Does a regulator stop reverse current at night?

Just another quick question about the solar panel that I've now got bolted to my roof. You've probably been asked this load of times before, but just to clarify - does the panel drain the batteries at night? According to my battery monitor, I am losing some power overnight (a few percent of the charge according to the Smartgauge) - I don't know if this is because the power is actually leaking back through the panel, or because the batteries are just settling down somehow (obviously, I've got no idea about the technicalities behind all this). Is the regulator supposed to act as a diode to prevent this, or should a separate diode be fitted between the regulatorand the batteries?

Thanks, Jon

You don't need a diode when there is a regulator - it stops any power leaking back through the panel.

Batteries do slowly self-discharge of their own accord, so you would expect the charge to drop a small amount overnight. As long as it's only a few percent there is nothing to worry about. If it's a significant amount, either your batteries are getting old and tired and losing charge more quickly - or there is something else draining power on the circuit.

However, it certainly shouldn't be the solar panel draining power if it's going through a regulator - that should prevent any reverse current.

Andy, Midsummer Energy

Losing charge through a Sunsaver controller?

Andy I think the Morningstar SunSaver solar regulator SS10 is draining my batteries at night. Every night I read the volts on the solar side -.04, -.09, -.16 ; No load on 2 x 85amp leisure Batteries in parellel.  Batteries increase around .25 volts a day and topped out at 13.29 yesterday night then dropped to 13.09 tonight.

What's your verdict?

What are the best batteries to use with the Kyocera 130 watt solar panel?

best regards, Scott

Hi Scott,

If they are only dropping to 13.09V there is nothing to worry about! Anything above 12.8V for a 12V battery is basically as fully charged as you can get it. Although the voltage will rise slightly above that during the day while charging is happening, it's quite natural for it to settle slightly overnight even if there is no load on the battery. If it was going down to 12.5 or so without any load on the batteries I would think there was a problem - but over 13 is a very healthy battery!

You do always measure a small negative voltage on the solar terminals when they are not receiving charge - if you actually measure the current along that wire however you should find it is negligible.

Standard leisure batteries like you are using are absolutely fine for use with that panel. They should last at around 5 years or so if they are kept well charged - which it sounds like yours are. 'Sealed' or 'gel' batteries would last longer - but they are so much more expensive that it's not really worth it.

A bank of 2 85Ah batteries is fine, but on the smaller end of the bank size I would recommend - you could easily add another couple of batteries if you want to have a bit more reserve for times when you are using the power heavily.

Hope that helps,

all the best,
Andy

Multiple regulators on one battery bank

Hello. I have 2 sets of solar panels (200W each) with their own regulator, and a wind generator with its own regulator. However they are not all charging efficiently. Even though the battery bank is fla,t when it is sunny and windy the wind regulator slows the wind gen down and one solar reg beats the other down. So I am getting maximum recharging from only one source not all 3. I think the regulators are sensing the charging voltage of the dominant regulator and thinking the battery is fully charged. Any suggestions? I have been looking for a regulator to manage 3 inputs (and 2 outputs would be good) but can't see any. Could I wire all 3 regulators to a 4th regulator for the bank? Thanks. Stephen.

Hi Stephen. You are right that whenever you are charging a battery, the voltage will increase, and therefore any other charging sources attached to the battery will see a higher voltage and think the batteries are slightly more highly charged than they actually are. That's pretty much unavoidable.

The effect should not be very large, however, and it's not necessarily a bad thing, as it prevents overcharging. PV arrays trickle charge batteries, and with a healthy battery bank and decent sized cables between the battery and regulators, you shouldn't see a massive voltage increase. If you are - if they are cutting out even when you think the batteries are flat - it's suggesting the voltage is rising above 14.4V (the usual cut off), even with a relatively low charging current. That suggests to me that the batteries are on the way out.

Regulators are designed to be used in parallel in the way you have them wired, so I very much doubt you will find any difference if you do change the regulators. Trying new batteries is in my opinion far more likely to give you good results.

Hope that helps.

Can I use a solar regulator to regulate a wind turbine?

Just having a look on your website for wind turbines and regulators etc. You suggest that you can connect up to 100W of solar panels into the wind turbine regulator in addition to the turbine itself.

Does this work the other way? ie. Can I plug a wind turbine into the solar regulator I already have?

I'm fairly sure the answer to this is no, from my memory of wind turbines they actually produce AC voltage by induction, is this still the case or do they now produce DC voltage direct?

Yours realising just how long ago it was that I last looked at electronics!!!

Neil

Hi Neil,

You're right that it's not a good idea using a solar regulator for a wind turbine - but it's for slightly more complicated reasons! Yes, turbines do produce AC by induction, although in fact it's normally rectified in the turbine itself so it's usually unsmoothed DC that comes down the wires. The problem is more to do with what happens when a regulator senses a battery is full. Most solar regulators will simply open circuit, which is fine for a solar panel. But an open-circuited wind turbine will spin freely, which is bad news in strong winds. So a turbine regulator is usually designed to short-circuit the turbine, which slows the blades down.

Also, solar regulators might not like the relatively spiky DC from the turbine compared to the very smooth DC from a solar panel.

Having said all that, you might get away with it in places that aren't too windy - but it's not really recommended by the professionals! You are likely to shorten the lifetime of your wind turbine.

Tristar regulator and battery monitors

We have just installed 7 x170w 34v solar panels and we need a regulator. Would the Tristar TS 60 be too big?  Also we have two other regulators for other panels - is there a monitor into which we can feed all the solar info to give us one lot of information on charging, battery status in % or amp hrs?
Sally

Hi Sally,
I'm slightly confused - 34V is an unusual voltage for a battery-powered system! Big panels such as those are usually used for grid-connected systems, where you produce 240V AC (domestic electricity). In those cases you wouldn't use a regulator such as the Tristar; instead you would use an inverter.
If you have a battery system, it would usually work at 12 or 24V DC. If it's a 12V system, your panels are really producing too high a voltage. But, if what you have quoted is the maximum voltage (usually given as 'Vmax'), they are about right for a 24V system. You have a total power of 1190 W (7 x 170), which at 24V is still a bit under 60 Amps. So yes, if you are running a 24V system, the Tristar 60 would be perfect.
You can get battery monitors to give you the state of charge of your batteries. For 12V systems the NASA BM-1 is very good (http://www.nasamarine.com/). I think Steca make a similar instrument for 24V systems - if that is of interest I can get you more details. At the moment we don't stock them, but we may be able to get one in.

Two seperate charging systems

Hello, I have a 50 watt panel and a 130 watt panel, is it possible to wire them both to the same batteries (560 ah)possibly through 2 seperate charge controllers which I have.The 50 watt system is an older system and batteries are suspect where as the 560 ah system is new and could easily take the 2 panels if they can be used together.

cheers, Steve

Yes, it's usually absolutely fine to wire two seperate solar panels to the same battery bank. You could either use two seperate solar regulators, or you could even wire both panels to one solar regulator - as long as it is rated for sufficient current. In your case, that would be 180 watts(130 + 50), divided by the battery voltage (12) - 15 Amps.