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Battery Monitors and Capacity


GeoffS

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39 minutes ago, Dr Bob said:

Yes, agreed and your method should throw a lot of light on the problem but if the Soc via smart gauge and amps drawn give similar results to the op initial results then is the capacity low? One possible explanation is the SG is telling porkies. Using the V at rest allows guessing the SoC at any state of charge.....but as Nick says with limited accuracy, but good enough for this question and all it needs is a quick glance in the morning. To the OP, what was your voltage and Amps draw this morning when you got up?

As Nick says though, vital to ensure all the wires go through the shunt.

The thing about the smart gauge is that its source data is only voltage, the rest is based on deterministic software. Nothing can be out of kilter except the voltage calibration. Provided the voltage calibration is within limits, and the device is installed correctly, it won't be telling "porkies".

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2 hours ago, nicknorman said:

The thing about the smart gauge is that its source data is only voltage, the rest is based on deterministic software. Nothing can be out of kilter except the voltage calibration. Provided the voltage calibration is within limits, and the device is installed correctly, it won't be telling "porkies".

Indeed. And the voltage agrees with the Victron so it’s a fair assumption that it’s correctly calibrated, PLUS OP got 8 years out of his last set of batteries. So I think we can be happy that SmartGauge is accurately displaying SoC. 

3 hours ago, Dr Bob said:

if the Soc via smart gauge and amps drawn give similar results to the op initial results then is the capacity low?

Yes. There’s no other explanation. 

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Thanks for all the input.

I haven't been at the boat apart from for few minutes earlier today. After more than 24 hours of discharge the SG was showing 79% and the Victron that 26AH had been used. The only item that was running was a 12V fridge minus whatever the 2 x 50W solar panels had put back in.

However I will look into it further, particular the shunt wiring, and follow your suggestions over the weekend and report back afterwards. The charger is on now and will be until tomorrow so I will have a clean start in the morning.

Thanks again.

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1 hour ago, GeoffS said:

After more than 24 hours of discharge the SG was showing 79% and the Victron that 26AH had been used.

That’s a capacity of only about 125Ah!  However, it’ll be a far more accurate calculation if you can get down to 60% SoC. Nevertheless I suspect Nick might be on to something with his suggestion of the shunt being incorrectly wired. As he said, the only connections to the domestic battery negatives should be the shunt and the SmartGauge. 

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My understanding is that the Smartgauge is not necessarily accurate at around 80%. I think someone here quoted Gibbo when the above was suggested as a criticism of his product, where his response was: 

"So What!!!"

The intimation was that it didn't matter whether it was accurate or not at 80%, as that is not what it is designed to do.

I'm fairly sure my bank has a capacity around 200 to 225Ah. Smartgauge seems to agree with this once it gets down to about 65% and below. Above that it gives widely varying results.

I use the Ah used reading from a NASA BM2, which I am assuming is correct, which it may not be :(

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29 minutes ago, Richard10002 said:

My understanding is that the Smartgauge is not necessarily accurate at around 80%. I think someone here quoted Gibbo when the above was suggested as a criticism of his product, where his response was: 

"So What!!!"

The intimation was that it didn't matter whether it was accurate or not at 80%, as that is not what it is designed to do.

I'm fairly sure my bank has a capacity around 200 to 225Ah. Smartgauge seems to agree with this once it gets down to about 65% and below. Above that it gives widely varying results.

I use the Ah used reading from a NASA BM2, which I am assuming is correct, which it may not be :(

I find mine is consistently accurate at 80% - accurate as in within a few % of the AH gauge -so I don’t know why yours wouldn’t be. The only region I find it not very good on discharge is the first few %, say from 100% to 96%. By 95% it’s sorted itself out.

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Does seems the batts are underperforming, maybe give the supplier a bell, if they're reputable they should see you right.

If there's filler caps that can be carefully removed without risk or damage, might be worth a check with a hydrometer, if the SGs are all over the place then that's not so good.

Possibly the thing to do for new batts is a fullish charge then an SG check or timed discharge test, they may need a few cycles to reach full performance but shouldn't be that far away from the rated capacity.

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On 20/10/2017 at 16:55, Richard10002 said:

My understanding is that the Smartgauge is not necessarily accurate at around 80%. I think someone here quoted Gibbo when the above was suggested as a criticism of his product, where his response was: 

"So What!!!"

The intimation was that it didn't matter whether it was accurate or not at 80%, as that is not what it is designed to do.

I'm fairly sure my bank has a capacity around 200 to 225Ah. Smartgauge seems to agree with this once it gets down to about 65% and below. Above that it gives widely varying results.

I use the Ah used reading from a NASA BM2, which I am assuming is correct, which it may not be :(

Just on the near-constant dis-ing of Smartgauge, we are now on the boat for a couple of weeks and I intend to keep an eye on it and report. We came out of the marina yesterday afternoon (boat having been on float charge). This morning just before starting the engine, Smartgauge was on 71% and AH gauge set to the badged capacity of 450AH was on 74%. I often find that the batteries seem to be a bit “lazy” for the first cycle following a long period on float, and am hopeful that the SG will not be behind the AH gauge tomorrow morning. We had a fairly early start at 08:30 and by about mid day (and having stopped at Curdworth top lock for a late breakfast, including 3 slices of toast in the toaster on battery power) I saw the SG at 99% and shortly after, at 100%. The charge current was 8.5A at 14.5v, ie below 2% of capacity, which many people consider to be fully charged. My AH gauge is set to 1% tail current and showed 97% SoC. An hour later, the AH gauge is showing 100% with 3.5A charge current.

Perhaps I am just lucky but I find this typical SG behaviour and don’t understand why some folk seem to want to dis it so much. Perhaps their devices are badly installed? When my SG shows 100%, the batteries are “fully charged” by many people’s measure, or if you want to get them better charged, add an hour. Or two hours if you are a perfectionist!

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23 minutes ago, nicknorman said:

End of play today, having cranked the charge voltage up to 14.7v, we had 2.2A which is about 0.5%. Getting close to fully charged!

I was chatting with Gibbo about this recently. Is fully charged 90%, 98%, 99%, or 99.99%? I think you me and him would say 99.99% but many others seem happy with High 90’s. 

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9 minutes ago, WotEver said:

I was chatting with Gibbo about this recently. Is fully charged 90%, 98%, 99%, or 99.99%? I think you me and him would say 99.99% but many others seem happy with High 90’s. 

Given that all batteries exhibit a self dischsrge current, I guess the battery can never get closer to fully charged than reaching a point where the tail current has dropped to the point where it matches the self discharge current? 

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Update.

As far as I can see all negatives are going through the shunt and nothing else is connected apart from the Smartgauge.

At 11.30 am Saturday arrived at boat having left charger on. Gone to Float all saying 100%. Disconnected Solar. Inverter and Webasto on. 12V fridge running

15.30 12.7V SG 97% Victron - 15AH

17.30 126V 93% -21AH

Laptop TV/DVD and phone on.

21.30 12.4V 70% -47AH

Sunday

8.00 12.3V 63% -69AH

10.30 12.2V 60% -77AH

15.30 12.2V 57% -92AH

17.30 12.2V 56% -97AH

Decision needed now, do I leave them to discharge further and see what happens or do I turn on the charger (I have hook up available).

20171021_122556.jpg

20171021_122543.jpg

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I also noticed today that the batteries have a small sticker on them saying 'Intended purpose: For use with electrical hook up with minimal off grid habitation usage'. Which is not what I would say is suitable for any travelling boater!

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What a shockingly poor installation.

At first sight it appears neat and tidy but no thought whatever appears to have been given to when the time comes to replacing the batteries. How can they be lifted out without pulling ALL that wiring to bits?

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Regarding charging, from The Battery FAQ

'According to IEEE 450-2002 Annex B Recommended Practice, "The pattern of charging current delivered by a conventional voltage-regulated charger after a discharge is the most accurate method for determining state of charge. As the cells approach full charge, the battery voltage rises to approach the charger output voltage, and the charging current decreases. When the charging current has stabilized at the charging voltage, the battery is charged, even though specific gravities have not stabilized." It should be less than two percent of the capacity (C/50) at the manufacturer's recommended temperature compensated absorption charging voltage level of the battery. For the average sized wet Low Maintenance (Sb/Ca) car battery (BCI Group 24) at 77° F (25° C), that would be less than two amps at 14.4 VDC with the cells gassing (bubbling) freely and evenly. '

http://jgdarden.com/batteryfaq/carfaq9.htm#charged

I've highlighted the two bits people tend to overlook.

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6 minutes ago, Mike the Boilerman said:

What a shockingly poor installation.

At first sight it appears neat and tidy but no thought whatever appears to have been given to when the time comes to replacing the batteries. How can they be lifted out without pulling ALL that wiring to bits?

I have personally disconnected and removed the batteries to re build the box and they have been removed and replaced for other works so no issues, not easy maybe but do able.. My issue is whether the batteries are performing and if not whether I need to go back to the supplier and seek recompense

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14 minutes ago, GeoffS said:

Gone to Float all saying 100%.

Sadly that tells us nothing much. If the current at charging voltage (somewhere around 14.4V) has dropped to less than 4A and has remained stable for about 45 minutes then we know the batts are close to fully charged. If the current is still reducing then the batteries aren’t there. If the voltage has dropped to float then they’ll never get there. Many chargers switch to float way too early and the procedure then is to switch them off and back on in order to continue charging at Absorption voltage. 

Regardless of the above the Batteries appear to have lost maybe three quarters of their capacity. It could be from chronic under-charging or it could be that they’re faulty. You can certainly talk to the supplier but don’t expect too much. 

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From history checking the time the charger is in Absorption and Float mode and looking at the charging current I am fairly certain they were fully charged. Many times I have seen tail current at 3-4A and the charger still be in Absorption. This is the first time recently it has been in float purely because I left it on overnight.

 

1 minute ago, Richard10002 said:

You should charge them up as much as possible, ideally to 100%, every day. Looks to me like your batteries have a capacity of a bit over 200Ah, (maybe 215-220Ah).

Yes and I do. But 4 new batteries 5 months ago at 115AH each should presumably not be at only 200AH total now. That is what I am trying to investigate.

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There truly are only two possibilities. Either the batteries are somehow faulty or you’ve been under-charging them. The latter is far more likely as a ‘faulty’ battery usually has far more dramatic results than a simple loss of capacity. Four faulty batteries even less likely. 

You don’t have one of the four getting hot and/or bulging do you?

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1 hour ago, GeoffS said:

Update.

As far as I can see all negatives are going through the shunt and nothing else is connected apart from the Smartgauge.

At 11.30 am Saturday arrived at boat having left charger on. Gone to Float all saying 100%. Disconnected Solar. Inverter and Webasto on. 12V fridge running

15.30 12.7V SG 97% Victron - 15AH

17.30 126V 93% -21AH

Laptop TV/DVD and phone on.

21.30 12.4V 70% -47AH

Sunday

8.00 12.3V 63% -69AH

10.30 12.2V 60% -77AH

15.30 12.2V 57% -92AH

17.30 12.2V 56% -97AH

Decision needed now, do I leave them to discharge further and see what happens or do I turn on the charger (I have hook up available).

It does seem as though they are knackered. No point in discharging them further. I did manage to find some info on the web about them. Hmmm, 250 cycle life down to 50% SoC is pretty poor and the same as a cheapo ones. Perhaps Exide buy in cheap as chips batteries from China, paint them blue and put a label on, then resell with a 300% profit!

I found dual purpose batteries such as those to be pants, but they can sometimes be temporarily rejuvenated by an equalise charge at 15.5v. Not for too long though, as you can't easily top up the water. 2 or 3 hours.

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21 minutes ago, WotEver said:

There truly are only two possibilities. Either the batteries are somehow faulty or you’ve been under-charging them. The latter is far more likely as a ‘faulty’ battery usually has far more dramatic results than a simple loss of capacity. Four faulty batteries even less likely. 

You don’t have one of the four getting hot and/or bulging do you?

No heat or bulging. But also given my regime very unlikely to have been undercharged. Especially as I managed 8 years from the last set.

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4 minutes ago, GeoffS said:

No heat or bulging. But also given my regime very unlikely to have been undercharged. Especially as I managed 8 years from the last set.

Agreed. So back to the supplier then :)

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