Solar wiring question

[Midnight]

Hi 
I added two solar panels which seem to be working fine. I followed the manufacturers instructions and took both cables from the MPPT controller direct to the battery terminals. I've noticed that on the Mastervolt MICC reading the battery voltage is up around 13.2 volts but the capacity reads at only about 21%.  I switched the shore power on and charged the batteries overnight but the capacity only went up to around 31% despite the batteries being fully charged.

Presumably the battery capacity works on some kind of bean counting system so should I have taken the negative cable from the controller to the shunt instead of the battery terminal?

[TheBiscuits]

Yes.  Your MICC needs to see the sunshine coming into the batteries or it can't wildly guess at a state of charge.

 

That's the correct technical language I think :)

 

[WotEver]

24 minutes ago, TheBiscuits said:

Yes.  Your MICC needs to see the sunshine coming into the batteries or it can't wildly guess at a state of charge.

And once you’ve done that you can safely ignore the wild guesses

[Tony Brooks]

2 hours ago, Midnight said:

Hi 
I added two solar panels which seem to be working fine. I followed the manufacturers instructions and took both cables from the MPPT controller direct to the battery terminals. I've noticed that on the Mastervolt MICC reading the battery voltage is up around 13.2 volts but the capacity reads at only about 21%.  I switched the shore power on and charged the batteries overnight but the capacity only went up to around 31% despite the batteries being fully charged.

Presumably the battery capacity works on some kind of bean counting system so should I have taken the negative cable from the controller to the shunt instead of the battery terminal?

I think that is the bit Wotever was saying yes to.

 

The second part of his reply was, I thin, referring to the fact the MICC, being an amp hour counter, will tell every larger porkies re state of charge and "time left" unless you really understand their set up and have done t. Then its vital you regularly get the batteries fully charged and resych the MICC. If you do not do this and you actually believe the MICC you will destroy your batteries in short order.

 

Remember that for the average boater using such monitors the only readings you can trust are Amps, Volts, and amp hours discharge.

[Midnight]

Thank you for the replies
I never thought the MICC capacity was that accurate but it is comforting to see it read 100% after a day's cruise. Seeing only 20%/30% is psychologically harmful. even though you know 13+ volts is pretty much charged.

I will change the negative and connect it to the shunt (on the non-battery side?) and reset the MICC (although I think it does that itself eventually when the batteries are fully charged)

[TheBiscuits]

Just now, Midnight said:

I will change the negative and connect it to the shunt (on the non-battery side?)

Yes.

[WotEver]

34 minutes ago, Midnight said:

... even though you know 13+ volts is pretty much charged.

But it isn’t.

 

A charging current of 1% to 2% of the battery capacity at a charging voltage of 14.4V+ is nearasdammit fully charged. So 4-8A for a 440Ah bank etc. 

 

 

[Tony Brooks]

12 hours ago, Midnight said:

Thank you for the replies
I never thought the MICC capacity was that accurate but it is comforting to see it read 100% after a day's cruise. Seeing only 20%/30% is psychologically harmful. even though you know 13+ volts is pretty much charged.

I will change the negative and connect it to the shunt (on the non-battery side?) and reset the MICC (although I think it does that itself eventually when the batteries are fully charged)

And 100% is definitely battery destroying on typical boats, especially if the reader thinks 13V can in any way indicate anything more than the battery has surface charge that must be removed before the voltage readings can in any way indicate state if charge.

 

When on charge use current to tell when the batteries are more or less fully charged as Wotever said but make sure the charging voltage is in excess of 14.2 volts. That will probably take many, many hours and a charger will probably drop to float voltage long before they are fully charged - as may a solar controller.

[Tony Brooks]

To add to my reply above:

 

How does the MICC determine the current capacity of the batteries?  If it can't as I believe and as the capacity gradually reduces in normal use percentage charged and hours left can never be accurate even if it does self calibrate when it thinks the batteries are fully charged..

[Midnight]

4 hours ago, Tony Brooks said:

To add to my reply above:

 

How does the MICC determine the current capacity of the batteries?  If it can't as I believe and as the capacity gradually reduces in normal use percentage charged and hours left can never be accurate even if it does self calibrate when it thinks the batteries are fully charged..

I'm no expert on electrics but I've had this system for 15 years and changed very little apart from the battery type and the AH setting when I changed the batteries about 5 years ago.

 

This is from the manual you may understand it better than I
"A battery is considered fully (100 %) charged if:

1. All of the Ah's discharged are charged back into the battery plus 1 Ah (real counting without CEF).

2. The charge-float voltage is met (the voltage is usually set around 14.0/28.0 volt).

3. The charge-return current is met (the charged current will be usually be set for 2 % of the installed battery capacity). If all the above parameters are met for a few minutes, the reading of the Ah's consumed will be reset to 100%."

Edited June 26, 2019 by Midnight

[Alan de Enfield]

11 minutes ago, Midnight said:

I'm no expert on electrics but I've had this system for 15 years and changed very little apart from the battery type and the AH setting when I changed the batteries about 5 years ago.

 

This is from the manual you may understand it better than I
"A battery is considered fully (100 %) charged if:

1. All of the Ah's discharged are charged back into the battery plus 1 Ah (real counting without CEF).

2. The charge-float voltage is met (the voltage is usually set around 14.0/28.0 volt).

3. The charge-return current is met (the charged current will be usually be set for 2 % of the installed battery capacity). If all the above parameters are met for a few minutes, the reading of the Ah's consumed will be reset to 100%."

 

Personally I'd rather see the (2) set at 14.4 volts (assuming FLA batteries) and the (3) set at 1.5%

 

Is it 'owner programmable' ?

[cuthound]

37 minutes ago, Midnight said:

I'm no expert on electrics but I've had this system for 15 years and changed very little apart from the battery type and the AH setting when I changed the batteries about 5 years ago.

 

This is from the manual you may understand it better than I
"A battery is considered fully (100 %) charged if:

1. All of the Ah's discharged are charged back into the battery plus 1 Ah (real counting without CEF).

2. The charge-float voltage is met (the voltage is usually set around 14.0/28.0 volt).

3. The charge-return current is met (the charged current will be usually be set for 2 % of the installed battery capacity). If all the above parameters are met for a few minutes, the reading of the Ah's consumed will be reset to 100%."

 

1. Is certainly not correct. Typical charge efficiency for a lead acid battery is 10-15%, but varies according to battery type and depth of discharge.

 

3. Is the most practical method of determining when a battery is about fully charged. A battery is not truly fully charged until the tail current has dropped to the level of the batter's internal self discharge current, but this could take 24 hours or more to achieve and is thus impractical for most.

[Midnight]

1 hour ago, Alan de Enfield said:

 

Personally I'd rather see the (2) set at 14.4 volts (assuming FLA batteries) and the (3) set at 1.5%

 

Is it 'owner programmable' ?

Some of it is. I have AGV batteries which isn't a preset option so I use the Gel setting.

I'm not sure but I think 2 only controls the Mastervolt charger

 

After 15 years I'm happy with the system but will reconnect the solar negative cable to the shunt and fully charge the batteries on shore power.

 

Thank you all for the info.

[WotEver]

As above really. 1) is miles out, 2) is too low, 3) is too high for an ideal setting. Having said that, those settings will work (3 is the most useful), won’t give you optimum battery life but will save engine hours. 

[Midnight]

I relocated the MPPT negative from the battery to the shunt and within minutes MICC capacity shows 100%.

Thanks for the help.