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Marine Contactors for series/parallel 12V battery momentary 24/36V


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Apropos the trolling motor/thruster thread, trying to figure out how to get momentary 24 or 36 VDC from a normally parallel 12V bank. 

A set of marine DPDT contactors would do it, or one 4PDT if such exists, so far not locating anything that seems suitable: 

 Double throw aspect is important as both high and low sides are being switched, and we don't want to put 24V on 12V buss if the ground switch hung up, or short a battery if a high side hung.

Can use a 4 or 6 pole with double throw and parallel the poles, but all need to break before make together.  

Specification:

  • 12VDC coil < 100mA 
  • > 100A DC current rating for windlass and trolling motor
  • > 48V DC voltage rating 

Prefer latching to avoid standing current, but NC side for 12V parallel is sufficient

something like this: (battery fuses & disconnects not shown for simplicity)

The apparatus would be located inside the forepeak, batteries are in the anchor rode locker, so humidity is a given, but not immersion. 

some type of sealed contacts would be preferred to reduce corrosion issues. 

image.png.031e94b42d01ee2ce34dcad6f802ae52.png

 

Any suggestions on vendors and source? 

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You are on to something here. I envisioned something along these lines 15 years ago on a hybrid electric catamaran I built. I wanted to be able to charge in parallel and then draw from the bank in series.  Everyone said I was crazy but it would have sure help that system. Twelve 4D 12 volt batteries was the big challenge. Lots of potential for fireworks in that! 

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1 hour ago, Rasputin22 said:

You are on to something here. I envisioned something along these lines 15 years ago on a hybrid electric catamaran I built. I wanted to be able to charge in parallel and then draw from the bank in series.  Everyone said I was crazy but it would have sure help that system. Twelve 4D 12 volt batteries was the big challenge. Lots of potential for fireworks in that! 

I can find DPDT relays that go to 80 A, but for the windlass "stall" load, I would want higher, though arguably the 24 & 36 Volt batteries would be in parallel and some careful wire length might give enough "ballast" to protect their NC contacts. 

 

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You might take a look at Warn winch contactors... or Gigglepin often has some upgrade bits. Warn was moving to solid state last time I was shopping for 4x4 winches.

Both have 12V and 24V products.

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17 minutes ago, randii said:

You might take a look at Warn winch contactors... or Gigglepin often has some upgrade bits. Warn was moving to solid state last time I was shopping for 4x4 winches.

Both have 12V and 24V products.

I have, but they don't have Double Pole stuff in what I was finding and depend on a chassis ground, which would not work in the stacking case. 

 

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The issue for a industrial application like this motor starter contactors etc will be cost as you get into higher load ratings.  Based on 3 12v cells you would need 6 independent NO contacts that ideally are set up in mechanical make or break configuration. You could do it with regular 12v continuous duty relay coils like you see for starters etc.  And small control relays for the interlock logic.  The danger being a component failure could make a welding machine.  Blue sea does some nice solid state battery switches as well and are might be able to do a one off controller.

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Ocding on relay logic projects is a weakness for me, I think you could probably do this for under $100.  I'll draw something up after work. You could run a control multi to a locker with the relays and have some configuration of a selector switch or switches to cover interlocking.  Schneider Electric is a good place for process controls.

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Crazy. So no house power while docking? Possibility of huge fireworks from bad switching? No way.

Seems simpler to rewind the motor for 12 V.

Are the batteries dedicated to the thruster? If so, consider putting the complexity on the charge side of the setup. Lower currents. Safety.

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5 hours ago, El Boracho said:

Crazy. So no house power while docking? Possibility of huge fireworks from bad switching? No way.

 

Certainly have 12V house power,  just 1/3 of amp hours which for "docking" is fine. Advantage of returning to Parallel is easier charging. 

The reason to have the multi-pole relays is to prevent "bad" switching. Any single pole scheme is vulnerable. A "Frankenstein"  Knife switch or modern multi-phase disconnect  is the equivalent for manual use. 

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4 hours ago, Crazy Horse said:

What about a Bosch or similar series parallel switch, used for 24 volt start and 12 volt run? https://www.amazon.co.uk/Bosch-0333300003-Series-Parallel-Switch/dp/B00C7OS9BY

that's in the right direction, as I decode their schematic it's a Double pole double throw "form C" which is good, but only 75A Automotive rated, which is a bit different than Marine. 

image.png.84c33404a62a0e6380734795f983c8c3.png

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Sidepower makes what you want already, I believe... but it is pretty pricey if memory serves... they made it to be able to run their 24VDC thrusters on 12VDC boats....

Edit: dealing a little bit with storm cleanup today, so I can't verify if it REALLY checks all your boxes- but it seems that the bits must be out there... https://www.imtra.com/Collateral/Documents/English-US/Products/Series_Parallel_Box_Manual_12-24V_2002.pdf

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3 hours ago, suider said:

Sidepower makes what you want already, I believe... but it is pretty pricey if memory serves... they made it to be able to run their 24VDC thrusters on 12VDC boats....

Edit: dealing a little bit with storm cleanup today, so I can't verify if it REALLY checks all your boxes- but it seems that the bits must be out there... https://www.imtra.com/Collateral/Documents/English-US/Products/Series_Parallel_Box_Manual_12-24V_2002.pdf

That's pretty much it. Thanks! figured somebody had to make them. 

S

 

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What are the independent loads and uses of the three voltages?  It sounds like you have a 12v house bank and the trolling motor is 36v@100amps.  What is the 24v for?  There are a couple lower cost possibilities for isolation and safe selection to get the three, depending on load some for all three continuous, obviously much easier with two.

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Trolling motor is either 24 or 36. No other 24 v load, but it’s a step on the 12v cascade. 

 

No doubt if I had 24 v I’d find things to run off it, like wiring a table saw for 220 vs 110, less sag etc. 

Old windlass is 12v, new could be 24 etc. 

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Ok that makes sense. Depending on your house electricial load sticking with a 24v bank may make sense.  Use a DC to DC converter for nav electronics. No switching one battery charger/inverter. Most stuff like refrigerators solar controls etc are either or 12-24 now.  The cost of a converter is likely less than all the switching controls like something imatra sells, which are just there anchor relays in a box with some controls over the top.  We have a 12 and 24 bank 12 for nav and 24 for hotel.  I over engineers it and used a newmar 30 amp to supply the hf radios and 2 meter.  It's pretty bullet proof and clean stable power.

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FWIW, if you do go to a 24V bank, it's very easy to get up to 100A at 12V at a reasonable cost with one of these:

http://www.cooperindustries.com/content/public/en/bussmann/transportation/products/power_conversion/battery_equalizers/21100x00_converterequalizer.html

No fans, no contactors, pretty much bulletproof.

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On 11/1/2019 at 8:04 AM, LionessRacing said:

that's in the right direction, as I decode their schematic it's a Double pole double throw "form C" which is good, but only 75A Automotive rated, which is a bit different than Marine. 

image.png.84c33404a62a0e6380734795f983c8c3.png

I run this Bosch series/parallel switch on my boat and it works really well.  It switches my batteries to run a 24V bow thruster and charge from a 12V alternator.  The 24V contacts are huge, rated at 200A or more IIRC, the 12V contacts are smaller and rated at only 75A, but my 55A alternator doesn't charge that fast anyway.

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