I would like to get a recuperative charger so that I can feed the energie back into my PV batteries when measuring small LFP batteries.
Since I’m using a smart shunt as an energy meter at the output, I have to route the negative terminal back through it. I would then need to take the positive terminal from the battery or after the battery fuse.
Now to the question: is the negative
connection in the SmartSolar continuous (no electronic components in the current path from “Load” to “Battery”), or is there perhaps something installed that doesn’t like being fed back from Load to Battery?
Can you draw some simple connection diagram of what you’re trying to achieve? If I understood you correctly, you need an adjustable DC step-up converter with a configurable current limit. What I don’t really understand is why you need a Smart Solar in this setup.
If the Smart Solar is supposed to act as a charge controller, then your PV battery has to be connected to its battery port. The small LFP battery, via a boost DC-DC converter, would then go to the PV port of the Smart Solar. In general, this will work, but it feels like you’re unnecessarily over-complicating the whole setup.
With this kind of connection, the Smart Shunt has to be placed right after the small LFP battery but before the DC boost converter.
In general, what you’re trying to do is completely unsupported by Victron in any way, and there’s a fairly good chance that something will go badly wrong. That said, I think I know what you’re trying to achieve — I’ve experimented with similar setups myself in the past
The charger is a standard RC charger with recuperation (it can be set as a CC/CV source). Therefore, the question specifically concerns the arrow (current flow at the negative terminal through SmartSolar), which would flow “in reverse” during recuperation.
And that is precisely my question: does this current flow in the other direction affect the SmartSolar?
Please write down which device models you have. I assume the main battery is connected to the battery terminal on the SmartSolar controller and everything else is connected to the load terminal? If so, that won’t work. The SmartSolar will not pass energy in the reverse direction. Why the positive lead of a charger is connected directly to battery and not the positive lead of dc loads?
Instead, you should connect the battery under test and your charger to the PV input of the SmartSolar. A shunt won’t be needed, as the SmartSolar will accurately measure the amount of energy produced (delivered by the tested battery).
I see two issues with this approach. First, you will need to switch between the PV and Load terminals between charge and discharge cycles. Second, during discharge of the tested battery, your charger must supply the SmartSolar with a voltage at least 5 V higher than the main battery voltage.
Once again, I want to emphasize that what we are discussing here is completely unsupported by Victron, and in case of any problems you may lose the warranty on your devices.
Because I assume that the negative terminal in the SmartSolar is simply looped through, meaning there’s no electronics “in the way”.
The shunts are from an earlier time (before I installed the Victron charge controller) and therefore I still use it there as an energy meter.
I understand that this entire circuit is somewhat unusual, but in my opinion it should work this way (provided the negative terminal of the SmartSolar is simply a continuous wire, at least in the path from “Battery” to “Load”). Otherwise, someone from Victron would have to confirm that this connection is just a conductor and contains no electronic components.
The charger would simply be looped through the shunt, and its energy consumption would also be included.
We’re really in uncharted territory here. That being said, I’ve checked one of the SmartSolar units I had at hand (MPPT 75/15) with a multimeter. In this particular case, there is a direct connection between the “–” terminals of the battery, PV, and load terminals.
Which version of the charge controller are you using? I don’t think anyone from Victron would be willing to confirm or deny anything we’re discussing here.
