Dynamic Product Search

Smart Energy Management for Marine and Off Grid


No products in the cart.

REC and WS500 User Forum

Please or Register to create posts and topics.

2 REC Active in Parallel batteries

12v RV with the new Victron Multiplus II.  Any issues with using a pair of the these BMS's in parallel?  Considering having the redundancy of a pair of 2P4S batteries rather than just one 4P4S battery.

How well does the software handle having more than one battery/BMS?

What items would I want two of? BMS/Wifi/??

Thanks much.

Great question.

First, the 2 BMS's can indeed share a WiFi module but they need to have their RS485 addresses set differently and then you can then just select the one to communicate with once you log in to its web server.  The only limitation is that all history logging will be recorded for the unit currently connected, which for me is not a major issue, but something to consider.

For the second question, it seems you are looking for device aggregation, and that become a function of how the Victron device deals with it.  Next month we will have our test lab set up to confirm how it all works together it but for now I will reach out to REC to see if they can help.  (it could be a few days before we get back on this one as its a holiday there)

You dont mention your application but if you are including a WS500 smart regulator it will indeed aggregate your loads with multiple REC BMS's


Thank you for the info. Look forward to hearing what REC has to say.

One additional sub question would be: If using two WiFi modules, would that allow for history logging from both devices?

Thanks again.


Correct, you would just set each WiFi device to a single unit.  I haven't tried it yet but it might be that your WiFi modules could each act as a backup, giving you redundancy at that level too.  I will have to try that one sometime.


Please let me know what REC says about the software being able to track two separate batteries/BMS's vs just 4 "cells".


I am interested in this posting. I will trying to connect 4 LFP batteries in parallel using 4 REC BMS units. My plan so far is to use a Victron BMS-712 battery monitor and/or a Victron Cerbo to manage the charge bus. Right now I am assembling the 2nd LFP and experimenting with that configuration. I think I will use the REC WiFi unit as a portable stand alone "test set" and plug into each battery as needed. My application is for 4 LFP's on a sailboat physically located at different places on the boat.

As it stands right now the REC architecture is designed in such a way that the Q series with a master controller that provides supervisory control and monitoring is the way to go for a complete integrated system off grid monitoring and control system, but it seems there is another level of integration in which we just want to have multiple systems on our network and in only some instances be able to aggregate the values.

I am thinking the best way to implement this strategy would be by using the Cerbo/GX with a bit of code that allows you to do this without the need for the master.  Additionally, for 12v systems we should be able to use the Active BMS as well.

This is young market and is evolving fast.  We intend to stay on the leading (and even sometimes, bleeding) edge so we are setting up a complete testing and training system with components from Victron, WakeSpeed and REC to really be able to dig into its possibilities.  With that in mind, we can see this feature as one near the top of our list for implementation.



TAS CPA has reacted to this post.

Thanks Rick for your comments and commitment.

I am currently building my second 20aH battery, its just minimally breadboarded now. I have the two batteries connected to a Cerbo and find some interesting surprises. The main surprise is that the charge and discharge currents going to/from each battery is much different than expected, they are not even close to equal.  I am not too concerned yet as the battery system resistance is probably a big factor why (i.e. on my completed battery, the system includes, fuses, contactors, bus connections, etc.) vs the bread board battery only includes a battery disconnect switch.  Granted the resistance of the completed system should be low, it is still a major difference.

I also have the following task ahead, that is now a BMV-712 battery monitor is controlling the charge bus relay. The fact that the SOC of the battery monitor vs the SOC of the BMS(s)  is different the system is not yet autonomous. I will need to have the Cerbo be the control mechanism for the charge bus relay.

This looks a little messy but it shows a bit of my set up


Uploaded files:
  • system1.jpg

Thanks for sharing !

Finally finished my second battery build, although these are just minor capacity cells (20aH). Slightly different in that I have used the REC WiFi module instead of the Bluetooth Module. Lots to learn and try to figure out. This is 2 batteries, my goal is 4 with a capacity of 200aH each.

I am hoping to be able to use the Cerbo more that I am. I have not yet figured out how to use the Cerbo to switch the charge bus relay but I think that will be do-able. My other challenge will be getting 4 batteries talking to the Cerbo. I have the REC BMS’s configured to talk to the Cerbo via a   V.E.-CAN connection of which there are only 2 inputs on the Cerbo for V.E.-CAN section. I thought it would simply be a matter of adding a network switch, but that didn’t work. My IT skills are very minimal so that was a blind shot in the dark.

I am trying to also teach myself Arduino to see if that or Raspberry Pi might work in monitoring and managing my 4 LFP battery project.

if anyone who reads this has some suggestions, I am listening. I know I have a lot to still learn.

Uploaded files:
  • 9F5F89FF-502F-4512-936B-731D267CD057.jpeg

Hey Patrick, if you could share with us a summary of what you are trying to achieve with the 4 packs and maybe some sequences of operation or pseudo code, it would help us give you some meaningful feedback.

As for your network keep in mind that this is not an internet connection so a switch will not work.  It is a daisy chain peer to peer topology that uses end of line resistors at each end to stop reflection.  A victron or CANBus network search will get you pointed in the right direction.

And for internet connectivity, if you put them all together on the same subnet you can just create a webpage with a bit of html and J's to display anything you want.  Here's an idea, use an RPI as your wifi router/server and add it there.  I bet you can even find an image with all of the LAMP server stack already setup for you. Even a router that supports openwrt and allows you to add webpages right into your router is another idea to explore.

More project info will help

Looking good!

Hopefully I am not intruding by asking a related question:

For a 24V system, would it be possible to also use 2 REC active in serial?  Or is there a product designed for 8S batteries that also has active balancing?  Thanks!

No Problem,

The REC Active BMS is for 12V systems.  It can be connected in parallel to create multiple 12V packs for expansion and redundancy, but it can not be used for 24V systems as you would have ground potential and inter-balance issues.

For 24V systems and greater you will want to use the Q Series BMS from REC, but it uses conventional top balancing.  Here is a link to it on the site.


If you need assistance configuring your BMS, just send an email to tech@offgridsoftwaresolutions.com with your system parameters and we will put together a pre-filled shopping cart link for your review.