Project Journals > Chris Olson
Battery Bank Status Meter
tomw:
I poked around their site and I could not figure out if I can put this 100+ feet from my battery bank? For in the house and my batteries are in the garage / office across the driveway. I have cat5 across for some metering and probably have a pair or more open for connecting this if it will do it over light wire. It claimed 12.5 Ma draw I think it was. I didn't see any connection diagram or discussion of wiring beyond a S model that you could switch off the LEDs.
Maybe one of the Midnite guys will chime in.
Tom
Watt:
--- Quote from: tomw on March 07, 2012, 11:45:12 pm ---I poked around their site and I could not figure out if I can put this 100+ feet from my battery bank? For in the house and my batteries are in the garage / office across the driveway. I have cat5 across for some metering and probably have a pair or more open for connecting this if it will do it over light wire. It claimed 12.5 Ma draw I think it was. I didn't see any connection diagram or discussion of wiring beyond a S model that you could switch off the LEDs.
Maybe one of the Midnite guys will chime in.
Tom
--- End quote ---
Tom, I would be glad to check the accuracy of this meter adding 100 feet of wire between it and my batteries. Could you let me know the size of wire you would like to test and I will have at it.
rossw:
--- Quote from: Watt on March 08, 2012, 12:12:47 am ---Tom, I would be glad to check the accuracy of this meter adding 100 feet of wire between it and my batteries. Could you let me know the size of wire you would like to test and I will have at it.
--- End quote ---
I think Tom said he had cat5 cable. That should be 24AWG conductors.
The 'bot says:
<RossBot> 24 AWG wire is 0.000317 square inches (0.204731 square mm, 0.510560mm dia), 81.961293 ohms per km
40 metres (130 feet - well, Tom did say "over 100 feet") = 80 metres total (40 out + 40 back) = 6.56 ohms.
Do you have a 10 ohm resistor handy? Sticking that in series with one lead would be the equivalent of close to 220 odd feet of cat5 cable (resistance wise anyway). If it works like that, it should be fine with anything less!
Oh, and:
<RossW> !ohmslaw 10r 12.5ma
<RossBot> 125.000 millivolts at 12.500 milliamps through 10.000 ohms for 1.562 milliwatts
So you won't need a power resistor. It should indicate about 0.125V low. Not sure if thats enough to worry about or not.
Watt:
--- Quote from: rossw on March 08, 2012, 12:37:43 am ---
--- Quote from: Watt on March 08, 2012, 12:12:47 am ---Tom, I would be glad to check the accuracy of this meter adding 100 feet of wire between it and my batteries. Could you let me know the size of wire you would like to test and I will have at it.
--- End quote ---
I think Tom said he had cat5 cable. That should be 24AWG conductors.
The 'bot says:
<RossBot> 24 AWG wire is 0.000317 square inches (0.204731 square mm, 0.510560mm dia), 81.961293 ohms per km
40 metres (130 feet - well, Tom did say "over 100 feet") = 80 metres total (40 out + 40 back) = 6.56 ohms.
Do you have a 10 ohm resistor handy? Sticking that in series with one lead would be the equivalent of close to 220 odd feet of cat5 cable (resistance wise anyway). If it works like that, it should be fine with anything less!
Oh, and:
<RossW> !ohmslaw 10r 12.5ma
<RossBot> 125.000 millivolts at 12.500 milliamps through 10.000 ohms for 1.562 milliwatts
So you won't need a power resistor. It should indicate about 0.125V low. Not sure if thats enough to worry about or not.
--- End quote ---
Yes, I missed that about Cat5 cable. Thanks Ross. Getting the egg off as I type. ;D I think I was thinking " Light " wire. I don't know either. :-[
Yes, I do have a 10ohm resistor. Which end goes where? ??? Just kidding.
ChrisOlson:
I was looking for the propaganda that came with that meter but can't find it. IIRC, it said that when the meter says 50% on a 24 volt system with lead/acid batteries (you have to set a jumper in there for the battery type), that the voltage at the bank will be about 24.25 volts. And it shows 100% when the bank is at 25.5 or above.
The wire going to the meter is about the size of the wire used in ethernet Cat 5 so I see no reason why it wouldn't work with a long run of Cat 5 wire on it. It'll have some voltage drop in the long wire, but it's no big deal if it shows 40% instead of 50%. After you get used to it and you know the meter is showing 50% when the bank is at 24.3 volts, or whatever, it still serves the same purpose - it's a simple glance at it and know right away where the bank is at.
If you get up in the morning and see it there on the kitchen wall and one of the red LED's is on, then you're getting low on power. If it's yellow or green life is good and might as well brew up a pot of java and worry about the power system later. And that's the idea of the meter, to my way of thinking. It's purpose is not to know that the bank voltage is 24.38547274648 volts and it's at exactly 53.57583% SOC. It's purpose is a simple device to show "yup, the system is working normally" or "damn - we got a problem" without having to go out to the utility room to ascertain that.
--
Chris
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