Xantrex Battery Charger Overheating - Frigoboat Fridge

[Captain Bill]

If the problem is on the boat side and not the shore side an isolator is not going to do you much good in solving this problem, though it might prevent other problems. I'm not sure what the capacitor will do for you in this instance. Capacitors pass true AC. They're great for taking out ripple on a DC line, but if the current is truely reversing it's going to pass the ac component. If you just had a lot of noise it would take that out quite well. For example, if the voltage on your fridge line was varying around 12v, say from +9 to +16 while your charger was trying to hold +13.1 the capacitor would work great at stabilizing the voltage at 13.1. However if you are truely seeing + and - 28V on that line the capacitor will pass that, though inverting and modifying the wave form. The exact effect really depends on the frequency of the AC and the size of the capacitor. Since we don't know the frequency at this point it's hard to predict what the effect will be. Besides this only masks the real problem, it doesn't fix it. There's no telling what other problems the real problem might cause. A diode would kill the AC component, but leave you with a 28V pulsed DC component that you really don't want on a nominal 12V line either.

With regards to finding a person with the right equipment, I'd guess that a manine electronics shop would be more likely to have an occiliscope than a marine electrician, but the electrician might be more familiar with Marine AC systems and could more quickly narrow down the source of your problem.

[senormechanico]

Originally Posted by Sailormannn

I googled around a bit looking for info at Radio Shack, etc on capacitors for this application. Couldn't really find anything. There were a few BIG capacitors for big audio systems but nothing 24v 0.5 farad. Any ideas what and where I would find?

Radio Shack should change their name to Remote Control Toy and Cell Phone Shack.
They are useless for electronic parts.
Try Digikey.com or Mouser Electronics.
BTW, the 0.5 mfd capacitor doesn't have to be rated at 24v.
Anything above your working voltage is fine. It could be 200v, 400v, 1kv.
It doesn't matter. Even the 0.5 is not critical. Bigger is better in this instance.

The easiest thing to try right now would be (imho) substitution of the battery.

[Kapena]

The voltage rating will be the toughest part. A surge rating of 20 volts will be adequate. An audio shop will sell these, or Best Buy, Fry's, possibly even wally world in the audio section. The bigger the value the lower the voltage rating for a particular size. You will find that I rated this appropriately for trade off of size and voltage. It's still a pretty big can. Use 8 or 10g wire. short leads. Directly to the output of the xantrex charger. Most have screw terminals so you can use a spade lug.
Example Overstock Auctions Rockford Fosgate Punch CPC05-03 1/2 Farad Capacitor Item 38710815
Don't get a high end audio version as it is money spent poorly. $20 is what you are looking for.

The purpose of the capacitor is to bypass any noise. The higher the frequency the lower the impedance (resistance). It tends to smooth out the voltage by supplying current when the voltage is lower and absorbing it when the voltage is higher (than the average value). Z=1/(2PI*F*C) where Z is impedance in ohms and F is freq in Hz. About .005 ohms at 60Hz. A smaller value can also work but this should be easily obtainable.

You don't need to substitute the battery. Adding the capacitor to the lead of the xantrex is EXACTLY like a new battery to the same place. Just a note...all chargers rely on the battery to do the filtering for the output. We are attempting to improve this condition with the capacitor.

There are other options to this, but requires more labor, or a different charger. This would be my approach. It is an easy install and a good test, and will also improve your vhf radio and stereo performance when the charger is running.

Make the AC measurement FIRST. Check the AC connections. If you can plug the boat into a different outlet, on shore, that is a good indication that the shore power needs fixing. You don't need an isolator, it is for a different issue. Also, as noted in previous posts, a good electronic tech or engineer could fix this in a few minutes. Much more difficult over the web.

[senormechanico]

If that capacitor doesn't do it, NOTHING will.

[Sailormannn]

Originally Posted by Kapena

The voltage rating will be the toughest part. A surge rating of 20 volts will be adequate. An audio shop will sell these, or Best Buy, Fry's, possibly even wally world in the audio section. The bigger the value the lower the voltage rating for a particular size. You will find that I rated this appropriately for trade off of size and voltage. It's still a pretty big can. Use 8 or 10g wire. short leads. Directly to the output of the xantrex charger. Most have screw terminals so you can use a spade lug.
Example Overstock Auctions Rockford Fosgate Punch CPC05-03 1/2 Farad Capacitor Item 38710815
Don't get a high end audio version as it is money spent poorly. $20 is what you are looking for.

The purpose of the capacitor is to bypass any noise. The higher the frequency the lower the impedance (resistance). It tends to smooth out the voltage by supplying current when the voltage is lower and absorbing it when the voltage is higher (than the average value). Z=1/(2PI*F*C) where Z is impedance in ohms and F is freq in Hz. About .005 ohms at 60Hz. A smaller value can also work but this should be easily obtainable.

You don't need to substitute the battery. Adding the capacitor to the lead of the xantrex is EXACTLY like a new battery to the same place. Just a note...all chargers rely on the battery to do the filtering for the output. We are attempting to improve this condition with the capacitor.

There are other options to this, but requires more labor, or a different charger. This would be my approach. It is an easy install and a good test, and will also improve your vhf radio and stereo performance when the charger is running.

Make the AC measurement FIRST. Check the AC connections. If you can plug the boat into a different outlet, on shore, that is a good indication that the shore power needs fixing. You don't need an isolator, it is for a different issue. Also, as noted in previous posts, a good electronic tech or engineer could fix this in a few minutes. Much more difficult over the web.

Thanks for this. Going to try a different dock outlet tonight. If that doesn't work will have to take a closer look at the AC connections inside the boat. I already checked the inlet and didn't really see anything there. I tightened the connections Are there any other likely points of failure or things to look for. The boat is a 2004; I've owned since new. It's been used lightly in fresh water.

One other question on the capacitor. This would go across + - on the DC house out terminals on the charger. Do I need to worry about the engine battery if the charger is letting AC through the batteries or just the house.

[senormechanico]

Under discussion (imho) is the AC component on the DC line being generated by the refrigerator's power supply (which is actually an inverter) that is being back fed to the charger via the charger DC output.

The charger is being fooled by this ripple on its DC output, and is reading it as an overheat condition.

The capacitor will filter out this ripple (if indeed that's what is happening).

[twistedtree]

If I'm following correctly, two things trigger the "overheat" problem.

1) Fridge running and
2) AC power adapter for computer

If both these things are off, you can charge your batteries and the charger consistently outputs rated power without shutting down? And the problem started when you switched from another brand charger to the Xantrex? And you are measuring AC on the DC circuit?

If this is true, then I'd agree that the Xantrex charger likely has a noise susceptibility problem.

To sort out where the AC is coming from, trying measuring with just the fridge on, then just the charger on, etc until you find the source. Also,with EVERYTHING off, measure the batteries to see if you are picking up AC. If so, your meter may be giving you a false reading, so that's worth checking before getting too far.

Is it too late to return the Xantrex charger and switch to something else?

[Sailormannn]

Originally Posted by twistedtree

If I'm following correctly, two things trigger the "overheat" problem.

1) Fridge running and
2) AC power adapter for computer

If both these things are off, you can charge your batteries and the charger consistently outputs rated power without shutting down? And the problem started when you switched from another brand charger to the Xantrex? And you are measuring AC on the DC circuit?

If this is true, then I'd agree that the Xantrex charger likely has a noise susceptibility problem.

To sort out where the AC is coming from, trying measuring with just the fridge on, then just the charger on, etc until you find the source. Also,with EVERYTHING off, measure the batteries to see if you are picking up AC. If so, your meter may be giving you a false reading, so that's worth checking before getting too far.

Is it too late to return the Xantrex charger and switch to something else?

Some good suggestions but its probably too late to return the Xantrex for a refund

I tried another power source on the dock and ran some more tests but I'm getting some unusual readings. Tried 3 different meters. 2 regular albeit fairly cheap simple volt meters (analog and digital) and a clamp meter that has leads to test voltage and using the clamp for amps. With the charger and refrigerator both on, both simple volt meters are showing ~28v AC and 13v DC at the batteries and refrigerator. The clamp meter doesn't show any AC voltage (none at all) using the leads but it shows 0.2A using the clamp. I tried multiple times. On the AC outlets in the boat all meters show 115v AC including the clamp meter so I know it's working and I'm on the right settings.

With the charger off (unplugged) still getting the AC readings on the volt meters and no AC voltage reading on the clamp meter. I am seeing some AC current though at the batteries and refrigerator with fridge on batteries. This is weird. Are my instrument all wacky or does this point somewhere else. With everything off and the shore power disconnected at the batteries I'm still getting the same readings for AC on the simple meters and no AC on the clamp meter using leads. There no amperage in dc or ac as everything is turned.

Pretty weird. Sounds like I need to try again with better meters but the readings are pretty odd. Don't understand these AC readings at all.

[twistedtree]

Given those results, I'd be inclined to disregard the AC readings on the DC circuit. A lot of meters are designed to measure 60hz AC. If you have noise feeding back into the DC system from the fridge's internal inverter (someone said it had one, so I'm taking that for granted), it will be at a much higher frequency. Unless you have a meter that can handle it, I wouldn't trust the readings.

Could you purchase a different brand charger, try it, and return it if it doesn't solve the problem? Then sell the Xantrex on eBay if it turns out it's the source of the interaction?

I think you could waste a lot of time chasing down meters and oscilloscopes, and experimenting with filter capacitors, where simply trying a different charger would cut right to the chase. After all, that's what changed coincident with the problem occurring. And filter caps aren't really a solution anyway since if you need one to make things work, it's really just indicative of a poor design in one of the underlying components. And to filter the AC out of the DC, you really need to use a scope to see the noise and confirm it's gone once you filter it. Different frequencies will require different value caps to filter the noise, and you will be running blind without a scope.

[Sailormannn]

Originally Posted by twistedtree

Given those results, I'd be inclined to disregard the AC readings on the DC circuit. A lot of meters are designed to measure 60hz AC. If you have noise feeding back into the DC system from the fridge's internal inverter (someone said it had one, so I'm taking that for granted), it will be at a much higher frequency. Unless you have a meter that can handle it, I wouldn't trust the readings.

Could you purchase a different brand charger, try it, and return it if it doesn't solve the problem? Then sell the Xantrex on eBay if it turns out it's the source of the interaction?

I think you could waste a lot of time chasing down meters and oscilloscopes, and experimenting with filter capacitors, where simply trying a different charger would cut right to the chase. After all, that's what changed coincident with the problem occurring. And filter caps aren't really a solution anyway since if you need one to make things work, it's really just indicative of a poor design in one of the underlying components. And to filter the AC out of the DC, you really need to use a scope to see the noise and confirm it's gone once you filter it. Different frequencies will require different value caps to filter the noise, and you will be running blind without a scope.

Good points. Those AC readings really through me. Not sure if my refrigerator has an inverter. Will have to let Richard Hollman weigh in on that. He was in on this thread earlier. A couple of other factors here. I replaced the charger since I have had some issues with my previous Cristec charger putting to much charge in on float. I want to make sure there isn't an underlying issue with the electrical system that was masked by the previous charger and the Xantrex has revealed.

While looking over the system tonight I noticed that there is an "isolator" between the charger and the batteries. It has some corrosion on the terminals. Not sure what this is designed to do and if the corrosion could be impacting things. I will have to clean. There's also a bit of corrosion on the main house fuse and the terminal connections.

On swapping in another charger that is definitely an option but I would prefer to get the Xantrex working if I can. I have the remote panel mounted so would have to cover that and the remote is a nice feature since you can tell at a glance what the charger is doing. It an option though.

All ideas and feedback are really appreciated.

[AnchorageGuy]

Originally Posted by Sailormannn

While looking over the system tonight I noticed that there is an "isolator" between the charger and the batteries.

That is an interesting observation. The old style isolators do not allow the battery to fully charge because of the voltage drop through the isolator. You might want to eliminate the isolator even if it has nothing to do with your problem. Chuck

[Seahunter]

Sheesh, let's all meet at Sailormannn's boat an' figure it all out. Sailormannn, do you have enough beer?

[twistedtree]

Telling us the make and model on the "isolator" would be helpful. There are two different kinds - those built around diodes that have a voltage drop across them and can create charging problems, and those that are built around relays and do not pose such charge problems.

Back to your original problem, my first guess would be that old charger was fooled by the fridge into remaining in Absorption mode and never actually went into float, or at least didn't go into float quickly enough. This can happen with any DC load while charging, and has nothing to do with the fridge specifically.

This is an unfortunate loop hole in the 3-stage charge protocol that is at best partially plugged by manufacturers. The transition from Absorption to Float should happen when the battery's acceptance current drops to about C/50, or 2% of the battery's capacity. The problem is that all the chargers in the world measure the current going out of the charger, not the current going into the battery. If you have any loads, the charger sees the current and assumes it's still being absorbed by the battery, and the absorb cycle never ends. The batteries get over charged, vent, and ultimately fail from chronic overcharging.

The plug for this loop hole is to have an Absorption timer which limits Absorption time regardless of charge current. I say it's a partial plug because it doesn't address or solve the root problem, but rather limits the extend of damage experienced by each charge cycle. On some chargers this time limit is adjustable, and the trick is to set it just a little longer than the actual absorption time.

Sorry of all this has been covered already - I'm jumping in page 6 or so of this thread and confess I haven't read the first 3 pages or so.

[rourkeh]

I have the same charger and it worked well for several months after install but then it started flashing the fan and A/C fault codes on the remote panel and would only function when I reduced the charging output to 60% or less. Then it just quit working all together and the only thing that will power up is the remote panel and that is not for long then it shuts down. I am way down south in the islands right now and there just happens to be an authorised Xantex repair facility here so I am going to talk to them today and see if they can repair the unit. My best guess is (and I heard this from someon else with the same unit) that these chargers are cheap because the internal parts are rubbish. My friend had to replace the tiny cooling fan twice and relocate the unit in the open so it did not over heat constantly. The fan inside is about the size and quality of a computor cooling fan and is overworked and unable to keep the boards inside cool enough so the charger burns out. Time to buy a Victron unit which is alot more money but what was suggested to me in the beginning when I opted to save $$ and buy Xantrex. You get what you pay for I guess.....

[senormechanico]

Originally Posted by Sailormannn

With the charger off (unplugged) still getting the AC readings on the volt meters and no AC voltage reading on the clamp meter. I am seeing some AC current though at the batteries and refrigerator with fridge on batteries. This is weird.

What you are seeing is the AC component being generated by the inverter in the fridge.

I suspect it is this AC component which is fooling the charger.
That's why substituting a different battery or installing the Mondo Large Ginormous Capacitor was suggested.