connecting batteries in parallel or series, myth and theory

| I think another key point is how often the batteries are fully recharged as | well. In Neon John's use of a golf cart, I would bet that he recharges the | thing every day or so depending on how much he uses it. Recharging from | grid power through a dedicated charger is pretty straight forward and not at | all hard to get a full charge overnight. | | But a solar installation may not have quite that luxury. A partial | discharge each day for a couple of days, followed by only a partial recharge | might be more problematic. A couple of cloudy days, and although the | batteries are not fully discharged, the chances are that one sunny day will | *not* put back all the charge.

In cases of a long period of autonomy, once the energy flow is back, but you do not know how long it will stay back, is it better to grab all you can and charge fast, or stick to the slow charge, knowing that if the energy quits before a full recharge, you could be discharging again from a point of not having gotten back to full charge. Part of the question is what is the effect on a battery/cell of sitting for some length of time at less that full charge, even if not discharging.

| Seems that type of duty is a lot harder on a battery than even 'typical' | golf cart usage. | | Unless of course you want to buy a lot more solar cells so you *can* | recharge the battery in one sunny day ;-)

But is that wise?

I could average out what my typical sun/wind energy input is over a long period of time, like a year, and what my usage would be, and size the PV arrays and windmills to provide all the energy I need, plus a reserve. But that does not size the batteries. If the batteries might need a quicker charge because the effect of sitting for time in a low charge state is worse than a fast charge, then I have to up the energy input size to deal with the batteries.

And of course all this is done statistically, since we cannot reliably predict how long these periods of energy availability and unavailability will be, as the Earth warms up and changes its weather and climate patterns around rather significantly in some places.

My personal experience is getting >95% of my home energy from solar and wind, and choosing a first set of batteries that's lasted 13 years so far. Beyond that, I live in an area that has thousands of off-gridders, and I take every opportunity to visit. I've probably seen >100 off-grid installations, such as the one I mentioned above. Some are really low-budget and many have had multiple owners. Even so, I've never personally seen, or even heard of anyone, who's been through as many batteries as you have. 5 sets is a record as far as I know, and that's assuming that 5 is the real number and not another of your prevarications. Considering that and your penchant for posting nonsense about batteries (samples available here

Wayne

here

How about because I'm right. Parallel batteries in a system use for home power is a waste of time and money.

In alt.engineering.electrical N9WOS

More to the point is how low the batteries charge is for a given time period. This is part of the calculation for days of autonomy. Personally I always charge my batteries if they get to 12V. Reason, it takes less time to bring them back up to better than 90%.

Run them up to 17V.

Again, that depends:

Notice the chart with the traditional three stage charging table.

In a number of cases the newer more sophisticated battery chargers will sense the condition of the battery/ battery string and apply their own charging algorithm. ( It can be a matter of trading a little money for a simpler more automatic maintenance requirement.)

Luck; Ken

P.S. There have been claims for battery desulfication schemes from day one. The high voltage pulse approach is often part of such efforts. I haven't heard of where anyone I would believe, has had any luck with such gadgets. Anything that actually works is/would be incorporated into the better chargers. (Some of them are pure snake oil, IMHO.)

Yep, just what my regulator does.

Give examples of diodes that are not rectifiers.

Phil,

I don't have science based information here.

It seems that, in addition to periodic 100% charges, periodic equalizations (controlled overcharges) are also required.

Surrette recommends equalization if battery specific gravities should vary by more than 0.015 between any two cells in the bank. And they also present, on their web site, recommendations for voltage, how often, how much, etc.

Also, for batteries that have become severely sulfated, I have been told by one of their tech support people that a prolonged equalization (as in days to weeks), along with careful monitoring of temperature and fluid levels, can often recover a severely sulfated battery. He stated he had done this personally.

--ron

George says that he would never use paralleled batteries again because the practice led to failure. And yet we know from his other writings that he's on his 5th set of batteries, and that others get longer life out of the very thing he rails against - paralleled GC batteries. Therefore, the failures must be due to at least some other issues. Here are some clues in his own words: "I float my 840Ah batteries at

As well, George believes that there's hidden capacity in some batteries. The maker of his batteries specifies a low-voltage cut-out of 11.5V.

All things considered, it's no surprise that Ghinius George Ghio holds the record for most dead batteries, and the cause has little or nothing to do with parallel strings. Wayne

It was *designed* to do a proper 3-stage charge, but you "subverted" that functionality in favor of single-stage. That was a dumb idea, although not quite as senseless as holding the record for dead batteries and pretending to be knowledgeable about battery maintenance.

Wayne

here

LOL That "ignore my undeniable foolishness, believe what I claim" position seems to be your answer for everything. Here's a clue for you: the market for home power is in a stage of unprecedented expansion. And yet you, the self-titled "power consultant", after decades of trying to make a living in the trade, are still getting more than 95% of your home energy from anything-but-solar, still need to start a generator for even minor loads like laundry, and still need to find another career to bungle. The joke is that there's so much work out there that even a screw-up ought to be able to find a niche. But it takes a true Renaissance nitwit to write a ton self-busting foolishness into a permanent, searchable, public archive.

Wayne

In alt.engineering.electrical snipped-for-privacy@citlink.net wrote: | On 17 Aug 2008 20:05:35 GMT, snipped-for-privacy@ipal.net wrote: | |>In alt.engineering.electrical snipped-for-privacy@gmail.com wrote: | |>| The very first battery bank I ever set up was a parallel string affair |>| and I did just that. Total waste of time. |>

|>And I presume you would never, ever, do that (install a parallel string) again, |>even though you don't know any of the physic behind it, simply relying on your |>experience of the end results of the way you did it, without really knowing if |>the problems were from the parallel aspect or the way you did it. | | George says that he would never use paralleled batteries again because | the practice led to failure. And yet we know from his other writings | that he's on his 5th set of batteries, and that others get longer life | out of the very thing he rails against - paralleled GC batteries. | Therefore, the failures must be due to at least some other issues. | Here are some clues in his own words: "I float my 840Ah batteries at | 15 volts(PL40) This makes the batteries bubble quite well" |

| "I will tell you that the reason I subvert my regulators three stage | default setting..." |

He should recycle his leftover lead, if it's not too terribly contaminated. Sounds like he probably has a lot of it.

| Also, for batteries that have become severely sulfated, I have been told by | one of their tech support people that a prolonged equalization (as in days | to weeks), along with careful monitoring of temperature and fluid levels, | can often recover a severely sulfated battery. He stated he had done this | personally.

So one would at least need some kind of redundancy system, to do this, if they are off-grid.

So far as periodic equalization, you just need some period of time with excess energy.

I occasionally have these periods during the summer, and they are not unusual during the rest of the year. They are more common in the late fall--early spring when we have the occasional "three day blow".

I would not do a prolonged equalization unless it was during one of these times. And I don't know that it has to be done "all at once". Perhaps

You probably won't be able to equalize continuously for days, anyway, because the cells may get too hot.

I have a hybrid Wind-PV system with a propane generator for backup.

--ron

You should be able to operate your battery bank and never see a "severely sulfated" battery. This is a case where "an ounce of prevention..." is likely to be all that's needed. Modern charge controllers and the simplest routine/scheduled maintenance should maintain a good balance and give you a longer lifespan for your batteries.

Of course, any drastic changes in the charging or discharging of your system, should be a reason to consider how the batteries may be effected, and appropriate action/ additional maintenance taken.

(Say a Hurricane knocks down your wind generator, and can't be or isn't replaced for months. Or there is a lot more use of the system than originally planed on, and there is insufficient charging to keep up, on a regular basis. You might need to use a gas generator to maintain the battery bank. )

If the situation becomes chronic then you need to redesign your setup. ( This might involve adding storage capacity and could well involve adding a matching parallel string to your existing setup, it would not mean any disaster is more likely. )

Some reasonable operating/maintenance schedule applied as a part of your weekly routine, will most likely prevent any problems developing. It's where people never bother with them, at all, until some problem develops, that allows the appearance of such conditions. It need not be any more lifestyle changing than adding a caged pet to your life, forget to water them or clean out the cage on a regular basis, and you will have problems.

Luck; Ken

I agree 100%, and should have mentioned that in my response.

--ron

Equalization should be done based on the hydrometer readings of your cells being out of whack. As a scheduled activity most advice I've seen suggests once every six months. These types of routine equalization only last 1-3hrs. Any time you are so severely overvolting the batteries you NEED to be closely monitoring the batteries, especially the temperatures, and MUST suspend charging until they return to normal temperatures, before continuing the equalization. (The equalization process stresses and shortens the lifespan of a battery, just not nearly as much as allowing the sulfide buildup.)

You should never have a battery so badly sulfated that you need to try any equalization over a couple hours. But if someone gave you some (from their neglected system), you could try a long term equalization, monitoring closely and suspending charging as required ( I would rig a thermal shutdown and restart, and do the job outside the house or garage, in a shed.) These "recovered" batteries would have a shortened lifespan as a result of the process, but if you got them for free or cheap enough, it might be worth the trouble.

Luck; Ken