close-loop modbus communication with lithium batteries

Started by Paniolo, August 23, 2021, 03:00:32 PM

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The batteries I have have RS485 ports and they have closed loop communication with a number of different controllers, but I didn't see the DIY on their list here even though other Midnite controllers were listed as a being compatible (Solar Classic 150, 200 & 250; Solar Classic 150, 200 & 250-SL) here.

Will my system be able to make use of the RS485 capability on the MN3548DIY and on the Fortress batteries? And do I need an adapter, or do they use the same RJ45 pin-out as Fortress eFlex5.4 LFP batteries? It would be really nice if all I have to do is plug in spare RS45 that comes with the batteries into the controller and everything just works with closed loop communication, almost as nice if I have to make an adapter, and not so good if they don't talk to each other for some reason despite both having RS485 connection ports.


I just got off the phone with Midnite tech support. I had an Outback Power system for years, and it was designed for lead acid batteries, before anyone thought of communicating with a BCM to get accurate state of charge. Since then I upgraded to LFP batteries and decided when my son gets his system we'll buy something that might be able to communicate with the BCM instead of just going off of the voltage (because the LFP voltage curve is so flat, voltage is clearly not the best way to do it). With that in mind, when I saw this cheap combined inverter and charge controller that had two RS485 ports and a CAN bus port, like my batteries, I figured this has got to be a great deal. The only reason anyone would put all those ports on there is to be able to do this sort of thing. Well it turns out that they could do it but their engineering folks at MidNite talked about it a couple of weeks ago and shot down the whole idea. That means I should have bought a Phocos because none of this is going to happen with MidNite (unless they change their minds). Phocos is working with my LFP battery manufacturer on closed loop communication already. I'm extremely disappointed with Midnite. The guy said they won't implement closed loop control because they'd have to re-implement it differently for every battery manufacturer. I suggested if there were a standard message protocol where it could be unified that could all be avoided, and he was not interested in having anything to do with establishing standards either. I don't like that attitude. My battery manufacturer was saying if we could find someone willing to answer a few programming questions with them and sign a nondisclosure agreement concerning their proprietary protocol that they would work together. Midnite says it's not going to happen. So don't buy this for closed loop communication with your batteries because it doesn't exist and they don't want to make it exist, period. Make an announcement if this changes, or I won't be recommending this to anyone like I was starting to do. I have to go back and tell all the people I was convincing this is good that I was wrong.


The RS485 speaks Modbus, I will be publishing the documents today or Monday. That said I would love to know who you talked to in support as we never had a plan for communications on this product line and have not had any meetings on it.

We will also most likely have a wifi dongle for them soon.


I have added the Modbus info for the DIY inverters here

I will be testing out the wifi adapter as well as USB communications over the next week