StandardProducts/Lithiumate/Service/Troubleshooting/CalculatedData


<h1>Calculated data issues</h1>  


<h2>At power-up, doesn't remember previous SOC</h2>


<ol type="1">
<li>SOC is somewhere in the range of 20 % to 80 % 

</li>
<li>BMS is turned off 

</li>
<li>BMS is turned back on 

</li>
<li>SOC starts at a different value (typically 50 %), and always at that particular value 

</li>
</ol>
<p class="line874">The problem is that, at power down, the controller didn't update the SOC in non volatile memory (EEPROM) 


Cause: 

<ol type="1">
<li>Either the BMS controller didn't realize that it was being powered down 

<ul>
<li>This can be due to the supply to the BMS controller taking longer than 10 ms to drops 

</li>
</ul>
</li>
<li>Or, it didn't have enough energy left to update the SOC 

<ul>
<li>This can be due to additional loads on the 5 V supply (Rev D hardware only) 

</li>
</ul>
</li>
</ol>

Solutions: 

<ol type="1">
<li>There can be no large capacitor across the supply: 

<ul>
<li>The supply should come directly from a switch (including a solid state switch), not directly from as supply (such as a DC-DC converter) 

</li>
<li>If the supply is coming from a supply: 

<ul>
<li>Add a high load across its output, to discharge its output capacitor rapidly 

</li>
<li>Reduce the value of the capacitor on its out (the ripple will go up, but that's OK) 

</li>
<li>Add a switch in series with it, between the supply and the BMS controller, that is opened when power to the supply is removed 

</li>
</ul>
</li>
</ul>
</li>
<li>Rev D only: do not use the 5 V output (Control connector pin 7) to power external loads 

</li>
</ol>