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Pete and Tracey

Battery and charging Q's

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Hi everyone,

Just wondering for those of you that free camp extensively, on a sunny day what voltage does your battery setup hold? We have just had a few sunny days and after the sun has set the batteries voltage settles at 12.8 - 12.9 V. The voltage drops to around 12 v at the end of the night running the TV and a 3G router. Not too much draw there?!? Is this right according to you? As they are being charged it reads 13.8 volts as expected. 3 batteries.

I had a look at the remote, PLM, and during the middle of the day there is 20 volts being delivered form the panels. Again is this what you should see? I have 4 130 w panels

Just wanted to get opinions, bit of a sanity check really

Thanks

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Pete and Tracey

From the point of view of a retired Electrical Engineer who has designed and run solar power systems for 20 years or more - a couple of points.

The difference between the open circuit solar panel voltage and the MAX voltage or system voltage you are reading at the end of the day is the potential difference available to drive current into your battery bank. Don’t bother about it, leave that to the regulator.

As the operator of the system on your Kedron watch two things.

State of Charge (SOC) and MIN system voltage.

Today’s small solar regulators are really Programmable Logic Controllers, called PLCs. In essence they consist of a bunch of counters fed by voltage sensors. To get to the SOC reading the PLC counts the Amp Hrs IN and the Amp Hrs OUT and adds em up. The SOC even though it has some inaccuracies is a fairly useful figure if you watch it over time, say a week or two. Interestingly if you read SOC one can at times see a figure above 100%, the Plasmatronic regulators can read up to 127%. How I hear you ask can a battery bank be measured at 127% of its rated capacity. The answer is that there are daily inaccuracies in the adding of the IN and OUT values that allow the figure to creep up. With the Plasmatronic regulators, hold the button for five seconds while reading SOC and the SOC figure will reset to 100%. Other brand regulators have resets as well.

Probably the most important thing about batteries is that to operate them in a deep cycle mode i.e. use a large portion of their rated capacity will unfailingly lead to a short battery life. This comment applies to all batteries, deep cycle included. I have 3 X 120A/Hr batteries in our Kedron so my overall capacity is 3X120=360 A/Hr. However when the SOC reads 75% I start the generator. So in other words even though I am towing around 360A/Hrs of capacity I only am prepared to use 25% of that or 90A/Hrs. When the van is parked up I use a trickle charge. Operating this way should give me good battery life.

As a backup measure of how the batteries are holding up watch MIN volts on your controller. On a typical Kedron setup it should almost never drop below 12V. An almost dead flat battery will quite happily read 12V with a multimeter across the terminals. One has to ask the same battery to deliver a substantial current and then read the resultant terminal voltage to detect a discharged or sulphated battery. It is called load testing. If you are seeing 11.6 or 11.8V at night after the evening load save up for buying new batteries.

Your panels at 4 X 130W have the theoretically capacity to deliver 43 Amps to the regulator, but they won’t do that. The efficiency of solar panels is highly dependent on their temperature. By the time the sun is well overhead they are quite warm and their efficiency will have dropped considerably. As a last point I will mention Peukert’s Law which has the effect of reducing the energy available from a battery. The conversion of an electric current form of energy to a chemical form of potential energy and then back to an electric current has a cost. The cost is described by Peukert’s Law. As a rule of thumb work on 90 to 93% of available solar output being available back at a load such as your DC light in the caravan.

In short monitor your SOC fairly closely, and more often during poor solar weather and use MIN voltage as a important backup indicator.

I hope this ramble is helpful.

Grahame

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Hi Pete and Tracey,

Grahame has covered the subject very well, but I thought I might add this...

You state that your batteries are "around 12 Volts" in the morning before solar charging commences. If around 12 Volts is actually, say, 12.3 Volts then that is a world of difference in terms of the state of charge of your batteries. 0.3 of a Volt doesn't sound like much but in a 12 Volt system it is a lot. See the table below:

SOC Volts

100% 12.7

90% 12.5

80% 12.42

70% 12.32

60% 12.20

50% 12.06

40% 11.9

30% 11.75

20% 11.58

10% 11.31

0% 10.5

As you can see, "around" 12 Volts is a 50% state of charge and 12.3 Volts is 70% state of charge.

I agree with Grahame that aiming for a state of charge no less than 75% is a good guide. This will ensure a long battery life. If you monitor the SOC as the evening progresses you will soon learn which appliances are pulling down your batteries and you can learn to ration their use accordingly (unless of course you wish to run a generator).

The 230 Litre Vitfrigio fridges don't draw a heck a lot of current but their duty cycle is an issue. To achieve safe food temperatures in our fridge it was running almost 100% of the time and was on the coldest thermostat setting to do this. After I insulated the fridge cavity with styrene foam I could hold the same temperatures with the thermostat on just one third of its range and a duty cycle of about 30%. In other words, my fridge was only running for about one third of the time and was off for 2/3 of the time.

Just insulating the fridge has made an enormous difference to our power usage and, as a consequence, the state of charge of the batteries.

I notice that Grahame didn't directly address one of your other concerns. When charging ceases the battery voltage drops from 13.8 to 12.8 or 12.9 Volts. This is absolutely normal. In fact, it will fairly quickly drop to 12.7 Volts before stabilising.

Hope this is of some help

Russ

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G`Day Grahame

Thankyou very much for your info on Panels and Batteries.That would have to be the clearest and most easily understood explanation for the system I have ever read.I usually get bamboozled on the second line of previous attempts to explain how every thing works. :confused1:

If you are game write the same explanation on caravanersforum.com. :thumbsup:

Thankyou again

Cheers

Rick & Lea

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Hey Guys,

Thanks for the replies so far, especially Grahame, I appreciate it. I did notice today that the 204v -> 12 v has been left on during our free camps. When I turn the inverter on this is activated as well. would this of made much difference?

I will watch that SOC now and see how we go.

Any other comments or tricks?

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Hi all, particularly Grahame and Russ.......

Very interesting information, thank you. About a month ago, I had the chaps at the factory check my HWS as it was difficult to start. Unfortunately , they left it in ignition mode and when I entered the van last week to get some keys, I noticed the battery gauge was flashing 'low'. Very strange, as nothing was turned on as far as I was aware and they were fully charged before I took it to the factory. When I checked the batteries with a multi meter, they were all at 11.7 volts. Later that evening when I returned to the van to replace the keys, I jus happened to notice the red light of the HWS igition being on. The HWS igition had been running for about 3 weeks, non stop. The van and batteries are 9 months old. Do you think the battery life has been significantly shortened by this. I have reported the problem to Tom at the factory.

I look forward to your responses.

Regards

Chris

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Hi Russ

How did you go about insulating the fridge cavity?

Bryan

Hi Bryan,

I measured the gap between the fridge and the cavity walls with the fridge in place. I did this from the hatch in the side of the van. Even the gap at the top can be measured by pushing the tape measure up until it hits the top of the cavity. Then measure the distance from there to the floor of the cavity. Then measure the height of the actual fridge and subtract fridge height from the first measurement. You can even measure the depth of the cavity from the rear.

I took my measurements to a company that makes foam insulating panels for air-condition systems and chillers and got them to cut the panels I need to the exact size. All up, with some of that aluminium tape to seal the joins, it came to about $250.00

Then I removed the fridge. No other way around this I'm afraid. It's not difficult though. You just unscrew the screws around the front frame of the fridge and then push the fridge from the rear (through the hatch) to get it started. Once it is out enough to get your fingers behind the front frame of the fridge you can pull it out easily enough. I placed an esky in front of the fridge that just happened to be the same height as from the floor of the van to the bottom of the fridge. This way I simply pulled the fridge out onto the esky.

Once the fridge was out I was able to insert the foam panels and make any cut-outs needed for cables etc. I glued the panels in place with liquid nails. I taped all of the joins with that aluminium tape for a complete seal. You should note that I also covered the top hatch of the cavity with the foam paneling. I figured that the main hatch at the bottom has plenty of air flow and would be enough ventilation. This has proven to be correct. I also cut and fitted 25 mm thick foam rubber insulation, with the aluminium backing, to the under side of the fridge body to prevent heat from the motor affecting the fridge.

Pushing the fridge back in was a real bugger. The foam was so accurately cut that you couldn't fit a cigarette paper between it and the fridge anywhere. It took me and another guy some serious effort to get her back in, but it was worth it.

I daresay that you could use pink bats or similar but I was concerned about fibres leaking into the van. I don't know about you but we used to get dust in through the fridge cavity so if dust could get in, so could insulation fibres. Now that I've insulated the fridge cavity and taped it up, we no longer get dust through it! Yippee!

Hope this helps,

Russ

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Do you think the battery life has been significantly shortened by this. I have reported the problem to Tom at the factory.

I look forward to your responses.

Regards

Chris

I'm sorry to say that this will have shortened the life of the batteries but it would be difficult to say how much. There are tests that can be done that can determine the remaining capacity of a fully charged battery. Most reputable suppliers of batteries would have one of these testers. Essentially they stress the battery by a given amount for a given time and monitor the drop in voltage Vs current supplied to compute the remaining capacity of the battery.

I think it would pay you to arrange for one of these tests to be done and take the van there.

Cheers

Russ

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Thanks Russ, I appreciate your advice.

Regards

Chris

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Russ, your explanation has been really useful. As Rick says, even I understood all that, and let me tell you, this is no mean feat! And grahame, your explanation of what to look for has been extremely informative. I for one am an obsessive watcher of the SOC, and haven't really understood what it was telling me.

In the mornings, even after heavy use of the TV the night before, it will often read 12.8 or 12.7 and I interpreted that to be low. Now I can see it is far from low. I don't think we have ever seen it go lower than 12.4. And that was after 8 days in rainy weather with heavy use of TV, washing machine and computer. (We have 4 x 130 watt panels and 4 batteries).

These solar panels are wonderful things. They are addictive; the more you have the more you want.

Chris

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Folks,

I am sorry to have disappeared from the battery charging / monitoring topic. I suffered a laptop death, so after a visit the Harvey Norman I am now going through the joys of re-building on our new machine. It was a disc failure with no warning, so one looses everything. Don't forget your backups people, luckily I had a backup two weeks old.

Rick and Lee,

No thanks, I will decline the invite to write for Caravanners Forum.

Pete and Tracy,

HWS start left on which gave a reading of 11.7V across the terminals. A MIN V reading for that day is what I would have looked for but that reading would indicate that some battery damage is likely. The MIN and MAX voltage readings on regulators are "integrated results" i.e. they are not instantaneous readings but a result arrived at by averaging readings across a number of control periods. Otherwise a heavy load being switched on or off, such as an inverter which can have a heavy inrush current will give a spike in voltage readings. Young batteries with minimal sulphation would be damaged less than older batteries with a higher degree of sulphation. I feel that one would be on thin ice mounting a compensation claim on one occurrence though.

240/12 Switch

I don't quite follow your question, but I offer the following comment. I have tried to get a Kedron wiring diagram for our unit from Ashley on a couple of occasions to no avail. In the absence of a diagram, my understanding of the operation of this switch is that when set to 240, 12V operations in the van are inactive other than loads which are hardwired to the batteries such as the fridge and an inverter if you have one.

Russ,

As you point out load testing is the way to test the health of batteries. The topic can run to a couple of chapters on its own. In general the design of a load testing regime should reflect the type of load the batteries are supplying. Under a load batteries have a characteristic drooping voltage characteristic - fellers very similar to the curve you see while having a pee in the bush.

Caravanners may have noticed battery capacities quoted against a C20 or C10 figure in literature. These figures refer to a current draw (Amps) calculated by dividing the capacity of the battery by the quoted figure. So for a 120AHr battery and a C20 current it works out to 120/20=6 Amps. The C10 rate of discharge for the same battery is of course 12 Amps. For batteries constructed to do service as house batteries or automotive starting batteries the C20 rate is considered safe for charge and discharge. The C10 figure is considered to be pushing it a little, but OK for short periods. C10 can lead to the battery generating heat.

Regards,

Grahame

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240/12 Switch

I don't quite follow your question, but I offer the following comment. I have tried to get a Kedron wiring diagram for our unit from Ashley on a couple of occasions to no avail. In the absence of a diagram, my understanding of the operation of this switch is that when set to 240, 12V operations in the van are inactive other than loads which are hardwired to the batteries such as the fridge and an inverter if you have one.

Regards,

Grahame

Hello Grahame,

I may be able to enlighten you re: 240/12V switch. When on 12V, all load is drawn from the batteries (sometimes via shunts), load terminal of the solar regulator and the charge lead from the car (if connected.) All as you would expect.

You're gonna love this next bit.....

When on 240V, there is a regulated 240 Volt power supply mounted in the boot that runs all the load that is NOT directed directly to the batteries. The fridge, inverter etc that are hard wired to the batteries remain unchanged. The 240VAC to 12VDC power supply in the boot runs in addition to the Battery Charger which obviously also runs when the van is connected to 240VAC. I can only suspect that way back in time someone may have been concerned that some of the appliances in the van might not handle the extra DC voltage of the battery charger when it is in Boost or Equalisation mode, so they fitted an extra 12 V supply to overcome this.

Well, that's my theory anyway. The only flaw in my argument is that if they were worried about the battery charger's boost voltage, why weren't they concerned about the same from the Solar regulator? The other theory I have is that the earlier battery chargers might have been a little underdone and not been able to charge the batteries as well as run the van Load. By putting in the extra 12 V supply the charger didn't have to run the van load. Seems a bit silly to me. Why not use the appropriate rated charger in the first place? The battery charger in my van is a 60A unit and is pretty darn good. Once it is on Float it tracks the current that is drawn by the appliances pretty well.

I removed the other PSU ages ago. In fact, I rewired the entire DC system as it was an absolute dog's breakfast. The PSU was just one more fan making noise in the front boot that I could hear right through the wall while in bed.

When I asked the guys at the factory why the 12 VDC supply is fitted, no-one had any idea. Must be a hangover from earlier times and whomsoever thought of it has now moved on.

Cheers

Russ

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When I asked the guys at the factory why the 12 VDC supply is fitted, no-one had any idea. Must be a hangover from earlier times and whomsoever thought of it has now moved on.

That's interesting Russ. When our van was built last December I asked for the PSU to be omitted as I could not see the point because we had upgraded charge capacity as a result of the charger/inverter we had chosen to have fitted.

I was told that the PSU should be fitted "just in case" the charger/inverter failed I would at least be able to run the lights and 12v outlets from the mains.

I think the changes to the wiring to remove the PSU were all too hard to contemplate.

John

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Russ,

When I asked about the 240/12V transformer(as they call it) it was explained to me that it is there in case the batteries fail you will still have 12v to power the van when on mains/generator power.

Without a wiring diagram it makes it hard to see the need but I assume that the output from the voltage charger is somehow isloated from the 12v input to the van.

Nev

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Thanks John and Nev. Crikey, the reasons the factory gave you for having the other 12 Volt supply are even more lame than the ideas I came up with. I can understand them thinking about some level of built-in redundancy but I don't get it!

If the battery charger fails, so what? Unless I'm wrong, most Kedron vans have some form of Solar setup and that, in its own right, should be able to keep you chugging along. Granted, you may have to ration power a bit, but I hardly think that the expense of the additional 12 Volt supply is warranted.

And the other reason given....a battery failing. In this situation you would be in a fair bit of trouble anyway as the fridge is wired directly to the batteries. I would be most surprised if all of the batteries failed at once. In the event of a battery failing it is a very simple process to disconnect all of the batteries, identify the culprit and reconnect those that are left.

But this does pose an interesting question. How many of us Koggers have had either of the scenarios mentioned and had to rely on the additional 12 Volt supply?

In my case, we spend more time out of van parks than in them, so the whole thing is a moot argument anyway.

Back in January 2009 we took our van back to the factory for a few issues to be sorted out after our "shakedown" trip. We ended up living in our van at the factory for three days. While there I took the opportunity to talk to several of the staff, including the young fellow who was wiring the vans. He was a nice young chap but had no trade qualifications and had learnt his wiring skills from a former employee whom had subsequently moved on.

During my questioning it became clear that this young bloke had no idea how the equipment functioned, nor how to identify issues. He wired the vans the way they "had always done". I was so concerned about this that I actually drew up a schematic diagram of how the DC wiring should be done, including leaving the additional 12 Volt supply out of the finished job. I gave this to Ashley and explained to him why things should be done that way. I think he was a bit nonplussed.

Anyway, to cut a long story short, my solar regulator was not wired correctly and would not show the load current (because the Load terminal of the regulator was not in use.) The young chap had a go at getting it right but in the end I told him not to go any further with it as I would rewire it myself. This I have done. Why I am mentioning this is that I noted Grahame's comment in an earlier post

I have tried to get a Kedron wiring diagram for our unit from Ashley on a couple of occasions to no avail.

I think that Grahame couldn't get a drawing because there wasn't one, but there is now although I have no way of knowing whether the people at Kedron use my drawing or any part of it. As I have said before on this forum, I have rewired three Kedrons now and I'm sure there will be more in the future. The DC wiring is possibly the weakest point in what is an exceptional van.

Cheers

Russ

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Hi Bryan,

I left the only one I had drawn with Ashley, but I can reproduce it easily enough. Just give me a couple of days and I'll PM you when it's ready. Then I'll email it to you.

Cheers

Russ

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Hi Russ and Grahame,

Been following this discussion closely and am pleased to report that the pea-soup has now become a fog! I would be very grateful to you Russ if and when you have redrawn your concept of the wiring diagram a copy could be sent to me as well.

We're on our 2nd Kedron and the wiring is completely different to the first in that the first had a Plasmatronic Solar Controller which had a user accessible function output, this one doesn't so I have little idea what my solar panels are doing and I'm thoroughly confused by the additional 12V supply.

Cheers

Brian

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Hi Russ,

Would you include me in on the wiring diagram please.

E-mail is good.

Safe travels

Gary

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Hi Russ

Any chance you could put the diagram on this site ? I'm sure your going to have more requests.

I also would like to see it.

Cheers Phil

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Russ,

You really have a "hot product" in this wiring diagram. Could I have a copy too please.

Grahame

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Russ

I have asked Kedron for a circuit diagram also but as yet have received nothing so if possible would also like to receive a copy of yours.

Lance

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Ok everyone, here is the diagram and explanation.

Caravn_Wiring_Guide.jpg

Notes

1) No fuses or breakers are shown for simplicity. All cables must be protected by fuses or breakers

2) You can see that the Solar Regulator uses the Negative connections to operate

3) The Positive common, shown here at the Solar regulator for simplicity, can be at any of the positive connections and after I drew this I realised that the Inverter Positive connection should go directly to the battery.

4) While only one wire each for Pos and Neg is shown going to the Solar Panels, it is preferable to wire each panel separately

5) This diagram is for PL20 and PL60 Plasmatronics regulators. For PL40 units, the dotted wiring should be installed and the hard connection between the fuse panel and the Solar Regulator removed.

6) This diagram will suit any quality regulator that has separate Load, Battery and Solar Panel connections. Again, if the Load connection has a low output rating, wire as per PL40 connection.

7) Red wires are Positive connections, Black are Negative and Blue represents the sensing wires from the Shunt to its interface module (not shown). There will also be wiring from the interface modules to the PL20/40/60 unit

8) Whilst only one battery is shown, it is representative of however many batteries you have installed.

9) Accessory wiring such as Anderson Plugs for pumps, car fridges etc should be wired to the Shunt that the van fridge and inverter are connected to.

10) The 240 Volt AC to 12 Volt DC power supply fitted by Kedron is not included in this circuit and is not required to support the 12 VDC system.

11) The block labelled + LINK is a connector strip but could be another fuse panel whereby the positive connections of the appliances are also fuse protected. (My preferred option)

12) The chassis, frame and body cladding of the van should NEVER be used as a common or "return" rail.

13) If any of the Negative connections in your van are connected to the chassis, frame or cladding and this cannot be isolated, make the + LINK box a fuse strip and the Negative connections commoned to a link strip. In other words, reverse the role of these two items. As I stated, the preferred option is to fuse Positive and Negative connections.

14) I have not seen a recently manufactured van, but it seems that Kedron no longer use Plasmatronics regulators. It is quite likely that they have changed over to MPPT Regulators (Maximum Power Point Tracking) but even so the principles should be the same.

Explanation

High-end Solar regulators can accurately show the State of Charge (SOC) of your system batteries by monitoring the Voltage of the batteries and the flow of current into and out of your batteries. State of Charge allows you to tailor your energy usage so that you maximise the life of your batteries. It is generally accepted that for all Lead-acid and lead-calcium batteries, the deeper the battery is discharged, the shorter will be its life expectancy.

In order to accurately calculate the SOC, the Solar regulator already knows how much current it is supplying from the Solar Panels. Likewise, it knows how much current is going out through the "Load" terminal. What it doesn't know is how much current your car is supplying as you drive along, or how much current your Battery Charger is putting into your batteries. It also does not know how much current is being drawn by the van fridge or an inverter if you have one fitted.

To monitor the current flows for items not directly connected to it, the Solar Regulator can use Shunts. A shunt looks like a giant fuse. It is connected with the battery to one end and the devices using or supplying current to the other end. The piece in the middle of these connections is a conductor with a very precise resistance. When current flows through the Shunt it goes through the precise resistor and causes the voltage to drop slightly. This means the voltage measured at one end of the Shunt will be slightly different to the voltage measured at the other end. It is this small, but measurable volt-drop that allows the Solar Regulator to work out how much current is flowing through the Shunt.

All Shunts have a calibration value. An interface unit is connected to the Shunt and measures the small volt-drop. This interface unit is set up to match the calibration value of the Shunt and in so doing ensures that the Volt-drop it is measuring is converted to a signal that is fed into the Solar Regulator, telling the Regulator EXACTLY how much current is flowing through the Shunt. When setting up a Shunt, it is important to "zero" the interface unit while no current is flowing through the Shunt.

So, by connecting the fridge, inverter, accessory power connections through a Shunt, the Regulator now knows how much current is being drawn from the battery. What about the charge lead from the car? Shunts are bi-directional. This means that if the Shunt sensing wires are connected the correct way around the interface unit can tell whether the current is flowing from the car to the van when driving, or from the van to the car if the car engine is off. I use this ability all the time. I isolate the cranking battery of the car from the Auxiliary battery. The Aux battery is connected through to the Van via the charge lead. The car fridge is in the rear of the car and is connected to the wiring going from the car to the van. This way, the car fridge is being run by both the car and van batteries. The Aux battery in the car is quite small, so the van batteries do the lion's share of the work. In this case, current is flowing out of the van batteries to the car.

In the scenario (above) the Shunt will record a Positive value for current going into my van batteries and a negative value if current is going the other way. The Solar Regulator uses the value relayed to it to display a figure as either "IN" or "OUT" when viewed on the display panel, with "IN" representing current going into the batteries and "OUT" representing current going out of the batteries.

If the Battery charger is supplying current, then the Shunt, via the interface unit, will send a value to the Solar regulator that represents the "IN" current. You might be thinking "If the charge lead is connected and the car is not running, then the battery charger could be sending current through to the car as well as the van batteries." This is true, but I'm less concerned about the Aux battery in the car getting overcharged than I am about the state of my van batteries. In this case, any current going to the car from the charger is not seen by the Shunt anyway, thus not affecting the accuracy of what is going into the van batteries.

There is another possibility though. In the above scenario, the Battery Charger might be supplying some current to the car and some to the van Batteries, but at the same time, the van batteries could also be supplying current to the car battery. This is not a problem because the Shunt will measure the net flow of current and report it to the Solar Regulator. The end result will be accurate.

The other shunt in the circuit diagram is there purely to measure the "OUT" currents drawn by the fridge, inverter, accessory appliances and, in the case of a PL40 unit, all of the other 12 Volt stuff in the van. The two Shunts are connected to the same place in the Solar Regulator and the sum of the currents (IN and OUT) is calculated and then displayed.

For example, The appliances connected to the Load terminal might be drawing 10 Amps. The Fridge might be drawing 5 Amps. The battery charger might be delivering 10 Amps. The charger current is 10 Amps but is opposite in direction and will be calculated to show a net 5 Amp charge or "IN" current and the "OUT" current will be the 10 Amps going to the items connected to the Load terminal. This represents a NET loss of 5 Amps.

In a real-world scenario this is unlikely to happen. If the van batteries weren't at their peak at the end of the day, the 240 Volt Battery Charger would most likely be producing the 15 Amps of load current plus extra to charge the battery. In this case you might see a display like 10 Amps "OUT" and say, 20 Amps "IN" which would represent the 10 Amps going out of the Load terminal and 25 Amps coming from the Battery Charger - 5 Amps going to the fridge and 20 Amps going into the batteries. The net difference would be 10 Amps of charge actually occurring. It is the net difference that the Solar Regulator uses to calculate the SOC.

When on 240 Volt AC for a fair while (such as when staying at a caravan park), the batteries will eventually get to a stage called "Float". This means that the Net current flow is Zero. You may well have 25 Amps going to appliances, but the Charger will match this almost exactly. During the day, the Solar Regulator will be capable of getting a charge current from the Solar Panels but if the batteries are already on "Float" then the Regulator will throttle this current down to nothing.

Right! What is all of this leading to? Well in nearly every Kedron van I have looked at, the current from the car charge lead and the Battery Charger does NOT go through a Shunt and is not calculated by the Solar Regulator. Many of the vans did have a shunt for the fridge (and other devices in the case of the PL40 unit) but I have seen these wired back-to-front (so that the discharge current is interpreted as charge current) or Kedron have connected the fridge on one end of the Shunt and other appliances on the other end, so that one or the other isn't actually being read. This renders the State of Charge calculations useless.

We know that State of Charge is important, so it should be accurate. Get your wiring right and then aim to have your battery SOC at 70% - 75% after discharging overnight (read at the time that the Solar Regulator is JUST starting to charge as the Sun gets higher in the sky.) You will soon learn which appliances are current "hogs" and how long you can run them for while still staying within limits. You should get around 7000 charge/discharge cycles out of AGM batteries if you stick to the percentages quoted. This number of charge/discharge cycles can drop dramatically by discharging your batteries to, say, 50% SOC regularly.

OK, that will do for starters. Next time I'll post a dissertation about how important wire sizes are in low voltage systems and how Kedron's wire size selections are too small for efficient operation of your system. Right now I'm tired and need to go to bed.

Russ.

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