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Old 04-18-2016, 01:45 PM   #21
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QUOTE=pgandw;1167830]First, it doesn't matter where you measure the 12V system voltage.

Fred W
2014 Rockwood A122 A-frame
2008 Hyundai Entourage (minivan)
camping Colorado and adjacent states one weekend at a time
next week is 9 days for the Utah 5[/QUOTE]

Really? Put your batteries in storage mode (batteries disconnected) when stored and see what voltage reading you get from a volt meter that isn't connected, in some way, to the positive terminal of the battery. Isn't that the purpose for this exercise, to check battery voltage when in storage to see if charging should be done. Not necessarily a requirement to check battery condition if shore power is applied. It's just another convenience tool.
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Old 04-18-2016, 03:06 PM   #22
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Originally Posted by pmsherman View Post
I installed a meter similar to the DROK previously mentioned and wired it to the 2/0 lines to the battery that the dealer installed when I had an inverter installed. My meter is on a switch that has on-off-momentary on positions so it can be turned off when the unit is in storage. The meter light also serves as a night light when we're boondocking.

Phil
Till you mentioned the inverter I had completely forgot that my inverter can read the DC volts from my batteries. Of course I would need to go outside to read it. The VOM I wired into my switch panel I can read any time with a flip of a switch.

Jim
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Old 04-18-2016, 03:39 PM   #23
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Originally Posted by bubbles View Post
QUOTE=pgandw;1167830]First, it doesn't matter where you measure the 12V system voltage.

Really? Put your batteries in storage mode (batteries disconnected) when stored and see what voltage reading you get from a volt meter that isn't connected, in some way, to the positive terminal of the battery. Isn't that the purpose for this exercise, to check battery voltage when in storage to see if charging should be done. Not necessarily a requirement to check battery condition if shore power is applied. It's just another convenience tool.
The OP was asking a convenient place to put a permanent meter to monitor voltage in a Pop-Up camper. The OP wants to know the condition of her batteries while she is camping. The parasitic power draw of a non-high-wall PUP or A-frame is pretty small - on the order of 0.5 to 0.75 amps.

So a voltage measurement anywhere in the 12V system is going to give a pretty close approximation of battery voltage. The volt meter might read as much as 0.1 volts low because of existing small current draws, which is a good thing, as it will cause recharging to start a little sooner. It will be the same reading, whether at the battery posts or wired to a switch inside the camper.

If shore power is applied, the voltmeter will tell her whether or not the converter is working, and whether or not it has switched to trickle charge mode (can assume the batteries are fully charged at that point).

There is really little reason to measure the battery voltage while they are in storage - I plug my A-frame in at least once every 3 months to keep the batteries charged (via the converter). The rest of the time, the batteries are disconnected with a shut-off I installed.

If she wants to read the voltmeter when the PUP is folded down, it has to be mounted next to the door or somewhere outside (battery box is a good location).

After these discussions, installing a voltmeter in my A-frame is probably in my near future for the same reasons I have given the OP. I currently undo the battery box cover and measure with probes at the battery terminals with a portable meter - because that is the most convenient place to access the 12V system on my A-frame. Voltmeters are cheap and have reasonable utility, just like my wireless thermometer for the fridge (except for some high wall models, PUP and A-frame fridges are continuous run with no direct temp control).

Fred W
2014 Rockwood A122 A-frame
2008 Hyundai Entourage minivan
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Old 04-18-2016, 04:16 PM   #24
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Originally Posted by pgandw View Post
The OP was asking a convenient place to put a permanent meter to monitor voltage in a Pop-Up camper. The OP wants to know the condition of her batteries while she is camping. The parasitic power draw of a non-high-wall PUP or A-frame is pretty small - on the order of 0.5 to 0.75 amps.

So a voltage measurement anywhere in the 12V system is going to give a pretty close approximation of battery voltage. The volt meter might read as much as 0.1 volts low because of existing small current draws, which is a good thing, as it will cause recharging to start a little sooner. It will be the same reading, whether at the battery posts or wired to a switch inside the camper.

If shore power is applied, the voltmeter will tell her whether or not the converter is working, and whether or not it has switched to trickle charge mode (can assume the batteries are fully charged at that point).

There is really little reason to measure the battery voltage while they are in storage - I plug my A-frame in at least once every 3 months to keep the batteries charged (via the converter). The rest of the time, the batteries are disconnected with a shut-off I installed.

If she wants to read the voltmeter when the PUP is folded down, it has to be mounted next to the door or somewhere outside (battery box is a good location).

After these discussions, installing a voltmeter in my A-frame is probably in my near future for the same reasons I have given the OP. I currently undo the battery box cover and measure with probes at the battery terminals with a portable meter - because that is the most convenient place to access the 12V system on my A-frame. Voltmeters are cheap and have reasonable utility, just like my wireless thermometer for the fridge (except for some high wall models, PUP and A-frame fridges are continuous run with no direct temp control).

Fred W
2014 Rockwood A122 A-frame
2008 Hyundai Entourage minivan
If you use a meter and where you hook it up is just a mater of convenience to you. My dealer does a lot of boon docking. He saw how I hooked up mine and liked it. Did the same thing to his TT for the same reason, he hates those idiot lights.

Jim
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Old 04-18-2016, 06:26 PM   #25
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It does matter where you read volts; or at which point you monitor AH or watts in or out. If it did not matter then any gauge wire would work for anything. If the converter happens to be putting out 14.8v (which most won't) do you think you will have 14.8v at the batteries across 15' of #8 wire? Don't think so. If you only want a go or no go test almost where will work. And yes a factory converter could be good enough, if your style of camping has several days between trips; absolutely.
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Old 04-19-2016, 03:49 PM   #26
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It does matter where you read volts; or at which point you monitor AH or watts in or out. If it did not matter then any gauge wire would work for anything. If the converter happens to be putting out 14.8v (which most won't) do you think you will have 14.8v at the batteries across 15' of #8 wire? Don't think so. If you only want a go or no go test almost where will work. And yes a factory converter could be good enough, if your style of camping has several days between trips; absolutely.
WW
Again, we're talking a Pop-up with a 12ft box for the OP - not a 35ft TT. The combination converter/distribution panel is located near floor level under the sofa or a dinette seat or similar. The converter will be near the tongue, with maybe 6-8ft of #8 wire to the batteries. And it's only a 30 amp converter. The amount of time the converter will be above 10 amps is pretty small - two hours at most after plugging in, and that assumes batteries were down to 50% SOC. Without a significant charge current flowing (I don't feel like calculating voltage drops right now), the voltage at the battery will be the same as at the converter output, which will be the same as anywhere else in the 12V system.

Chances are the OP is not going to connect the voltmeter at the converter in any case - it will be awkward to use. An inside mount of the voltmeter will likely be tapping the stereo or night light circuits in the camper, where it will accurately read the battery voltage at any given time.


Time to recharge really only matters if you are using a generator to recharge. Plugged in to shore power, the stock converter is good enough. A more aggressive and/or larger converter may save an hour or two out of 12 hours at best. Solar re-charging time is dictated by panel output.

Fred W
2014 Rockwood A122 A-frame (also 12ft box)
2008 Hyundai Entourage minivan
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Old 04-20-2016, 10:14 AM   #27
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Originally Posted by WolfWhistle View Post
It does matter where you read volts; or at which point you monitor AH or watts in or out. If it did not matter then any gauge wire would work for anything. If the converter happens to be putting out 14.8v (which most won't) do you think you will have 14.8v at the batteries across 15' of #8 wire? Don't think so. If you only want a go or no go test almost where will work. And yes a factory converter could be good enough, if your style of camping has several days between trips; absolutely.
WW
I think you are getting voltage and amperage confused. The voltage is going to read the same any where in the OP's trailer. You become concerned with wire size when you are dealing with your load, in other words, amperage. I don't think there is a wire run long enough in a trailer that would be long enough to cause a concern with voltage drop. Take a look at the wire size on your meter. my good meter has 3 foot long leads and small wire size.
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Old 04-20-2016, 11:31 AM   #28
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The OP can install a meter anywhere but if it is battery that holds interest then it must be connected at the battery.

The meter has small leads because its resistance and load is tiny. But it causes voltage drop... very little but it does. Its impedance is small... or high.

A load, any load (resistive) causes a voltage drop (DC to keep it simple). It is ohms law. There is resistance in a wire, any wire. Add this resistance to that of powered devices and current increases. Batteries can't magically increase voltage to compensate; so voltage can only be less across a load. With a digital volt meter read your batteries (not being charged - resting) while doing that, turn on an appliance that offers a substantially load then look... tell me if the reading changes. Try it you'll be amazed.
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Old 04-20-2016, 11:54 AM   #29
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I made this for my unit. I spliced (with an in line fuse) into another system (electric awning) N.O. switch 12 volt wiring that comes directly off the battery because it was convenient for where I mounted the panel. Picked up ground from another switch. Panel is thin modeling plywood, the meter is cheap from ebay and the push button switch is cheap and small as well. I thought something like this is all the OP was looking for. Maybe not.
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Old 04-20-2016, 12:49 PM   #30
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I made this for my unit. I spliced (with an in line fuse) into another system (electric awning) N.O. switch 12 volt wiring that comes directly off the battery because it was convenient for where I mounted the panel. Picked up ground from another switch. Panel is thin modeling plywood, the meter is cheap from ebay and the push button switch is cheap and small as well. I thought something like this is all the OP was looking for. Maybe not.
Basically the same as I did only I used a cheap VOM and hooked up to the battery test button in my switch panel. Main purpose, check condition of my batteries when boon docking so I know when to charge them.

Jim
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Old 04-20-2016, 12:54 PM   #31
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The OP can install a meter anywhere but if it is battery that holds interest then it must be connected at the battery.

The meter has small leads because its resistance and load is tiny. But it causes voltage drop... very little but it does. Its impedance is small... or high.

A load, any load (resistive) causes a voltage drop (DC to keep it simple). It is ohms law. There is resistance in a wire, any wire. Add this resistance to that of powered devices and current increases. Batteries can't magically increase voltage to compensate; so voltage can only be less across a load. With a digital volt meter read your batteries (not being charged - resting) while doing that, turn on an appliance that offers a substantially load then look... tell me if the reading changes. Try it you'll be amazed.


WW
No, I won't be amazed. I know what will happen. We are getting way off topic though and not helping the OP at all now.

Jim
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Old 04-20-2016, 04:33 PM   #32
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The OP can install a meter anywhere but if it is battery that holds interest then it must be connected at the battery.
I think I understand the reasoning behind the disagreement now. You are envisioning measuring the current or AH from the battery - Trimetric or similar. In that case, a shunt (resistor) is placed in SERIES as close to the battery as possible to capture every bit of current flowing from the battery. The shunt is probably on the order of 0.005 ohms (must be accurately manufactured to get good readings) to keep the voltage drop across the shunt to a minimum. Even at that value shunt, it's easy to get a drop of 0.1 volts or more between converter and battery.

The OP is installing a voltmeter inside or outside her camper - which is a pop-up camper with limited 12V loading. The voltmeter, which is placed in parallel, not series, with the rest of the camper, has an internal resistance of 100K or better (usually 10M or better). The voltmeter's resistance - in parallel - would reduce the overall camper resistance in the 6th decimal place at worst. It's not going to be measurable or noticed.

If there is no shunt - OP was talking voltmeter, not Trimetric - then there is only the voltage drop in the camper wiring to make the voltage inside the camper different from the battery. A pop-up camper has minimal loads and minimal wire lengths compared to a 35ft travel trailer. You have a heater fan (4-5 amps) if in use, 2 inside LED lights (0.8 amps) if in use, an automotive stereo (unknown) if in use. The possible CPAP and heater use will be the only loads of concern, and the #8 wiring from battery to converter is not going to have any significant drop with 10 amps going through its 6-8ft length.

Hence my statement that it doesn't matter where the voltmeter is mounted or tapped in. It should be where ever the OP finds a mounting spot that is easy to read when she wants to check the battery voltage.

When camping with a CPAP, the recommendations are to wire into a 12V circuit like a cigarette lighter. Run the CPAP with the humidifying off. That will give you about 4 nights (no heater) of CPAP use without recharging and not running the dual golf cart batteries below 50%.

Fred W
2014 Rockwood A122 A-frame
2008 Hyundai Entourage minivan
camping Colorado and adjacent states one weekend at a time
trip to the Utah 5 begins Saturday
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Old 04-22-2016, 09:28 AM   #33
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Go small solar

With the price of batteries, it is worth protecting your investment. I tent camp in the winter hunting seasons. I had CF electric lights in the tent. I just ran them off the battery, and they would last 5 days, no problem. The problem was that I had to buy a new battery ever year or two. I finally got smart and added a small solar panel. A 10 watt panel will not overcharge a single battery, and doesn't need a charge controller. A 20 watt panel won't overcharge your dual battery setup. Mount it somewhere on the trailer, run the power to your battery, and you'll never have to worry about your batteries, except to check the water occasionally. In our houseboat, we have the old style volt meter, no light, just a dial gauge. If you read this blog, that gauge will all you need to know. I have the Trimetric, but that may be more than you need for your setup.

State of Charge: Your Camper/RV May Be Killing Your Battery Bank | PopUpBackpacker.com
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