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This page is dedicated to the PFC-30 charger from Manzinita Micro.
Installation of the PFC-30 Charger
December 2005
The first use of the PFC-30 Charger was to test the charger on the test pack.
Using the install instructions from Manzinita Micro the setup was quick and easy. All went well.
The PFC-30 charger is light enough to be installed on-board. It was decided to put the charger in the rear of
the vehicle, in the extra space at the rear battery box. This will help to reduce rear-end weight, as more batteries can then be installed up front.
Improvements to the PFC Charger
A few improvements to the PFC charger will ensure the charger is well protected, provides a consistent voltage, and ensures a safe installation:
- Protect charger if there is no output load connected.
- Temperature compensation (adjust voltage based on pack temperature) if not using the Rudman regulators.
- Extra NC/NO relay switches when charger is powered (used to disable ignition if charging)
- AC power present before power to charger is activated (prevents any power being at exposed contacts of charger AC input)
PFC Charger Control Circuit
The charger control circuit, is an add-on to the charger (or to most any charger), which provides protection for the charger and people:
- Protect charger if there is no output load connected.
- Temperature compensation (adjust voltage based on pack temperature) if not using the Rudman regulators.
- Extra NC/NO relay switches when charger is powered (used to disable ignition if charging)
- AC power present before power to charger is activated
...and the final result:
PFC Charger Temperature Compensation
To ensure optimal charging, the charge voltage must adjusted based on the temperature of the pack.
For the New Beetle project, two circuits are set-up to provide this ability:
- Battery Pack Heaters
Battery pack heaters, placed under the batteries in each pack, heat the packs during charging to maintain a (somewhat) consistent temperature.
- Modification to a single Rudman Regulator
Joe Smalley and Rich Rudman are working on modifying a regulator to provide voltage adjustment for the PFC-30 based upon battery pack temperature (March 2005). Until that is complete,
a simple thermometer, calibrated with a voltage scale is used to set the charge voltage:
Programming Charge Profiles with the PFC
The New Beetle will use 26 (312V Nominal Total) Deka Lead Acid Gel batteries from East Penn.
These batteries require the following charge profile
(from the MK Battery technical manual for Gel batteries):
- Bulk stage 1:
MAINTAIN constant current 3 Amps per 10 Ah @ C20. This is 18 Amps for the Deka 8G34M.
FINISH when end voltage is 2.30-2.35 volts per cell. This is 358.8 - 366.6 volts for a pack of 26 batteries.
STOP when timer exceeds 1.2 * DoD (Ah)/Average Current (A) hours
- Absorption stage 2:
MAINTAIN constant voltage of 2.30-2.35 volts per cell. This is 358.8 - 366.6 volts for a pack of 26 batteries.
FINISH when current acceptance is less than 0.1 Amps over one hour
FINISH if exceeds 12 hours
STOP if current exceeds 8 Amps after going below 6 Amps.
- Float stage 3:
MAINTAIN constant voltage of 2.25 volts per cell. This is 351 volts for a pack of 26 batteries.
Note: These voltages are for 20oC. The voltage should be adjusted based upon pack temperature:
for each 1oC above 20oC subtract 0.005 Volts/Cell (subtract 0.78 volts per oC for the pack of 26)
for each 1oC below 20oC add 0.005 Volts/Cell (add 0.78 volts per oC for the pack of 26)
In summary, for a 26 Battery pack (312):
- For the Bulk Stage, it is constant current of 18 Amps until end
voltage reaches 358.8 - 366.6 Volts
- For the Absorption stage, it is constant voltage of 358.8 - 366.6 Volts,
until acceptance current is less than 0.1 Amps over an hour or a maximum of 12 hours
- For the float stage (only required if batteries will sit idle for over 3 months), is to keep the pack at 351 volts.
The charging needs to be temperature compensated: subtract 0.78
volts/deg C above 20 deg C or add 0.78 volts/deg C below 20 deg C
The PFC Charger is a Constant Current, Constant Voltage charger, so can easily handle the Bulk and Absorption stages required for the DEKA batteries.
The voltage and amperage are adjustable through the front panel controls.
It also has a timer which can be set to start once the bulk stage has finished, to ensure the absorption stage does not run too long (max of 150 minutes).
Custom Profiles with the PFC Charger
Joe Smalley has published some documents on the Manzinata web site (Remote Control Questions and Answers) on how to modify the PFC charger and control its' power.
Caveat emptor: if you do this, you will void the warranty.
Reference
MK Battery Gel Battery Charging
MK Battery Gel Technical Manual
Operating DC Relays from AC and Vice-Versa
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