[Android Head-Units] kaween:
Generic tip to speed up boot time in real life use

Hello.

I just wanted to share this little tip with you guys : it's not limited to use with the S150 device, I can imagine a wide range of devices and uses for this idea, you yourself must decide if it's of any use to you personally.

Given : many car makers have an electricial or even mechanical interruption of the powerline to "less than needed" systems that kick in during cranking the engine. In short : if your car stereo resets of looses power during the start process of your engine, and you dislike that, just read on.

Now in my experience, there are 2 main reasons for headunits rebooting during crank :

1) the interruption of the powerline during crank, put in place by the manufacturer to Ensure maximum power for your car's start procedure.

2) headunits that will reset when their minimum power level is met or drops below that.

Especially with Android ect ect units, this can under circumstance mean you will wait an extra 10 or 15 seconds till your radio is usable. If you've got one of these "retractable screen 1 din units", this issue is even worse as the unit will pull back the screen the moment the voltage drops below critical minimum.

You CAN try to solve this by hooking your car radio to the 12V constant : sure, the radio will play now regardless of having put on ignition, on the other hand if you forget to switch the radio off, you will have a flat battery by the next morning (trust me, I know. :eek: ). And if your headunit is one of these "extra picky my voltage can not drop below 11.5V at any time" thingies, your headunit will STILL reset during crank even when you've connected that radio straight to the battery.

There are several ways to solve this, I've build a couple of them myself, but none of the solutions is as good as this one in my opinion.

Have a look at this : http://www.mini-box.com/picoUPS-100-12V-DC-micro-UPS-system-battery-backup-system.

What you need :

1) this tiny PCB (5x3 cm approx)

2) a sealed lead battery, you can start at 2.6Ah which is pretty much a very small battery, but I would recommend 7Ah or better for reasons I explain later.

The only thing you need to do is to connect the main battery to the input part of this PCB ("V In"), the PCB to the "extra Battery" ("Battery") and the Radio Power Circuit to the output of this PCB ("V Out")

Once you've done that, the effect will be that :

1) your headunit will become totally independant of your mains battery, as long as there's juice in the backup battery.

2) your headunit can NOT drain your main battery empty, as the PicoUPS will only charge the backup battery when the car's voltage goes above 13.2 V (in other words, when the engine of the car is running and your alternator is charging the battery circuit)

3) your headunit will be able to be operated even without a key in the ignition, as the PCB will switch automatically from main to backup battery depending on what input gives the highest voltage (but as said, it will refuse to charge the extra battery when the main battery drops below 13V thus protecting your main battery from being drained by a headunit you forgot to switch off). This is ideal when you've got kids in the car and you want to keep the radio playing, but you don't like the idea to leave them alone in the car with the key in the ignition)

4) even if your headunit reboots because the voltage drops below critical value during crank, the extra battery will avoid that unit to reboot as the ups switches from mains to backup in a timeframe of 100ns.

In other words, you can step into your car, first thing you do is you switch on your headunit, then you put the key in ignition, fasten your safety belt, ect ect .... and you will know your headunit will NOT reboot when you start that engine, in effect your headunit will be operational by the time you're ready to drive. And you know you'll be able to use that radio when the engine is off, and it will never drain your main battery empty.

I've been using several "power tamer"-like devices in my cars so far, but none of them ever worked this good before, and it requires very little to no technical knowledge to pull it off.

Maybe someone has some use for this.

PS : in terms of usable battery :

A 2.6Ah will support the S150 for approx 1 hour of play, independant of the main battery.

A 7Ah will do that .... +/- 3 hours

A 17Ah .... well I'm still testing that. :)