T-Pain Is On A Boat: Re: [Electric Boats] Re: Dual Pro Output current.

Thursday, July 22, 2010

Re: [Electric Boats] Re: Dual Pro Output current.

It would not be difficult to spec a transformer and rectifier for a proper load point, but tricky to avoid over-voltage without regulation. A large variac into a transformer/rectifier could be done with off-the-shelf parts, but would require manual adjustment to avoid over-voltage. For example, a practical (under 200lb 5kw) system loaded to peak output might drop 30v from a no-load condition. This drop would be the heat generated by operation under load. Conceivably, a transformer/rectifier could be specified that would run 60v no-load and 44v at peak output, but I would predict such a system would be quite massive. I had a transformer built for 120vac, 1:1 at 30a for galvanic isolation. It's a two man lift at 90lbs, yet just able to sustain 3.6 kw output to manage thermal losses.
A switching power supply would be more in line with modern technology. I found some used 0-100a, 0-100vdc power supplies at an electronics recycle yard. Running single phase 220vac, they can source 60 amps continuously. Unfortunately, power supplies are designed for a laboratory environments, not salty bilges. The 90lb isolation transformer is mounted in the bilge, albeit after a soaking in silicone potting compound (not to be confused with conformal coating).
Personally, I'm building a generator with a 5kw 48vdc output, and perhaps 12v house output. My proto-type is built on a Briggs vertical shaft 1.8kw gas engine with a downdraft carb. The regulation is done with a servo on the throttle. It works nicely with a load bank. I have not had it on a boat.

Be Well,
Arby
Advanced Marine electric Propulsion

From: Eric <ewdysar@yahoo.com>
To: electricboats@yahoogroups.com
Sent: Thu, July 22, 2010 5:06:27 PM
Subject: [Electric Boats] Re: Dual Pro Output current.

Pat,

Thank you for bringing this up. This may be a case of the smart charger being too smart. A battery under load could easily lead the charger to see a "damaged" battery, and better programming would shut things down before more damage occured.

Your suggestion of a simple power supply is excellent, I don't think that I've read a post here that has specifically made that suggestion. Do you know of any 1000W to 1500W 48V power supplies that are available to DIY folks like us?

Thanks,
Eric

--- In electricboats@yahoogroups.com, "greenpjs04" <greenpjs@...> wrote:
>
> The Dual Pro (PS4) is indeed capable of 15 amps per channel. If the 4 channels are wired in series (which they are if connected to 4 batteries in series), then it can supply 15 amps at 48 volts. I don't think the problem is one of overheating that was mentioned earlier. It is that the dual pro was designed as a battery charger. It has microprocessors that monitor the batteries. A motor drawing 15 amps at 48 volts does *not* look like a healthy battery to the microprocessors. The dual pro will shut down with an error because it is not making any progress charging the batteries. It knows something is wrong. If you want to run your motor from a 48 volt power supply, I recommend buying one rather than using a charger.
>
> Pat
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>