Carver 3307 33AFT Alternators upgrade

[mmccorkell]

Hi

I have purchased a carver 33 AFT from a friend of mine who originally shipped the boat from the USA, so I know her history and have always admired her. She’s the perfect boat for us as a family with loads of space, especially on the Flybridge.

I’m looking to replace my two 12-volt 51-amp Prestolite alternators on my boat ( 1 left hand & 1 right hand)

The engine is a Crusader V-8 454 CID/7.4 Litre - Model 454. I would like to upgrade them to the highest amperage output possible, I have the physical room to do so, and my battery banks are 2 x 840 ah

I was looking at the 10SI as per link and image below as someone said they are compatible but would welcome your views/ recommendations


https://www.dbelectrical.com/products/1 ... -wire.html


Thanks in advance Mark
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[bud37]

Welcome to the forum......question..... First, why do you believe you need to make such a change ? Are your existing two alts not keeping up ?

[mmccorkell]

Hi

Thanks for the welcome, and yes you’ve asked a very good question.

At present the boat is moored in the non-tidal section of the River Thames just outside London, and although we will be using her in the open sea in the future. The plan for the next 4-5 years is to keep her on the Thames.

We have mains hook up at our mooring to charge the batteries, but we spend up to 3 weeks at a time on the boat, and may only cruise at 5 knots for 2-3 hours most days. so my thinking was my idea was to use a high output alternator to do the bulk of the charging


We have a Kolher generator so we could charge the batteries from it, but due to the noise we would prefer to only use the generator as a last resort


Cheers Mark

[bud37]

Source of the post We have mains hook up at our mooring to charge the batteries, but we spend up to 3 weeks at a time on the boat, and may only cruise at 5 knots for 2-3 hours most days. so my thinking was my idea was to use a high output alternator to do the bulk of the charging

You have have quite the battery bank, 1680ah total ?...anyway my advice, before you decide on new alternator sizing read up on battery bank recharge rates at different states of charge, it is an interesting subject as there are no free rides with the put and take of battery power, there is a point where more alt power is not necessarily better but you will have to decide for your bank setup where that point is.....good luck with your project..

[Midnightsun]

Welcome to the forum.

Question? You sure about that 1840 ah battery bank? That would be huge. Could you be confusing CCA with AH? regardless, a larger alternator is always a good thing. That being said and considering the price of gas nowadays especially in the UK, I will have to assume 5 knots is most likely going to be your standard cruise speed. Problem is slow speed equals slow speed alternator revolution and poor charging characteristics. There are alternatives to correct this by installing different size pulleys on the alternator to increase their revolution at low engine speeds. May even be a better alternative not to mention cheaper than installing a high output alternator which may produce less than the original at slow speeds. Just something to keep in mind before jumping in. A little reading here will explain things more clearly. https://alternatorparts.com/alternator-pulley-size.html

My suggestion is to rebuild the originals and install smaller pulleys. Cheap and effective.

[mmccorkell]

Hi Bud/Midnightsun

Thanks for the feedback and advice its really appreciated

At present I have 8 x 105 ah batteries in each battery bank, one of the battery banks is new but the other is due for replacement this year, with this in mind and knowing that at 5 Knots even with a smaller pulley wheel I’m never going to get fully capacity out of the alternators.

I have shower power at my mooring, but there is very little shore power available at overnight moorings across the non-tidal Thames, and with 2-3 of cruising at 5 knots each day, any size alternator is not going to provide me with enough charge

• Keep the alternators and install the smallest pulley wheel as I can
• Buy a Victron MultiPlus Inverter Charger 12V/3000VA/120A which will give me 120amp charging capacity
• Keep the good battery bank and remove the old bank and make 2 x 420ah Battery banks
• Run on the onboard generator for 3 hours a day whilst cruising which will give me around 360ah of charge which is enough charge for at least 24 hours use

Ref the boat loading
• The heating is now via an Eberspaecher diesel heater and the airtronic heating/AC has been removed
• There’s a full-size fridge freezer which draws about 100 watts 230v
• Microwave
• Lighting is all LED
• 2 No. Toilet macerators 2 TVs
• General laptop/phone chargers


Cheers Mark

[Viper]

You might want to consider putting your alternator budget into a solar power array. On sunny days, they'd maintain charge in the presence of some of the smaller loads you might have on a regular basis such as lights, fridge, radio, electric toilets, computer, phone chargers, etc. There's a few threads here on the subject.

BTW, there are alternators designed to put out full load at lower rpm but if you manage your power consumption and charging habits, you'll do fine without them. Install a digital battery monitor and monitor your usage and the state of charge, then top up as needed when the solar panels can't keep up.

[km1125]

Always thought it would be a cool project to rig an alternator with a planetary drive... essentially a two-speed "transmission" for the alternator. At low crank speeds, it might be a 1:3 ratio but at high speeds it would drop down to a 1:1.5 ratio and use a magnetic clutch that would kick in around 2000 rpm on the crank. That way you could get full output of the alternator at any engine RPM you needed to run at.

There's a guy in another forum who's using a hydraulic pump on the engine and hydraulic motor connected to an alternator to do something similar. With some valving between the pump and motor, he can adjust the speed on the alternator so he can get full output even when the engine is at low RPM.

[plittle2005]

Hi, fellow Irishman, I have the same boat here in the US, and will be using mine in the same way, so this thread is informative. I love this forum!

I have 4 Group 27 12v FLA 90 AH batteries between the engines, down between the stringers, with cover boards over them, using up all the room that I have.

Can you describe your battery arrangement? You seem to have many more. I would like to increase capacity. How was it done in your boat?

Thanks very much
Phil Little, '92 33 AC
Weehawken NJ USA