Motor Draw and Stall Amps

[AHarris]

My digital multimeter has just arrived from Amazon and I have connected it to my main motor (has the biggest prop on it and sall be used for vertical movement).
In air it draw approximately 1 Amp, when I stop the motor with my hand it reaches 2.5 Amps. Does this mean that underwater it shall draw a maximum of 2.5 Amps as this is the point where it stops?

Or am I looking at this in completely the wrong way?


Thanks

[thegadgetguy]

2.5 amps is the stall amps, so that's pretty much the maximum the motor can draw under any circumstances. Even with the motor underwater, it probably will be lower than that on average, as the shaft is still turning.

[derelicte]

I would have expected a higher stall current. what kind of motor is it?

[AHarris]

Hi, I should point out this is without the tether attached.
It is a bilge pump, I believe it is a Rule 800 which I have attached a set of computer fans to which are approximately 80mm across.

I too am slightly suprised, especially when considering others on this forum claim that the motors they used draw almost ten times that when underwater...
I did do a trial run and I can certainly feel the pull of the motors and they kick up enough water so I think they shall be fine?

[derelicte]

I don't know about 10x, but mine draw almost double that running underwater and are basically the same (500 and 1000 gph cartridges).

I have no idea what the stall current is on mine, and I'm not sure I want to find out. those props are sharp!

is something else limiting the current, like wire size or the ammeter?

[sthone]

Yeah... your either reading/using the meter wrong or something else is amiss. 2.5 amps is way to low for a stall current.

How are you hooking up the multimeter?

Are you running the current through the meter or just attaching the leads to the pos. and neg. terminals on the battery?

-Steve

[AHarris]

Yeah... your either reading/using the meter wrong or something else is amiss. 2.5 amps is way to low for a stall current.

How are you hooking up the multimeter?

Are you running the current through the meter or just attaching the leads to the pos. and neg. terminals on the battery?

-Steve

Hey, I think I am doing it right but it would be worth it if you could just check:

I have connected the negative to the battery and then the positive to one of the rods on the multimeter. Then I place the other rod on the other battery terminal and take the reading.

In terms of wiring I am just using the wires which are from the pumps, the pumps are old and have been in a box for a while? Could it be because they haven't been used for a while, when starting them up they didn't sound as healthy but seem fine now?

Thanks

[reHosea]

Hi. I didn't see any specs posted on the battery that you are using to power your pump. So, just to point out an obvious question here; is the battery capable or producing an amperage draw greater than the 2.5 amps you are seeing? I'm guessing it probably is, but I just thought I'd ask.

[AHarris]

Hi. I didn't see any specs posted on the battery that you are using to power your pump. So, just to point out an obvious question here; is the battery capable or producing an amperage draw greater than the 2.5 amps you are seeing? I'm guessing it probably is, but I just thought I'd ask.

Erm, not too sure as it is an old battery and the label has fallen off.
It is a 9 Volt Lantern Battery, I think it may be one of these Eveready batteries: http://www.rapidonline.com/Electrical-P ... ry-18-0249

Obviously it is nowhere near car or tractor batteries but it is just a battery to test with. In the future however, I was planning on getting this set:
http://www.rapidonline.com/Electrical-P ... rger-62263

As they are small, has everything I would need and most importantly they are cheap. When you say, 'is the battery capable of producing an amperage draw' would this one only be capable of putting out 1 Amp as it states 'Max Discharge current 1.0A'

Thanks again for all the help!

--NOTE--

Not sure whether this shows any information, but connecting the multimeter directly to the battery terminals and measuring the amps on it I get 3.57 Amps which I am guessing shows that it can put out a maximum of 3.57 Amps?

[derelicte]

well now you have basically shorted the battery out so all bets are off.

try measuring it again with a 12v car battery.