GVSolar
Solar Enthusiast
- Joined
- Jan 6, 2020
- Messages
- 455
I am in the process of creating a large bank of four TechDirect/BigBattery pre-built 24v BYD units (3kw usable capacity each). Three of the units are already "awakened" (three charge/discharge cycles) and connected in parallel. They are receiving their charge from (2) Schneider Conext MPPT 60-150s (DC coupled 3000w) and a 1500w string of REC/Enphase M-215s (AC Coupled) thru a Conext SW4024 inverter. System monitoring is thru a Conext SCP/Combox.
In order to commission the system I first connected two FullRiver DC-115 AGM (115ah) batteries in series (24v), and connected them to the inverter/chargers for LFP programming (replacing my previous bank of Trojan L16s). After setting the charge parameters for LFP I added the parallel string of 3 TD/BYDs to the 24v AGM. This parallel LFP/AGM bank is performing as expected - and I am now installing a separate fused disconnect switch to bring the AGM battery in or out of the main bank of LFP as needed (adding a fourth TD/BYD unit this week).
I originally thought of this primarily as a maintenance issue (programming/reserve capacity) but after some reading on the subject the notion of the AGM battery acting as a island of last resort in case of a BMS disconnect (overcharge/low temperature, etc.) began to appeal to me.
Thoughts on implementing this in my totally off-grid system would be very much appreciated.
Some reading on other LFP/AGM parallel banks:
In order to commission the system I first connected two FullRiver DC-115 AGM (115ah) batteries in series (24v), and connected them to the inverter/chargers for LFP programming (replacing my previous bank of Trojan L16s). After setting the charge parameters for LFP I added the parallel string of 3 TD/BYDs to the 24v AGM. This parallel LFP/AGM bank is performing as expected - and I am now installing a separate fused disconnect switch to bring the AGM battery in or out of the main bank of LFP as needed (adding a fourth TD/BYD unit this week).
I originally thought of this primarily as a maintenance issue (programming/reserve capacity) but after some reading on the subject the notion of the AGM battery acting as a island of last resort in case of a BMS disconnect (overcharge/low temperature, etc.) began to appeal to me.
Thoughts on implementing this in my totally off-grid system would be very much appreciated.
Some reading on other LFP/AGM parallel banks:
Parallel lead acid and lithium circa 2018 - Class B Forums
Are we going to start seeing parallel lead acid & lfp battery setups now with the drop-in lithium batteries? There's already a commercial option for this: https://www.bos-ag.com/products/lith...ens
www.classbforum.com
Battery Mixing integrating Lithium Lifepo4 AGM or Gel
Ok, I know Im out on a limb here with the general consensus. What I’m looking for here is a technical explanation as to why not, or how to, run a mix of AGM/Gell and Lithium The attached shows my current setup, and my thinking of how I will integrate lithium. So firstly some information: My...
forums.sailboatowners.com
Lithium battery systems | Nordkyn Design
nordkyndesign.com