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Old 06-10-2022, 02:11 PM   #1
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Sunova power converter question.

2004 Itasca Sunova. Can someone tell me how the converter and 12 volt system works on this model? When plugged into shore power does the converter keep the coach batteries charged so they can power the 12v items? Does the converter take over for the batteries as well as charge them? I replaced my converter and it runs non stop now. Argh!
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Old 06-10-2022, 02:26 PM   #2
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It might depend on which model of Sunova that you have but here is how it worked on my 2003 Sunova 30B. When connected to shore power the converter charged the batteries and supplied power to the other 12V items as long as the coach power switch (the salesman switch by the door) was on. So when plugged into shore power the converter ran non stop. However, the converter usually ran silently unless it was asked to supply a lot of 12V power to the batteries and other items. If that was the case, the fan on the converter would come on to keep it cool. I suspect you hear the cooling fan.

So the question is: why is your converter working so hard? Are you using a lot of 12V items or are your batteries really discharged? If your batteries are really drained, it may take the converter overnight to charge them (assuming they are not damaged and can't be charged).

Also, why did you decide to replace your converter? Perhaps there is a setting on the new converter that is not set correctly for your type of batteries.
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Old 06-10-2022, 03:02 PM   #3
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The original converter went out last week. I replaced it with one that has the same specs and it runs non stop. I've got 13.8 at the converter as well as the batteries. I would think that once the batteries were charged the converter would would kick off and charge at a lower rate or ? The last one I replace in a previous Adventurer would shut off once in a while.
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Old 06-10-2022, 03:45 PM   #4
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I can think of a few things that might cause this... but the number one thing I'd check is the batteries. If your previous converter wasn't charging them they may have been damaged beyond repair. If that was the case then the converter might run non-stop.

Unplug from shore power, wait a couple of hours or even overnight and using a multimeter check the voltage of your house batteries. You'd like to see 12.7v or more. If you see 12.0v or less they are likely dead.

Discharged batteries that are left that way for a period of time are not salvageable.
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Old 06-10-2022, 04:05 PM   #5
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Thanks. I'll check that. The heat sink fried in the original one. It took a couple of days before I figured out what was going on. The batteries finally got low enough that the lights were getting dim so who knows. They are 3 years old. I'm starting to think the converters working properly and I'm just hearing the cooling fan because it's a different and less expensive unit.
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Old 06-10-2022, 07:01 PM   #6
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Do be careful when doing voltage tests on batteries as they mislead a large number of folks. We often have a problem with knowing what it is we are reading on voltages.
If you do the reading when there is any form of charging, you don't get the battery voltage but the voltage coming from the charging and it takes a few hours for the batteries to settle after the charge is removed for us to really get a true battery voltage!
A somewhat easy and handy idea of the battery condition is to have a known charge go to them for 6-8 hours and then let them "rest" with no drain nor charge for 6-8 hours and see if they are at close to 12.8. IF they show 12.8 or so after a rest, they are in good shape as that is as high as a lead acid battery will charge. Anything higher is not true battery voltage but the remaining "surface charge" from charging.

If you charge for a good long period and then let rest but only find 10-11 volts, the batteries are likely bad.
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Old 06-10-2022, 07:50 PM   #7
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I disconnected them from the converter a few hours ago and plan on checking them in the morning. Does the converter continue to send 13.8 volts to the batteries even after they are fully charged but at a reduced amperage? The batteries aren't warm like an overcharge. Thanks for the help .
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Old 06-10-2022, 09:50 PM   #8
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I disconnected them from the converter a few hours ago and plan on checking them in the morning. Does the converter continue to send 13.8 volts to the batteries even after they are fully charged but at a reduced amperage? The batteries aren't warm like an overcharge. Thanks for the help .
You've just pointed to something that is often not well understood about charging batteries.
Back to basics may help to understand what happens better.

Why current flows? It flows due to the difference in voltage of two spots. It is not something seperate that any power source changes to change the amps moving but simply as the voltage difference in two spots changes, the current changes.

We often speak of voltages in our RV as the difference in the voltage of the battery as compared to the ground connections. The difference is often 12 volts. So if we accidentally connect the 12 volts at the positive post to ground, we get a really big rush of current. Big flash, big trouble as too much current flows!

But if we connect the 12 volts at the start battery to some other point like the
coach battery when it is maybe 10 volts, we get a lot less current flowing as the DIFFERENCE in potential (voltage?) is not 12 volts but 2 volts!
Current flow is directly changed by the DIFFERENCE and it works the same if we are speaking of a 24 volt source into an item that is at 22 volts. The difference is only 2 volts and the current is determined by that difference.

All that is spelled out by Ohm's Law but that tends to confuse lots of folks who are not used to the formulas, etc. used there.

The big take away is that when we have an alternator that can put out a whole bunch of amps (125??) what controls how much it actually puts out is the difference between that point and the point where it is being stored or used, like the battery.
Rather than trying to control the output amps as well as the voltage, we use the theory and just control the voltage.

When the alternator starts and finds a weak battery at some low voltage like 10 volts, the difference in the 14-14.5 from the alternator creates high amp flow as the difference in potential is pretty high (4-4.5 volts?) but as that flow reaches the battery and has to start reversing the chemical reaction that has been making the battery voltage go down, it soon runs into the area right at the positive post being a higher voltage than the first 10 volts and that automatically slows the current flow.
But we also don't want to drive six hours with an alternator putting out 14.5 into a battery which is ideally only going to charge to 12.8 as that just boils off water, gets hot and all kinds of things we don't want.

So we have different stages of charge with different things like alternators and converters. We want them to put out higher voltage to get a low battery brought up quicker but then we don't want to over charge it, so as a really good charger gets closer to the correct final level, it begins to back the output voltage down in stages. But if we turn on a bunch of stuff, it can also boost the voltage back up and put out lots more if needed to keep the batteries from going back down.
Different chargers have different levels and ways to do it but there are often bulk charge at higher voltage, some mid level voltage and a final float voltage as the battery reaches the ideal level to maintain it best.

One of the nice things about just controlling the voltage and letting the current go with what fits is that we don't have to figure in so many variables.

If you leave a site and the coach batteries are all way down, the alternator just stays in bulk or higher voltage mode a bit longer and if we turn on several things as we drive, that just keeps the voltage difference a bit lower, longer and the alternator still just works on getting all the batteries connected back up to some preset level where it senses that it is nearing the point where it lowers the output voltage to keep from overcharging any of the connected batteries.

At one point you asked about the converter taking over from the batteries. That is not done but it is more like they are all on the same connectionand if you are using the battery to run a vent fan, it is not so much that the power is coming from the battery but more that the power is taken out of the whole circuit connected together, so saying it is coming from the batteries or from the alternator is not really possible without watching a speciifc electron.

Kind of like having several buckets all connected and a pump putting water in at the same time. Kind of like asking if the water came out of bucket one or two or from the pump? The batteries are just storage for what the alternator is putting out and we never expect to need more than it can handle as it is so oversized to cover the worst load we should ever have.

Or kind of like you and the wife having a shared account? You and her put in, the money comes out and is it your money or her money doesn't really count as long as the input is more than what's taken out??? I sahould never mention that idea!!!
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Old 06-11-2022, 05:19 AM   #9
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Great explanation. So for my simple mind since the batteries aren't getting warm and boiling over it would seem that all is well. The cooling fan running all the time is probably normal and I'm only hearing now because it's a different and less expensive model?
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Old 06-11-2022, 12:15 PM   #10
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So for my simple mind since the batteries aren't getting warm and boiling over it would seem that all is well.
No, not necessarily at all.

Yes, you can overcharge and ruin your batteries by boiling away the electrolyte. BUT you can also ruin your batteries by depleting them and leaving them in a depleted state for a long time.
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Old 06-11-2022, 12:35 PM   #11
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The cooling fan running all the time is probably normal and I'm only hearing now because it's a different and less expensive model?
It seems suspicious that your old converter burnt the heatsink and the fan on your new converter runs constantly. Both seem to be heat related. Is something putting a big load on your converter? Are the cooling vents for your converter blocked by something? Are you camping in Death Valley right now? If you have an electric fan, you might try blowing that into the cabinet where your converter is located to see if the converter fan turns off. You could also try opening the 12V circuit breakers/pulling fuses one by one to see if that makes any difference.

I've only had experience with my two motorhomes so others may have different experiences, but the fans on my converters almost never run. My 2003 had incandescent lights. If I turned a bunch of those on and the battery was a little down then the converter fan would come on. I switched it to LEDs and my new RV has LEDs so the 12V load is much less.
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Old 06-11-2022, 01:37 PM   #12
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I do have a small fan I can direct at it. I can feel the exhaust from the cooling fan and it's not very warm. But I want to try that.
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Old 06-11-2022, 01:45 PM   #13
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I just checked them after having shut off the auxiliary battery switch yesterday afternoon and they are at 13.5. I'll shut the converter off and turn on some lights to see if the number drops quickly.
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Old 06-11-2022, 02:03 PM   #14
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After running on battery only for 15 minutes with lights,fans,ect the batteries only dropped from 13.5 to 12.5.
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Old 06-12-2022, 07:45 AM   #15
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13.5v is a surface charge from charging. So your charger is working.

A drop to 12.5v isn’t bad unless they keep dropping in a short period of time. If the voltage keeps dropping then your batteries are not holding a charge very well.
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Old 06-15-2022, 09:14 PM   #16
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Thanks. I'll check that. The heat sink fried in the original one. It took a couple of days before I figured out what was going on. The batteries finally got low enough that the lights were getting dim so who knows. They are 3 years old. I'm starting to think the converters working properly and I'm just hearing the cooling fan because it's a different and less expensive unit.
If you are handy you can replace the noisy fan with a quieter one from a computer power supply, they are both 12VDC!
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Old 06-15-2022, 09:35 PM   #17
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I am somewhat handy and I've been thinking about doing that. I still have the old converter and have thought about trying the fan out of it.
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Old 06-16-2022, 12:41 AM   #18
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I would buy something from Amazon or Newegg, check the specs for noise levels, generally the slower fans are quieter.
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Old 06-16-2022, 09:16 AM   #19
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We hear battery voltages mentioned often. And a couple of tenths doesn't sound like much difference. Hey it's still over 12 volts that's good right? Well no.
The State of Charge for a Sealed or Flooded Lead Acid battery voltage is: 100% 12.70, 75% 12.40, 50% 12.20, 25% 12.00, 0% 11.80: And lead acid batteries that get discharged below 50% will get “sulphated” over time; and in this state, their actual energy capacity is reduced, lower than the voltage reading might indicate. That's why sometimes only a load test of a charged battery will tell the tale.
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