[RE-wrenches] SOC, FNDC, and LFP batteries

Sat Aug 18 17:01:26 EDT 2018

I think if the user wants to find the answer, he is going to have to
hire someone who can read the CANBUS data out of the LG. 

It is very
accurate from what I have seen for 2 years now in testing for Schneider.
Here is a screen shot from a Raspberry monitoring the LG RESU and supplying
the keep alive signal the LG needs. 
Dave Angelini Offgrid Solar
"we go
where powerlines don't"
http://members.sti.net/offgridsolar/ [1]
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offgridsolar at sti.net [2]
text 209 813 0060

On Sat, 18 Aug 2018 12:57:38
-0700, Jay  wrote:    Interesting thread as I was just in contact with
someone with a LGchem coupled to a solar edge inverter.  He's seeing at
times 20-25% less capacity than rated kWh and pretty much never actual
capacity. Tech support gives some wishy washy answers as to why this would
be. Where is the difference, is it in the communication between units or
the BMS? And funny as he's never seeing more capacity.    Maybe there are
some inaccuracies in the BMS's?    Standard OB, trimetric and midnight wiz
bang meters all require frequent meeting of charge parameters ( volt/amps)
to keep the devices accurate. I've got 4 meters that I compare and if they
are full daily it's about 1-2% difference between them. If it's been 7-10
days since full, then they could be off by 10-15%+ off.    Curious what
others are seeing   Jay   Peltz power.          
On Aug 18, 2018, at 9:40
AM, Jerry Shafer  wrote:

   Lou Sounds like you are having the same issue
we did, l adjusted the size of the battery down to 50% of the battery
rating and so far the values appear to follow in. We will also be
installing a DC CT on the egauge to see and have a better idea of whats
going and out outside of the BMU Jerry  
  On Fri, Aug 17, 2018, 12:09 PM
Lou Russo  wrote:   

Hello All, 

Does anybody have any insight in getting
the SOC to report accurately on the Outback FNDC when using batteries that
have a minimal voltage curve? I have several systems with LFP batteries
that have both a eGauge (communicating directly with the battery BMU) and a
FNDC and I get wildly different SOCs. In a typical 24 hour period
(12am-12am) I get SOCs on the FNDC that vary 2% to 34% of what the battery
BMUs are reporting. I am assuming that the BMUs are reporting accurately. I
would think a 1%-5% difference would be acceptable. 

Any help or thoughts
on this subject would be greatly appreciated.  
       Aloha,   Lou Russo
lou at spreesolarsystems.com [5] 808 345 6762 Spree Solar Systems LLC 
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