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Sonoferin

posts 17

8:34 pm January 25,2012

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I am replacing all 4 8d batteries on Sea Pirate,I was hoping for some advice on selection.

A mechanic at the marina says that the 8d's are an overkill for my boat and that I should buy 4- 4D's

I read that 4D's put out 40% less than 8D's ???

I told him I have an invertor on board ..he says if the invertor is only being used intermittently then still advises the following setup

1 Group 31 as a starter

3 4D as house batteries

Any thoughts ??/

Martin Cool

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Scott Carle

posts 606

1:08 am January 26,2012

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I'm not familiar with the 8D's

I am current using 4 AGM group 31's for a total bank size of 420 amps. However we are not living on the boat. It seems like a lot of power to us though. Currently I don't have separate start and house banks. Just the one. I have two optima battery's that are the equivalent of the group 31's that will be a starting bank/secondary house bank as soon as I create a place to mount them under the pilot berth.

Ok I looked up the 8D's nice batteries. The good ones seem to average out at about 250 amp hours each which is more than double the capacity of one of my Group 31's.

The cost of a flooded version of the 8D's seems to be in the 250 dollar range while the AGM version is about 550 dollars to 600 dollars.

So if you put in 4 8D batteries you should have about 1000 amp hours.. and cost between 1000 and 2000 dollars. that is a lot of amp hours and not a bad price on the flooded end of it. I like agms as you can not spill the acid in them:) however you need a very good charger that is designed to charge them correctly or you end up with expensive dead batteries. A decent shore charger is in the 400 to 600 dollar range. The cheaper chargers in my limited experience seem to die and or kill batteries.

My current group 31's by comparison were about 300 each retail for a grand total of 1200 dollars for that 420 amp hours capacity. ( disclaimer…I didn't pay that for them.. I actually got them for around 600.) I couldn't afford 1200 for a battery bank. However the 4 8D at a 1000 for a 1000 dollars sounds like a pretty good deal.

Flip side is that many are saying to go with 6volt golf cart batteries that two of them take up the same foot print as one 8D and are easier to move. At current prices it looks like they will cost more per amp hour at 12 volts than the 8D's. I had read people saying that they were cheaper and with more capacity.. However the prices I have just been looking at are higher. 225 amphour 6v battery for 199 dollars. you would need two of them to get 12volts at 225 amp hours. so 400 dollars for 225 amp hours or 250 for 250 amp hours with an 8D…

I don't envy you putting them in and out of the boat though. Those are big monsters. When I put our Group 31's in and out we too a 10 inch wide board about 5 or 6 ft long and layed it up on the battery tray ledge and over the engine. Put the batteries on the board and slid dragged them up and down the board to get them in and out of the engine compartment. One person in the galley and one up in the engine compartment and it went pretty fast.

I believe based on conversations I have heard that most Interstate Battery dealers will deliver batteries on to your boat for a minimal delivery charge. Not sure if they will install them for you though:)

here is an example interstate battery for 188 dollars. :) much better price than I was seeing on my first search. however im not sure this is a deep cycle or just a starting battery.. You would want a deep cycle version of the 8D.

Scott

http://www.atbatt.com/product/…..D-MHD#tabs

Scott Carle DE38 Cutter s/v Valkyr

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svbodhran

posts 42

4:46 pm January 26,2012

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Certainly the one group 31 battery will be sufficient for a starter battery. As for your house bank,you really need to determine what your needs are. How much power do you use in a day? You mentioned and inverter. How big is it? What kind of loads do you put on it? What kind of power generation do you have? solar? wind? If you've got lots of power being generated,then you don't need as big of a battery bank. If I remember right Nigel says to size your bank to about 4 times your daily usage. This way you'll rarely discharge your batteries below 50% and when you run the engine to recharge them,you'll only have to run it up to the 80% charge rate at which point the batteries ability to accept a high amp charge goes down significantly.

I'm very happy with Bodhran's power setup right now. I have to run the engine if it stays cloudy for more than 3-4 days in a row,otherwise the solar keeps the batteries up above that 80% charge rate. My main power consumers are the fridge (Engels,very low power draw) and the inverter (used mainly for the computer,but also for tools and such.) I've got LED lights and run some fans,but neither of those are very big power consumers. Generally I figure that I use about 70 amp hours a day. I've got 4 Trojan T105 golf cart batteries for a total of 450 amps at 12 volts. Using the 4:1 ratio I would only need 280 amp hours,so my bank is 60% bigger than the minimum. I've got 190 watts of solar mounted on an arch with nothing to shade them except for the back stay,but of course there's lots of factors that come into play with solar power generation. I've also got a balmar 70 amp alternator with a 3 stage regulator on it which is a little undersized for charging my bank. You should have an alternator capable of providing 25% of the total capacity of your bank,but in my case the solar picks up the slack.

So as to your question about the 4Ds vs the 8Ds. The difference in capacity varies from battery to battery,but is more like 20% than 40%. Just looking at the lifeline agm batteries,the 4D has a 210 amp capacity and the 8D has a 255 amp capacity. So your old bank was probably in the 1000 amp capacity range and the one that's been suggested is in the 600 amp range. So if your daily usage is less than 150 amps,3 4D batteries should be fine. If you use upwards of 250 amps a day then you should replace the 4 8Ds.

Hope that helps,

Jason

DE32 Bodhran

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Scott Carle

posts 606

9:56 pm January 26,2012

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I meant to ask.. do the 8D's really fit in the built in battery trays on the DE's?

scott

Scott Carle DE38 Cutter s/v Valkyr

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Sonoferin

posts 17

7:35 pm January 28,2012

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Scott Carle said:

I meant to ask.. do the 8D's really fit in the built in battery trays on the DE's?
scott

Yes they fit all around the shelf at the rear of the engine room

Certainly a lot to think about. If there isnt a big difference in amps from the 4D's maybe thats the way to go.

I could use the space where the last battery on the right goes to custom fit a small microwave.

I am not sure about the solar panels or the invertor. Never got to try it all out last year cause of work.

Im going to replace the batteries and just try to figure out what kind of power I am using this year while sailing.,

Off the top of my head….Stereo,GPS,Lights are all LED in the cabin now. BTW I found a place in

China that sold me bulbs with 24 led's for $4.00 and they were legit !!!

I got an anchor LED for $7.00

anyway thx for all the info I am trading a website for the batteries at this marina where IM at so have to keep the price fair for the trade.

Martin

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Scott Carle

posts 606

10:37 pm January 28,2012

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I just wasn't visualising that amount of batteries. contrast my boats 4 group 31's. I still have 280 lbs of batteries back there. I have thought about adding more but installing them at the bottom of the storage area under the pilot berth to keep the weight low. The port side of the engine compartment where you have the D8's is just open empty space except for the compressor for the fridge up against the cabinetry in the forward end of the shelf. Weight varies but I am looking at about 640 lbs for 4 D8's back there. Does that much weight there affect the fore and aft balance of the boat much? I think I would go for two of them back there for 320 lbs and 500 amps capacity…250 amps usable. I wish that there was a place near the water tanks to mount batteries. You could put a lot of weight there without affecting the balance of the boat.

Scott Carle DE38 Cutter s/v Valkyr

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svbodhran

posts 42

10:51 pm January 28,2012

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I cut out the insulation around the locker under the aft end of the starboard settee and made put my batteries there. On a DE 32 there's just enough room for 4 golf cart batteries in a line on the inboard side of the locker. It keeps the weight pretty centered in the boat and it's a heck of a lot easier to check the water levels. Here's a pic from when I first put them in:

Jason Rose

DE32 Bodhran

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Scott Carle

posts 606

9:50 am January 29,2012

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I like that. I don't think I want to lose that storage space but that is a very nice and accessible place. I have AGM batteries so am not concerened about having to add water. However they are not fun to put in and out of the engine compartment at 70 lbs each. I would love to shift that weight forward in the boat though like you have:)

Scott

Scott Carle DE38 Cutter s/v Valkyr

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