How to set fire to your boat...

[celandine]

Steve,

Having had this type of equipment fitted last season, I have been following your posts with interest, (but not from a knowledgeable position.) Could you please clear up one small point : ie If my alternator is only capable of producing say 55 amps, how can it suddenly start producing these dangerous 200 amp currents when the demand from the windlass comes on? No doubt there is a simple reason that I have failed to grasp.

Thanks

Mick

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[Strathglass]

Mick
The 55 amps quoted is the maximum current that the alternator (in ideal circumstances) can supply into the battery.

When you connect a heavy load to that battery, be it a starter or a windlass, the the current demanded (typically 200 amps) from the battery by that load can be far in excess of this 55 amps.
Any under-rated component in the path to the load from the battery, be it a VSR or even a piece of cable, will present a fire risk.

This does not exclude the use of lower rated (Lucas ?) VSRs to provide split charging when correctly installed.

Steve's postings indicate correctly that care should be exercised when heavy loads are involved.

IMHO this type of posting is typical of the forums and one of the reason why they are so popular.

Iain



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[andyball]

When the voltage of (usually) the starter battery reaches a certain level (13.2-13.5 commonly) the relay effectively links the starter bank & the house bank. The high currents can exceed alternator output because the current can come from the battery and the alternator.




I had a home-made vsr on my van for years (cheap durite regulator switching a 50Amp relay) ..... don't think I'd have one for a big domestic bank & starter though.

I agree that manufacturers/suppliers should warn buyers of the possibility of problems if a large load is connected to a flatish domestic bank w/o suitably sized cable & relay.

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[Guest]

Depends if mistake is ...

made in following the instructions of fitment to the letter - therefore supplier is in error, or making own mistake in not complying with suppliers fitting instructions. I get the impression from SC's post that he followed the suppliers instructions.
So if you buy an article and fit it as per suppliers words - are you then at fault - as you seem to regale at SC ....

The forum is to eductae, advise, assist and generally inform. Having been also at the end of anothers vitriolic stick - I fuly understand from both sides ......

If you disagree with SC ..... do it nicely without the 'stick' .....

I for one am very interested in battery charge / connection systems and want to learn from others successes and failures ... not from tantrum laden bullshit !!!!


<hr width=100% size=1>Nigel ...
So WHAT does the EU really stand for ????/forums/images/icons/cool.gif

 

[tome]

Re: What do you mean \"...

Cor Steve, you're getting into a bit of a stew here!

Having re-read your posts I now believe that you may have the windlass powered from the service batteries. This is another no-no. They should be powered from the engine start batteries and the engine should be run when using the windlass. The service batteries will not provide sufficient cold cranking current to drive a windlass if they are deep-cycle cells.

You should also make sure that the engine batteries have sufficient capacity. Lofrans recommends at least 150Ah for their Cayman 1kW windlass.

If you had the system correctly wired, the state of the domestic batteries does not matter and the danger you warn of doesn't arise.

And on your later rant on ACR regulators don't assume there aren't others who know it's the outside brush that wears.

Regards
Tom

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[celandine]

Thanks Iain and Andy.
In my naivity I thought that the relay and the wires from the alternator only carried charging current. I think I am going to have to track down a circuit diagram before I can really get my head round this one.
Mick

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[andyball]

Re: charging 2 banks

There's a reasoned discussion about charging 2 banks within the "electricity on board" pdf download on Victron's site.

A 1MB download, & I don't want to clog up this thread, so for those with slow connections the relevant part is <A target="_blank" HREF=http://www.windywoo.f9.co.uk/charging2banks.doc>here</A> for a few days at least.



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[halcyon]

I personally find this a bit across the board statement, as we have been designing, and supplying split charge relay systems now for 25 years.
To the best of my knowledge we have not sufford the above problem, from day one the units were designed for SC's problem, or engine starting, by droping out at 13 volt, and included a fuseable link at Sealine's request back in 1983. This has, to the best of our knowledge worked ok, as we have had fusable links blown.
In the current units we produce there is a interface circuit that monitors startermotor ( or the winch motor could be added in ) which drops out the relay when the solonoid is engaged and before a load comes onto the circuit. Added to this the current 80 and 100 amp units will carry 300 and 500 amp for 30 seconds, and if this was used with 15 or 25 sq mm cable there should never have been a problem. This cable size is also used to allow for the link starting facility that is built in, which would have made the winch no problem.

I would be grateful if Steve would not tar all of us with the same brush, beleive it or not we put in 100 of hours thinking about charging, it's problems and the user, all seems a little wasted now.

Brian

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[JamesDavis]

Re: Reasonable question

Wow! What a debate. I am in the process of rewiring my boat and was sold a VSR for my proposed system. 32 ft sailing boat with 2 batteries, only high load device being the starter motor. I'm not a liveaboard and boating consists of weekend sails with a lot of engine use with a couple of Channel crossings a year. I wanted to dispense with the selector switch for the batteries as it was a bit prone to disasters with the children and the constant going below to switch over was a pain and often forgotten. I've drawn up a wiring diagram. Would anyone fancy a browse over it and some advice? E-mail a address and I'll get it to you.

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[MedMan]

Re: What do you mean "...

The service batteries will not provide sufficient cold cranking current to drive a windlass if they are deep-cycle cells.

Hmm! My windlass is connected to my service battery bank (2 x 120Ah) and I have never had any problem at all in 15 years of use. I do, as you suggest, always run the engine whilst using the windlass.


<hr width=100% size=1><A target="_blank" HREF=http://www.yachtretreat.com>http://www.yachtretreat.com</A>

 

[Chris_Robb]

Steve - not sure that

it is such a problem.
I have had a charge splitting relay for years. However the main differnce is this.

The Winch is connected to the starter battery - the alternator is fitted to the starter battery. Therefore no problem can occur with this set up (I hope!)

A serious problem which can occur is on starting. As these relays will connect either way - if your domestic bank is over 13.5 with solar charging or a battery charger (therefore connected ) then when you start the engine a huge current could flow the other way. This is a recognised danger and a relay breaker is fitted (to the ignition circuit), which drops the relay the moment the key is turned. The unit I have is from a little cornish makers KDD and is the only one I have seen with starting circuit break. Some others I have looked at could therefore be dangerous.

I believe that splitting diodes can burn out in the circumstances you describe - can they not? most are only rated to the alternator output.

I do think that the prime problem here is that the manufacturers should warn that ANY heavy current devices should not be fitted to the domestics if the alternator charges the engine battery, explaining the danger clearly. I suppose if you think about it, it was an accident waiting to happen.



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[MedMan]

Re: Steve - not sure that

I believe that splitting diodes can burn out in the circumstances you describe - can they not? most are only rated to the alternator output.

No they can't. Current cannot flow from one battery to another through a pair of splitting diodes - that is the whole point of them. They are one -way valves that allow current in (from the charging source) but not out.

<hr width=100% size=1><A target="_blank" HREF=http://www.yachtretreat.com>http://www.yachtretreat.com</A>

 

[halcyon]

Re: Steve - not sure that

If a diode fails it will fail short or open circuit, if it fails short circuit it conducts like a piece of wire.

Brian

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[OzGirl]

Heavy current items

Back to the the subject, I agree heavy current items should never be connected to the domestic bank. On our boat, both the thrusters and the windlass are connected to the starter batteries. The two starter banks and the domestics are charged by two separate alternators, one 12V the other 24V.

<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by kimhollamby on 09/02/2004 08:56 (server time).</FONT></P>

 

[pvb]

Oi!!!

"Poor" I'd agree with, but not so much of the "old", please!

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[pvb]

No, most VSRs are now mono-directional...

Most of today's VSRs are in fact mono-directional; that is, they only close on sensing voltage on one side. The BEP unit which Steve Cronin has referred to is certainly mono-directional.

In contrast, most battery combiners are bi-directional: they will close when either end rises above a preset voltage.

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[MainlySteam]

Re: What do you mean "...

<<<My windlass is connected to my service battery bank (2 x 120Ah) and I have never had any problem at all in 15 years of use>>>

It is, as Tome says, bad practice.

You will suffer greater voltage drop from deep cycle batteries than you will from a proper cranking battery when a load is placed upon it due to the much thicker plates of the deep cycle battery. Once the surface charge is taken off the difference can be significant. That can be lessened by running the engine but unless one has a high output alternator capable of supplying the whole of the windlass draw plus the draw of the batteries charging (which may be 200 amps if say 1kw windlass and 500Ahr of batteries under charge) the voltage will still sag more than a cranking battery under charge (also, the cranking battery will normally only ever draw a few amps from its, say typically, 60 amp alternator as they are always close to full charge).

That may not be too onerous but in my mind it should be avoided. For three reasons in parallel to the above:

- the day you have to haul with no engine, the house voltage will sag much more than the engine cranking battery votage

- the engine cranking battery is almost always fully charged

- the house batteries when part discharged will sag the DC line voltage even with the engine running if they are capable of charging at a rate higher than the alternator's output.

Why is this important? The greatest cause of failure of windlasses is low supply voltage to their motors.

John

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[tome]

Re: What do you mean \"...

I don't think that the fact this hasn't caused you any problems that you're aware of changes anything. John has explained very clearly why it is best practice to avoid deep-cycle cells for heavy loads. If you wish to ignore this, then that's fine but please avoid triumphalising your 'getting away with it' as proof that there's something wrong with the advice given.

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Oh, I see you've pulled your post!<P ID="edit"><FONT SIZE=-1>Edited by tome on 08/02/2004 09:44 (server time).</FONT></P>

 

[halcyon]

Re: OK, Steve...

The problem that Steve has had was high lighted by Sealine back in 1983, when thay had a cable catch fire after a relay stuck(not our unit, but another manufacturer that stopped making them years ago ). For that reason and to prevent further danger a fusable link was added to all units, now we have an interlock with the startermotor ( the original problem ) or to a winch in Steves case, that drops out the relay if engaged to stop the problem. New models have equipment rated to cope with high loads, thus avioiding Steve's problem.
Blocking diodes, or diodes in general can fail, and do, either open circuit, or short circuit, in the latter case they will conduct like a piece of wire.
We are looking at a volt drop of 40 milli volts ( 0.040 V ) per 100 amp on the new units, a blocking diode will drop 0.6 to 1.2 volt. This effectively halfs your recharge levels compared to a relay, thus needing smart alternator regulators i.e. Adverc, or battery sensed alternators to cover the volt drop.
Since around 1990 we have always recomended either a battery in the bow for winches or bow thruster, or to run these of the engine battery, which is normally better charged and the engine will be running. As a preference I go with a battery in the bow, avoids high current on long runs up and down the boat( this a hazard in it's self unless cables are very well installed ) and avoids the volt drop in cabling, which intern increases the current drawn by the winch, thus increasing volt drop more.
In recent years the amount of equipment fitted to boats has grown dramatically, 10 years ago bow thrusters were almost unknown, now everyone has one. Thus if uprating specifications of existing boats, bow thrusters, winches etc, check your current system. It may not have been designed to meet the loads you put on it.


Brian

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[kds]

Re: What do you mean \"...

Now I really am scared witless !!
I am going to complete my 29 ft. long keeler with two identical, semi-traction batteries, 1/both/2/off switch, ( the lower voltage battery will surely draw the grater current when charging !) Sterling alternator control, hand windlass boat hook and stop reading all these technical, contradictory and far too heavy for my simple mind discussions.
And now for a glass of red .....

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