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Old 05-08-2014, 07:28 PM   #21
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Eric: here's a different approach. Consider an Optima spiral-wound 'Blue Top SpiralCell 34M'. Although AGM, being spiral-wound it is very accommodating of charging voltages--more so than other AGM forms--- and will live happily with a FLA profile. And the other advantage of spiral wound is that it delivers a heck of a cranking charge. Victron, who DON'T own Optima, specifically recommend these for thrusters, for another reason: the spiral-wound form is very shock resistant (so good if installed in a bow). My 'cranking bank' (serves to start propulsion engines, operates Sidepower 75 thruster and my davit) comprises two of these and is 7 years old and still sounds as strong as when new.
These are probably the worst of the worst. My understanding these were taken off the market, pure garbage in my opinion.

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Old 05-08-2014, 07:38 PM   #22
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Greetings,
http://www.streetsideauto.com/p/optima-8016-103/
Everyone's entitled to their opinion.
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Old 05-08-2014, 10:19 PM   #23
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Optima might have been a good choice. I've had dual Redtops in series in my diesel LandCruiser for ten years now.

But. Make sure you have a charger that can charge them. You can discharge the heck out of them. Many auto chargers won't charge them because they see the battery voltage so low that it figures it has a dead cell and decline to even try.

I think that has brought on a lot of hate towards the Optima. They think they're dead but they really aren't.
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Old 05-09-2014, 06:55 AM   #24
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>I might disagree it depends on the wind resistance in perfectly calm waters the thrusters current might be lower than say trying to do an emergency docking in 60 plus mph winds?<

Not really , the thruster operates at basically zero speed , just as bollard pull would be measured on a tug.

The motor in the thruster just spins as it can , depending on the voltage.

TIME is what heats and eventually burns undersized wiring .

The battery V going lower may raise the amperage drawn , raising the heat produced.

Most bow electric thrusters have severe time limits ,( in Da Book) till the white smoke escapes.

Weather the week point is the wiring , or the motor service time ,or battery capacity , its still the week point and will fail when overdone.

Thats why some select hyd .
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Old 05-10-2014, 10:29 AM   #25
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Okay, I'll buy the theory that the motor current draw is a constant. However as I mentioned my Thruster is wired with less than 8 (round trip) feet using #4/0 wiring. It's doesn't get much larger than 4/0. I was on the thruster less than 6 times perhaps at the most in 15 second bursts. I also have plenty of house bank/ cranking voltage and current (3) 31 series AGM Lifelines are the source.
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Old 05-10-2014, 11:54 AM   #26
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Billy- If your 4/0 cables got hot in a one minute run, I would strongly suspect the connections have high resistance, somehow. Heat generated there will move fast through cu cable (excellent thermal conductivity) so cable can feel hot a good distance from the end. But the termination is likely the heat source. Check/clean/snug connections.

Ran my boat yesterday, thruster has lots of zip. Terminal voltage now about 11v under load, vs 10 (and dropping) with tired old batt. Amazing the difference a volt makes.
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Old 05-10-2014, 12:00 PM   #27
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I have been all over the installation this only happened about 4 years ago during an emergency docking procedure in during a fast moving line of thunderstorms with water spouts. The cables are normally cold to the touch. I had my wife do a 45 second crank on the thruster against our dock wheels while I inspected all the connections. It's never happened again the thruster is as reliable as the day I installed it. The lugs are tight and covered with heat shrink which I cut away after the one smoke incident. I can only attribute it to docking under adverse docking conditions. I'll admit this should have never happened it did. It didn't take out the high current fuse either.
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Old 05-10-2014, 12:59 PM   #28
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DC motors require a lot more current to start than they do to run.

Your initial post was that you started the motor 6 times for 15 second runs.

Your test was a continuous run of 45 seconds.

Big difference.
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Old 05-10-2014, 01:06 PM   #29
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You bring up some valid flaws in my testing. Still the unit hasn't had an issue since that storm and all connections were tightened and tested.
Thank you,
Bill
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Old 05-12-2014, 01:05 AM   #30
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Can I say that Deep Cycle and dual purpose batterys have no place driving DC Bow thrusters. The issues are simple, deep cycle batteries do not deliver cranking amps for anything like the duty cycle required and although some quote outstanding CCA numbers the duty cycle is in some cases less than a second. The other problem with dual purpose batteries including deep cycle is in their in ability to recover - they dont absorb current well and need trickle charging.
In my experience thrusters will fail when the boat owner is returning home after being away and the batteries are down, there is a thought that simply running home is enough to re-charge the banks but that isnt always true.
In a series wound DC motor cranking capacity of your battery and its duty cycle is the only thing that matters.
Sometimes the cheap batterys are the good ones - good old lead acid for me.
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Old 05-12-2014, 07:59 PM   #31
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Can I say that Deep Cycle and dual purpose batterys have no place driving DC Bow thrusters. The issues are simple, deep cycle batteries do not deliver cranking amps for anything like the duty cycle required and although some quote outstanding CCA numbers the duty cycle is in some cases less than a second. The other problem with dual purpose batteries including deep cycle is in their in ability to recover - they dont absorb current well and need trickle charging.
In my experience thrusters will fail when the boat owner is returning home after being away and the batteries are down, there is a thought that simply running home is enough to re-charge the banks but that isnt always true.
In a series wound DC motor cranking capacity of your battery and its duty cycle is the only thing that matters.
Sometimes the cheap batterys are the good ones - good old lead acid for me.
Funny thing, Vetus specifies what size battery to use for their thrusters by giving an amp hour (not a cranking amp) specification and range. They also note that if the capacity exceeds the top end of that range, and the cables are larger (or much shorter) than that specified in their table, the usage time must be reduced to avoid motor damage.
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Old 05-12-2014, 08:31 PM   #32
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Funny thing, Vetus specifies what size battery to use for their thrusters by giving an amp hour (not a cranking amp) specification and range. They also note that if the capacity exceeds the top end of that range, and the cables are larger (or much shorter) than that specified in their table, the usage time must be reduced to avoid motor damage.
Vetus are wrong.
What the issue is with your comment on motor damage is like this - most providers of DC thruster make their specification based on an expected voltage loss. For example, Sidepower quote their performance in KG of thrust at 21vdc, other brands do the same so the run times are based on the voltage / amps = KG of thrust. If you increase the voltage at the thruster you also increase the current; Increase current you increase heat and therefore shorten run times (or potentially damage motor). The offshoot of all that is increase current = increase power with a shorter run time due to all being thermaly protected.
In my experience - Deep Cycle batteries have no place connected to a Bow Thruster of any brand.
I have watched my Clamp Meter tell me the story of just how poor they are 100 times.
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Old 05-12-2014, 09:04 PM   #33
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voltage / amps = KG of thrust. If you increase the voltage at the thruster you also increase the current;
You really didn't just say that did you? Really?

Vetus is wrong???
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Old 05-12-2014, 09:35 PM   #34
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You really didn't just say that did you? Really?

Vetus is wrong???
Yes I did, based on your assertion - however I believe its all about how you understand their instructions - just had a look
125 kgf - 12 V : 2.5 min. at 840 A
125 kgf - 24 V : 2.5 min. at 470 A

I read this differently and dont read into it stored amps rather I read this as capability of the battery required to deliver current. They are requesting in my opinion cranking requirements not deep cycle storage.

For the record I dont believe Vetus are incorrect. I have installed and sold many of their product (without problem) as well as Sidepower, C Marine (a good new brand) as well as fixing just about all the rest over the last 20 years or so.


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Old 05-12-2014, 11:27 PM   #35
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Well Ski, amazing the discussion you raised. I must say though, sure glad I have AGMs for the thruster given the batteries' location. Lots more to this than arguing battery types.
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Old 05-13-2014, 06:27 AM   #36
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AC motors (except universal ((with brushes))) eat power in watts. V x A = W

So if the power ,Voltage, goes down yes more amps are required.

Thats why so many air cond refuse to start in summer , low dock voltage can not deliver the watts required for it to run. The Watts are constant, as is the power.

DC and universal AC motors are quite different , feed them 120V and receive a certain HP, feed then 90V (chain saw at the end of 4 extension cords) and the HP is less , as is the amperage drawn.

Thats why they are selected for the task.

A DC windlass is similar , lower the supply voltage and the amperage is also decreased.
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Old 05-13-2014, 09:17 AM   #37
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These are DC motors and they power in watts too (V x A = watts) . So does your engine (1 horse power = 745 watts). So on an electric motor, to generate the same power, as volts increase current decreases as illustrated in the number of amps in the Vetus specs for 12 and 24 volt versions.

Look down the Vetus manual a few more pages to "The Power Supply" and you will see the battery is spec'd in ah. By coincidence I have the same manual, in mine it is page 16 in the English section.
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Old 05-13-2014, 06:52 PM   #38
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Vetus are wrong.
It takes a pretty big pair to say the manufacturer of a piece of equipment is wrong when they specify how to install or use it.

My thruster is a Key Power and it came as original equipment on the boat. It's powered by the house bank which used to be deep cycle batteries but is now AGM which are pretty much deep cycle in operation.

Regardless, it's worked just fine since I bought the boat in 2008.
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Old 05-13-2014, 07:21 PM   #39
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It takes a pretty big pair to say the manufacturer of a piece of equipment is wrong when they specify how to install or use it.

My thruster is a Key Power and it came as original equipment on the boat. It's powered by the house bank which used to be deep cycle batteries but is now AGM which are pretty much deep cycle in operation.

Regardless, it's worked just fine since I bought the boat in 2008.
I'm with you Ron, I have (3) 31 series Lifeline AGM's and the thruster has never let me down. It was installed in 2007.
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Old 05-14-2014, 06:59 AM   #40
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These are DC motors and they power in watts too (V x A = watts) . So does your engine (1 horse power = 745 watts). So on an electric motor, to generate the same power, as volts increase current decreases as illustrated in the number of amps in the Vetus specs for 12 and 24 volt versions.

TRUE , that is how they are rated for static comparison ,,my point is the HP goes down as the DC voltage decays.

An AC motor will attempt to create the HP by demanding more amps.

A DC motor ACCEPTS the fact that it creates less power with lower volts and does not demand more amps.

ON a DC motor the watts and therefore HP output change , by design.
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