Hello and Advice about fixing an "odd" charging problem....

[Nico Bosham]

Hello all,

Welcome to the latest "long time lurker creates an account to ask a question" thread....

As per title I have a slightly odd charging issue on my boat. It's a Jeanneau Sun 2500, with a Yanmar 1GM diesel - one engine starter and one house battery.
Over the course of last season, the house battery charging was a bit hit and miss, as evidenced by the (permanent/fixed) digital voltmeter that is connected to it. Sometime is would be very obviously charging and sometime it would not. If I say, motored for an hour, it would sort itself out and I was never in bother with power for house things, nav, fridge, stereo etc.

This season seems even worse, and I had thought the battery might be knackered, but my (educated) hunch tells me it a charging not a battery issue....

My investigations thus far are as follows:

• Over the course of a day I might for example switch only the fixed voltmeter on first, and all on its own and the display reads 12.2V for the house battery.
• Switching on GPS, Depth and Speed etc might make it drop straight to 11.5V, fridge makes it drop to 11.2V.
• Over the course of a day out, I am seeing single digit voltages and the GPS, and even more horrifyingly, the fridge, stops working (I think Fridge needs 11V+ and GPS 10V+)
• Engine starter reads 12.4V on mulitmeter without engine running. (There has never been a hint that the engine starter is in trouble...)
• I start the engine and using a multi-meter, the voltage across the engine starter reads 13V at tickover and with a moderate amount of "onions" 13.6V
• House battery voltage does not change, even with engine revs.
• When I connect the boat to shorepower, the house battery meter immediately registers 13.4V, and so does multimeter across house battery
• Last weekend, having proved the alternator is apparently charging the engine starter, I
• connected the engine starter to the house battery with some jump leads and the multimeter AND fixed house voltmeter both immediately read 13.4V, which tells me that the fixed house voltmeter is at least accurate - it and the multimeter have never read even slightly differently when connected to the house battery

I have concluded that there is fundamentally nothing wrong with the alternator - it is clearly capable of charging and is charging the engine started no problem (and house when I daisy-chain it direct to the engine starter.
There is no obvious sign of loose or problematic or degraded cabling anywhere - the house battery is locate in a bone dry storage area under a forward berth, and looks completely spotless.

Could there be a "box of tricks" somewhere - a diode maybe? between the house battery's connection to the alternator that has gone bang? Something that is bypassed/not required when connected to shorepower or daisy-chained? again no obvious sign of this.

I was kind of hoping the house battery was shot, as that's an easy, if expensive replacement job, but it does seem to perform every bit as well as one could expect when charged.

Thanks in advance for any idea of what might be afoot here.

Discombobulated of Bosham.

 

[Graham376]

What type of battery isolator(s) do you have, a 1, both, 2, off, rotary switch or, separate isolator switches for each battery? If you have separate battery switches for engine and house, you may have a VSR (voltage sensitive relay) which has failed.

 

[andsarkit]

You need to find out how the charge is supposed to get to the house battery assuming there is a priority system to charge the engine battery first. Either a 1 both 2 switch, a diode splitter or a voltage sensitive relay that connects when the engine battery has reached adequate voltage.
Your observation that the house battery charges after the engine has been running for a few hours may indicate that a VSR ( if fitted) may be set to a higher voltage than needed.
Obviously undo and recheck all connections for a good clean contact.
I would expect the engine battery to go to 14V fairly quickly with the engine running. Perhaps get the alternator checked at a local alternator dealer.

 

[Sandy]

When did you last check all the connections?

 

[Clancy Moped]

Is your drive belt slipping?

 

[AngusMcDoon]

The voltages are all low & suggest discharged or failing batteries. The engine starter should be 12.7 V at rest, dip only when the engine is being cranked, and then when the engine is running in less than a minute go up to the alternator set point voltage of approximately 14 V. Engine starter batteries only have a very shallow discharge in a normal engine start.

It sounds like you have a VSR in your system. It's normal if you have one that when the engine has started you see no change on the house battery voltage. This is because the VSR at this point connects the alternator to the engine start battery only. After the short period mentioned above when the voltage on the engine starter battery has reached the set point in the VSR, about 13 V, the VSR will parallel the two banks and the house battery voltage will start to rise. On my system there is an audible clunk when it does this.

Connecting the shore power causing the house battery to rise to a charging voltage is not unexpected if you have a VSR & the mains charger is connected on the house side of it.

If your house battery only shows 12.2 V at the start of the day and dips into or below the low 11's under a normal load then it won't last long.

 

[Nico Bosham]

Hello and thanks you all for your replies so far... To try to answer the questions:

Battery Switches - I have two individual battery switches - they kind where you insert a red plastic "key" turn them on and they key is locked in when they're on. It's not the rotary 1/2/both/off type.

Oddly one of them seems to do nothing whatsoever - all of the house electric work independently of both switches (being as they are, all controlled from the two switch panels above the little nav table, but the engine starter is defo on the lower one. According to the chap I bought the boat off of this time last year, "the upper one does nothing", and it would appear that this is true, despite the fact that there are a lot of wires going to and from it! I wondered if it for the diesel heating somehow? I have never had this working, even though the digital control panel is powered up regardless of whether this mystery isolator is on or off.

I could still have a VSR type thing though right?

Connections - checked in a visually, but not particularly rigorous fashion on Sunday gone as part of the jump-lead experiment.

ansarkit - I completely agree; I do not know if there is a priority logic to the charging, but even if there was, with the way the engine starter is always tip-top, something must've changed for the system to have decided to wait longer for the house battery to charge? Maybe the change is a failed component that is not permanently open-circuit?

The way that the problem seems to have come on progressively, as opposed to in an instant does rather point to a slow failure of a component. There are some fuses in amongst the electric under the companionway steps (where the engine and starter battery are) but they all appear intact.

Drive belt slipping? - no I do not think so - there is no sign of that and if it was, surely that would negatively effect the charging of the engine starter too?

 

[Trident]

You need to find out what gets the charge from the alternator to the house battery. It may be a direct lead from the alternator but normally the alternator - if it doesn't have a combining battery switch which you say it hasn't - will charge the start battery only and then a relay of some sort will close when the charge is high enough and that will allow charge to the house battery too

The normal setting on a voltage sensitive relay (which will be a cube box with one wire to the start battery positive and one to the house and a negative to somewhere ) is 13.2v - this means until the alternator has raised the start battery to 13.2v (ie full at 12.8v and with a charge current that is higher than that) it won't start charging the house battery .

So you may have a) a dodgy start battery that is not getting full - 12.2v is about 50% capacity , 12.8v is a full charged battery when rested and not being charged , which means unless you run the engine for a long time it won't get to charging the house, or
b) a dodgy VSR or wiring to it that isn't allowing the full charge to the house or c) simply don't motor long enough to charge everything and have some parasitic load on the start battery that is draining it between use.

You can check the first by fully charging the engine start with the shore power and then leaving it a day or so and see what it reads - you can also do this connected and disconnected to check for a parasitic load - if it drops when connected up but you think everything is off you'll know something is drawing from it be it a short or an unknown device

My suspicion is that the battery is poor and doesn't get full under from the alternator so takes a long time to have a high enough voltage to open the VSR and trickle charge the house which also has some big loads with the fridge etc and so also is near really full unless shore power has charged it.

 

[Boater Sam]

You may have an ordinary split charge relay with poor connections rather than a voltage sensitive relay Or a diode again with poor connections.
You also need to find out why that isolator switch "does nothing" the 2 problems may have a common cause.

 

[nigel1]

Hello and thanks you all for your replies so far... To try to answer the questions:

Battery Switches - I have two individual battery switches - they kind where you insert a red plastic "key" turn them on and they key is locked in when they're on. It's not the rotary 1/2/both/off type.

Oddly one of them seems to do nothing whatsoever - all of the house electric work independently of both switches (being as they are, all controlled from the two switch panels above the little nav table, but the engine starter is defo on the lower one. According to the chap I bought the boat off of this time last year, "the upper one does nothing", and it would appear that this is true, despite the fact that there are a lot of wires going to and from it! I wondered if it for the diesel heating somehow? I have never had this working, even though the digital control panel is powered up regardless of whether this mystery isolator is on or off.

It's possible that the two switches are connected together, this was standard on Beneteau boats. I believe that their thinking waws that if the start battery was no good, it was easy to start engine from the house bank.
Not really a good idea, I disconnected the bridging cable on my boat.
Have a look to see if there is a cable connecting both switches.

Beneteau (and possibly Jeanneau) used a split diode to charge the start and house batteries, also not the best approach, as this produces a 0.5V voltage drop.

Have you checked the voltage output from the alternator, using a multimeter directly on the +ve and -ve terminals of the alternator, (not at the battery).
Would expect something in the region of 14.2 to 14.6V.

If the house bank drops to 11.5V with just the nav instruments on, it would indicate that the battery is near (or at) end of life. Do you know how old they are?

 

[Daydream believer]

https://www.youtube.com/results?search_query=how+a+5+pin+relay+works