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Old 05-29-2019, 07:29 PM   #1
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Mystery 2.25V present with everything disconnected???

I'm cleaning up some wiring after having some new lithium batteries installed in our 2014 International 25 FB in the storage area under the bed. I also had a PD4655Liv converter, Victron a battery monitor 712, and a couple of other things installed at the time. Because nothing the new DC items weren't working properly except the PD4655Liv, I decided to revisit how everything was connected on the DC side. I started this project by disconnecting shore power and removed the leads from the battery terminals so there are no power sources (AC or DC). However, as I was going through all of the leads to the various components, I happened to measure 2.26 volts on the positive lead from my original WFCI 1000 watt inverter. Is there some sort of capacitor in the inverter or something else that might be causing this? Thanks!
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Old 05-29-2019, 07:41 PM   #2
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Quote:
Originally Posted by Scott66Carav View Post
I'm cleaning up some wiring after having some new lithium batteries installed in our 2014 International 25 FB in the storage area under the bed. I also had a PD4655Liv converter, Victron a battery monitor 712, and a couple of other things installed at the time. Because nothing the new DC items weren't working properly except the PD4655Liv, I decided to revisit how everything was connected on the DC side. I started this project by disconnecting shore power and removed the leads from the battery terminals so there are no power sources (AC or DC). However, as I was going through all of the leads to the various components, I happened to measure 2.26 volts on the positive lead from my original WFCI 1000 watt inverter. Is there some sort of capacitor in the inverter or something else that might be causing this? Thanks!
Yes
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Old 05-29-2019, 08:58 PM   #3
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Yes most likely a capacitor that is not blead down.
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Old 05-29-2019, 09:01 PM   #4
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Mystery 2.25V present with everything disconnected???

Which leads to a safety comment. Always check for voltages when you start to do any maintenance or modifications on a supposedly Ďdeadí system.

Capacitors can deliver quite a jolt to you or other hardware. Sometimes enough to be fatal. Air conditioning start and run capacitors are just one common spot where high voltage can lurk.

Donít ever assume a circuit is Ďdeadí without checking carefully. Itís quite possible YOU might be the dead one.

Been there, seen the sparks, survived. Itís no fun getting fried by voltages you didnít think were there.
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Old 05-29-2019, 09:14 PM   #5
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Originally Posted by Scott66Carav View Post
I'm cleaning up some wiring after having some new lithium batteries installed in our 2014 International 25 FB in the storage area under the bed. I also had a PD4655Liv converter, Victron a battery monitor 712, and a couple of other things installed at the time. Because nothing the new DC items weren't working properly except the PD4655Liv, I decided to revisit how everything was connected on the DC side. I started this project by disconnecting shore power and removed the leads from the battery terminals so there are no power sources (AC or DC). However, as I was going through all of the leads to the various components, I happened to measure 2.26 volts on the positive lead from my original WFCI 1000 watt inverter. Is there some sort of capacitor in the inverter or something else that might be causing this? Thanks!
from PD's website>
Electronic converter/chargers first convert the 120 VAC 60 Hz from the outlet to 120 VDC after it passes through Diode Rectifier #1, the Capacitor then filters the ripple voltage. This 120 VDC voltage is then fed to an Electronic Switching Circuit that converts it to back to AC and increases the frequency from the original 60 Hz to 3,500 HZ. This high frequency AC voltage is now fed to a step-down transformer where the output voltage reduced to approximately 13.6 volts AC and Diode Rectifier #2 converts the AC to 13.6 Volts DC and the Capacitor filters out the ripple.
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Old 05-30-2019, 10:03 AM   #6
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rmkrum, I definitely understand the importance of electrical safety and it's why I'm doing this housekeep project as my wiring was an absolute mess. I don't work on the AC side of things at all. However, when working on the DC side I use a voltmeter and electrical rubber gloves. Before starting the project, I had the battery disconnect engaged, disconnected the shorepower, reviewed my "to be" wiring diagram with the techs at the battery manufacturer, discussions with other component techs to make sure they are functioning/wired properly. I was careful when removing the leads from the batteries (using rubber gloves) and placing them safely away from other wires and components.

I was just very surprised to find any voltage present in the leads I had disconnected from the battery. So now I'm just trying to confirm possible sources and did confirm with others in this group and just got off the phone with the WFCO inverter manufacturer, so I feel comfortable moving forward with the project. Thanks!



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Originally Posted by rmkrum View Post
Which leads to a safety comment. Always check for voltages when you start to do any maintenance or modifications on a supposedly Ďdeadí system.

Capacitors can deliver quite a jolt to you or other hardware. Sometimes enough to be fatal. Air conditioning start and run capacitors are just one common spot where high voltage can lurk.

Donít ever assume a circuit is Ďdeadí without checking carefully. Itís quite possible YOU might be the dead one.

Been there, seen the sparks, survived. Itís no fun getting fried by voltages you didnít think were there.
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Old 05-30-2019, 11:30 AM   #7
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Are you using a digital multimeter? They have very high input impedance which means they can show voltage even when there is very little energy. Use a small load (like a 1Kohm resistor) across the leads when you do the measurement. My guess is the voltage will soon die to very close to zero. If you don't have a resistor, use a light bulb or something ... measure while you have the bulb attached and after you remove it. Almost all the electronics on the 12V will have some sort of capacitor on the supply side.

As a side note to rmkrum's caution on caps. Absolutely right in general (especially things like old CRT color TV's), but for 12V systems its pretty difficult to hurt yourself with the caps in standard electronics. At worst you'll pull a spark, you will not electrocute yourself. Exceptions: If you've got supercaps with your lithium (almost never) or big beer-can caps for your aftermarket thumping audio system ....
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Old 05-30-2019, 11:58 AM   #8
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Flash burns and wiring damage can be a hazard...
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Old 05-30-2019, 10:57 PM   #9
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Yes I was using a digital multimeter. Over time the voltage did drop but I'll keep your suggestions in mind. I learned from the WFCO inverter tech, there is capacitance so everything seems normal. No burned wires or any damage along the way. My big thing with DC is that I want to ensure it's wired with large enough gauge and fused properly so it's efficient and won't start a fire. In this case the two lithium batteries are under my bed so I'm being a little extra careful during this project. Thanks!


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Originally Posted by Rhinno View Post
Are you using a digital multimeter? They have very high input impedance which means they can show voltage even when there is very little energy. Use a small load (like a 1Kohm resistor) across the leads when you do the measurement. My guess is the voltage will soon die to very close to zero. If you don't have a resistor, use a light bulb or something ... measure while you have the bulb attached and after you remove it. Almost all the electronics on the 12V will have some sort of capacitor on the supply side.

As a side note to rmkrum's caution on caps. Absolutely right in general (especially things like old CRT color TV's), but for 12V systems its pretty difficult to hurt yourself with the caps in standard electronics. At worst you'll pull a spark, you will not electrocute yourself. Exceptions: If you've got supercaps with your lithium (almost never) or big beer-can caps for your aftermarket thumping audio system ....
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Old 05-31-2019, 05:39 AM   #10
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Originally Posted by Scott66Carav View Post
Yes I was using a digital multimeter. Over time the voltage did drop but I'll keep your suggestions in mind. I learned from the WFCO inverter tech, there is capacitance so everything seems normal. No burned wires or any damage along the way. My big thing with DC is that I want to ensure it's wired with large enough gauge and fused properly so it's efficient and won't start a fire. In this case the two lithium batteries are under my bed so I'm being a little extra careful during this project. Thanks!
I always tell people when they are re-wiring DC circuits to plan wiring/circuit protection sizes for future expansion. For example, you later decide to add a 2000VA inverter. You plug in your coffee maker, which draws 1000W. The inverter will draw approximately 98 Amps from your 12V battery to provide this power. (1000W divided by 12V = 83A divided by .85 (the efficiency of the inverter) = 98A of 12VDC.

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