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Old 03-07-2021, 10:12 PM   #1
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Side Power Thruster - 564 Amps?

Wow, they were NOT kidding,

I was reviewing my electrical data yesterday using the Victron Portal after a short 3 hour trip (to see how my new alternator regulator was doing) and I ran across this deep current demand...

564 amps?....wow, I better be more careful using those monsters...the battery temp went up 3 degrees in 10 seconds.

I didn't know where that came from until I realized that I was docking the boat at 13:55
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Old 03-08-2021, 05:52 PM   #2
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It does get your attention. The instantaneous current was probably higher than what your meter could capture. One reason to really make sure all connections are tight and without corrosion.
On a previous boat just after I bought it, the lead-clamps melted off the batteries after using the thruster for 10 seconds. Never had that problem again after ensuring clean and tight connections.
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Old 03-08-2021, 07:46 PM   #3
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Which model SidePower are yours?
Thats exactly the kind of info I was looking for for my thrusters. Mine are also 500A fuses for each thruster.
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Old 03-08-2021, 07:55 PM   #4
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We have side power 95ti DC units.
You have a good source for anodes for these?
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Old 03-08-2021, 09:06 PM   #5
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I expect the shunt is rated for max 500a. I'd be a little concerned running 800 amps through it, and wouldn't expect it to be accurate at those currents.

You might consider a dedicated thruster battery bank. That takes the stress off the house system and better supports the thruster.
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Old 03-08-2021, 09:11 PM   #6
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Mine are the older SP95s
Anode is SM71190A 1-3/4" Dia (alum) and readily available from Defender, Boatzinc.com and some others.
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Old 03-08-2021, 09:18 PM   #7
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Quote:
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I expect the shunt is rated for max 500a. I'd be a little concerned running 800 amps through it, and wouldn't expect it to be accurate at those currents.

You might consider a dedicated thruster battery bank. That takes the stress off the house system and better supports the thruster.
I have a thruster bank that serves my B & S thrusters - currently AGM 8D.
I recently moved my engine start to this bank to make my house purely house.
Plan when replacement needed is to go with a pair of AGM Gp 31 as I'm done with handling 8Ds and see no advantage as price, performance, capacity are at least equal with 2 - Gp31s.
I believe I would see my Raymarine GPS/MFD drop out from low V is tied to thrusters as I have seen it with starting when start was on house and I used one 8D. I have 2 for house and now have them paralleled. Likewise plan for replacement is 4 - Gp31 AGMs.
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Old 03-10-2021, 07:32 AM   #8
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The high amps is probably why the unit has operating time limits.

High amp (actually any amp) draws can be helped by using a star washer under the captive nut on the feed cable.

Amps makes the connections hot so they expand , the star washer pushed the connection back to tight.
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Old 03-10-2021, 10:40 AM   #9
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This conversation makes me wonder about electric boats. What’s the difference in these motors and setup vs electric as a primary drive?
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Old 03-10-2021, 10:42 AM   #10
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This conversation makes me wonder about electric boats. What’s the difference in these motors and setup vs electric as a primary drive?

Electric drive would typically have higher voltage to keep the amps down and also better motor cooling to allow for continuous operation. A thruster can often save some weight, bulk, and cost by down-sizing components as it only needs to run for a fairly short period, then gets time to cool.
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Old 03-10-2021, 10:53 AM   #11
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Another note to keep in mind when choosing which batteries to use with a thruster:
the motor is essentially a big starter motor. Deep cycle batteries need not apply!
If your house bank is made up of deep cycle batteries, your thruster(s) should have
their own separate starting-type batteries.
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Old 03-10-2021, 10:58 AM   #12
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Another note to keep in mind when choosing which batteries to use with a thruster:
the motor is essentially a big starter motor. Deep cycle batteries need not apply!
If your house bank is made up of deep cycle batteries, your thruster(s) should have
their own separate starting-type batteries.

In general, yes, starting batteries are better suited to thruster use (where they supply a large burst of power for a short time, then get topped off). However, if the house bank is big enough that the thruster draw isn't (relatively speaking) too large, it'll be able to supply the high draw of the thruster just fine even though the batteries are deep cycle and not as good at putting out large bursts of power.
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Old 03-10-2021, 10:58 AM   #13
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Originally Posted by KnotYet View Post
Another note to keep in mind when choosing which batteries to use with a thruster:
the motor is essentially a big starter motor. Deep cycle batteries need not apply!
If your house bank is made up of deep cycle batteries, your thruster(s) should have
their own separate starting-type batteries.
Actually many AGMs work very well for both.
You will notice Duracell (East Penn) AGMs spec both CCA and AH.
They confirmed AGM GCs perform comparable to GP31s for both start and deep cycle.
The typical FLA plate thickness & free space below plate differences dont apply with AGMs.
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Old 03-10-2021, 11:44 AM   #14
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A graphic example of the inrush current when starting an electric motor and a great illustration of why the folly of using repeated "bursts" of thrusters is bad practice.

My boring old lecture to learn to maneuver your boat with the rudder and the engine instead of relying on thrusters threatens to drop another large rock in the site's pond...
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Old 03-10-2021, 11:46 AM   #15
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A graphic example of the inrush current when starting an electric motor and a great illustration of why the folly of using repeated "bursts" of thrusters is bad practice.

My boring old lecture to learn to maneuver your boat with the rudder and the engine instead of relying on thrusters threatens to drop another large rock in the site's pond...

A good thruster controller would ideally control that inrush at least somewhat.



As far as use of thrusters, I agree. I see way too many people using them as a crutch, or as their sole means of steering in tight quarters and just laying on the thruster for repeated long blasts. In my mind, they exist to help you do things the boat just can't do without them. Use them when needed, but you've gotta know what the boat can do without them and when you need them.
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Old 03-11-2021, 12:08 AM   #16
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Quote:
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Another note to keep in mind when choosing which batteries to use with a thruster:
the motor is essentially a big starter motor. Deep cycle batteries need not apply!
If your house bank is made up of deep cycle batteries, your thruster(s) should have
their own separate starting-type batteries.
That's an oversimplification. My house bank is 4 8D batteries with 1500 MCA apiece. They're wired up in series/parallel at 24V so 3000 MCA at 24V. I think they'll be okay.
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Old 03-11-2021, 06:36 AM   #17
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"I expect the shunt is rated for max 500a. I'd be a little concerned running 800 amps through it, and wouldn't expect it to be accurate at those currents."


A shunt with too much juice put thru becomes a Fuse!
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Old 03-11-2021, 08:06 AM   #18
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I have a strong thruster. When first learning the boat, I used it for a few seconds one to three times while docking. Now, pride that keeps me away from the controls. The thruster is used only once in a while for "fine tuning".
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A good thruster controller would ideally control that inrush at least somewhat.



As far as use of thrusters, I agree. I see way too many people using them as a crutch, or as their sole means of steering in tight quarters and just laying on the thruster for repeated long blasts. In my mind, they exist to help you do things the boat just can't do without them. Use them when needed, but you've gotta know what the boat can do without them and when you need them.
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