Battery based tank circuit (tested)

**Ricky327** · 01-04-2004, 05:52 PM

The diode design sounds cool. My concern would have been if i had substantially discharged my tank, I'd suck the juice required to bring the batteries to equilibrium out of the main battery, and not be able to crank. This obviously isn't a problem with a small battery.

The 0.8Ah Ive used is probably negligible to the car battery

quite simply, conect the tank to pin 87a, and 86 to the starter wire. This might eleviate some concerns about the relay not switching quickly enough- the relay for the starter is probably just as slow

Yes the hardest part is the ensure the backup is fully disconnected before the engine start cranking. And I guess one of the way to achieve this is to have an additional switch that get triggered as you turn the key to crank the engine...before it crank.

It seems easy but theres alot to think about to design a good tank circuit that will work for every setup.

**robiewp** · 01-04-2004, 05:54 PM

Originally Posted by mst

Maybe I am wrong but I am afraid to send unregulated 13,5 volt to the screen and the motherboard (the PW-70 does not regulate the 12 volt).
.....

The sproggy is the same price (with the free parts)but it is not small.
The best would be a Opus but they are expensive and big.

You're definitely NOT wrong to fear sending unregulated voltage to the screen and motherboard. Not only does the PW-70 not regulate the 12volt line, but under some circumstances it does not properly regulate the 3.3v or 5 when seeing 13.8! To say that I don't use the ITPS is not to say that I send unregulated voltage to the PW-70. I considered it as a possibility, but after some testing found that when 13.8v powered the PW-70, by whatever act of nature and god, the vt6103 chip (lan) was getting voltages outside of its tolerances. This was the only chip I checked, but I would not be suprised if there were more. Even if you're not noticing problems with unregulated current does not mean you arent' slowly killing your computer

I have the fine motor skills of crack fiend so I shy away from soldering intensive stuff, though i can manage most of the time (you do have to build the sproggy, right?)

**mst** · 01-04-2004, 05:55 PM

A few months ago I was nearly finished my setup for my "still under renovation" Golf GTI 1983 with a 16v engine with a laptop 266 Mhz, mainly for GPS,then I had the (mis)fortune to read about the Via Epia motherboards on the net and later I found the MP3car forum,it has been quite an expensive meeting,the laptop is dished,so is the car radio and it will take quiet a few months before the car is finished;but the carputer can do a lot more then an old laptop

**mst** · 01-04-2004, 05:58 PM

Originally Posted by robiewp

You're definitely NOT wrong to fear sending unregulated voltage to the screen and motherboard. Not only does the PW-70 not regulate the 12volt line, but under some circumstances it does not properly regulate the 3.3v or 5 when seeing 13.8! To say that I don't use the ITPS is not to say that I send unregulated voltage to the PW-70. I considered it as a possibility, but after some testing found that when 13.8v powered the PW-70, by whatever act of nature and god, the vt6103 chip (lan) was getting voltages outside of its tolerances. This was the only chip I checked, but I would not be suprised if there were more. Even if you're not noticing problems with unregulated current does not mean you arent' slowly killing your computer

I have the fine motor skills of crack fiend so I shy away from soldering intensive stuff, though i can manage most of the time (you do have to build the sproggy, right?)

Oh,I can solder it OK,but if it works after,that is the question

**robiewp** · 01-04-2004, 06:04 PM

Originally Posted by Ricky327

It seems easy but theres alot to think about to design a good tank circuit that will work for every setup.

I couldn't agree with you more. It's entirely a case by case basis thing with the type of design I was speaking of, and couldn't be readily generalized to, "put the + here and the - here". In my mind it's more advantageious, but then again all of my needs were in mind

Originally Posted by mst

A few months ago I was nearly finished my setup for my "still under renovation" Golf GTI 1983 with a 16v engine with a laptop 266 Mhz, mainly for GPS,then I had the (mis)fortune to read about the Via Epia motherboards on the net and later I found the MP3car forum,it has been quite an expensive meeting,the laptop is dished,so is the car radio and it will take quiet a few months before the car is finished;but the carputer can do a lot more then an old laptop

I've been almost done for 6 months! Really though, I'm almost done!

**mst** · 01-04-2004, 06:12 PM

Well If you continue to read this forum it might take more time,it is fantastic so many good ideas you can find to put in your car

**numberone** · 01-05-2004, 01:33 PM

Even with this improved setup I dont think its good enough for ITPS. The only way around the ITPS is to add a relay that short out the diode so no voltage is ever lost. Even with that zero voltage drop circuit, the ITPS minimum operating voltage of 13.3V is still pushing it to the limit.

As I can see your tank circuit doesn't provide any regulation. Could you suggest any itps free solution based on your circuit? I'm starting to hate my ITPS. IT SUCKS!

**robiewp** · 01-05-2004, 01:45 PM

regulation is too complicated for our simple minds

**Ricky327** · 01-05-2004, 01:58 PM

I guess you just want a regulated +12V for your PC? True the ITPS simply cant do this without the input being above +13.3V

Well the main problem is desiging a circuit that can supply +12V @ 5A or more with an operating voltage from 8-16V lets say. 8-16V supply range should survive a crank. It is possible and have been done before, I havnt looked deeply into it as I dont need one

Subtituting the LM1084 used in ITPS with a lower voltage drop regulator should help. But even then a zero voltage drop tank with a zero voltage drop linear regulator Ill say it can still be unreliable. The car voltage is just not high enough and tend to varies from 11.5V to 13.8V in normal operation. With a perfect setup 11.5V can still crash your PC.

As been mentioned in some thread before, the voltage can be stepped up by using a DC-DC laptop adaptor. This stepped up voltage of 14-15V is then fed into the ITPS. Of course the DC-DC adaptor must be able to work down to 8V...most only work down to 11V. There are some talk about a step up regulator that outputs 12V...I dont know if it does work well.

It is a very messy idea...check this out, I think its cool :

http://www.mp3car.com/vbulletin/show...097#post149097

or just use something else like the OPUS.

Sorry no direct solutions

**mst** · 01-06-2004, 03:00 AM

Hi
I looked at the schematic of the sproggy,as fare as I can see its takes the incoming voltage lowers it to 5 and 3,3 volt regulated and then takes some of the 5 v and raises it to 12 volt,this time regulated.I hope even if it gets only 8 volt it can still make the 5 volt.
Only problem is to get the max787's free,Farnell sells them for $18 plus 19% sales tax plus $7 transport (if they have them in stock),Well one day Maxim must catch up with there back orders.