Consistent 12 volts for sensitive electronics.

[HamRad Mobile]

Good morning, Dave; 

     Yes, sir, close.  What I have is the Parallax Power Components or Parallax Power Incorporated "TCRU" variant.  That is the one with the Temperature Compensation circuitry and the 25 foot long sensor for use with the battery charging portion of the unit. 

     And, as you indicated, yes, it does have the PPC FH-7100-11L eleven ATC fuse position "100 Ampere" rated DC power distribution PCB assembly.  I am not happy with the way that it was made, and with some of the ratings or specifications.  First, I think that "100 Ampere" rating is optimistic.   Then there is the point that the first two output fuse positions out of the eleven are rated for holding a 30 Ampere ATC fuse, but the wiring terminals can accept only up to a 12 AWG wire.  To comply with the normal NEC recommendations, either the fuse rating should be dropped to 20 Amperes to work with 12 AWG copper wire, or the wiring terminal size should be increased up to where it will accept a 10 AWG copper wire that is rated to carry up to 30 Amperes.  Then there is the point that the main heavy gauge wiring terminals for 2-14 AWG wiring are not adequately soldered onto the heavy current PCB traces to reliably carry anywhere near 100 Amperes of current.  To me it looks like the workers in Mexico who were assembling the things were instructed to be more concerned with saving the Tin-Lead (Sn-Pb) solder than they were with making a reliable electrical connection that will carry the device rated current. 

     If anyone feels compelled to challenge my ability to judge the quality of a soldered electrical connection, I do feel honor bound to reveal that I did spend the full two weeks at the George C. Marshall Space Flight Center in Huntsville, Alabama, at the NASA Reliable Electrical Connections School learning both how to make such connections for electrical or electronic circuitry intended for launch into space (and a lot of mine were), and the second week was spent learning how to train others in my organization on how to make those connections also. 

     The battery charging portion of the PPC TCRU device:  Yes, sir, I agree.  While I did read from their information that their schematics and other detailed descriptions of their products are "proprietary and not available," I am able to tell from the illustrations that I have, that there is absolutely no suitable high current filtering nor any voltage regulation on the output from the RV 12 VDC power converter portion of that device which comes out on the Blue and White wires going to the FH-7100-11L 12 VDC power distribution panel, and passes through the two parallel 30 Ampere (or three parallel 20 Ampere) ATC fuses on the way to the eleven fuse position 12 VDC power distribution portion for the coach 12 VDC power system.  It may be that there is a battery voltage regulation circuit for the part that goes out to the 8 AWG wire going to the batteries, but I cannot tell what is under the "fish paper" protector over that part, and, as stated earlier, I do not have a "proprietary" schematic for it, nor have I taken the case apart and opened up the box to see what is really inside the aluminum enclosure.  And, to be honest, with that direct connection between the Blue wire and the +VCC wiring terminal to go the coach wiring 8 AWG wire going onward to the coach batteries, I cannot really see how that battery charging circuit can be regulated.  Clearly it is not series regulated, and I cannot see anything in the aluminum case that is large enough for it to be shunt regulated.  The closest thing I can see in there that could be considered to be a "regulation" device is that series connected 0.15 Ohm 50 Watt "Kool-Ohm" resistor in series with the rectified 12 VAC sine wave coming from the two diode rectifiers following the 24 VAC CT transformer secondary winding. 

     And, again, Dave, thank you for the references to the other makers' products that really do look like modern switching mode power supplies with real filtering and regulation.   My intention at this time is still to design and install a filtering and regulation system that will work with any of the older really simple ones like the type 6345 and any of its brethren.  The filtering is easy.  It is just the voltage regulation to hold down the voltage under a very light load that is going to be a little more difficult.  I have a couple of ideas.  I just need to put them together and actually try them out to see how they perform. 

          Enjoy; 

          Ralph 
          Latte Land, Washington 

[sasktrini]

I think this is an excellent thread.  And frankly, for anyone who is considering the outlay of converting their RVs lighting to LED, or maybe adding expensive electronic devices for communications, video, etc. to their coach wiring, the buck-boost from the original post isn't that much of an additional expense.


In a vehicle with a single electrical system, the output from an alternator typically passes through a voltage regulator.  So CB radios, televisions, inverters, LED lighting, etc. can run pretty reliably and consistently.  I do worry about my converter's 12VDC output when the input is dirty 120VAC.


It would almost be worth wiring up a separate fuse panel, fed by a buck-boost device, to feed lighting and other sensitive circuits.


That said, I have a question… examples of buck, boost and buck-boost devices seem to also pass the ground connection through them.  Does this mean that I would have had to wire a "clean" ground wire in any circuit wiring I would have wanted to protect with such a device?  Right now, my ground wires are routed spatially…devices in the same vicinity share a ground.  Somehow, I bet I'd have to dedicate a clean ground path.

[HamRad Mobile]

Good morning, Corey; 

     The problem with the original and basic RV 12 VDC power converter is not with "the dirty 120 VAC" that is being fed to it.  The Alternating Current waveform coming from the rotating field generators at the Grand Coulee Dam, the Boulder or Hoover Dam, the Bonneville Dam, and many other hydro-electric power generators really is pretty good, stable, on frequency (over time), and relatively clean, and it is necessary for the transformer action to take place in dropping the voltage from 120 VAC on the primary side down to the 12 VAC on the secondary side that will be then rectified (and should be filtered and regulated) and then go to the RV 12 VDC electrical power system.  The Onan Emerald III 120 VAC generator in the motor home RV is also a rotating field sine wave output type, but its parameters are not as finely controlled as the Bonneville Dam.  Most of the noise and voltage spikes you may see on the 120 VAC or 240 VAC electrical grid power system will come from nearby lightning strikes, large electrical motors, and a few other things.  Our electrical power system really is pretty good. 

     The problem with the surprisingly simple "RV 12 VDC power converters" is that they really are not what we think of when we talk about a "DC power" system, such as what you mentioned when you spoke of the common automotive "12 VDC electrical power" system.  The automobile type power system does a really pretty good job of providing the filtering and regulation of the electrical system voltage with the filtering of the battery in the circuit and the voltage regulator keeping the voltage well in the range of from 13.2 VDC to 14.0 VDC.  The automotive 12 VDC electrical power system really is a pretty good straight line direct current regulated voltage power system.  The common "RV 12 VDC power converter" output is not. 

     The only way that they can say that the "DC" part of that label can be applied to that piece of equipment is by being foot-loose and fancy-free with the definition, or by outright redefining what "DC" means.  I also say that this is the real reason why they call it a "power converter" instead of what the thing really should be, and that is a "power supply" with filtering and voltage regulation to provide a true straight line direct current output.  Selling something with a peak voltage excursion that is 50% higher than the nominal rated system voltage is not acceptable.  No wonder we are having problems with our furnace, water heater, refrigerator, and other system control boards in our RVs and now it really is much more evident with the death of the more efficient LED lighting we are trying to put into our RVs. 

     In most electrical and electronics systems, the base value tolerance for the components and other parameter values used to build those systems will normally be +/- 20%.  Better quality systems will be built with +/- 10% or +/- 5% tolerance components.  Precision circuits will often be built with +/- 1% or "selected value" components. 

     A fifty per cent (50%) variation, by definition, is "out of range." 

     The "buck-boost" devices.  We need to be a little bit careful here.  It does help to specify the device or at least the system that it is being used with.  There are "buck-boost" devices that are designed for use with DC power systems, and ones for AC power systems.   They are not the same. 

     The Blue colored device that was shown earlier in this thread is only one, and it is intended to work with a nominal 12 VDC electrical power system to maintain the voltage at 13.8 VDC for devices to be operated off a normal "automotive type 12 VDC electrical power system."  The one I have for use with my radios happens to be black, and it is rated to provide up to 30 Amperes of direct current at the regulated 13.8 VDC output when parked and operating off the coach batteries.  The coach battery voltage that I like to keep within is 12.6 VDC down to 12.20 VDC which is the 50% capacity point.  There is a 3.5 digit voltmeter right beside the RV power and control panel above the stove in the galley area.  There are also some other voltage readouts on the equipment that I use, so I can watch what the batteries and the voltage boost system are doing.   

     The "buck-boost" systems for 120 VAC power are for those places where you may have a chronically higher or chronically lower AC line voltage.  Then you could use a "buck" device to lower the AC line voltage down closer to the desired 120 VAC range, or a "boost" device to raise the AC line voltage up closer to the desired 120 VAC range, which could actually be a target of 117 VAC in many areas.  Most of these will be a transformer type device, and the "constant voltage transformers" will do both the buck and boost function automatically.  Many electrical devices start to have problems when the AC power is outside the range of a minimum of about 105 VAC and up to 135 VAC. 

     And, yes, these devices will have the "ground passed through them" or at least to them to meet the safety ground requirements. 

     It does help to be a little more specific about which buck or boost device you are discussing.  While they accomplish essentially the same goal, they do it on different types of power systems using different methods to accomplish that goal. 

     Grounding.  Oh, boy.  This is one of the more extensive subjects of the NEC and often is not really fully or properly applied.  The main way that we see it is in the 120 VAC portion of the shore power and AC generator power wiring in our RVs.  Types of grounds include the earth ground, the 120 VAC electrical system safety ground, the 120 VAC power system neutral return wiring, and for us in this case, the 12 VDC chassis ground or "battery minus or negative" current return wiring, and less often seen, there can also be a "lightning protection" ground and an "RF ground" for radio use. 

     That "lightning protection" part is in quotes, because if you get a direct lightning strike, all bets are off.  There is no such thing as "lightning protection" from a direct lightning strike.  You might be able to increase your system lightning damage resistance, but you probably will never achieve "lightning protection" outside of a complete metallic enclosure wired to an extensive earth grounding system where the enclosure contains everything you are trying to protect, and they have no connection to anything outside the enclosure.  That is another subject and goes off into the area of EMP and other things.  Later. 

     Your question about 12 VDC system ground wires.   Yes, ideally we would like to see separate "ground" wires or return current wires run back to a single common or "grounding" point which will also include the negative side of the battery system.  In common usage and practice with a low voltage 12 VDC system, usually we can use the chassis or run a separate return wire back to the main grounding point.  And, as you have seen with many RV appliances and lighting, most of them do have a common 12 vDC common return wire connecting several of them back to the battery negative terminal eventually.  In all cases, the main thing is to make sure that you have adequate size wire for the total current that may be involved over the wire length for that run, and that the connections are adequate also for the current and they are clean.  Do everything you can to minimize any resistance and the development of any corrosion on those connections in the complete circuit. 

     In most cases, it will be only when we get into RF (radio frequency) grounding for radios and grounding to avoid common mode currents for some sensitive electronics equipment that we will need to be more careful with our 12 VDC grounding or return path wiring. 

     Corey, while I thank you for asking the question, it is also true that the answer may be more than you expect if it is to be complete.  And, as mentioned just above, "grounding" can be a much more technical subject in a few areas. 

          Enjoy; 

          Ralph 
          Latte Land, Washington 

[sasktrini]

Thank you.


Grounding… throughout the coach, I have run grounding wires from all my devices, though they are shared where possible, leading back to my converter.  More current I expect them to carry, the thicker the gauge wire I use.


Buck-boost devices… I had been focusing on the DC-DC type, which is where I had seen them having four leads or connection points… +/- DC in and +/- DC out.  So I lamented having to revisit my grounding strategy.  I think I'll be okay though.


I never contemplated a 120VAC device.  Wouldn't we be talking about wiring a surge protector into the AC input of the converter box to clean up the resulting performance of the AC and DC circuits?

[M & J]

So....... Are you guys working on your thesis or something??   

[sasktrini]

So....... Are you guys working on your thesis or something??   

Ladies love a little nerdy talk! (I may have heard wrong, and it's "dirty"… beginning to believe they prefer silence, because the other two don't work for me lol)


In the end, I'm trying to figure out whether I need to clean up the electricity that's coming through my shore cable into my converter, or if I have to clean up the electricity that's leaving it.  I guess if I see issues with my 12VDC lighting, but also plan on using 120VAC computers, TVs and music gear, I might need something for the whole system instead, and makes sure I have good 120VAC coming in.

[DaveVA78Chieftain]

Well, one must remember we are talking about moving over the road and through the woods vehicles.  Most devices that are purposely designed to be used in them are designed to withstand the rigors of service that they are intended to be used in.  It is when we want to install items (Microwaves, Home Computers, etc.) in them that where not originally designed for this application that trouble starts.  The bulk of converters installed prior to say 2005 where mostly just unfiltered full wave rectifiers with a separate battery charger circuit.  It was not until the advent of the modern 3 stage converter/chargers and inverter/chargers that more effective regulation and filtering was implemented.  These improvements sort of evolved due to boondocking desires as well as the desire by the older generation (baby boomers) wanting to full-time RV.   The older converters also stayed around as a lower cost option until the more modern units seen today came down in cost.  Part of that cost reduction driver is that baby boomer desire to travel.  Once they discovered that the old style converter was burning up their expensive deep cycle batteries the demand for improved converter and inverter technology greatly increased.  The other driver has been the push towards home and RV solar (Aww geeze Ralph, you want to run your fancy big screen TV off the solar battery bank via the inverter at nite also! $%#*% football).  So, if we are to reap the benefits of these advancements then we must also accept that the original stuff put in these lovely older beasts will have to be upgraded in order to take advantage of the newer technology.
One first needs to look at what was originally installed in these older RV's. The older converter technology was designed to support 12VDC incandescent lights, water pumps, and Fridges/Furnaces/Water Heaters that had control boards designed to account for the unfiltered Full Wave rectifier converters used at the time in almost all RV's.
Aww shucks, you mean a LED does not have the same electrical characteristics of a 12VDC incandescent lamp bulb?  Just saying, don't blame the older stuff because of what it was originally designed to support.
Of final note, when thinking of upgrading, please remember the lack of positive comments with a web search about a particular device can be just as telling as a lot of negative comments about a device.

[sasktrini]

I installed a new WFCO 8725 with a 30A shore cable.  The idea of LED lighting for boondocking seems logical and practical for a rig that will be used a lot.  I'm glad that I have tested my electrical with one LED bulb rather than my computer.  But hey, personal electronics have gotten more sensitive in just the last decade.  They work great in a sticks and bricks building and in our cars and trucks.  But I never imagined how different an RV could be.


Honestly, I don't recall a conversation quite like this anywhere.  Could there be a simple solution?  Maybe a $5 device on my lighting circuit is sufficient to prevent me from burning out an investment in LED retrofit bulbs.  I dunno about the quality of 120VAC my system has… seems fine for power tools, but not sure about plugging my computer in.

[DaveVA78Chieftain]

Trying to keep this as a simple solution for the average reader here.
You can regulate/filter at the end device, or you can designate a given supply circuit branch to be regulated/filtered, or you can regulate/filter the complete system.

Tim's original approach Post 1 of this thread was system oriented approach.

Now various inexpensive adjustable buck-boost regulators are listed here: EBAY - boost-buck converter

A higher output amperage device could be wired in for a branch circuit.

A lower output amperage device could be wired in at each end unit (LED a very low amp devices).  This is what I mean by "devices which were designed to be used in a automotive environment".

A branch or end device approach "isolates" the effects of say a noisy 12VDC furnace blower motor or 12VDC water pump motor on the rest of the system

[Bnova]

I installed a new WFCO 8725 with a 30A shore cable.  The idea of LED lighting for boondocking seems logical and practical for a rig that will be used a lot.  I'm glad that I have tested my electrical with one LED bulb rather than my computer.  But hey, personal electronics have gotten more sensitive in just the last decade.  They work great in a sticks and bricks building and in our cars and trucks.  But I never imagined how different an RV could be.

Sasktrini, I forget now, did you say you are burning up LEDs when running on converter power?

I was just at my MH a few minutes ago, and I switched between conv power and battery power several time and I could not detect even the slightest difference in the quality of the light.  No flickering either.

Honestly, I don't recall a conversation quite like this anywhere.  Could there be a simple solution?  Maybe a $5 device on my lighting circuit is sufficient to prevent me from burning out an investment in LED retrofit bulbs.  I dunno about the quality of 120VAC my system has… seems fine for power tools, but not sure about plugging my computer in.

Sasktrini, I forget, did you say you are burning up LEDs when running on converter power?

I was just up at my MH a few minutes ago and I switched between conv power and battery power and I could not detect even a slight difference in the quality of the light.  No flickering either.

[Bnova]

Once they discovered that the old style converter was burning up their expensive deep cycle batteries

don't blame the older stuff because of what it was originally designed to support.

the lack of positive comments with a web search about a particular device can be just as telling as a lot of negative comments about a device.

Dave, I know there's probably been countless threads on battery life, but how is the converter killing these batteries?  Is it from having shore power plugged in for months on end?  My single coach battery is now exactly a year and a half old and I've run the furnace and a light through the night when I was boondocking for 10 days and then recharged off of the alternator the next day while driving.  And this battery seems like it is still in good condition.  What is the general expected life of a battery in terms of seasons?

I plug in every couple months maybe just to top off.

Praise your comments about the older stuff and design for a different era.

I love to look at reviews, especially when the poster gets detailed about what they've done and you discover they are using it incorrectly.

[DaveVA78Chieftain]

Originally the charger boards on older converters like the 6345 series were designed to output 13.5 - 14.1 VDC.  The actual output value at any point in time is dependent upon battery state of charge.  For the 6345, when the battery is confirmed to be 100% state of charge (SOC) by the technician, the battery charger board output is supposed to be adjusted to 13.8VDC.  Battery manufactures have determined that 13.8VDC "float" voltage is far to high and slowly "boils" the water in the battery until it is all evaporated if not topped off periodically (monthly refill if converter is always connected to shore power).  Even though the current flow at 100% battery SOC is minimum, that 13.8VDC voltage still causes the boiling problem.  Currently, the generally accepted "float" voltage for a wet cell battery is 13.1VDC.  Unfortunately, some converter manufactures (e.g Parallax) still design to the 13.8VDC float value.
Most other converter manufactures, like the one's I listed above, have converted over to 3/4 stage converter/chargers.
Stage 1, Bulk/Boost Mode: Max recharge current until battery voltage comes back up to about 80% SOC (12.5VDC) (trigger point for stage 2).  Recharge current must be reduced at the trigger point to avoid damaging the battery.  Bulk/Boost mode is used to quickly charge the battery
Stage 2, Absorbtion Mode: Current is reduced to a level such that the charger output voltage is maintained at approximately 13.6-13.8VDC.  As the battery continues to charge, the internal resistance increases. The charger compensates for this resistance change by reducing the charge current flow in order to maintain the 13.6-13.8VDC output voltage level.  Once the recharge current reaches around .2 amps, the charger triggers into stage 3.  The Stage 2 concept is equivalent to a automotive alternator circuit design.
Stage 3 Float mode:  Charger voltage drops to 13.1VDC with around .1 amps.  This maintains the battery in a healthy state without the  boiling water problem at 13.8VDC.
Stage 4 Equalization Charge (not all chargers have this):  Periodic short period of 15-16VDC voltage.  Used to agitate the battery water in order to mix up the electrolyte so that it does not seperate into it's different physical components resulting in excessive lead sulphate in the battery floor.  Build up of lead sulphate in the bottom will eventually build up and short out the cells.  Part of what limits battery life.
These modern smart converter chargers remain in Stage 3 float mode until they sense a current draw on the system (lights on, water pump, etc.).  At that point they shift to stage 2 to provide enough current for the requested loads so they will not drain the battery.  Once the loads are turned OFF, the converter shifts back to Stage 3 after a short period of time to prevent boiling the battery.

So, you can see that when using a battery based system, the discharging/charging requirement results in wide range working range of 11.5VDC to as high as 16VDC.  The newer converters may have better AC ripple filter (<50mV vs the 6-8VAC of the 6345) however the DC working range is wide.

So, the acceptable working range of any device connected to this system must be designed to work within at least a 11.5 to 16VDC range.  To make this working range more restrictive (e.g 12.5VDC +/- .5VDC) requires adding additional components like a buck-boost DC regulator/filter to the circuit.  This brings me back to the devices added to the system must be designed to be used within the operational characteristics of the system.

Schools out Whoppie!

Dave

http://www.chargingchargers.com/tutorials/charging.html

[Bnova]

Thank you Dave, so for someone like myself who has a MH that sits idle most of the time, this will not be a problem.  The battery only needs to be on the charger maybe once a month for an 8 to 12 hour period while sitting idle in the winter.

But I can see where if you lived in it or were out for an extended stay somewhere plugged into shore power for days/weeks on end that this could be a problem.

How ever, looking at the schematic from Parallax, it appears that the charger output could be adjusted to 13.1 volts at R5.

I know it seems like I'm reaching here, but what do you think about that?

[DaveVA78Chieftain]

I would leave it at 13.8 in your situation and maintain your existing schedule.  I am reasonably sure dropping it to 13.1VDC would keep it from bringing the battery back up to 100% SOC.  The 13.8VDC value would represent the charge mode cutoff voltage representing 100% SOC.  That may sound odd when at rest 100% SOC voltage is 12.5VDC however, that is the difference between charge complete voltage and at rest voltage once the charge voltage is bled off.

[Bnova]

Appreciate the response Dave, thanks again.

[sasktrini]

I've got one LED installed, which has been shown surges or flickering.  I'm always running through the generator via the shore cable.  However, it also could be an ill fit of the bulb in the light fixture, vibration from doing refurb… obviously, there are a number of factors that could contribute to what I've experienced.

[Bnova]

I installed a new WFCO 8725 with a 30A shore cable.  The idea of LED lighting for boondocking seems logical and practical for a rig that will be used a lot. I'm glad that I have tested my electrical with one LED bulb rather than my computer.  But hey, personal electronics have gotten more sensitive in just the last decade.  They work great in a sticks and bricks building and in our cars and trucks.  But I never imagined how different an RV could be.


Honestly, I don't recall a conversation quite like this anywhere.  Could there be a simple solution?  Maybe a $5 device on my lighting circuit is sufficient to prevent me from burning out an investment in LED retrofit bulbs.  I dunno about the quality of 120VAC my system has… seems fine for power tools, but not sure about plugging my computer in.

I would suggest using a laptop computer in the motorhome, it charges using an a/c adapter and with that you should have no problems being it's a DC output to the computer. 

I can't imagine having a desktop computer in the MH, much too bulky and too many cables etc.  I love the laptop, fold it up and put it away for traveling.

[HamRad Mobile]

Good morning; 

     On the topic of the problems with the LED lighting operating off the older "RV 12 VDC power converter,"  I was not referring to the LED lighting flickering or changes in the light color output, or anything like that.

     I was talking about the death of the LED lights when powered that way. 

     By death, I mean the destruction, failure, or burning out of sections of, or the entire failure of, the LED light itself.  LED parts that no longer make light when you turn it on. 

     The blinking or flickering of a light, such as with an old incandescent bulb or a florescent light tube fixture, or even an LED light vibrating in its socket, is something that I can live with.  It is the death of the things from using them on the frustratingly old DC power source that does not meet voltage specifications when connected to shore power that is the problem.  I stopped the program when I reached $200 worth of dead LED lights, until I can get the power supply system fixed.  When they cost between $15 and $35 each LED light that I bought, it adds up pretty fast. 

     Also, there is my concern for other electronics equipment, and for the simple type of voltage regulators used to drop the nominal "12 VDC" in an automotive type electrical system down to the voltage that our cellular telephones, GPS navigation systems, and other devices need for recharging their batteries.  I do not know which ones of those will not like that 18 VDC peak voltage coming out of my old RV 12 VDC power converter. 

          Enjoy; 

          Ralph 
          Latte Land, Washington