Electroquest 30 Amp Charger difficulties - Maximum Battery Bank Size?

[alan_fincher]

1 minute ago, WotEver said:

No, you didn’t imagine that. Once SmartGauge can see the voltage dropping it can work out exactly where you are. Until then it’s guessing because it has no real data to base its calculations on. 

Thanks,

I edited my post while you were posting.

Will having had it disconnected cause it to forget all it already knew, please?

[WotEver]

6 minutes ago, alan_fincher said:

For clarity, the Smartgauge was disconnected from the battery bank for several days whilst I reconfigured and rewired everything.  (Will that have caused it to forget everything it "knew" at the point it was disconnected.  Sorry if that's a very basic question that has been answered 100 times before!)

Yup. SmartGauge will have permanent amnesia. It only takes a few cycles to learn again but until then it knows nothing. 

[smileypete]

Might save some time and aggro in the long run to learn up front how to rely on ammeter and voltmeter alone.

The amount of time lost and trouble caused by people taking the Smartguage reading as gospel.

Edited October 30, 2017 by smileypete

[alan_fincher]

2 minutes ago, WotEver said:

Yup. SmartGauge will have permanent amnesia. It only takes a few cycles to learn again but until then it knows nothing. 

This may then be the problem.  I guess I'm looking at it the wrong way, but given those charts that equate a certain voltage to a SOC, it's tempting to say if voltage is 12.7v, then why isn't that 100% SOC, irrespective of bank size.

I am of course fretting that I don't want 5 x 110Ah batteries only about 6 months old to be damaged by not generally being at a good state of charge.

Assuming I measure battery volts with the charger off, and some effort made to get rid of surface charge, what is a generally accepted voltage that I can be fairly certain no significant damage is being done? 

(Actually in my current circumstances, if I'm going to rely on voltage, because I don't trust SG's SOC figures, I'm kind of wondering how useful the SG is!)

2 minutes ago, smileypete said:

Might save some time and aggro in the long run to learn up front how to rely on ammeter and voltmeter alone.

I have never previously bothered to do otherwise!

After early scepticism about the product I finally allowed myself to be persuaded that SG would give a reliable "push of a button" reading that is accurate enough, but if I have to still use some other way, I'm becoming less convinced!

[smileypete]

For charging, just go by tail current, here's the relevant para in The Battery FAQ

In descending order of accuracy and depending on the battery type, one or more of the following three methods is normally used to determine if a battery is fully charged:

• 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

OK it's a bit wordy but I've highlighted the pertinent bits. For sealed batts you may find the charge current stabilises (tail current) as low as 0.5% of capacity, or less.

Edited October 30, 2017 by smileypete

[alan_fincher]

2 minutes ago, smileypete said:

For charging, just go by tail current, here's the relevant para in The Battery FAQ

In descending order of accuracy and depending on the battery type, one or more of the following three methods is normally used to determine if a battery is fully charged:

• 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

OK it's a bit wordy but I've highlighted the pertinent bits.

So is that really saying that if I still have most of my 550Ah left available, they are sufficiently charged when charging current is 2% of 550, i.e. 27.5A, (assuming correct charging voltage).

Or am I misunderstanding completely?

[nicknorman]

9 minutes ago, alan_fincher said:

So is that really saying that if I still have most of my 550Ah left available, they are sufficiently charged when charging current is 2% of 550, i.e. 27.5A, (assuming correct charging voltage).

Or am I misunderstanding completely?

I’d say 2% is too high. But since there is no definition of “fully charged” you can take your pick. I think you want to be 1% or less to be reasonably fully charged.

Back to Smartgauge, if you disconnect it and reconnect it, it will go to the default of 75%. If the batteries at that time were at say 95% it will struggle to work it’s way up to a reading of 100% unless the charging is held for a long time after the batteries are fully charged. However if you discharge the batteries to say 70%, then recharge, it will “catch up” with the state of the batteries.

[WotEver]

26 minutes ago, alan_fincher said:

This may then be the problem.  I guess I'm looking at it the wrong way, but given those charts that equate a certain voltage to a SOC, it's tempting to say if voltage is 12.7v, then why isn't that 100% SOC, irrespective of bank size.

This is why it is difficult to ‘just use a voltmeter’ as some suggest. The charger will have been charging the batteries at 14.5V for ages with the current slowly decreasing, so you can’t tell SoC by charge voltage. When you take the Batteries off charge at anything above say 85% SoC they’ll read 12.7V so you can’t go off that either.

As I pointed out earlier your charge current is well below 1% of the battery capacity. That’s 98-99% charged. Other than by reading the relative density of the electrolyte in the cells the tail current (the current at the end of charging) is the only way to tell when the batteries are fully charged. 

[alan_fincher]

5 minutes ago, nicknorman said:

Back to Smartgauge, if you disconnect it and reconnect it, it will go to the default of 75%. If the batteries at that time were at say 95% it will struggle to work it’s way up to a reading of 100% unless the charging is held for a long time after the batteries are fully charged. However if you discharge the batteries to say 70%, then recharge, it will “catch up” with the state of the batteries.

This may very well be the explanation then.

I would be deeply disappointed if actual SOC had gone as low as 80%, let alone 70% or under.  It's never going to keep charging long after the batteries are anything like 100%, because once the current falls to 3 amps it stops charging. (The float charge is insignificant).

[WotEver]

Also, it was recently stated that a battery manufacturer stated that you could ‘fully’ charge a battery in 12 hours. Once again we hit this problem of definition - what is ‘full’? 99%? 99.9%? 99.99%? I’d suggest that 99.9% is as close as is practical but the time taken to get from 98.9% to 99.9% is... about another 12 hours. (It’s also difficult to read the difference without an accurate multimeter.)

4 minutes ago, alan_fincher said:

It's never going to keep charging long after the batteries are anything like 100%, because once the current falls to 3 amps it stops charging. (The float charge is insignificant).

If the voltage is above 13V and if it’s constantly applied then you’d be surprised. It WILL continue to raise the SoC, although by a negligible amount. 

[nicknorman]

14 minutes ago, alan_fincher said:

This may very well be the explanation then.

I would be deeply disappointed if actual SOC had gone as low as 80%, let alone 70% or under.  It's never going to keep charging long after the batteries are anything like 100%, because once the current falls to 3 amps it stops charging. (The float charge is insignificant).

The other option is to disconnect the Smartgauge and then as part of the power-up sequence, set the indicated SoC to 100% manually. Then you’ll be happy!

[alan_fincher]

13 minutes ago, WotEver said:

If the voltage is above 13V and if it’s constantly applied then you’d be surprised. It WILL continue to raise the SoC, although by a negligible amount. 

If it's telling the truth then the float charge voltage is 13.8V.  The charge current isn't enough to measure on my clamp meter though!

3 minutes ago, nicknorman said:

The other option is to disconnect the Smartgauge and then as part of the power-up sequence, set the indicated SoC to 100% manually. Then you’ll be happy!

I'm never happy, me!

[Tacet]

45 minutes ago, alan_fincher said:

So is that really saying that if I still have most of my 550Ah left available, they are sufficiently charged when charging current is 2% of 550, i.e. 27.5A, (assuming correct charging voltage).

Or am I misunderstanding completely?

2% of 550Ah is 11Ah - which helps you a bit.

[alan_fincher]

26 minutes ago, Tacet said:

2% of 550Ah is 11Ah - which helps you a bit.

Quite right - not sure how I got that wrong!

(I've managed to do 5%, not 2%, haven't I!)

Edited October 30, 2017 by alan_fincher

[WotEver]

31 minutes ago, alan_fincher said:

If it's telling the truth then the float charge voltage is 13.8V.  The charge current isn't enough to measure on my clamp meter though!

It will be tiny - you’re 99.x% charged so there’s only a teensy bit to go. 

1 hour ago, alan_fincher said:

After early scepticism about the product I finally allowed myself to be persuaded that SG would give a reliable "push of a button" reading that is accurate enough, but if I have to still use some other way, I'm becoming less convinced!

If it’s previously worked ok for you then there’s no reason why it shouldn’t continue to do so. It simply requires a couple of discharge/recharge cycles to sync up with your batteries. 

It’s still best to monitor tail current though - always has been. 

[smileypete]

1 hour ago, alan_fincher said:

So is that really saying that if I still have most of my 550Ah left available, they are sufficiently charged when charging current is 2% of 550, i.e. 27.5A, (assuming correct charging voltage).

Or am I misunderstanding completely?

It has to stabilise somewhere less than 2% when the charger has reached the correct absorption charge voltage. For a sealed batt it should stabilise somewhere below 0.5%, for unsealed somewhere between 1% and 2%, maybe more if well worn.

For a smallish charger on healthy batt's, (max charger amps is <10% of bank capacity) I'd expect tail current to stabilise no more than 4 hours after the correct absorption voltage is reached.

Also ISTR anecdotal reports saying this occurs about 2 hours after a Smartguage indicates 100%, but this should be verified by an ammeter.

If you want to be really OCD about it I'd say wait until tail current falls below 2% then wait till the amps fall by less than a third over an hourly period.

Edited October 30, 2017 by smileypete

[WotEver]

48 minutes ago, smileypete said:

For a smallish charger on healthy batt's, (max charger amps is <10% of bank capacity) I'd expect tail current to stabilise no more than 4 hours after the correct absorption voltage is reached.

That all depends on how much <10% you’re talking about. At 10% I’d expect somewhere between 4 and 6 hours. However, most folk have much bigger chargers than that, resulting in a much longer time before tail current stabilises at a low figure. 

[nb Innisfree]

For tail current to stabilise it used to take us varying times between 24 and 72 hrs with our Victron on shore power charging AGMs, this was on top of a bulk charge to acceptance voltage. Off grid I just used to do a bulk charge each day with large alternator then a minimum 8hr charge with Kipor and Victron every 7 days or less, best compromise IMO. Used Smartgauge and BMV as a reference. 

[Iain_S]

2 hours ago, nicknorman said:

The other option is to disconnect the Smartgauge and then as part of the power-up sequence, set the indicated SoC to 100% manually. Then you’ll be happy!

You don't need to disconnect it. Pressing Volts and Status for a few seconds puts it into setup mode.

[smileypete]

1 hour ago, nb Innisfree said:

For tail current to stabilise it used to take us varying times between 24 and 72 hrs with our Victron on shore power charging AGMs, this was on top of a bulk charge to acceptance voltage. Off grid I just used to do a bulk charge each day with large alternator then a minimum 8hr charge with Kipor and Victron every 7 days or less, best compromise IMO. Used Smartgauge and BMV as a reference. 

IIRC your AGMs got badly sulphated. Can you remember what tail current you had?

ETA: From a quick google it looks like Rolls specify a tail current of 0.7% for their AGMs:

http://support.rollsbattery.com/support/solutions/articles/4345-agm-charging

So maybe I should have said below 1% for a sealed batt...

Edited October 30, 2017 by smileypete

[nb Innisfree]

10 minutes ago, smileypete said:

IIRC your AGMs got badly sulphated.

Yes, because I initially thought they were the older type AGMs I charged at 14.2v, realising they were later type I increased to 14.4-6v, that together with several long raised absorption charges recovered them, they lasted another few years. 

Didn't have the bottle to go to 14.8v even though Multicell recommended that. 

Edited October 30, 2017 by nb Innisfree

[MtB]

I too find the tail current never stabilises. I've spent a whole day charging and checking every 45 mins. It's always a little bit lower each time I look.

[nicknorman]

5 hours ago, Mike the Boilerman said:

I too find the tail current never stabilises. I've spent a whole day charging and checking every 45 mins. It's always a little bit lower each time I look.

Aka my favourite word in this context - asymptotic. But of course it’s not asymptotic tending to zero, it’s asymptotic tending to a fixed low value. That value depends on various things like battery type and condition, temperature and voltage.

Edited October 31, 2017 by nicknorman

[nb Innisfree]

8 hours ago, smileypete said:

 

 

8 hours ago, smileypete said:

IIRC your AGMs got badly sulphated. Can you remember what tail current you had?

ETA: From a quick google it looks like Rolls specify a tail current of 0.7% for their AGMs:

http://support.rollsbattery.com/support/solutions/articles/4345-agm-charging

So maybe I should have said below 1% for a sealed batt...

IIRC approx 0.5 A (24v - 8 x 120 ah) and it definitely went as low as 0.2A on one occasion. 

Edited October 31, 2017 by nb Innisfree

[WotEver]

7 hours ago, Mike the Boilerman said:

I too find the tail current never stabilises. I've spent a whole day charging and checking every 45 mins. It's always a little bit lower each time I look.

Which is kinda the point. As an extreme example if you had a charger of only 1% of the bank capacity (and no loads) the time taken to stabilise would be zero seconds, but all of your charging would be in Bulk. 

10 hours ago, nb Innisfree said:

For tail current to stabilise it used to take us varying times between 24 and 72 hrs with our Victron on shore power charging AGMs

Unfortunately this is symptomatic of Victron’s ‘Adaptive Charging’ feature. It does the exact opposite of what is required.