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Author Topic: Converter Question  (Read 5185 times)

Orick

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Converter Question
« on: August 20, 2010, 11:33:24 AM »
For some time now I've noticed that turning off the "Aux (house) Battery" switch shuts down shore power to the coach.  It hasn't been a major problem so it's languished on my list of things to do but I've finally gotten around to looking into it. 

It's my understanding that a converter takes over the duties of supplying 12v to the coach when attached to shore power and takes the coach batteries out of the equation... but keeps them charged via the Dimensions Inverter/Charger.  What I have been observing instead is the house batteries constantly cycling... that is discharging and then recharging as the charger goes into Bulk Mode.  All of this leads me to believe that if there's a converter in there someplace it's not working.  I should mention that I'm currently limited to a 20amp shore line and the charger in bulk mode can eat up several amps.

I've poured over my manuals and can only find a brief reference to the converter and it's role but no details on even where it is.  As I began to investigate, I've found that the 120v outlet located in the electric utility bay right above the inverter is dead.  I haven't yet tried to run a seperate extension cord to the the plug that uses it to see if that rectifies the 12v converter issue because I wanted to find out why the plug is dead first if at all possible.  I'm now looking over the wiring diagrams for the coach to see if I can find where the breaker controlling it might be but wanted to put out feelers to see if anyone else knew what might be going on.

Thanks in advance for any insights.
Rick, Nancy, Peanut, Lola (Westies) & Bailey the Sheltie Dog
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Jammer

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Re: Converter Question
« Reply #1 on: August 20, 2010, 12:11:22 PM »
The usual practice is for the converter and batteries to be wired together at all times.  The batteries are not disconnected for two reasons, one, it allows the converter to charge them while running the house circuits at the same time, two, it provides a degree of additional power filtering so that the power is cleaner even if shortcuts are taken on the design of the output side of the converter.

A properly designed, true three-stage converter should stay in float even when a load is applied and should only switch to a charging cycle if shore power is disconnected and reconnected or after a multi-day delay.  One thing to check might be to see if there's something wrong with the shore power side of things, a loose connection or something, that might cause a brief disconnect in the power to the converter, thus triggering another charge cycle.
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Orick

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Re: Converter Question
« Reply #2 on: August 20, 2010, 01:40:11 PM »
Thanks Jammer.  I think I'm really confused with terminology.  I thought an inverter was the device which changed DC to AC.  I thought the converter changed AC to DC to run the load in the coach.  And, I thought the charger was just to charge the batteries but it appears that the converter actually contains or "is" the charger? 

I have just learned that the "dead" plug I referred to is actually a switched outlet which has my engine heater plugged into it so it's not relavent to my problem.

You point out that "A properly designed, true three-stage converter should stay in float even when a load is applied and should only switch to a charging cycle if shore power is disconnected and reconnected or after a multi-day delay."  I can watch as my batteries fall from ~13v slowly down to ~12.2v and then the charger kicks into bulk mode and they charge back up and begin the cycle again as the coach consumes 12v power throughout the day.

What's got me scratching my head is that it is my understanding that proper operation of my system when plugged into shore power would have the converter converting a portion of the shore power into 12v consumption and just "maintaining" the batteries via the 3 stage charger.... but, it appears that what's happening is that the house batteries are supplying 12v to the coach for consumption and the charger is simply charging them when they get depleted.  ???

I guess I'll give Winnie a call Monday if I don't get it figured out this weekend.

Thanks again...

Rick
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Jammer

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Re: Converter Question
« Reply #3 on: August 20, 2010, 02:48:55 PM »
Thanks Jammer.  I think I'm really confused with terminology.  I thought an inverter was the device which changed DC to AC.  I thought the converter changed AC to DC to run the load in the coach.  And, I thought the charger was just to charge the batteries but it appears that the converter actually contains or "is" the charger? 

The terminology is confusing, all the more so because the RV industry uses different language than the electronics industry.  I've been a little fast and loose with language in my reply above and I'll try harder here.

A "converter" changes 120 volts ac to 12 volts dc.  In the 1950s, RVs (well, house trailers, they called them then) either didn't have a 12 volt system, or had duplicate lights and appliances for 12 and 120 volt.  So you'd have a light switch that said "off," "city," and "battery," and the light would have a 12 volt bulb and a 120 volt bulb.  For things like the bathroom fan and the water pump they would use a universal motor and a transformer.

I think the original converters were just transformers and didn't produce DC, they produced 12 volts AC, and the incandescent lights and universal motors they used would work on either AC or DC so it didn't matter.  The DC thing came later but the name "converter" stuck even though they were now charging batteries too.

In a modern RV the "converter" charges the house batteries and provides 12 volts DC to lights and appliances, when connected to shore power or running the generator.

Anyway, your rig has what is usually called an inverter/charger, which has the traditional "converter" function built into it, with the addition of the "inverter" feature which produces 120 volts AC from battery (12 v dc) power.  With current technology the design of any kind of power converter is the same regardless of whether it's going from AC to DC, DC to AC, DC to DC, or AC to AC with a frequency or phase change.  So, many of the heavy and expensive parts can be used for both tasks, which is why the functions are combined.

It's called an inverter/charger rather than an inverter/converter because that terminology makes more sense to people who use them for stationary standby power.

I don't know much about the particular inverter/charger you have (I know the Xantrex ones better) but I don't think it should be doing that.  Whether it's a design flaw or something wrong with this individual instance, well, uh, good luck with that.  I'll be curious to see what they have to say for themselves.
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Orick

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Re: Converter Question
« Reply #4 on: August 20, 2010, 03:39:48 PM »
Thanks again Jammer.  I'm getting quite an education on this.  It's funny, I hadn't heard the term "house trailer" probably since the 50s and it made me laugh.  I'll give them a call next week and make a follow up post.

Rick
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Gary RV_Wizard

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Re: Converter Question
« Reply #5 on: August 20, 2010, 04:55:26 PM »
As Jammer says, the inverter, converter & charger in your coach is all the same unit and the battery is NOT disconsolate from the house 12v circuit just because shore power is in use. The charger simply puts out enough current to supply present demand and also maintain the batteries.

Theer are a variety of possible reasons you appear to lose 120v power if you move the battery switch to the Off or Store position. Depending on where the switch is in the circuit, you may be cutting off converter/charger output as well as batery power.  And loss of 12v power to certain devices means that shore power, though available, is inoperative. That's because the devices use 12v-powered controllers to manage their operation. Examples are the fridge, the thermostat (a/c andheat), and the Powerline Energy Mgmt. System. These all shut down when 12vpower is lost.

Simple answer is "Don't turn the Aux battery switch to Store/Off when using shore power". There is no reason to do so plus (at the very least) it prevents charging of the Aux batteries.
Gary
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afchap

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Re: Converter Question
« Reply #6 on: August 20, 2010, 05:06:31 PM »
Quote
Simple answer is "Don't turn the Aux battery switch to Store/Off when using shore power". There is no reason to do so plus (at the very least) it prevents charging of the Aux batteries.
I agree with Gary except for this last statement, except that I don't know that we loose any 120v power when we trip the Aux battery switch. Turning off the Aux battery switch on my Winnebago coach is not something I want to do when using shore power because we loose all 12v power to coach powered items ...ie. lights, refrigerator control board, ac/heating thermostats, etc.  BUT...turning off the aux battery switch DOES NOT prevent charging of the Aux batteries ...house batteries.  That is EXACTLY what I do when I use the Equalizing mode on my Xantrax Freedom inverter/charger.  I turn off the Aux Battery switch to cut the 12v connection to all 12v items powered by the house batteries, then I manually start equalizing mode to equalize the house batteries.
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Orick

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Re: Converter Question
« Reply #7 on: August 20, 2010, 05:23:44 PM »
Thanks guys.  Looks like what I was afraid might be a problem is actually something simply "working as designed". 

This all began a few weeks ago when I replaced my house batteries.  Like a good little wannabe mechanic, I turned off the house battery switch and that's when I realized that the fridge, Air Cond, and EMS went dark.  It was a hot day so I had to postone the work.... or deal with the rath of DW.

I finally got the batteries replaced a few days later but then we arrived at my in laws place and are limited to a 20 amp shore line so every bit of energy conservation came into play.  Gary helped me with a post about that topic because I was concerned that my Dimensions going into bulk mode would trip a breaker in the basement of the house if it were to come on with the first AC unit running... and the breakers aren't easy to get to.

From what I had read previously, both in my manual and on line, I was under the impression that shore power would provide 12vdc to the coach INDEPENDENT of the house batteries... I think it was that assumption that led me astray.  I don't think it was ever actually stated explicity but I somehow drew that conclusion. 

I think I actually understand how it works now and don't think a call to Winnie or Dimensions is going to be necessary.

Thanks Much for all the help!
Rick
Rick, Nancy, Peanut, Lola (Westies) & Bailey the Sheltie Dog
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Gary RV_Wizard

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Re: Converter Question
« Reply #8 on: August 20, 2010, 06:00:25 PM »
I too think your system may be "working as designed". The only question is whether the Aux switch is between the batteries and the charger or elsewhere in the power supply circuit. I've seen them done both ways and AFChap's report clearly demonstratives that at least some Winnies have the Aux switch between battery and charger. In that case, power would continue to flow to the 12v system, even with the switch off.
Gary
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John Canfield

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Re: Converter Question
« Reply #9 on: August 20, 2010, 08:17:08 PM »
The Dimensions inverter/3-stage charger (no 'converter' involved here) was wired directly to my house batteries (was because I replaced  my Dimensions with a Xantrex, but I left the primary wiring alone.)  The battery disconnect switch did not remove the Dimensions charger from the 12V house circuit.

So in my situation at least, if you are plugged into shore power, the Dimensions is turned on, the house batteries will be charged irregardless of the position of the disconnect switch.  Chances are great yours is the same as mine.

I don't remember much about the Dimensions, but on my Xantrex RS2000 I can program a max limit to the charge current - if I'm on 20 amp shore power, I can limit how much 120V power the Xantrex uses.

We have been on 20 amp shore power before and it can be a bit of a challenge if you are in a hot climate and need to run the AC.
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Orick

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Re: Converter Question
« Reply #10 on: August 20, 2010, 09:54:38 PM »
Thanks John... Actually I've been using the AC current limiter for the charger on my Dimensions since it cooked two sets of batteries in the first six months I had the coach.  That's when my dealer called them and was told to set the limit down from 25 to 5 amps.   ::)

Yep, this climate is a challenge on 20 amps but it's teaching me a lot about my coach that you just don't have to learn if you're on a steady 50 amp diet.  ;)
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John Canfield

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Re: Converter Question
« Reply #11 on: August 20, 2010, 10:07:04 PM »
Thanks John... Actually I've been using the AC current limiter for the charger on my Dimensions since it cooked two sets of batteries in the first six months I had the coach.  That's when my dealer called them and was told to set the limit down from 25 to 5 amps.

The typical scenario for cooking the batteries with the Dimensions is either a bad battery cell or cells, and/or the Dimensions is sick.  Reducing the charger AC current input to 5 amps is basically emasculating the charger and I think masking a problem.  My Xantrex will pump 100 amps into my house batteries (maybe 20 amps at 120V going in to the charger) in the bulk three-stage mode with no issues at all.
--John
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Orick

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Re: Converter Question
« Reply #12 on: August 21, 2010, 10:01:02 AM »
Great input.  I've always suspected this but now the challenge is going to be getting my dealer and ext wty company to convince Dimensions of that.  :(
Rick, Nancy, Peanut, Lola (Westies) & Bailey the Sheltie Dog
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Gary RV_Wizard

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Re: Converter Question
« Reply #13 on: August 21, 2010, 11:45:48 AM »
I've seen several reports of the Dimensions charger apparently causing battery problems. Here and elsewhere. I surmise john is correct - when a battery gets a bit old and weak, the charger keeps on pumping more and more amps into it, trying to bring it up to some target parameter, and "cooks' all the batteries in the process. Xantrex, Magnum, Progressive Industries, Iota, etc. avoid doing that, pretty much regardless of condition.  My guess is that Dimensions has a charge algorithm that works well in lab conditions but not so good in the field.

I doubt if "poor design" will be an acceptable reason for replacement under your extended warranty.
Gary
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Orick

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Re: Converter Question
« Reply #14 on: August 23, 2010, 12:21:35 PM »
Update....

Just got off the phone with Winnie and, as several of you have pointed out, the system is functioning as designed when throwing the "Aux Bat Disconnect" switch makes the coach go dark... even when connected to shore power.

Al told me that the Inverter/Charger feeds directly through the house batteries and that this is common on many/most of their coaches.

Thanks to all for contributing to this question. I know I've learned some things I didn't know before.   ;D
Rick, Nancy, Peanut, Lola (Westies) & Bailey the Sheltie Dog
2007 Itasca Ellipse 40FD
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