>>>SIMPLE<<< 12V Battery Level Indicator

[PcHistorian]

wow, guys this is great info.
I would imagine that that indicator is meant for the deep cycle batteries, because the other batteries are not meant to be used for any long term discharge, they are designed to start something and then be instantly recharged. Any other use you are supposed to use the deep cycle. As for % discharge, on another thread here, they are mentioning that for the longest life of a deep charge battery, only go down to 50% charge before recharging. lastly golf cart batteries are the best deep cycle type out there.

I am thinking (as an electronics hobby-ist since 8 y/o) of using a zenier diode at like 9vdc (lets out 9 volts before it conducts) then put an LED (green) on it with a resistor. That should light for voltages over 10.5 or so. (keep shady) When that goes out, or to where I can's see it, charge. Then for charge and discharge indicators, get a high wattage resistor, and put an led in parallel with it, and have one for charge in and one for discharge - charge out, in series with the loads. You have to have about the voltage drop across the resistor, to get enough voltage to light the light. The brighter the light the brighter the charge or discharge. Once I get the specs I'll post them, this will be your $10 solution. Won't look as fancy, but you can put your lights where ever you want with second location repeaters, and not drill a hole in a fancy, expensive case. (besides I probably got all these parts in my piece parts bins. maybe put it in an altoids can and nail it to the wall... ;-)

I'm planning on putting instructions on the back of cabinet doors with clear, packaging tape. (I have a 120v and a separate 12v "closet.") Shouldn't destroy the surface and should be removable, but hold, (after I poly the back of the fiber board paneling I am using... :-)

[mckenney56]

Here's a "state of charge" chart. Just print it and tape it next to your battery.



I got this from this thread here: http://www.tnttt.com/viewtopic.php?f=30&t=11173

I use Gus' solution since I carry a multimeter for troubleshooting anyway.

<Chas>

This chart confirms what my dear old dad taught me. Let the battery rest as others have mentioned. Put a volt meter on it. If it is below 12 volts then charge it.

[crumbruiser]

OK, maybe I'm a moron but this is the 1 I'm going to use. I will put it somewhere around my radio.

Harbor Frieght=$5.99 with a coupon.
Frank

[PcHistorian]

that guage looks cool, I may get one for my little truck as well.
I'm trying to adapt a multi-led set for that purpose, but it was part of a power supply that bit the dust. next challenge is to make a circuit that fits the led arrangement. (even has a buzzer attached... :-)

[PcHistorian]

I may end up going with zenier diodes (fixed voltage electronics) and use some compare chips (cheap and easy) and bodge up a few square inches of circuit for the led's. put 11.5v as the alarm minimum and do 0.5v increments for the rest of the lights.

I do really like that simple led arrangement though. Maybe put the chart (laminated) on a string to a lighter type plug (from an ex-cell phone) with that device on the plug. Then, plug it in to check the state of the system.

here's a digital dc good to 200 v and 200 a, for $11. ($7 S&H) in fact I just ordered one. I may give up on the other thing idea. I have to make my own cotroll moduel, all I have are the LED's.
http://www.amazon.com/s?ie=UTF8&field-k ... ch-type=ss

I would hook it up on a push button switch to save even more energy (that of the readout) you could leave the shunt for the amperage in place.

I also have a full car meter, volts, amps, dwell, tac. but the amps doesn't seem to work (or I'm not drawing enough in testing to read.)

Although I like the relay cut out idea on that first led one. Radio shack sells 12vdc @ 30A contact relays. You could also get a relay from an old car, used for the horn or the power windows or power seats. Tough choice since relays use power, too. Maybe an SCR (silicon controlled rectifier) You'd need to press a button to activate it, but it would hold until the power cuts out on it and it takes almost no energy to hold the circuit. Or a power transistor. Tough choice. The fancy ones have that all figured out for you.

I'm quandering the chargers. Lug my "10 amp / automatic" car battery charger? Nice cuz it will auto charge to peak and keep the battery there but it doesn't fit in my wall cabinets. :-(
Or two amps (trickle charge) and go for the big charge from the tow vehicle by jumper cables or #10 cables run from the alternator...
(solar, wind, peltier, etc...)