A battery back-up siren is quite simply a siren with a battery integrated into it. Its purpose, in addition to making a noise when the car alarm is triggered, is to sound if the main vehicle battery is disconnected or if the siren is unplugged.
I’m going to run through how battery back-up sirens work and explain some of the different types we have in New Zealand, and review some of the most common sirens available.
Not all battery back-up sirens are equal
Obviously, you don’t want the siren to sound when the alarm is disarmed. There are times when the vehicle needs to have the battery disconnected or things unplugged, so having the siren going off with the alarm disarmed would not be good.
The siren and alarm system should be smart enough to allow this to happen. All decent alarm systems with battery back-up sirens produced after 1995 manage this by using a digital siren.
Outdated battery back-up sirens with override keys - Dumb sirens
Which battery back-up sirens should you avoid?
- If a siren has an override key, then it needs to be accessible.
- If it’s accessible, it can be disabled as quickly as disconnecting the battery.
- Result: It has no meaningful real world security over a standard siren and is far less easy to live with.
Cheap to make, but not effective
Battery back-up sirens with override keys got phased out in the UK in the last century, but are still common here in New Zealand and Australia.
The over-ride key simply disconnects the internal siren battery when turned to the off position, It’s a very crude outdated way to do things.
These ineffective sirens were sold as being 5 star rated and continue to be promoted even though the rating system was dropped back in 2012.
Digital sirens are the only battery back-up sirens I recommend
Digital sirens know if the alarm is armed or disarmed. They do not need to be turned on and off with a key before the battery can be disconnected.
This allows a good installer to place them in locations that are not easy to access, making them harder to defeat.
Autowatch 375800 battery back-up siren
Digital Siren (No override key)
The Autowatch 375800 siren is of the digital variety, hence it has no override key to worry about, and can be hidden for that extra level of protection. It has soft arm/disarm chirps or can be programmed to silent arming (actually, silent arming isn’t strictly correct as it gives a very discreet blip).
The 375800 siren works with the following Autowatch alarms:
Not Waterproof
The main thing that lets the Autowatch siren down is that it is not waterproof. The little red tag with Autowatch embossed into it seems unnecessary as it makes the siren easier to spot on a concealed installation.
AVS - Smart data back-up siren
How can a siren with an override key be smart?
It’s not smart. It is blatant misleading sales spin. It’s not uncommon for these sirens to fail. I expect they are designed with built-in obsolescence. The siren works with both the AVS S Series and the A Series of alarms. Once it fails, you’re forced to either replace the siren with another AVS siren or replace the entire alarm system.
What is the point of having a data siren with an override key?
From a security perspective, it is totally pointless. The AVS siren comes with a very flimsy bracket and can be ripped out of the engine bay in seconds.
AVS probably views it as a good money earner though. It is the most expensive siren to purchase, so it’s reasonable to assume AVS makes a healthy mark-up on it and they are highly likely to fail at some stage.
Poor battery pack – Not waterproof
From my experience, the battery pack inside the siren typically fails after about two years, or the siren gets water-ingress, causing the internal components to corrode.
Cobra 4310 siren
Digital and waterproof
The Cobra 4310 is a true digital battery back-up siren. It is extremely solid and better, still has a very high pitch sound. It is certainly the loudest and most attention grabbing of the brands on offer here. The other great thing with the Cobra siren is that the arm/disarm chirps can be adjusted in volume to suit the owner.
The Cobra siren is so advanced that it will even give a diagnostic warning if it has been tampered with!
It is also worth noting that the 4310 siren is waterproof. It has not been replaced by the 5375 siren, which is just as loud but is now smaller. Hence, why the 4310 no longs has a 10/10 rating.
The 4310 came with the following Cobra alarms:
Cyclops & Dynatron Siren
Less is more
The Cyclops battery back-up siren is another low quality siren with override keys. If you like the Cyclops alarm, then get the lower priced version with a standard siren and save some money.
I remember a time when installers would take these sirens apart, remove the lock from the siren, seal it with a grommet, extend the wires to the lock, and relocate the lock to inside the cabin of the vehicle so the siren could be hidden.
Looking back, it was time consuming faff and the cost of a better alarm would be better spent than all of the added labour!
This siren comes with the following Cyclops alarms:
Mongoose battery back-up siren
Poor siren lock is easy to pick
The Mongoose siren is another basic battery backup system with an override key. The lock on the M60G siren can be picked and turned off without the key, which is a worry!
Designed to be defeated
Mongoose sirens come with bullet connectors and labelled wiring. This means it is really easy to unplug the trigger wire and connect to the ground, which will silence the siren in seconds! The bullet connections really should be cut off and the wires soldered and taped, yet Mongoose fail to mention this in the installation manual.
Check out my Video of the Mongoose M60G in action here.
Mongoose are a brand I recommend avoiding. Read the following reviews for a deep dive into why they are so bad:
Vodafone Automotive 5365 Wireless Siren
Great for installers
The 5365 siren from Vodafone Automotive (previously called Cobra) is a wireless battery back-up siren. It still needs a power supply from the vehicle, but does not require a physical connection to the alarm module. This makes it much easier to install on some cars where running cables between the engine bay and cabin can be difficult.
One way communication
The alarm can command the siren to arm, disarm and trigger, but the siren can not communicate back to the alarm. This means if the siren is tampered with, it will trigger the siren but not activate the rest of the alarm. This YouTube Video explains it in detail. Hence why it only gets an 8/10 rating.
The 5365 is IPX5-rated, so it can handle some water.
Vodafone Automotive 5375 Wired Siren
My new favourite car alarm siren
The 5375 siren from Vodafone Automotive replaces the discontinued 4310, which has been my go-to siren for the past 2 decades.
It ticks all the same boxes as the 4310 with a couple of added improvements.
- It is smaller but still as loud.
- It comes with a 4.5 meter wiring loom, so I don’t have to extend the cables very often.
The 5375 is compatible with all of the alarms that came with the 4310 siren.
The 5375 is IPX7-rated, so it is waterproof and recommended for off-road vehicles.
