We’re looking for customers experience regarding the accuracy or difference between using the BMS State Of Charge reading, or a Shunt SOC reading.
This is specifically for customers who have batteries produced after June 2024, or have upgraded the BMS Software to version 32_240529_ZC0T (for 12v batteries). This BMS software version has been shown to have exceptional results in our testing, but we would like some more real life customer feedback. The question is also aimed primarily at users who regularly use their system and monitor these 2 items side by side. If your RV is irregularly used, the SOC readings are known to be wildly variable.
There are many myths and truths about BMS SOC readings, and they vary according to brand, settings, usage, opinion, bias and more. One common thing we hear is that a smart BMS SOC is never accurate, but this is simply not true. Just like external shunts, they are accurate in the right conditions, and inaccurate in the wrong conditions.
Have you found the two devices track accurately?
Do they synchronise often and accurately when fully charged?
Does one seem more accurate than the other, and how did you determine this?
Do you trust one more than the other?
And of course we welcome any other feedback for either, so we can continue to improve the product.
Our latest BMS Software takes into account both the power used by the BMS itself, and the self discharge of the cells, and of course this is based on the programmed cell capacity. While these are numbers embedded into the BMS, they do normally help the SOC calculation be more accurate. In general it will underestimate the SOC, so if it says 40% SOC, you will likely have significantly more in reserve, which is a good thing.
An external Shunt will not measure these two parameters. External shunts normally have better accuracy at low currents down to as little as 100mA, so they will often be better at counting loads such as USB chargers or small LED lights, or small amounts of charge early in the day or late in the afternoon, whereas the BMS may not accurately measure current under a couple of Amps.
If you have not yet upgraded the firmware, you can do so by going to this link and filling out the form.
https://powerpaul.com.au/powerpaul-battery-daly-software-upgrade/
