Relay burnt out & leisure batteries dying...

[sociable_hermit]

Having sorted out the mains wiring on my boat, with some very helpful advice from people on here (Arnot and Gibbo in particular), it seems the 12V side is now in need of attention.

 

My boat spends most of its life in a Marina plugged into a shoreline. Some may recall that last year I decided to abandon using my 3-way fridge on anything other than mains, as the 12V never does much anyway and the gas installation was dodgy IMHO, plus changing bottles all the time was becoming a chore. I didn't have the money for a new fridge and in any case I couldn't find anything exactly the same size (it would appear Dometic fridges have 'grown' slightly over the years) and that would have meant rebuilding the kitchen. So, keep the fridge but make it mains only. The downside was that when away from the Marina, the fridge would have to be powered from the inverter, which would probably hit the batteries quite hard. However given that I'm only out for about 6 weeks of the year (not consecutively) I thought that would be ok. It worked fine for the last two trips of last year.

 

However this year things started to go wrong. On the second night of our trip to Nuneaton the inverter had stopped working by the morning. I checked the battery levels and they were slightly down but not alarmingly so. I topped one up in the morning and the other at lunchtime and nursed the boat along using the minimum power we could for the rest of the week. Plugging the mains charger in when we returned, it could not charge the batteries sufficiently to drop back onto float.

 

Investigating today, I checked the levels again and they were ok. Someone has borrowed my multi-meter and not returned it (isn't that always the way?), but I do have one of those cheap car battery testers, and that indicated 13.5V. However the battery charger still hums away continuously at full pelt and won't complete the cycle and go back onto float. I also found that my 33RA relay is badly melted. Mysteriously, in trying to figure out how it was wired, I've also found that the Kestrel alternator manager / battery boiler I have in the engine bay appears to be disconnected, although I'm damn sure the LEDs used to light up. I've called on professional engineers at least twice to carry out work in the engine bay, but would someone really tinker like that and not tell me?

 

Worse, I cannot see how the present installation works. I can only presume that it is wired direct from the alternator to the relay to the batteries, but it is hard to see. The old wiring to/from the Kestrel is still in place but disconnected (grrrr...) just to add to the confusion. It takes me back to my Alfa owning days.

 

I don't know enough about split charge relays and alternator controllers to work out what is going on. How do these things work?

 

And would the relay burning out cause the batteries to die or is it more likely that dying batteries caused the relay to burn out? Should I just replace the relay and the batteries and hope for the best, or is it time to strip everything out and start again? What should I be testing when I get my meter back, and how?

 

The batteries are at least 2 years old and may have been life expired anyway. The relay is a Lucas unit which may have failed anyway. But it's funny how everything has happened at once.

 

Edited to add: there could, of course, be something wrong with the charger as well.

 

I don't know where to start, really. Suggestions please.

Edited September 4, 2010 by sociable_hermit

[sociable_hermit]

I've posted something about 12V electronics and no-one wants to use it as the starting point for an arguement?

 

Are you all feeling all right?

[ditchcrawler]

I've posted something about 12V electronics and no-one wants to use it as the starting point for an arguement?

 

Are you all feeling all right?

OK Ill go first,

Relay burnt out, batteries failed to charge, fridge and inverter flattened them to about 10 volts when the inverter cut out and killed them. Just a thought.

[blodger]

I would replace the relay first off and I am sure that advice on here would be to fit a better one. 2 year old batteries should still be 80% OK and I would re-wire and test alts etc without the 'boiler' and sort the 'boiler' out from first principles next before thinking off replacing. Easier said than done!

[sociable_hermit]

Ok, so the old batteries finally giving up the ghost would possibly have had that effect on the relay when we started the engine up and attempted to recharge?

 

That's good news for me, as it suggests that I can change the batteries and the relay and everything should still be ok until I can investigate tidying up the 12V wiring properly and maybe investing in some better kit.

 

My main concern was that the relay had fried due to some sort of fault and that had then knackered the batteries. Because if that's the case then it'll happen again, but this time to a brand new relay and a brand new pair of batteries...

[blodger]

Relays give up the ghost for a variety of reasons but mainly because they were not really up to the task in the first place. I do not think the relay packed in because the batts have had it. The batts may not have enjoyed the continuous landline charging regime and may well be unable to now stand up without. Nevertheless, I would just renew the relay first and make sure that has a positive effect and not do everything at once. Monitor the battery SGs and voltages a bit before deciding to replace; they might do you another winter alongside yet.

[sociable_hermit]

I would replace the relay first off and I am sure that advice on here would be to fit a better one. 2 year old batteries should still be 80% OK and I would re-wire and test alts etc without the 'boiler' and sort the 'boiler' out from first principles next before thinking off replacing. Easier said than done!

 

Ah, they're at least 2 years old, in that they came with the boat, and I've owned it for 2 years. Well, 2 and a half, now I think about it.

 

I've bought another Lucas relay as a quick like-for-like swap, simply because I knew which wires went where. As it's impossible to trace where they go next (except the big red lead to the battery bank) I'd not be 100% certain about wiring up another relay until I could be sure what is what. But yeah, point taken, the Lucas component is cheap and nasty and in time I'd prefer something better.

 

The Kestrel is a bloody nuisance as I cannot see whether it is partly or totally disconnected. I want to rip it out as I suspect it's just confusing me unnecessarily, but am afraid to do so in case that kills the lot. More confusingly, the Kestrel is wired into a small Durite relay half way up the wall which could also be a split charge relay. However the two wires from it to the alternator are both disconnected, apparently deliberately. This is strange as I'm sure it was working when I first got the boat, and I haven't disconnected it. However I have to work on the basis that, at the moment, the Lucas relay is the one doing the work. How do I know this? Because it melted...

[sociable_hermit]

Relays give up the ghost for a variety of reasons but mainly because they were not really up to the task in the first place. I do not think the relay packed in because the batts have had it. The batts may not have enjoyed the continuous landline charging regime and may well be unable to now stand up without. Nevertheless, I would just renew the relay first and make sure that has a positive effect and not do everything at once. Monitor the battery SGs and voltages a bit before deciding to replace; they might do you another winter alongside yet.

Ok, thanks, that makes sense.

 

The main reason I'm worried about the batteries is because the charger won't drop out of the equalising stage. That can't be doing the batteries or the charger any good, although admittedly every 12V thing on the boat is still working!

[blodger]

Just re-read the OP and I wondered what sort and ampage mains charger and whether you croc it to the batt terminals or if it is hardwired in?

Too much is made of the age of batts mine are eight years old and will suffice until the wife wants to use the washing machine when we are on hols again.

I have a Stirling alt controller and I think there is a relay within the LED box. It sounds as though yours is external. I have not come across the Kestrel but wonder if it is one of Pete Hopley's of Acorn chandlery Manchester way?

[sociable_hermit]

Just re-read the OP and I wondered what sort and ampage mains charger and whether you croc it to the batt terminals or if it is hardwired in?

Too much is made of the age of batts mine are eight years old and will suffice until the wife wants to use the washing machine when we are on hols again.

I have a Stirling alt controller and I think there is a relay within the LED box. It sounds as though yours is external. I have not come across the Kestrel but wonder if it is one of Pete Hopley's of Acorn chandlery Manchester way?

Yep, spot on - Acorn Engineering, Manchester.

 

The mains charger is a 20A Stirling 'pro-budget' charger. I know they aren't very popular on here but it has worked well up until now.

 

Edited to say, it is hard-wired in, rather than croc clips.

Edited September 4, 2010 by sociable_hermit

[blodger]

I have the same 20a Stirling Charger does stirling but the fan is getting noisy. I am not a fan of hardwiring chargers though I suppose it has its merits for single bank users, etc. I presume that there are no problems in that as that's been OK for 2 yrs or more. Although I am confused as I am not aware that the budget chargers do a (4th step) equalisation charge. I have a 20 or 25a Amperor though that does every 10th or something charge up.

 

Perhaps it is the sustained load, although not you fridge as that's now on AC, that is stopping the charger taking a rest and going on float. Is there something else amiss?

 

It also ocurred to me that when the relay burnt out probably the windings connected to the battery shorted draining the batts(I would have thought this should primarily affected the starter battery?), and that you would have felt an alt load on the engine in consequence when you were last out. There are lots of little things that aid diagnosis and the experts will be along in a bit but I think they hesitate these days because of the flack they get when they categorically jump in with their knowledge.

[Keeping Up]

The Kestrel is the original "battery boiler" and is now so obsolete that its best state is "disconnected".

[sociable_hermit]

The Kestrel is the original "battery boiler" and is now so obsolete that its best state is "disconnected".

That's fair enough. I just wish that whoever disconnected it had done so properly, and removed the unit and the accompanying relay and the redundant wires. It makes it very hard to figure out, when you have two of everything. Especially when at least some of the wiring still seems to be reliant on connections through the redundant kit.

 

I think the most likely scenario is that the batteries are fading and the inverter finished them off, which caused the relay to burn out when the alternator attempted to make up the difference. I'm not convinced there was any form of dead short - I think the batteries are knackered because they dropped low and then didn't get any charge for 3 days because the relay burnt itself out. On that basis we did well to get back at all so I suppose I should be grateful.

 

P.S. The Sterling mains charger has only 2 settings AFAIK, equalisation (flat out) and float (trickle). It can't get itself to the trickle stage which says to me that the batteries are shot, though it could be the charger has a defect as well.

[blodger]

The Kestrel is the original "battery boiler" and is now so obsolete that its best state is "disconnected".

I am interested in your statement since I like simplicity and from what I recall Peter Hopley's device was but with a trimmer so that you could determine your own level of 'boiling'.

The Sterling's have some software or switching to allow for different batt types and the Advercs do a bit of on & off with up & down cyling of the upped voltage.

Is any of that superior to being able to adjust the regulated voltage yourself to suit your circumstances?

It seems to me you have to know what you are doing with any 'boiler'.

Today's conventional wisdom is that modern alts do not need upping controllers provided you are not using split charge diodes.

However, low volt regs still abound and it is handy to be able to get more out of your alt.

I would not disconnect a functioning alt controller but have it switched so its there when the occasion warrants. etc.

So to me 'Keeping Up"s opinion is bad advice

[sociable_hermit]

The advice in the Acorn manual is that "the current level shuld be set to within 10% and 15% of the ampere hour capacity of the batteries." I have two 110A leisure batteries so that's about 33A max. Funnily enough the highest charge rate is normally 30A.

 

There are some clues around the engine bay that the engine has been changed. For example there are Crosland stickers for filters that bear no relation to what's on the current engine. So maybe the more modern engine that's been fitted just happens to give 30A at normal cruising speed, which is why the Kestrel has been disconnected.

 

Or is that simplistic wishful thinking?

Edited September 4, 2010 by sociable_hermit

[blodger]

I do not know whether the experts will concur but there used to be a fixation about current in the old days when charging devices like dynamos were all limited (<20 amp cont). Every 60's car I remember had an ammeter not a voltmeter. The follow on alts that replaced dynamos would provide greater amps and regulated the voltage to well within the starter batts ability 13.8v. Higher volts regulators allow the alts to output more amps and modern alts are set to 14.2/14.8 where gassing of batt electrolytre happens.

The early (obsolescent) marine alt controllers (perhaps the Kestrel) merely raised alt charging voltage from the former 13.6/13.8 to the 14.2/14.8 basis saving the expense of replacing the alternator for more efficient charging that could result in battery boiling if settings not right. In marine installations the opportunity to overcome the resistances inherent in the cabling, connections and split charging made the alt controller/battery boilers more desireable.

Alternator controllers are not needed where these resistances do not exist and where the alternators own regulator is at a sufficient voltage.

[Sir Nibble]

I would theorise that with the engine running your inverter current is passing through the relay from the alternator thus overloading it. I would suggest a little reconnection. Usually the alternator charges the engine battery and the relay cuts in to supply the domestic bank. For a camper van or caravan this is quite correct as the major load on the alternator is the vehicle electrical system, on a boat the engine battery usually does nothing but start the engine and requires next to no charge whilst the major load is the domestic battery and so the lions share of the alternator output goes through the relay. I suggest swapping the leads so that the alternator output goes direct to the domestic battery and the relay supplies the engine battery, this way even quite a puny relay will be enough for the job. This should sort you out and your batteries may recover.

[Gibbo]

I agree with Snib.

 

I think your relay burnt out due to excess current. You have two choices: Do what Snib suggests or replace with a much bigger relay.

 

Why your charger didn't go into float I can't work out.

[Keeping Up]

I am interested in your statement since I like simplicity and from what I recall Peter Hopley's device was but with a trimmer so that you could determine your own level of 'boiling'.

The Sterling's have some software or switching to allow for different batt types and the Advercs do a bit of on & off with up & down cyling of the upped voltage.

Is any of that superior to being able to adjust the regulated voltage yourself to suit your circumstances?

It seems to me you have to know what you are doing with any 'boiler'.

Today's conventional wisdom is that modern alts do not need upping controllers provided you are not using split charge diodes.

However, low volt regs still abound and it is handy to be able to get more out of your alt.

I would not disconnect a functioning alt controller but have it switched so its there when the occasion warrants. etc.

So to me 'Keeping Up"s opinion is bad advice

There were two adjustments IIRC, one was the amount of extra current that was made available (which was pretty pointless since the requirement was invariably to have as much as possible) and the other was the voltage at which it cut out. The problem was that it simply ramped up until that voltage was first reached, and then it switched off completely for ever more (or at least until the engine was next stopped and restarted). This was as good as it got in those days, but it never gave the battery any time to absorb the charge unless it was set to quite a high voltage which caused a load of other problems such as burned-out lamps and boiled batteries. They had a tendency to switch themselves off when the battery was only 3/4 charged, in response to the sort of spike that you got when the water pump turned off, and also meant that if you had a low output alternator and a diode splitter (which was the situation they were designed to cope with) once they had switched off you could actually end up with the battery being slightly discharged by the domestic appliances even though the engine was still running.

 

My advice was not to disconnect a functioning controller - it was to leave disconnected one which is already disconnected. And as it's a Kestrel I stand by that.

[blodger]

Well I can see where you get the view that the Kestrel might be best left disconnected.

 

For me, if it is there it should be useable. Whether in reality it is useful will depend upon the alternator (age) model and regulated voltage.

 

As I said there's a bit of a knowledge requirement for using any battery boiler appropriately and well which means ensuring you are not running the alt without achieving any output!

 

Many I have come across do not use their alt controllers because they cannot see it makes any difference. Amongst these folk are those who do not realise it is automatic in its operation? The Kestrel was obviously semi-automatic!

[sociable_hermit]

Well, I took the easy(ish) option and replaced the relay with a heftier Durite example. This included a neat little reversible mod to the Lucas mounting bracket as I hadn't been left with enough spare wire to mount the relay anywhere else.

 

A certain amount of stripping wires with my teeth whilst upside down in the engine bay was involved, but it's all in place now and didn't go bang under testing, which I always consider to be a good result.

 

Interestingly, having run the engine at 1400 rpm for a minute or so, I turned it off and plugged the mains charger back in. After about 2 minutes at full charge it then switched to float mode. I'm still not sure why it wouldn't do that before, but nonetheless, hurrah!

 

The real proof will, of course, be next time we are out and about, and away from mains power for any length of time. However I am very pleased that my batteries aren't in need of immediate replacement as I had suspected.

 

The wiring still needs tidying but I think I will start with fresh plan of what I need and wire it to that, rather than trying to adapt the existing mess still further.

[blodger]

So it would have been worth carrying a spare relay and/or be prepared with a jump lead to parallel the starter and domestic batts.

 

Give some thought to Sir Nibbles/Gibbo's suggestion to rewire the relay so alt always charges domestics and cuts in the starter battery rather than the other way round. The idea being to reduce the amps flowing through the relay.

 

You do not say what capacity of relay either the Lucas or the replacement Durite were/are. Perhaps the Lucas was under spec.

 

Anyway, a temporary result; It's all good fun!

[Sir Nibble]

and didn't go bang under testing, which I always consider to be a good result.

 

Sounds good to me. Pay some attention to your charging system chum, it's important. Maybe when you're alongside on shore power for a while and not dependant on it we could help you out. Gibbo in particular can point you at some easy and inexpensive modifications and advice on making sure nothing is under spec.

[sociable_hermit]

The markings were melted off the old relay but it was blue plastic and therefore most likely a Lucas 33RA. They are rated at 60A.

 

If I understand what's been said correctly, if the batteries are under charge that normally shows as around 30A on the ammeter, but the inverter would be in addition to this? The inverter is 400W so max. 33.3A draw at 12V. It's also possible that the batteries sometimes draw in excess of 30A, let's say 35A. So that would make the total load around 68.3A which is obviously in excess of the relay's stated capabilities.

 

I'm not sure what alternator is fitted, but the present day version of my engine (Vetus M3.28) is fitted with a 75A alternator, which makes sense.

 

The new relay I've fitted is 120A. There didn't seem to be anything available off the shelf between 60A and 120A.

[sociable_hermit]

Sounds good to me. Pay some attention to your charging system chum, it's important. Maybe when you're alongside on shore power for a while and not dependant on it we could help you out. Gibbo in particular can point you at some easy and inexpensive modifications and advice on making sure nothing is under spec.

Thanks, that would be great!

 

The biggest frustration has been in figuring out what's there now. Everything is hard to reach (especially the alternator), some of it is disconnected, and all of the wires are as short as they could possibly be. I hate messy wiring precisely because it makes faulting so difficult, and I think I'd rather come up with a plan of what I'd like and then rip everything out and start again from scratch, so I know what's there and understand why it's there and how it works.

 

At the moment I don't have the time or the money to do the work, but I could start drawing some wiring diagrams. The suggestion about swapping the relay onto the starter battery circuit, for example, makes a lot of sense and is something I'd like to do. Any more ideas like that would be very useful.