Mains charger problem ?

[julianmingham]

Hi,

I’ve got an issue with my charger and/or batteries that I’d like some advice on.

The setup:
The domestic battery bank is 5 x Numax sealed lead-acid deep cycle batteries with 472Ah total capacity (about 18 months old)
The mains charger is a Mastervolt IVO Smart charger 12/40-3 (probably at least 10 years old)
Voltage and current measured on Victron BMV-702 battery monitor

The issue:
When I arrived on board yesterday the domestic bank was at 12.3V, yet I had been on board the previous week for 48hours with the mains charger on all the time although I had switched it off when I left last week.

Steps taken:
1. Switch the charger on and measure the current after a few minutes. It was 7A. I’m not sure what the load was but it can’t have been more than about 4A for the fridge
2. Leave the mains charger on for 24hours, switch it off and leave the batteries with no load for a few hours. The domestic bank then measured 12.4 V
3. Switch the mains charger back on and increase the DC load to about 11A (Eberspacher, lights, fridge compressor). The domestic bank then measured 12.9V and the current was -3A.

I assume that the charger should always maintain the voltage to at least approx. 13.5V, and that the current in/out with the charger on should never be negative. On that basis I assume the charger is faulty ? Or could this be a battery issue ?

Thanks for suggestions

 

[PaulRainbow]

Almost most certainly the charger.

 

[Pasarell]

Almost most certainly the charger.

Really? I would be looking at the batteries first. Charger seems to be putting out a reasonable current for the load and similar to what mine would give in the same situation.
Are any of the batteries getting hot when charger is on?
I would disconnect the charger and all loads and isolate each battery. Leave for an hour or so then check each battery voltage. It sounds to me like a dud battery and that would pull all the bank down. Isolating and resting them for a while will indicate if one of them is the problem.
If all batteries hold their charge equally then I would go back to Paul's suggestion and look at the charger

 

[Plevier]

I nearly posted exactly the same as Pasarell last night, I only hesitated because this is a biggish charger and to pull the volts down I would expect to see more current.
Nevertheless I would suggest doing exactly as he suggests, plus try each battery with a load of a few amps - such as a headlamp bulb - to see if it collapses quickly even if ocv looks ok.

 

[alan]

Sounds like a battery(ies) to me; when charging, the volts will only show as 13.5v when the battery(ies) are fully charged. My friend had the same issue (only two batteries); he was ready to bin the charger but I checked the charger on open circuit and the batteries with no load .. and both batteries were knackered (only two years old!!).

Alan.

 

[matthewriches]

You have not mentioned anything regarding a multi meter yet If you haven't got one, grab one from Screwfix, Toolstation or the like or see if you can borrow one from the boatyard or a mate.

Ignore the battery monitor for a moment.

Give the batteries a bit of a charge, then immediately split them into individual items and watch them over a few hours to see what is happening, if one is rapidly dropping you have a dicky battery dragging the whole lot down. Load testing would be even better if someone near you has a tester. Or as Plevier says, a headlight bulb or heating element would do.

Some chargers are wise to dud batteries and will go into a sort of protect mode. And be safe when disconnecting.

We fit a lot of Mastervolt stuff to tugboats as they seem to rate them as being heavy duty. The big Mastervolt stuff will act as a 12v power supply so other thing to do is with all batteries removed, test what is coming out of the charger with a multimeter. Then apply a bit of load with some lights or similar and see what happens.

Failing that, have a beer or go sailing :nonchalance:

 

[matthewriches]

Just another quick thought, thinking to your battery monitor, it may not be giving you the whole picture depending how it has been wired. Did you wire it in or was it already on the boat?

 

[julianmingham]

Thanks for all your comments, I do have a multi-meter and will now isolate each battery and check the voltage over a few hours. Not sure what I’ve got yet that could put a load on.
I did fit the monitor and it’s on the main +ve feed direct from the batteries.

 

[Plevier]

An alternative approach would be isolate 2 or 3 batteries and see what charger behaviour is then for a while, then swap over to the others. Of course if all 5 are equally done in it won't help!
Btw don't kid yourself those are real deep cycle batteries, Numax is ok middle of the ranks leisure battery stuff.

 

[julianmingham]

Update:
I’ve isolated all batteries and checked the voltage on each regularly.
Results as follows:

Battery. 1. 2. 3. 4. 5
10.20. 13.38. 13.38. 13.31. 13.42. 13.35
10.50. 13.32. 13.30. 13.23. 13.35. 13.30
11.20. 13.27. 13.27. 13.21. 13.31. 13.27
11.50. 13.24. 13.24. 13.19. 13.28. 13.25
12.20. 13.23. 13.23. 13.18. 13.26. 13.23
12.50. 13.21. 13.21. 13.18. 13.25. 13.22
13.20. 13.20. 13.20. 13.16. 13.23. 13.21

I’ve also measured the voltage output of the charger when not connected to the batteries - it was 13.45V
I’ve not found a way to load test the batteries individually.

Conclusions
So far each of the batteries appears to be fully charged, and to be behaving normally although this may not be conclusive in the absence of a load test ?
The output of the charger looks OK although I’m not sure what to expect ?

I need to leave the boat to resume normal life shortly and I’m planning to leave the batteries isolated (until I return next week) to get a true resting voltage from each, in the absence of any better ideas ?

Cheers

 

[Plevier]

Are all your interior, nav and steaming lights LED? If you still have filament bulbs you could get quite a bit of load that way.
In your first post you mentioned the charger current in steps 1 & 2 but did not say what voltage it was giving, do you know?
13.45V is sensible for a smart charger to be giving with no current as it assumes the batteries are full and only want floating. What's more interesting is what it gives with some load.
I think the jury is still out. It would certainly be a disappointing life for your batteries but we don't know their life story.
What did you have before and how long did they last? With similar use?
Have you checked soundness of every junction between the charger and batteries?

BTW in my IVO the 3rd output is limited to 3A for starter battery, is yours the same, are you just using two outputs?
Is it set for AGM? (You called your batteries sealed lead acid, you do mean AGM not sealed maintenance free do you? Common confusion.)

 

[julianmingham]

As in my step 3 I put a load of 11A on (I have a meter that just measures load) and that dragged the voltage down to 12.9V but the in/out current was -3A.
Unfortunately I didn’t record the voltage in steps 1 & 2
When I changed the batteries 18months ago that was the 1st time that I had done that (I’ve only had the boat 3 years) so I don’t know previous life.
Yup checked all the connections
Yes I’m just using 2 outputs on the IVO
the batteries are sealed maintenance free not AGM

 

[RichardS]

Update:
I’ve isolated all batteries and checked the voltage on each regularly.
Results as follows:

Battery. 1. 2. 3. 4. 5
10.20. 13.38. 13.38. 13.31. 13.42. 13.35
10.50. 13.32. 13.30. 13.23. 13.35. 13.30
11.20. 13.27. 13.27. 13.21. 13.31. 13.27
11.50. 13.24. 13.24. 13.19. 13.28. 13.25
12.20. 13.23. 13.23. 13.18. 13.26. 13.23
12.50. 13.21. 13.21. 13.18. 13.25. 13.22
13.20. 13.20. 13.20. 13.16. 13.23. 13.21

I’ve also measured the voltage output of the charger when not connected to the batteries - it was 13.45V
I’ve not found a way to load test the batteries individually.

Conclusions
So far each of the batteries appears to be fully charged, and to be behaving normally although this may not be conclusive in the absence of a load test ?
The output of the charger looks OK although I’m not sure what to expect ?

I may be misreading but why is battery 1 ever anywhere near 10.2V? If the batteries were all connected together in parallel and then disconnected and battery 1 read that low compared to the others then there's something seriously wrong with it.

Richard

 

[matthewriches]

As Richard says, if that is battery 1 column, the battery is fudged.

Charger is perfectly ok.

 

[pvb]

I may be misreading but why is battery 1 ever anywhere near 10.2V? If the batteries were all connected together in parallel and then disconnected and battery 1 read that low compared to the others then there's something seriously wrong with it.

Richard

Column 1 is the time....

 

[RichardS]

Column 1 is the time....

Good grief ... so the time on the bottom line corresponds exactly with the battery voltage of two of the batteries. What are the chances of that?

Richard

 

[Plevier]

As in my step 3 I put a load of 11A on (I have a meter that just measures load) and that dragged the voltage down to 12.9V but the in/out current was -3A.
Unfortunately I didn’t record the voltage in steps 1 & 2
When I changed the batteries 18months ago that was the 1st time that I had done that (I’ve only had the boat 3 years) so I don’t know previous life.
Yup checked all the connections
Yes I’m just using 2 outputs on the IVO
the batteries are sealed maintenance free not AGM

Not sure I understand that - do you mean total load 11A with 8A coming from the charger and 3A from the battery?

 

[julianmingham]

Yes it would appear like that, I.e. 8A from charger and 3A from battery. Or putting it another way, I could interpret that as the mains charger is connected but the batteries are discharging - surely that can’t be right ?

 

[jfkal]

Potentially both. Assuming that the charger is rated to cover house demand by itself then the current should never be negative.
A battery at rest measuring 12.4 V should accept more than just meager 3 A.
I had the same some time ago. Turned out that the charger was faulty and the battery end of life.

 

[Plevier]

The 11A test does perhaps point to the charger, but I will raise again the question of really checking all the connections. Make sure they are firm physically, then under electrical load measure the volt drop across every connection in both + and - lines.
Some other thoughts about the charger, assuming it's basically the same as my IVO (which is a 12/25-3)
1 There is an internal DIP switch to set to float only or 3 stage, check that isn't set to float only. It should go up to 14.4V in bulk and absorption phases.
2 There is an other DIP switch to set float voltage for "wet" or "AGM/Gel". The wet is 13.25V, the AGM/Gel is 13.8V. Although your batteries are wet, I would set the switch to AGM/Gel, 13.8V float is more appropriate to a typical modern lead calcium wet battery.
Those voltages are at 25 deg C - at lower temperatures they should go up a bit, the charger has temperature compensation. Do you have the remote temperature sensor on one of the batteries?
3 My IVO has a green LED indicator that should flash fast during bulk charge, flash slowly during absorption and be continuous in float. Does yours have that, does it behave sensibly?