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Old 26-09-2011, 10:11   #1
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Electric Drive

I'm new to this forum, and new to electric drive. Installed an SolidNav Explorer with a double bank of Odessey 1800 and smart chargers last year. Our old Benz diesel had given out. As we do mostly day sailing, are moored in a marina with shore power, this seemed an ideal set up.

Once set up, we had some questions for our supplier in Seattle, but both he and SolidNav seem to have vanished and we feel marooned.

The info that had been prvided was for a 27' Ericson with a claimed 50 kn mi per charge. Accounting for our heavier boat we had hoped for about a 35 kn mi. range per charge. We are getting 1/4 of that at the very reasonable low speed of 3 kn (20 A or 2kW draw). At 30 A we do 4 kn for 10 minutes and then the whole system "throttles" down to a stall. Reverse will work instantly, forward works again after a few minutes.

Without teck support, marine mechanics trained for fossile fuel propulsion, know little more than we do. Any electrical engineers among us sailors?

Any help is appreciated.


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Old 26-09-2011, 10:13   #2
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Re: Electric Drive

Greetings and welcome aboard the CF, Alfred.

Sorry to learn of your difficulties.

FWIW: See our earlier discussion ➥ SolidNav Explorer

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Old 26-09-2011, 11:51   #3
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Re: Electric Drive

Welcome to the forum Alfred...
I hope you can find some technical assistance here.
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Old 26-09-2011, 14:34   #4
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Sounds like a controller fault. Or merely your batteries are poor. At 218 ah you don't have a lot of capacity.

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Old 26-09-2011, 15:33   #5
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Re: Electric Drive

They aren't a subsidiary of Solyndra...are they?

Sounds like you need mo' batteries
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Old 27-09-2011, 07:10   #6
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Re: Electric Drive

I might be able to help, but need some clarification.

You say you have a double bank of Odyssey 1800 batteries. They are rated at 214Ah @12V. How is your double bank wired? In parallel for 428Ah @12V, or in series for 214Ah @24V?

You say at cruise of 3kts you draw 20A or 2kw. For 20A to be 2kw, the voltage would have to be 100V, and it seems that your battery bank is either 12V or 24V, so there is some discrepancy somewhere. What instrument is reporting the 20A and 2kw power draw?

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Old 27-09-2011, 07:42   #7
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Re: Electric Drive

Here's some real quick engineering on your drive system. Hopefully it will shed some light on the problems you are having.

I'll assume you are drawing 2kw when motoring at 3kts. 2kw is equivalent to 2.6hp, and it's believable (just barely) that 2kw could propel your boat at 3kts. As a comparison point, a typical electric bow thruster will draw 200A and lightly push a bow around, so it's believable that the same power could move you forward at 3 kts.

I'll also assume your battery bank is paralleled for 428ah @12V. That would result in a 160-200A battery draw depending on what the actual operating voltage is. I'm guessing your reported 20A draw is a typo and that it's actually 200A.

At 200A draw, you batteries will run for about 60 minutes (actually less) before they are 50% depleted, and 50% depletion is typically what one would design for for reasonable battery life. 60 minutes at 3kts is a traveled distance of 3nm, not 35.

If the draw is only 160A, you would last about 80 minutes for a traveled distance of about 4nm.

To travel 35nm, you would need approximately 10 times the battery capacity that you currently have.

I must be off somewhere in my assumptions because you are actually getting more distance. I'm be happy to rerun the numbers once you setup is clearer.

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