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enodev avatar image
enodev asked

SmartShunt time to go computation question / infinity versus finite time

Hi guys,

I'm using SmartShunt to measure and visualise time to go of my RV battery, working great. For screenshots and more here is a project: https://github.com/mman/node-red-dashboard-ismove

When SmartShunt periodically sends time to go when battery is discharging, the value is averaged over recent consumption interval and is very useful.


However whenever charging starts - such as when solar panels kick in, the smart shunt stops sending the time to go value as soon as the flow of the energy goes to the battery, in other words as soon as the battery stops discharging.


Although technically and mathematically correct, it is not useful at all for example in an RV or Yacht, because it displays time to go as infinity, but that is not correct, as soon as the sun stops shining, time to go will drop back again.

What I did is to remember the last time to go value, and display it along, since "actual" time to go has not changed that much and will probably not change much for as long as batteries stay at around the same SoC. So I display the last value with "+" attached indicting that SoC is going up.


Am I the only one who finds this a bit confusing? Thoughts?

Martin

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2 Answers
Alexandra avatar image
Alexandra answered ·

@enodev

Trying to apply human logic doesn't work.

The device only knows there is a charge source. It doesn't know that it is solar or that the sun will go down. It only knows you are now positive not negative so time to discharge is infinite.

There is a mod somewhere else that will switch the notification or message to time to full charge. Not sure where as came across it ages ago. But that might be a solution to work i to your mod.

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Alex Pescaru avatar image
Alex Pescaru answered ·

Hi @enodev

Suppose that the battery was starting to charge at 50% when it still had 3 hours of time-to-go. You are saying - keep that 3 hours displayed. OK.

But when the battery will be 80% charged and the sun goes down, the time-to-go will not be 3 hours anymore, will be maybe 4.5 hours, of course if the consumption will still be the same. It will jump to 4.5 on display?

Maybe you should also take into account the amphours information to properly correct the time-to-go when charging...

Just my 2 cents...

Alex

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