Hacking with the RENAVAIR Battery Charge Control Panel by Bob-O Schultze-KG6MM From time to time Home Power gets letters from folks with 24VDC systems bemoaning the fact that most of the DC appliances and controls available on the market are geared toward 12V systems. Well, listen up folks! This one's for you! God knows what sort of military machinery this panel was part of, but it originally ran on 24VDC. This charge control panel is just what it says it is, a panel with controls and instrumentation for starting, monitoring, and adjusting a 24V engine-driven (probably diesel) generator or alternator. Almost all of the components can be used on 12 VDC. Here's what you get: A nice 50 mV. @150 Ampere brass shunt with matching 150 Amp full-scale Crompton analog ammeter. A 0 to 40 VDC full-scale Crompton analog voltmeter, 2-ganged Heinemann 110 Amp @ 28VDC circuit breakers. A manual reset 2 Amp DC circuit breaker. A Hobbs hourmeter reading 0000.0. Since the Hobbs is not resettable, this is the surest indication that the whole shebang is brand new. The hourmeter works on 6 VDC to 40 VDC. 1-Ohmite 10Kê, 2 Watt potentiometer with a large knob. 3-Bosch 10/20A, Automatic resetting circuit breakers. 2-SPST toggle switches-heavy metal 1-SPDT toggle switch 1-SPST momentary with a big red button marked "STOP" 1-DPST momentary w/big green button marked "START" Two cool-looking chrome panel lights-shielded on top A big green bezel "Power On" light-ooh,ooh! A full-wave bridge rectifier and 6800uF @40V capacitor A "Fault Indicator" circuit board. This outputs to several small lights on the panel marked low fuel, water in fuel, low oil pressure, etc. A cast of seemingly hundreds of white (yes,all of them) wires with little make- you-go-blind numbers on them hooking the whole thing together. A heavy box about 15" X 10" X 5" with hinged front. All the meters, switches, lights, etc. are mounted on the hinged front. All this stuff is of the highest quality; just what you'd expect when the government is spending our tax bucks. All kinda nice stuff and a welcome addition to any hackers junque box, but if you really want to set up a 24V engine/alternator battery charger, whew! It's the kind. Here's how. A schematic for the Mark VI 12V alternator field controller was first published in Home Power #2. The schematic below is a 24V version of that circuit. Insert skiz First,THE DISCLAIMER- This is what I did to make the control panel that I had work. I'm guessing that all of them come from the same batch and are wired the same. After all, this stuff is military surplus so anything is possible. Check to see that all the wires go the same places that this one did. In the interest of safety and sanity, disconnect and remove any that you're not going to use or aren't sure of, OK? Remove the 10Kê Voltage Adjust potentiometer from the panel and replace it with a 1Kê linear taper pot. The knob should work fine. It will become R7 of the Mark VI. Remove the SPST toggle marked "Preheat" and replace it with a 100Kê linear taper pot. It becomes R3. The Heinemann breaker is set up to break both the positive and the negative battery-to-alternator lines. If you look at the back of the insulator, you'll notice that there are "+" marks on both terminals of one of the breakers and "-" marks on both terminals of the other. Bring your positive and negative leads in from the battery bank to the bottoms or "load" sides of the breaker. Remember that these wires will be carrying the full output of your alternator, so size them accordingly. All the seething mass of white wires should be on the tops or "line" sides of the breakers. If any aren't, put them up there, keeping the negatives with the negatives and the positives with the positives. Your Mark VI input wires go here also. The negative wire coming from your alternator goes to the top or "line" side of the negative breaker and the positive wire from the alternator connects to the lower side of the 50MV shunt. Connect the output wire of the Mark VI to the alternator field. Trace out (good luck!) or remove the wire from the upper side of the "Panel Lights" switch and connect a wire from there to the lower side of the shunt. Assuming that you've been living right and haven't angered to gods in some way, throwing the big breaker switch to "on" should activate the Mark VI, the volt and amp meters, the hourmeter, and the big green "Power On' light. Alright! Toggling the panel lights switch up should turn them on. The "voltage adjust" pot will control the upper charge voltage set point and the other pot will control the alternator amperage output rate. Have Fun! Access Author: Bob-O Schultze is the hacker and hydromanic found at Electron Connection/ Lil Otto Hydroworks!, POB 203, Hornbrook, CA 96044. ù 916-475- 3401. The Battery Charge Control Panel is available from Renavair Corp. POB 2110, Alpine, CA 92001 ù 619-445-7317. A complete panel is $119.95. The panel box without any components is $19.95. Most components are available separately.