Ok,
maybe check you get a BMS with heating.
In any case look for active balancer, either build in or an external NEEY.
I am quite habe with my PACE200 BMS as I can set all parameters.
Yes, the batteries we are looking at have JK BMS with heating, fire extinguisher, active balancing and RS485 as well as Victron CANBus support,
In your first post you want a second level of (smart) protection for each battery. That should be possible with an Victron Smart Shunt, a solid state relais and a phone (software/ app) with this you get battery protection independent of the Ess protection (if that should fail)
Not sure I understand this. The smart Shunt offers measuring but no switching, contactor or way to read or isolate a malfunctioning battery?
You mean something like just measuring the SOC and use a remote relay to switch based on that?
Like 500A current? switch off⊠58 Volts voltage? switch off the battery by the solid state relais (or a mechanical relais wich are very expensive).
A quick search turned nothing unfortunately.
You could use one or two of these in line with your Smartshunt. Youâd have to control it (them) through one of the relays of the Cerbo.
These are from Tyco Electronics, so not some One Hung Lo cheap Chinese brand.
I am seriously considering going on the same path for my system (still in the planning phase). The disconnect is for emergency purposes. I see three options:
- 4 pcs. Victron NG 5 kWh with 2 Lynx BMS NG (2 for redundancy).
- 4 pcs Pytes V5 with 2 Lynx BMS old.
- 4 pcs Pytes V5 with Smartshunt and TE Kilovac.
I would like t know what path you took with your system.
Thanks for the TE Kilovac tip @DavidOvNL . I assumed Victron has a gadget like this but maybe not? Smart BatteryProtect fits the bill but is not for nominal 48V. You think Pytes is worth it? Curious about your reasons. Victron NG batteries are only slightly more expensive than Pytes per kWh, which gives you Victrons eco system for security and monitoring.
Ah well. I guess my thinking is as much kWh as I can afford and then add as much security as I can afford.
As suggested in this thread, it is also possible to buy higher quality batteries and spend less on security layers I guess, but we can get more than three times the kWh of 4 Pytes V5 with similar high quality cells ATM for a similar price. Depending on your needs obviously, but more kWh does give you options for usage.
Yes, I will post here when this system is up and running in about 2 months, if this thread is still open.
Hell @OGPS
May I ask you a specific question on using the older Lynx Smart BMS for 3d party batteries if you have a moment?
Is the procedure to simply close the smart battery loop with an extension cable to silence smart battery coms and then use it as a shunt, contactor and precharge unit?
And can you then set DVCC using the JK BMS but use the Lynx for SOC or am I missing something obvious?
Do you know if the relay/contactor of the Lynx BMS is published in Node Red via the Victron Node, so that it could potentially be used for security and automations via Node Red?
Finally, are there any major drawbacks there in your experience in terms of settings and what is shown in the VRM as well as real world usage? Thanks!
Exactly!
Yes. You can separately configure your controlling BMS to be the JK and the battery monitor to be the Lynx BMS.
We havenât tried to control the contactor in the Lynx BMS via NodeRed so I donât know. We use a physical switch with the remote terminals of the Lynx BMS. I havenât really thought about using NodeRed for this, but for emergency power off (EPO) I prefer something simple and out of band. Meaning, in an emergency, I donât know that I would want to rely on NodeRed running on a device that is part of the overall system. But you might have other uses for this Iâm not aware of.
I find the settings in the JK BMS to be overly complicated in general, but handy for the tweakers who want the most control. The bigger problem is the lack of documentation (at least in the beginning) and having to use trial-and-error just to figure out what a poorly worded parameter really means. Andy at The Off-Grid Garage has spent the last two years chronicling the ups and downs of what works, what doesnât, what JK broke when he requested a change, etc. I donât have the time or desire anymore to deal with stuff like that. And I certainly donât want to provide support to customers who rightfully expect us to support anything we recommend or sell. So, I donât have long-term experience using the JK BMS in DVCC and how drifty the JK shunt is. In the last 12 months Iâve just watched Andyâs experiences. Heâs got it figured out and working, but heâs using the iBMS and SmartShunt to do it.
That said, in the early days of OGPS I stupidly followed the advice of a YouTuber famous for his âreviewsâ of âbudget friendlyâ batteries and sold some batteries to customers that used off-the-shelf Chinese BMSâs and the BMSâs were just horrible. I only have three customers using these crappy batteries but several years later weâre still dealing with that poor decision. I have one customer with FIVE 220Ah generic batteries and Iâm very close to pulling them out and replacing them with four Pytes V16 batteries. If I take his batteries back, Iâll end up replacing the BMSâs with JK BMSâs, one iBMS, and a SmartShunt in one of our shop systems. Or, replace the BMSâs and sell them to a DIY tinkerer. I mention this to say that I might have to wade back into these waters sooner than Iâd like 
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Excellent reply, @OGPS thanks very much. Appreciated!
Edit: Regarding node red, I would like a physical button as you suggest, but also the possibility to use messages directly from the JK BMS and turn that into security switch-offs or parameter changes for the Victron gear if needed. Beginning with cutting off the batteries if I am away or asleep and a serious malfunction occurs. That type of thing in theory at least.
I do think Pytes looks like a good product. I look for one specific function in the batteries I will use in the end; I want to be able to shut them off by breaking a contact, exactly like the remote off on the MP IIâs. So far I have not been able to find a brand that delivers that from factory. Iâve seen some hacks with a jumper in the positive supply of a JKbms, but how that behaves long term: big question. My system will ha an E-STOP in 2 stages, controlled by a Schneider Electric safety relay (XPSUAT13A3AC). The direct contacts switch off the Multiplus and the Fronius. The delayed contacts switch off the solar panels and the batteries. Because the inverters al already off, there is only a little current to switch.
There are some questions lingering about the Pytes units though, maybe @OGPS can shed some light there (although that would be some nasty hijacking of this thread); On the V5 there is a connector with 1 switch input and 3 (electronic?) relay outputs. In the documentation I was able to find, there is only mention these are there, but nothing about the functions available or if its is configurable. Can you tell us more about that? I see that there is an app from Pytes in the App Store; is that of any use to set up the battery?
I want to have my battery in 5kWh chunks. Whatever brand I will choose in the end. That has to do with availability. If one pack craps out, I only loose maximum 25% capacity. That is also why I want 2 masters. You can easily string 4 packs in parallel and call it a day, but what if itâs the master that has a problem? This setup also makes it easier to add more capacity.
You mentioned that the NG batteries ar only a bit more expensive per kWh, but that is without BMS that is an extra âŹ700. And I want 2. But the biggest advantage there is that VenusOS has native support for multiple NG BMSâes. I hope that wil later expand to have support for multiple BMSâes of different brands as well. And I know that has some big challenges.
When youâve finished building, you can put the pictures in the âShow us your systemâ topic. No need to keep chatting here, just to keep the thread open.
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Interesting thoughts on security layers there, thanks. Some things align with my own ideas.
A separate switch for each battery would probably be the best for redundancy and robustness, hence the title of the thread.
I am surprised that Victron does not appear to sell battery protect/cut off relays for larger LiFePo batteries. Is that a fact or am I missing something? The batteries we plan on using are fused with a 300A mega fuse and the biggest I find is battery smart protect 100A which also does not do bi-directional currents so is not possible for this application anyway.
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