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Solar aids battery power, but keep your balanced systems

February 10, 2006
Solar aids battery power, but keep your balanced systems

Battery powering a good camping holiday is a complicated question.

And when it is time to make it work the problem is often you!

Now, dont be like that, we are here to help with Battery World and Old Head experts we know . So, lets consider solar power feeding batteries.

To arrive at the best systems to suit a caravanners needs, good suppliers go to great lengths to draw out what the client wants to power.

But the addition of a litany of power draining additions from the caravan or motor home owner can make the potential power source hit the wall.

As a Battery World spokesman relates ... In one case after a long protracted series of calculations the customer finally said the Air Conditioner words ... at that time all thoughts of solar power just did not have enough roof space to accommodate what they wanted. It was a clear case of forget the batteries stick to powered sites.

When dealing with solar power to charge batteries the suggestions in this feature are the practical considerations of what works in practical terms.

Battery World says there has been a long term argument about Deep Cycle and Marine batteries in the end result it comes down to the horse for the course and battery suppliers can only recommend on thebasis of the client's requirements and information provided.

Getting accurate information is often very difficult this is, however, not so much from inaccurate appliance labeling but customers who forget the 1500 Watt hair dryer used daily or that they actually watch more TV via an inverter than they admit to.

Battery World says they have more people that turn up in Broome or Alice Springs, Cairns or Darwin having had an horrendous trip due to lack of power. This is sometimes caused by under quoting by suppliers but is often because the original power audit did not include many appliances added by the caravanner.
Editor's note: Place your cursor on thepictures to read the captions.

Battery WorldSo here is some basic battery translation to help the how much power is needed decision

Battery World says when M series batteries are discussed it probably refers to Century batteries ... Marine batteries are generally a hybrid combination starting battery with some deep cycle properties.

This allows them some rapid charge facility in combination with Cyclic ability, being an antimonial alloy it has good recovery from discharge unlike Calcium alloy batteries where a discharged battery builds up high internal resistance and often require a much more significant charger to get the battery to take charge.

The selection of the battery type is as critical as the whole power bank equation. When budget enters into the calculation generally all objectiveness to make the system work is eliminated.

It is difficult to balance a solar/battery bank because of the extremely elastic conditions.

For example high temperatures mean the fridge will work harder and the battery will be put under extreme load. If this is followed by cloudy days where peak sun is not harnessed to the full by the solar collector then power available will fall away. Many variables must be considered so significant buffers should be built in to the equation.

Editors note - Refer Simple Solar Math at the end of the feature.

Battery World says that solar panel outputs are generally correct but conditions are so variable that a straight lineal calculation is usually wrong. For example, to collect an average six hours peak sun in Queensland thesolar panel has to be north facing and tilted to a 15 degree angle to the sun. The question is really how many caravanners will take that amount of trouble and by association how many prefer to enjoy their caravan, motor home or RV parked in the shade?

Charging the batteries is of course crucial, we would never recommend pure solar only,the Battery World spokesmantold Go SeeAustralia.

It is possible, however, to come close to a balanced system which can be topped up via a dual battery system take off from the alternator. Again this needs the right advice and care to ensure the alternator is big enough and the customer understands the driving time needed to recharge a 75 Amp or bigger battery.

Cabling size is also critical, particularly if the caravanning holidaymakers are trying to charge a battery in a caravan some 6m away from the alternator.

Or a good inverter/charger should be recommended so that when the customer arrives at a powered site they can recharge batteries. Most caravanning or motor home people will look for a powered site every five to seven days maximum for a decent shower, washing machine, reliable quick internet connection and a swim in the caravan park pool.

The addition of a generator may be a useful tool but does add extra weight, plus fuel and cannot be used in many National Parks (as it upsets the wildlife, especially those in the next camper). A generator should also be pure sine wave 240V output otherwise any electronics may well be history within a short time.

Solar is not a reliable solution on its own, Battery World says.

Simple Solar Math for simple souls

Q How long will my battery last when I go camping?

A How large is your Deep Cycle battery? Expressed in Amps over 20hrs i.e.; Amp Hours (Ah).

To protect your battery try to maintain a 30% safety buffer (never totally discharge your battery.
Next part is what are you running?

Typical camping needs

Waeco CF50 50 litre fridge (runs at 45 Watts per hour 32% running at 30C ambient) i.e. Watt hours (Wh)

I.e. 45 Watts x 8hrs divide by voltage 12v = 30 Amps per day 30Ah

Lights 2x 13 Watt fluorescent about 3 hrs a day

26 W x 3 divided x 12 = 6.5 Amps per day 6.5Ah

Television via an inverter

35 Watt x 90% efficiency for inverter say 2.5 hrs a day

35 W x loss = 39 W x 2.5 divide x 12v = 8 Amps per day 8Ah

Radio / player

10 watts 2 to 3 hrs say 2 Amps per day 2Ah

Total daily load 46.5 Amps consumed per day 46.5Ah

Divide 70 % of the battery rating by the daily load

A 100 Ah battery will provide approximately 1 and days power in this situation.

How can I extend my camping trip?
Well, you could take a generator, but many parks do not allow generators to be run because of the noise and it does stress wildlife especially those parked in the next trailer

Solar power
An average 80 Watt solar module will collect an average annual daily peak of 5.5 peak sun hours in NSW maybe 6 in Qld (less in southern states )(that is with the panel fixed facing sun) Camping in summer will increase that average daily collection.
80 Watts X 5.5 hrs divide by voltage (nominal specified by the panel Mfg) = than 36 Ah per day
Not enough to run all your power needs.
Now try sun tracking put the panel on an angle to maximise sun power facing North East in the morning, Due North in the middle of the day and North West in the afternoon. You will collect possibly 7 - 8 hrs per day or even more. Remember panels are expensive never leave them unattended.
80watt x 7.5 divide by panel voltage = Collected power Almost 50.0 Ah
That replaces all your daily needs
Start with a fully charged 100 amp deep cycle battery Power Bank
So on the first day you use 46.5 Ah of 70/100 Ah 53.5 Ah
Second day replace 50. Amps back to full power. 100 Ah
Now what will this cost?
Here is a typical shopping list
BP, Solarex or Kyocera 80 watt panel or a Unisolar 64 Watt amorphorous silicon panel
Regulator (to prevent the panel from overcharging the battery)
Deep Cycle battery (N70T 75 Ah rated at 20hrs)
Hold Down and tray (or Battery Box a little extra)
Indicative pricing about $1,100
Plus installation at cost, ask your local store to arrange.
Where do you get it?
Any Battery World Store. In Australia Call 13 17 60 to connect to your nearest store,
Or web site

Also see:
Simple Solar Math continued . . .
Watt rating
Hours use
Watt Hrs
A x B =
Divided x volts
Waeco fridge CF 50 on power 2 setting at 30C ambient
Lights x 2
Radio / player
Daily load
Your List Below
If in any doubt on what to do just fill in the appliance and the number of hours expected use Battery World will calculate based on standard estimated power use.
Watt hrs
Appliance description
Contact number:
Fax this sheet to Battery World (07) 3373 1770 in Australiaand they will calculate your power requirements and advise the typical costs involved in satisfying those needs, both battery bank and solar panels.
To Visit Battery World in Australia ring 13 17 60 for nearest location.

Copyright Intellectual property contained in this document belongs to Battery World Australia Pty Ltd and may only be reproduced with the permission of the author. The use of this chart is a guide only and Battery World and GoSeeAustralia and GoSeeNewZealand will not in any way be responsible for incorrect interpretation.