Motor power/voltage monitoring question

[Volt_Ampere]

Yes I think I could do that too.

[Volt_Ampere]

Some meters need isolation and some don't. Depends on how they designed them. If then need isolation, the power supply for the mater must not be grounded to the battery pack that you are measuring or it won't work properly (or worse it may smoke). These are all Chinese designs that I am not sure I would trust on my cart.

[Iflyasa]

Originally Posted by Volt_Ampere

Some meters need isolation and some don't. Depends on how they designed them. If then need isolation, the power supply for the mater must not be grounded to the battery pack that you are measuring or it won't work properly (or worse it may smoke). These are all Chinese designs that I am not sure I would trust on my cart.

So would I purchase a low power reducer and separate that from the battery pack, to power both of these meters? I'm trying to figure out how to do that. Take 48V from the batteries but find another ground source if that's possible? I guess I could get a small lawn mower 12v battery as well.

[Volt_Ampere]

Be careful if you are using more than one meter. They may each require an isolated power supply. Depends on how they are connected and what is in common. An isolated power supply has a transformer that allows the input and output to be isolated. Most 48V to 12V golf cart converters don't have any isolation. The input and output grounds are tied together internally. (and have to be)

[Volt_Ampere]

Here is the isolated 12v to 12v that I am considering for my design:

TDK-Lambda Americas Inc. CC3-1212SR-E

Small and low power (250mA)

[Iflyasa]

Soooo now that you guys have enlightened my knowledge, let me see if I'm on the right page...

Let's say I use a lawn mower battery, 12v.

I use this to power both my meters. The first meter being the 1000 amp that monitors the motor and anything from the 48V collectively. Hook the shunt in series with the -48v from the # 6 battery, while powering the meter with the 12V lawn mower battery.

Next, my other meter is strictly to monitor my 3 voltage reducers (48v to 12v), which I hook the shunt in series with the negative common ground, which is also powered by the 12v lawn mower battery.

In theory would this get me started? If so, next would be removing the lawn mower battery, and figuring out a way to power each meter from independent isolated 12v power. I would have to use one of my voltage reducers for the 12v power. I am assuming the parts you guys listed above would enable me to do this? I don't understand how that would take a non isolated 12v and make it isolated. If it works then great.

So initially could I just test both meters from the non isolated 12v and see if my meters can work without isolation? If one or or neither work, then I try the lawn mower battery. While that's working I then try the isolaters you guys mentioned previously.

Thanks

[cgtech]

I have killed a few cheapo volt meters by not using a isolated power source. Then i spent a few bucks on these isolated power supplies. The meters have zero forgiveness for being hooked up to non-isolated power source, its killed instantly, no "lets try something else". They are available on other output voltages too. Their may be cheaper options, but thats what i found that worked.

[Iflyasa]

Originally Posted by cgtech

I have killed a few cheapo volt meters by not using a isolated power source. Then i spent a few bucks on these isolated power supplies. The meters have zero forgiveness for being hooked up to non-isolated power source, its killed instantly, no "lets try something else". They are available on other output voltages too. Their may be cheaper options, but thats what i found that worked.

Did you isolate and did it work? If so how?

[Volt_Ampere]

Be careful with multiple meters running from the same battery. They are not isolated from each other and you may have a ground loop that will kill them. As cgtech said many of these meters will not tolerate lack of isolation.

[Iflyasa]

Originally Posted by Volt_Ampere

Be careful with multiple meters running from the same battery. They are not isolated from each other and you may have a ground loop that will kill them. As cgtech said many of these meters will not tolerate lack of isolation.

Hmmm 2 small lawn mower batteries?