PCB design for led bargraph battery monitor - Page 3 - Fuel Economy, Hypermiling, EcoModding News and Forum

Tweety · 12-09-2009, 05:31 PM

Plus we are going for low cost aren't we?

Tweety · 12-09-2009, 05:58 PM

I love optocouplers...

Especially cheap one's...

Now this should be bulletproof... Not even I could screw this one up...

dcb · 12-09-2009, 06:36 PM

I can't tell if there is a lower cost option for the opto, since we are just looking at a single tree in a forest here, but the opto should do it, same circuit as the original with an opto enable.

yah, the GND should be connected to batt neg? Don't want it to go to vehicle GND on accident.

The R7 looks strange though, like it is always "sorta" on.

Tweety · 12-09-2009, 07:06 PM

The GND in the schematic is internal, the only thing connected to anything is the 4 posts on the left hand side... Connecting to vehicle ground wouldn't really harm anything unless that is connected to pack ground... Otherwise it should be the same as negative on the 12V system...

The enable pins, two this time is +12V and ground in the 12V system...

R7 is a bypass... If you use the remote on feature you leave R7 out of the circuit, if you use it as a standalone, you stick a wire there and leave out R6 and the opto... It's an easy way to have one PCB for two functions...

The opto is about ~$0.5 in batches of more than 10 from my local supplier, so not too expensive... Dunno what you would pay/get... But it should be more than possible to find an equivalent cheap one...

dcb · 12-10-2009, 02:40 AM

Quote:

Originally Posted by Tweety

Connecting to vehicle ground wouldn't really harm anything unless that is connected to pack ground

yah it will, you really need to look at the bigger picture

mora · 12-10-2009, 10:06 AM

So there was a problem with transistor. Optos are even a bit cheaper here than transistors. And yes, at least I aim for going cheap.

Tweety · 12-10-2009, 10:42 AM

Quote:

Originally Posted by dcb

yah it will, you really need to look at the bigger picture

Dammit... I'm still thinking car = 12V...

Ok, taking a few steps back I get the picture... Now I'm gonna upgrade my 1n4001 diodes to atleast 1n4004's... should give me enough protection to realise I made a bo-bo before I let out the magic smoke...

Tweety · 12-10-2009, 10:45 AM

Quote:

Originally Posted by mora

So there was a problem with transistor. Optos are even a bit cheaper here than transistors. And yes, at least I aim for going cheap.

No, not really a problem... It's just that when using a transistor it would end up needing a few more components as well... And since an opto is atleast in the ballpark same cost and in the end doesn't need any more components to do the job... Well I adhere to the KISS principle...

MrOrange · 10-20-2011, 11:48 AM

Hey guys,

I've been looking for an LCD battery monitor display for quite a while now. It seems every time I find one, it was developed in 2008/9 and has since been abandoned. I have attempted multiple times to contact many manufactures with no replies. One such display is: www(dot)youtube(dot)com/redirect?q=http%3A%2F%2Fevie-systems.com%2Findex.php%3Fmain_page%3Dproduct_info %26cPath%3D44_48_49%26products_id%3D65&session_tok en=VARP0DJz2ydFO0eiQgzjVLNciTh8MTMxOTIwNzk1MkAxMzE 5MTIxNTUy

I am going to have 60 cells in my EV, so the available LED monitors while cool, aren't really practical. Does anyone have a lead on such a system? I have never worked with LCD's before so I know I cannot design one, but if someone here could I would be happy to throw some money behind them to assist development.

I think with today's systems and higher voltages this would be more in demand than it is. Surely it's going to be highly sought after in the coming years.. Or is there a system I've been unaware of at the present time?

Does anyone agree or am I crazy? Sorry to bump old thread, cannot make new post..

mora · 10-20-2011, 11:56 AM

I abandoned the idea of using this LCD monitor mainly because I abandoned Pb-batteries. Luckily I made only a few for testing purposes. They worked fine.

But I'd like to get similar monitoring system as you described. Small and simple bar display which doesn't show volts but a rising/lowering bar which is related to voltage level. One could easily tell which cell sags the most. I believe it could be a simple loop-style wiring with no spaghetti involved if using canbus. It could even be integrated into miniBMS or such system. Two wires running from module to other and only two wires running from pack to master module. No high voltage either.