Repowering Help - Page 3 - SailNet Community
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post #21 of 33 Old 10-04-2011
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take a look at this paper
http://www.exide.com/Media/files/Dow...s%20Manual.pdf

a battery can output lower current for a long period of time the way to make this work is to have a large number of cell and a high voltage with a low draw

i know this will sould like a lot of batteries but I want to start with a 240 volt dc bus
this will take 20 batteries. starting out with 280 volts and drawing down to 200 volts if the current is low I can draw 5-7 amps with an average of 240 volts for 24 hours this is about 2hp average over that time. the drive I am using needs 175 volts dc min so I can draw the batteries down lower, a newer drive is in the design phase and will allow even lower voltages to be used. This is an experiment keep in mind I just want to invest some time and capitol into this as I don't like any of the current system I have read about.

the motor is 20 Hp 3 phase AC 200 volt so It will give me all the power my atomic 6 had and more, of course at high power the battery life goes down faster. I don' know what the results will be but it is worth the effort to find out. I am looking for a nice quiet gen set to add to this , and a wind turbine and also some solar panels. I any one want to come for a look while we do this. you are woelcome to come see as we move along with the project. I am looking for all your good ideas.
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post #22 of 33 Old 10-04-2011
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Please keep us posted, I am not sure your budget and plan are doable with that technology, but we shall see...

Please be careful as DC voltage can be very unforgiving at those levels...and the components often fail in spectacular ways.
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post #23 of 33 Old 10-04-2011
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20 Hp 3 phase AC 200

What is the frame size and rated 20 HP RPM on this motor ?

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post #24 of 33 Old 10-04-2011
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A 12 volt battery is fully charged at about 12.8 volts resting. The lowest you want to take them to for long life is 50%, or about 12 to 12.1 volts. They are considered dead at 10.5 volts.

As you will have 20 batteries take your lower voltage of 200 and divide by 20. That equals 10 volts and you will never get there running a motor. 50% SOC for your massive bank is about 240 - if you go much lower the batteries will have a very short life.
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post #25 of 33 Old 10-04-2011
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Quote:
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A 12 volt battery is fully charged at about 12.8 volts resting. The lowest you want to take them to for long life is 50%, or about 12 to 12.1 volts. They are considered dead at 10.5 volts.

As you will have 20 batteries take your lower voltage of 200 and divide by 20. That equals 10 volts and you will never get there running a motor. 50% SOC for your massive bank is about 240 - if you go much lower the batteries will have a very short life.
And if you run them all the way down to 10 (200 for the bank) there is no guarantee they will recharge even once.


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post #26 of 33 Old 10-04-2011
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Exactly.

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post #27 of 33 Old 10-04-2011
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And if you run them all the way down to 10 (200 for the bank) there is no guarantee they will recharge even once.
thus my comment about a spectacular failure of a component...

and without proper fusing or current limiting hardware, the "motor" may spin once or twice and then the batteries may flash/incinerate/smolder...that current has to go somewhere.

And if there is a weak/marginal cell or poor manufacture...well about the same result.

the exide paper is just their spin sheet....nothing new there.

the bigger question is how are you going to convert all this DC to 3phase 200 VAC that the motor you mention requires...or did I miss something there..?
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post #28 of 33 Old 10-04-2011
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Well

The DC to AC deal would happen in the control and is how its done in the most modern forktrucks

A big issue on a motor that size is it will need a powered cooling fan which will eat some amps

Even a AC VFD drive goes AC to DC back to AC to perform its tricks

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post #29 of 33 Old 11-10-2011
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boat is in the building we rented in newport parts are on order i will keep you posted as we make progress
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post #30 of 33 Old 11-10-2011
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Regardless of who you are dealing with, a Kubota has got to be the best bang for the buck
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