"Things that Work!" Home Power tests Backwoods Solar Electric's Battery Charge Controller Richard Perez Device Overview This battery charge controller operates in two modes. As series resistance to control incoming energy from any DC source. And as a shunt regulator which connects loads to the batteries in order to control system voltage. Steve Willey's battery controller operates either or both ways. The strong points of Backwoods Solar's controller are versatility and quality. Shipping Container & Documentation The unit arrived in fine shape via UPS. Documentation is very brief and could use more diagrams and pictures. After several readings and some head scratching, we got if figured out and installed using the documentation. Physical Examination The control box is 10.25 inches wide by 8.25 inches high by 4.25 inches deep. The unit contains two large analog meters. One is an expanded scale, 10 to 15 VDC battery voltmeter. The other is a DC ammeter that reads 25 Amperes full scale. Two switches which control the modes of the controller are located on the front panel. The front panel also contains three Light Emitting Diodes (LEDs) that indicate the status of the control system. I opened the box and examined its inards. The switches, connectors, printed circuit board, and the box itself are of the highest quality. All power handling components within the controller are rated at 30 Amps. The voltage adjustments for the switching logic are marked and easily accessible. Large, low loss, wiring bars are provided to interface the control with the rest of the system. A large silicon diode is well heatsunk for blocking purposes in PV systems. The box itself is made of heavy gauge steel, with louvers on the top, and a first class paint job. Installation & Test System We installed the controller between 155 peak Watts of PV modules and a battery pack of 350 Ampere-hours at 12 VDC. The controller was easily wall mounted using a few screws. Knockouts for wiring are plentiful on the bottom of the controller. These knockouts accept standard wire clamps for a "code sanitary" installation. The unit comes supplied with a low loss battery cable assembly with attached fuse. Control Operation There are two switches that set the mode of the charge control. The first, labeled CHARGE control switch, selects how the incoming DC energy is processed by the controller. The CHARGE switch has three settings: 1) it passes the incoming DC energy in voltage controlled mode, 2) it passes the DC energy in voltage uncontrolled mode. and 3) it disconnects the DC power source from the batteries. The second switch is labeled Auxiliary. The auxiliary selects how an auxiliary load is connected to the system's batteries. The Auxiliary switch selects between; 1) auxiliary load connected to battery when voltage is high, 2) auxiliary load connected directly to the battery, and 3) auxiliary load off. The logic of the control sets two voltage switching points. One switch point is for HIGH voltage, the other is the LOW voltage switch point. These actual voltage of these switch points is user programmable via two potentiometers on the control board. When the system voltage reaches the high set point two things happen. One, a resistor is inserted in series with the incoming DC power, thus reducing system voltage. Two, the auxiliary load is connected to the battery, also reducing system voltage. When the system's voltage falls below the low voltage set point, then the process in reversed, i.e. the resistor is taken out of series with the power source, and the auxiliary load is disconnected from the battery. In our experience the voltage switch points remained stable once set. The high and low voltage sensing logic, coupled with the two manual switches, offer six different combinations. These combinations fall into two categories, either series or shunt (parallel) control of the incoming DC energy. One may mix and match both these types of regulation to suit any particular system. This control will function in PV, wind, or microHydro systems with equal facility and effectiveness We adjusted the voltage sense points to suit our system and let the control do its job. When the incoming energy from the PV array produced system voltages above 14.5 V., then the controller reduced the array's current from 11A. to 4A. We also tried using the Auxiliary load function. When the PVs drove the voltage over 14.5, then the auxiliary load was added automatically to the system by the controller. We set the low voltage switch point at 13 Volts. When the system's voltage fell below 13 Volts, the resistance controlling the PVs incoming current switched out of series and array resumed its normal production of 10+ Amperes. Also, when the system voltage fell below 13 Volts, then the auxiliary load was disconnected from the line. The auxiliary load can be virtually anything-- a fan, a pump, a water heater, or whatever. With the charge switch set on manual, the series regulator is defeated and the incoming power is fed directly to the batteries. Even if this series regulator is defeated, the shunt regulator will still function. In other words the user can chose between four distinct modes of regulation: 1) series & shunt, 2) no series & shunt, 3) series & no shunt, and the transparent mode of no series & no shunt. In addition to these four regulation modes, the switches also offer the OFF state to disconnect the power source and/or the auxiliary load from the batteries. The ability to shut the regulators off and run the system without regulation is very useful and not featured on many controls. We tested the unit's meters for accuracy. The voltmeter was within 2% and the ammeter was within 5%, according to our Fluke 77 DMM. The unit was able to handle its full rated current without problems. No heat was detected where it shouldn't be during full current operation. Cost Retail price of this battery charge controller is $260. This is in keeping with the high quality of the hardware used and the basically "hand made" nature of the control's manufacture. Contact Steve Willey at Backwoods Solar Electric Systems, 8530-HP Rapid Lightning Creek Rd., Sandpoint, ID 83864, or call 208-263-4290 for more information. Conclusions We can recommend Backwoods Solar's Battery Charge Control as a "Thing that Works!". We liked its quality and especially its versatility. It can be used in PV, wind, and/or microHydro systems. This control's ability to become completely transparent and disappear from the system at the flick of a switch is great. Most controls don't do this waste energy when they aren't functioning. Our only complaint is about the control's documentation. A control with this much versatility needs more documentation to enable the user to realize its wonderful potential.