DEEP CYCLE BATTERIES and BUSH POWER

Thanks condor22 they are great posts.

Couple of small typo's that will confuse some in the last post.

Answer = as A=W/V then the formula is A=10/12 = 0.833 amps, it's on for 5 hours so, 5 x 8.33 = 4.17 amps. So for every similar light that is on for the same time add another 4.17 amps.

condor22, could you please include wiring charts as there is so much BS associated.

I've run 16mm square to minimise voltage drop but the local auto elec told me 6mm would be OK, had I followed that advise it would have provided about 9v for battery charging. Means can't charge & fridge shuts down. Any wonder people have problems with 12v systems.

Thanks for the info.
Barry

slowflow said:

condor22, could you please include wiring charts as there is so much BS associated.

I've run 16mm square to minimise voltage drop but the local auto elec told me 6mm would be OK, had I followed that advise it would have provided about 9v for battery charging. Means can't charge & fridge shuts down. Any wonder people have problems with 12v systems.

Thanks for the info.
Barry

Click to expand...

As I said previously, I'm getting to things like that, but I believe explaining why before explaining what and I can't do it all in one post.

Thanks wooly, bloody decimal points lol

It should read

Answer = as A=W/V then the formula is A=10/12 = 0.833 amps, it's on for 5 hours so, 5 x 0.833 = 4.17 amps. So for every similar light that is on for the same time add another 4.17 amps.

Does this help Slowflow?

redarc.com.au/handy-hints/calculator/cable_size_calculator/

Ok, here are 3 charts

1. State of Charge for the 3 types of battery;



2. Wire gauge per centimetre per amps etc;



Other charts are available giving units imperial feet, American wire gauge and amps as below.

Here's an example of where I used this information.

My auxiliary 100AGM is in the rear storage box of my 4x4, next to the Engel, so I have no voltage drop issues with powering the fridge due to its proximity to the battery.
I also have a high output 4x4 air compressor for the tyres, it draws 35 amps. So I ran a cable 2 metres long from the auxiliary battery to an external Anderson plug under the rear bumper. I used 6mm twin core cable.

Here's where I depart from chart 2 above. When people refer to 6mm cable that is the cross sectional area of the wire, NOT its diameter.

Here are those figures calculated from the metric diameters in chart 2.



Not an exact match, but I could have used 10 AWG because 2 metres will carry 100 amps and although much more than I needed I had some spare 6mm cable so I used it..

I also used a 40 amp circuit breaker (CB) in the wiring of the 2 metre cable. Remember that both the positive and the negative wires need to be of the same gauge.
This is to protect the cable, not the compressor, it has its own fuse.

IMPORTANT - When designing a cable run, system or whatever, try to keep the length of cable as short as possible. Considered thought should be given when locating each device i.e. keep the charger close to the battery, keep an inverter even closer and the higher the current of the device being powered the closer to the battery it should be.

REMEMBER - If you fuse or CB a cable place it as close to the power source as you can, if you are protecting the device being powered, put it as close to the device as you can.

Hope that all helps Slowflow

INVERTERS

I will give exact calculations to demonstrate what an inverter takes from a battery. Then add to that at the end of this post.......

An inverter is a device that converts 12 VDC battery power to 240 VAC (mains) power. They come in a variety of sizes and 2 distinct types, being;

Pure Sine Wave (PSW) - "Clean Power", more expensive.
Modified Sine Wave (MSW) - "Dirty Power" cheaper.

For my money I would not buy anything other than pure sine wave. Some devices, particularly if they have a solid state clock, may not work properly on a MSW inverter and you can "bugger" some sensitive devices that may cost more than a PSW inverter, the risk is yours.

Generally for camping they come in 150W, 300W, 600W and 1200W sizes, but are available many times bigger. My following explanation will explain why I recommend limiting the size you use.

I will use a 300W inverter as an example.

If it produces 300W at 240 VAC, the using previous formula, we divide W by V to get amps. So 300/240 = 1.25 amps. As you may note, not a lot.

Here's were it gets "hairy" - To calculate the amps required to generate 300W @ 240 VAC, the battery also needs to provide 300W, but this is at only 12 volts.
So again using previous formula, we divide W by V to get amps. So 300/12 = 25 amps.

However, (here's the bit that I add near the end) like all machines there is an efficiency loss, you never get out all of what you put in.

I had a 300W PSW in a previous caravan, I know, because I measured it, that it drew 27 amps at full power. So a 100AH battery will last less than 4 hours.

Of note, if you only power something at 150W of the 300W available, then you will only use 13.5 AH from the battery.

I have to mention this, someone on this forum said they had a 2000W inverter, at full power a 100AH battery will last about 30 minutes, be flat and probably worth keeping as a bot anchor. Plus draw close to 180 amps, that would require some serious wiring.

More.......

More on Inverters.

I now have a 150W inverter in the 4x4 and another in the caravan. They will charge phones and other small battery operated devices.

My caravan TV is 12 VDC, but if I use the Vast Satellite system it is 240 VAC, but only draws about 50 W or 4 amps. So I can watch 2-3 hours of TV on 1 battery at 100AH.

The rule I use is;

If I want any more than what a 150W inverter can give, I crank up the Honda.

NEXT - Battery Cycle life, does and don'ts (this is where it starts to come together)

To clarify a PM sent to me.

A device will have an amp (A) rating and an amp hour (AH) use.

I'll go back to the Engel;

It may be rated at 3.2 A, however it is not on all of the time (as in my 20 deg day example)

At 20 deg in my 4x4 it averaged 1 AH (rounded)

However, something like a TV that is rated at 3A will use 3AH and if on for 5 hours will use a total of 15AH

So the difference between A and AH is;

A is what it is rated at and uses when on.

AH is what is uses per hour or the total over a given time.

(Some also use W and WH, the math using the previous formula will give the same information, but I'll not confuse)

BATTERIES then CYCLE LIFE

Observations.

The lifespan of a deep cycle battery will vary considerably with how it is used, how it is maintained and charged, temperature, and other factors.

The life of an beep cycle battery can vary because of plate thickness, which goes to the quality of the individual battery.

According to industry sources, AGM Batteries outsell Gel Cell by at least a 100 to 1. AGM is preferred when a high burst of amps may be required. The life expectancy; measured as cycle life or years is excellent in most AGM batteries if not discharged more than 60% between recharge.

Gel Cell Batteries are typically a bit more costly and do not offer the same power capacity as the same physical size AGM battery. The Gel Cell Battery excels in slow discharge rates and slightly higher ambient operating temperatures. The big issue with Gel Batteries is they must be recharged correctly or the battery will suffer premature failure.

In most cases AGM batteries will give longer life or cycle life than a Wet Cell battery.

Most deep cycle battery manufactures say that their batteries are designed to be cycled to 50% of their rated capacity. So every time you take a battery below 50% you are shortening its life.

An AGM battery left unattended only self discharges at about 3% per month, and after 12 months sitting idle can be recharged without any ill effects. Conversely, a wet cell deep cycle battery will have destroyed it's self as it will no longer hold a good charge.

Wet cell batteries give of corrosive gas and should not be placed near sensitive electronic equipment or used in a confined space, they also need the fluid checked regularly.

CYCLE LIFE

This is, how many times you can partially discharge the fully recharge a deep cycle battery. One cycle is equal to using some capacity, then recharging.

From the chart below, you can see that a 50% discharge rate will give approximately 1,000 cycles, whereas a 25% discharge rate will give about 2,500 cycles.



So if you cycle once per day, 50% will give you just under about 2.7 years, 25% will give you about 6.8 years. Of note is, if you cycle 90% your battery may last a year if you're lucky.

What this means is, and, using a 100AH AGM as an example;
If you have a requirement to constantly use 50 AH a day (50%), your battery/ies will last longer if you have 200AH of capacity. The 50 AH need is then 25% of capacity.

This goes back to earlier comments that you first have to know what you need, before you decide how to provide it. Then, given that you most likely don't have mains electricity, decide on how to charge your battery.

Before, I deal with that subject, an important comment.

If you have a need for two batteries i.e. 2 x 100AH AGMs, connected in parallel, (please let me know if you need an explanation of parallel and series connection) then both batteries need to be of the same brand, capacity, age and if possible manufacturing batch. If one of the batteries is weaker than the other, it will drag the better one down to its level.

I am in the process of assessing my new caravan's battery, it came with an 80AH GEL @ approx 25kg. I would prefer it to be an AGM and I want more than 80AH. It is far better for me to look at 1 x 160AH AGM @ about 46kg, than buy 2 x 80AH @ a total of about 50kg and parallel connect them. Plus one big battery takes less space than 2 smaller ones. I will also need to reassess the charger.

Next - Charging batteries in the bush (As charging differs depending on battery type, and, I would only ever advocate AGM, that is what I will base charging on).

CHARGERS

As I said previously, you should only ever charge a deep cycle battery with a "smart charger" (multi stage).

The following stage names have come from commercially available multi stage chargers and are in the order they start charging at;

7 Stage Charger - Desulphation, Soft Start, Bulk, Absorption, Analysis, Recondition, Float.
5 Stage Charger - Soft Start, Bulk, Absorption, Float, Pulse.
3 Stage Charger - Bulk, Absorption, Float.

I have successfully and only used 3 stage chargers on AGMs, so that is all I am going to describe. The more stages, the more they usually cost. If readers wish to find out about 5 and 7 stage chargers use "Google".

3 Stage Chargers explained;

This is best explained on this website http://www.chargingchargers.com/tutorials/charging.html

But in brief
BULK stage involves about 80% of the recharge, current is held constant and voltage increases.
ABSORPTION stage - for the remaining 20%, approximately the charger holds voltage and decreases the current until the battery is fully charged.
FLOAT stage the charge voltage is reduced to between 13.0 VDC and 13.8 VDC and held constant, the current is reduced to less than 1% of battery capacity. This mode can be used to maintain a fully charged battery indefinitely.

Next post - Different types of batteries, i.e. Wet, Gel and AGM need charging differently............

Differences.....

• Typically the bulk charging voltages are; 14.1V (GEL), 14.4V (AGM), 14.7V (WET), 14.7V (CALCIUM)[/*]
• Typical Absorption voltages 14.2 to 15.5 depending on battery type.[/*]
• Typical Float voltages 12.8 to 13.2 again depending on battery type.[/*]

However, most good quality 3 stage chargers have a mode switch or function that allows the user to choose their battery type and the charger does the rest automatically.

How big a charger do I need? The rule of thumb is C/5 or capacity divided by 5.
So for a 100AH battery a 20A charger is the choice. But batteries come in different sizes, 1/5th of an 80AH is 16A and 1/5th of a 120AH is 24A.

My choice would be to get the closest charger size to the calculated amount erring to next size up. Most chargers come in 5, 10, 20, 30, 40 or 50A sizes.

As I said before if it's way to small it may never fully charge and if it's way too big you'll bugger the battery.

Next post - How you power your charger.........

Chargers cont.

OK, assuming we are running a smart charger, of some kind, to charge our deep cycle battery and it's a reasonable quality device, how do we power it?

There are several ways to do this, the input can be either 240VAC or another 12VDC source.

First, the 240VAC type;

This type of charger is the type generally fitted to modern caravans and or motor homes. They will charge your battery when on "shore power" i.e. a caravan park or at home. The only practical way of providing 240VAC out bush, is to run a generator. I am going to cover generators further into my posts, but suffice to say, a 1kVA (1,000W) generator is plenty big enough to run a camp battery charger. The important thing to remember, going back to PSW and MSW inverters is, some of the cheaper generators use modified sine wave to produce 240VAC. This will most likely stuff a good quality charger due to the sensitive electronics inside the charger.

The next way to power a charger is via 12VDC, this can be produced by your vehicle alternator or by solar panels.

Alternators - As a vehicle alternator is a fixed voltage and usually 13.8VDC it is not a smart charger. The use of a 12v to 12v smart charger is my recommendation, something like the Redarc BCDC1220 works well (I have one in my 4x4). They can suffer a degree of voltage drop at input (as low as 11VDC), are configurable to the type of battery being charged, are a smart charger and wired correctly will not flatten the vehicle's primary battery when the vehicle engine is off. There are other brands commercially available.

I have no affiliation with Redarc or any other provider

Next Post - Solar input to a charger.

Solar charging.

A solar charger is usually referred to as a solar controller or solar regulator. A solar panel typically produces 18-19VDC at the panel. Some regulators only drop the voltage to a nominal figure approx. 12 to 13.8 volts, it is an output, not a charger, beware of this.

A good quality solar controller is not only a voltage regulator, but also is a smart charger, is configurable to battery type and is a data logger as well. Data logging is where the device records, in simple terms, how much power the panel has produced and how much power you have used. I'll make some comments re solar, that I will better explain later in a practical example.

NB - Regardless of system design, you need to manage it. Simply, you need to know what power you use to ensure adequate recharging and have the correct gear to do that.

Your demand upon a battery may be 24/7, however, remember that solar power is only produced during daylight hours. So the panel output over the number of "sun hours" it is exposed to, needs to be enough to cover all of your use, to be truly independent. Sun hours will vary greatly, depending on location, time of year or weather.

As solar power is variable, a system's design needs to follow this basic criterion; Design for the worst case output against the maximum demand.

A mix of solar, alternator and generator is always the best option as it offers both flexibility and assurance.

All solar panels aint always the same; There are different types and they have differing pros and cons.

Next Post - Generators, then subsequent post -An example of a solar, 240VAC system in a caravan, how, what and why.......

Generators .....

I have previously described what kVA means, but I will reiterate some of the previous stuff and bullet point some statements.

• As far as I am concerned, you get what you pay for, I would only ever use Honda or Yamaha, they have national service warranty and lets face it, if something is going to fail it will most likely happen out bush when using it. Some of the knock off dealers require you to ship back to them and that could be the other side of the country from where you are. I have no affiliation with Honda or Yamaha.[/*]
• A 1000 W generator will supply approx. 4 amps of 240VAC and a 2000 W about 8Amps.[/*]
• Noise - The Honda and Yamaha are generally much quieter than other generators. To explain sound; dbA is a unit of sound measurement, the Honda Eu20i is rated at 59dbA full throttle and 54dbA on eco throttle. dbA is a logarithmic value, each 3dbA increase is twice the sound level i.e. 6bdA is 4 times, 9dbA is 8 times and 12dbA is 16 times the noise level etc. Sound is measured at a distance of 1 metre from the source, in simple terms, if you double the distance you halve the sound. So when you see another brand (on sale at a national hardware chain) of the same output of 2000 W advertised its noise level of 72dbA, it is approx. 16+ times louder than the Honda.[/*]
• A 1kvA generally weighs a bit over 20kgs, a 2kvA a bit over 30kgs. Consider this when you think about a 3+ kvA el cheapo.[/*]
• The Honda and Yamaha (with a special cable) can be ganged i.e. 2 x 1000W Hondas can be joined to produce 2000W etc. Most of the rest can't.[/*]
• A noted 1000 or 2000W generator doesn't actually produce that amount constantly, that is maximum. The constant rating is more like 800 and 1600W. The Honda/Yamaha will handle up to 3000W start up current for an aircon, many cheaper ones won't.[/*]
• A 2000W Honda/Yamaha will operate most caravan air conditioners and charge the battery at the same time. It will not however operate the aircon and the microwave at the same time.[/*]
• The 12VDC output is exactly that, a12VDC supply, it is not a battery charger.[/*]

I have both studied and worked with sound power measurement in years gone by.

The most important thing about cheaper generators is this.

I noted earlier that a PSW Inverter is more expensive than a MSW one.

The same thing can be said of generators, the petrol engine runs a nominal 12 volt generator which then uses an inverter to produce the 240VAC.
Honda and Yamaha are pure sine wave, just because the cheaper ones state "Inverter Generator" does not mean it is pure sine wave.

Be aware of this when making your choice, because most good smart battery chargers don't play nicely with Modified Sine Wave generators.

Next - I have given some thought to a practical example of a bush battery/power supply and have decided to do two. One for caravans and one for camping in a tent. They will be examples, please be aware that there are many different ways of achieving similar results, it depends on individual choice. This will be a few days away as I'll draw the relevant wiring schematics as well.

condor22 said:

Chargers cont.

Alternators - As a vehicle alternator is a fixed voltage and usually 13.8VDC it is not a smart charger. The use of a 12v to 12v smart charger is my recommendation, something like the Redarc BCDC1220 works well (I have one in my 4x4). They can suffer a degree of voltage drop at input (as low as 11VDC), are configurable to the type of battery being charged, are a smart charger and wired correctly will not flatten the vehicle's primary battery when the vehicle engine is off. There are other brands commercially available.

Click to expand...

Some newer vehicles (inc mine) which are not designed for dual battery systems may have a 'smart alternator' which ain't that smart at all if you install a DC-to-DC charger and second battery in the boot or wherever. These alternators sense when the cranking battery is fully charged and then stop providing current or go into a 'trickle mode'... which is no good if you are trying to recharge the second battery on the move.

Some smart chargers include a built-in gizmo to trick the alternator into thinking the cranking battery is not fully charged so that current can continue to flow to the DC-to-DC charger for the second battery. I think REDARC has one that does this, whereas CTEK offers a stand-alone gizmo that needs to be wired into the system. In either case, there is an extra $$$ cost associated with being able to trick the 'smart alternator'.

I have a CTEK D2500S DC-to-DC charger wired to a second battery in the boot but not the additional gizmo. So, my approach to ensuring the 'smart alternator' continues to pump current to the CTEK charger is to drive with my headlights on (which I'd do in any case for country driving) - seems to do the trick for me. :8