Battery charging issue

[Ewan123]

I'm not really sure whether it's an issue with the batteries or not, but I hope someone has had something similar happen before.

 

We switched the engine on to charge and noticed the battery panel showed the absorption rate fluctuating a lot. The max reading for Amps in (about 30A) behaved as usual, gradually decreasing to about 1.5A in over a few hours; however, about every two seconds the reading would drop right down to almost nothing going in, then go straight back up.

 

Could this be symptomatic of dying batteries? They're the sealed type.

[Richard10002]

It's possible that your domestic stuff is drawing power so the amount that goes to charging the batteries falls for a time. If it has gone from 30A to 1.5A over a few hours, they are probably as full as they can be.

 

How big is the bank, (in Ah), how long does it usually take to fall to 50% SOC, (or something similar)?

[Keeping Up]

Do you have an inverter? When powering only a small load it is not unknown for them to take their power from the 12v supply as a stream of short sharp pulses of current. This can manifest in the way you describe.

[Ewan123]

 

28 minutes ago, Keeping Up said:

Do you have an inverter? When powering only a small load it is not unknown for them to take their power from the 12v supply as a stream of short sharp pulses of current. This can manifest in the way you describe.

We'd had some decent solar over the weekend but the surface charge from that may have been hiding the true voltage I suppose. It did seem to charge as though they weren't that empty.

 

We've got 420ah (4x 105). It can take a couple of days to get down to 12.2V largely just using a couple of laptops and charging a couple of phones (sorry that's not more precise).

 

29 minutes ago, Keeping Up said:

Do you have an inverter? When powering only a small load it is not unknown for them to take their power from the 12v supply as a stream of short sharp pulses of current. This can manifest in the way you describe.

We do and it was on at first, but I turned it off for a minute or so and it didn't seem to have an effect I don't think, though my memory is already hazy on that... will definitely try that if it happens again.

Odd, that first quote should have been Richard10002's.

 

[Tony Brooks]

A thought. What was the sun doing at the time and were there any moving shadows about. After a few days of sun the batteries might have been "full" so the alternator would be regulating the voltage. If the solar regulated at a higher voltage then the alternator may shut down causing the current drop. Likewise, if an MPPT controller has hunting for the maximum power point.

 

Try turning a reasonable electrical load on a see if it stabilises.

[Ewan123]

6 minutes ago, Tony Brooks said:

A thought. What was the sun doing at the time and were there any moving shadows about. After a few days of sun the batteries might have been "full" so the alternator would be regulating the voltage. If the solar regulated at a higher voltage then the alternator may shut down causing the current drop. Likewise, if an MPPT controller has hunting for the maximum power point.

 

Try turning a reasonable electrical load on a see if it stabilises.

Hmm... we're partially shaded by bare trees. We ran the engine around lunchtime because we've so far found that a reasonable way to find out what state the batteries are when the solar is just keeping it at a surface charge. We'd just had about 4 days of no engine and mostly low energy usage, max solar in was about 160W I think (from 400W of panels).

 

We were getting half decent solar through the MPPT at the time of engine running though can't recall the numbers.

 

Will try turning things on next time though not got many high demand devices (except an untested mains electric chainsaw left by the previous owners...)!

 

 

Thanks all! Lots of food for thought so far, bit more playing around required I think. I probably should have mentioned this is our first sunny season on board, so maybe just not used to solar panels being more than decoration!

[Alan de Enfield]

32 minutes ago, Ewan123 said:

We've got 420ah (4x 105). It can take a couple of days to get down to 12.2V largely just using a couple of laptops and charging a couple of phones (sorry that's not more precise).

 

If that is correct, then you are using ~105Ah per day, which doesn't stack up with a couple of lap tops and charging a couple of phones (unless the laptops are sooper dooper power hungry gaming machines).

 

That would suggest to me that either you have some other electrical demands, or, the batteries are down on capacity.

 

If you are getting back from 12.2 to fully charged in 'just a few hours' that would again suggest that the batteries are sulphated and down on capacity.

 

What do you consider to be fully charged and how do you measure it ?

 

If you have on,ly been charging to (say) 90% each time then you will have considerably reduced the capacity over a matter of weeks/months.

[ditchcrawler]

Do you check the water level on them?

 

[Keeping Up]

3 minutes ago, ditchcrawler said:

Do you check the water level on them?

 

Difficult, he said they're sealed.

[cuthound]

I presume that you have checked that all connections (battery, alternator, shunt and back of meter) connections are tight?

[Ewan123]

18 minutes ago, Alan de Enfield said:

 

If that is correct, then you are using ~105Ah per day, which doesn't stack up with a couple of lap tops and charging a couple of phones (unless the laptops are sooper dooper power hungry gaming machines).

 

That would suggest to me that either you have some other electrical demands, or, the batteries are down on capacity.

 

If you are getting back from 12.2 to fully charged in 'just a few hours' that would again suggest that the batteries are sulphated and down on capacity.

 

What do you consider to be fully charged and how do you measure it ?

 

If you have on,ly been charging to (say) 90% each time then you will have considerably reduced the capacity over a matter of weeks/months.

Now that you put it like that, it does seem rather a lot to use.

 

We usually charge until there's only about 1.8A ish going in (according to the Mastervolt Combi Control Panel) which can 4-5hrs of engine to reach. The batteries were installed a couple of years ago though (we've only had the boat a few months) so don't know how the previous owners were treating them.

12 minutes ago, Keeping Up said:

Difficult, he said they're sealed.

 

Yeah, 'Sealed wet flooded' type: https://advancedbatterysupplies.co.uk/product/lucas-lx31-mf/

[Alan de Enfield]

1 minute ago, Ewan123 said:

We usually charge until there's only about 1.8A ish going in (according to the Mastervolt Combi Control Panel) which can 4-5hrs of engine to reach. The batteries were installed a couple of years ago though (we've only had the boat a few months) so don't know how the previous owners were treating them.

 

Current is a good indicator of charge ONLY when combined with Voltage and time.

 

If the batteries are showing 1.8A at 14.4-14.6 volts and it doesn't change for more than an hour you can consider them charged.

[Ewan123]

1 minute ago, Alan de Enfield said:

 

Current is a good indicator of charge ONLY when combined with Voltage and time.

 

If the batteries are showing 1.8A at 14.4-14.6 volts and it doesn't change for more than an hour you can consider them charged.

Sorry forgot the voltage, good point. I do forget to look at that as often when charging, it's usually around 14.4V when I stop, I think, but I'll pay more close attention to both next time. Thanks.

[Tony Brooks]

14.4 volts just means the alternator has started regulating, the batteries will be many hours from fully charged at that point.

[Ewan123]

10 minutes ago, Tony Brooks said:

14.4 volts just means the alternator has started regulating, the batteries will be many hours from fully charged at that point.

Ok, I'll hope my stated 14.4V is just a result of my poor memory - I'll pay proper attention to the volts on the next charge.

[Alan de Enfield]

3 minutes ago, Ewan123 said:

Ok, I'll hope my stated 14.4V is just a result of my poor memory - I'll pay proper attention to the volts on the next charge.

 

AND duration of current and voltage (as above) post No ?

[Tony Brooks]

36 minutes ago, Ewan123 said:

Ok, I'll hope my stated 14.4V is just a result of my poor memory - I'll pay proper attention to the volts on the next charge.

 

Once you get t 14.4 volts plus it's the ale amps you need to watch until they stop falling over an hour or so - as Alan has pointed out. This could be 8 hours or more later.

[Keeping Up]

1 hour ago, Alan de Enfield said:

 

Current is a good indicator of charge ONLY when combined with Voltage and time.

 

If the batteries are showing 1.8A at 14.4-14.6 volts and it doesn't change for more than an hour you can consider them charged.

True but it doesn't address the particular question asked by the OP.

[ditchcrawler]

3 hours ago, Keeping Up said:

Difficult, he said they're sealed.

Miss read it as having  T105 batteries

[Ewan123]

3 hours ago, Keeping Up said:

True but it doesn't address the particular question asked by the OP.

 

It doesn't specifically but is appreciated - I'd forgotten that (considering how long I've been lurking this forum for you'd have thought it might have sunk in earlier.)

[Ewan123]

4 hours ago, Alan de Enfield said:

 

AND duration of current and voltage (as above) post No ?

 

Yep

 

3 hours ago, Tony Brooks said:

 

Once you get t 14.4 volts plus it's the ale amps you need to watch until they stop falling over an hour or so - as Alan has pointed out. This could be 8 hours or more later.

 

Right, another 4 hours of engine and we get to (from an apparent 12.4V after 7A being drawn for an hour or so without):

 

12.7V / 2.3A (without change for an hour) 

Or, with inverter on and 2 laptops 3 phones charging)

12.6V / 1.8A

 

No funny fluctuations, negligible solar at the start of the engine session.

 

[Detling]

2 hours ago, Ewan123 said:

 

Yep

 

 

Right, another 4 hours of engine and we get to (from an apparent 12.4V after 7A being drawn for an hour or so without):

 

12.7V / 2.3A (without change for an hour) 

Or, with inverter on and 2 laptops 3 phones charging)

12.6V / 1.8A

 

No funny fluctuations, negligible solar at the start of the engine session.

 

How are you measuring the voltage and amps? do you have a battery monitor?  If the 12.7 volts was with the engine still on, it is suggesting there is no charge from the alternator at all, is it connected? including the exiter lead with bulb not lit?  If it was it just after the engine was stopped, it is still very low the surface charge should last for a good hour or so at 2.3 amps load. It also seems strange that the current drops when you switch the inverter on, often they take and amp or 2 doing nothing but being ready. 

[Ewan123]

On 31/03/2021 at 22:32, Detling said:

How are you measuring the voltage and amps? do you have a battery monitor?  If the 12.7 volts was with the engine still on, it is suggesting there is no charge from the alternator at all, is it connected? including the exiter lead with bulb not lit?  If it was it just after the engine was stopped, it is still very low the surface charge should last for a good hour or so at 2.3 amps load. It also seems strange that the current drops when you switch the inverter on, often they take and amp or 2 doing nothing but being ready. 

 

Sorry for the drip-feeding of info (e.g. engine revs), I'm climbing around and identifying things as I go along! Also I can't upload images or video on mobile for some reason, will try and get to my laptop soon.

 

I'm measuring on the 'Mastervolt Combi Control Panel'.

 

We have two 70A Lucas A127 alternators. The port alternator deals with the starter and bow-thruster batteries, starboard does the domestic (so says the circuit diagram).

 

I can't find any light connected to the starboard alternator, though the circuit diagram suggests there should be.

 

Our engine panel has a red light labelled 'port alternator', which behaves as described below (not sure how relevant if it's just for starter and bow-thruster).

 

Engine at idle (650rpm ish):

* Port alternator red light on constant

* No fluctuation on battery control panel.

* No fluctuation in engine revs

 

Engine at higher revs (1200rpm ish)

* Port alternator red light flashes on briefly, in sync with...

* ... Aforementioned battery volts and charging amps fluctuation on battery control panel and...

* ... brief slight drop in engine revs (by sound - rev needle on control panel dances around without apparent to engine revs except the highest point it dances to seems likely to be actual revs).

 

I know we're missing information on what the starboard alternator is actually up to, I'll try and hunt again for the lamp (there does appear to be a lead going from D+ to somewhere - apparently the 'ALT control' according to the circuit diagram - but can't physically work it out in real life).

 

 

Does any of that help us???

Edited April 5, 2021 by Ewan123

[Tony Brooks]

That missing lamp, it MIGHT be that both D+ (warning lamp wires) are connected to a single lamp. This may well explain when the lamp stays on at low revs but it makes fault finding difficult.

 

I think that you really need a multimeter and ideally one that has a DC current clamps so you can measure battery voltage and current flow in the battery bank's main lead.

 

The combi control panel is probably measuring the domestic battery voltage.

 

Are both alternator belts tight?

 

I don't see why an alternator light that is off should go out and then flash on and off as you rev the engine. Go out yes, but flash no.

 

On alternator should have one thin wire on it and the other two. The second thin wire is the W rev counter wire and which ever alternator its connected to is providing the pulses to drive it. If a rev counter is dancing about I would suspect a bad solder joint but can't confirm that without knowing the voltage of both battery banks before start up, whilst idling and then when the engine is revving. I would also need to know the current flowing into both battery banks with the engine revving and almost as soon as the engine is started after a night on the boat.

[Ewan123]

Well, since I left that hanging I thought I'd just update with the resolution from today! A bit embarrassing really after all of that, especially as I think the answer was here all along... I think it just took me a few months to get confident poking around in there.

 

After playing with the multimeter a few times, giving up a few times, I went back to the beginning and checked the wiring connections. I think I did a lazy one when I first checked... because one connection was clearly corroded (can't seem to a upload a pic on mobile but I think this is that W connection @Tony Brooks)

 

So WD40, wire brush, scrubadubdub and all appears to be well! No fluctuation in engine revs (sound) and no bouncing needle on dial (first time I can reliably read revs on this!). The charging input now goes as expected.

 

Hoorah.

 

Thank you for all of the patient advice!

Edited August 20, 2021 by Ewan123