testing the charger/converter?

[beardrum]

I'm suspecting my converter/charger might be getting weak. Here's why:

I parked the Scamp after a several hour drive home, and left it connected to shore power. The Link10 monitor showed about 12.5 volts on the battery, but about a 0.2 Amp drain. It's been on now for about a week, and it still shows about 12.5 volts and a 0.2 Amp drain. I have no idea what's causing the drain. I think all the DC systems are off. I pulled the cover off the battery and checked voltage directly on the terminals, and got about 12.4 volts.

So I put my old simple-minded charger on the battery, and it promptly jumped to over 15 volts. I left it there for about an hour, disconnected it, and now the battery shows 13.2 volts, and the Link10 is flashing green, saying the battery is fully charged. That's about the behavior I expected or hoped for. I think the battery is OK, and that it actually hasn't drained much from when I disconnected it from the tow vehicle a week ago.

Shouldn't the converter/charger in the Scamp been able to charge the battery up to the point the Link 10 says it's full (flashing green) and given a voltage of 13.something? Or am I making up trouble?

How do I test the output of the converter? It's the 20 Amp Chinese-made "American" model supplied with the Scamp when it was new in 2005. I recently tested the battery with a hydrometer, and got a specific gravity close to 1.260, and I'll test it again after the battery sits for a few hours after zapping it with the charger.

Thanks for any thoughts,

Chuck

[Bob Miller]

You answered my 1st question already, an American (brand) converter. The one in our 2004 smoked long ago.

The second question: What is the voltage across the battery when the shore line is ON. If it's 12.5 volts you will never get a full charge, you need at least 13.4+ to get there. Try running your battery down a bit and see if the charging voltage goes up.

The "Full Charge" you saw after a short charge may just be what is called "Surface Charge" and may drop rapidly with even a slight load. Try it....

And, as I have done myself, and suggested at least 5 times in the past month, you might want to look into the Progressive Dynamics PD-4045 as a replacement for the Chinese Junque Scamp included. it's an easy fit. And, if it hasn't smoked yet, it's in your future.

[beardrum]

Yup, that what's I meant to say, it was 12 1/2 volts with the shore power on.

I'll go put a load on the DC system right now... that's why I was going to wait a few hours with the charger off and measure voltage again. After the surface charge has dropped off, it should be 12.75 plus or minus a few tenths, right?

I've been interested in the discussion about the PD-4045, Charge Wizard, etc - that's one of the reasons I've been watching my old converter's performance.

Thanks

[Bob Miller]

Just turn on a couple of regular lights for 10 minutes and see what the battery voltage drops to when you turn them off.

I'd be proactive with a new converter this winter, they almost never fail when at home, the further away you are, the better the chance of failure.

[beardrum]

After 2-3 days sitting quiescent on the converter, the voltage in the system is 12.65, and the Link 10 is still flashing green, telling me it thinks the battery is at full charge. If the converter were working correctly, charging into what was a few days ago a full battery at 13.2 volts that has not got any load on it, I'm thinking it should still be at 13.2 volts, or closer to it than a half volt lower.

The Link10 could well be crazy as far as I'm concerned. I don't know enough about it to be convinced it's reporting the state of charge correctly, but I trust the voltage reading it gives me, because I've checked at the battery posts, with he battery disconnected from everything, and it is within a few hundredths of what the Link10 reports.

So I think the converter either is not charging at all, or is not charging at full tilt. Is there a way to test the output of the charger with a meter?

thanks

cg

[Steve L.]

There are potentially a number of phantom loads. Perhaps the trailer's TV antenna amplifier is on. Some have a tv or car-type radio connected to 12vDC which draw current even when turned off. Even the Link 10 draws current in standby especially if it's flashing but you want to reset it after you're sure it's back to full charge and you're not confident of that yet.

I have the LinkPro but have used the Link 10 previously. I consider them good units and I tend to believe them, assuming they're hooked up correctly. I'd consider checking the voltage at the battery with a digital voltmeter (or two to get a consensus among the three measurements) to verify the 12.6vDC. But I normally believe the voltage reading unless I have reason to suspect otherwise. Xantrex still has manuals online I believe.

The LinkPro flashes at me when it's returned the amp-hour debit back to zero (or into negative amp-hours) and can sometimes get out of sync and needs to be resynced. The Link 10 has to be reset occasionally as well. Plus you have to enter the battery's amp-hour rating for the meter to show state of charge correctly and different batteries and older batteries have different amp-hour ratings. Resetting it will stop the flashing.

At the moment, I'm more suspicious of the converter/charger.

Another thought would be to add a second charger to the battery (no need to disconnect the converter) to see if the charge voltage goes to 13+ volts as another check of the battery monitor and converter.

[Bob Miller]

With your charging voltage at about 12.5 volts the battery is NEVER going to fully charge. But, the good news is that, as electron flow is always from a point of higher potential to one of lower potential, the low voltage will be less apt to fry your battery(s).

My best friend in troubleshooting this kind of problem is a DC Amp clamp. I have a Craftsman Model 82369 AC/DC Multimeter with DC Amp Clamp.(usually much less than $100) As most amp clamps don't measure DC, be sure before you buy. With this, set on a 10th's amp scale you can explore around and find exactly where any phantom load exists.

But, without some info about the condition of the batteries, any measurements taken off the charger, except for charging voltage, may have limited value.

When we go to the Dr. she often does "r.o." tests. meaning to "Rule Out" certain issues. In this case, because it's fairly cheap and easy, I would first r.o. the batteries by pulling them and getting them tested and then look into find the the voltage adjusting pot that can be cleaned and adjusted to bring up the charging voltage. But, keep in mind that, after doing that, you will never want to leave it connected for days at a time without use to avoid overcharging.

[beardrum]

I've tried to eliminate phantom loads, by making sure the antenna booster is off, the face plate is out of the CD player, etc. The Link10 still shows a draw of about .2 Amps. I suppose it could be measuring/reporting it's own power consumption (there's a hefty shunt on the plus side of the batteries).

Steve, it's nice to hear some good words about the Link10. I did find the manual on line, but must admit I fell asleep somewhere between "Charging Efficiency Factor" and "Peukert's Exponent." I do have the amp-hour capacity set to about 50 as I recall, and I have reset the amp-hour consumption number to zero a couple times, mostly to experiment with the effect of the various parameters. As you probably can tell, I don't have it entirely figured out yet. By the way, I did connect another charger, and the voltage went to 15.something, then tapered to 13.5 or so. After that the Link10 started flashing full.

Bob, where would the voltage adjusting pot be? On the converter's circuit board? Which would mean either standing on my head under the back bench and trying to look at something a couple inches from my nose, or uninstalling it enough to take it apart, in which case I'd be inclined to take your earlier advice and simply replace it with a PD-4045.

A clamp-on DC Ammeter is probably in my future as well as a new converter.

Thanks, everybody, for your copmments.

cg

[Carol H]

Originally Posted by beardrum

Bob, where would the voltage adjusting pot be? On the converter's circuit board? Which would mean either standing on my head under the back bench and trying to look at something a couple inches from my nose, or uninstalling it enough to take it apart, in which case I'd be inclined to take your earlier advice and simply replace it with a PD-4045.

when I first got my trailer I would also stand on my head in order to trouble shoot issues with items in the rear hatch - had a heck of a time just opening up the converter box to replace a fuse in it when it was found not to be charging.

That was until I discovered that the back bench only has about 6 screws holding it in place. Way easier/faster just to take the bench out makes working in that area *way* easier - especially if you ever decide to change out your rear tail lights.

[Darwin Maring]

Bob Said: a replacement for the Chinese Junque

Shame on Bob, He just gave Junque a bad name by lumping it in with Chinese stuff.

[Bob Miller]

Yep, you get to lay on the floor and look in the front side at the circuit card area. It's usually a slotted pot, meaning it doesn't have a stem like a volume control, just a small slot for a screwdriver to adjust with.
As it will be very dirty from age, I suggest that you get a spray can of contact cleaner, spray it good, twist the pot full range several times, spray again and then turn on power and try to make the adjustment with the batteries connected.

[beardrum]

Thanks Bob. Would I read the voltage at the battery or somewhere closer to the converter?

[Bob Miller]

Because you are most interested in what voltage is apparing at the battery after any voltage drop(s) along the way, measure for about 13.4 volts at the battery.

However, if the voltage at the converter is much higher than that, you might look for loose connections between the converter and the battery.

[Byron Kinnaman]

The American converter stops charging too early. A few years ago I tracked them down, I don't remember that actual name of manufacturing company, it's not American. I manage to contact them vial email because I was concerned about over charging (boiling out the electrolyte). They indicated they were pretty sure that wouldn't happen since the charger part stops charging somewhere in the 12.2 to 12.8 range.
Generally I don't use the converter, I use a Battery Maintainer when at home to keep the battery fully charged. At time like now where I have the Battery Maintainer occupied with a second vehicle, I let the American do it's thing. I rely on the tow to get the battery fully charged while in route. Once in camp I use a 65 Watt solar panel to keep things running.

As far as what drawing current. Two things come to mind one, your meter or your reading of the meter could be off a bit and the current draw is closer to 0.02 amps rather than 0.2 amps. The other is if you have a propane detector installed, which is supposed to be installed so that it can NOT be turned off.

[Raz]

Originally Posted by Byron Kinnaman

As far as what drawing current. Two things come to mind one, your meter or your reading of the meter could be off a bit and the current draw is closer to 0.02 amps rather than 0.2 amps. The other is if you have a propane detector installed, which is supposed to be installed so that it can NOT be turned off.

Yup. The other thing that occurred to me was if you have a refrigerator with electronic controls (most over 2 ft^3 do) you will have a parasitic draw of 200-500 mA. Raz

[Byron Kinnaman]

Originally Posted by P. Raz

Yup. The other thing that occurred to me was if you have a refrigerator with electronic controls (most over 2 ft^3 do) you will have a parasitic draw of 200-500 mA. Raz

Ya, I keep forgetting about those fridges with electronic controls. Mine doesn't have that battery eating feature.

[Raz]

Originally Posted by Byron Kinnaman

Ya, I keep forgetting about those fridges with electronic controls. Mine doesn't have that battery eating feature.

Neither does mine. We must be anti-technology

[beardrum]

That's the inside of the American converter. Where would the voltage adjustment pot be? I don't see anything obvious.

BTW, the voltage between the big horizontal yellow and white wires is 13.2 when the circuit breaker (the left one of the pair on the right) is on, zero when I turn the breaker off. Also, the red and black wires leading down to the cover on the floor go to a small LED that seems to be burned out or not working - I've never seen it come on, and I didn't even know it was there.

Anyway, the big question now is to track the line that goes back to the battery and measure the voltage there.

[Bob Miller]

Sorry Chuck, not a clue on the American (brand) I was thinking of the other American (made) converter, from another thread.

But, if you have 13.2 VDC at the converter, you will have less at the battery.

We had to chuck the American (brand) converter in our Scamp as soon as smoke started coming out of it the first time we connected to shore power after bringing it home.

[beardrum]

No worries, Bob. My point was really that I'm not very inclined to stick my screwdriver into an energized circuit board , especially one that combines 120VAC and 12VDC in an inaccessible place, all wire-nutted, cable-tied, cable wrapped, electrical-taped, in-line fused, fastened down and thoroughly hidden behind various and sundry permanent structures. Sorry, <Rant Mode OFF>

Thanks for everybody's comments!

c