high current voltage regulator

Are you sure you want to cook the batteries at 16.5V? How much extra usable capacity do you get? The whole purpose of the charger is to PREVENT overcharging.

If you insist, wouldn't it be easier to just fix the inverter?

Once built a current dump load using a PWM, some big resistors and PIC. Avoids all those nasty voltage drops in series with the solar panels.

You'll probably get better info on one of the alternative energy groups. mike

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When

I am

regulator that

You can buy a 25A bridge reectifier for under $3.00. When you short the

• and- leads, the ~ leads will drop at least 1.2V, more as the current goes up. The polarity doesn't matter, of course. Or you could use 1 or

2 rectifiers in series, each dropping about .8V depending on current. butthey're probably more expensive than the bridge. A 1N1188A 35 amp stud mount is aboutthe same prices as the bridge, but you need two of them.

For some odd reason the bridge rectifiers are priced oddly compared to the rectifiers. 1A, 3A and 6A rectifiers are $.04, $.12 and $.22 apiece. Those prices hover around a nickel an amp. But the prices for bridges hover around a quarter an amp, and don't drop as quickly at higher currents.

The manufacturer recommends 16.3 v for several hours, I just pulled the

16.5 out of my tortured memory.

No "charger".

It came that way, I assumed it was some sort of 'protection', not a manufacturing flaw.

Irrelevant, the point was to regulate the -voltage- across the inverter, while simultaneously topping off the batteries.

Since this is "components" and the regulator is one, I foolishly assumed...

Laurie

Shutting down at 14.1 volts is correct for 12-volt lead-acid batteries. I wouldn't change it.

I think I misunderstood the question. A charger should shut down (reduce its current to a trickle) when the battery reaches 14.1 volts. Or are you saying that an inverter (that takes the battery's output to higher-voltage AC) is shutting down when its input is over 14 volts?

Could that be due to the fact that the bridge is (nearly always) going to be used at a 50% duty cycle, while discrete diodes might be used at

100%? [And there's probably some packaging savings...]

I think you want to look for a solar charge controller, rather than a voltage regulator. It's a simple matter to make a regulator with an LM317 and pass transistors, similar to this:

(The circuit shown woud have to be modified for your use) The problem is that your energy source is solar, and the panels may not (probably do not) produce enough voltage for that kind of circuit.

For a solar charge controller, you really want an inverter style supply, which can produce the required charging voltage even when the panels can provide a voltage well below that.

Finally, and *most* important: you need to know the charging requirements of the batteries if you are going to make a regulator to charge them. "Around 14 volts" sounds more "right" than "several hours at 16.3 volts" , but neither one instills a lot of confidence. I believe - but do not know for sure - that in solar systems a periodic overcharge (called an equalization charge) is sometimes recommended. That should certainly not be done on a regular basis. 16.3 is an overcharge - perhaps it is that equalization charge I've heard about.

Ed

am

... snip ..

If I recall.. an equalization charge has to do with UPS systems. Uninterupable Power Supply with alot of 2V batteries, or cells. Some cells will be lower in votage and some maybe higher.

1.95 ... 2.00 ... 2.3 ... 2.01 ... 2.00 You apply a charging voltage of 2.25 volts to all the cells. The charging voltage is the equalization charge voltage. You are bringing all low cells up in voltage and the hi cells down, till all the cells are at a certain voltage, fro the whole UPS system. I'm sure of the 2.25 volts, maybe I'm wrong on this, just some number in my head rite now.

When

am

that

You can use 2 higher rated diodes, or you can use a bridge rectifier that has 4 diodes in the package.

ebay , BRIDGE RECTIFIER 25 AMPS NEW OLD STOCK , $1.00

When

inverter I

The 2.25V is the float charge voltage; eq V is a bit more, like 2.3 or so. But most UPSes don't have parallel batteries, they are in series. So enough current is run thru them all to give the eq v across each, which means that the cells with higher V are also overcharged.

"> But most UPSes don't have parallel batteries, they are in series."

I had to look , so series / parallel UPS , google has 190,000 hits

Alpha UPS units use both series and parallel combinations... http://206.131.241.58/ubb/ultimatebb.php?ubb=get_topic&f=1&t=002710

"Connecting your Batteries in Series or Parallel"

Series-Parallel Connection with a 12 Volt 1 Amp BatteryMINDer

+186,000 web links to go for Series/Parallel configurations. Seems there's more ways to skin a cat.

The battery faq is,

CAR AND DEEP CYCLE BATTERY FREQUENTLY ASKED QUESTIONS 5.2 ,

Battery Tutorial ,

It looks like the 14 volts is what's suppose to be there. If you over charge a battery with more than 14 volts, you might risk damaging the battery. Aren't deep cycle batteries expensive?

Ed

For a 12 volt lead-acid battery, 16.3 volts is an equalizing charge, and should only be done occasionally. Normal bulk charging is done at up to 14.4 volts (or so, depending on temperature). As the battery approaches full charge, the voltage should be reduced to a "float" level of aboout 13.7 volts - otherwise you'll boil off all the electrolyte.

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I have but a single question...

Why do you think that it's stupid that the inverter shuts down at 14V?

I think it's smart enough to realize that you're cooking your batteries at

16.5V.

Do you?

BAJ

As I understand it, the equalizing charge is intended to mix up the electrolyte. In a flooded-cell lead-acid battery, the electrolyte can "stratify" into layers of different density - high-density high-acid fractions at the bottom, and a more dilute electrolyte at the top of the battery. This stratification can impair the battery's ability to charge and discharge properly. The equalizing charge _deliberately_ pushes the battery into electrolysis, breaking down some of the electrolyte's water into hydrogen and oxygen. The resulting plop-plop-fizz-fizz stirs up the electrolyte and de-stratifies it.

The cost of doing this, of course, is a loss of water in the cells. The battery's gas-recombination catalyst _might_ be able to recombine all of the hydrogen and oxygen into water, but I suspect that it usually can't keep up with the gas flow and that the excess gasses are lost.

Again as I understand it, gel cells do not require equalizing, and AGM (glassmat) batteries neither require it nor can tolerate it (they can be damaged by high charging voltage). I don't think I'd equalize- charge any sealed lead-acid battery unless the manufacturer specifically recommended doing so and gave explicit instructions on voltage and duration. Over-pressuring a sealed battery case could have nasty results.

One manufacturer of deep-discharge flooded-cell batteries suggests one equalizing charge per 10 deep discharges.

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