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Author Topic: Wattmeter  (Read 471 times)

Peter34

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Wattmeter
« on: June 05, 2019, 10:04:02 PM »

Just a general question on what I observed today on watt meter.
I have 2 batteries in parallel running to 2 escs and 2 motors.
If I plug just one battery in with the watt meter between it and the connection on the boat I get 12.6v and 6amps at full throttle.
If I now plug the other batter in. The watt meter still reads 12.6v as expected, but at full throttle only shows 2.5amps.
Is this correct or have I done something wrong.


It is wired as in the pic minus the Leds in the middle.



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fredd

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Re: Wattmeter
« Reply #1 on: June 05, 2019, 11:01:42 PM »

I suspect you have connected the meter to the single wire from one battery and are reading the current from that battery.
The meter needs to be in the single wire to the esc

Fred
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Tug Fanatic

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Re: Wattmeter
« Reply #2 on: June 06, 2019, 08:33:11 AM »

I basically agree with Fredd except that you need to measure the current to each esc seperately or next to each battery seperately & then add them together for total load .

As you have drawn your circuit I cannot see a single wire that is carrying the total load.

Out of interest if you measure the amps next to each battery & they are significantly different readings then it tells you that your batteries are not well matched.

Unless they are Lipos & you are monitoring each cell I hope that you are charging the batteries separately having disconnected them from each other.
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Peter34

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Re: Wattmeter
« Reply #3 on: June 06, 2019, 09:43:14 AM »

Should i change the wiring around so there is one wire coming off the 2 batteries that then splits to feed the escs or won't it make any difference. It seems to run fine s it is.

Have measured both sides/ batteries and the amp draw is the same 6amps at full throttlewith only one battery connected. With both batteries connected its shows 2.5amps.
They are 3 cell lipos and are removed and charged separately.
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Tug Fanatic

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Re: Wattmeter
« Reply #4 on: June 06, 2019, 09:55:22 AM »

There is no running advantage in joining the batteries & then taking feeds from that combined supply line to each motor/controller - it just makes measuring current easier!

Where in the circuit have you placed your watt meter for each reading?
As stated above there is nowhere that carries the total load with 2 batteries connected so as there are two supplies & essentially two loads (actually there are 3 loads if you include receiver/ servos etc) you will need to add two/ three readings to get the total.

Have you got fuses in the circuits?
 
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Peter34

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Re: Wattmeter
« Reply #5 on: June 06, 2019, 10:03:08 AM »

I plugged one battery into the watt meter and the other end of meter into the battery connection on the boat. Tried it with a single battery connected and both.
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Tug Fanatic

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Re: Wattmeter
« Reply #6 on: June 06, 2019, 10:19:29 AM »

I plugged one battery into the watt meter and the other end of meter into the battery connection on the boat. Tried it with a single battery connected and both.

You need to measure at both point A & point B on the amended circuit diagram & then add them together.

I would also want fuses at A & B (which mainly protects the batteries) & just before each controller at C & D which will protect the controllers in the event of a prop jam. Yes I am fuse mad!
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JimG

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Re: Wattmeter
« Reply #7 on: June 06, 2019, 01:26:01 PM »

Just a couple of points. Most seem to be assuming that an ammeter is being used to measure the current so only one wire from the battery is used. The OP is using a wattmeter, these are connected to both the  ve and -ve wires out of the battery as they also measure voltage. Check the way you are connecting to the batteries as it seems that with one battery you are measuring current to both escs while with both batteries you are only measuring current to one esc.Also there is no need to charge the batteries separately as long as you have not run one down much lower than the other. As long as they are both near the same they can be charged in parallel without any problems, there are parallel charging boards available for this which can take 6 batteries in parallel for charging. As long as the batteries have the same capacity the fact that they are being used in parallel will mean that they stay at the same charge state.
Jim
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Peter34

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Re: Wattmeter
« Reply #8 on: June 06, 2019, 01:39:13 PM »

Indeed, the watt meter is connected to the plus and minus of the battery. And displays voltage amp draw and mah used.


I have a parellel charging boards that I use for charging my quad batteries.
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