LifePO4 3.2V Batteries vs. "Drop in Replacements"

[Rando]

The hall effect sensors are definitely more noisy than shunts, if the electronics reading the current were designed for a shunt they may not have the filtering necessary for the hall effect which could lead to integrating errors. The other issue with hall effect sensors are offsets. Hall effect sensors are actually measuring magnetic fields, with the open loop sensors you can actually get some interference from external fields, including the Earth's magnetic field - which could be a particular issue on a truck which changes orientation frequently. You may end up with a phantom load when you park N-S relative to when you park E-W. I know on my DC hall effect clamp meter you need to zero the meter in the orientation you plan on using it in before taking a reading.

Anyway, for your application there is no reason not to go with the shunt that you already have.

Here is a good table from Texas Instruments that describes the relative attributes of various current sensors:

Source: https://e2e.ti.com/blogs_/archives/...-sense-current-and-how-to-decide-which-to-use

 

[VerMonsterRV]

Quick update, my batteries have reached the US and are in the hands of FedEx with a delivery of Monday scheduled. I'll report back when I receive them.

 

[RandyP]

great thread, learning more about LiFePo4 batteries than I ever imagined possible.

 

[VerMonsterRV]

I got the batteries today! At least from first glance they all look good and no damage. Hopefully they will work as good as the look. If so, they were $1600 shipped for a 400Ah battery pack, and Ginger at Frey Battery was very responsive. Actually I don't think she sleeps as she seemed to answer my emails any time of day.

I also heard back from Thornwave, Razvan did get and test the Hall effect current sensor. Here is his response

"I noticed a difference of up to 0.2-0.3A between the hall effect sensor and the shunt.

This has nothing to do with PowerMon. The difference is because Hall effect sensors are less accurate and have more offset error than current shunts.

You might have an offset of up to 0.3A. You can correct that by zero-ing the current.

There is not much you can do about the accuracy. You can try to calibrate the whole current measurement but does not guarantee that the 0.2-0.3A of difference does not change over time."

So, given this I am planning on sticking with the shunt.

 

[Rando]

Glad your batteries look good, this should be a fun project!

On an coulomb counting (ie integrating) battery monitor, offsets will kill you. It may only be 0.3A offset, but that means your SOC will be off by 8Ah after one day and by 50Ah at the end of the week. Stick with the shunt.