Battery conundrum

Cardo

Cardo

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Some advice from you guys in the know would be really appreciated!

We have 500Ah of sealed lead acid batteries in our domestic bank. I have a SmartGauge keeping an eye on them to have an idea of the % capacity.

I'm not sure what's going on, but we seem to be eating through our batteries at a substantial rate.
For example, we arrived at our anchorage yesterday at 1800 hrs. The batteries had been charged overnight and we had motored to the anchorage. SmartGauge showed 100% capacity, and around 12.8ish volts.
This morning, 15 hours later, the SmartGauge is showing 71% and voltage is around 12.4v.

Usage has been the fridge, which averages around 3Ah, playing some music for a few hours last night, some LED lights and the LED anchor light overnight. SmartGauge was showing 94% when we went to bed around 2300, only anchor light and fridge were running after that.

I am very confused as to how we managed to drop down to 71% by this morning.

So, ideas as to what's going on?

My thoughts -
- Batteries are shagged (they're only a couple of years old, and until this summer hadn't had much drain on them as we'd been sat in marinas most of the time) and their capacity is no longer anywhere near the 500Ah they should have.
- SmartGauge is not calibrating properly and we have more capacity than it claims. Though what would you equate 12.4v to?
- According to SWMBO's napkin maths, we've supposedly used around 150Ah over approx a 15 hour period, which would equate to a constant drain of 10A. This has certainly not been the case. I appreciate drain on batteries isn't quite so linear, but it gives an indication.

Where has our electric gone?!
 
Cardo said:
Some advice from you guys in the know would be really appreciated!

Where has our electric gone?!
Click to expand...

I'd think there is a good chance it has not gone anywhere apart from what you know you have used.

I think your problem may be that you are comparing the voltage immediately after the batteries had been on charge with a voltage after they had been supplying a small nearly continuous load for 13 hours.

If I am right you will find that the volts and the indicated % state of charge will return to their 1800hours reading very quickly once on charge again. Far quicker than you would expect to put in nearly 30% of 500 Ah.
 
Thanks all for the replies.

I did a quick test to see if any particular battery was pulling down the voltage by disconnecting each one at a time and leaving it out of the bank for a few mins. The bank voltage didn't magically recover, so I'm guessing there is no particular battery that is causing problems.

As for the SmartGauge, who knows? I'm fairly confident the voltage it shows is about right, but as for the % capacity, it's all magickery as to how it achieves the number.

VicS,
What kind of voltages should I be expecting to see? They were sitting at around 12.2v with load (fridge running, ipad charging) and returning to around 12.3v to 12.4v when the load was off.
I start getting nervous when the voltage approaches 12.0v. At what voltage should I really start getting nervous about causing irreversible damage to the batteries? I've been reading around, and some places even suggested they could be discharged as far as 10.5v??
 
pvb said:
I'd agree that this is a possibility. To check, disconnect the parallelling wires and measure each battery's voltage separately with a multimeter.
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I also tried this, but it would appear my cheapo multimeter has lost the plot. Need to go buy a new one, and this time pay a decent sum for something that will actually work!
 
Cardo said:
I also tried this, but it would appear my cheapo multimeter has lost the plot. Need to go buy a new one, and this time pay a decent sum for something that will actually work!
Click to expand...

I would replace the battery in the multimeter first, probably one of those 9v little jobbies.

Pete
 
Cardo said:
As for the SmartGauge, who knows? I'm fairly confident the voltage it shows is about right, but as for the % capacity, it's all magickery as to how it achieves the number.
Click to expand...

I have a very basic Fox-D1 gauge, which is supposed to show voltage or, at the flick of a switch, current. Only it doesn't: the voltage shown decreases steadily with current drawn, even when the battery voltage is almost unaffected. Seeing "9.2V" scared the heck out of me until I check with a multimeter and found it was actually 12.7V ...
 
Pete7 said:
I would replace the battery in the multimeter first, probably one of those 9v little jobbies.

Pete
Click to expand...
I've binned it! The longer I left it on the terminals reading voltage, the higher the voltage went up! When it was claiming my batteries had 16v I decided it wasn't particularly reliable. ;)

I have a theory as to what may be happening. I would appreciate it if someone could let me know if it's possible or whether it's a load of rubbish.

So, we'd run down the batteries quite a bit prior to the last shore power charge, as we'd gone nearly a week without plugging in and the skies had been a bit grey so solar panels were struggling to keep up. SmartGauge reckoned we'd gone down to around 55% at its lowest before we popped into a marina to top up.

When we arrived at the marina, and throughout the day we spent there, the sun was scorchio and our solar panels (300w of them) were putting in a decent charge. This was together with the shore power charger.
Is it possible the voltage created by the solar charger may have confused the shore power charger leading to the shore power charger thinking the batteries were topped up before they really were? Could it be that we only really put in, say, around 75% or 80% charge instead of the full 100%?
 
I cannot speak for your Smartgauge percentage readings, all these complex toys seem to induce more problems than they solve. I have a voltmeter and ammeter, although I rarely use the latter. My voltages are, and have been for the last seven or eight years, very similar to yours. In the evening, after solar panel input all day, the voltage might be anything between 12.8 and 13.2. By late evening this will be 12.6 without the fridge running, maybe 12.4 when it is. First thing in the morning 12.2 or even 12.1 with it running, 12.4 with it off. Consumers on all night are the fridge, about 30% of the time, and 0.5 Amps constant for Navtex, panel controller, the voltmeter, etc.

Your figures sound pretty normal to me. 330Ah of sealed batteries, 125 watts of solar, fridge uses between 3 and 4 amps when running.
 
After running my engine for a while my clipper gauge shows batteries full (& charging at 14 v)
If i then connect to shore power via my Merlin triple charger the charger works at max (charging at 13.3 v )for some time demonstrating that the batteries were not actually full
If i run the engine until batteries show full & do not connect to shore power the meter shows a gradual drop even if the batteries are not connected to anything over 12 hours
This demonstrates that the reading on the meter needs time to settle after engine charging
I suspect that you were not fully charged to start with
 
Sadly, I don't think that the no-load voltage is much help unless one battery is very dead. A load tester gives a better view, if you can buy or borrow one. With wet cells, a hydrometer can usually detect a dud cell but is of no help on totally sealed batteries. With jumper cables you could try testing the batteries individually by using the starter motor or windlass motor as a load. Using a multimeter, good batteries should sneer at the load. If there is a significant voltage drop on the terminals of one battery compared to the others, it indicates a failing battery.
 
Cardo said:
Is it possible the voltage created by the solar charger may have confused the shore power charger leading to the shore power charger thinking the batteries were topped up before they really were? Could it be that we only really put in, say, around 75% or 80% charge instead of the full 100%?
Click to expand...
I doubt that the charger gets confused, they are usually too simple, depending on stage they will try to apply 14.8, 13.5 or 12.8 volts (typically). The MPPT will dance about a bit trying to maximise input wattage but still within limits 12.8 to 14.8 (typically). The Smartgauge might have problems with that as I gather it only measures voltage and not amp-hours in calculating the amount of charge. You could try a few days of charger only.
 
Cardo said:
I've binned it! The longer I left it on the terminals reading voltage, the higher the voltage went up! When it was claiming my batteries had 16v I decided it wasn't particularly reliable. ;)
Click to expand...

I think you will find that is a classic symptom of a failing ...failed... battery in the meter.
Surprised though that you did not get a low battery indication. Maybe you did but just did not notice it!

Next time it happens (to your new better meter) chuck it in my bin please.

.
 
VicS said:
I think you will find that is a classic symptom of a failing ...failed... battery in the meter.
Surprised though that you did not get a low battery indication. Maybe you did but just did not notice it!

Next time it happens (to your new better meter) chuck it in my bin please.

.
Click to expand...

The meter was practically new, however only cost around €5. Maybe a dead battery, but it also took one of those relatively expensive camera batteries, so I think I'll go with something better next time!
 
I am a bit confused regarding your setup. I have a smartgauge and am very happy with it. It does what it says on the box and is an excellent bit of kit. You have said you have solar panels fitted. If so and the sun is shining you will record high voltage which may fool the smartguage into thinking your batteries are in a better state of charge than they are...... ( I think....)

It is also true as someone else said that if you have had the alternator running on charge the reading will be high until the batteries settle. Is it possible that in the evening when the sun go down (breaks into calypso.......) The solar panels stop charging and you then see the correct reading?
 
Daydream believer said:
After running my engine for a while my clipper gauge shows batteries full (& charging at 14 v)
If i then connect to shore power via my Merlin triple charger the charger works at max (charging at 13.3 v )for some time demonstrating that the batteries were not actually full
If i run the engine until batteries show full & do not connect to shore power the meter shows a gradual drop even if the batteries are not connected to anything over 12 hours
This demonstrates that the reading on the meter needs time to settle after engine charging
I suspect that you were not fully charged to start with
Click to expand...

A charge of 14V when the engine is running is actually too low, you should be getting 14.4V minimum and 14.8 max. Also your charge rate at 14V will be much much slower. So not surprised its charging some more on shore power though the charge rate at 13.3 is a float rate and would charge very very slowly.
 
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