Battery recharging?

[Raz]

I think it would be more like designing a car without cruise control: the operator is required to monitor and respond to the speed [voltage]... and many of us seem to be old enough to remember when cruise was a fancy option.

A car without brakes crashes. A charger without a switching or trip point cooks the battery. A car without cruise control makes your right foot work harder.

While it is possible for a charger to just shut off at a set voltage - that's how traditional car battery chargers work -

My 1980's vintage Napa charger, that I paid $40 for, is pulse width modulated and switches from charging to float at a point adjusted by a potentiometer.

My Boler's obsolete converter disconnects the battery when the converter gets AC power, so although the battery never gets charged it also never gets overcharged, and the lights and other stuff in the trailer are supplied with a constant 12.4 volts. I believe that the optional charger switches a connection to the battery on and off as required to charge but not overcharge it.

Nothing boiling here

My (not moulded) 2002-vintage fifth-wheel trailer came with a Parallax 7445, which appears to be dumb, by any definition. The truly mediocre 7400 Series Converter/Battery Charger Owners Manual suggests (at least in my reading) that it is simply a constant 13.6 volt power supply which will wander up to 0.2V above that if there is no current flowing. That's high enough to charge a battery (although perhaps not quickly) and we hope low enough to not cook it too badly by overcharging... and higher than normal dumb always-on always-connected "float" chargers. It never shuts off or changes voltage.

Sounds like the charging system in most tow vehicles. Crude, but again nothing boiling here either.

I have since replaced this thing with a Progressive Dynamics Intelli-Power PD9260C, just like the one that came in my motorhome. The Intelli-Power series are not "dumb", and are designed in the currently typical fashion for "smart" devices.

This one could boil your battery. That's how it deals with stratification, a "problem" common to solar array storage batteries sitting in an attic but not so common on the tongue of a camper.

These will be really be "smart" when they get the correct input, electrolyte temperature. We're not there yet.

The term "smart" is a misnomer. There is nothing smart about a smart converter. It simply makes decisions based on software rather than hardware. The terms dumb and smart go back to the 1980's when microprocessors were first introduced into circuit design. In most cases adding a software component allowed for the cheapest solution for increasing product levels. Add a couple resistors, change a few lines of code, and charge a hundred dollars more.

Determining whether the battery voltage has reached a certain voltage threshold by a line of code or a comparator circuit is immaterial. To argue that converters that are not software controlled, i.e."dumb", will harm a battery and ones that are software controlled, i.e. "smart"', won't harm a battery without a thorough knowledge of the actual circuit designs is irresponsible and inaccurate.

I am forever seeing folks urged to replace a working, albeit, not state of the art converter (to the tune of several hundred dollars) to get a few extra months out of a $75 battery. Further, people who have never wired anything are urged to install it themselves. It's easy! So to alleviate the perceived risk of battery damage they create a possible fire hazard. Go figure.

[Carol H]

Originally Posted by Brian B-P

Linda, did the trailer come with a set of manuals? Usually, there is a very basic one for the trailer, but also a stack of the installation and operation manuals that come with each appliance and major piece of equipment. My Boler was 26 years old when I bought it, and it still had that stack of manuals. If there is one for a "power converter", that should tell you what it is and how it works.

See OP's post #5 in response to your #4. PO did changes to the electrical so not very likely the manuals that came with the trailer are going to help. Your right though if the PO left the manuals for the new stuff he put in the trailer that might help.

[RogerDat]

It seems that it really boils down to what "features" does the converter implement. And then how well. The technology used may impact the how well aspect, but does not preclude older technology that may do an acceptable job from the OP perspective.

Only two ways to know. Using a test meter and working through converter output Or the much easier approach. Post the model here or search for it online to find out the features. Seems to me most converters that implement floating or trickle charge will brag it in the manual, and possibly brag about the technology.

[Byron Kinnaman]

This and many other "electrical" issues have created myths. Once somebody says something that's incorrect it's picked up and repeated, misunderstood, and embellished. A new myth is born and forever will be held dear to those that don't understand the basics. Old myths are carried on forever.

[Thomas G.]

Originally Posted by RogerDat

.......... Post the model here or search for it online to find out the features........... .

That would be too simple.

[Lfoxmont]

I think I will have to search the storage space under the bed.....that's where the power cord comes in.....if I find it, I'll definitely post the model number and look it up on line. Thanks for all of your comments.

[Brian B-P]

Originally Posted by P. Raz

My 1980's vintage Napa charger, that I paid $40 for, is pulse width modulated and switches from charging to float at a point adjusted by a potentiometer.

That's nice. As recently discussed in another thread (Schumacher 10/2 amp Dual Rate Battery Charger) not only are these features not shared by all chargers, some chargers are still sold - Donna just bought one - which have no shutoff or mode switching at all in the manual version. Just because someone has a sophisticated converter/charger in an old trailer - or an automatic charger in their garage - does not mean that everyone does, and it would be irresponsible to say otherwise.

[Brian B-P]

Originally Posted by P. Raz

I am forever seeing folks urged to replace a working, albeit, not state of the art converter (to the tune of several hundred dollars) to get a few extra months out of a $75 battery.

I can only guess that this is a shot at me, as it is in the context of a post which quotes almost all of my post. I did not at any point in this thread urge anyone to replace anything; I reported what I did, and I have no delusion that anyone desires to follow anything I do. For clarification, I replaced that Parallax regulated power supply with a PD converter/charger because the Parallax was running so hot that it caused some fine sawdust (left over from the original construction of the trailer) to smoke; perhaps pushing 13.6 V regardless of battery charge state wasn't working out so well for it.

The Progressive Dynamics Intelli-Power PD9260C costs a couple hundred dollars, not "several" hundred.

I have kept the Parallax, and plan to use it as a bench power supply in my garage, for testing automotive electrical components - its operating characteristics seem well-suited to that use.

[rabbit]

Raz, your post #21 above very interesting in that the desulfation mode of a smart charger is described as having the characteristic of "boiling" the electrolyte. My PD9245 autocycles to desulfation voltage for 15 minutes duration at interval of 21 hours. What number of cycles would put the battery on the boil for a period of time sufficient to produce a significant loss of electrotyte?

Is increase or reduction of charging voltage based on electrolyte temp. difficult, expensive, physically cumbersome, commercially undeveloped, all of above? I suppose you are aware of self-styled battery experts on the internet who claim that a wet cell 12v batt can't be "pressurized" to full charge at less than 15+V? Would these experts be risking boiling out their batteries or do they have "software switching" of charge voltage based on sophisticated predictions of batt chemistry which the rv converter maker either does not have or is not willing to implement?

jack

[Raz]

Originally Posted by Brian B-P

I can only guess that this is a shot at me, as it is in the context of a post which quotes almost all of my post. I did not at any point in this thread urge anyone to replace anything

Nope, not a shot at you but rather a general observation.


P.S. I posted in Donna's thread this morning.

[Raz]

Originally Posted by rabbit

Raz, your post #21 above very interesting in that the desulfation mode of a smart charger is described as having the characteristic of "boiling" the electrolyte. My PD9245 autocycles to desulfation voltage for 15 minutes duration at interval of 21 hours. What number of cycles would put the battery on the boil for a period of time sufficient to produce a significant loss of electrotyte?

Is increase or reduction of charging voltage based on electrolyte temp. difficult, expensive, physically cumbersome, commercially undeveloped, all of above? I suppose you are aware of self-styled battery experts on the internet who claim that a wet cell 12v batt can't be "pressurized" to full charge at less than 15+V? Would these experts be risking boiling out their batteries or do they have "software switching" of charge voltage based on sophisticated predictions of batt chemistry which the rv converter maker either does not have or is not willing to implement?

jack

Jack, I'm an EE not a chemist. I can tell you how to design a circuit to do it but even the chemists can't agree whether it's a good idea. In the "smart" chargers decisions are made based on battery voltage. They read the voltage, convert it to a number and compare it to a preset value. When the battery voltage reaches that value the converter changes mode. But since each batteries chemistry is slightly different, the switch points are not optimum. A better indicator of where the charger should switch is electrolyte temperature. To do this would require a temperature sensor (thermistor) inside the battery and a charger that was programmed to interpret it. It would not surprise me if this is done in commercial systems with $1000 batteries. With RV batteries all this finesse is wasted the first time the owner leaves his battery sitting all winter uncharged. Raz