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Bowthruster batteries


Barge Maria

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Hi all

 

I would value some guidance from those forumites that are familiar with battery technology

 

I have just had fitted to my 106 year old Dutch barge an electric bowthruster, 24 volt, 20 hp. Yes, we are all getting older!

 

After some help and guidance from Mr Tony Brooks of this parish the wiring and fusing is all in place, and the unit is up and running. It is a Duco unit for anyone interested, Dutch, good quality, but little by way of technical input for the installation.....luckily the boatyard new how to weld it in!

 

Anyway, in my design for the batteries, I took the view that semi tractions would be the way to go in order to give capacity for long bursts of thrust (this i is running the risk of turning into a Carry On script....) so I bought 4 Yuasa batteries of 6 volts and 225 amp hours, wired in series. They are the same ubnits as our old friends the Trojan T105 but are a bit cheaper.

 

Up and running and the thrust is good, but a bit weaker than I expected. Also noticeable is a distinct warming of the battery terminals after a 3 or 4 second burst. The current is between 500 and 600 amps based on the fusing suggested by both Duco and Tony B. Cables are not really warm, but batt terminal are.

 

I am now thinking that I made a bit of a boo-boo and should have used truck starter batteries with a CCA of c.1000 and capacity of c.180 A/hrs or so, wired in series to give 24 volts.

 

Would I be right in thinking that the semi tractions are not up to providing c.600 amps for such a purpose?

 

I can easily change, and use the Yuasa batts for another purpose in the domestic battery bankl, but before I spend again I would value thoughts.

 

Thanks for reading this far...................

 

Tim

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My first reaction is that 600A is a LOT of current for a 225Ah bank!

 

It certainly is.

 

20hp = 20 x 746 watts = 14920 watts

 

14920 watts / 24 volts = 622 amps

 

This needs a battery installation to traction motor standards (truck starter may be adequate if the thruster is only used in short duration)

 

(and your 24V is probably dropping quite a lot anyway - hence reduction in expected force - but a voltmeter across it and measure the drop - expect 14 to 18 volts)

Edited by Tiggs
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This is all about short bursts of high amps... a bit like a car starter battery :)

 

Lots of cars have 60-80Ah batteries, but they have High CCA capabilities, so can push out lots of Amps for short periods of time, (a few seconds for most cars)..

 

Say you use a bowthruster very excessively, perhaps for 10 minutes total, in 30 second bursts of 600A..... that would be one sixth of an hour at 600A, or 100Ah. Not ideal, but not really a big deal for a charged 225Ah bank, as long as it has a high enough CCA.

 

So... for a bowthruster, or a windlass, or both, a high CCA battery bank is the thing.. i.e. typical car starter batteries.

 

Unless I'm missing something??

 

I used to have a 200Ah Lucas leisure battery for my bowthruster and windlass at the front of a seagoing yacht.

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The hot battery terminals make me suspect they are carrying a far higher current than the battery designers imagined. I think sharing the load with more batteries (so each supplies less current) would help. However I would also go for starting batteries.

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On the trip boat, we have a 24v large Vetus thruster, and always use truck starter batteries, as other types haven't been up to the use.

 

We can only use 3 second bursts maximum anyway, or the contactors start welding themselves together (something which if I ran the company rather than just being a skipper I would probably change!)

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Batteries often have an internal fuse, worth checking with the manufacturer if yours have and it's value. If the terminals are getting warm it may be the fuse getting hot in which case it might not last long. I think that the fuse is not normally replaceable, so if it blows the battery is scrap.

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Definately use 2 large truck starter batteries the ones with both terminals at one end, they are designed to give lots of power for short bursts as opposed to traction batteries that are designed to discharge slowly for long periods.

 

Neil

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Yes you are correct in thinking you have bought the wrong batteries. Your bowthruster motor will be taking more current than a typical starter motor so you definately need starter batteries with a CCA rating. These have a greater number of thinner plates to supply the higher currents needed.

 

Suggest either doubling up with present semi-traction batteries with another pair in series (which will reduce the current draw from each) with power taken diagonally from the bank, or switching to starter/truck batteries. TBH with that size thruster running at 24 volts, you probably need four 12 volt 110 Ah batteries (or equivalent) anyway.

 

Hot terminals suggest a high resistance connection to the cable or inadequate cable cross-section. If you are convinced there isn't a mechanical issue here try doubling up on the cable size. My smaller Nobels thruster uses two 70mm2 cables for both positive and negative feeds as recommended by manufacturer.

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Those semi traction batteries are squealing in pain! That current is a LOT for them. Full starter duty batteries would be happier, yes spiral wound ones would be better still.

 

If you wish to afford it now, seek out some full traction batteries. Do be certain that the charging system is adequate, as with a car battery, getting charge used replaced quickly is important and the long cable from engine room to bow tube is usually a killer for hing currents.

 

600A x 5 seconds isn't a lot in Amp hours (About 1 ! ) But putting that back will cause a volts drop down the cable from the engine room.

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I'm using my engine start batteries to supply the bowthruster, been good upto now, I'm on 24v, have two 664? 125A/hr truck batteries in series.

Batteries are in engine room and have used 95mm cable.

About 25 meters out&return. Bowthruster is vetus 75kg, it takes about 200A at 24v. When measured at the motor terminals, we got about 18v, but it seems happy enough.

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I'm using my engine start batteries to supply the bowthruster, been good upto now, I'm on 24v, have two 664? 125A/hr truck batteries in series.

Batteries are in engine room and have used 95mm cable.

About 25 meters out&return. Bowthruster is vetus 75kg, it takes about 200A at 24v. When measured at the motor terminals, we got about 18v, but it seems happy enough.

Blimey, those cables were probably more expensive that the bow thruster!

 

Surely it's better to have the BT batteries close to the motor at the bow and then you can get away with thinner charge cables from the stern. My system has short 50mm2 cables from batteries to motor and the charge cables running from the stern are only 16mm2. This is for a 12v system. There is obviously some voltage drop but because there is plenty of time to charge and i don't overuse the BT the batteries stay charged.

 

Also, my twin alternators split the charge between the start battery alternator and BT batteries. The idea is that (unlike the domestics), the start battery will be fully charged straight away so that all the charge can then go to the BT batteries.

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Blimey, those cables were probably more expensive that the bow thruster!

 

Surely it's better to have the BT batteries close to the motor at the bow and then you can get away with thinner charge cables from the stern. My system has short 50mm2 cables from batteries to motor and the charge cables running from the stern are only 16mm2. This is for a 12v system. There is obviously some voltage drop but because there is plenty of time to charge and i don't overuse the BT the batteries stay charged.

 

Also, my twin alternators split the charge between the start battery alternator and BT batteries. The idea is that (unlike the domestics), the start battery will be fully charged straight away so that all the charge can then go to the BT batteries.

 

My configuration is the similar, a couple of batteries (spiral cell) at the bow end with two charging cables (mine are 40mm) running from a Voltage sensitive relay that's connected to a bus bar (bus bar also has the alternator / house batteries).

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Well, yes and no,I didn't want a duplicate set of batteries to maintain just for the bowthruster,and as the starter batteries have a similar short duty cycle,I decided to use them.

Got a 100 meter drum of 95mm cable

off a mate of mine,only thing is the cable is 600v grade heavy rubber insulated and about an inch in diameter, but beggars can't be choosers.

I'm working in Finland this week,but when I get home I'll have a go at measuring the voltage drop out of curiosity.

Sometimes the relays stick on mine too. Can they be dressed up or are they sealed units?

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We've got a Nobels 10hp on a 24v system. 2 x Optima Yellowtop Batteries (75ah each but in series for 24v). They were in boat when we got it in November and are approx 5yrs old. They power both the engine starter as well. Still show 25.6+ volts at rest.

 

https://www.tayna.co.uk/Optima-Yellow-Top-Battery-YTS-5.5-P9099.html

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I was going to use batteries in the bowthruster compartment, but it's half full of ballast bricks,and I didn't like the idea of yet more batteries to keep charged,and a long way from my charging source too.

Was pricing up cable from local suppliers, cef etc, and getting a fright. Batteries would have worked out cheaper, but asking around the cable turned up for next to nowt.

We all deserve a bit of luck occasionally. It's suprising how people give you stuff for the boat.

I was given a little generator last week,spark is very weak, and it wont start... I'll have a fiddle with it when I get home. I'm sat in a hotel bar in kokkola, Finland, bored out of my mind as you may have guessed.

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