Split charge relay problem

[sebrof]

I should be grateful for some advice.

 

My bow thruster does not appear to be getting enough power from the batteries (2 large 190AH lead acid jobs). It has been gradually declining during the past few months, and now just gives a grunt and gives up when I switch it on.

 

A few months ago, I had new electrics installed. Two Victron 50A chargers and the engine alternator are connected to a split charge relay, and charge either two new AGM domestic batteries or the BT batteries.

 

A Smartguage tells me that the domestics are 100%, and usually at around 13.35V. The BT batteries are usually between 12.20V and 12.35V. I am on shore power 95% of the time, and when not on shore power the domestics have never gone below 60%. There is no problem with them, AFAIK.

 

The existing BT batteries were tested when the electrics were done, and pronounced OK. They have had little use since then, and it seems unlikely that they could be knackered. They have ample electrolyte.

 

So what is the consensus? Is the relay working properly? Is the BT itself on the way out? Are the BT batteries indeed knackered? Do those voltages seem OK, or indicative of a problem?

 

And most of all, how should I go about checking? I have the usual tools, plus a digital multi-meter, but I have no idea what to look at first.

 

The electrician, BTW, migrates in the summer, and returns in the winter, so I can't get hold of him at the moment.

 

Thanks for any light you can shed on this.

Edited September 28, 2011 by sebrof

[Bob18]

I assume the bow thruster batteries are in the bow, "next to" the thruster.

Where are the chargers mounted?

If they are at the stern then you've probably got a fair voltage drop between the one looking after the bow thruster battery and the battery.

[Nickhlx]

I would be concerned if the batteries were at only 12.2 to 12.35.. If they are meant to be fully charged and in good condition, even off charge and rested they should be at 12.6 or more - and around 13.0+ if on a charger on a "top up" regime..

 

Time to do an equalisation charge on the BT batteries, measure the S.G., rest them for say 24 hours and see what the voltage is after this time ( with no drain from them since the charge)

 

Also measure the voltage when thought to be on charge and see what that is - if it drops back to "charged" and its top up cycle quite quickly, I would suspect one or more cells in one or more batteries.

 

Nick

[blodger]

And most of all, how should I go about checking? I have the usual tools, plus a digital multi-meter, but I have no idea what to look at first.

I would look at the relay first and make sure it actuates and, check the voltages before and after it when it shoould be charging.

 

I have heard talk of the necessity for fuses/trips at front and back; Have you checked these.

 

It's a process of elimination.

 

You could try setting up some temporary bypass wires from front to back to jump everything and then work forwards or backwards. You can pick up 6mm 53 amp earth tri rated cable for 36p/metre on Ebay from time to time that would do.

Edited September 28, 2011 by blodger

[sebrof]

I assume the bow thruster batteries are in the bow, "next to" the thruster.

Where are the chargers mounted?

If they are at the stern then you've probably got a fair voltage drop between the one looking after the bow thruster battery and the battery.

 

No, the BT batteries are in the engine room. There is a device that leaves them in parallel for charging, but in series when the bow thruster is switched on. This means that the fat cables going to the bow are not as fat as they would have to be if at 12V.

 

This system wasn't changed when the electrics were upgraded.

[Nickhlx]

No, the BT batteries are in the engine room. There is a device that leaves them in parallel for charging, but in series when the bow thruster is switched on. This means that the fat cables going to the bow are not as fat as they would have to be if at 12V.

 

This system wasn't changed when the electrics were upgraded.

 

Depending on the power of the BT, it will be taking maybe 400 amps when operating. Our batteries are sited within 2 feet of the BT and have cables the size of my index finger carrying the main current, so even if your engine room was even midship, the cables would likely be grossly under-sized, and causing a significant volt drop.

 

Knowing the voltages would be good, when you get a moment...

 

Nick

 

 

 

[sebrof]

I would be concerned if the batteries were at only 12.2 to 12.35.. If they are meant to be fully charged and in good condition, even off charge and rested they should be at 12.6 or more - and around 13.0+ if on a charger on a "top up" regime..

 

Time to do an equalisation charge on the BT batteries, measure the S.G., rest them for say 24 hours and see what the voltage is after this time ( with no drain from them since the charge)

 

Also measure the voltage when thought to be on charge and see what that is - if it drops back to "charged" and its top up cycle quite quickly, I would suspect one or more cells in one or more batteries.

 

Nick

 

Thanks.

 

I suppose that if I were to measure the SG now, without doing a charge, any faulty cells would have a very different SG from the good cells. And if they all measured the same, the battery should be OK (or have six equally faulty cells, which I presume is unlikely).

 

From the replies, I am coming round to the view that I may have one or two dud cells somewhere.

 

Depending on the power of the BT, it will be taking maybe 400 amps when operating. Our batteries are sited within 2 feet of the BT and have cables the size of my index finger carrying the main current, so even if your engine room was even midship, the cables would likely be grossly under-sized, and causing a significant volt drop.

 

Knowing the voltages would be good, when you get a moment...

 

Nick

 

The system has worked adequately (though perhaps not optimally) for years. Bear in mind that it is 24V, not 12V. What is happening now is a completely different thing.

 

And most of all, how should I go about checking? I have the usual tools, plus a digital multi-meter, but I have no idea what to look at first.

I would look at the relay first and make sure it actuates and, check the voltages before and after it when it shoould be charging.

 

I have heard talk of the necessity for fuses/trips at front and back; Have you checked these.

 

It's a process of elimination.

 

You could try setting up some temporary bypass wires from front to back to jump everything and then work forwards or backwards. You can pick up 6mm 53 amp earth tri rated cable for 36p/metre on Ebay from time to time that would do.

 

Thanks. I think I need to eliminate the batteries anyway, and that seems to be the easiest thing to do. If they're OK, then I'll look at the relay.

[by'eck]

No, the BT batteries are in the engine room. There is a device that leaves them in parallel for charging, but in series when the bow thruster is switched on. This means that the fat cables going to the bow are not as fat as they would have to be if at 12V.

 

This system wasn't changed when the electrics were upgraded.

 

So you have a 24 volt bowthruster with dedicated 12 volt batteries in series located in the engine room to power it. This requires a long cable run which is not to be recommended but at least volt drop will be minimised if adequate cable gauge is used as only half the equivalent current of a 12 bolt thruster will be needed.

 

Assuming I understand your setup correctly I would strongly suspect the relatively complex contactors/relays you must be using to switch your batteries from series (24 volt) to parallel so they can be charged from the 12 volt charger(s). This is not common practice although clearly possible. Its complexity though with several high current connections could well leave the batteries under charged due to connection or relay deficiencies allowing lower than normal charge voltage. Have a thorough check of connections & if possible measure voltages at batteries when charger is running.

 

I would have thought a dedicated 24 volt charger for the BT batteries which could then be left permanently wired in series, would be far more practical. A 24 volt alternator with 24 to 12 volt converter (for 12 volt systems) could take care of charging when engine is running. Siting the BT batteries near the thruster is also highly recommended.

Edited September 29, 2011 by richardhula

[ChrisPy]

why do you have the dedicated BT batteries fitted remote from the BT? it's a recipe for trouble.

[bottle]

Edit:

 

Reply removed as this is a duplicate thread already running here:http://www.canalworld.net/forums/index.php?showtopic=41560&pid=755659&st=0entry755659

Edited September 29, 2011 by bottle

[blodger]

would have thought a dedicated 24 volt charger for the BT batteries which could then be left permanently wired in series, would be far more practical. A 24 volt alternator with 24 to 12 volt converter (for 12 volt systems) could take care of charging when engine is running. Siting the BT batteries near the thruster is also highly recommended.

 

Likewise the chinese on Ebay do buck boosters that would enable 24v charging from 12v. A simple® relay from the alt output to actuate and supply would automate?

[Bob18]

First place to look is the "magic box" that allows you to switch between series and parallel connection of the batteries. Is it working correctly? - When charging does it put 14.4V onto the batteries (measured at the batteries).

 

 

Like others I would strongly recommend having the bow thruster battery close to the bow thruster and have a 12/24 DC/DC charger in the same general area. This charger would not need to be a mega powerful unit, so the feed wires. This saves the faff of having a pair of large cables running the length of the boat. Remember even with a 24 volt system the voltage drop over a 40m run at 200A can be quite significant unless the cables are big enough - for example 50sqmm cable over 40m at 200 amps gives a voltage drop of about 10%.

[NB Willawaw]

There's not enough information to solve this in one.

It sounds like you have an unusual system but you have what you have.

 

I suppose it's an example of why you shouldn't employ an electrician who only works half a year.

 

I travel extensively visiting boats and ships but am never far from my email.

 

I often get customers asking me about further work or planned upgrades and couldn't go walkabouts for a season.

It's not good customer service is it ?

Edited September 29, 2011 by NB Willawaw

[sebrof]

So you have a 24 volt bowthruster with dedicated 12 volt batteries in series located in the engine room to power it. This requires a long cable run which is not to be recommended but at least volt drop will be minimised if adequate cable gauge is used as only half the equivalent current of a 12 bolt thruster will be needed.

 

Assuming I understand your setup correctly I would strongly suspect the relatively complex contactors/relays that switch your batteries from series (24 volt) to parallel so they can be charged from the 12 volt charger(s). I have never heard of such a system although its entirely possible to install such. Its complexity though with several high current connections could well leave the batteries under charged due to connection or relay deficiencies allowing lower than normal charge voltage. Have a thorough check of connections & if possible measure voltages at batteries when charger is running.

 

I would have thought a dedicated 24 volt charger for the BT batteries which could then be left permanently wired in series, would be far more practical. A 24 volt alternator with 24 to 12 volt converter (for 12 volt systems) could take care of charging when engine is running.

 

Yes, I think you have understood it properly. I would agree that a dedicated charger and new alternator would be a simpler solution, but it's all money, and in these straitened times I am trying to avoid non-essential expenditure.

 

The switch is a complex-looking but robust affair. It was fitted some time ago in Holland, and I suspect many barges have or had them.

 

why do you have the dedicated BT batteries fitted remote from the BT? it's a recipe for trouble.

 

Why is it a recipe for trouble? It just means it requires heavy cable running down the boat. As far as I can tell the installation is at least 10 years old, if not 20 or more, and has worked fine until now.

[sebrof]

There's not enough information to solve this in one.

It sounds like you have an unusual system but you have what you have.

 

Indeed. I am not going to completely re-do a system that has worked for many years just because something (which could be just a dud cell) has ceased to function correctly. But I am grateful for suggestions for how to identify the fault, and have ordered a hydrometer.

 

I suppose it's an example of why you shouldn't employ an electrician who only works half a year.

 

He was recommended as he has worked before on Dutch barges, and knows their idiosyncracies. Such people are few and far between. At this stage, there is no evidence that it is his fault, but it would certainly be nice if he were around.

 

why do you have the dedicated BT batteries fitted remote from the BT? it's a recipe for trouble.

 

Why is it a recipe for trouble? It just means it requires heavy cable running down the boat. As far as I can tell the installation is at least 10 years old, if not 20 or more, and has worked fine until now.

[NB Willawaw]

I think you have enough "experts" putting their head together on this one offering free advice.

Fault finding by committee is not my thing.

 

I guess it's a bit late for your fault but the advice about will o the wisp electricians may help others reading

 

 

 

Indeed. I am not going to completely re-do a system that has worked for many years just because something (which could be just a dud cell) has ceased to function correctly. But I am grateful for suggestions for how to identify the fault, and have ordered a hydrometer.

 

 

 

He was recommended as he has worked before on Dutch barges, and knows their idiosyncracies. Such people are few and far between. At this stage, there is no evidence that it is his fault, but it would certainly be nice if he were around.

 

 

 

Why is it a recipe for trouble? It just means it requires heavy cable running down the boat. As far as I can tell the installation is at least 10 years old, if not 20 or more, and has worked fine until now.

[WotEver]

As has been said, there's little point in saying how it should have been installed, you have a system that's worked for many years so we need to find what's changed.

 

The very first and simplest check would be to measure the standing voltage of the BT batts, then start the engine and see if that voltage rises. If it doesn't then we know that the fault lies with either the split charge relay or your parallel/series contactors, or any of their associated connections. If it does rise, what does it rise to? If it rises to 14.4V or thereabouts then I think we can probably say that the batts have had it. If it rises by a smaller amount then that's where it gets interesting and your hydrometer readings would be the best place to start.

 

Tony

[sebrof]

As has been said, there's little point in saying how it should have been installed, you have a system that's worked for many years so we need to find what's changed.

 

The very first and simplest check would be to measure the standing voltage of the BT batts, then start the engine and see if that voltage rises. If it doesn't then we know that the fault lies with either the split charge relay or your parallel/series contactors, or any of their associated connections. If it does rise, what does it rise to? If it rises to 14.4V or thereabouts then I think we can probably say that the batts have had it. If it rises by a smaller amount then that's where it gets interesting and your hydrometer readings would be the best place to start.

 

Tony

 

Thanks Tony,

 

The BT batteries seem to be permanently around 12.3V. Turning on the engine, or switching on the chargers, appears to make no difference. The domestics, however, go up to 14.5V or so when those two things happen, (until the chargers go into float).

 

So, trying to think logically, it suggests to me that the batteries have reached an equilibrium state. They are not going up, because no charge current is reaching them, and they are not going down because they are too weak to run the BT, so there is no drain.

 

Which takes us to either the relay or the big switch. I know that the switch is not totally dead, because when I try to use the BT, there is a clatter from the switch as it goes over to 24V, then back to 12V because there's not enough energy to sustain it in 24V mode (which means the BT is switched on and trying to draw current). It then switches back to 24V again, and the cycle continues until I get bored and turn off the BT switch. I get bored pretty quickly.

 

The relay is a dual-sense BEP Marine 125A VSR, which is meant to cut in at 13.7V and out at 12.8V.

 

When not being charged, my domestics are typically around 13.1V. They are 225AH Lifeline deep-cycle AGMs, and have led an easy life on shore-power for their 9 months of existence.

 

The engine is hand start, although there is a small starter battery for the genny (which hasn't been used since last summer). This battery is switched manually, and is currently reading 12.85V.

 

Hopefully I will have the hydrometer by the weekend.

[WotEver]

Okay, it sounds to me like it's most definitely the VSR. I suggest you either switch on the chargers or start the engine, then short out the VSR with a jump lead. I'm sure you'll then see the BT batts voltage rise. Leave it like that for some time to try to get a bit of charge into the very flat batteries.

 

Tony

[sebrof]

Edit:

 

Reply removed as this is a duplicate thread already running here:http://www.canalworld.net/forums/index.php?showtopic=41560&pid=755659&st=0entry755659

 

How bizarre.

 

I didn't intentionally post twice. It looks as though in correcting a typo, I (or the system) has inadvertently re-posted the message.

[sebrof]

Okay, it sounds to me like it's most definitely the VSR. I suggest you either switch on the chargers or start the engine, then short out the VSR with a jump lead. I'm sure you'll then see the BT batts voltage rise. Leave it like that for some time to try to get a bit of charge into the very flat batteries.

 

Tony

 

Thank you, that sounds encouraging.

 

I have an old 30A charger knocking around. I think I'll just connect that to the BT batteries as I haven't a clue what to short. The various items on the main electrical panel are squeezed in fairly tightly and it's hard to know what's what.

 

What would make a new VSR pack up? And (assuming that's the problem) should I replace it with another one, or get something else?

[bizzard]

If stuck for a battery tester, a very simple but potentially dangerous method can be substituted.

Now before i begin,all the electrical experts lay off from coming back at me with remarks about dangerous lunatic ect ect.

as i have a sneaking suspicion that you have resorted to this harsh method at times when hard pressed and lost,forgotten or simply don't own correct test gear.

Here we go.

Take battery to the middle of a field,far from any surrounding signs of habitation dump it down and build a little wall of mud around it,remove cell stoppers or strips. Don a fire proof suit like F1 driver wear,crash helmet and goggles.

Nip back to your vessel an fetch a hefty bar,a mooring stake will do. Approach offending accumulator side on, eye it up, take a deep breath and holding the bar by a hand at each end,lunge forward and boldly whack it on both terminals,don't diddle about in a timid manner,or it will arc and flash big time,whack it on fast,if a faulty cell or cells are present they will boil immediately,all this takes about 4 seconds,yank bar off crisply. This is an extra heavy resistance drop test. But be careful.

Now have a nice large brandy before testing the rest of em.

 

Don't do it if battery has just come off charge, Too much hydrogen about.

This little trade trick should also fix your boredom.

Edited September 29, 2011 by bizzard

[nbfiresprite]

Totally bonkers dangerous lunatic, In 23 years as an engineer, I have never resorted to anything as foolhardy as this.

 

Firesprite

 

In the wilds of the Fens

[Bob18]

The domestic battery voltages look to be good, 14.5 when charging, and dropping to 13.something at rest.

 

"the relay" (VSR) - is that between the Alternator and the "big switch"? I hope it is.

 

Now how does the big switch know which way it should be connecting the batteries? Most of the time it needs to be "charge" (12 volt) mode, only going into 24 volt mode when there's a demand for 24 volts. To do this safely the 12 volt supply has to be disconnected from the battery, and the batteries "re-wired" to be in series, and then connected to the load, and lots to go wrong. From your description it sounds to be a stack of relays and contactors, one of which is failing to stay on, the fact that its not connecting charging to the 24 volt battery suggests its the isolation contactor that's failing, and that there is some interlocking that gives you the repeated tries. The technical term for this sort of failure on MUCH bigger switches is "machine gunning" (I'm talking about switches for 25,000 volts, at over 400A - and its quite spectacular to see the lumps of molten copper flying around...).

 

Without seeing how the switch is actually made it very difficult to be more precise than that - any pictures of the guts of the beast?

[bizzard]

Totally bonkers dangerous lunatic, In 23 years as an engineer, I have never resorted to anything as foolhardy as this.

 

Firesprite

 

In the wilds of the Fens

You couldn't have been a motor engineer then. There are hundreds of different types of engineer. The Americans name for a train driver too.

Help! other motor mechanics,come clean and admit you've done it in an emergency cos i know you have,or at least heard of it.

Come on be brave! and help me out.

In the hydrogen fumes of the Stort.