What to consider before signing up for your security companies load shedding offers.
CURRENT
The first thing is the total current demand from your system.
Let’s look at an easy way to determine this.
Look at the capacity of the battery that has been supplied. Mostly you will find a 7AH or 8AH battery. In some instances you may have been provided with an 18AH battery.
Establish for how long the battery maintains your system when the power outs, and divide the capacity of the battery with the number of hours of operation maintained.
This rough calculation will give you an estimate of the Current in Amps that your system will draw per hour.
The general requirement is that the battery is provided to give you 4 hours of operation during a power outage. This assumes that the battery is in good condition, and that the supply company has properly matched the battery size to the current demand of the system. The battery should not be allowed to drain below 90% of it’s capacity.
A 7AH battery should then be capable of maintaing a 1.5Amp load for approximately 4 hours. This system will use 3Amp during a 2 hour period of load shedding.
CHARGE RATE
The average security charging system will recharge the battery at between 0.5 amp and 0.8 amp per hour. These systems are limited – since the battery should not be charged at more than 10% of it’s capacity.
In the above example, the 3 Amps drawn from the battery in 2 hours, will be replaced in approximately 4 hours. The battery will be recharged before the next bout of load shedding, and will still have a 3 Amp reserve if it isn’t -all is fine.
The problem is that very few installers even consider the current draw from the system. They simply provide the standard 7AH battery that comes in the kit.
Now when load shedding arrives, and the system doesn’t hold up – they tell you it’s because of loadshedding, and not due to poor design. Now they can up sell you on bigger batteries.
Just ask your installer to tell you the exact current demand of your system?
Very few alarm systems, and even fewer cctv systems will operate on 1.5Amp per hour. Most DVR’s will require more than 1.5Amp on their own.
MORE BATTERIES
So what is the solution?
We will sell you a battery backup kit and give you more battery they say.
So now we a 7AH battery in the panel and an 18AH battery in the backup unit. Let’s take for an example a system that draws a very conservative 3A per hour (6A for two hour load shedding).
This system is going to give you approximately 8 hours of standby time. The system will use 12 Amp in a day of double loadshedding and take 15 hours to replace that. Clearly at some stage you are left with a dead battery.
You can get a 100Amp Hour battery, and recharge it at 0.8Amp – but these batteries usually cost a few thousand rands, and eventually the math suggests that it too will end up dead after some time.
These type of systems charge at around 0.5 – 0.8Amp.
LITHIUM ION
What if you could safely charge the battery at a rate higher than 0.8Amp?
A lithium ion battery can be charged at around 30% of it’s capacity. You could add a 2.4 Amp charger to your 8AH lithium battery, and have it recharged in 4 hours – ready for the next bout of load shedding. (The existing backup pack is still only charging at 0.8A)
MAKING SURE
Before signing up for these load shedding deals – ask your technician what the total current draw is for the system that you need to power. Be concerned if he stutters or gives you a vague answer.
You might also question why a system that draws 2 Amp was initially provided with a 7AH battery?
Only when you are armed with this information – will you be able to commit to a solution that will keep your system running, safely through load shedding.
Speak to your Gensix representative about Lithium Ion batteries, chargers and lite and industrial level power ups stations. service@gensixtech.co.za
