Energy Tariffs

[Stinsy]

Running multiple charging sources to one lithium battery pack has to be done carefully. You don't want both inverters being told by the battery BMS that the max charge rate is say 100A and 200A going into the pack.

The easy way to do that is to have all the batteries connected electrically, but split into two pack electronically.

For example if you had 6x US2000 batteries you'd have them set up as 2x stacks of 3, from a data perspective each reporting to their inverter a max charge/discharge rate of 75A (25a per battery). However the batteries would really be in a single stack and would charge/discharge as one.

That doesn't work unless you have both inverters of the same capacity, the same amount of PV on each and in the same orientation- otherwise you could get limitation in charging.

I don't see the problem!

In my example each inverter could charge/discharge the battery pack at 3.6kW. That is plenty! I have a 5kWp array and my inverter can charge/discharge the batteries at c. 3.4kW, I've never found it limiting. A diverter for a DHW tank, BEV, or SH would solve the problem if you had bigger arrays.

[Tinbum]

More importantly what happens if you get one BMS reporting an error with its pack- the other inverter wouldn't get the message and would carry on charging.

[Oldgreybeard]

More importantly what happens if you get one BMS reporting an error with its pack- the other inverter wouldn't get the message and would carry on charging.

I'm pretty sure that the Pylontech BMS just shuts the battery down if there's an error. There is definitely a "soft" switch in the battery packs, as they turn on and off by a command from the button on the master battery, plus the on/off switch on each battery isn't a power switch, it just tells the BMS to disconnect the battery from the terminals, I believe.

[Tinbum]

More importantly what happens if you get one BMS reporting an error with its pack- the other inverter wouldn't get the message and would carry on charging.

I'm pretty sure that the Pylontech BMS just shuts the battery down if there's an error. There is definitely a "soft" switch in the battery packs, as they turn on and off by a command from the button on the master battery, plus the on/off switch on each battery isn't a power switch, it just tells the BMS to disconnect the battery from the terminals, I believe.

Yes, That's as I understand it. (It wasn't meant to be a question. ) That is a last resort.

If say the inverter developed a fault where it went overvoltage the BMS can shut it down before any damage. Pylon batteries only have to go to 54.5v before a new bms is required. Pylontech put the CAN communication in their batteries for a reason, yes they have fail safes in the battery but that's what they are fail safes.

[Oldgreybeard]

So, as long as the second charger is set to not exceed the maximum charge voltage then all should be fine. Setting the second charger to charge to maybe half a volt less than the cut-off voltage of the first charger should be safe enough. The second charger would be fine during most of the charge, but when the battery gets to within a few percent of fully charged that second charger will just stop charging and the first charger can carry on to 100%, under CANBUS control from the battery BMS.

[Joeboy]

With my current systems the Victron charge controller is set to cut out at 52.3v. I will have to check and see what voltage the Goodwe hybrid unit pushes the Pylontechs to. Meant to do that for yonks!

[Tinbum]

What you need to do is intercept the CAN message from the, single, battery pack and then adjust it and resend them out to each inverter, which is what I do. All my chargers receive messages from the BMS, so are controlled by it, but receive a corrected message depending on what the other chargers are doing.

[nowty]

I'm keeping out of this one.

[Stinsy]

I'm keeping out of this one.

Is this where we find out your next-door-neighbour is on Octopus Outgoing?

[nowty]

I'm keeping out of this one.

Is this where we find out your next-door-neighbour is on Octopus Outgoing?

Maybe,