Electrickery for camping

[Elders]

The series of posts will deal with the following topics:
Electrickery for camping
How to power your fridge ?
Battery type
Where to place the battery?
What size cables?
How to charge the second battery
What to power from the 2nd battery ?
Solar systems
Dual battery system


NOTE - series of posts attached as a single pdf (to post ONE)


Electrickery for camping

Chances are if you have been camping for some time that you have seen friends go through the following evolution, who knows, you might have gone through this yourself. And many of us are somewhere on this journey ….

You go camping with friends, possibly even get to use their hand me down tent for the Saturday night. Next week you are ALIVE, and buzzing from the experience of “the camp” …. And now you plan your next trip. At some point you obtain your friends hand me down tent, or go buy a cheapy at your nearest camping shop. While you walk through the store you realise you need a sleeping bag. Thanks to Eskom we all have gas bottle at home so you are set for making coffee in camp.



First camp on your own is sort of okay. But you convince yourself that if only you had the gear the guys next to you had, then you would have enjoyed your camp so much more. Just look at his drawer system in his bakkie, and that other guy had such good looking rig on some sort of trailer setup ….

And the journey starts. Now you troll the camping shops. Visit every Forum to get the best overlanding tips, for your next 3 day camp 50km from home. THREE days ! Wow, now you are going to need some sort of a cooler box to keep the meat from going off. What !! These 4x4 camping stores are totally wacked out. How dare they charge more than R 3 000 for a cooler box, sure that R 250 model will do the trick.




By the morning of day 2 the cooler box is no cooler than the outside air. Day two will always be remembered for the luke warm drinks ….. Then you see the guy camping next to you has fridge ! A fridge in the middle of the bush with no electricity nearby. Huh ??



And thus you enter a brand new world of electrical options for your camping needs.

So you buy that 12V fridge/freezer, and then find out that it needs power when you have parked your vehicle. JIP, the salesperson “forgot” to tell you about a “dual battery setup” …. You guessed it, you have only just started spending money. You are about to spend a lot more money on electrickery for your camping setup.

[Elders]

How to power your fridge ?

EDIT - also see post 447 on page 23, document attached to this page

The answer to this depends largely on YOUR use and requirements. There is no single answer that works for everybody. Some need the drinks to stay cool, and don’t worry too much if the fridge is off for some hours per day. Others keep medicine in the fridge and the power must be un-interrupted. The following is some examples of how it can be done.

Some people place the fridge in the back of the vehicle and use an existing power point. Most of these power points only deliver power while the ignition is switched on. The wiring to these power points is seldom rated for long periods of use for the power demand of the fridge. The next evolution is to install a relay and a dedicated power point for the fridge. The only benefit here is that you now know the wire is rated for the current draw. You can also use better quality electrical connection points.





But this is only the start of the electrickery journey ! Having already spent a small fortune you now WANT that fridge to be cold for the whole weekend, not only while you drive. So you start playing camping-russian-roulette, you leave the ignition on for a few hours at a time to keep the fridge going. And it is not long before you wake up to a flat battery !

Now you start asking questions about a “second battery”. Never in your life have you had so many opposing ideas about a single item. You are going to encounter the following questions:
- What type of battery?
- Where must the battery be placed?
- What size cables?
- How do you charge this second battery

Most often people forget to ask how to use the power from the second battery. This typically becomes more apparent when the next question pops up: What can I power from the 2ndbattery ?

And then a few trips later you start asking questions about solar systems.

In the following sections I will attempt to provide some insight into possible answers to these questions.

PLEASE NOTE:
- I will mention the brands I have installed, but I will also mention some other brands as well. This series of posts is NOT promoting any brand above any other ! Rather I will attempt to promote technological concepts, while trying my best to explain the use of each technology in respect to the end user requirements, and to explain it in laymans terms.
- I have multiple qualifications in electrical and mechanical engineering. But most of what I am posting here is as a result of having paid expensive school fees along the road ofelectrickery for our camping.
- During the last decade there have been huge advances in the various components. And by 2015 this article will need updating in terms of the latest technologies for each field … and this need for updating will be never ending. So PLEASE read all comments in context of the time it was written and the technology available at the time, AND in terms of the unique needs of each end user.
- Eggie, Fluffy, Koebelwagen, Mistral, SarelF and so many more had contributed greatly to this knowledge pool over the last couple of years – THANKS gents !

[Elders]

Battery type


For years our only option was “high cycle” batteries, the type that have been used as starter batteries for decades. Then “deep cycle” batteries were added to the option list. There are now other very expensive options as well. (With no personal experience of these alternate models I will ask others to add information about these options)

I was going to write a nice piece about the properties of the high vs deep cycle batteries …. But the more I researched this topic the bigger the mine field got !

For now I will just be highlighting the following very basic characteristics:
- Charge voltage –modern alternators deliver around 14V, which is high enough to charge a high cycle battery, while a deep cycle requires about 14,5V for a full charge.
- The norm now is a battery with an approximately capacity of 100A.h.
- Deep cycle batteries are better suited for deep discharge, when compared to high cycle batteries. Which is probably the main reason these have the market share.
- Deep cycle batteries have a unique characteristic whereby it charges slowly once discharged below 50%. This is probably the single biggest drawback of deep cycle batteries. Once a deep cycle battery has been discharged deeply in a camp environment you will need an extended charge cycle to be able to get it charged properly. More about this when we look at the charging options.

However, this magic “Capacity” of a battery is hardly the same as a 2 liter milk bottle that will always have a capacity of 2 liter when full. According to the table below a classic six cell car battery is “full” when it has a voltage of 12,7V. By the time the voltage drops to 12,42V the battery is only 80% full, and 11,9V points to a charge level of 40%.

State of charge pic -



A “total discharge” is very bad for a battery and drastically shortens its life span. Thus the National Luna fridges have a function whereby the fridge will automatically switch off at a set value to protect the battery. The safest setting will shut off the fridge once the battery voltage drops to 11,5V. You can push this limit by opting for the medium safety setting of 10,5V – which according to the attached table is a total discharge of the battery, which will shorten the life span of the battery !

Battery monitors
Imagine driving your 4x4 with no fuel gauge, not knowing when you will run out of fuel.

Now imagine camping with a fridge full of drinks and meat, not knowing when your battery is going to “die”. A “battery monitor” is the fuel gauge for your battery. From the previous table you can see that there is a direct correlation between the battery voltage and the battery charge level. Thus a battery monitor is just a fancy voltmeter.

The NL fridges have battery monitors installed in their fridges for this very reason.



NL also sells battery monitors. These can be used to monitor the 2nd battery voltage, or you can buy a dual unit to show the voltages of both batteries. Do note that these units have a most annoying audible alarm, which cant be muted, when the battery level drops low.

For the real techno geeks there are very fancy meters that will measure the voltages, and record the current flow into and out of the battery.



Enough of batteries for now. I will leave it to the experts to tell us more about the current options.

[Elders]

Where to place the battery?


The possible answers to this question are dictated by your vehicle and camping setup.

The classic setup was to fit the 2nd battery in the engine bay. Some 4x4 vehicles are manufactured with this in mind and have space set aside for a 2nd battery. Yet more and more vehicles don’t have any spare space in the engine bay. With bakkies we often see the 2nd battery in the back with the rest of the camping gear. This works, as the back is traditionally well ventilated.

Here I need to point out that traditional batteries give of highly combustible Hydrogen gas when it is charged. As such it is a VERY bad idea to charge a battery in a closed space ! Some of the modern batteries claim to use other chemicals and that no hydrogen is given off during charging.

If you drive a 4x4 SUV type vehicle and need to install the battery IN the vehicle please ensure you get a battery that is totally sealed, that wont be giving off any hydrogen gas during the charge cycle.

And of course many batteries are fitted in camping trailers.

Wherever you place the battery, please ensure you use a proper bracket to mount it. With batteries weighing about 30kg it becomes a very heavy projectile in an accident, so it really needs to be fixed properly. There have been a number of reports where poorly designed battery brackets tore vehicle fenders !!



My personal recommendation is to place the battery close to where the power will be used.

[OLi4 Chris]

Where to place the battery?


The possible answers to this question are dictated by your vehicle and camping setup.

The classic setup was to fit the 2nd battery in the engine bay. Some 4x4 vehicles are manufactured with this in mind and have space set aside for a 2nd battery. Yet more and more vehicles don’t have any spare space in the engine bay. With bakkies we often see the 2nd battery in the back with the rest of the camping gear. This works, as the back is traditionally well ventilated.

Here I need to point out that traditional batteries give of highly combustible Hydrogen gas when it is charged. As such it is a VERY bad idea to charge a battery in a closed space ! Some of the modern batteries claim to use other chemicals and that no hydrogen is given off during charging.

If you drive a 4x4 SUV type vehicle and need to install the battery IN the vehicle please ensure you get a battery that is totally sealed, that wont be giving off any hydrogen gas during the charge cycle.

And of course many batteries are fitted in camping trailers.

Wherever you place the battery, please ensure you use a proper bracket to mount it. With batteries weighing about 30kg it becomes a very heavy projectile in an accident, so it really needs to be fixed properly. There have been a number of reports where poorly designed battery brackets tore vehicle fenders !!



My personal recommendation is to place the battery close to where the power will be used.

I totally agree with that a flying battery can write your caravan off & cause serous injuries to persons in an Accedent
Nice post

[Elders]

What size cables?


Uhmja …. Bet the first installer you see will tell you that you MUST use 16mm square cable to the 2ndbattery, or even 25mm square cable if he thinks he can milk you for more money …. Thick cables are expensive, and there is a lot of money to be made if you can convince a client to use the thickest possible cable.


4, 6, 10 and 16mm square cables :


The reasons for using very thick cables is to limit the “volt drop”, while the current carrying capacity will in turn determine the minimum cable size.

On the assumption that most people reading this are not qualified electrical engineers it is best to take a moment to discuss these terms. To keep it simple, let’s consider the flow of electricity as that process whereby electrons move from one atom to another. For this process to occur you need a “potential difference”, and a closed circuit. Once you have a chemical cell which provides a potential difference, you have a situation whereby you can complete the circuit using wires and a “load” (that item that uses the electricity). The “resistance” of the load will then determine the resultant “current flow”. The basic terms are:
- Potential difference - volt (unit V, symbol V) - http://en.wikipedia.org/wiki/Volt
- Current flow – ampere or amps (unit A, symbol I) -http://en.wikipedia.org/wiki/Ampere
- Resistance – ohm (unit ohm, symbol R) - http://en.wikipedia.org/wiki/Ohm

The basic mathematical relation of these three entities is : V = I x R

In addition to this there are two more entities relevant to electrickery in our 4x4’s:
- Charge - here we use the term “A.h”, which is literally the product of the current flow and the time it was used.
- Power – watts (unit W, symbol P) - http://en.wikipedia.org/wiki/Watt


So what does all this stuff actually mean ?

Well your 2nd battery is charged from the vehicles alternator, when the alternator has a larger “potential difference” than the voltage of the 2nd battery. So if your 2nd battery shows a voltage of 12V and the alternator puts out 14V the 2nd battery should be charged. BUT, we need to look at the “circuit”. This means we need to look at every connection and every piece of wire in the circuit. Working with round numbers here – let’s say the circuit (wires and connectors) add 0,05 ohm resistance to the complete circuit while the 2nd battery is being charged at a rate of 20A. Then we can calculate the voltage drop in the circuit as follows:
V = I x R = 20 x 0,05 = 1V
{Note to the purists – this example use values aimed at getting the message across}

This means that of the 14V available from the alternator, the 2nd battery only “sees” 13V, since 1V was “lost” in the circuit due to the resistance in the circuit.

Punch line : 13V is NOT enough to charge the 2nd battery ! Well not entirely true .... in practice it means the charge current is limited, and a balance is struck between the volt drop and the charge current. As such a 10mm square cable may well be used to charge the second battery, albeit at a reduced current flow due to the volt drop.

And thus people started using THICK cables with lower resistance to ensure the 2nd battery “sees” a voltage as close to the alternator output as possible. For decades this practice was our only option, and the use of way over sized cables became the norm.

And then the deep cycle batteries entered our campsites. But a deep cycle battery needs 14,5V to fully charge !! Thus MORE volts than many modern alternators deliver. In the next section we will discuss how this problem was overcome. For now let’s focus on the minimum cable size.

We already know that V = I x R, in thinner cables the resistance is higher, leading to higher voltage drops. This voltage drop causes heating of the cable. There are industry norms for the maximum current relative to cable size to ensure the heat generated remains within safe limits. From the SABS tables (using the worst case values) we get the following guidelines for the maximum current that a cable can carry continuously.




Thus, if you used a charger that limited the charge current to 20A a 4mm square wire would be sufficient. More about this in the next section.

[Alberto]

What size cables?


Uhmja Â…. Bet the first installer you see will tell you that you MUST use 16mm square cable to the 2ndbattery, or even 25mm square cable if he thinks he can milk you for more money Â…. Thick cables are expensive, and there is a lot of money to be made if you can convince a client to use the thickest possible cable.


4, 6, 10 and 16mm square cables :


The reasons for using very thick cables is to limit the “volt drop”, while the current carrying capacity will in turn determine the minimum cable size.

On the assumption that most people reading this are not qualified electrical engineers it is best to take a moment to discuss these terms. To keep it simple, let’s consider the flow of electricity as that process whereby electrons move from one atom to another. For this process to occur you need a “potential difference”, and a closed circuit. Once you have a chemical cell which provides a potential difference, you have a situation whereby you can complete the circuit using wires and a “load” (that item that uses the electricity). The “resistance” of the load will then determine the resultant “current flow”. The basic terms are:
- Potential difference - volt (unit V, symbol V) - http://en.wikipedia.org/wiki/Volt
- Current flow – ampere or amps (unit A, symbol I) -http://en.wikipedia.org/wiki/Ampere
- Resistance – ohm (unit ohm, symbol R) - http://en.wikipedia.org/wiki/Ohm

The basic mathematical relation of these three entities is : V = I x R

In addition to this there are two more entities relevant to electrickery in our 4x4Â’s:
- Charge - here we use the term “A.h”, which is literally the product of the current flow and the time it was used.
- Power – watts (unit W, symbol P) - http://en.wikipedia.org/wiki/Watt


So what does all this stuff actually mean ?

Well your 2nd battery is charged from the vehicles alternator, when the alternator has a larger “potential difference” than the voltage of the 2nd battery. So if your 2nd battery shows a voltage of 12V and the alternator puts out 14V the 2nd battery should be charged. BUT, we need to look at the “circuit”. This means we need to look at every connection and every piece of wire in the circuit. Working with round numbers here – let’s say the circuit (wires and connectors) add 0,05 ohm resistance to the complete circuit while the 2nd battery is being charged at a rate of 20A. Then we can calculate the voltage drop in the circuit as follows:
V = I x R = 20 x 0,05 = 1V
{Note to the purists – this example use values aimed at getting the message across}

This means that of the 14V available from the alternator, the 2nd battery only “sees” 13V, since 1V was “lost” in the circuit due to the resistance in the circuit.

Punch line : 13V is NOT enough to charge the 2nd battery ! Well not entirely true .... in practice it means the charge current is limited, and a balance is struck between the volt drop and the charge current. As such a 10mm square cable may well be used to charge the second battery, albeit at a reduced current flow due to the volt drop.

And thus people started using THICK cables with lower resistance to ensure the 2nd battery “sees” a voltage as close to the alternator output as possible. For decades this practice was our only option, and the use of way over sized cables became the norm.

And then the deep cycle batteries entered our campsites. But a deep cycle battery needs 14,5V to fully charge !! Thus MORE volts than many modern alternators deliver. In the next section we will discuss how this problem was overcome. For now letÂ’s focus on the minimum cable size.

We already know that V = I x R, in thinner cables the resistance is higher, leading to higher voltage drops. This voltage drop causes heating of the cable. There are industry norms for the maximum current relative to cable size to ensure the heat generated remains within safe limits. From the SABS tables (using the worst case values) we get the following guidelines for the maximum current that a cable can carry continuously.




Thus, if you used a charger that limited the charge current to 20A a 4mm square wire would be sufficient. More about this in the next section.

i have to explain to someone this wire thickness at work for a project we want to use a small winch bought at adendorfs , the power will come from a tractor ,it will not be used to winch 4x4 or the tractors ,,which is the dia meter of these wires inner and outer core on the foto , plus the amps it carries, we are going to use anderson plugs to connect the tracktors and to the project ,but need to know the wire sizes ,is the awg [,american wire gauge] the same as south african sizes ,

[DirtBasher]

i have to explain to someone this wire thickness at work for a project we want to use a small winch bought at adendorfs , the power will come from a tractor ,it will not be used to winch 4x4 or the tractors ,,which is the dia meter of these wires inner and outer core on the foto , plus the amps it carries, we are going to use anderson plugs to connect the tracktors and to the project ,but need to know the wire sizes ,is the awg [,american wire gauge] the same as south african sizes ,

Here are the three cables sizes from AWG to metric

[Alberto]

Here are the three cables sizes from AWG to metric

thanks so i said skoenmaker hou jou by jou lees end get a sparky

[Elders]

How to charge the second battery


Once again there are so many options, and the optimum solution depends on your specific requirements.

Most people start off with connecting the 2nd battery to the alternator and hoping this will charge the 2nd battery. Depending on the exact setup you may be able to charge the battery to some extent, but highly unlikely you will get more than 80% of the possible capacity of the system. Remember the previous section where we spoke about the voltage drop, and the final voltage available at the 2nd battery.

The cheap solution is to pre-charge the battery at home, with a 220V charger. Then relying on the alternator to keep the system going for a typical long weekend trip. And this works surprisingly well for many people. But once you take a trip of more than a few days the limitations of this approach becomes very apparent. Then you start thinking of better systems …

The deep cycle battery is best suited for campsite use, but requires a charge voltage of 14,5V. This is more than most alternators now deliver. This created a market place for the DC-to-DC (dc2dc) chargers. The principle of this charger is simple, it takes the voltage from the alternator and pushes the volt value up, by reducing the current value in turn. You now get a situation where your alternator puts out 13V at idling, but after the dc2dc charger your 2nd battery sees 14,5V. An added benefit is that most dc2dc chargers actually limit the charge current, thus you can now more accurately choose a cable size that matches your installation.

Most dc2dc chargers are also “clever chargers”. The “clever chargers” monitors the charge level of the 2nd battery. Once the 2nd battery is almost fully charged the charge current is reduced, to protect the battery.

So while you are driving, your alternator, via the dc2dc charger, charges your 2ndbattery at 20A (different models have different pre-set values, but this is a realistic figure).This is a very good system and has many benefits, but still does not address the fundamental question of power while you are parked.

As long as you are parked your fridge draws power from the battery. With an average current draw of about 60A.h per day you need to drive at least 3 hours per day to keep the battery charged, or find some other way to keep it charged … More about this later.


Fridge power draw
National Luna (NL) provides a current draw figure of “an average of 2,5A” per day for its 52 liter Weekender Twin unit. Basic maths says 24 hours times 2,5A = 60A.h - http://www.nationalluna.com/weekender52.htm

BUT, NL briefly mentions “..consumption is measured in a controlled environment ... Actual power consumption may vary ...”. Actual tests show a current draw of 5 to 6 A. Due to the on/off cycles the average of 2,5A is possible in moderate climates. During summer in Kgalagadi or Namibia, with day temperatures of more than 40 degrees Celcius, and night temperatures mostly above 30 degrees Celcius the fridge hardly ever switch off !! At 5A for approximately 20 hours you suddenly need 100A.h to power your fridge !!

The actual power draw of your fridge will depend on many factors:
- Insulation – the quality of the insulation has a big impact on the power draw.
- Where the unit is installed – A unit installed inside an air conditioned SUV will draw a LOT less power than a unit stuck in the back of a super hot canopy.
- Use – Opening the fridge too often increased the cooling load, and thus increase the power draw.
- Loading of goods – Try to load cold goods into the fridge, or load the goods when you can use mains power to cool it down, thus saving your battery capacity.
- Operating temperature – The colder the thermostat setting of a fridge, the higher the rate of heat flow through the insulation.

Never over look the most obvious though – use the 220V in the camp site when available.


What is a “relay” ?
When switching a circuit on or off, a spark is generated at the switch. This spark actually burns away the switch contacts over a period of time (number of uses). The solution to this problem is to limit the current that flow through the switch – but the current flowing to the load is a constant. As such the circuit is now split in two:



Think of this as the electrical circuit for a set of spot lights. By switching the spot light switch, you are passing a small current through an electromagnetic coil, this closes the heavy duty switch between “30” and “87” and power is now sent to the spot lights. The numbers used in the illustration are above are the standard numbers found on relays.

Typical use of an inline fuse and a relay to power a load:


The current flow will determine the type of relay to be used. For spot lights and other small items standard relays are used. For connecting two batteries a much higher current flow is allowed for and a heavy duty colehersee type relay is used.





The benefit of a relay is that it will function automatically and no additional user input is required. That said, there are still a few users that want full manual control. They would then use a typical “marine switch” to connect or disconnect batteries.



The use of relays are VERY handy for spot lights, hooters, vhf radios, etc, and combining this with a nice waterproof box creates endless opportunities:

[Elders]

What to power from the 2nd battery ?


What do we use cell phones for now ? “Phoning” is last on a very long list of functions.

In the same way we start with a 2nd battery system to power the fridge. But once we have power we realize that it could:
- Charge the cell phones
- Charge the iPads
- Charge the laptops
- Charge the camera batteries
- Drive the compressor
- Power an electric blanket for winter camping
- LED lights
- And the list just keeps on getting longer and longer …

To manage this host of devices you will need a well planned power distribution setup. Jip, you have now migrated from simply powering your fridge to becoming your own Escom !

PLEASE NOTE:
The 12V battery and all the cabling you are about to install DOES have the potential to burn your vehicle to the ground if done badly !

MOST manufacturers void your warrantee once you have these electrical installations done !!

DON’T play with this if you don’t know what you are doing. This article is aimed at helping you to understand what a decent system should have in it.

This is not a DIY training kit !

When doing a power distribution system the safety of this system is determined by:
- Size and placement of fuses
- Wire sizing
- How wires are run
- Connections

FUSES
Install a 100A fuse close to the 2nd battery in the main positive wire going to the distribution box. In the distribution box plan your layout and provide appropriate size fuses for each circuit, ie a 5A fuse for the LED light circuit that will only be using about 1A, or a 15A fuse for the circuit that will power the fridge.





WIRE SIZING
With each circuit properly planned, you will know the expected current draw for that circuit and can use the optimum wire size. The only downfall of oversizing is the impact on your budget, but undersizing cables are to be avoided !



RUNNING THE WIRES
The fuses provide a measure of safety in the event of a short. But prevention is better than cure. Run the cables in sleeves or trunking to protect it, and to avoid electrical short circuits. The use of cable ties greatly assist with keeping wiring neat and preventing it from chaffing through, potentially causing short circuits.

CONNECTIONS
We go through all the effort of using correctly sized cables to keep voltage drops to an absolute minimum. Yet, one bad connection can cause more of a voltage drop that all the wires. And such a bad connection has the potential to generate heat and be the cause of an electrical fire!

Electrical connections very often make use of “lugs”. Proper connection of the wire to the lug can be done in the following ways:
- Solder – Insert the wire into the lug and solder it. However, a bad solder joint can cause a “dry-joint” which leads to a volt drop, which causes heat build up, which can melt the solder and the joint can become undone ! This is probably the lead cause of failure of joints.
- Crimping – using a proper crimping tool you can ensure a proper connection of the wire to the lug. The photos below shows two decent crimping tools. Do NOT try to use a pair of pliers to crimp a lug !
- Crimp and solder – I prefer to use a proper crimping tool, and then to also solder the joint. Definitely a belts and braces approach.
- Once the connection has been made, use some “heat shrink” to achieve a proper finish. A 4x4 fitment centre that use “insulation tape” wont ever touch my vehicle.


For the larger cables -


for the smaller cables -

LUG SIZING
Lugs have two dimensions:
- The whole diameter – the diameter of the bolt or screw that will hold the lug in place.
- The wire size – this dimension refers to the wire size that is to be used with that specific lug.

Thus a 6x4 lug will be connected to a battery terminal with a 6mm bolt, and will accommodate a 4mm square wire. Using the correct size lug is important to achieve an optimum connection.

[Elders]

Solar systems


You have now almost come full circle. You bought the fridge for your next 3 day camp. You now know the basics of where your 2nd battery can be mounted. You even know the basics of the wiring and fuses to distribute your new found power for other devices ….

And suddenly you find that the fancy dc2dc charger no longer can store enough power in that stupidly small 100A.h battery to drive the fridge, cell phones, laptops, camera batteries, etc etc … And driving for hours on end each day to keep all these devices charged is taking the fun out of your three day break away.

Time for the next step on this electrical journey – a solar system. After all this will keep that battery going and everybody can sit around the camp fire with their faces pointed directly at their individual electronic gadgets. So what are your options with solar:
- Foldable – You get a kit that folds up and packs away to about the size of a brief case. Nice. Minimal packing space. And when you need it you place it out on the grass and charge your battery. Downsides being that it only works when you have actually packed it out, ie it does not help you when parked out near a watering hole taking some photos, and when you get back to camp late in the afternoon there is not enough sunlight left to really charge the battery. And if you place it on the ground the neighbours kids ride over your panel with their bicycles. And at about R7 000 for such a fold up panel you want to wring their little necks for breaking your panel !





- Roll up panel – very much the same concept as above. Just cheaper and it rolls up to the size of a large drum.

- Solid panels – An 80W panel is about 1000x700mm. VERY uncomfortable size to pack away, this is the reason people consider the first two options. To reduce the packing space people use two of 50W panels with hinges, now the panels can “fold double” drastically decreasing the packing size. This is actually the same as the first two options, just much cheaper. The main drawback remains, solar panels that are packed away don’t charge any batteries. Solar panels only work when in the sun !

- Permanently mounted solar panels – the ultimate solution is to have solar panels permanently mounted on the roof of your 4x4. This way it can charge the battery any time your vehicle is parked in the sun.




Solar panels charge your battery via a “regulator”. There are basically two types of solar regulators:
- Shunt – Your solar panel will have about 16V worth of potential energy while charging, while the battery needs between 13,5 and 14,5V to charge. The shunt regulator “throws away” the extra volts. Thus reducing the potential power you can get from the solar panels.
- MPPT (Maximum Power Point Tracking) - Think of this as a reverse dc2dc charger. It reduces the potential 16V to the required 13,5 to 14,5V, and increases the charge current by the same ratio. Thus ensuring the maximum solar power is delivered to the battery.



Thanks to a number of specialist suppliers we now have access to some stunning camping equipment. Even a dc2dc charger that also has a MPPT solar connection point. These units are known as “dual chargers”.

The Ctek 250 S set the standard for dual chargers. It has a dc2dc charge rate of 20A, high enough for a fast charge without damaging the battery. But it also has a built in MPPT solar charger for your solar panels. This unit is fully automatic. As soon as you start the engine the Ctek senses this and the dc2dc charger starts about 5 seconds later. When you switch off the engine the Ctek will automatically switch over to solar charging.



HcDP now also has some dual chargers. Some need manual switching, while others switch over automatically.

[Elders]

Dual battery system


Having covered the basics in the previous “chapters”, it is now time to apply this information to select components for a dual battery system.

Let’s do this for a bakkie with the battery in the back of the vehicle and with a full power distribution system. This is how it was done 2 decades back:



Fuse at the 1st battery, then a basic heavy duty relay, and some 16mm square cables to charge the second battery.



Due to the high voltages required to charge modern deep cycle batteries this approach has now fallen by the way side. We now use dc2dc chargers, as follows:



This way we are now SURE the charge voltage is high enough to fully charge the 2nd battery. Since the dc2dc charger limits the charge current we can now use a 4 or a 6mm square wire from the front to the back. Note how the dc2dc charger is located close to the 2nd battery.
But you want to camp without having to run the engine, thus you need to add solar :




With this setup the alternator can charge the battery while you drive. And while camping the solar panel can charge the battery.

If you were to use a Ctek or HcDP dual charger your setup would look like this:




Okay, so your charging circuit is sorted, now let’s look at the distribution from the second battery:






Combine all of this and you may well have a “dual battery system” that looks something like this:

[Balljoint]

Hi Chris
Excellent information.
Could you tell me where I could get that voltage/ amp meter in your illustrations.
Regards

[Elders]

Hi Chris
Excellent information.
Could you tell me where I could get that voltage/ amp meter in your illustrations.
Regards

this unit ?






Bought it from 4x4Direct.

They are commercial members on this forum, and have a physical store in Brackenfell where you can buy a LOT of the stuff in my photos ....

http://www.4x4direct.co.za/shop/

[Balljoint]

this unit ?






Bought it from 4x4Direct.

They are commercial members on this forum, and have a physical store in Brackenfell where you can buy a LOT of the stuff in my photos ....

http://www.4x4direct.co.za/shop/

Thanks Chris for the info
Regards

[jorsman]

this unit ?






Bought it from 4x4Direct.

They are commercial members on this forum, and have a physical store in Brackenfell where you can buy a LOT of the stuff in my photos ....

http://www.4x4direct.co.za/shop/

I have a concern regarding the connection of the amp meter. The amp meter needs to be connected in series with your output, right? Now if you look at the thickness of the wires of the amp meter, what is the use of having thick cables all the way from the battery to the fridge, but inline this little piece of thin 0.25mm wire is connected in the main supply line. Help me with an explanation please.

[Fluffy]

I have a concern regarding the connection of the amp meter. The amp meter needs to be connected in series with your output, right? Now if you look at the thickness of the wires of the amp meter, what is the use of having thick cables all the way from the battery to the fridge, but inline this little piece of thin 0.25mm wire is connected in the main supply line. Help me with an explanation please.

The cables you can see are actually the sense wires that go to a current shunt.

The shunt is so short that the maximum volt drop across it at maximum current of say 50Amps is only 50 mV ie 0.05 of a Volt.

Remember that volt drop on a cable is proportional to both the cable diameter and the cable length.

[KBie]

[QUOTE=ChrisF;2270567]Dual battery system

Thanks for taking the time and effort - Great Article with sound advice

[Potshot]

Dual battery system


Having covered the basics in the previous “chapters”, it is now time to apply this information to select components for a dual battery system.

Let’s do this for a bakkie with the battery in the back of the vehicle and with a full power distribution system. This is how it was done 2 decades back:



Fuse at the 1st battery, then a basic heavy duty relay, and some 16mm square cables to charge the second battery.



Due to the high voltages required to charge modern deep cycle batteries this approach has now fallen by the way side. We now use dc2dc chargers, as follows:



This way we are now SURE the charge voltage is high enough to fully charge the 2nd battery. Since the dc2dc charger limits the charge current we can now use a 4 or a 6mm square wire from the front to the back. Note how the dc2dc charger is located close to the 2nd battery.
But you want to camp without having to run the engine, thus you need to add solar :




With this setup the alternator can charge the battery while you drive. And while camping the solar panel can charge the battery.

If you were to use a Ctek or HcDP dual charger your setup would look like this:




Okay, so your charging circuit is sorted, now let’s look at the distribution from the second battery:






Combine all of this and you may well have a “dual battery system” that looks something like this: