New Solar Installation - Confused About State Of Charge

[DJW]

Evening all

 

I've spent today fitting two 95A solar panels, wired in series to a Tracer 30A MPPT regulator. I have the remote meter for the tracer and the readings all seemed pretty good today except state of charge...

 

I've told the meter it's connected to a 550AH battery bank made up of sealed batteries (5 x 110ah batteries) and its state of charge readings seem pretty low. When i switched off the shore power (which had been plugged in continuously for days) state of charge was something like 60% and even when the Tracer goes into 'float' mode (very low Amps charge going into the batteries) the state of charge reading is nowhere near 100%. It seems to fluctuate quite a lot too.

 

Is the SOC reading inaccurate on these or am I doing something wrong? I have read on here that the SOC report is almost as accurate as a Smartguage (which I was considering buying but hoped the Tracer might do the job).

[Grace and Favour]

Hmm - - -

 

I've not a Tracer MPPT, so I cannot comment specifically on your bit of kit.

 

However - we've 960w of panels with an 80A Outback MPPT controller.

 

Our box goes into float at (about) 80% of charge (as measured by Smartgauge)

 

 

 

Depending upon your morning's s.o.c., and in weather such as we've had today - I'd expect your 190w panels to put something between 40 and 50 Ah during the day - that\s at best 10% (ish) of your battery capacity

[smileypete]

Looks like the Tracer SoC reading is just based on batt voltage and is pretty basic.

 

'Battery capacity strip flash:
Each strip equals to 20% of battery capacity.
Note: the calculation takes fully charged voltage as 100%, and over discharge as 0%. All is based on battery voltage, not the real battery capacity.'

 

http://www.belismart.com/index.php?dispatch=attachments.getfile&attachment_id=14

 

cheers, Pete.

~smpt~

[Ally]

How have you wired it? Direct to batteries or via 'some' of the 12v circuits?

[DJW]

Ah, thanks Pete, that might explain it. I did "RTFM" but obviously skimmed over that bit! I had thought the SOC reading was more sophisticated than that.

 

Ally, the MPPT is wired straight to the batteries.

 

I left the shore power connected overnight and the SOC first thing this morning was around 95%. I unplugged the 240v and within half an hour SOC has dropped to 51%. I know my batteries are in decent nick so doubt that's a genuine drop.

 

The shore power keeps the voltage at around 13.5 to 14v. WIthout that and without any solar input (still in the shade here) the voltage has dropped to around 12.7. This would seem to back up what smileypete found that SOC is just based on battery voltage.

 

Looks like I might still be in the market for a smartguage after all!

[Justme]

13.5 to 14v is not the real battery voltage.

 

12.7v is the real bat voltage & roughly indicates that its 90% ish SOC.

[DJW]

13.5 to 14v is not the real battery voltage.

 

12.7v is the real bat voltage & roughly indicates that its 90% ish SOC.

 

If 12.7v is ~ 90% SOC why did the meter report this as only 51%? Is it really that inaccurate?

[Justme]

You need to read the manual & reset its Soc setting.

 

Mostly done by a long charge till you know 100% that the battery is full & then telling the meter its full.

[bottle]

When the battery bank was new then it was probably 550 Ah but I will bet it is not now.

 

Batteries age and also lose capacity if not totally re-charged to 100% SOC regularly, they do still lose capacity but at a slower rate than if not

 

You have set the meter to 550 Ah so it is working on that size.

 

As Justme says, you will have to charge the batteries until they reach their maximum SOC then tell your meter that they are at 100%.

 

ps. you mentioned Smartgauge, this automatically adjust for the ageing etc. of batteries.

 

When a Smartgauge reads 100% then the batteries are at 100% SOC for their current capacity, this will not be the same as when they were new.

 

A couple of sites if you want to learn more.

 

http://www.smartgauge.co.uk/technical1.html

 

http://www.batteryfaq.org/

[Rich]

 

 

ps. you mentioned Smartgauge, this automatically adjust for the ageing etc. of batteries.

 

When a Smartgauge reads 100% then the batteries are at 100% SOC for their current capacity,

So how come that when a SG reads 100% an ammeter will show that up to 6 amp charge is still going in? The charge will continue for a long time, gradually dropping to nil charge when presumably the SG is then telling the truth.

[bottle]

It is in the manual that a Smartgauge may be up to 10% inaccurate whilst the batteries are being charged.

 

edit: to many words

Edited August 5, 2013 by bottle

[Rich]

It is in the manual that a Smartgauge may be up to 10% inaccurate whilst the batteries are being charged.

 

edit: to many words

It may well be but it should be in large letters on the front cover because one of the uses it is put to is to notify when charging is complete, or as near to as makes sense financially. At least by us poor suckers who bought what they thought was an accurate and useful piece of equipment.

 

And that makes the fabled accuracy of the SG somewhat suspect.

[bottle]

Well this poor sucker has I have one, read the manual and did a lot of research and knows what it is telling me.

 

The same as all meters it is the knowing what it says and how to interpret it.

[Rich]

Well this poor sucker has I have one, read the manual and did a lot of research and knows what it is telling me.

 

The same as all meters it is the knowing what it says and how to interpret it.

Well done you. I prefer something that means what it says without my having to employ black arts to make sense of it. I know that many people think well of the SG. Amazingly I am allowed to be one that doesn't and I regret wasting the money I spent on it.

 

How do you know when your batteries are charged sufficiently?

[DJW]

You need to read the manual & reset its Soc setting.

 

Mostly done by a long charge till you know 100% that the battery is full & then telling the meter its full.

Ok, thanks. I'm on shorepower again so will try and work out how to tell it when it's at 100%. The manual is badly translated into english so not that easy to follow in places but I'll have a go tonight.

[Rich]

Ok, thanks. I'm on shorepower again so will try and work out how to tell it when it's at 100%. The manual is badly translated into english so not that easy to follow in places but I'll have a go tonight.

An ammeter would tell you that, surely.

 

If you find out how to tell it the batteries are fully charged could you post the method on here because I haven't found it?

[bottle]

Well done you. I prefer something that means what it says without my having to employ black arts to make sense of it. I know that many people think well of the SG. Amazingly I am allowed to be one that doesn't and I regret wasting the money I spent on it.

 

How do you know when your batteries are charged sufficiently?

 

I use batteries and do not worry to much whether they are fully charged but I do try to treat them with as much TLC as possible.

 

I use a combination of charger (generator) and solar. They vary from about 75% SOC to 100%SOC (Smartgauge)

 

 

An ammeter would tell you that, surely.

 

If you find out how to tell it the batteries are fully charged could you post the method on here because I haven't found it?

 

 

Specific gravity (of course the batteries cannot be sealed, AGM, or GEL) will probably give you the most accurate but again you will have to know what the reading is telling and interpret it. Another learning curve.

 

 

 

Edit: predictive text.

Edited August 5, 2013 by bottle

[smileypete]

An ammeter would tell you that, surely.

 

If you find out how to tell it the batteries are fully charged could you post the method on here because I haven't found it?

 

Mentioned in The Battery FAQ:

 

'9.5. How Do I Know When My Battery Is Fully Charged?

...

'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.'

 

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

http://www.batteryfaq.org/

 

So when the charge current stabilises at the correct absorption voltage, which should be a current of less than 1/50th of batt bank capacity. Lots of good info elsewhere in the FAQ, probably answers about 80-90% of batt related questions.

 

cheers, Pete.

~smpt~

Edited August 5, 2013 by smileypete

[DJW]

If you find out how to tell it the batteries are fully charged could you post the method on here because I haven't found it?

 

No joy there Rich - I read the manual again last night and fiddled about with the remote meter but can't see any way of manually setting the SOC

[Rich]

 

Mentioned in The Battery FAQ:

 

'9.5. How Do I Know When My Battery Is Fully Charged?

...

'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.'

 

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

http://www.batteryfaq.org/

 

So when the charge current stabilises at the correct absorption voltage, which should be a current of less than 1/50th of batt bank capacity. Lots of good info elsewhere in the FAQ, probably answers about 80-90% of batt related questions.

 

cheers, Pete.

~smpt~

Or look at the ammeter.

 

I think you missed reading the "it", the eighth word in the sentence. Rather alters the request.

 

No joy there Rich - I read the manual again last night and fiddled about with the remote meter but can't see any way of manually setting the SOC

 

So I didn't miss it when looking through the manual. The guy who supplied the controller reckons it is written in Chinglish and that it can be learned. I don't think I am going to try.

 

ETC the now normal typo

Edited August 6, 2013 by Rich

[smileypete]

Or look at the ammeter.

 

I think you missed reading the "it", the eighth word in the sentence. Rather alters the request.

 

I think the answer is elsewhere in the thread if you'd care to look.

 

cheers, Pete.

~smpt~

[Rich]

 

I think the answer is elsewhere in the thread if you'd care to look.

 

cheers, Pete.

~smpt~

 

I am unable to find anywhere in the thread that states how to tell a Tracer MT-5 remote meter what the state of charge is which is what the OP was advised to do. Could you please point it out to me?

 

I know two ways to tell when the batteries are fully charged, both very simple. One is to charge until no more is going in according to the ammeter and the other is to leave it on charge for a long time, but this can be, from experience, much longer than you might think.

 

When I installed my Tracer MPPT the batteries were fully charged, they had been on a charger for a couple of weeks and there was no charge going in. But, the SOC according to the MT-5 remote meter was nonsense and varied minute to minute, up and down. It would also have me believe that the LEDs, water pump and the fridge are using up to 200 amps overnight. I think it is telling fibs or even downright lies.

[matty40s]

No customer of mine has been advised to use the MT5 for state of charge readings, the majority have also had smartgauge fitted at the same time, although made aware of the 'not liking solar' readings when the sun is out.

The MT5 is purely a voltage linked figure which may give a realistic SOC when used with brand new batteries, on the first charge,....only.

[Rich]

No customer of mine has been advised to use the MT5 for state of charge readings, t

No one has ever suggested that I use it for the purpose. Because the facility is there I had a look and, quite literally the %s were up and down in the space of seconds so I just decided that it wasn't much use and left it at that.

 

It was when it was suggested that the SOC had to be entered into the gauge that I took notice because I hadn't seen such a facility. And it would seem there isn't one. Reminds me of the time I went into a boatyard well-known for its electrical expertise and was told my problem was that I needed to put into my SG the state of charge. When I said it was not necessary as it could set itself I was told "trust me, you do". I took my problem elsewhere.

 

As has been mentioned before on here, once you get over the excitement of getting all that free power and stop going to have a look the meter to see how much? is going in the whole setup can be left to its own devices and the meter used to give the occasional warm glow when you confirm to yourself how clever you were in installing solar.

[Iain_S]

Looks like the Tracer SoC reading is just based on batt voltage and is pretty basic.

 

'Battery capacity strip flash:

Each strip equals to 20% of battery capacity.

Note: the calculation takes fully charged voltage as 100%, and over discharge as 0%. All is based on battery voltage, not the real battery capacity.'

 

http://www.belismart.com/index.php?dispatch=attachments.getfile&attachment_id=14

 

cheers, Pete.

~smpt~

Which I would read as the Tracer shows 0 at 50% charged, 1 bar = 60%, 2 = 70%, etc to 5 bars=100%

i.e. each bar is 20% of the 50% capacity between Smartgauge's (and everyone else's) 50% and 100%. (IYSWIM )

 

Iain