Battery conundrum

[Chris_Robb]

Cardo, I have pretty much the same capacity - 4 x 110AH lead acid - and the same experience.

We started off in 2010 with 4 new open Lead acid from Numax. I was surprised as you were at how much the batteries lost voltage and % charge overnight regularly down to 12.2V. Eventually 2 of them boiled and overheated so much under power that they had to be thrown overboard.

I replaced the lot in Aegina with 4 sealed recycling Korean E-nex batteries of the same capacity and the curious thing noted was that over night the voltages were still about 12.7V (from 12.9V) and even with 8 amps being taken by the fridge draw that would drop to 12.6V, but recovered when the load was off. [Fridge sounds like its taking a lot of amps, but its a powerful job capable of running as a deep freeze and is so well insulated it uses very few amps overall].

It seems absolutely clear to me that I just had poor quality batteries which did not hold their charge.

 

[VicS]

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!

Mine is Maplins cheapest. In fact I had one, bought two more when they were on a "2for" offer. So now keep one at home one on the boat and gave one to my son.
They take the flat 9 volt batteries which last for years if not inadvertently left switched on.

I wont buy an expensive meter because I know sooner or later I'll do something nasty to it. Better to have two cheapies so if one gets broken the other is still OK.

http://www.maplin.co.uk/domestic-multimeter-37279 Used to be only £5! Leads are poor but I made up a longer pair with clips on the end any way

 

[bobgarrett]

Digital multimeter batteries run down very fast if you leave them on by mistake. I have done this a few times so know!
Does your battery condition meter have an ammeter setting? It must know the current drawn if it is doing an intelligent job of working out how much remains. If it does then by switching to this you should be able to see if excessive current is being drawn.
I'd still suspect as a culprit that one battery is failing. Disconnecting and testing it immediately may not work unless it is under load. Better to remove one at a time and run for a couple of days. However, unless your battery condition meter is very clever and or can be reset easily it will be confused by the lack of one battery, so best solution is to test each battery with a good sized load and see how it behaves.

 

[charles_reed]

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!

Cheap or expensive, to work properly they need a good 9V dry cell.

Your Smartguage is obscuring the position.

1. Your batteries, immediately off charge should be showing some 13.1v, this should drop to about 12.7v with no discharge.
2. At 10.5v your battery will be irrecoverably discharged.
3. 12.4v, after overnight use is reasonable, with no other load on the battery.

It seems your batteries are not being fully charged - either due to high temperatures limiting the controller or (most likely) one or more of the batteries failing.
You really need to have them out and drop-tested, individually, and then properly re-charged by a charger which goes into an absorption phase, to equalise the cells.
No doubt Troubador will be along to comment.

It does sound as though

 

[rogerthebodger]

last for years if not inadvertently left switched on.

That was the bane of my life,inadvertently left switched on, until I got one that automatically turned it's self off if left on too long.

 

[charles_reed]

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.

Depends on batteries Chris - 14.8 is OK for open lead acid, providing you top up the cells regularly, but will kill gel batteries stone-dead and shorten the life of sealed batteries. A far safer max voltage is 14.4.

 

[Chris_Robb]

Depends on batteries Chris - 14.8 is OK for open lead acid, providing you top up the cells regularly, but will kill gel batteries stone-dead and shorten the life of sealed batteries. A far safer max voltage is 14.4.

Absolutely. 14.8V is fine with good quality batteries but killed mine. With the new sealed units, the manufacturers specify charging at 14.8V, but I have reduced the charge to 14.4V for safety. Also this puts less strain on the alternator (less heat?) as well as it is down from 90 amps on start up to about 70 amps.

A beneficial side effect is that the Sterling controller does not trip anymore, but that may have been due to the bad battery faults - although Charles Sterling did not agree that that might have caused it.

Out to Leros on Tuesday..... looks like the summer is going to break down to a large area of thunderstorms!

 

[William_H]

I think the OP problem relates to the shortcomings of the smart guage. With fancy algorythms it tries to decide the percentage charge of a battery by its voltage. As already said this depeds on recent usage and charge temperature and other things.
I would be very wary of any device that claims to show battery charge percentage. Of real use can be the cumulative amp hour meters which at least show what you have put in a nd what you have taken out. But even then actual charge percentage depends on battery condition.
I would suggest that if readings from the smart guage have suddennly turned queer tha there amy be a battery problem. So isolate each battery and check its performance in isolation. ie charge it and then discharge and see how voltage goes. A comparison with the performance of the other batteries in the bank may indicate a problem with one.
If all seems oK then basically provided you are sure the batteries have been fully charged. (by knowing that an equivalnet of 120% of AH have been put in since battery was low) then check time to batteries get to a low voltage reading and relate this to actual amphours used. It will become obvious when batteries are not giving the performance you need. (50% of claimed AH rating of the battery is quite a normal result and so still OK)
To sum up don't rely too much on that smart guage % reading. good luck olewill

 

[boatmike]

I think the OP problem relates to the shortcomings of the smart guage. With fancy algorythms it tries to decide the percentage charge of a battery by its voltage. As already said this depeds on recent usage and charge temperature and other things.
I would be very wary of any device that claims to show battery charge percentage. Of real use can be the cumulative amp hour meters which at least show what you have put in a nd what you have taken out. But even then actual charge percentage depends on battery condition.
I would suggest that if readings from the smart guage have suddennly turned queer tha there amy be a battery problem. So isolate each battery and check its performance in isolation. ie charge it and then discharge and see how voltage goes. A comparison with the performance of the other batteries in the bank may indicate a problem with one.
If all seems oK then basically provided you are sure the batteries have been fully charged. (by knowing that an equivalnet of 120% of AH have been put in since battery was low) then check time to batteries get to a low voltage reading and relate this to actual amphours used. It will become obvious when batteries are not giving the performance you need. (50% of claimed AH rating of the battery is quite a normal result and so still OK)
To sum up don't rely too much on that smart guage % reading. good luck olewill

Without wanting to be argumentative, such criticisms of smartgauge are pretty well based on a lack of experience with it. Like all information it needs to be viewed as advisory rather than accepted blindly, but I have found mine to be a useful bit of kit and coupled with an accurate digital ammeter provides an instant readout of charge/discharge and voltage. I have always found the % readout fairly accurate but would agree that it should not be followed blindly. The voltages displayed cannot be argued with however and the additional features are simply IMHO a bonus. What I do think is that, as I said earlier, the fact that the boat in question has solar panels which I assume are permanently connected, will have the effect of showing a higher voltage even when the amperage produced is small. It is possible that this is confusing the posters readings as at night, when the panels will not produce an output, the voltage will drop. I suggest an experiment to disconnect the solar panels and see if this produces understandable readings.
I also agree with those that say the readings obtained in the morning are not unreasonable. There is probably nothing wrong here at all apart from the fact that the voltages taken before night falls are not effectively "resting" volts. With the SPs on the batteries are in fact on constant charge.

 

[sailinglegend420]

.....This morning, 15 hours later, the SmartGauge is showing 71% and voltage is around 12.4v.................
Where has our electric gone?!

12.4 with no load and no charging does mean 70% SoC.

I'm sure SmartGuage is correct - but you don't say how long you have had it installed. It needs to "learn" the state of your batteries over several charge discharge cycles - down to 50% if possible. This is a very sophisticated monitor that uses clever mathematical algorithms to work out the % depth of discharge of the batteries just by measuring the voltage, and it does this over one thousand times a second. Because it doesn’t use a shunt, it is cheaper and very much easier to install, and has proved to be much more accurate than any Battery Monitor that uses a shunt. As batteries age and you use them SmartGuage gets more accurate.

It's one failing is mine tends to read 100% charged too early. As soon as the charge stops it will re-calculate and eventually give you an accurate reading. You dropped down from 100% to 94% in three hours. I doubt if you used 6% in that time - it was just SmartGuage synchronising itself.

I suspect your time in the marina has killed them - either over charged them with too much solar, or undercharged them with no shorepower.

 

[pvb]

SmartGuage ...has proved to be much more accurate than any Battery Monitor that uses a shunt.

It's one failing is mine tends to read 100% charged too early. As soon as the charge stops it will re-calculate and eventually give you an accurate reading.

Aren't those statements contradictory?

 

[halcyon]

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.!

I think that 100% is not 100% capacity, and that 12.4 in probably around 55-60%. You are not getting full capacity, may be alternator voltage, could be sulphated batteries giving a surface charge.

Do you have a ammeter that can monitor charge going into battery, discharge from battery and the voltage ? not alternator output.

You are going to have to ignore the cleaver and go back to first principles.

Brian