Solar Controller settings

A recent thread on Solar panels saw me check the settings on my PL20 controller.

All was correct, except that it was set for a 120ah battery whereas recently a new 105ah has been fitted.

As the PL20 jumps from 100ah to 120ah as the available choices my question is what to set the controller to?

Set at 100ah the controller will be undercharging the battery but at 120ah will be overcharging.

Is the difference too small to be an issue?

Paul
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Reply By: Peter_n_Margaret - Friday, Jun 11, 2010 at 10:14

Friday, Jun 11, 2010 at 10:14
The Amp/hour setting does not detirmine the ammount of charge that is applied Paul. It is only used to calculate the % state of charge. Set it on 100Ahrs.
The boost/absorb/float voltages are what determines what goes into the battery. These can all be set individually on program 4, or you can use one of the default programs, depending on your battery.

Cheers,
Peter
AnswerID: 420427

Follow Up By: Battery Value Pty Ltd - Friday, Jun 11, 2010 at 10:37

Friday, Jun 11, 2010 at 10:37
Hello Paul,

I second the other Peter ;)
I don't think it matters much in terms of actual charge being pushed into the battery.

I think the Ah figure has been made configurable so that the controller can display some meaningful SOC percentage depending on how much Ah go through the battery in both ways.

BTW, the specified battery capacity is not a rock solid constant.
It changes with temperature, and most noteably with battery age.
A perfectly healthy 5 year old battery may only have 80% of the original capacity left.
If it's been abused, then this figure may well be lower.
In both cases the solar controller isn't going to over or under charge it because the charge termination voltages remain more or less the same regardless of residual battery capacity.
But even these voltage levels can change a little over the life of the battery and could be adjusted by the OP when trying to get maximum service life out of the battery.
But for this to be successful the usage history has to be known, and actual values of internal resistance and float current requirement has to be known (and compared to the same set of properties when the battery was new).

F.e. if the battery was subject to frequent undercharging in the past, then the battery life would be limited by sulphation. If countermeasures aren't taken, this will cause other effects to kick in which shorten battery life even faster.
But if sulphation is detected in time, then this domino effect can be prevented by raising the float voltage to stretch its useful life a bit.

Best, Peter
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FollowupID: 690593

Follow Up By: Member - Andrew (QLD) - Friday, Jun 11, 2010 at 11:26

Friday, Jun 11, 2010 at 11:26
I believe Peter_n_Margaret answered the question simply and to the point without confusing the poor bloke. :(

Andrew
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FollowupID: 690600

Follow Up By: Battery Value Pty Ltd - Friday, Jun 11, 2010 at 11:34

Friday, Jun 11, 2010 at 11:34
haya Andrew,

I think you succumbed to the temptation, just as much as I do just now - how is that for confusion lol

...The real art of conversation is not only
to say the right thing at the right time,
but also to leave unsaid the wrong thing at the tempting moment...

Best, Peter
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FollowupID: 690602

Follow Up By: Member - Andrew (QLD) - Friday, Jun 11, 2010 at 11:37

Friday, Jun 11, 2010 at 11:37
I know LOL

but is it the wrong thing or the right thing to say ?? ;)

Andrew
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FollowupID: 690603

Follow Up By: Battery Value Pty Ltd - Friday, Jun 11, 2010 at 11:46

Friday, Jun 11, 2010 at 11:46
tell me the answer and I'll let you know if it's the right or wrong one :o)
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FollowupID: 690605

Reply By: Member - Ups and Downs - Friday, Jun 11, 2010 at 20:36

Friday, Jun 11, 2010 at 20:36
Thanks to all who provided the answer for me.

Much appreciated.

Paul
AnswerID: 420481

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