Cheap battery saver module?

**fixumdude** · 03-02-2005, 06:38 PM

My friend has designed a very simple module to shut off everything pluged into my battery when it drops below 10.5V to save some battery power for starting the truck. My PC board power supply does this automatically, but not my monitor or my GPS module...this is for when the truck is off for a few days.

Would there be any interest in these if they were cheap enough (i.e. less than $10-$15) or is there already a cheap solution out there that I just missed in my searches?

They would have two sets of contacts. Connect one set to constant power and ground and power your devices off the other set of contacts.

Any feedback and/or suggestions would be appreciated.

Mike

**MSUC5Vette** · 03-08-2005, 07:13 PM

I would be interested.

How much current can be passed through it, and how much current does it draw?

**fixumdude** · 03-09-2005, 10:24 AM

MSUC5Vette,

I'll have to ask my engineer friend when he gets to work. I think he said it would supply as much current as the relay would handle so I would think we could get one that could handle almost any power needs. As far as how much current it draws we will have to measure it and see, I don't think it's much...we're just testing the circuit right now, but it worked like a charm. I'll post more when he gets in.

Mike

**fixumdude** · 03-09-2005, 06:10 PM

Ok, we tested the circuit this afternoon. With the relay we have it was pulling less than 7 milliamps in the cutoff mode and a little less than 100 milliamps while driving the relay. The realys we have are rated at 30 Amps @ 30 Volts so they should be able to switch a little more than 30 Amps @ 12 Volts.

I'm making mine up this week and will post some pics when it's done. We have it set to cut off at 10.5 volts right now, but that can be adjusted if necessary.

**zPilott** · 03-09-2005, 07:12 PM

I am also very interested.

**rotarypower101** · 03-09-2005, 07:41 PM

Interest here as well, my priority start took a dump, and it had only actually been used once before it somehow broke and the warranty had ran out already.

Take some pics of the setup.

And if possible you should make it have a bypass that can run power to the stereo so it can keep its settings while power is cut off. I hated that omission on the priority start. The amount of power used to keep the memory is not going to be a deciding factor if the car will start or not.

**execute** · 03-10-2005, 02:58 AM

this is very interesting, but would this abruptly cut the power right away without any warning?

if you had a way to make it integrate to the serial port, by just grounding 2 pins (forgot which pins and i'm not an expert so i might be using wrong terms or refering to different things) so that it can send a signal to the pc or something, i've read this here. Maybe just send the signal and delay the cut off... also, is it possible to change the battery charge cut off?

then again, that's almost like an existing module now is it

but this is all good, i'm interested if the price is right

**fixumdude** · 03-10-2005, 08:25 AM

execute,

Yes this will just cut off the power. My power supply already sends a shutdown signal to the PC when I turn the truck off. This is just a cheap backup measure to save some battery power at all costs...after I replaced my battery last week

The cutoff is adjustable...what voltage do you think would be the best cutoff point?

**Chairboy** · 03-10-2005, 11:17 AM

Why not power your GPS and monitor from your power supply, especially if your p/s already does the shutdown?

**fixumdude** · 03-10-2005, 11:55 AM

I think my M1-ATX power supply may already pushing the limits with 2 laptop hard drives, a CD/DVD drive and an occasional pen drive, etc...I don't want to mess it up by trying to run too many things from it. How much can you safely run with a 90 Watt power supply?