48V issues

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wdicken
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48V issues

Post by wdicken »

I thought I had seen an answer to this question before, so if someone has the link, please send.

We finally got our electric outboard boat working. Four 12v batteries in series with an AXE controller. We have the speed we hoped and so far, all is good. Time for the next step.

Power Gauge;

We need to monitor the batteries, both independently and as one. So we need to be able to create a "fuel gauge" for the 48v system. We are using a propeller mPU for the onboard controller and it is measuring speed (Water, Air) so I can add other functions as needed. If I measure the amps consumed by the motor, I can create the logic so I understand whats left (with saftey margin).

Does anyone know of a 48V amp measurement circuit that can tie to a 3208 ADC ? I'll buy it if I have to.

Battery Monitors

I have temperature monitors on my 12v batteries (and the motor) so is there a simple battery monitor circuit for each battery ?

PowerSupply

We power the processor with a seperate 12V battery. Anyone got a simple step down power supply that can go from 48 to 12V ?

Thanks
dyarker
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Re: 48V issues

Post by dyarker »

We power the processor with a seperate 12V battery. Anyone got a simple step down power supply that can go from 48 to 12V ?
What is the max current needed at 12V?

Also, are you actually using the 12V as 12V; or is all of the 12V being regulated down to 5V (or 3.3V)? In the later case it would make more sense to convert 48V directly to 5v (or 3.3V).

Cheers,
Dale Y
wdicken
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Re: 48V issues

Post by wdicken »

It's a pretty small propeller chip (gadget Gangsters prop module) so about 1.5A. The 12V was for the 1-wire devices but my son just pointed out that I can run all the ones on the boat with 5V. So if I get 1.5amps at 5V at the input supply, I should be golden. The chip runs at 3.3 but the 1-wires use 5.

Good catch.
dyarker
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Re: 48V issues

Post by dyarker »

1.5A sounds like a lot, but doesn't matter; 10W @ 5V is 2A.
Jameco and Mouser both carry Mean Well p/n SKE10B-05, a 10W, 5V regulated out, 36V to 72V input supply. Do not be tempted to buy the 48V input unit which is $10 less. Four batteries in series will be almost 54V fully charged, down to 36V discharged. Digikey has DC to DC supplies by other manufacturers.

Surprised no one else has picked up on the other questions yet.

To measure current, the max current drawn by the motor must be known.

Measuring total battery voltage, bottom battery, is relatively easy because one end is common. The individual voltages of the upper three are more challenging.

Cheers,
Dale Y
wdicken
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Re: 48V issues

Post by wdicken »

A good point. I'll get that supply and I'll start working through the notes you had. Thanks
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jwax
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Re: 48V issues

Post by jwax »

I'm surprised MrAl has not commented here yet. He has built 4-channel battery monitors that interface with a PC. Perhaps send him a PM with your exact needs?
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frhrwa
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Re: 48V issues

Post by frhrwa »

telephone company is where I'd start looking.. NEC chargers, etc.. they run 52vdc (48 regulated)..
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Dimbulb
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Re: 48V issues

Post by Dimbulb »

you could develope a voltage divider using higher value resistors so you conserve power.
Then you do a voltage to frequency which is transmitted from onboard.
The recieved frequencies are converted to voltage.
you could recieve each frequency by switching in filters.
accuracy will not be a problem.
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