E-News Issue #76
A battery charger is a great back up to a solar system, particularly when you get several days of rain or someone in the house decides they want to watch the cricket for 3 days straight! The Australian made Woods ‘Dialomatic’ chargers are robust and also have the advantage that they can charge an individual 2 or 6 volt battery. For October, we are offering 10% discount off the published price of our 12V-30A model (40A peak). Check out BCH-032 on our website for more details.
Electric fencing can be a cost effective and practical method of fencing for a wide variety of animals.
There are several brands and models available from rural agricultural stores which are battery powered as opposed to being powered by the 230V grid. The battery type units can then be powered by solar modules.
Due to the wide selection of energisers and accessories on the market, we no longer sell the energisers. However, we can supply you with a suitable solar panel and battery.
When you buy the energiser, only buy one as big as you require, e.g. if a 3 km unit will do the job, don't purchase one for 20 km, as they will need a solar panel several times larger and more expensive than you’d otherwise require. A 3 km energiser can be typically powered by a 2W solar module.
Several months ago one of our readers, Jules, submitted some hints about using electric fences which is reproduced below:
I have used a number of different electric fence units, from small to medium large, to power up to several kilometres of fence, and I believe that they are an almost essential part of fencing. In theory, smaller units are fine for shorter fences, but in practice, shorting out from long grass/plants is an unavoidable drain in most situations. Medium and large units are available using 12V power and either an attached solar panel or a separate panel. The units with a built in solar panel are rather costly for what you get and the logical conclusion might be to run your fence off your 12V home battery bank/solar system. Provided all the connections are good, and the unit is operating properly, this causes no more trouble than a pulse across your TV screen with each fence discharge. There are however two major problems that inevitably crop up over a longer (several year) period:
a) As mentioned in your book (Energy From Nature), lightning is a hazard to electric fence units. Even if you do not have any direct strikes of lightning, a farm fence is a custom designed electricity catcher. It is of course possible to use diverters to earth (most) of a lightning strike and it is sometimes possible to detach a fence during a storm (though this could be dangerous in itself). The problem with lightning is that the voltages generated are just so huge that any form of protection has its limits.
b) Electric fence units are subject to more failure than most other electrical equipment. I’m not sure why this is, but I'd guess that the mixture of low voltage with strong pulses of high voltage is problematic. It is quite common to get some sort of feedback of high voltage from the output side of the circuit to the input. Some units seem to do this when in perfect working order and others can develop it as a fault where transformer insulation breaks down.
Both of the above failures can be very serious for sensitive electronic equipment like computers and solar regulators. The best and safest way to power an electric fence is from a separate panel/battery/earth system preferably housed in a shed away from your house. A reasonably cheap and very functional system can be put together with a second hand solar panel (and if you've been using solar for a while you might well have a spare), a decent car battery (or that size of deep cycle battery), and the highest output 12V fence unit you can stretch to.
12V Emergency PumpWith the fire season approaching and many people now buying ‘back up’ water tanks with our increasing drought, I thought I'd share a few ideas with you.
An Emergency Pump on a Grid Powered House:
In the past year I have been receiving increasing numbers of inquiries from grid connected home owners about solar and 12 volt water pumps. These inquiries are coming as a result of a number of community concerns including:
1) The aerial footage of dozens of brick homes burned in the Canberra bush fires a couple of years ago next to swimming pools full of water created a lasting impression in some people’s memories. When there is fire there is a danger that the city water pressure or your own water pump could fail.
2) A few years ago some city Councils banned the use of water tanks. Now some of the same Councils are giving homeowners subsidies to install them! Some Councils have advised their rate payers that the days of being able to use town water for their gardens are gone forever. In some tank locations getting a plumber and an electrician to put in a 230V pump can be quite costly.
3) There are increasing concerns about the reliability of our grid supply which may be needed to supply household water requirements.
4) The provision of a pressurised emergency water supply by installing a header tank can be expensive or difficult on some properties.
So what are some of the possible solutions? Generally the ‘problem’ is to pressurise water from a ground mounted rainwater tank. In some cases the tank is near the 'grid'; in other cases it might be next to a shed or garage.
A battery charger powered pump would have one of our Flojet domestic pressure pumps connected to perhaps a car battery which is kept charged by a small automatic (regulated) battery charger. Even a car battery should power the smaller Flojet pump for several hours should the grid fail. This is long enough to provide domestic water for an emergency loss of power for at least a couple days. A larger deep cycle battery would be suggested if you experience frequent grid failures.
A solar powered battery pump might be the best option if the grid is a bit far away or if there are frequent or prolonged grid failures. If you are only going to use the pump for say an average of twenty minutes a day, a 5 Watt solar module might be large enough to do the job!
In all cases, you need to remember that wet lead acid batteries are potentially dangerous if not installed properly. They release explosive hydrogen gas when charging, contain acid, and the cabling should be fused to prevent fires in the event of an electrical fault. Contact our office for more detailed advice.
We have scheduled 2 courses prior to Christmas:
Weekend Course (for system owners) 13 & 14 November
Overseas Training Course starts 18 November This is a one month course designed primarily for overseas students. We only have 1-2 places left. See our website for more details.
Cheers from Dave and all the RPC crew.
Dave Lambert (Director)
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