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On Feb 16, 3:20*pm, "Percival P. Cassidy" wrote:
On 02/16/11 10:15 am, raypsi wrote: snip ... I built a flooded lead acid charger. I only bought one part the IC UC3906, I already had a solderless breadboard, the resistors and capacitors in my junk drawer The hardest part was figuring the resistor values and how to make those values, and that was easy. The heatsink fan came from an old CPU fan heatsink, and I mounted the pass transistor to that heatsink fan. I think that the UC3906 was the best think since sliced bread I've seen schematics and board layouts for SLA chargers based on the UC3906. VK3EM's uses SMT components, while N5BIA's uses discrete components -- but both are only for charging currents of 2A or so. For what current did you build yours? If high-current, what pass transistor(s) did you use? N5BIA offers a kit, and I was wondering whether this could be beefed up to handle 25A by adding 12ga wire to all the charging-current traces and substituting higher-current pass transistor(s). I'd have to recalculate the resistor values to suit a flooded battery, of course. And what about using a P-channel MOSFET device, such as the STP80PF55 that the "Micro M+" uses? "Perce" There is no design on the internet for charging a flooded lead acid battery at the levels I use. There is a reason for this it's called lithium ion cells. I used to make a living selling NTE parts. NTE always bought the cream of the JAN type transistors, so they could sub tonnes of transistors with one number. When the regulator went south on my car alternator I used a NTE180 to drive the field winding with a zener regulator I mounted the heat sink right to the positive side of the battery; when that car died the day the big tsunami hit back on boxer day 2005 I took the NTE180 out. I use an NTE180 30 amp PNP transistor and 1 foot of 14 gauge wire to set up the main charge current, I use a 23amp PS from the filtered unregulated side to the input of the 14 gauge wire to collector of the PNP. the UC3906 looks at the voltage across the 14ga. wire and directly drives the PNP. I snake the wires for the emitter and base of the PNP thru the heatsink fins. I used the TI data sheet for the UC3906 to calculate the settings for the different charge cycles. The 14 ga wire and the pass transistor are the only off the solderless board parts I wound the 14 ga wire in a pancake style coil so it fits right over the heat sink I had to use single turn trim pots and series resistors to set the different charge cycles from the equations provided by the data sheet on the UC3906 I did alot of research on my power supply, the others that used a UC3906 on the internet could not be used to recalculate the resistor values for the UC3906 for a large flooded lead acid battery. There were to many mistakes as I found out. Using the TI data sheet, is the best way to go, it looks like rocket science but it's easy.\\ 73 OM de n8zu |
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