
- starting battery is 1 8D
- House bank is 2 8Ds

I want to replace the house batteries with 4 GC2s and the starting battery with??? which is the questions. Currently I have a Volvo TMD31a motor that starts easily (I hope I did not just jinx myself) I want something I can manage that would be used for just starting the motor. I am not sure on what the CCA requirement is on the volvo - would a group 31 (flooded) battery work?

so... please - anyone know what I should use as a starting battery (That one person can move around to service and replace in the future)
AND where are good locations to locate the batteries?

It is my plan to rebuild the battery boxes to house the new battery configuration. I will include a way for the boxes to "slide" out for easy access to check and water. Currently access requires a contortionist... Has anyone built a sliding battery box? (The boxes would be secured in normal operation) I am open to ideas -

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Old 05-18-2019, 12:29 PM   #2
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Based on some past questions on TF (and answers by folks that know what they are talking about) it appears that a good GRP 31 should be able to start your Volvo without a problem.

If your current house bank is 2 x 8Ds, isnít that a bit over 300Ah? 4 x GC2 would be maybe 220-240Ah? Unless you donít need much, I would think that the 4 x GC2s may give you less capacity than the 8Ds gave when the boat was new.
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Old 05-18-2019, 01:07 PM   #3
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Go with all AGM batteries, and you won't need slide outs to check water.

Consult your engine owners manual for recommended start battery size. Probably one 4D or maybe a group 31 is sufficient.

For house batteries, you can replace the two 8D's with four group 31's if you want something that is easier to move. But when comparing cost, add in the extra battery cables.
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Old 05-18-2019, 01:35 PM   #4
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If I remember, 2 8Ds is about 440 AHs and so are 4 6Vs, or very close. I would go with 4 6V AGMs. They will fit in the same footprint as the 2 8Ds. Then you don’t have to slide them in and out. In our RV we have a sliding battery tray but I would not trust it to hold 4 6V batteries secure in a boat. Much more rocking and rolling in a boat than a RV. The problem with going AGM is the charging profile is different so you will have to probably go with all AGM on that charger including the start battery.
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Old 05-18-2019, 03:09 PM   #5
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"I want to replace the house batteries with 4 GC2s and the starting battery with??? which is the questions. Currently I have a Volvo TMD31a motor that starts easily (I hope I did not just jinx myself) I want something I can manage that would be used for just starting the motor. I am not sure on what the CCA requirement is on the volvo - would a group 31 (flooded) battery work?"

My Volvo TAMD41s (2 of them) and genset have always started from a single 4D. The last one lasted 12 years (FLA) so never stressed. Your TAMD31 is the 4 cyl version of my 6s, so should take the same or less to start.
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Old 05-18-2019, 03:33 PM   #6
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Quote:
Originally Posted by Comodave View Post
If I remember, 2 8Ds is about 440 AHs and so are 4 6Vs, or very close. I would go with 4 6V AGMs. They will fit in the same footprint as the 2 8Ds. Then you donít have to slide them in and out. In our RV we have a sliding battery tray but I would not trust it to hold 4 6V batteries secure in a boat. Much more rocking and rolling in a boat than a RV. The problem with going AGM is the charging profile is different so you will have to probably go with all AGM on that charger including the start battery.

My memory was way off. Forget what I said. Your numbers are much better.
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Old 05-18-2019, 04:00 PM   #7
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If you can make a little extra room, J305 AGMs have 312 AH per pair. Four would have almost 50% more AH than the 8Ds youíre used to. Not lightweights but MUCH easier to wrestle than the 8D beasts.

Length: 11.61Ē (295mm)
Width: 7.09Ē (180mm)
Height: 14.41Ē (366mm)

We start our Lehman 135s with a group 31 with no problems.
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Old 05-18-2019, 04:05 PM   #8
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A reminder. changing to 6V batteries remember to verify total amps. Example,
I have two Rolls 6V rated at 880 amps each, Wired up in series to get the 12V, and amps are still 880 amps. Don’t make a common mistake by assuming you’ll double the amps.
Probably allready knew this, just saying.
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Old 05-18-2019, 04:29 PM   #9
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I think six GC2s (approx 660 Ah) will fit in the space of two 8Ds (approx 490 Ah). Check that.

A single G31 may start your diesel, but if necessary two G31s would certainly work.. and schlepping the weight of individual G31s might not hurt as much as shifting a single 8D.

Were it me, I'd choose quality AGMs and bag the sliding tray, watering chores, etc. altogether.

Odyssey G31 AGMs (PC-2150) offer serious cranking amps. Lifeline makes 6V AGMs. The two brands prefer different charge voltage regimes, though, so if you need to use a single charger for both banks... Lifelines G31s would be quite sufficient.

There are less expensive AGMs out there, too; I don't have experience with those.

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Old 05-18-2019, 08:36 PM   #10
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Recently got rid of my factory boxes, replaced with a dual 8d box. In box I now have 3 Grp 31 maintenance free batt, tested when new at 1100cca each. Two are used for thrusters, the other for engine start, a 330 horse Cummins. So far so, so good. Batteries can be combined if need be. In same box is a grp 24 used to start NL 5kw gen. There is space in box, for another grp 31 if needed. Made for about 10 sg ft more storage in lazzeret.
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Old 05-18-2019, 10:06 PM   #11
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Battery questions... and suppliers?

Quote:
Originally Posted by Rebel112r View Post
Recently got rid of my factory boxes, replaced with a dual 8d box. In box I now have 3 Grp 31 maintenance free batt, tested when new at 1100cca each. Two are used for thrusters, the other for engine start, a 330 horse Cummins. So far so, so good. Batteries can be combined if need be. In same box is a grp 24 used to start NL 5kw gen. There is space in box, for another grp 31 if needed. Made for about 10 sg ft more storage in lazzeret.

Where are those Dan? Are they all in the aft lazarett under the cockpit? When I got mine, the PO had put an 8D in the ER for the engine and a GRP 31 for the genset. Thrusters are 2 8D Lifelines in the aft lazarett.

The GRP 31 died the day after I bought it and I replaced it with a GRP 27. If the engine start battery dies (doubtful) Iíll replace the 8D with probably 2 x GRP 31s or simply let my Thruster bank double as my engine start battery. Iíd love to get rid of the engine start battery in the ER. It would give me a LOT more room.
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Old 05-19-2019, 06:23 AM   #12
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Your location shows Chicago, which might require more starter cranking if you use the boat in cold weather.

Da Book (the engine service manual) will have the required CCA for your engine .
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Old 05-19-2019, 08:26 AM   #13
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Dave, they are in lazerett on stbd side. No batts, in engine space.
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Old 05-19-2019, 09:53 AM   #14
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Dave, they are in lazerett on stbd side. No batts, in engine space.

Nice.
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Old 05-19-2019, 11:28 AM   #15
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TAMD41P here (6 Cylinder, 200 hp). A #27 starts her easily..
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Old 05-19-2019, 12:19 PM   #16
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When it was time to replace my 8D batteries, I took out 3 8D and put in 8 L16 Lifeline AGMs. Three L16s fit in the foot print of the 8D, they weight less 125lbs each, and increased my battery bank. The L16s are taller, if you have the space.
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Old 05-19-2019, 12:33 PM   #17
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Least expensive golf cart batteries are at Costco.

The are Interstates.

My last 6 was from Costco and they lasted 7 years which is 1 more than the Costco ones previous to those. But that maybe due to more advanced battery charging of the inverter/charger or the alternator controller.

Purchased the Group 31 starting batteries from Costco too.

My philosophy is to purchase the least expensive house batteries and replace more frequently. I weigh batteries when I buy them to compare lead content.

Back in the 80's, I used to buy the Rolls batteries. Great batteries but very very expensive. For what they cost, multiple purchases of Costco batteries was less expensive
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Old 05-19-2019, 01:03 PM   #18
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Quote:
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Least expensive golf cart batteries are at Costco.

The are Interstates.

My last 6 was from Costco and they lasted 7 years which is 1 more than the Costco ones previous to those. But that maybe due to more advanced battery charging of the inverter/charger or the alternator controller.

Purchased the Group 31 starting batteries from Costco too.

My philosophy is to purchase the least expensive house batteries and replace more frequently. I weigh batteries when I buy them to compare lead content.

Back in the 80's, I used to buy the Rolls batteries. Great batteries but very very expensive. For what they cost, multiple purchases of Costco batteries was less expensive

I agree with you, and that is exactly what I did on my last sailboat when I needed to replace the 2 4D batteries after they finally died.

I would have done the same on my North Pacific other than the location was definitely NOT convenient for watering them. They also were located in an enclosed lazarett that also contained the diesel furnace. While I generally donít worry much about hydrogen off-gassing, I didnít think flooded batteries in an enclosed space with an inanition source sounded like a great idea. I also got a killer deal on some AGM L16s.
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