solar power

You would actually have to put a bit more in, however, it is unlikely your fridge (hopefully a compressor one) will draw 3 amps per hour on average. Most seem to do about 2. Which is 28 Ah in a 24 hour period. I have a 60 and a 30 watt panel, the latter mounted on the roof of the car and therefore not "steerable" On our last trip I managed to get a maximum 15 Ah a day out of this setup, that is by moving the 60W panel to produce the best output.
It is not easy (you need at least 2 80W panels) to be totally self sufficient for longer periods. I can go for about 3 -4 days without starting the engine and I have an 80Ah and a 100Ah aux batteries.
It will take about 6 to 8 hours driving to recharge after they are run down. I do run a HF radio as well and that has an effect but it is not on for long periods of time.
Cheers

The amount of extra current you have to supply to recharge a battery depends upon its construction. It is explained by PEUKERT'S LAW

Richard, I totally DISAGREE with your entire post, on your "members rig & profile" you do not mention a Solar power system, just a triple battery system, so I can only assume you don't have a "quality" Solar power system installed, your post miss-information actually indicates that also.

A Solar regulator will NOT "regulate down" 3.33 Amps to 2.5 Amps in the way you have posted and Amps are only regulated to the battery to suit the battery 'State of Charge'

A quality Solar regulator works in exactly the same way as a 3 x stage 240v battery charger works.

My Solar system charges my battery system from sun-up to sun-down 24/7 365 days a year, peak hours is just that the "peak" hours of the day where you will have "full solar capacity" available, I checked at 9.27am today to give you some relevant facts.

Here in Dunsborough in the far South West of West Australia there is 6.2 Amps being produced at my Solar system, which is attached flat on a roof-rack on my vehicle, it has a capacity of 12+ Amps, only 1.2 Amps is going to the battery, because the battery system is at 99% State of Charge @ 13.8v, the fridge is showing 2.1 degrees so has recently turned off.

Any factual information you require - ask :-))

Yep Mainey ,got to aggree ,some people have no idea of the actual use of solar , peak hrs ect that they only read about in a book , in Brisvegas today at 8.30am my panels [64 unisolar +120 kycera] were producing 11.42amps with my batts only taking in .02amp as state of charge better than 99% , at 4pm, like 10min ago the panels were producing 10.98amps with o going into the batts as state of charge is 100% and "steca" in float mode 13.8v.

You can read all the books / spit out all the so called learnerd information and you can call it gospel , and yes you are wrong , pray tell us all what magic 12volt commpressor driven fridge freezer you run that you by your own maths get to run for a total of 13days from your battery without recharge , as you plainly state YOU have no solar so you only know what you assume to be the case , you HAVE no REAL knowledge of solar in practical use. IE: you dont even know the correct charging voltage supplied by a solar regulator ,13.8 is the Float not the charge.

Richard

Where you have gone wrong is you are using the maximum total watts as your basis for your calculations and doing your calculations in watts. What you should be doing is to work off the voltage/current curve that applies to a particular panel.

To obtain the voltage vs current curve you need a variable resistance (load.) As you vary the resistance, when you reach the point where the product of the voltage and current is at its maximum (maximum power point) the output voltage will be in the range of 17 to 18 volts. If you increase or decrease the resistance the voltage/current product will drop. When decreasing the resistance the voltage will rise but not as fast as the drop in current. When you increase the resistance the current will rise but not as fast as the voltage drops.

When you are charging a battery (assuming no load is being drawn at the time and the battery is flat enough to absorb all the current the panel is capable of producing) then the voltage across the system will be governed by the state of the battery. This will be in the range of something less than 13V to something more than 14V. You can not calculate the current the battery will draw. You have to read it off the graph that applies to your panel. What I can guarantee is that the current drawn will be equal to or more than the specified current at the maximum power point, unless the temperature is extremely hot. Now you have a little grasp of the current and voltage dynamics of a solar panel and you know they do not have a linear relationship you can get hold of some curves, redo your calculations and report back.

PeterD

Richard,
yes unfortunately I also have to suggest you’re wrong !!
Basically for the fairly complex reasons used above by Peter.

IMO there is no more EFFICIENT way of FULLY recharging a "storage battery" system than by a 'decent' Solar power system.


Don't get 'hung up' about "numbers" they can be construed to mean so many different things when stated in different formats.

If you use an 'Elcheapo' Solar PANEL, Solar REGULATOR or an inefficient STORAGE BATTERY system you will get inferior results as shown in your post.


EFFICIENT Solar systems SHOULD recharge the Storage Battery fully during the day.
Only during the night the battery system has to run the fridge and lights etc.
Next morning the battery system will be FULLY charged again - before lunch.

The fridge will be drawing power from a fully charged battery system ALL day, as an efficient Solar system should be capable of replacing more power into the battery than is drawn from the battery.
( Yes, when the fridge is actually running, there should be an excess of Solar power recharging the Storage battery system )

If this is not the scenario then it’s clearly only a “toy” and IS undersized.

I have been using Solar 24/7 since 1996, so yes I have a little bit of actual genuine hands-on experience that was not learnt in a book. I also cel & install the 'stuff' so why would I even consider second rate gear for my own use.

Once you buy the Solar panel/s and a "quality" Solar Regulator there is no further ongoing costs associated with it's use, and a good genny is about the same cost as a decent solar system anyway, with-out all the benefits associated with Solar power.

Only those using a Solar system will be able to give you their own accurate advice,

An efficient Solar system has 3 main components;
Solar Panel/s
Solar REGULATOR
Storage BATTERY system.

If there is a shortfall in any component the system is simply NOT efficient.

EfficientSolar power systems will NOT work in a moving vehicle :-)

Mainey

I am afraid I will have to disagree with you in respect to your last sentence. Sun light travels a a tad bit faster than your van does. It is only the portable ones you pack away that don't work whilst moving.

However, solar charging on the move will be reduced when you attempt to charge your batteries from the tow vehicles alternator without employing a voltage booster. A solar panel will charge a battery with 14.2 - 14.6V (depending on battery type setting.) A motor vehicle alternator has temperature compensation built into it. When the motor compartment heats the alternator output voltage is reduced, so that the warm battery under the bonnet battery does not get overcharged. The system voltage is reduced to a level below 14V. As a consequence, a cold battery that is remote from the motor compartment will not receive much of a charge.

When you connect your tugs electrical system to the system in your van, the tug's system will control the maximum voltage of the whole system. As this voltage is less than the solar systems maximum charging voltage your van's battery will receive less charge than if you leave the solar panel to charge it.

If you have a current meter in the solar input leg of your regulator it will indicate roughly the same current whether you have the tug connected or not. As your van's battery is not receiving as much current with the tug connected you will find the difference current is going bank into the tug's electrical system. If you don't believe me then put a current meter in the line and check this.

A good site to see the current a battery will absorb for different applied charging voltages ishttp://www.sterling-power.com/support-faq-1.htm

PeterD

Peter,
You have posted -> "I am afraid I will have to disagree with you in respect to your last sentence. Sun light travels a a tad bit faster than your van does. It is only the portable ones you pack away that don't work whilst moving"

Umm, yes, the sun does travel a LOT faster than me,
however, that's not relevant to the post lol.

What is relevant is that when you have the engine running, (driving the vehicle) and therefore the Aux battery is being charged by the Alternator, the Solar REGULATOR 'senses' about 14.2v to 14.4v at the Aux battery.

The Solar REGULATOR then shuts off Solar power to the Aux battery, because it's senses it as 'fully charged' and at most only a 0.5 amp (max) is trickling into the Aux battery, if any current at all.

When the engine is turned off and the Aux battery voltage is reduced, maybe by the fridge running, the Solar Regulator will then allow current to enter the Aux battery again to replace the 'lost' voltage and maintain a float of ~13.8v or whatever the Solar Regulator is set to deliver.

The Solar panel/s are still 'making' electricity, it's just not being sent to the Aux battery by the Solar regulator, because the Aux battery is seen as 'fully' charged.


I use a Steca Solar regulator with a LCD screen which shows Amps going to the battery and also to the fridge, also in-line between the Aux battery system and the Solar Regulator is a 15 Amp (+) (-) Amp gauge, this shows Amps going both into the battery system and also out from the battery system.

Mainey

Solar regulators charge batteries at a higher voltage than Vehicle alternators do. When you couple your van in the morning the solar will be charging a battery that has been depleted from use overnight. The terminal voltage of your house battery will not be high enough for the charging current to reduce so that the controller will sense that it should drop to float charge.

Then you couple your van and start the motor. As the alternator voltage is generally lower than the solar system it will control the charge rate of the battery. As the total system voltage is lower, when the charge level of the battery rises, the charge current will fall off quicker than if it were allowed to be charged at a higher voltage by the solar system charging it alone. To add to the problem of reduced charge, when the motor compartment heats up, the temperature compensation in the alternator regulator will reduce the charge voltage even further. This in turn will reduce the current absorbed by the battery. If you had read through the page that I gave you the link to in FollowUp 4, you would have seen how much the charge current into a battery drops with a little reduction in applied voltage.

What I m trying to get through is that if you use panels large enough to charge your batteries when mounted flat on your van, you will get more charge into your battery than if you connect alternator to assist in charging them. Also you will get more charge into your batteries with solar panels than if you use an alternator alone – remember an alternator will only recharge your batteries to about 70% of their maximum capability. However it is possible to engineer a solar system to charge your batteries to nearly 100% of their maximum capability.

PeterD

In addition to my FollowUp 6, I am saying a solar system will work on the move. It will work even better if you do not attempt to use the tug's alternator to assist it with the charging of the battery.

PeterD

Peter,
Sorry, I can't agree.

I have actually checked early this morning by watching my Ammeter installed in-line between the Storage batteries and the Solar regulator and it was showing a constant 3.4 Amps going into the Storage batteries.

The AGM Storage battery Volts was showing as 13.8 Volts. (Normal)

I had some-one start the engine, after a few 'seconds' the Amps suddenly went back to ZERO, therefore indicating no Solar power was going into the Storage batteries from the Solar System.

However the Storage battery Voltage suddenly went 'UP' - from 13.8v to 14.4v.

I believe I can explain the "few seconds" by saying the Cranking battery was initially recharged by the Alternator.
Then the Rotronics battery Isolator closed to allow the Alternator to put charge direct into the AGM Storage batteries.

>You don't have to knock people down even if they are wrong
>or right

Hmmmm... I refer you to your earlier posts today Richard. We are all prone to make mistakes.

Mike Harding

Please read my FollowUp to Reply 6 regarding the dynamics of a solar panel.

You are a little astray in your understanding of battery charging too. The traditional flooded lead acid battery requires 14.2V to fully charge it. The new calcium/calcium batteries need up to 14.7V, the sealed batteries require less than 14.2V - consult the manufacturers specifications of a particular battery before putting mouth into gear or fingers into motion. The float voltage of a lead acid battery is in the range of 13.4 to 13.8V - again, consult the specifications. The standing voltage of a fully charged will be around 12.7 to 12.9V.

If you do not know what you are talking about, you really should not be going into print. You only contribute to miss understanding, confusion and arguments. You could be responsible for the destruction of equipment and even death of a person.

PeterD

Olcoolone,
You say -> "Our fridge draws 1.2 amps an hour and we use two 120 amp batterys in our hilux and we have 3 of the same in our trailer"

With a fridge that only has a tiny 1.2ah draw, why on earth do you need 2 x 120ah batteries OR 3 x 120ah batteries in the trailer ??

My 70Lt fridge/freezer is 2.8ah and happily runs on a ~200ah AGM battery system, charged by ~200watts of solar power.
The AGM battery system has never, repeat never, been below 12.0v at any time, day or night.
The fridge 'cut-out' is set at 11.6v and has never been activated.

IMO your system is total overkill, but obviously you must need it that large, because you would not have paid the $$$ for any other reason.

Peters 'float' numbers above are accurate!!

I'm not having a go at you, as there is so much rubbish printed even on manufacturers web sites about 12v 'stuff' - it makes you wonder how the hell the average guy gets any decent, reliable information.