Step down DC-DC

[chris piazza]

I have a NewMar 32-12-25 step down transformer that powers my electronics on the bridge. The output (12v) is wired to a dedicated panel by the engine room door with seperate breakers for all the electronics on the bridge. When all the electronics are on (two VHF's, chartplotter, sonar and radar) warning alarms go off for low voltage. The chartplotter and sonar have built in voltage meters which I watch drop as I turn more things on, usually by the time I get to the last piece turned on I am down to 11.7v which sets off the alarm. Don't even think about keying a mic on one of the VHF's because than it goes down to 10.5v. Batteries are good and fully charged. I think the transformer has seen its better days and is not reaching its full 25 amp capacity. I priced a new one and there not cheap, over $400 for a 30amp if I go up a step. I think the output has always been marginal. Any sugestions for a fix?

Chris
Superior Nights 53C

 

[davidwigler]

Check the voltage at the breaker box while under load. You might have voltage drop from marginal or undersized 12 volt wiring to the bridge. If so a 30 amp converter won't solve the problem.

If you have a waterproof place under the bridge, one fix is to move the 32 volt converter and 12 volt breakers to the bridge. The other solution is to upgrade the 12 volt wiring.

 

[sandspur1966]

I added a second newmar unit to that panel to double my capacity.

Also I recommend you call Newmar, they have really good tech support in my experience. I accidentally crossed terminals with a screwdriver and fried one of the converters, pulled it and sent it to newmar. They rebuiult it and had it back to me by the end of the week.

Also, I would keep an eye on ebay, I bought a newmar unit new for about half the factory price.

 

[Pascal]

I'd start looking at the voltage drop due to corrosion at the terminals... If you have a single set of wire going from the converter in the ER to the FB, they may be too small especially as things may have been added over the years

Measure the voltage at the converter terminals and up on the FB, then compare. Also check the voltage at the converter input and don't overlook the neg wire

 

[Canuck Dennis]

Am curious, is the 25 a output at 100 % power factor or do you have to compensate for 80% efficiency ??

 

[GJH]

I'm with Pascal. These things don't wear out as a rule. Trace and measure the power from the batteries to the convertor input and output on to the end of the line. Have you measured the voltage right at the converter's outlet yet?

 

[chris piazza]

Yes I got 13.2v at the transformer, same to the panel under the steps in the galley and the same all the way up to the bridge. It looks to be 12ga wire all the way to the bridge, which I think is a little bit marginal. I guess it is possible that as electronics get older and more added they tend to draw more amps, it would not take much to put it at capacity. It was a rats nest of wiring under the bridge consul and I have spent the last couple of days sorting out and cleaning out old wiring. It appears as if the previous owner switched radars because I found the old radar wires which had its own dedicated wire. The new radar is 12v and he hooked it into the incoming line from the transformer, that could have been what pushed it to the limit. I thinking I will use the old radar 32v line and mount a 32-12-10amp up on the bridge to power just the radar. That should lighten the load for the one in the engine room.

Chris
Superior Nights 53C

 

[Boatnut]

Chris,

If you are getting 13.2 at the transformer, and the bridge when everything is turned on, then the wiring from the last point could be too small or a defective connection somehwere. If you have not already done so check the voltage at the transformer with everthing turned on, that will help determine if the power source is being overloaded.

I think a lot of the newer radars will run on voltage from 12vdc to 40vdc, possibly other newer electronics are the same. Possibly you don't need another converter run some things on 32vdc. If all these items ran previously without problems, the regulator circuit in the dc to dc converter could be defective, and a repair of the unit may be an answer. Of course it's possible you are overloading the converter, without more info it's hard to tell.

 

[Boatsb]

Almost all the new systems will run from 12-32 volts DC but they will not run on your 32 volt system because its really at 38V. a 24 v system will approach 30 v being charged and thats the window it is made to work with.

 

[Boatnut]

Almost all the new systems will run from 12-32 volts DC but they will not run on your 32 volt system because its really at 38V. a 24 v system will approach 30 v being charged and thats the window it is made to work with.

I stand corrected, thanks

Somehow I thought they went to 40vdc

Hopefully the rest of my post is more helpful.

 

[chris piazza]

I think the problem was the radar being added to the line by the previous owner, just to much draw. If I leave it off I have almost no voltage drop even when keying a mic on one of the VHF's. The JRC radar I have now is a 12v unit but I think it will take up to 16v +\- A small transformer mounted on the bridge should solve my problem.

Chris
Superior Nights 53C

 

[SKYCHENEY]

Chris,
As stated earlier, keep an eye on ebay for a transformer. I bought a 32-12-35 for $80 a few years ago. I didn't really need it at the time, but the deal was too good to pass up. I have since put it good use.