Continous power supply 5V of anti-theft system from battery, even with the engine off

[OscarA]

I have a Cube wit Active Line Plus, and I want to put an anti-theft system with motion alarm and GPS tracking. The system is charged by standard USB (5V)
I want to power the system directly from the battery for 3 reasons:
- Maximum autonomy
- I want to hide and mechanically fix the equipment, so its removal to charge will be annoying.
- Comfortability and easy of use, and always charged.
I know the 2 sockets for 6V to power the lights, but they cut the power when the engine is off.
I found a DC converter Input: 5V-40V / Output 5V 3A (able as a USB charger), and I want to connect directly to the battery.
--> My question: Do you know where can I connect? Any "prepared" connexion point? or any point "easy to adapt"?
Many thanks
OscarA

 

[vfr400]

40v isn't enough. You need to go higher. This one is 50v
https://www.ebay.co.uk/itm/DC-DC-4-5-55v-to-3-3v-50v-5v-9v-12v-24v-Buck-Step-down-Regulator-Converter-Board/252510783885?hash=item3acad0c98d:g:QzAAAOSwbiFZRJBVYou have to be careful with cheap buck converters, if they blow, they dump the high-side viltage into whatever is connected. It's probably a good idea to go for one with plenty of headroom for the current.

 

[OscarA]

Hi vfr400,
Many thanks for your answer. Regarding the buck, I'v found these two, that I liked for the tension and waterproof.
1)www.aliexpress.com/item/4000098833104.html?spm=a2g0o.productlist.0.0.1199180f78BqC3&algo_pvid=04684bf9-d12e-4063-a8f6-d293c071adb1&algo_expid=04684bf9-d12e-4063-a8f6-d293c071adb1-14&btsid=51efd833-9668-4097-9fcb-fbdedcdec5a7&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_53
2)https://www.aliexpress.com/item/32962819560.html?spm=a2g0o.productlist.0.0.1199180f78BqC3&algo_pvid=04684bf9-d12e-4063-a8f6-d293c071adb1&algo_expid=04684bf9-d12e-4063-a8f6-d293c071adb1-29&btsid=51efd833-9668-4097-9fcb-fbdedcdec5a7&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_53
I wrote 5V-40V because I think that the battery voltage is 36V, but in fact they are 10V-60V and 7V-50V.
Why to you say that 50V are needed if the battery voltage is 36V?On the other hand, do yo have any suggestion for the connexion point?

 

[Benjahmin]

He's saying 50v because a fully charged 36v battery is actually 41.5 - 42v. 50v gives you headroom, similarly with the current rating.

 

[Deleted member 25121]

You'll need to watch the current drain. A 500Wh 36V battery can provide a nominal 14Ah and it would be flattened in a week if the current drawn by the voltage converter was just 83mA.
The first converter you linked to:
www.aliexpress.com/item/4000098833104.html?spm=a2g0o.productlist.0.0.1199180f78BqC3&algo_pvid=04684bf9-d12e-4063-a8f6-d293c071adb1&algo_expid=04684bf9-d12e-4063-a8f6-d293c071adb1-14&btsid=51efd833-9668-4097-9fcb-fbdedcdec5a7&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_53
quotes a "Static power: <10MA " which is presumably means the residual current is 10mA. Taking this and the quoted effieiency of 90% into account I calculate that if your alarm drew 500mA at 5V it would flatten your 36V battery in a week . Now 500mA is a lot but I think it would be worth measuring the current drawn by your alarm, just in case it remains high even when the alarm is on standby.

 

[OscarA]

Hi Benjahmin, now I understand why 40V isn't enough. Thanks!
Hi biker99, I totally agree with you, the consumption of the anti-theft equipment must be controlled.
So I put a switch to cut its consumption. It only consumes when I leave the bike in a "risky" place, I turn off the system and activate the alarm. It is usually for few hours and I don't think the battery would be flattened.
On the other hand, in case of theft, the system has to send the GPS position, how long? until I catch the thief or the thief disassemble equipment and battery, XD. Thanks
And going to the connection point giving continous power (even with the motor off), I found this picture. Someone konws what are each connector?
I'm not sure, but maybe: 1+2= Speed sensor / 3+4+5+6= Display / 7+8 and 9+10 = front and rear light / 11+12+13+14= Battery ?


So, if no more connectors are there, no "prepared" point can be used! In this case is necessary to "adapt" one of the connectors. The Display connector (I imagine with very low power just to activate signal?) I supose that the 4-pins display connector should be 2 for power and 2 for data. The battery connector is my candidate, connecting in a point beetween the battery and the motor, with a shortcircuit protection. Similar to this but with a shortcircuit protection:

My question: Is it a good idea? Any better idea? Or is a crazy and dangerous idea and I need to install a separated battery for the alarm powered by the light connector and charged when motor is ON?

 

[Deleted member 25121]

I can't answer your last questions but thought this might give you some ideas:

I have a GPS tracking system that's hidden inside the frame of a Bosch powered ebike. It has its own small battery that's charged up then the bike is turned on and when the bike is turned off and stationary it more or less turns itself off and its battery will last for a couple of weeks in that state. If the bike is moved when its power is off a motion detector in the tracking system turns it on and it will broadcast its position via a mobile phone network, the battery will last for about 30 minutes when its active in this way. If the movement stops the tracker will turn itself off in 5 minutes or so.
The tracking information is sent to a server run by the company that makes the product and there's a great phone app that I use to see on a map where the tracker was last located and the state of charge of its battery. I think the company will charge around £5 a year for this service, I haven't needed to renew it yet.

The system is very expensive at £200 but its great to have for peace of mind:

Just a moment...