Ammeter

[BruceK]

Recently I replaced the windlass motor with a new 1200 watt one. The tired old motor used to draw about 45A on its leisurely retrieve, this one sends the needle off the 50A scale, as far as it can go, and rattles the chain in.
The ammeter, which used to show quite small power draws, like <5A for the little Danfoss portable fridge, now only moves for a major draw.
I prefer "cause and effect" to the "coincidence" theory. Any ideas? Has it recalibrated itself? Should I just fit a 100A one?

 

[Bay Pelican]

Bruce

I have been installing several ammeters, Blue Seas units. I spoke to the technical department at Blue Seas about any problems with the exceeding the 25, or 100 amp scale and was warned that this would affect the ammeter and funny (technical term) things could happen.

Marty

 

[BruceK]

Thanks Marty, sounds like it. I would not be surprised something got bent, seeing the velocity the needle moved over and out of sight. Now to buy something matching my 33 year old instrument.

 

[Aquabelle]

Bruce.,, bite the bullet mate and get an SOC gauge so u can really see what's going on....it will show what the current draw is of gear operating as well as track your battery state of charge.

 

[rwidman]

If I suspected an ammeter was inaccurate, I would test it or have it tested. One way to test would be to temporarily replace it with a known good ammeter.

On some boats, the windlass and bow thruster circuits do not flow through the ammeter. An ammeter capable of measuring 100+ amps will be of little use measuring one or two amps. My boat is set up that way, only current passing through the DC panel is measured. The windlass and thruster are direct wired to the batteries (with proper circuit protection).

 

[twistedtree]

Keep in mind that there are two parts to a typical DC ammeter; the meter itself, and the shunt. It would be worth checking to confirm that the shunt is not also limited to 50A. It might need to be replaced too.

 

[RickB]

Why mess with shunts?

Hall Effect 100 Amp DC Current Sensor 4 20 MA Current Loop Transmitter | eBay

 

[twistedtree]

Whatever sensor is used, it needs to match the electrical requirements of the meter. Resistive shunts provide a voltage reading proportional to the current. The hall effect sensor on ebay is a current source. Either is fine provided it's matched with the correct meter.

 

[Brooksie]

Maybe don't put the windlass through the ammeter, your starter doesn't go through it...