Guru
Joined: 13/10/2014
Location: AustraliaPosts: 2199
| Posted: 11:04pm 01 Feb 2024 |
Sorry for breaking up the lines below, for some reason it's forcing the view in my browser to scroll across three times the screen width if I don't?? and at the moment, only in this thread.
Hi Rodger. I thought I would chime in on paralleling MPPT solar charges.
You likely know that I've had four mppt in parallel for years, soon to be five in parallel.
I initially had one mppt feeding each battery bank.
I made sure that all mppt negative cables were the same length back to a common ground point. All battery and other charge cables were also the same length to the AC inverter connection bus.
The 60A "Make Sky Blue" mppt controllers, like most I assume, are incredibility sensitive to output voltage tracking.
The manufacture shows them connected in parallel and goes to length to emphasize equal cable lengths, that was mainly to ensure equal individual bank charging and I once did it like this.
I now have two common solar charger connecting bus bars, one for positive and one for negative, these go via 53mm2 cables directly to the Junction connections of the AC inverter and Battery connection Bus bars.
Solar charger "load sharing" tracks a lot closer than before, but that was not the reason for the change, just a byproduct.
Tracking really makes no difference to the operation of mine. I sized the panels to produce a max of 40A from each controller, this gives me plenty of headroom for solar input flaring.
One mppt may be running at 23A and the other three at say, 12A, 9A and 7A.
As soon as the load demand increases, they obviously have no choice but to start to equalize current sharing.
I would imagine that yours runs like that as well. No diodes and I have had no faults after years of running it like this.
I did calibrate the voltage display on each mppt, they use that calibrate voltage point to accurately set the mppt charge output regulate voltage.
This system runs an average of 1.5kw all day, there is some running time at 3kW and short surges up to 10kw or 13kW. In my situation, any diodes would be problematic and wasteful.
It's the "Solar chargers" that power the AC-Inverter all day long, when each battery pack charges to a set point, it disables its charge input.
So the only time the battery packs might show any discharge current is from load startup surges or from falling solar input, but for 90% of the day the solar chargers run the house and shed by themselves.
The batteries sit floating with almost no charge input and almost no discharge until the evenings, when the batteries run the property at night, repeat cycle.
.
Edited 2024-02-02 11:10 by KeepIS