DEEP CYCLE BATTERIES and BUSH POWER

My contribution re independent power...........

I've given a deal of thought as to how to tackle this topic, bearing in mind that some readers will have technical expertise on this subject, others will have very little. So, I have decided to keep it simple and try not to baffle with science. My posts may seem incomplete in isolation, but when put together will hopefully build a complete picture of the things that need to be considered when looking at a battery system. Before I start a few things need to be stated;

In any design, there are numerous solutions, some better, cheaper and easier than others, but not necessarily right or wrong. It truly is in the eye of the beholder, depending on ones personal needs.
Everyone, with a little knowledge may have a different opinion, that's fine, everyone's entitled to theirs. I say this because I'm not doing this to argue a point of view, but to impart some basic knowledge.
Battery system design, will differ from in vehicle to, in camper, to in caravan, to in motorhome, to off grid home design, but the science is similar.

OK, onto batteries, as most of the forum discussion has been with regard to 12 volt camping power, I will centre my posts around this area of independent power, noting that "in vehicle" will vary a little.
Batteries - A battery is a storage device, it does not generate power, much like a water tank. When the level goes down it needs to be refilled or recharged. In this post and subsequent posts, I will cover the common battery types, their differences, pros and cons, types of recharging, solar panels, generators, load calculations, wiring, fuses, circuit breakers, voltage drop, Ohms Law and anything I haven't yet thought about.
Although there are new technologies surfacing, in terms of vehicle and deep cycle batteries, there are 3 distinct types;

Cold Cranking Amps (CCA) - The common starting battery in vehicles, designed to give short bursts at high amps (up to 300 amps) Commonly charged by the vehicle alternator.
Deep Cycle Battery - Designed to provide a relatively constant current, (i.e. a portable fridge at 3-4 amps over many hours). Commonly charged by a smart charger, solar array and with other considerations, the vehicle alternator.
Calcium (Ca) - I call this a hybrid battery, that will start a car and provide deep cycle power as well. They also require very specific charging rates and voltages. I believe that when something like this is an "all round" item, it doesn't do CCA or DCB functions as well as the specific function battery.

As this post is with regard to DCBs, I'll say no more about CCA or Ca batteries.

Next post - Deep Cycle Batteries..............

Deep Cycle Batteries (DCB)

Commonly fall into three distinct types;

Flooded Valve Regulated Lead Acid (VRLA)
Gelled Electrolyte Lead Acid (GEL)
Absorbed Glass Mat (AGM)

They fall into various quality levels in each type. Price is dependent on design, processing, and manufacturing costs. Like in all things, higher quality means higher cost, but as I've said before, you get what you pay for.

VRLA - These have been around for decades. The electrolyte is liquid sulphuric acid, which is corrosive. VRLA batteries generate and vent dangerous explosive gases through their valve regulation and must be vented to the outside world. These batteries also acid "mist" during charging and discharging. This leads to the corrosion of their terminals, and damage to surrounding surfaces. (look at your car battery for an example) VRLA Flooded batteries must be installed upright, can leak that acid, and require regular watering. That all being said, they are also the least expensive type.

GEL - They were introduced by a German Company about 30 years ago. Their acid is immobilized by adding "fumed" silica to the sulphuric acid solution and then sealing the battery. They internally recombine most of the gases (hydrogen and oxygen) generated during charging and are maintenance free due to this. Gel electrolyte is highly viscous and during charge and discharge the gel can develop voids or cracks when the amperage is increased. These pockets impede acid flow and result in the loss of battery capacity. Gel batteries may store hydrogen gas that has not recombined. When overcharging causes a gel battery's vent caps to open, explosive gasses may be vented into the battery compartment. This vented hydrogen has caused a number of "fast failures" or battery explosions.

AGM - Were developed to provide increased safety, efficiency, and durability over all existing battery types. In AGM batteries the acid is absorbed into a very fine glass mat and held in place by capillary action. This construction technique, in coordination with double wall design, and sealing has many advantages.

The acid is never free to slosh around. This allows for installation at any angle, even upside down.
Gas recombination is more efficient (99% AGM). This leads to fewer exploding batteries than either of the 2 types above.
The AGM material has an very low electrical resistance, so the battery delivers much higher power and efficiency than other battery types.
Since the AGM material has a low electrical resistance it can charge and discharge more amps without cost to life. AGMs are rated at 100% their capacity for charging and discharging amperage, compared to roughly 35% for gel and flooded)
Less acid means a lighter battery
AGM batteries offer far better life cycles than either gel or flooded batteries.

When DCBs are used, each charge and discharge is called a cycle. Battery life is dependant on the number and depth of cycles completed. A Deep Cycle battery is designed to recover from a deep cycle. However, it should be noted that a VRLA or GEL battery flattened to 100% will not fully recover and it's life is drastically reduced. An AGM will recover and although it's life is also reduced, it is significantly less than the other two types.

Conclusions -

VRLA - Pros - The cheapest and easiest to charge. Cons - More maintenance and management, requires a fully vented area and the most DANGEROUS.
GEL - Pros - Less chance of spill, less maintenance, semi confined areas are OK. Cons - More expensive, require more specific charging than a VRLA or could be DANGEROUS.
AGM - Pros - Maintenance free, work at any angle, totally spill proof, will cycle deeper and longer, work in sealed compartments and the SAFEST of the 3 options. Cons - Cost the most and require specific charging. (However, it should be noted that $ per cycle per year could well work out the cheapest in the long run)

I've always used AGM deep cycle batteries, primarily because they were installed under my caravan dinette seat and I have too much respect for my bum than to sit on a potential bomb. Also they love the constant charging of solar without having to check fluid levels.

Next post - Battery care, maintenance and charging rates................

Good info Condor.
I did have an AGM in my camper trailer, cost over $300.00 and it didn't make the trip between Brisbane to Dajarra--must have fractured the glass matts----had to buy a new Deep Cycle batt $230.00. Threw away the AGM because it weighed a ton couldn't really take it on my round Australia holiday could i---
ps Have used Deep Cycle ever since --no worries.

@Condor22,
Well done mate, good info and not too baffling for the 'dummies'! (No offence intended!! but referance to the 'dummies books!!')
I'm an electronics tech an would love to add info to your thread if required.
Again, well done!
Simmo

Jaros said:

Good info Condor.
I did have an AGM in my camper trailer, cost over $300.00 and it didn't make the trip between Brisbane to Dajarra--must have fractured the glass matts----had to buy a new Deep Cycle batt $230.00. Threw away the AGM because it weighed a ton couldn't really take it on my round Australia holiday could i---
ps Have used Deep Cycle ever since --no worries.

Click to expand...

Jaros,

As I said in my article, an AGM is a deep cycle battery. A 100AH AGM typically weighs 34kg, a 100 AH Gel weighs about 35.7kg. I wouldn't entertain a wet cell for campers, caravans or in a tent when moving them around.

I've had 6 off 100AH AGMS and never had an issue. Most are built to MIL SPEC and in fact that's what they were originally designed for.

Simmo said:

@Condor22,
Well done mate, good info and not too baffling for the 'dummies'! (No offence intended!! but referance to the 'dummies books!!')
I'm an electronics tech an would love to add info to your thread if required.
Again, well done!
Simmo

Click to expand...

Thanks for the offer Simmo, how about you wait till I finish my topics and then if you think you can value add, go for it.

Note: Battery life will vary considerably with how it is used, how it is maintained and charged and operating temperature.

Battery Charging - To maximise the cycle life of a deep cycle battery, they need to be charged with a "smart charger". Smart chargers come in a variety of stages i.e. 3, 5 and 7, however to simplify the process I'll cover 3 stage only.

Three Stage Chargers - Battery charging takes place in 3 basic stages: Bulk, Absorption, and Float. A good quality multi stage charger will also have a mode option where the user can select the type of battery being charged i.e. lead acid, gel, AGM and even Calcium. The reason for this selection is the different charge voltages and rates applied to the various batteries.

Bulk Charge - The first stage of 3-stages. Current (amps) is sent to batteries at the maximum safe rate they will accept until voltage rises to near 90% full charge level. i.e. Assuming a 100AH battery is 80% charged, a 20 amp charger can take a bit over 30minutes to replace the first 10% of the charge, then,

Absorption Charge: The 2nd of 3-stages. Voltage remains constant and current gradually tapers off as internal battery resistance increases during charging. It is during this stage that the charger puts out maximum voltage. Because current tapers off in this stage the remaining 10% can and will take longer than the 10% charged during Bulk charge (1 to 2 hours depending on battery).

Float Charge: The 3rd stage. After batteries reach full charge, charging voltage is reduced to a lower level (typically 12.8 to 13.2) to reduce gassing and prolong battery life. This is often referred to as a maintenance or trickle charge, since it's main purpose is to keep an already charged battery from discharging.

Next Post - Some facts and fallacies..................

This post, some myths busted.........

FACT - Most "garage" automotive battery chargers (single stage chargers) are bulk charge only and have little, if no, voltage regulation and will likely destroy a deep cycle battery. They are fine for quick boost to a low battery, but should not be left on for any length of time.

FALLACY - The 12 VDC output of a generator will charge a battery. The fact is that it will not, a battery charger will typically produce between 13.8 and 15+ volts, to charge a 12 volt battery. However, given that a fully charged 12 volt battery open circuit tests at 12.8 volts, the logic is that you need to charge at a higher voltage than the battery outputs. A generator 12VDC output is exactly that a 12.0 VDC output.

FACT - Generators aint always generators. The "el cheapo" generators available from some stores and online will produce 240 VAC, but they are not as reliable, they are noisier, can use more fuel and probably produce "dirty power" (to be explained in a later post).

FALLACY - A deep cycle battery, for arguments sake a 100AH, will give me 100AH of power. It may well do so, but at what cost. (again, explained later)

FACT - A vehicle generator will charge a deep cycle battery - BUT - It will not fully charge something like an AGM. The charging rate of a vehicle alternator is typically 13.8 VDC, the required charging rate for an AGM is 14.2 VDC.

Next post - A glossary of terms (because the following post will be a bit of Ohms Law and some example calculations)..........

GLOSSARY

Ohms Law = Deals with the relationship between volts, watts, amps and resistance.
Volts - Abr = V - Analogy = Akin to the pressure in a water pipe.
Amps - Abr = A - Analogy = Akin to the flow rate of the water in a pipe. Also called current and abr = I (uppercase i )
Resistance - Abr = R - Analogy = Akin to the pipe dia or size.
Watts - abr = W - The measurement of electrical power.
VAC = Volts Alternating current, what you typically get at home i.e. 240 volts
VDC = Volts Direct Current, what your car typically produces i.e. nominally 12 volts.
AH = Amp hours, simply explained by stating that a 100 AH battery will give 100 amps for 1 hour or 10 amps for 10 hours or 1 amp for 100 hours. (the math is not exact regarding this, but it simplifies the explanation.)
Solar Panel = Usually considered the overall assembly including frame, cell matrix and output wires.
Solar cell = One of the rectangular components of the solar panel matrix.
Solar Controller or Charge Controller = The little box that regulates a solar panel output. (panels typically generate VDC in the high teens i.e. 18 to 19 VDC. A solar controller will reduce this to the correct charging voltage for the battery type being charged.
Inverter = A device that typically converts 12 VDC to 240 VAC (in this context)
Transformer = A device that typically converts 240 VAC to 12 VDC (in this context)
Generator = Typically a petrol driven motor that drives a 12 VDC generator, then converts it to 240 VAC using an inverter.
Rectifier = An electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction.
Pure Sine Wave (PSW) = The smooth waveform generated by VAC (where it changes + to - so many times a second i.e. in Australia's 240 VAC system this is 50 cycles per second or 50Hz) Also known as "clean power"
Modified Sine Wave (MSW) = The waveform generated is a "chopped" rectangular pattern where the waveform rests on zero for a few milli seconds, whereas a PSW crosses zero cleanly. Also known as "dirty power"

Next post - A bit of Ohms Law and some simple Math........

Your indication of V and I etc with the introduction of an acronym of ABR gives confusion.
Lets clarify and say that for example, that VOLTS is abbreviated or abr to V...
Sorry to interfere.......

That's not interfering Simmo. When I did my training with the PMG in the mid 60's, "E" was used the abbreviation for Volts. EMF meaning electromotive force.

Thanks Jaros.
Yeah, a lot changes eh?! I did my training in the RN in the 80's however now contract for who you started with! Oh and that new NBN mob too!!
Condor's info is really good, because a lot of us that go out bush all the time, need the gear, but don't quite understand how to put it together.
Breaking down stuff that took us tekkies years to learn, into simple talk, is the way to go!

Aah English, what a "great" language.....

Oki, decided to keep it simple or should I say more simple than.....(Ohms Law to follow)

W = Watts
A = Amps
V = Volts
AH = Amp hours

These are the only units, I am going to explain in more detail in later posts, however,

I will give this brief explanation of R or resistance and its effect in the context of bush power.

As I said before the analogy is the size of the water pipe, in context of electricity it is the wire size. A good example of resistance is a strip heater. This is a coil of wire of a diameter that creates so much resistance to the electrical input that it gets hot, which is what we want.

However if we want to provide power along a cable to supply another device, without losing that power to the resistance of the cable, we need to have a wire big enough for the electricity to flow unimpeded.

So, when we look at cable sizing, another good example is a normal household power point is rated at 10 amps, a caravan input cable has a 15 amp connection. (the difference is that the earth pin is bigger on a 15 amp plug so it will not fit in a 10 amp socket. The reason is that 15 amp cable, which is also heavier, will carry more power, the 10 amp socket and fuse/circuit breaker won't.

This also explains voltage drop with regard to distance versus cable dia. A cable of a given diameter and length will have a specific resistance. If the length is doubled, then the resistance increases and a voltage drop occurs. So if the double length is required, to prevent voltage drop the diameter needs to be increased.

This becomes more critical in low voltage systems such as 12 VDC than with 240 VAC. Also note, that both V and A have are affected by cable size.

There are plenty of charts available online to help you design a system without having to understand the math. I'll provide links when I get to that topic.

Very helpful. thanks for taking the time. Any plans for a write up on lithium ion batteries?

nuggetino said:

Very helpful. thanks for taking the time. Any plans for a write up on lithium ion batteries?

Click to expand...

Wasn't planning re camp power, but can add on when I finish this.

Thanks for the info
I'm planning my camper trailer build after Xmas.

Ohm's Law

I=V/R or V=IxR or R=V/I Where I = current or amps, V = volts and R = resistance

However, I'm not really interested in resistance in this context. What I am interested in is real power calculation, using volts amps and watts. The formulae
for power calculations are;

A=W/V or W=VxA or V=W/A Where A = amps, W = watts and V = volts.

Enough of the theory for now, I will give an actual example I measured on my Engel, using these formulae, running in my 4x4 on 2 different days, one at 20 deg celcius, the other at 40 deg celcius ambient temperature. Also listing the equipment I have and method.

Equipment;

100AH AGM deep cycle battery
Powertech power monitor (Jaycar) Records Present V, W, A - MAX V, W, A - MIN V, W, A & AH used.
Engel 29 litre fridge (circa 1993, as good as new.)

Method;

The fridge was half full of drink cans, it was pre cooled on 240VAC, to run at about 3 degrees, the battery was fully charged. As my Auxiliary battery is charged via a 12 volt to 12 volt charger when the car is running, I did this test on a day when I would not use the car for at least 24 hours. At 8am I switched the Engel over to 12 volts and took measurements of the volts, amps it was drawing and zeroed the power meter.

20 deg day - Battery volts at start = 12.9 no load and = 12.7 when the Engel was turned on.
The amps at start = 3.2 (This varied from 2.8 to 3.2 most likely due to temperature)
After 24 hours Battery volts = 12.6
AH used = 25 AH (which is 25% of battery capacity)

40 deg day day - Battery volts at start = 12.9 no load and = 12.7 when the Engel was turned on.
The amps at start = 3.2
I only ran this test for 8 hours (8am to 4pm) and Battery volts = 12.5
AH used = 26 AH (which is approx 25% of battery capacity)

So using simple math, if I use 25 amps in 24 hours, the Engel averages 1.04 amps per hour, but approx 3.0 amps when running. So, I now know that the thermostat cuts in for approx 20 minutes each hour on average on a 20 C day.

However on the 40 C day I used 26 amps in 8 hours which is 3.25 amps per hour. This means that the Engel was going pretty well all of the time and working hard. But, I also know that once the sun went down, it would use less overnight. I wasn't game to use so much battery power, so I ended the test at 8 hours. I guesstimated that had I continued the test for 24 hours, I would most like have used at least 50AH of my battery, which is 50% of battery capacity.

Using twice the power for the same device in different circumstances is one lesson, but will become more evident re battery life in later posts.

Next post - more on V, W, and A

More V, W, and A

again using;

A=W/V or W=VxA or V=W/A Where A = amps, W = watts and V = volts.

Many devices, particularly 240 VAC will give V and A or V and W, but not necessarily all three, so some examples of power calculations, both 240 VAC and 12 VDC.

We all know of the 1kVA or 2kVA generator. Firstly explaining kVA;
k is the abbreviation for 1,000 and as you know V = volts and A = amps.
Putting all 3 symbols together is also an abbreviation for multiplying the symbols.

ergo - 1000 x 240 x 8.33 = 2000 and we know V x A = W so this explains a 2000W generator.

Next example is an electric kettle. Assume 240 VAC, most are rated at 2400 watts.
using A = W/V then 2400/240 = 10 amps (substantial if using a power board with other items on it, when most are rated at 10 amps total)

Next, let's take a 10W, 12 VDC quartz halogen or Xenon down light in a caravan. Assuming we have it on from 6pm until 11pm, how many AH are used.

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.

Conversely, and you will have to trust me here, a similar shaped LED down light uses far less. My previous caravan had 10 down lights that used a bit over 9 AH when all on. (all Xenon) I replaced all of them with LED equivalent. The result was that with all 10 on the current draw was about 1 amp. This worked out to 1/10th the power consumption and therefore much more time between needing to charge the battery.

My final example is a caravan water pump, it uses about 6.5 amps when operating. To calculate daily requirement (assuming you have a shower in the van and do the dishes once a day), you need to add each usage. This may be 2 x 5 minute showers and 5 minutes at the kitchen sink = 15 minutes. So 6.5 amps x 1/4 hr = 1.625 amps.

Where am I going with the previous examples? The answer is this:

BEFORE YOU DESIGN ANY BATTERY SYSTEM - You need to work out what you actually want to power (that means every device you are likely to want). THEN, You need to estimate it's daily use in hours or part thereof and add them up. That will then give you a total AH requirement.

How to apply this, will be in the next post.

WARNING - Many, but not all salespersons will only sell you what makes them money. It may not do what you want, but if you don't ask the right questions, you'll never get the right answer.........

It's said a little knowledge can be dangerous, but it can save you doing a job twice and therefore paying for it twice !!!

At this point I'll say "my previous posts may well be a lot to digest, but when I have finished, I'll summarise into a shortish, simple practical example that will hopefully make sense if you remember the important bits of the previous posts." (and those to come)

So stay with me.

Still to come;

• Inverters[/*]
• Battery cycle life[/*]
• Chargers[/*]
• Solar [/*]