Thermistor Temperature Compensation For Megawatt

Nehhhhhh.....

If you want the genuine article here is some jan-you-wine Woghash..


"Most lead acid battery additives contain EDTA, or ethalene diamine tetra acetic acid has always been known to dissolve the lead sulfate layer on the plates. There are, however, two downsides to this: EDTA usually comes in powder form, or as a solution. With manufacturers tending to favour sealed maintenance-free type batteries, there is no chance to introduce EDTA to the battery in the first place. EDTA works by forming a complex compound with the lead sulfate layer on the plates. While this removes the insulating layer, the active material that had formed lead sulfate will not be reconverted once the battery is charged.

In principle, the insulating layer of lead sulfate is removed, but active material is sacrificed in the process. EDTA reacts with the lead sulfate to form the complex compound above. The plates are cleaned, but active material is not returned to the battery. Complex compound formed by breaking the lead sulfate bond. Battery life is extended temporarily with the removal of the lead sulfate crystals and increase of reaction surface area, but the lifespan of the battery cannot be maximized unlike using our Desul..."

You need to order a couple of these and then you can go back 30 years..

http://www.oreillyauto.com/flux-capacitor.html

MEXICOWANDERER wrote:
Well, it's like this...

I want that 11 position, snap break-before-make switch with resistor array

Configured for AGM and flooded battery voltage span.

The Megawatt voltage divider uses a convenient 10 ohms per tenth volt calibration factor.

An ON/ON 5 ohm primary bias switch can halve the resolution doubling the count to 22 positions.

While an ON/ON/ON switch can select thermistor, 11 switch or all-out 16.13 0 ohms charge rate (for equalizing).

Yeah - yeah I can use a low resistance Bourne pot to bias thereby configure the Thermistor circuit.

**** I can only wish this stuff was around 30 years ago.

:B

Well, it's like this...

I want that 11 position, snap break-before-make switch with resistor array

Configured for AGM and flooded battery voltage span.

The Megawatt voltage divider uses a convenient 10 ohms per tenth volt calibration factor.

An ON/ON 5 ohm primary bias switch can halve the resolution doubling the count to 22 positions.

While an ON/ON/ON switch can select thermistor, 11 switch or all-out 16.13 0 ohms charge rate (for equalizing).

Yeah - yeah I can use a low resistance Bourne pot to bias thereby configure the Thermistor circuit.

**** I can only wish this stuff was around 30 years ago.

I still don't see why you don't just stick a digital pot in there with an Arduino measuring current, voltage, temperature and time.

From that explanation, I would guess that the factory pot is connected (on the high side) to a fixed DC voltage source, typically 5VDC. The low side is connected to common (ground) and the wiper arm picks off a DC voltage between 5 and 0, and injects it into the variable voltage source to adjust the output. Very typical for a DC power supply. Your plan is to replace the pot with a temperature variable resistor to control the output via temperature. I would think that a series combination of two thermisters connected from high to low, with the center point of the thermistors connected to the injection point would also work and would give you more variability. Just thinking out loud, so to speak.

The Megawatt like most Meanwell clones, uses an accessible 1-turn potentiometer that ranges from around 11.5 to 15.5 volts.

By substituting a thermistor within the unit's voltage divider network the sensing system becomes thermally oriented.

By actually working on the units I found the inverse operation (lower the resistance the higher the voltage) has a fundamental useful voltage span that correlates to 280 ohms max down to whatever resistance / voltage level a user desires. In theory a wider scope thermistor can be used to control floating voltages from -40FC to 122F 50C.

The setup is simple - removal of the original pot, solder a length of twin wire with a quarter watt carry potential (24 gauge would be useful to around 60' total back and forth length - meaning a 30' distance between thermistor and float charger.

The beauty of this is that the thermistor could be switched in and out of circuit with a simple ON/ON switch. I am ordering a 16-position single pole click-click switch today, which would allow quite a span in voltage. One side of ON would be thermistor control, the other ON, a manual control. Of course a multi-turn pot can substitute for the click-click switch.

For that matter, another clicky switch can be used as a pull-up with inline resistors for the thermistor. Six ohm increments, and three positions could bias the thermistor. Maybe .1 volt increments negative to plus. It all could be contained in a module with voltmeter and one of Mr. Wizards inductive ammeters.

A fun project.

Do I understand correctly that you want to build a variable output, 36 amp charger, using something like an IGBT or SCR, that is controllable, and you want to use a thermister to provide the controlling input to the charger? The controlling action will be based on temperature or else a variable voltage output?