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AGM to Pylontech. Do I need comms?


Ivaenol
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I've got a 48V small off grid solar installation with some AGM lead acid batteries that I've not looked after very well and which are going to need replacing soon. I've been wondering about the Pylontech Lithium batteries, but have some questions that I can't make out from their manual and searching.

The manuals describe a communication cable between each battery (which makes sense from a BMS/balancing point of view), but also a communication cable to the hybrid inverter (which I don't have because I have separate MPTT solar charger and inverter, neither with CAN or rj45 connectors).

Can these batteries work just dropped into an existing 48V system (as the only battery and with charging voltages set appropriately in MPTT), or do they require an external comms link to work? Something I read from @Youda seemed to suggest he'd had a working system with no comms link at some point. Long term I'm happy to play around with an arduino connected to the CAN bus to get things perfect, but would be good to get it working first without too much trouble!

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12 hours ago, Ivaenol said:

Can these batteries work just dropped into an existing 48V system (as the only battery and with charging voltages set appropriately in MPTT), or do they require an external comms link to work?

You are going to get mixed feelings about this.
While many forum members say that this communication is mandatory, I have personally never used this feature. I have also seen many installations by other installers without said cables. My personal reasoning is that the BMS takes care of balancing and protection from overcharge or overdischarge. The charge controller only charges to a certain voltage and the inverter switches off at a certain discharge voltage. For me that is good enough. 
 

The one area I could foresee a problem arising is if you had too small a battery bank and too big a solar array. In that case communication might help to keep the charge amperage to acceptable level. 

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Ok Thanks. That's what I needed to know - that it will work at some level. I'll make sure battery bank vs solar panels are sized appropriately for charge voltage, and rely on the BMS otherwise until I have time to play around with the battery Comms and a raspberry pi.

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