Rudman Regulator

Rudman Regulators

Rudman Regulators come in lots of versions. All of them offer two basic functions. They sit on top of a battery and clamp its voltage to some maximum, keeping it from being overcharged. This is accomplished by shunting power through a resistor on the regulator. They also optionally send a signal back to a Manzanita Micro battery charger (or other charger) telling the charger to cut back its current because one or more batteries can't accept this level of charging current.

All versions before the MK2-D and the MK3 are no longer available.

The MK-1 versions were relatively simple.

The MK-2 versions are much more feature-rich than the MK-1 versions. They allow the user to set the clamping voltage and the voltage considered "too low." If the "too low" voltage is ever encountered, a red LED lights up and stays lit until the battery is fully charged, as evidenced by the voltage clamping circuit engaging. The voltage clamping circuit lights a green LED when it is active. Furthermore, the MK-2 regs can accept a signal from the charger indicating that the clamping voltage should be raised 10% for an equalization charge. When this is turned on, typically by a DIP switch on the charger, the reg turns on a yellow LED. Lastly, the MK-2 series of regulators have a header for an external temperature sensor and an external load, which is turned on when the clamping circuit is engaged.

The MK-3 versions use an embedded microprocessor to do most of the things that the MK-2 series did, except for the external load. A user can connect a computer (or other device) to the string of regulators and collect data from them, vastly simplifying the task of monitoring a battery pack.

The MK-3 regulators respond to a set of commands, which can be entered directly from a computer running a terminal emulator program. Windows XP, for example, comes with "Hyperterminal" which is an example of such a program. If you already know all about terminal emulators, consider this as an example. If you don't know what one is, find a computer running XP and go to Start->All Programs->Accessories->Communications->Hyperterminal. Choose a COM port that you have a "null modem" plugged into. Set the baud rate to 9600. Set the format to 8-N-1. Connect the null modem cable to the adapter that is connected to the regulator string.

All commands follow a two-digit number with no space between them. The two-digit number identifies the individual regulator in the string. Using the number 99 addresses all the regulators simultaneously.

The commands are as follows:

voltage - Displays the current voltage of the battery that the regulators sits on.

Example: 01voltage returns 01V 13.83V

status - Displays the current state of the regulator, including which features are turned on or off and what is currently happening. The result is a two-digit hexadecimal number. Each bit means something.

The definition of the bits is as follows:

Regulator Disabled - 0x80 Shunting Current - 0x40 Battery voltage is too low - 0x20 Battery voltage is too high - 0x10 Battery voltage has been low - 0x08 Regulator is too hot to function - 0x04 Battery temp monitoring enabled - 0x02 Statistical collection enabled - 0x01

temperat - Displays the temperature of the regulator

v2volts - Displays the voltage on the V2 header, which can be hooked up to anything the user likes, so long as the ground is the battery ground.

v3volts - Displays the voltage on the V3 header, which can be hooked up to anything the user likes, so long as the ground is the battery ground.

sethigh - Sets the voltage at which the battery will be clamped by the shunting circuit. As long as the regulator can dissipate enough energy through its resistor, it will keep the battery from going above this voltage. If the current is too high, then the regulator will overheat and shut down. To keep this from happening, the regulator will signal to the charger to cut back its current whenever the battery is above this voltage.

Example: 99sethigh 14.80

Note: The regulator is programmed (as of firmware version 4.07) to take into account the fact that lead-acid batteries will show different voltages under load at different temperatures. Because of this, accurately predicting state of charge of a battery must take into account the temperature it is being charged at. The MK-3 regulator automatically does this, assuming that the clamping voltage you specify is that for 70 degrees Fahrenheit. If the battery is above 70F, then actual clamping voltage will be somewhat lower. If it is below 70F, the clamping voltage will be higher.

Further note: The MK-3 regulator (as of firmware version 4.00) is programmed to dissipate some energy before the battery reaches its clamping voltage. This increases the amount of battery balancing that can be done in a single charge cycle. If you watch the regs during charging, you may see them light their green lights without signaling to the charger to cut back the current. This is normal and expected, and even a nice feature. When they reach the actual clamping voltage (again, temperature compensated) then they will tell the charger to cut back.

Final note: Temperature compensation is much better with the external temperature sensor installed. Without it, the regulator guesses that the battery is at the same temperature as the regulator if the regulator hasn't dissipated any power in the last 20 minutes. To make this work well, two things must be true. The external temperature monitoring must be disabled (with the btdisabl command) and the regulator must be mounted on or close to the battery.

setlow - This command sets the voltage at which the battery is considered "too low."

When the battery is too low, the red LED will be lit solid and the charger signal to reduce current will be asserted. The charger signal can be used to signal a motor controller to reduce output or, in the case of the Manzanita Micro Plug-in Prius conversion kit, it causes the boost battery to momentarily stop sending current into the Prius.