So I returned my Ultra III...

[Bruce B]

...converter. Like others here I thought that the simple single output voltage that Parallax uses was kind of dumb and would damage my battery (a 4d Lifeline AGM) so I ordered an Ultra III converter kit to replace it.
Just before I was going to install my new converter I noticed that it was made in China (strike one!).
Then, I removed it from the box and noted that due to sloppy assembly I had to re-tap a screw hole that held it into the metal frame so that it would sit correctly in the holder (see above comment about China) strike two!
Then I read the manual and the troubleshooting guide for the Ultra III unit. I began to wonder how this converter worked. The biggest omission seemed to be any type of temperature compensation for the charge profile. On a whim I tried calling the manufacturer’s number for technical support in the USA. No answer so I left a message. No reply 24 hours later so I called again, no answer. Strike three!

Next I decided to call Parallax tech support to ask “why no float voltage…?” I got some very interesting answers, some that I understand pretty clearly and some that I do not. The bottom line was that the tech (he is actually the engineer who designs their equipment) told me that the three step charge process doesn’t work well with a converter because of the typical residual 12 volt system draw found in most RV’s. He said that the 3-step converters really never get into the float mode as a result of that draw. He went on to say that he has several popular 3 step converters on his test bench that have never gone into float in spite of even very small residual loads applied. He added that Parallax does not recommend that the battery be charged with the converter for long periods of time anyway! He suggested that for storage an independent 3 step charger is a much better solution (think Battery Tender). The real issue according to Parallax is temperature compensation. They believe that this is much more important to battery life during converter use/charging than the float voltage and that they are on the cusp of introducing kits to allow their converters to adopt this important feature.

So anyone who has changed their converter to an Ultra III ever verified that the converter does drop the voltage to the 13.2 volt float setting? Does it stay there? I’d love to know…..
I returned the converter and took the 15% hit rather than put it in. I have a solar panel installation that will keep the battery topped up without needing the converter for charging over the long term. I think I’ll wait for the nice Mexican made Parallax upgrade instead!
Bruce

[azflycaster]

I don't have that converter, but I have a PD 9245 and it goes to float mode all the time. Since I have a vintage trailer that has no load when everything is off, it should go into float mode. This may not be the case with newer trailers.

[Bruce B]

I am very curious about all of this! For now I will just put the 12 volt system into the "storage" mode and disconnect the battery when my monitor says the battery is charged. Then the solar charger will see to it that it is topped up as necessary. I'm looking forward to see what shakes loose on this subject!

[Jammer]

I think there's a great deal of truth in what the Parallax guy said, but there are some missing pieces.

I have the stock Parallax converter in my trailer.

The way it works, essentially, it stays at float all the time. The float voltage it uses is a little higher that I might want for long-term storage in summer temperatures, but I have flooded cells, so I just add water 2-3 times a year and it works out OK. If the converter were temperature compensated I wouldn't have to do that, and I wouldn't have the opposite problem of undercharged batteries in really cold weather.

The disadvantage of single-voltage converters like this isn't really battery life. The problem is that it takes a very long time to recharge the batteries. The amount of time varies depending on depth of discharge, battery age, and temperature, but it's typically around 24 hours. With older batteries or at lower temperatures the batteries may never really reach full charge.

This is a huge problem, obviously, for anyone trying to run their generator for an hour or two a day to keep the batteries charged, as it is for anyone who doesn't have power at their storage location and is trying to charge the batteries at their house for a few hours prior to a bondocking trip.

Now, let's look at the bit about 3-stage chargers never entering float. I don't have samples on the bench to experiment with, but we can at least see the design intent by looking at the manufacturer's literature. In reality these things only have two modes of operation, other than the "equalize" feature, which isn't relevant to this discussion. There's the bulk/absorption phase, where the charger limits voltage to 14.4, the the float phase, where the charger limits voltage to 13.6. In many cases these values are adjustable and temperature compensated. There's no real difference between bulk and absorption, despite the hubris, what they call the "bulk" mode is just the part where the converter is operating at its current limit instead of at its voltage limit. The output can and does bounce between the voltage and current limits when large loads go on and off like the furnace or water pump.

The events that trigger the transition to "float" vary among manufacturers and models. The better designs have both a current trigger and a time trigger. The current trigger is usually around 20% of maximum output and is sometimes adjustable. The time trigger is typically around eight hours from the start of the bulk/absorption cycle, though I believe there are some devices that use a shorter time and start timing when the voltage limit (14.4) is reached.

A shortcoming inherent in this approach is that if the battery is near full charge at the start of a charging cycle, and the load is high enough to keep the output current above the trigger point, the output will stay at 14.4 for eight hours or however long the time limit is, which will overcharge the battery. There's no way to design around this without building a converter that has separate connections for the battery and the load, so that the controller inside can ascertain how much current is going to the battery without being fooled by the power draw from the lights, furnace, etc.

[Bruce B]

You make a lot of sense. If I understand you correctly you are saying that the Parallax charger is in essence just “floating” the batteries until they are charged thus the long charge times. I wonder if perhaps a good quality marine charger might be used to good effect to charge the batteries when a charge is needed. Then I’d get the benefit of a smart charger for the batteries (used with the house battery disconnected) and a good long term storage solution for the batteries. I could let the converter do its thing and provide 12volts for the trailer when I am plugged in and charge the batteries separately? I am just thinking out loud here….

As to time to transition to float voltage the only time I have ever had this luxury was when I had an Ample Power Energy Monitor on a sailboat. It kept the regulator from the bulk or absorption charging voltages unless the battery was actually down in charge as calculated by the monitor thus if I started the engine and then shut it off and restarted a little later I just kept to float. It was nifty but the reality is that I have not got this feature on our current boat and the batteries are lasting just fine without it, who knows?
Bruce

[Jammer]

Originally Posted by Rifboy

You make a lot of sense. If I understand you correctly you are saying that the Parallax charger is in essence just “floating” the batteries until they are charged thus the long charge times. I wonder if perhaps a good quality marine charger might be used to good effect to charge the batteries when a charge is needed. Then I’d get the benefit of a smart charger for the batteries (used with the house battery disconnected) and a good long term storage solution for the batteries. I could let the converter do its thing and provide 12volts for the trailer when I am plugged in and charge the batteries separately? I am just thinking out loud here….

It adds complexity but if it works for you, fine. You would need a charger with output of around 1/4 of the amp hour capacity of the batteries to charge them quickly.

As to time to transition to float voltage the only time I have ever had this luxury was when I had an Ample Power Energy Monitor on a sailboat. It kept the regulator from the bulk or absorption charging voltages unless the battery was actually down in charge as calculated by the monitor thus if I started the engine and then shut it off and restarted a little later I just kept to float. It was nifty but the reality is that I have not got this feature on our current boat and the batteries are lasting just fine without it, who knows?

Exactly. It's clear that the better technology is better. What is less clear is whether the shorter charge times provide any useful benefit the way most people use their trailer. My approach has been to beef up the ability of the tow vehicle to charge the battery, and I think that's going to work OK for me. YMMV.

[RickDavis]

Faster charge times a an advantage when charging is done with a generator.

I have never used one of the fancy converters and am not convinced there is a lot of benefit unless hooked to shore power most of the time.
I am using an old magnetek unit. This is a ferro resonant circuit. Since I also have a generator from prehistoric times ( Honda EM 600) I can move it slightly off 60 cycles and maintain a 20 amp or so charge rate. The battery voltage etc. is monitored by a Trimetric 20 20 meter so I am able to tell what is happening and also monitor the number of amp hours used and replaced..
Normally the charging is done by the solar system. On the rare occasions we are hooked to shore power I only turn the charger on as needed instead of leaving it on.
Not high tech, but the golf cart batteries will be 9 years old in June so something is working right.
If I were to go to a high tech charging system I would want one that could be forced to stay in bulk charge mode when using a generator.

Of course if you usually have hookups your needs are totally different

[vswingfield]

Originally Posted by azflycaster

I don't have that converter, but I have a PD 9245 and it goes to float mode all the time. Since I have a vintage trailer that has no load when everything is off, it should go into float mode. This may not be the case with newer trailers.

I have a 9280 in my Excella. It spends most of its time in float mode. When the batteries are charged up, even running the lights and stereo rarely gets it out of float mode. It does regularly, about once a day, go into boost mode shortly for desulfation as designed.

I have a VoltMinder in plain view and the Charge Wizard Remote Pendant installed, so it is easy to keep track of which mode the 9280 is in.

The (PD) Inteli-Power seems to work great.

[Wabbiteer]

My take on new tech batteries - 13.2V might be better called a storage voltage instead of a float voltage.

AGMs and Gel batteries can call for a low float voltage if its got high current to back it up - since it can't boil the electrolyte to keep it stirred up they depend on high current surge to get the gel & semi-gelled AGM electrolytes moving by sheer force of expansion and convection.

My batteries call for unlimited charge current at partial discharge & C/4 amperes ONLY at 100% discharge. On these 10-year warranty 110AH batteries the only time it calls for a high-rate-float (above storage, above float, less than an absorption voltage) is when another 'expected' charger power outage with necessary continued battery usage would drop the state-of-charge below 20% and cause more harm by over discharge than some light cooking of the battery.

[Bruce B]

Originally Posted by RickDavis

.....Not high tech, but the golf cart batteries will be 9 years old in June so something is working right.....

That is impressive!Do you ever verify the actual capacity remaining in the batteries? I'd love to know how much is left in that bank but clearly you are doing something right...
Bruce

[RickDavis]

Originally Posted by Rifboy

That is impressive!Do you ever verify the actual capacity remaining in the batteries? I'd love to know how much is left in that bank but clearly you are doing something right...
Bruce

I have never discharged them all the way down. We typically use 30 to 40 amp hours per day which still leaves us at about 80% charge based on an expected 200 AH capacity
As it happens, we just returned from 2 months in Florida, most of it running on solar. When doing maintenance today I did put my Harbor Freight load tester on them and they passed that fine.

I am sure at this point the capacity is down from new but it is still getting the job done.
I know their days must be numbered but I am curious as to how far I can take it .

[Bruce B]

Originally Posted by RickDavis

As it happens, we just returned from 2 months in Florida, most of it running on solar. .

Rick,
What size are your solar panels?
Thanks,
Bruce

[RickDavis]

Originally Posted by Rifboy

Rick,
What size are your solar panels?
Thanks,
Bruce

I have 5 panels totally 250 watts.
When parked in the open it is more than adequate, however we camp in the woods a lot so a generator back up is needed occasionally.

[Bruce B]

Nice to know, I've wondered what the actual "real life" expectations are for solar panels. Now I know that with enough sun I can expect to get 30 to 40 amps back into batteries from 250 watts of panels.
Thanks,
Bruce