high current voltage regulator

The simplest solution may just be a load bank that switches across the batteries, just before the inverter kicks off and switches off at just a bit lower voltage. Heat is easy to get rid of.

It shouldn't take too many watts to load the solar bank down from 16+ volts to 14+ volts.

Hi Laurie,

You wish to drop 2.3V at 15V, so about 34W would be dissipated by a linear regulator.

If you're happy with dissipating 34W, the best solution may be a 3 terminal regulator with an outboard pass transistor. A linear regulator would be easy to implement. You would want to be careful with protection and current limiting. You may also need to worry about the dropout voltage of the regulator when the battery voltage is about 14V. Perhaps a relay could be used to bypass the regulator when it isn't required. Look at the LM317 datasheet from national - there are some application circuits which may interest you.

A better solution would be a "buck converter" - a type of switched mode regulator. This type of converter is harder to build (you need to switch highish currents fairly fast), but would be far more efficient.

I think there is an introductory description of switched mode regulators in "The Art of Electronics" by Win Hill and Paul Horowitz. There are very good application notes covering the topic on the Linear Technology and Texas Instruments websites.

Regards, Alan

Yes! I agree with the shunt regulator has some problem with heat dissipation. I think you should try the series regulator. But the regulator should use good MOSFETS, otherwise will also has the same problem. But the big advantage for series regulator is no short current for solar panel. For your inverter to shut down at 14V, I think this is better for your battery otherwise if the battery charge at high voltage will make the lifetime shorter. Normally at 25 degree the charge voltage should not above 13.9V. But for boost voltage the voltage can keep for 14.5V for some hours. This depend on the state of your battery. If you want your battery has long lifetime you should use some professional regulator. I can introduce you some products if you are interesting. Regards, Feng

Unfortunately under embargo, I have the schematic for a solar regulator which will do better things for your batteries and not irritate your inverter. The device is a Solarex SC-18 and costs ~$A150.

The reg is a series switch which cycles between two limits - let's call them V+ and V-. When sun disappears and voltage drops below a lower limit V- - a latch is set, and on next appearance of sun the switch stays closed until a higher threshold V+ + is reached, then the device cycles between V+ and V-.

This "daily" boost trip to V+ + is intended to help destratify the electrolyte.

All four set points are adjustable.

I have no commercial affilaition with Solarex, just a very happy user of many of these devices. We found that MANY microprocessor designs created so much RFI that they were banned from our radiocommunciations sites in favour of these KISS devices.

Shunt regulators are a problem with their heat dissipation, which increases as the battery SOC rises.

Just my 2c worth.

V * V = W?? Oh, wait, that is "square volts"; things sure have changed since I taught myself electronics with the help of Popular Electronics in the '50's.

Actually, fumbling through their data sheets, I found the LM338 which can handle 5 A, and a circuit that parallels two of them: DS009050-2, so that will do it.

Laurie

Sorry - my error. What I meant 2.3V at 15A. Hopefully this was pretty clear from context (and dimensional analysis, as you have pointed out).

Ensure that you have suitable heatsinking to keep the devices at a sane temperature. It seems quite sad to use such an inefficient regulator in a solar powered system.

Regards, Alan

Am planning to use a Peltier heat pump that conveniently operates on 12 v DC between regs and finned heat sink.

Any more efficient approaches would be appreciated.

Laurie