DEEP CYCLE BATTERIES and BUSH POWER

[condor22]

A Zener diodes primary application is to prevent flowback i.e. it only allows current flow in one direction). It's typical application is, when a solar panel is going through a controller to a battery it is charging and flowing in that direction.

At night, you do not want battery power flowing back through the controller to the panel, which it can and will unless a directional control diode is in circuit.

They sometimes can allow reverse flow, but only if the voltage reaches a certain point. So I do not think a Zener diode will limit the voltage in the direction of flow.

If you are still concerned, email Ctek and ask them what might happen if the input voltage exceed the charger/controller's rating...... (go to ctek's web page then click contact, it allows for an email messaging system.)

 

[PabloP]

A Zener diodes primary application is to prevent flowback i.e. it only allows current flow in one direction). It's typical application is, when a solar panel is going through a controller to a battery it is charging and flowing in that direction.

At night, you do not want battery power flowing back through the controller to the panel, which it can and will unless a directional control diode is in circuit.

They sometimes can allow reverse flow, but only if the voltage reaches a certain point. So I do not think a Zener diode will limit the voltage in the direction of flow.

If you are still concerned, email Ctek and ask them what might happen if the input voltage exceed the charger/controller's rating...... (go to ctek's web page then click contact, it allows for an email messaging system.)

An ordinary diode only allows current to flow in one direction (ie. not flow back as per your term) but a Zener diode is used as a voltage regulator, as when the voltage reaches its Zener rating the diode effectively breaks down and allows the current to flow back through it. Naturally you would normally place a resistor in this circuit to limit that flow and protect the Zener.

The drawing was copied from the following web site as it was easier than creating my own.

http://www.electronics-tutorials.ws/diode/diode_7.html

Rob

 

[condor22]

What is a Zener Diode?

Zener diodes are a special kind of diode which permits current to flow in the forward direction. What makes them different from other diodes is that Zener diodes will also allow current to flow in the reverse direction when the voltage is above a certain value. This breakdown voltage is known as the Zener voltage. In a standard diode, the Zener voltage is high, and the diode is permanently damaged if a reverse current above that value is allowed to pass through it. Zener diodes are designed in a way where the Zener voltage is a much lower value. There is a controlled breakdown which does not damage the diode when a reverse current above the Zener voltage passes through a Zener diode.


Taken from - http://www.futureelectronics.com/en/diodes/zener.aspx

What I originally posted above was simplified in context. A standard diode allows current flow in one direction. If over voltaged it will fail. A Zener diode has a lower reverse flow voltage and therefore has a protection for itself. This does not mean it will protect or reduce voltage to another device.

In regard to the original question of solar input exceeding a controller/charger's max input voltage, a diode, or Zener diode offers no protection or reduction of said voltage.

 

[Tathradj]

I was going to use a 24v 250 Watt panel with a tracking regulator.
The regulator in this case accepts a voltage/amperage much higher but limits the amount as per battery voltage/resistance.
Taking things into all consideration this would have been nice in a lot of ways but I settled for a 160 watt folding array with a 10amp regulator and leads all set up and ready to go. I did not have to much time before scuttling for Oallen.
Am rather impressed with the arrays performance but as always, There is room for improvement.
20amp regulator. I know that you only get max amperage in a small time frame but, Squeeze a bit more out of it.
Regulator close to battery, not 5 meters of cable after the regulator.
Proper post clamps on the battery, Not a small set of alligator clamps.
A better set of legs that do not let the array over balance. Small re engineering change here. LOL
.
Appearing on the forum shortly I will be posting a rebuild of a caravan that was given too me and it will be fitted out with solar. Stay tuned.

 

[condor22]

The basic calculation for regulator size is thus. (You don't specify panel voltage)

Panel watts divided by panel voltage = amps. So for a nominal 12 volt panel it would be around 18 to 19 volts, so to play safe assume 18

i.e. 160/18 =8.9A so a 10A regulator will work. However assuming a 24 volt panel is double the value would be <5 amps.

If the calculation is within about 10% of the regulator capacity, I would tend to go to the next regulator size up.

Why? Like all voltage modifying devices, solar regulators get hot. The closer to capacity, the warmer they get and in our climates hot weather, I prefer to err on the safer side and increase the size. Plus if at some future time you want to add a panel, you don't need to change regulators.

The other aspect is that once it becomes a charger at the output, you need to consider the battery size.

i.e. you would not want to charge one 100AH battery off a 50A regulator, it's too harsh a charge.

 

[jon_m]

If you are still concerned, email Ctek and ask them ...

Have emailed Ctek. Shall post their response. Thanks for the detail. Have become quizzical re putting another regulator (or whatever) to protect the Max 22v input, when baintech.com.au say that using a solar panel with a built-in regulator "will be unable to charge" through the Ctek D250S Dual. So, shall be interesting to hear what they say about it.

 

[condor22]

If you are still concerned, email Ctek and ask them ...

Have emailed Ctek. Shall post their response. Thanks for the detail. Have become quizzical re putting another regulator (or whatever) to protect the Max 22v input, when baintech.com.au say that using a solar panel with a built-in regulator "will be unable to charge" through the Ctek D250S Dual. So, shall be interesting to hear what they say about it.

You can charge with any suitable panel, but as I said before you don't regulate twice. I'll post a mod that explains how you can use a panel with an inbuilt regulator to power a CTEK or a Redarc dual.

To follow.......

 

[condor22]

This is for a folding solar panel with 2 halves. If a single panel you only need 1 lot of connectors.

You will need 4 x Andersons for the panel and 3 more for the fly lead in the external regulator option. (I have assumed the main outlet lead has an Anderson provided, if not you will need a couple more.

 

[Westaus]

Hi Condor, just wanted to say a big thanks for all your effort in this topic. Without it I would have made a lot of mistakes (still made plenty) and been confused with the whole process. Now the thread didn't help with any techniques nor tips ! which after many frustrations my work still looks like a pre-schoolers homework for mum and dad haha. However it has been good to learn and understand the whole process. I wish I had videoed my first effort at putting an Anderson plug together, how I didn't end up with a 6" puncture in my leg I will never know.

The variation I have done instead, but still working on the same principal is. I have hard wired both solar panels (120W 2x60W)(80W 2x40W) bypassing the regulator as in picture 3, these are wired the same on both panels. Except I have removed the Anderson plugs altogether from the panels and have a twin power out Anderson on the lead out, no regulator.

I then took out the regulator, which had dropped off from them using double sided tape and have made up the exact whip lead in diagram 3 but it is mobile, I am about to mount it into a small box and it will be a little portable 12V solar charger I can move it directly to my friends car near his battery and he just hooks up a solar panel, I am loaning him my 80W set, I will use the 120W as I run the fridge and a bit more electronics etc..

Doing it the above way solved a couple of issues, it took some weight from the panel directly, it also reduced the cost in Anderson plugs from 7 down to 4. It also took the regulator and moved it closer to the battery as was suggested so it works more efficiently. Overall this I believe will work well, the only two negatives are that I forget to bring the lead and/or it gets damaged by not being on the back of the panel.

All of the back up batteries are not connected to the main vehicles at this stage, I will be using a ctek D250S Dual and my mate will use the solar charger as stated above. We are doing a quick run in two weeks just to test the system and have a look for our next big trip. I will then hard wire everything in as needed but want to make sure everything is working, plus budget says hold on that final step.

Just to give another variation to the above but still achieve the same result ? I hope :8

 

[condor22]

In any design solution there are many versions, so long as the desired result is achieved, none are wrong.

Your solution has converted regulated output to none regulated and is not easily reversible, my solution is easily reversible. They both achieve the required result.

More effort and or cost are also factors in design solution.

If I had a permanent regulator in my caravan, I would chose your option, but at this point I don't. Actually on thinking again I would still chose my way, because although my can may be installed with it's own regulator, I would still want the portability of a self regulated panel for other use. So would want to easily swap back.

Everyone's needs differ, but the logic used is very similar, the trick is to sift out what matters to you, use it and discard the rest.

I once had a guy out bush tell me that he powered his inverter off of the battery, but only whilst he had the generator going, because he didn't want to flatten the battery.

In fact, this works, but my logic was; A generator produces 12 VDC and is then inverted to 240VAC which then feeds a 240VAC charger which converts to charge a 12 VDC battery, which then feeds an inverter to convert back to 240VAC. That's a lot of efficiency loss. When all you need do is plug your 240VAC kit straight into the genny and forget the inverter until the genny is turned off.

That's an extreme example of 2 solutions that both work, but in different ways.

BTW when I told the guy how I would do it, he answered "Crap, I never thought about doing it that way!"

Go figure......

 

[wooly]

Thanks. VOC it is. Just hate to think if I had one of the panels like in the first (eBay) link outputting VOC 21.6 volts, and then got some sort of spike it could do the Ctek charger in. Maybe there's some sort of voltage limiter (just googled; would that be a zener diode?) that would ensure no voltage above 22 v could hit the Ctek?

I really don't think you need to worry about a spike.
What you do need to worry about is the panels temperature coeffecient.
Solar panels increase their voltage when the cell temperature decreases and decrease their voltage when the cell temperature increases,
So the colder your panels are the higher the voltage will be.

Solar panels are tested at standard test conditions (STC) which is 25 degrees Celsius and 1000 watts of solar irradiation per square meter
In the specs for the solar panel should be a Temperature coefficient of VOC expressed like this -0.31%/. Any good solar panel should have this in their spec sheet. The temperature coefficient is the amount that the VOC increases or decreases by with every degree of cell temperature rise or fall.
So to determine the maximum VOC you need to know what is the coldest temp that the panel will be in and apply this formula.

Vmax_oc =Voc_STC+[voltage temp coeffecient x (Temp _min - Temp_stc)]

=21.6+[-0.14 x (0-25)]
=21.6 + (-0.14 x -25)
=21.6 + 3.5 = 25.1 VOC @ zero degrees celcius which would be to high for the Ctek.

Depending on where you live your panels cell temps may never get down that low or they may get lower if you lived of Kosciosko or similar.

I have not done these calculations for quite a while and think they are correct. Unfortunatly the panels you have mentioned on ebay do not show the Temp coeffecient so I have just made one up in the formulas.

 

[Tathradj]

And I failed to mention
Thank You for your input into this subject Condor22
Very Much appreciated.

 

[condor22]

Adding to what Wooly has said,

Mono Crystalline Poly Crystalline and Amorphous cells all react differently to temperature and are not the only type available.
A good explanation of the various types can be found here.

http://energyinformative.org/best-solar-panel-monocrystalline-polycrystalline-thin-film/

As Wooly points out there are voltage differentials vs ambient temperature. Mono and Poly panels drop off the hotter they get. Amorphous, such as the Unisolar work better in hot temperatures, but they are expensive and a bugger to keep clean.

The basic advice I would give is;

• Get the best panel/s you can afford[/*]
• Use a good quality regulator with a reasonable input voltage range (Redarc =9VDC to 30VDC)[/*]
• Use a regulator that will accept the amperage output of the panel/s, but, that matches the battery or batteries AH rating.[/*]

Along with all of this is the order in which a system is designed; (previously noted in this thread);

• Calculate how many AH you will use in 24 hours (or what you think will be the time between charges)[/*]
• Multiply this figure by at least 2, but preferably 4, to calculate the AH rating of the deep cycle battery required. This is to calculate 25% to 50% cycling of the battery.[/*]

Then, look at charging as the next step, wether it be by 240VAC to 12VDC, 12VDC to 12VDC or solar. Regardless of the method, you need a charger that charges between 10 and 20% of battery capacity. Any less than 10% and you will be there all day, any more than 20% is probably going to reduce battery life.

My logic is this, A good battery, requires a good charger and a good charging technique. If you skimp on quality for cost or ignore technique, you will most likely need to spend more money and time to fix a problem. And, problems usually happen when you are out bush wanting to use the kit.......

 

[jon_m]

If you are still concerned, email Ctek and ask them ...

Had a reply this a.m. ...

Hi

You can have a maximum of 23V. Most likely a zener diode to interfere with or block the charge. Ask the supplier of the solar cell, what it gives in the voltage, it is under 23V, everything is ok.

Best regards
Pierre

PIERRE LFGREN W W Sale Support
CTEK SWEDEN AB ROSTUGNSVGEN 3, SE-776 70 VIKMANSHYTTAN, SWEDEN
PHONE: +46 225 351 80 DIRECT: +46 225 351 91
FAX: +46 225 351 95 MOBILE: +46 70 3880191
WEB: www.ctek.com EMAIL: [email protected]

"Most likely".... wish there was some certainty. I can stitch & glue some wire but cannot get my head around why the Ctek seemingly cannot have something to block voltage above 22v (now 23v) and insure the charger is not harmed. . %$@#(()^$%#

Well guess there is a trick - just not a zener diode - but maybe by trial and error?

 

[condor22]

Jon

Do you already have the Ctek and panel?

 

[jon_m]

Have the Ctek D250S Dual but no panel as yet. Maybe a generator would be the way to go??

But I'm having to re plan things a bit - just taking possession of an old Viscount (unexpectedly). My setup with tent and v small car is being knocked about. Now I'll be laid up rewiring new lights onto this old van, and getting it ready for a RWC.

Thanks

 

[condor22]

There is another option, depending upon panel wattage size. That is to use the CTEK too charge from the alternator, but not solar.

Then get a separate regulator to suit whatever panel/s you end up getting.

 

[condor22]

I ran my TV and 3 LED down lights off the van battery for 6 hours to simulate what I might use at night in the van. I haven't yet included electric blankets, because I need to do some more wiring for my inverter. To remind, I have a 100AH GEL. Here are the results

After 6 hours as above the battery state of charge (SOC) was 76%, so 24AH used, battery no load was still 12.7V, battery temp was 30deg.

At start of charge (15A Projecta smart charger) charge amps = 14.7, (boost mode) voltage = 13.8

50 minutes later SOC = 89%, charge amps = 10.9A (so now in absorption mode), volts = 14.2

at 2 hours of charge SOC = 95% charge amps = 3.2A volts = 14.1

at 3 hours SOC = 100%, amps = 0.8 (now in float mode), volts = 13.8 (I should have checked at 2.5 hours in hind sight, but was watching TV, lol.

From this I can establish that 25% of battery use from 100AH will take 3 hours or a little less to fully charge the battery.

And, because any more than 25% usage will recharge in boost mode, every 5 AH extra use will take about 20 minutes more charging time.

I'm happy with that, 3 hours of genny idling away is fine with me. Consider also that if I start the genny at 5pm, 3 hours of lights and TV are not being powered by the battery, so usage will be half of the 24AH I did use and this extra 12AH can go toward other use such as my inverter.

Next test to include the electric blankets off of inverter. What I would do here is heat up on full while genny is on then turn to low once genny is off to keep the bed warm.

 

[Westaus]

In any design solution there are many versions, so long as the desired result is achieved, none are wrong.

Your solution has converted regulated output to none regulated and is not easily reversible, my solution is easily reversible. They both achieve the required result.

More effort and or cost are also factors in design solution.

If I had a permanent regulator in my caravan, I would chose your option, but at this point I don't. Actually on thinking again I would still chose my way, because although my can may be installed with it's own regulator, I would still want the portability of a self regulated panel for other use. So would want to easily swap back.

Everyone's needs differ, but the logic used is very similar, the trick is to sift out what matters to you, use it and discard the rest.

So true, in thinking as well, I believe for the extra few dollars on plugs your way would have been SO much easier. Anyway done now and we will see how it goes in a fortnight yah. Thanks again mate.

 

[condor22]

Had a think about the inverter, I don't and won't use a big one, anything over 150W I'll use the genny. The only 3 things in my van I would regularly use the inverter for are the Blue Ray player, the satellite receiver or the electric blankets. I can also charge things like, detector battery, tablet, phone, camera etc, but some of them I would charge via the 2 USB charging points I have already installed to the van or 12 volt car or van.

Problem - The inverter is a 150W Projecta pure sine wave, it has a short inlet cable with a cigarette plug on the end. Most cig sockets are rated to 120W or 10A at 12VDC, so it's a bit too much current for my liking. Plus, near my TV I only have 1 cig socket (the only one inside the van), I use it for the TV at all times. If I use a double adaptor and all of the inverters 150W, I'll load up to about 220 watts (18-19 amps). Given the distance from the TV to the battery, I don't think the cable to the cig socket will handle this.

Solution - Add another shorter wiring run near the battery to a different kind of plug/socket and fuse to 15 amps.

Got these from Jaycar this morning. So will put the socket on the outside of the dinette seat where the battery is, using about 1/2 a metre of 6mm cable with inline fuse holder and wired to my battery monitoring system.

I have 2 choices with the inverter for the plug; cut the cig plug off and re-terminate with the new 2 pin, or, make up a small patch lead with the 2 pin on one end and a cig socket on the other. I'm inclined to do the latter as I can still plug the inverter into my 4x4 auxiliary cig socket which is already wired and fused to 15A.

The inverter can then feed a 4 way power board, for the items I want to use off the inverter. The blanket has 2 plugs, 1 for each side. All ok, so long as no more than 150W. Running a 2 metre extension on 240VAC to the bed or satellite receiver is not a problem re voltage drop.

Will look at this in the next day or 2, that should be pretty well be all the mods I need for now, so will post pics of the setup when done.

After which I'll test various power consumptions (blankets, blue ray and satellite) so I'll know the limitations before my next bush bash.