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Logging battery amps
#11
I've also been playing around with esp8266 and ina219 together with at sd card module in order to have the esp8266 logging it's values locally when the pi is shut off. When tied up for the night I usually switch off the pi in order to save on the on board batteries. But I still want to monitor the consumption from the cooler, pumps, anchor light etc.
When the wifi comes back up the esp8266 sense that it again has a connection to emoncms (in my case) and starts sending the buffered values from the sd card. The trick was to always include the timestamp when sending the data to keep it accurate.
I use ntp towards the pi to set the time on the esp8266.
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#12
Fantastic. I have a task to replace my shunt - perfect timing to add better battery monitoring. I like the electrical isolation by using the ESP.  Great job. Thanks for sharing!

Hank
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#13
Hello,

Do you have published the code ? (i can't find it but not sure if i've missed something).

Thanks !
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#14
Hi,

I 'll Probaly ask a newbye question :

I see on the chart the current going up to 15A.
But the ina219 specifications are 0-26v and 3,2 A.
How can the INA support so high current ?

Cordialy
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#15
The shunt makes that possible. Here’s an article with a good explanation or google shunt resistor

https://www.rc-electronics-usa.com/current-shunt.html


Sent from my iPhone using Tapatalk
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#16
OK thanks for this information.

I am reading, about shunt and ohm's law, then it reminds me some very old memories from school Sad

I was reading on an other forum that it is good to take some safety precautions with a shunt, because it can become very hot.

Which ratio is good to respect ?
To measure 20A install 100A shunt ?
More or less ?

What about something cheap like that : https://fr.aliexpress.com/item/Good-perf...Title=true
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#17
(03-10-2019, 12:46 PM)topodom Wrote: OK thanks for this information.

I am reading, about shunt and ohm's law, then  it reminds me some very old memories from school Sad

I was reading on an other forum that it is good to take some safety precautions with a shunt, because it can become very hot.

Which ratio is good to respect ?
To measure 20A install 100A shunt ?
More or less ?

What about something cheap like that : https://fr.aliexpress.com/item/Good-perf...Title=true

I'm just piggy backing my ina219 on top of the battery monitor shunt which from memory is something like 500A, 50mV. Your link looks OK though might be a good idea to have any really big loads like a bow thruster direct to the batteries.
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#18
Yes i think, it s good to keep margin.

I read again proprely the link given by  svtgd.
they write : "In practice current shunts are often rated to be used continuously at only 66% of their "rated current"

So in my case to monitor 150W (8A max) of the solar panels i will order a 30 AMP and for the max load on the electric panel (5A) a 20A Shunt.

Hope it will be OK Smile
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#19
Hi

I'd be keen to try this but cannot find a link to the code, could someone please give me a pointer?

Many thanks
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