Charging a 48V bank?

[jdege]

I'm thinking about installing a pair of Torqeedo Cruise 6.0 outboards on my boat. These are 48V motors, and Torqeedo's battery prices are absurd, so I'm looking at something like 4 of SOK's 12V 100Ah marine batteries wire d in series. 4×12V rather than 1×48V or 2×24V because the lower individual weight will make them easier to handle when installing them or removing them from the boat. These are going to be pretty much permanently installed, except for removing them during the off season.

Eventually I will want to be able to charge these in a number of ways:

• Shore power
• Solar panels
• Suitcase gasoline generator
• Regen when sailing

I'm going to be adding things to the boat over a number of years, rather waiting until I have everything in place before I splash.

Right now, I'm trying to figure out what charger/chargers to use, when plugged into a single 30A AC shore power pedestal.

Ideas?

 

[sunshine_eggo]

Do the current limits of the SOK meet the needs of your motor(s), particularly any surge currents?

 

[Supervstech]

I'm thinking about installing a pair of Torqeedo Cruise 6.0 outboards on my boat. These are 48V motors, and Torqeedo's battery prices are absurd, so I'm looking at something like 4 of SOK's 12V 100Ah marine batteries wire d in series. 4×12V rather than 1×48V or 2×24V because the lower individual weight will make them easier to handle when installing them or removing them from the boat. These are going to be pretty much permanently installed, except for removing them during the off season.

Eventually I will want to be able to charge these in a number of ways:

• Shore power
• Solar panels
• Suitcase gasoline generator
• Regen when sailing

I'm going to be adding things to the boat over a number of years, rather waiting until I have everything in place before I splash.

Right now, I'm trying to figure out what charger/chargers to use, when plugged into a single 30A AC shore power pedestal.

Ideas?

A grand isn’t a terrible price for a 25Ah 48V battery designed for a boat, but,yeah I agree, sok should be a much better design…

 

[jdege]

Do the current limits of the SOK meet the needs of your motor(s), particularly any surge currents?

The Torqeedo Cruise 6.0T has a max draw of 125A.

The SOK batteries have a max continuous of 100A.

So I'd either need to choose a higher current battery, wire two sets of SOKs in parallel, or not drive the motors at full power.

Truth is I don't expect to run the motors at full power. Full power significantly increases energy drain for a minor increase in speed.

But I'd need to understand the consequences of accidentally hitting full throttle, before I decide to not worry about it. The SOK will handle 200A for up to three seconds, after which it will shut down. The big question is how long after before it resets?

Or can the Torqeedo throttles be configured to set a max current draw, so as to keep below 100A, no matter what my idiot nephew does with the levers?

 

[jdege]

A grand isn’t a terrible price for a 25Ah 48V battery designed for a boat, but,yeah I agree, sok should be a much better design…

Torqeedo's Power 48-5000 cost $5200, not $1000.

And they're LMO-NMC, not LiFePO4.

 

[Supervstech]

I wouldn’t use 12V batts in series for a motor load…
I would get a 48V battery with a 200A BMS… way simpler.

 

[jdege]

I wouldn’t use 12V batts in series for a motor load…
I would get a 48V battery with a 200A BMS… way simpler.

A 48V 100Ah battery is going to weigh 100 pounds. Getting the into and out of the boat, and down into the remote corners where they're going to have to fit, is far from simple.

 

[Supervstech]

A 48V 100Ah battery is going to weigh 100 pounds. Getting the into and out of the boat, and down into the remote corners where they're going to have to fit, is far from simple.

Which is why you build a 25Ah battery… like they sell.

 

[sunshine_eggo]

The Torqeedo Cruise 6.0T has a max draw of 125A.

This is likely not the case unless it's listed as a LRA (locked rotor amps) value or a surge.

The initial flow of current to a motor is typically 5X higher than its maximum operating current. The winding of the motor essentially have zero resistance until the flow of current induces a field that "pushes back" at the incoming current.

Truth is I don't expect to run the motors at full power. Full power significantly increases energy drain for a minor increase in speed.

Doesn't matter. There will still be large surge.

 

[Bluedog225]

Cool project. What boat?

The juice on the regen may not be worth the squeeze.

 

[Bluedog225]

A 100 amp fast blow fuse would be a fail safe. Give a way to explore the limits. Though it might get a little pricey.

 

[jdege]

Cool project. What boat?

The juice on the regen may not be worth the squeeze.

It's a Vaitses/Herreshoff Meadowlark - a 37' shallow-draft ketch.

Torqeedo's marketing promises Regen when using their batteries. But I'd not expect much except when pushing hull speed on long passages, which for me is a someday maybe.

 

[jdege]

The initial flow of current to a motor is typically 5X higher than its maximum operating current. The winding of the motor essentially have zero resistance until the flow of current induces a field that "pushes back" at the incoming current.

So I'm going to need to find the specified max initial inflow, before I make decisions.

It's not in the material I've found, yet.

 

[Bluedog225]

Sweet ride! 2500 lbs min? My gut says this is not a feasible project without a lot more juice.

 

[OzSolar]

I'm thinking about installing a pair of Torqeedo Cruise 6.0 outboards on my boat.

I'm in the very preliminary stages of daydreaming about an electric boat project. I assume you've already seen the Elco boat motors? No idea if they are any good or not, just thought I mention them in case you haven't seen them.

 

[jdege]

I'm in the very preliminary stages of daydreaming about an electric boat project. I assume you've already seen the Elco boat motors? No idea if they are any good or not, just thought I mention them in case you haven't seen them.

Elco makes inboard motors, IIRC.

My boats was designed to have two props, each driven by a 5hp gas engine. Somewhere along the line she was converted to a single offset prop driven by a 27hp diesel. Given that the diesel isn't in great shape, and that she really needs two props to steer at low speeds, I've been looking at alternatives.

Rather than adding a second prop, and then two inboard motors, I'd been thinking about external pod drives. Both ePropulsion and Torqeedo make these. But ePropulsion's are propped and geared for light boats at high speeds. Torqeedo's Cruise 6.0 is the only one designed to efficiently push displacement hulls at low speeds.

Then I started thinking about their outboards. They're essentially the same motors and props as the pods. But they're easier to install, easier to work on, easy enough to replace with a gas outboard should I find myself somewhere where getting parts is a problem.

And I can install them without removing the diesel. Which means minimal downtime during the sailing season. I can wait until fall to pull the diesel.

 

[jdege]

Sweet ride! 2500 lbs min? My gut says this is not a feasible project without a lot more juice.

12000 pounds. But she's shallow and narrow, she doesn't need much to drive her. (As in 8' beam and 20" draft - plus leeboards

She was originally powered by two 5hp engines. The motors I'm considering are 6kW each, roughly 8hp.

 

[BobR]

The Torqeedo Cruise 6.0T has a max draw of 125A.

The SOK batteries have a max continuous of 100A.

So I'd either need to choose a higher current battery, wire two sets of SOKs in parallel, or not drive the motors at full power.

Truth is I don't expect to run the motors at full power. Full power significantly increases energy drain for a minor increase in speed.

But I'd need to understand the consequences of accidentally hitting full throttle, before I decide to not worry about it. The SOK will handle 200A for up to three seconds, after which it will shut down. The big question is how long after before it resets?

Or can the Torqeedo throttles be configured to set a max current draw, so as to keep below 100A, no matter what my idiot nephew does with the levers?

Make sure your batteries can handle the amp draw at full throttle; or there is a way you can limit the amp draw. The last thing you want is to be trying to work off of a lee shore and to lose your motors. You don't have time to wait for your bms to reset.

Lee Shore Dangers and How To Escape | Life of Sailing

Leeward has a few applications in sailing and understanding each is kind of important. Two terms in particular, “Sailing in the lee”, and “sailing by the lee” can both be quite dangerous.

www.lifeofsailing.com

 

[BobR]

I really don't see the need for two motors on a little sharpie like the meadowlark. I would go with one motor. Save your $s and have some fun!

 

[jdege]

I really don't see the need for two motors on a little sharpie like the meadowlark. I would go with one motor. Save your $s and have some fun!

She has a single prop, offset, and tucked up along the keel. She has no prop-walk to speak of. She simply doesn't steer.

She was designed to have two props, and I think she really needs two props.