solar battery charge controller, when does it cut out ??

simonfraser

simonfraser

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i think i nearly understand, but:
during the winter i am supposed to charge my lead acid battery to a float of 14.0V.
my (3rd !) regulator cuts out way before this, somewhere in the region of 13.0V.
my solar panel runs at 23.8V, so i have connected this direct without the regulator. this being the only way to drive the voltage high enough to put more charge in my battery.
today i have a float V of 12.9, so i have kept it connected and shall check again next week.
why does no one make a regulator to charge a lead acid battery a 100% ??
will my instruments expire if they are connected to ??? 15V or more ?
 
What sort of batteries do you have? (type and Ah) How big are the solar panels? Do you ever leave the boat with no load (fridge, etc.)? In which country is the yacht to be kept (e.g. are you planning to leave her in a very sunny country?).
 
What's happening is that at times the battery becomes somewhat discharged so when you visit the boat regardless of how sunny it is the voltage is clamped to somewhere between 12.3 and 13.0V and that voltage won't rise much until the battery is nearly fully charged. My suspicion is that the controller is fine. The whole system is pretty marginal and you have no way of knowing how much output current you will get.

To check the correct functioning of the regulator, try charging the battery with the engine or whatever so that it is up at 13.6V on charge, then disconnect the anchor light, stop the engine (or turn off the charger) and see what happens with just the sun and the regulator in circuit. If, as I suspect, the controller is fine then you will need to consider increasing the panel output or reducing your load. Can't you switch the lamp off during the day with a photo switch? Does the anchor light manufacturer make a switch? Otherwise you will find circuits to do this online, I am sure.
 
You sure 23.8v is correct for your system?? ,sounds very high ,have you got the panels in line or running in parralel???.
If you have them inline 23.8v will kill your 12v 110amp batteries.
The usual output range on solar panels even in the UK should be around 17/18v open (no load)circiut.
If you install a regulator for your system it will "float" at 14.2 for lead acid unless you program it differently yourself.
Check the specs for each regulator (ours is a Prostar30)
 
I think you might be right about two of the panels being in series - it does look very high.

I have a Prostar 30 which floats at 14.2 When I bought it, it was said to be a three stage charger and I expected it to fall back to 13.6 or so but it doesn't. Do you know how to programme it - my instructions don't mention it.
 
The voltage as measured with no load is usually around 20 volts. 23.8 means the manufacturer was generious in the number of cells fitted or your multimeter has a flat battery. 2 panels in series would give 36 to 40 volts in good sunshine.

A solar panel regulator in simple form is a wasting bypass or shunt regulator which simply begins to pass current from battery positive to negative when the voltage of the battery as pushed up by the solar panel reaches the preffered voltage. usually around 14 volts.

You have done the best test by connecting the solar panel without a regulator. This will push the battery up in voltage until it is fully charged then if there is enough current will start to boil the battery. If the panel is small compared to battery size then boiling will be insignificant. ie solar current less than 10% of battery Amp hour rating.

However this all is based on a lot of sunshine over a long period with the panel fairly big and set at right angles to the mid day sun.

You need an ampmeter to measure current out of the panel into the battery- no reg. This will confirm you have good solar panel and enough sunlight. You can expect a current of panel watts devided by 20volts or .5 amps for every 10 watts of panel.

I suspect at this time of the year in UK there is simply not enough sun. (says he typing at 8Am while expecting 30 degree max)

One last trick if you think you have enough sun and solar power but the reg is too low in regulated voltage you can fit a silicon diode in the negative line of the regulator. That is you connect the -ve of the panel to the negative of the battery. and a 2 amp diode or bigger for big panels, with anode on the negative terminal of the reg (if there is an in and an out connect them together) and the cathode ( head of the arrow or black band) of the diode to the negative panel and battery.

This should trick the regulator into thinking that the regulated voltage is lower than it really is so jack up the regulated voltage by .7 volt. You can use 2 diodes in series both the same direction to jack it up by 1.4 volts.

Will your instruments die if the battery voltage gets up to 15 volts. I dunno.... Smart regulators on alternators do this so apparently not. I often wondered.

I still think bottom line is the solar panel is too small or not enough sun or the battery is cactus. good luck olewill
 
hi olewill,

many thanks, the solar panels supply between 100mA and 800mA with winter sunshine. this is enough to run my LED anchor light and instruments for the weekly winter sail. glad to see that is not enough current to boil my battery dry.

during the summer i can get up to 1.4A but according to your 10% rule i still won't need a regulator ! simple. i'll watch the voltage though.

i have run the setup with a regulator and do not get enough charge in the battery, in fact it has a lower float V after one week, without the regulator it is slowely increasing in float V.

i like your diode trick, i'll put that in if the regulator is needed.

so, does the battery boil off the excess energy the solar generates ? what sort of voltage am i likely to see when it boils ?????????

enjoy the sunshine :-)
 
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