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Topic: dual system voltmeter mod for <$10 :) (Read 717 times) previous topic - next topic

dual system voltmeter mod for <$10 :)

If you do any boondocking you often find yourself turning on the CRT on your dashboard just to check the voltage of your coach batteries. There's a voltmeter already on the dashboard but it only tells you the voltage of the cranking battery, and only when the ignition key is turned on. Go to an auto parts store and get a double throw single pole switch. Connect the existing voltmeter to the switch's center terminal. Connect the coach battery to one of the switch's outside terminals and the cranking battery to the other outside terminal. Now the existing voltmeter will tell you the voltage of either battery with a flip of the switch, even when the ignition is off. When the switch is in the center position the voltmeter is off... If you don't understand what I wrote then it's best to leave it alone, but for those of you who do understand here's a simple but useful modification that costs less than $10! :)
Scott Cook
1991 U300 36' 6V92TA
Old Town Penobscot 16
1984 Honda VF1100C (V65 Magna)

Re: dual system voltmeter mod for <$10 :)

Reply #1 –
Scot, I like the idea of using the crt up front but mine uses too much juice. I put a digital in the lighter socket for the engine battery. You gave me an idea, to put another socket fir the coach right beside it-thanks ^.^d

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My advice and experiences are Free, you decide if they are worth anything .

John - driving Old Faithful
1994 U280 GV
C8.3, Banks, Pacbrake, 900 watts, Resonator, XLHD tow dolly
Retired Army Warrant Officer

Life is what you make of it - if it is lemons, make lemonade!
Former Coaches:
1988 GV 40' ORED 300HP CAT - 9 years
1990 Winnebago LeSharo - 3 years
2000 Newmar London Aire - 3 years (#18 of 23 produced)

Re: dual system voltmeter mod for <$10 :)

Reply #2 –
Under the dash on the firewall of the 280 are a row of relays with red wires going to them. One is from the coach batteries. I put a cigarette lighter extension with alligator clamps on that one, ran it outside the dash and plugged in one of those $2.80 digital voltmeters and another one into the cigarette lighter socket itself. I monitor both voltages all the time without having to get out of my chair.
1994 U280, Build 4490
Deming, NM.

Re: dual system voltmeter mod for <$10 :)

Reply #3 –
Not sure when they did this, but on mine there are two 12v "lighter sockets" right by the CRT on the dash. One is connected to the house batteries, the other is connected to the engine batteries.
1998 U270 34'

Re: dual system voltmeter mod for <$10 :)

Reply #4 –
On our '93 U225 there is a coach cigarette lighter plug-in on the co-pilot side but hidden under the glove box (left of the glove box and right of the center console/table). It's vertical (you plug in  from the bottom). I found it by accident when I was working on the co-pilot's chair and happened to glance up.

Craig
1993 U225 36' Unihome GV with PACBRAKE exhaust retarder, Banks Stinger and Solar Panels.
Toad: 1999 Jeep Wrangler 2-door soft-top.

"No one has ever had to evacuate a city because the solar panels broke."

Re: dual system voltmeter mod for <$10 :)

Reply #5 –
Quote from: krush –
On mine there are two 12v "lighter sockets" right by the CRT on the dash. One is connected to the house batteries, the other is connected to the engine batteries.

On mine, the upper one is labeled "Aux Power" and the lower one houses the cigarette lighter.
 
Do you know which one hooks to which battery?
 
Thanks,
 
Trent
Trent and Jean Eyler
2000  U295  4003  WTFE  ISC  350
Build#5603 MC#17385

Re: dual system voltmeter mod for <$10 :)

Reply #6 –
Dash is engine, side panel is house. Digital plugin voltmeters are only a couple of bucks each delivered off ebay.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: dual system voltmeter mod for <$10 :)

Reply #7 –
Here are the voltmeters I installed in ours. You can also see the plug-in voltmeter at the bottom of the photo. Second photo is the voltage at the batteries. OEM dash analog voltmeter is just a ballpark reading. Get digital voltmeter source from your schematic matching wire codes with schematic codes. The hardwired voltmeters are about $8 delivered off ebay source. Make sure they the display is powered off 12V as some are 5V. Also, you need a switch to be able to turn them off. I just used one of the old CRT switches.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: dual system voltmeter mod for <$10 :)

Reply #8 –
I only have one cigarette lighter socket on the dashboard and I use it to power my computer with a 12 volt DC power supply. I changed the wiring so the cigarette lighter socket is powered by the coach battery. It used to be powered by the cranking battery. I already have a voltmeter in the dashboard so I thought I'd continue using it instead of installing another voltmeter or another cigarette lighter. With a flip of the switch I can compare the voltage of the two systems on the same meter. The single pole double throw switch actually cost less than six dollars with sales tax included. I rounded up to <$10 to cover the connectors and tiny bit of wire I used. I thought about this modification a long time before I did it... basically every time I turned on my CRT monitor to check the voltage of the coach batteries. :)
Scott Cook
1991 U300 36' 6V92TA
Old Town Penobscot 16
1984 Honda VF1100C (V65 Magna)

Re: dual system voltmeter mod for <$10 :)

Reply #9 –
I installed a Trimetric 2025RV battery system monitor that tells me the voltage for both banks as well as power in and power out. About $150 (although Amazon doesn't seem to be carrying it any longer). Originally I bought this as a way to measure how much solar I'd need for our usage but it works so well that I'd recommend it for anyone who has an RV and a 12vdc system; especially one with two separate isolated battery banks. And if you boondock or drycamp something like this is really valuable as it will tell you the percentage of charge left in your house battery bank and the voltage in the start bank.

I have ours mounted right next to the entrance just below the old shore power voltmeter.

And, yes, I know it costs more than $10 but it tells me so much more than just a meter. :D

Craig
1993 U225 36' Unihome GV with PACBRAKE exhaust retarder, Banks Stinger and Solar Panels.
Toad: 1999 Jeep Wrangler 2-door soft-top.

"No one has ever had to evacuate a city because the solar panels broke."

Re: dual system voltmeter mod for <$10 :)

Reply #10 –
The only thing I need to know is the voltage of both systems. I have no idea what I'd do with the other information. The voltage is the determining factor for when I need to start the genset and charge the batteries. I'm sure some readers on this forum spent a lot more than $150 on battery monitors... I'm NOT one of them... ;D
Scott Cook
1991 U300 36' 6V92TA
Old Town Penobscot 16
1984 Honda VF1100C (V65 Magna)

Re: dual system voltmeter mod for <$10 :)

Reply #11 –
Quote from: RRadio –
The only thing I need to know is the voltage of both systems. I have no idea what I'd do with the other information. The voltage is the determining factor for when I need to start the genset and charge the batteries. I'm sure some readers on this forum spent a lot more than $150 on battery monitors... I'm NOT one of them... ;D

Knowing just the voltage doesn't tell the whole story. Perhaps there is a big current load going on (water pump, furnace fan(s), etc.) that can (and will) drop the battery voltage reading but not necessarily indicate that it's time to run the generator.

The Trimetric tells you that actual current draw on that battery bank as well as voltage.

Craig
1993 U225 36' Unihome GV with PACBRAKE exhaust retarder, Banks Stinger and Solar Panels.
Toad: 1999 Jeep Wrangler 2-door soft-top.

"No one has ever had to evacuate a city because the solar panels broke."

Re: dual system voltmeter mod for <$10 :)

Reply #12 –
Quote from: TulsaTrent –

On mine, the upper one is labeled "Aux Power" and the lower one houses the cigarette lighter.
 
Do you know which one hooks to which battery?
 
Thanks,
 
Trent

Trent, the one labeled AUX power goes to house batteries on my FT (it has a little rubber cover on it). The unlabeled one had a cig lighter in it, and goes to engine batteries.

Another way to double check: plug something in to the "AUX" one, and turn off the 12v master power with the switch at the doorway. This shuts off almost everything running off the house batteries, including the dash power outlet---well at least it did on mine.
1998 U270 34'

Re: dual system voltmeter mod for <$10 :)

Reply #13 –
I don't check the voltage during a large current load. I never have a large current load anyway, it's usually just my laptop computer running off a 12 volt DC power supply. I always check the voltage when the batteries have been at rest a while, so I get an accurate reading. Now I can compare the voltage of the coach batteries with the cranking battery on the same voltmeter for an even better idea of what the reading should be... Sorry, but I'm never gonna spend $150 when I only need a voltmeter. I've got so many places I wanna go and sooo much diesel to buy! :)
Scott Cook
1991 U300 36' 6V92TA
Old Town Penobscot 16
1984 Honda VF1100C (V65 Magna)

Re: dual system voltmeter mod for <$10 :)

Reply #14 –
The Trimetric also shows the State of Charge of your batteries.  Takes any guess work out of knowing how much juice is left.
Scott & Carol Seibert
2001 42' double slide U320 - Sold
Previous - 2002 36' U320
 

Re: dual system voltmeter mod for <$10 :)

Reply #15 –
Yes, that's what a voltmeter does... There was a basic battery course posted on this forum about a week ago that explains how to check the state of charge of your battery with a voltmeter or by testing the specific gravity.
Scott Cook
1991 U300 36' 6V92TA
Old Town Penobscot 16
1984 Honda VF1100C (V65 Magna)