Wulfee wrote: ↑
Sat, 02 Nov 2019, 04:41
My current firmware is 72.30, that should be ok?
Yes, that should be fine. You will miss out on whatever improvements (hopefully!) are in 72.30 but not in 72.20, but in my experience these are quite minor.
Coulomb wrote:Is your battery LFP (LiFePO₄), or other Lithium Ion?
It's home made Lithium Ion.
That doesn't completely answer the question. You might be making a home-make LFP battery. What is the nominal voltage of your cells? If around 3.2 V, then it's LFP. If 3.6 V or more, it's not LFP.
From what I was reading it looks the the non LiFePO4 firmware is better for that?
Assuming it's a 3.7 V per cell chemistry, then yes, you need the LC flavour of the patched firmware. The only difference is a handful of voltage thresholds, but it's important to choose the correct flavour.
So if I don't connect any solar panels to it, does that mean I won't be able to get it to charge from the grid at the rate I want?
Not at all. The command we've altered with the ability to specify any total charge current (to one amp resolution) is the MNCHGC command. It specifies the present total
charge current limit (PV plus utility charging). So with no PV charging, all your charging will be utility charging. So effectively, you're setting the utility charging limit, since PV charging will always be zero. So that's perfect for your needs right now.
As an example, suppose you have enough grid connected solar power to charge the battery at 23 A. You'd set the dynamic charge current to 23 A with a command of MNCHGC0523. Now suppose that you also have 10 A (battery side) of PV charge current. That same limit of 23 A will really restrict you to 13 A of utility charging. But all you have to do is use another command to find out how much PV charge current there is, and add it to the 23 A you want for utility charging. So you'd set the total current limit to 33 A, with a MNCHGC0533 command. The inverter knows to prioritise PV charge current over utility charge current, so it will figure out that the present set points should be 10 A for PV charging and 23 A for utility charging.
Actually, as I write this, I see a problem. When you measure 10 A of PV charge current, it does not mean that only 10 A is available, just that it figured out 10 A as the correct value based on the combination of availability and the settings last time it figured this out. For example, it might be able to charge at 20 A from PV, if only you had specified a larger limit. So you might need to have some sort of outer feedback loop, that guesses a current limit, measures how much utility charging results, and adjust the guess accordingly for next time. It might be possible to guess the PV charge current based on the known grid-connect charge power; you would expect that there would be an approximate constant of proportionality. Or, you might choose to put all your PV panels on your existing grid connected inverter, just to simplify things.
Thinking about this a little more, it might not be a problem at all. Let's take the example again of 23 A of utility charging, and 10 A of PV charging. You have the limit set at 33 A. Let's say the sun comes out from a light cloud, allowing about 10% more PV power. So now you have 12 A available from PV, and 25 A from utility. You only update the limit every 15 seconds (say), so at the end of that period, you have 12 A of PV charging and only 21 A of utility charging. The extra PV charge current has "robbed" the system of 2 A of utility charging. But next cycle, you set the limit to 12+25 = 37 A, and all is well again.
The main problem might be when the available solar power changes a lot. Let's say there is bad cloud, and you have 3 A of PV charging and 5 A of utility charging. Limit is 8 A. The sun comes out from behind a cloud, and suddenly there is 20 A of PV available (but you don't know that yet), and 30 A of utility charging. You'll get 8 A of PV charging at the end of this cycle, and no utility charging. You will set the limit to 8+30 = 38 A, which will result in 20 A of PV and 18 A of utility charging. You'll miss out on 30-18 = 12 A of utility charging. By the start of the next cycle, the cloud edge effect is gone, and you have 15 A of PV available (you do know this now, since the PV emasurement isn't "clipped" by the limit), and 25 A of utility charging. So you set the limit to 15+25 = 40 A, and end up with 15 A of PV and 40-15 = 25 A of utility charging. [ Edit: in other words, this cycle is exactly correct, and the effect of the sudden jump has already gone. ] So you end up with one period of sub-optimal performance, and only when the present limit is lower than the available PV power (which I'd say would be quite rare).
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.