How to install additional 12V battery to run security systems

[ElectricalNewbie]

Hello all, new here.

I’m searching for advice whilst brainstorming the idea of installing an additional 12v battery in my car to supply the security systems. Some context, the car in question is infamous for being easy to pinch as it is easy to access the battery, disconnect it without setting off any of the security systems as they have no internal backup battery, nor battery disconnect feature.

In short then, essentially what I am thinking is installing a second 12v battery that will be charged along with the normal battery, but only supply the security systems. That way the additional battery will always remain charged, but should the primary battery be disconnected and the rest of the vehicle be dead, the additional battery will continue providing power to the security systems.

Hopefully I have explained it clear enough. It seems simple enough but I haven’t a clue how to connect it up or what components are required. Nor do I know what the limitations of choice are for the additional battery. Preferably it can be much smaller and more compact as it is only to run the low current draw security systems and that will allow it to be tucked away discreetly.

Any help or advice is greatly appreciated.

 

[DPG]

If the thieves disconnect the battery, how do they start and run the car?

 

[plugsandsparks]

Hello all, new here.

I’m searching for advice whilst brainstorming the idea of installing an additional 12v battery in my car to supply the security systems. Some context, the car in question is infamous for being easy to pinch as it is easy to access the battery, disconnect it without setting off any of the security systems as they have no internal backup battery, nor battery disconnect feature.

In short then, essentially what I am thinking is installing a second 12v battery that will be charged along with the normal battery, but only supply the security systems. That way the additional battery will always remain charged, but should the primary battery be disconnected and the rest of the vehicle be dead, the additional battery will continue providing power to the security systems.

Hopefully I have explained it clear enough. It seems simple enough but I haven’t a clue how to connect it up or what components are required. Nor do I know what the limitations of choice are for the additional battery. Preferably it can be much smaller and more compact as it is only to run the low current draw security systems and that will allow it to be tucked away discreetly.

Any help or advice is greatly appreciated.

Its not straight forward as if effect in your scenario both batteries will be tied together through the charging cct. They would need to be isolated as different batteries at different states of charge when tied together can produce large currents. Usually in this scenario its easier to either have a larger battery or a second battery with a separate charging system, like plugging it into Battery charger at home.

 

[ElectricalNewbie]

If the thieves disconnect the battery, how do they start and run the car?

Thanks for your response. I suppose it would be in the instance of the vehicle being towed away or if the vehicle was a motorbike and lifted.

 

[DPG]

Thanks for your response. I suppose it would be in the instance of the vehicle being towed away or if the vehicle was a motorbike and lifted.

If they lift a motorbike they don't care about the alarm. It will be a battery powered angle grinder to the security chain, and then they lift it straight into the transit van. Probably all done in about 30 seconds.

 

[ElectricalNewbie]

Its not straight forward as if effect in your scenario both batteries will be tied together through the charging cct. They would need to be isolated as different batteries at different states of charge when tied together can produce large currents. Usually in this scenario its easier to either have a larger battery or a second battery with a separate charging system, like plugging it into Battery charger at home.

Would a voltage sensing relay do the trick?

 

[UNG]

I would go down the route of a split charge system for a second battery and add an additional 3 party security / tracking / geofencing system to backup the manufacturers security fed from the second battery

 

[ElectricalNewbie]

I would go down the route of a split charge system for a second battery and add an additional 3 party security / tracking / geofencing system to backup the manufacturers security fed from the second battery

Thanks for your response, this sound feasible. Would you be able to explain in a little bit more depth roughly what components would be required and how they would be connected? From a little bit of reading I’m thinking using a VSR to connect the second battery and connect the additional security direct to the second battery. Does that sound correct?

 

[UNG]

You would need to work out what extra security equipment you are going to use and then find a battery or batteries that can be hidden within the vehicle and supply that load for upto a few days or possibly a couple of weeks it may also be worth installing a battery monitor that can report the battery status when getting to a critical voltage. A VSR works in a similar way to a split charge setup but is easier to wire

 

[DPG]

Is it really such a big problem with these cars? I mean the fact that they will not be able to start them/run them and will probably need to trailer them away. Most criminals now either clone the keys or steal them from the house.

 

[ElectricalNewbie]

You would need to work out what extra security equipment you are going to use and then find a battery or batteries that can be hidden within the vehicle and supply that load for upto a few days or possibly a couple of weeks it may also be worth installing a battery monitor that can report the battery status when getting to a critical voltage. A VSR works in a similar way to a split charge setup but is easier to wire

Thanks, I’ve looked in to the prospect of adding a tracker. The FMT100 looks simple and acceptable. On the manufacturers website it offers the information below on consumption. Based on this, if I were to use a small, compact motorcycle 12v battery of say 6Ah, connected via a VSR, does that sound a sensible setup?

Power consumption

At 12V < 1.47 mA (Ultra Deep Sleep) At 12V < 3.21 mA (Deep Sleep) At 12V < 3.75 mA (Online Sleep) At 12V < 5.48 mA (GPS Sleep) At 12V < 24.41 mA (nominal)

 

[plugsandsparks]

Thanks for your response, this sound feasible. Would you be able to explain in a little bit more depth roughly what components would be required and how they would be connected? From a little bit of reading I’m thinking using a VSR to connect the second battery and connect the additional security direct to the second battery. Does that sound correct?

Post up the product you have in mind and a wiring diagram, can comment then

 

[ElectricalNewbie]

Post up the product you have in mind and a wiring diagram, can comment then

This is the tracker:

FMT100 - 2G Bluetooth Insurance GPS Tracker | Teltonika Telematics

2G Bluetooth easy mounting GPS tracker FMT100 with precise crash detector for UBI and SPECIAL fleet management applications

teltonika-gps.com

This is the VSR:

12V Voltage Sensitive Relay - 140A | 072733 Durite - Leaders in Vehicle Safety & Auto Electrical Parts | Durite.co.uk

Product Description and Specification for 12V Voltage Sensitive Relay - 140A | 072733

www.durite.co.uk

And this is the sort of battery I was considering:

12V 7Ah Toy Car Battery

High performance mobility scooter and wheelchair batteries at low prices. Designed to cope with modern day demands. Also Ideal for other traction applications like toy cars and electric motors. Other references: FR2:LB352623, 6 DZM 7, 6DZM7, DJW127, UL7-12, DJW12-8HD, DMU12-7.6, DMU12-8...

www.tayna.co.uk

And this very simple diagram I’ve pinched off of the internet was my plan. Connecting the VSR where is says battery isolator and the tracker where it says amplifier. With an inline fuse either side of the VSR. What do you reckon?

 

[plugsandsparks]

Like it, only issue i can see is how many days you need out of it. I see one week in winter probably maybe 10 days in Summer.

 

[ElectricalNewbie]

Like it, only issue i can see is how many days you need out of it. I see one week in winter probably maybe 10 days in Summer.

Thanks, really appreciate your help. I may look at alternative batteries of a similar size but with a greater Ah rating for the reason you state.