Bow thruster power

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wayneakp

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Hi all

Can anyone tell me what the recommended Ah / CCA is for a Nobels thruster - it has 12V 9 stamped on the motor - guess 9 HP. I have the manual but it does'nt give any information regarding batteries.

many thanks

Wayne
 
wayneakp said:
Hi all

Can anyone tell me what the recommended Ah / CCA is for a Nobels thruster - it has 12V 9 stamped on the motor - guess 9 HP. I have the manual but it does'nt give any information regarding batteries.

many thanks

Wayne
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It's very unlikely to be 9hp at 12v. That would need more than 500amps and some fearsome batteries and cabling. Any other data? More likely to be say 4 or 5hp
 
jfm said:
It's very unlikely to be 9hp at 12v. That would need more than 500amps and some fearsome batteries and cabling. Any other data? More likely to be say 4 or 5hp
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Even so, a 4 / 5 HP Vetus type 75 / 95 is pulling 500 / 600 amp, the OP needs to find the actual requirements of his system, he is or can be playing with high power. The other consideration is some manufactures use the battery size and / or connecting cable to limit current draw of the motor.

Brian
 
jfm said:
It's very unlikely to be 9hp at 12v. That would need more than 500amps and some fearsome batteries and cabling. Any other data? More likely to be say 4 or 5hp
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Crumbs. Page 9 of this pdf from Aquafax does indeed suggest that Nobels do a 12v 9hp bowthuster, with a 6.6kw power requirement, which in turn is 550a, as you suggest.

http://www.aquafax.co.uk/pdfs/05_cat.pdf

Cheers
Jimmy
 
Thanks all - that is indeed the item - I missed the rest of the info on page 11 though :o - thanks 2 x 150 it is then
 
wayneakp said:
Thanks all - that is indeed the item - I missed the rest of the info on page 11 though :o - thanks 2 x 150 it is then
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But Wayne if you're buying dedicated batteries just for the b/t then why not do it in 24v not 12v? Much better, and less fire risk, and you'll save on 50sq mm, jeez, copper
 
jfm said:
But Wayne if you're buying dedicated batteries just for the b/t then why not do it in 24v not 12v? Much better, and less fire risk, and you'll save on 50sq mm, jeez, copper
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Thanks - the thruster is already fitted and is 12v. Next decision is which type of battery to go for???
 
Just before you rush off and rob your nearest railway of cable and nobble the Tescos electric forklift for its battery.

Fit a dedicated battery as close as possible to the thruster. Providing the cable run is short then you won't need stupid cross section cable. It will be chunky but only standard off the shelf stuff from an automotive supplier or decent chandlery. Try Uxbridge Boat centre in Waterloo road Uxbridge. A great source for proper fit out materials and inland prices. They are old school so it's a visit or a call on the phone rather than online.

Cables only need to be monster thick when you extend the cable run in order to avoid voltage drop. Fitting the dedicated battery means 12 volts and plenty of cranking power. The charge feed to the battery will only need to cope with a relatively small current so can be of more realistic proportions (read cheaper!).

Although the current requirement sounds huge it's only for a very small period of time. Look at the cold cranking amp quoted on the battery rather than the amp hour capacity. In theory a 100 amp hour battery could deliver 6,000 amps for a minute (in theory).

You obviously have a relay arrangement controlled by a small current fitted locally to the thruster so again the control wires can be skinny.

I hope that explains things.

A good manufacturer will use very substantial cable rather than a secondary battery because that is the ideal solution but it's very expensive and retrospectively running the 2 cables may be a nightmare due to weight and lack of flexibility.

Henry :)
 
Why are you fitting 2 batteries?

I would have thought a single 100ah decent Cold crank rated battery would do the job. It's getting a constant charge (I hope) whilst you are underway. You're only going to run the thruster for a few seconds at a time. In theory a 100AH battery will power a 500 amp thruster for 20 minutes. I know it doesn't work quite like that but 10 seconds is a walk in the park.

Henry :)
 
henryf said:
Why are you fitting 2 batteries?

I would have thought a single 100ah decent Cold crank rated battery would do the job. It's getting a constant charge (I hope) whilst you are underway. You're only going to run the thruster for a few seconds at a time. In theory a 100AH battery will power a 500 amp thruster for 20 minutes. I know it doesn't work quite like that but 10 seconds is a walk in the park.

Henry :)
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Manufacturers specification is 2 batteries, he is pulling around 900 amp, 8 HP Vetus pulls 800 amp @ 12 volt and the OP has 9 HP.

Brian
 
So I think I have found why the thruster is weak. The spec calls for 2 x 70mm2 cables and there is only one so we are seeing quite a volt drop. At the weekend I plan to run another pair of cables in 70mm. I cant get it clear in my head if I need to fuse each +ve cable at separatley, or jointly - any comments please?

cheers

Wayne
 
You can fuse them individually or jointly. Doesn't really matter. Obviously the individual fuses would need to be 50%x the nominal fuse required, and the new cable that you're running needs to have identical conductivity to the existing cable, not merely similarish. If any doubt on that, fit a joint fuse
 
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