Solar Array Help – III

Sorting out Solar Power is really not hard, when you can get the facts. The problem is the “do the thinking for you” attitude that has cropped up as a result of Snowflakes demanding it. Wading through the “user friendly” bullshit in search of reality is really hard, because the whole point is to hide reality and insulate the Snowflakes so they don’t get triggered, cry, demand a refund, and leave a bad review; all because they’re so stupid they can’t figure out anything, ever. And., worse, instead of learning, they believe they’re entitled to not learning and forcing someone else to do everything for them.

While I admit I haven’t been applying myself full-time to the project, I’ve finally got it sorted out.

MidNite Solar Kid.
Salvaged Chevy Volt (LG Chem) Batteries.

Kids can be daisy-chained and made to work in parallel.

But, wait. The Kid has no way to handle Lithiums as they want to be handled.

Wanna bet?

We really can’t expect MidNite to come up with a preset for everything. Especially not salvaged batteries which were never meant for this.

The full range of the LG Chem Lithium cells is 4.15v to 3v. They’re perfectly linear between 4 and 3.5, at a slant which covers 80% of their capacity!

You can’t use 80% of a Pb/H2SO4 cell if you want it to last more than a month.

4 * 12 = 48

3.5 * 12 = 42

A “12v battery” means 12v nominal. They actually charge at significantly higher voltages. This won’t be a problem, though, because the Kid can be set to nominal = actual. So this is a non-problem.

The PICOGLF12KW48V240VS has two source-power priority modes which simultaneously select two different voltage ranges. It’s still Pb-centric, but since we’ll never hook this up to any A/C input power, and always run on battery no matter what, it essentially gives us two voltage ranges. This also means the not-gonna-work-at-all charger doesn’t have to be worried about. One of those select-able ranges is 44v for Low Batt Warning, and 42v for Low Batt Cut Off. The Low Batt Warning also triggers the built in contactor that could be used to start a generator. It can carry 16 amps, not that I care…

So, the major hurdle is nullifying some of the features in the Kid that are used for Pb but which would destroy a Lithium.

BULKMPPT mode is “Pump all of the amps!” mode. This is default behavior.
BULKMPPT mode stops when the ABSORB voltage is reached.
ABSORB continues for a specified ABSORB TIME. If ABSORB TIME is set to a number appropriate for Pb, it would kill Li.
Once ABSORB TIME is reached, FLOAT is triggered.
FLOAT is a perpetual trickle charge meant to combat natural failings inside Pb cells which do not exist in Li cells. If allowed, FLOAT would destroy Li cells.
REBULK is the point at which we tell the Kid to go back to “Pump all of the amps!” mode. Set REBULK to 45v
We go in a circle.

So, just do this:

Set ABSORB value to 48.1v.
Set ABSORB time to 0.
Set FLOAT to a value drastically below anything the battery could ever reach. It will never happen because the battery is at 48.1v when this condition is checked.
We go directly to IDLE mode. The Kid just sits there waiting for the batteries to reach REBULK.

Exactly what we want for our salvaged LG Chem Lithiums; dump all of the amps until 48.1v, then do nothing until it’s amp dump time again. We’ll have to do some re-wiring… But, we don’t have to break the bricks, and the really cool native cooling system stays intact. I’ll probably re-stack them with allthread…

One may notice that the REBULK voltage is set to 1v above the Low Batt Warning/Gen Start trigger. Won’t sag give you a false positive? Not really. You’re thinking like Pb again! These totally badass LG chem batteries can deliver 350KW pulses out of a mere 16KW pack without sag! I’m going to have 4x of them. So, I’d have to have a 1.4MEGAWATT load to induce a false trigger. The PICOGLF12KW48V240VS would blow up at 0.036MW (it’s surge capacity is 3x rated). So, not a problem.

Aux charger and generator are not selected. I’ll probably just use that cheap 8KW China Freight Generator. I have the smaller version and it’s badass little machine if you know a few simple tricks. I bought the 8KW for my parents, and it’s every bit as badass. It’s no Listeroid, but that’s an upgrade for another day…

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