Battery charging questions - Page 6 - Fiberglass RV


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Old 11-13-2013, 02:48 PM   #71
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Originally Posted by Paul Braun View Post
If I may expand on some of your observations. First, I believe the panels put out considerable more that you realize, the usual voltage on a 75 watt panel is up to 18 volts. Since the controller is dropping the voltage between the solar panel and the battery from 18 volts to 13.4 the gauge of wire is not critical. I run over 100 feet using 14 gauge and I am positive the controller is still reducing the volts. If you run the resistance calculations you do not loose enough to make a difference.

The controller should be mounted as close to the battery as possible and the gauge wire here may need your attention. However, the inexpensive controllers only have 16 gauge on the output side so it may not make sense to go with anything larger.
Paul,
If you are using a 100' extension between a panel and controller, that is 200' of 14 gauge wire in the circuit. Probably about 5 volt loss if the panel put out 5 amps. Even a 50' extension costs 2.5v. Maybe it works, but I would want bigger wire.
My controller would need to be mounted inside the front closet, or outside in a WP enclosure with air vents to be near the battery. Neither are particularly ideal. Thanks for your input.
Russ
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Old 11-13-2013, 05:03 PM   #72
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Originally Posted by ruscal View Post
Paul,
If you are using a 100' extension between a panel and controller, that is 200' of 14 gauge wire in the circuit. Probably about 5 volt loss if the panel put out 5 amps. Even a 50' extension costs 2.5v. Maybe it works, but I would want bigger wire.
My controller would need to be mounted inside the front closet, or outside in a WP enclosure with air vents to be near the battery. Neither are particularly ideal. Thanks for your input.
Russ
You're about 4x too high.
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Old 11-13-2013, 05:14 PM   #73
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Originally Posted by ruscal View Post
My 2003 16' Scamp has an American brand converter, and a lead acid Costco RV 12v battery. I have installed a Trimetric monitor to see what is going on when charging and monitor power usage real time. I experience very long re-charging times, and see not much current being dumped into the battery. I also use a stand alone CTEK 7002 smart charger at times, but it is also slow. Any ideas?
Russ

Have you checked your battery for charge (12.6v) with a standard DVM? When I look at the Trimetric site I see 2 shunts available. The 100 amp, 100 mV shunt appears to be the smaller of the two. Perhaps I'm missing something but a 100 amp, 100 mV ( 1 milliohm) shunt would be sending 1mV to the instrument for each amp of current flowing to the battery. Charging a single battery might be too low for the instrument to be accurate. Even at 10 amps you will only see 10 mV which could well be overwhelmed in an electrically noisy trailer environment. Just a thought, Raz
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Old 11-13-2013, 06:57 PM   #74
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Originally Posted by P. Raz View Post
Have you checked your battery for charge (12.6v) with a standard DVM? When I look at the Trimetric site I see 2 shunts available. The 100 amp, 100 mV shunt appears to be the smaller of the two. Perhaps I'm missing something but a 100 amp, 100 mV ( 1 milliohm) shunt would be sending 1mV to the instrument for each amp of current flowing to the battery. Charging a single battery might be too low for the instrument to be accurate. Even at 10 amps you will only see 10 mV which could well be overwhelmed in an electrically noisy trailer environment. Just a thought, Raz
Raz,
I just went out and looked. It is stamped 50mV. I did check the battery voltage with a Fluke back when I was setting up the Trimetric. It agreed at that time. I installed the meter about a year ago, and have forgotten many of the details pertaining to its operation. I have been simply toggling between modes to read voltage, current flow and direction, % battery charge, etc. I forgot how to enter the amp hours used mode, and will have to re-read the manual.
Russ
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Old 11-13-2013, 07:13 PM   #75
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You're about 4x too high.
Jeez, I can't get this electrical stuff right! I found a voltage drop calculator at supercircuits.com and just plugged in 12v DC 200' 5amps 14ga and pushed the button. It says 5 volts drop. I believe it to be correct. It didn't have a choice for copper or al wire, so I figured it would be copper by default.
Russ
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Old 11-14-2013, 01:27 AM   #76
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I use a 100 amp shunt with my trimetric and it works completely fine. However you need to set the meter to use it. There are two options, it's default is for a 500 amp shunt, the other setting is for a 100.
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Old 11-14-2013, 03:59 AM   #77
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Raz,
I just went out and looked. It is stamped 50mV. I did check the battery voltage with a Fluke back when I was setting up the Trimetric. It agreed at that time. I installed the meter about a year ago, and have forgotten many of the details pertaining to its operation. I have been simply toggling between modes to read voltage, current flow and direction, % battery charge, etc. I forgot how to enter the amp hours used mode, and will have to re-read the manual.
Russ
That appears to be the higher current shunt ( 100 microvolts for each amp flowing through it). Basically a shunt is a precision resistor placed in the circuit you wish to measure the current through. The voltage across it is proportional to the current flowing through it (Ohm's law). The shunt has to be large enough to produce a significant voltage but not so large as to effect the current. With either of these shunts you are operating on the low end, with very small voltages. Voltages you could not measure accurately with the average DVM. It's a little like trying to measure the thickness of a penny with a yard stick.

Next time your battery needs charging, disconnect it from the trailer and charge it with the CTEK charger. Over night should do. In the morning, check it with the DVM. If it's 12.6 V. or higher I would say the charger is working fine. Good luck, Raz
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Old 11-14-2013, 11:09 AM   #78
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I use a 100 amp shunt with my trimetric and it works completely fine. However you need to set the meter to use it. There are two options, it's default is for a 500 amp shunt, the other setting is for a 100.
Drew,
I'll check the setting. I'm pretty sure I covered that during the initial setup, but worth checking.
Russ
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Old 11-14-2013, 11:20 AM   #79
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Originally Posted by P. Raz View Post
That appears to be the higher current shunt ( 100 microvolts for each amp flowing through it). Basically a shunt is a precision resistor placed in the circuit you wish to measure the current through. The voltage across it is proportional to the current flowing through it (Ohm's law). The shunt has to be large enough to produce a significant voltage but not so large as to effect the current. With either of these shunts you are operating on the low end, with very small voltages. Voltages you could not measure accurately with the average DVM. It's a little like trying to measure the thickness of a penny with a yard stick.

Next time your battery needs charging, disconnect it from the trailer and charge it with the CTEK charger. Over night should do. In the morning, check it with the DVM. If it's 12.6 V. or higher I would say the charger is working fine. Good luck, Raz
Raz,
The CTEK has worked in the past, but it is slow when topping off a 80% charged battery. The battery won't accept bulk rates unless discharged more. I'll do some current draw measurements comparing the Trimetric to the Fluke to see if the Trimetric is calibrated properly. It was showing negative flow even with the CTEK hooked up while camping a couple of weeks ago. The Trimetric showed the proper charging voltage, but the current was backasswards.
Russ
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Old 11-14-2013, 11:23 AM   #80
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Does anyone know if the meter shunt can be mounted exposed to the weather? Mine is mounted on the tongue of the trailer and exposed. The brass is showing some patina. I went to the Deltec site and could not find any info.
Russ
EDIT
I Called Deltec and got the answer. They sell marine grade shunts that are plated and hold up in corrosive environments. He said that corrosion and crud buildup will affect the calibration and will vary over time. He suggested that I clean the shunt with non corrosive solvent, and then enclose it in a plastic box with vent holes drilled in the bottom. I asked it the shunt could be calibration checked with a DVM and he said no. I has to be done on a calibrated standard bench.
I will clean mine, and mount it in a box.
Russ
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Old 11-14-2013, 12:06 PM   #81
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Victron was supplying a water-tight enclosure for their shunt but absent from the package now.

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Old 11-14-2013, 02:30 PM   #82
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Most common shunts (i.e. 50 amp, 100 amp, 500 amp etc) are designed to drop a standard voltage value at the rated current flow. The most common value is 100mv. By designing meters and display devices to give full-scale readings at 100 mv a wide range of current capacities can be measured by selecting the correct shunt.

BUT.... shunts are precision resistive devices and leaving them exposed to the elements can quickly throw off it's very small resistive value by damaging the bonds between the terminals and the shunt material itself.

In short, never leave it exposed and, just the act of aggressive cleaning of a dirty shunt can destroy it's accuracy.

Best bet: New Shunt, either weatherproof protected or moved inside.
Second Best Bet: Get your cleaned up shunt retested for value.
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Old 11-14-2013, 04:33 PM   #83
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Quote:
Originally Posted by P. Raz View Post
That appears to be the higher current shunt ( 100 microvolts for each amp flowing through it). Basically a shunt is a precision resistor placed in the circuit you wish to measure the current through. The voltage across it is proportional to the current flowing through it (Ohm's law). The shunt has to be large enough to produce a significant voltage but not so large as to effect the current. With either of these shunts you are operating on the low end, with very small voltages. Voltages you could not measure accurately with the average DVM. It's a little like trying to measure the thickness of a penny with a yard stick.

Next time your battery needs charging, disconnect it from the trailer and charge it with the CTEK charger. Over night should do. In the morning, check it with the DVM. If it's 12.6 V. or higher I would say the charger is working fine. Good luck, Raz
Raz, When I looked at the cable it appears like it 4 wires. If so it's Kelvin which should negate noise in the measurement lines. Also according the web site the monitor is supposed to measure down to .5 amps. I agree with DVM not reading the voltage drop at any distance from the shunt. Short leads and right at the shunt, I think it would depend on the DVM.
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Old 11-14-2013, 04:41 PM   #84
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Originally Posted by ruscal View Post
Jeez, I can't get this electrical stuff right! I found a voltage drop calculator at supercircuits.com and just plugged in 12v DC 200' 5amps 14ga and pushed the button. It says 5 volts drop. I believe it to be correct. It didn't have a choice for copper or al wire, so I figured it would be copper by default.
Russ

First off make up your mind is it 200' or 100' .

Second AWG 14 is .2525 ohms per 100' At 10 amps that 2.525 volts drop.

In your second post you said 200' that would about 5 volts. 200' is also long ways about 2/3 of a foot ball field.
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