Charge controller set point (solar panel)

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trophy160

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Can anyone advice the battery voltage at which a charge controller should 'allow' the solar panel to start charging. I fitted a new system today and noted that the battery voltage had to drop to 12.5 volts before the solar panel started charging. This seems wrong to me.
 
trophy160 said:
Can anyone advice the battery voltage at which a charge controller should 'allow' the solar panel to start charging. I fitted a new system today and noted that the battery voltage had to drop to 12.5 volts before the solar panel started charging. This seems wrong to me.
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Which controller is it? Some have a threshold voltage and will not start charging until the panel reaches a pre-determined point.

Obviously, as a general point, no battery will start to charge until the voltage from the regulator/panels is higher than the battery voltage which could easily be 12.5 volts.

Richard
 
I have a basic on/off solar controller dual output for charging 2 batteries,always charges the lowest voltage first then charges both when equal voltage.
Stops charging when 14.4 volts and when voltage drops to about 13.2 starts charging again.
 
RichardS said:
Which controller is it? Some have a threshold voltage and will not start charging until the panel reaches a pre-determined point.

Obviously, as a general point, no battery will start to charge until the voltage from the regulator/panels is higher than the battery voltage which could easily be 12.5 volts.

Richard
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So many questions for the OP to understand what he is asking. If it is as Pete says a hysteresis so it stops charging at say 14 v but does not start again until 12.5 then I would think it is too low. On the other hand I do not understand why they would have a hysteresis built in when for charging one usually sets a max limit of voltage and this becomes in effect the trickle charge level.
However all this assumes that OP has a large PV panel in lots of sunshine and the battery is indeed being fully charged then charge current is cut back. In practice with small panels and large batteries, not so much sun, the controller seldom cuts back current so system is doing its best which is not much. olewill
 
The charge controller was one of these http://www.ebay.co.uk/itm/20A-12V-2...462807?hash=item1eb5d21497:g:oq8AAOSwnQhXpF9x
I have to admit it was a very short test at the end of the day, the sun was weak and low in the sky so conditions were more like bright overcast. I have to admit that I do not know how off load voltage from the panel relates to in circuit voltage. Off load it was giving around 19 volts so I would have thought it should have kicked in before the battery dropped to 12.5v. It is also significantly lower than the float voltage of 14 volts quoted in the product description.
 
trophy160 said:
The charge controller was one of these http://www.ebay.co.uk/itm/20A-12V-2...462807?hash=item1eb5d21497:g:oq8AAOSwnQhXpF9x
I have to admit it was a very short test at the end of the day, the sun was weak and low in the sky so conditions were more like bright overcast. I have to admit that I do not know how off load voltage from the panel relates to in circuit voltage. Off load it was giving around 19 volts so I would have thought it should have kicked in before the battery dropped to 12.5v. It is also significantly lower than the float voltage of 14 volts quoted in the product description.
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If you're talking about a smallish panel in overcast conditions this country at this time of the year, I don't think it's a fair test for the system. The controller will be detecting a battery that is potentially well-charged combined with a very small current coming in from the panel and will determine that it doesn't make sense to start charging.

Try it again in direct sunlight with a rested battery voltage of 12.5V and see what happens.

Richard
 
It's a 100 watt panel, but your point regarding a proper assessment on a sunny day is well made, I just need that sunny day!
Nic
 
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