MEGAWATT 60-AMP INTRODUCTION

jrnymn7 wrote:
5. Temperature Compensation... something most "smart" chargers don't do.

This is a biggie for me. Weeks and months at 13.6V WELL above 77F can't be good for the batteries long term. I will admit, if I had a pair of Costco 6V's, I might not sweat it so much. Those batteries are cheap and I'm a weekend warrior. But I paid a decent chunk of change for mine and want them to last for quite a while.

mena661 wrote:
Weeks and months at 13.6V WELL above 77F can't be good for the batteries long term.

Hmmm ... my RV battery manufacturer says to float them in the range of 13.5 volts to 13.8 volts ... so weeks and months and years (in our back yard) of these kind of volts is good for them. I do disconnect them from the voltage source during 90+ degree days, however.

FWIW and interestingly, I believe that Mex disregards what his manufacturer says about float voltage and floats his Lifeline battery at about the same voltages as I use on my brand of RV batteries.

MEX also emphasizes the importance of a proper float for longest life. And I think he explained why he's ignoring his own advice. Since mine sit more than they get used, float is the most important maintenance I can do. Up until I got the MegaWatt, the batts have been seeing 13.6 all year round unless it was above 105 then I'd disconnect them for the day and reconnect at night. Quite a PITA as I don't want to spend that much time on batt maintenance. The MegaWatt enabled me to simply lower the float voltage and go back to living.

PS - I live in a hot climate. What most see as abnormal, we who live in these climates see as normal. Sometimes it snows here, when it does everything closes and people stay at home. People in places that have snow routinely still go to work, see a movie, get groceries and etc. I don't have the luxury of disconnecting my batts for half the year, they have to be ready to work.

Phil,

We all know in hot weather, batteries self-discharge faster. Therefore, if floating is so important, it is contra-indicated to stop floating them at such times. Instead of terminating float, float should be continued, but at a lower voltage. This IS temperature compensation; something I have failed to take seriously, in the past, but will be much more diligent to put into practice in the future.

Contrary-wise, in cold weather, batteries self-discharge slower, and therefore floating may not be as important. This is the time when discontinuing float may be indicated.

This is all about VARIABLES and GRADIENTS

No, 13.71 volts is NOT an appropriate AGM float voltage for 35c. Nor is it recommended for 5c like it was here on the Baja California peninsula this morning.

Mena, is going to be boondocking when I am strumming a harp (or shovelling coal). My sdvice is to keep things in perspective. Some of you are fervent believers in playing the temperature compensation like it is a Stradavarius. It's more like a Yamaha violin.

When the battery goes with me to Michoacan, I will yawn and stick a 75-amp schottky rectifier inline and drop the voltage. But I'm not going to jump out of the toad and do it the moment I arrive. Areas where temps vary 40F or more are need T.C. But I woukd not get a case of diarrhea if the battery had to endure , 3 - ,4 volts deviation + - from "optimum". Temperature compensation is important but keep it in perspective.

Y'all in the hot weather areas need to convert your batteries electrolyte to "Tropical Blend" during the hot months. ie, top the electrolyte off good and high with distilled water and keep it up there near the upper limits during the warmer months to dilute the SG a bit and save the lead/antimony plates.

Whenever it's hot, you have to consume more water. Why would batteries be any different?

The more I think about that problematic T-1275 and top charging and needing 15.0V to get it top charged, slowly, the more I realize that a balanced 1 watt to 1 amp hour of battery ratio for my solar panel, battery, and an adjustable Voltage charge controller provide exactly what the battery prefers and needs, a slow steady charge, not a blast at 30 amps from my Mega Watt and generator.

But sometimes, when the sun don't shine, you gotta do what you gotta do. Electricity at night stored in the jars is more important than life of battery being a minute bit of months or days longer. Not too important in the grand scheme of things, unless pan handling or on food stamps, me thinks, for the majority of us.

Niner, thought about tropical blend but it gets cold (currently 22F...temps can swing 40F in just a day here) in the winter, I'd have to change blends twice a year. I'd rather just drop/raise float voltage.

jrnymn7 wrote:
Therefore, if floating is so important, it is contra-indicated to stop floating them at such times.

As far as I know, the purpose of properly done floating is to provide just the right amount of float voltage ("electrical field") so as to drive the electron transfers necessary to compensate for internal energy loss ("internal discharge") inside the battery. Since electro-chemical reactions are not "digital" (except at the discrete particle level) - but for all practical purposes happen "smoothly" via continuous processes - some amount of float is probably always necessary to replace the internal loss of energy that is always going on.

However, as you say, the rate of this internal discharge varies with temperature because electro-chemical reactions are temperature dependent and are also "driven" by the electrical fields that voltage establishes. With higher ambient temperatures (around the battery), a weaker electrical field (less voltage) is required ... with lower ambient temperatures (around the battery), a stronger electrical field (more voltage) is required.

What all this means is that, on hot days one should reduce battery float voltage the proper amount or you'll have too much of it and go beyond what's necessary to only compensate for internal discharge. You then risk boiling away the water in your batteries. In my case this is a no-no, since my batteries are AGM and boiled away water can never be replaced because it escapes via a one-way valve.

Since my batteries' float voltage is merely the ~13.8 volts from my RV's Parallax converter, I "kindof manually" control their float voltage versus high ambient temperatures by disconnecting them from the converter when it "kindof feels hot" outside. So far this by-guess and by-golly aproach has gotten over eight years of good performance from them.

Maybe I'm just lucky to have wound up with batteries that are easy to get along with ... or maybe my not obsessing over my batteries has charmed them into good behavior in spite of what I do. :h

I see batteries as being a lot like the human body. Amazingly, both can withstand a lot of abuse. But some damage is reversible for the most part, while other damage is not. So, I don't think any of this is worth obsessing over. But at the same time, some very simple rules do apply, and these rules can be best adhered to by using an adjustable unit. I just cannot see any downside to using an adjustable psu, while I see many downsides to using non-adjustable pre-programmed charging devices.

So, dollar for dollar, and with user ability factored in, it just makes good sense to go adjustable. And thankfully, guys like Randy at bestconverter, and John at MW, are seeing this, and are taking the necessary steps to address these issues, which for way too long a time, have gone ignored. And it's high time most rv manufacturers got up to speed and realized there is no 'one voltage fits all' solution. There simply is no room for such gross compromise when it comes to battery maintenance.

Niner, pure fast charging is a loser. Battery plates are a lot like the texture of a coral reef. Spongy incredible amount of surface area. Electrons and chemicals have to have enough time to revert sulfation, and pure super fast charging ain't gonna get the job done.

This is the reason for Top Charging. Keep it at FIVE PERCENT amperage rating of the amp hour capacity of the battery. Top charging is an excellent viable idea used in conjunction with solar panels. No generator run-time.

I run into solar systems, big ones that hammer lots of energy into the batteries. But the time quotient is ignored. The only answer is "Top Charging Day". Reduce load the night before and use the following day for the top charge formula. Some solar owners pschaw the idea. Battery vendors love 'em and wouldn't have it any other way...