Battery or cabling/connection issue?

[jimbo]

I need some help with a battery or cabling/connector issue. I have 4 x 118amp carbon lead batteries on my boat, they are 4 years old, have never been discharged below 70% and are kept topped up by solar panels. Until this week they have been working very well. A few days ago, after about 6 hrs sailing, using all the usual loads such as plotter, autopilot, fridge etc, the plotter low voltage alarm went off (not unusual tbh), and then the main board low voltage alarm went off. The (not totally reliable) Scheiber board was reading 11.8v whilst the Victron battery monitor was reading 12.3v with batteries 90% full. A couple of hours later the autopilot shut down as did the plotter. The board was reading 10.5v whilst the Victron monitor was saying 12.2v. The autopilot could only be revived with the engine on. A couple of days later the same thing happened (the batteries had been charged to 100% on shore power the day before). This time the solar regulator alarm also went off, advising batteries below 50% (Victron monitor suggested 88%). This could be a totally unrelated fault with the regulator but the timing is suspicious. Checked the Victron settings and all ok and charging to 100% should synchronize SoC readings.
Have the batteries expired or is this a cabling issue? Any suggestions as to how to resolve very welcome.

 

[Iliade]

Possible you have a dead or dying battery pulling the rest down. Before doing anything, inspect the batteries for swelling or heating. Likewise for electrolyte levels.

Try separating the batteries then running either a discharge test or leave them overnight then measure voltages.


If not the cells, start looking for unexpected loads...

 

[VicS]

I need some help with a battery or cabling/connector issue. I have 4 x 118amp carbon lead batteries on my boat, they are 4 years old, have never been discharged below 70% and are kept topped up by solar panels. Until this week they have been working very well. A few days ago, after about 6 hrs sailing, using all the usual loads such as plotter, autopilot, fridge etc, the plotter low voltage alarm went off (not unusual tbh), and then the main board low voltage alarm went off. The (not totally reliable) Scheiber board was reading 11.8v whilst the Victron battery monitor was reading 12.3v with batteries 90% full. A couple of hours later the autopilot shut down as did the plotter. The board was reading 10.5v whilst the Victron monitor was saying 12.2v. The autopilot could only be revived with the engine on. A couple of days later the same thing happened (the batteries had been charged to 100% on shore power the day before). This time the solar regulator alarm also went off, advising batteries below 50% (Victron monitor suggested 88%). This could be a totally unrelated fault with the regulator but the timing is suspicious. Checked the Victron settings and all ok and charging to 100% should synchronize SoC readings.
Have the batteries expired or is this a cabling issue? Any suggestions as to how to resolve very welcome.

The discrepancy between the Victron monitor , which measures the voltage at the battery, and the Scheiber panel suggests a poor connection in the wiring between the battery and the panel

First step, perhaps, to confirm the readings with a reliable multimeter.
.

 

[Sandy]

Do you have a calculation of the amps or watts usage? From that you can work out the number of amps or watts used in a given time.

118 * 4 = 472 total storage
472 / 2 = 236 usable amps

236 - (your total amps usage * hours switched on)

say:

15 * 7 = 105 ah used.

What is the 'normal' voltage with everything is switched on after an hour, two hours or three hours?

Is the Victron 'battery monitor' a shunt or other device? I'd be more inclined to trust the Victron.

What is the shore power charger? What is its output amps rated at?

How long was the shore power on for? Do you know how many amp hours were delivered to your batteries? Does the shore power feed the house or engine battery first? What are the absorption rates of your 'carbon lead' batteries? Are they AGM's which have a higher absorption rate than lead acid?

Are you 100% confident that you left for the trip with the batteries fully charged.

 

[Boathook]

There is some talk that lead acid batteries being kept fully charged all the time do lose capacity. I had this problem the other year over the winter with batteries always fully charged and not ''worked''. They hardly had any capacity and struggled to run anything for more that a few hours.
I tried various ways to bring back to life but ended up buying 2 new 110 ah batteries.

 

[jimbo]

Possible you have a dead or dying battery pulling the rest down. Before doing anything, inspect the batteries for swelling or heating. Likewise for electrolyte levels.

Try separating the batteries then running either a discharge test or leave them overnight then measure voltages.


If not the cells, start looking for unexpected loads...

Thanks but would one dead battery explain the discrepancy between the two monitor readings? Victron is saying everything is normal whilst the Scheiber panel suggests otherwise.

 

[B27]

I need some help with a battery or cabling/connector issue. I have 4 x 118amp carbon lead batteries on my boat, they are 4 years old, have never been discharged below 70% and are kept topped up by solar panels. Until this week they have been working very well. A few days ago, after about 6 hrs sailing, using all the usual loads such as plotter, autopilot, fridge etc, the plotter low voltage alarm went off (not unusual tbh), and then the main board low voltage alarm went off. The (not totally reliable) Scheiber board was reading 11.8v whilst the Victron battery monitor was reading 12.3v with batteries 90% full. A couple of hours later the autopilot shut down as did the plotter. The board was reading 10.5v whilst the Victron monitor was saying 12.2v. The autopilot could only be revived with the engine on. A couple of days later the same thing happened (the batteries had been charged to 100% on shore power the day before). This time the solar regulator alarm also went off, advising batteries below 50% (Victron monitor suggested 88%). This could be a totally unrelated fault with the regulator but the timing is suspicious. Checked the Victron settings and all ok and charging to 100% should synchronize SoC readings.
Have the batteries expired or is this a cabling issue? Any suggestions as to how to resolve very welcome.

The starting point would be to check the voltages in both places using an accurate meter, both with and without a load being drawn.
Then maybe with a load being drawn, check for voltage drop in the cabling between the + at he battery and the + at the panel and likewise the -ves. I use a couple of car headlight bulbs to give a 10A load. But just having the fridge running might do.

If there is a real voltage drop, then check each cable and connection until you find it.

Opinions will differ as to how much cable loss should be tolerated.

 

[jimbo]

The discrepancy between the Victron monitor , which measures the voltage at the battery, and the Scheiber panel suggest a poor connection in the wiring between the battery and the panel

First step, perhaps, to confirm the readings with a reliable multimeter.
.

Yep, will check each individual battery to see if there is a wrong 'un

 

[jimbo]

Do you have a calculation of the amps or watts usage? From that you can work out the number of amps or watts used in a given time.

118 * 4 = 472 total storage
472 / 2 = 236 usable amps

236 - (your total amps usage * hours switched on)

say:

15 * 7 = 105 ah used.

What is the 'normal' voltage with everything is switched on after an hour, two hours or three hours?

Is the Victron 'battery monitor' a shunt or other device? I'd be more inclined to trust the Victron.

What is the shore power charger? What is its output amps rated at?

How long was the shore power on for? Do you know how many amp hours were delivered to your batteries? Does the shore power feed the house or engine battery first? What are the absorption rates of your 'carbon lead' batteries? Are they AGM's which have a higher absorption rate than lead acid?

Are you 100% confident that you left for the trip with the batteries fully charged.

Hi Sandy, lots of questions there, only some of which I can answer.

The victron monitor uses a shunt and I assume it calculates the SoC by deducting the net amps going out (nb solar panels trickling in some power during day) and deducts this from the capacity that I have entered manually.

Have been sailing 6 hrs now in glorious sunshine, mainly under autopilot but fridge off, and victron reading 12.8v and the panel is reading 12.6v (this is normal as there is always a small v drop st the panel).

I don't know what the output of the shore charger was but next time I will try to find out how many amps I used to fully charge and see if this corresponds with the amount of amps that the Victron monitor says we're taken out. I'm sorry I don't know the absorption rate of these batteries but if I know what went in and it is roughly the same as the Victron monitor then will be very confident that the monitor is working fine.

I am not 100% the batteries were fully charged on departure (solar top up can lead to overstated SoC apparently) but they were before yesterday's occurrence as had been on shore power overnight.

Will also test the battery voltages with a multimeter.

Will report back

 

[jimbo]

There is some talk that lead acid batteries being kept fully charged all the time do lose capacity. I had this problem the other year over the winter with batteries always fully charged and not ''worked''. They hardly had any capacity and struggled to run anything for more that a few hours.
I tried various ways to bring back to life but ended up buying 2 new 110 ah batteries.

Thanks - I hope this is not the same situation!

 

[Boater Sam]

If you have been relying on the % state of charge reading of the monitor and stopping charging when it reads 100%, the batteries are toast. These monitors tell lies unless they are reset very regularly with the batteries charged until the amps going in is less than 1% of the battery capacity. Only then is the battery fully charged.

 

[KompetentKrew]

Will also test the battery voltages with a multimeter.

I'm sure the Victron is right.

It's a bad connection somewhere in the circuit, I reckon. I would test with jump leads / fly leads - use them to bypass things and see if the problem goes away.

My boat is now 30 years old. The pre-purchase surveyor insisted the batteries were duff because the inverter gave a low voltage alarm and shut down when he plugged in a load (500W hair drier or something?). We charged up the batteries, put the fridge on for some hours and tested the battery voltage - all good, so we sailed home. Months later I identified the cause as being corrosion on the terminals of the master fuse and fuse holder - replaced those and I can draw 100A through it.

More recently some bizarre behaviour was traced to the main battery isolator switch - a screwdriver across the terminals relieved the problem immediately, then I used a bulldog clip or something until the replacement switch arrived.

Low voltage DC circuits, like 12v - 48v, are weird. Corrosion and bad connections cause voltage drop, but sometimes only under load.

However troubleshooting is easy, if boring and sometimes frustrating - you just eliminate things one by one.

The plotter may have an option to show voltage (my B&G Vulcan does). Does it consistently read less than the Victron by the same amount? E.g. 12v when the battery is being charged at 13.5v and 10.5v when the Victron is showing 12v.

You need to get the problem to show itself again - when the plotter goes off, take a fly lead from the negative terminal of the batteries to the plotter's black lead. Does it come on again? Now do the same from the positive terminal of the batteries to the plotter's positive. I bet one of these will restore it to life, proving that the batteries are fine and it's just a cabling / connector problem. Now you just have to trace the cabling from battery to plotter, eliminating things one by one - use the flylead from the battery positive to one side of the main fuse then the other, for example. Does that bring the plotter to life? If so you know the problem is in the part of the circuit that you have bypassed; if not it's between the main fuse and the plotter. You have multiple devices losing power, so the problem is surely close the battery - between the battery and the fuse / distribution board, if on the positive side.

 

[Iliade]

The (not totally reliable) Scheiber board was reading 11.8v whilst the Victron battery monitor was reading 12.3v

That missing half volt could be cable losses or inaccurate readings. I wouldn't lose too much sleep about that, although it could indeed indicate a poor connection between the two.

I'd start with the batteries themselves, then work my way outwards.

Do any of your batteries look like this:

 

[jimbo]

I'm sure the Victron is right.

It's a bad connection somewhere in the circuit, I reckon. I would test with jump leads / fly leads - use them to bypass things and see if the problem goes away.

My boat is now 30 years old. The pre-purchase surveyor insisted the batteries were duff because the inverter gave a low voltage alarm and shut down when he plugged in a load (500W hair drier or something?). We charged up the batteries, put the fridge on for some hours and tested the battery voltage - all good, so we sailed home. Months later I identified the cause as being corrosion on the terminals of the master fuse and fuse holder - replaced those and I can draw 100A through it.

More recently some bizarre behaviour was traced to the main battery isolator switch - a screwdriver across the terminals relieved the problem immediately, then I used a bulldog clip or something until the replacement switch arrived.

Low voltage DC circuits, like 12v - 48v, are weird. Corrosion and bad connections cause voltage drop, but sometimes only under load.

However troubleshooting is easy, if boring and sometimes frustrating - you just eliminate things one by one.

The plotter may have an option to show voltage (my B&G Vulcan does). Does it consistently read less than the Victron by the same amount? E.g. 12v when the battery is being charged at 13.5v and 10.5v when the Victron is showing 12v.

You need to get the problem to show itself again - when the plotter goes off, take a fly lead from the negative terminal of the batteries to the plotter's black lead. Does it come on again? Now do the same from the positive terminal of the batteries to the plotter's positive. I bet one of these will restore it to life, proving that the batteries are fine and it's just a cabling / connector problem. Now you just have to trace the cabling from battery to plotter, eliminating things one by one - use the flylead from the battery positive to one side of the main fuse then the other, for example. Does that bring the plotter to life? If so you know the problem is in the part of the circuit that you have bypassed; if not it's between the main fuse and the plotter. You have multiple devices losing power, so the problem is surely close the battery - between the battery and the fuse / distribution board, if on the positive side.

Thanks for your comprehensive reply. Will start testing batteries and circuits tomorrow and report back what I find

 

[jimbo]

That missing half volt could be cable losses or inaccurate readings. I wouldn't lose too much sleep about that, although it could indeed indicate a poor connection between the two.

I'd start with the batteries themselves, then work my way outwards.

Do any of your batteries look like this:
View attachment 177847

Will open up the boxes and have a look (and test) tomorrow.

 

[jimbo]

The starting point would be to check the voltages in both places using an accurate meter, both with and without a load being drawn.
Then maybe with a load being drawn, check for voltage drop in the cabling between the + at he battery and the + at the panel and likewise the -ves. I use a couple of car headlight bulbs to give a 10A load. But just having the fridge running might do.

If there is a real voltage drop, then check each cable and connection until you find it.

Opinions will differ as to how much cable loss should be tolerated.

Thanks.and will do.

 

[jimbo]

Update.
Plugged into shore power on arrival at destination. Unfortunately we had to motor the last 2 or 3 hours as wind died so the batteries were close to full on arrival. The batteries charged for a very short time, went into float mode according to the BMS, and the Victron monitor also went to 5amps of charge (also have 118a engine battery and 2 x 60a for bowthruster) and then to zero. All seemed normal and consistent with the readings of SoC. This morning tested all the batteries individually and they are fine - all reading between 13.02 and 13.10 whilst the Victron monitor reading 12.96 and the board 12.9v, no sign of corrosion. Checked the two bus bars at the board and they were both reading 12.95v. So, nothing obvious there.
I really need to do the above when the issue happens but that is not so easy when at sea.
Will keep monitoring and report back if I get to the bottom of it.
Thanks everyone for your ideas, suggestions and comments.

 

[VicS]

Update.
Plugged into shore power on arrival at destination. Unfortunately we had to motor the last 2 or 3 hours as wind died so the batteries were close to full on arrival. The batteries charged for a very short time, went into float mode according to the BMS, and the Victron monitor also went to 5amps of charge (also have 118a engine battery and 2 x 60a for bowthruster) and then to zero. All seemed normal and consistent with the readings of SoC. This morning tested all the batteries individually and they are fine - all reading between 13.02 and 13.10 whilst the Victron monitor reading 12.96 and the board 12.9v, no sign of corrosion. Checked the two bus bars at the board and they were both reading 12.95v. So, nothing obvious there.
I really need to do the above when the issue happens but that is not so easy when at sea.
Will keep monitoring and report back if I get to the bottom of it.
Thanks everyone for your ideas, suggestions and comments.

You need to compare the voltage at the board with the battery voltage displayed by the Victron monitor, and confirm both with a multimeter, with as much load as possible on the system.
If the previously observed discrepancy is due to a bad connection or contact there will be little or no voltage difference while there is little or no load but its magnitude will increase as the current draw innreases.

 

[KompetentKrew]

This morning tested all the batteries individually and they are fine - all reading between 13.02 and 13.10 whilst the Victron monitor reading 12.96 and the board 12.9v, no sign of corrosion.

You fully charged in the evening and then left shore power disconnected overnight so that these were the resting voltages?

The Victron shunt should be right next to the batteries, so I'm surprised there's that much voltage drop already - the whole point is that it should read the exact same.

The corrosion may not be obvious - that's why you test with fly leads; just a long wire with crocodile clips at each end.

 

[KompetentKrew]

What kind of bolts are on the battery terminals?