4000 Pro + Tank: Unequal discharge
I've got a 4000 pro installed with a single tank stacked in my Sprinter. I commonly see the tank capacity at 10-20% below the main unit. I would expect the two units to draw equally. Is this normal and expected behavior?
When charging on shore power, the two do eventually even out. Thanks.
Answers
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Just got my 4000 pro, but seeing the same thing. I plugged them in this morning, let them equalize and fully charge. Now that I'm using it, the display says 100%, but when I look in the app the tank is at 84%, while main battery is at 100%
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Due to the way our LFP batteries and the SoC reading work, it’s not uncommon for there to be a gap between the Yeti & Tank SoCs but can still be considered equalized as our definition of equalization depends on the state of the battery voltages and not the SoC reading.
Here is a summary of some potential conditions the Yeti & Tank can be in:
- Unequalized – Yeti & Tank have a wide margin of Voltage difference and thus begin pre-charging (a low current <5A) charging state where the Yeti & Tank attempt to gracefully close the voltage gap
- Non-matched Regular operation (equalized in technical terms) – Yeti & Tank don’t have the exact same voltage but are close enough that the FETs on the BMS are opened and operating in normal condition, when system (Yeti & Tank) are idle it will trickle charge some small amount of current to equalize the battery voltages between Yeti/Tank
- Matched Regular Operation (equalized) – Yeti & Tank share the exact same voltage (or close enough to the same voltage) that there is no further trickle charge between Yeti/Tank and the system operates in normal condition
- Idle – Tank and Yeti can communicate, but won’t establish full connection & current won’t flow between Yeti/Tank
To check if your system is in state 1, go to the ‘device info’ menu on Yeti itself and scroll to the page for Tank FW version. At the bottom of the screen, it should say ‘pre-charging’.
If the status there instead says ‘combined’ then your system is in either condition 2 or 3.
If the state instead says ‘idle’ that means that the system is in condition 4 where your Yeti is detecting the Tank, but for some reason isn’t engaged (no power will go to or be drawn from the Tank), we will need to troubleshoot/reset to correct that.
Conditions 1-3 are normal to be in & only condition 4 would be an issue that we need to resolve provided the Yeti and Tanks are getting roughly the expected Watthours/runtime that should be expected based off the system (# of Yetis/Tanks) and load they are running (to rule out bad battery capacity).
