DIY STATE-OF-CHARGE METER (SORTA)

[(unknown)]

Hello everyone.

First of all, I'm a 'long time listener, first time caller' and want to say this is a great site and I appreciate all the info here.  

When I originally saw this I was impressed with the simplicity.  I should probably say now that this is NOT my idea and I don't even have a battery bank to use this on to see how useful it might be or whether you would have to recalibrate it as the battery bank ages.  With that said here's the link to the guy's main page: (click 'ev gas gauge' at the bottom of the page to go to the meter set-up)

http://www.qsl.net/k5lxp/ev/evmain.html

This setup has limitations and is obviously for the bank as a whole not individual batteries but I think it is interesting for what it is.  I think his explanation is sufficient and I hope that someone may find it useful.  I did a search of the board & didn't find an equivalent circuit and I don't know if an easier/cheaper digital circuit exists or even if the modern inverters already provide an 'instantaneous' SOC reading or not.  

Until I can contribute something of my own I thought I would post this as a way to say hello with something more than just my hat in my hand.

Cheers!

[harrie]

Very interesting site, this is something I have always wanted to do, and it looks like he did a very nice job. I wish he would have given more information on the drive motor/motors? Anyway, welcome to the board, Harrie

[The Crazy Noob]

Very nice way to give a reference of the bank's capacity.

Above all, the meter just looks gorgeous!

[dinges]

Hello and welcome to the board.

I wouldn't want to call this instrument a 'state of charge' meter. It measures the voltage and the current of the battery. These are only roughly indicative of the state of charge of a battery.

As far as I know, only hydrometers provide a -real- indication of state of charge of a battery, by measuring the density of the electrolyte.

http://www.solener.com/pregunta_e.html

see question nr. 22.

The instrument that is described in the article is nothing more than a fancy way of having both a current and voltage measurement in the same instrument. No more, no less. Definitely not a SOC meter.

It's an interesting use of the meter movement of an old SWR meter though.

[(unknown)]

Hello and thanks for the welcomes.

I totally agree with Peter it's not a true SOC meter.  I pondered over how to word it and couldn't come up with a better name.  Kind of an at a glance indication of where your battery bank is compared to current load?  Hopefully, somebody here will be able to give it a more proper name.  I just liked the simplicity of it, but of course you will still need to use a hygrometer just as normal, sorry if I gave that impression.  

Thanks everybody.

Cheers!