Two separate arrays with different specs in parallel?

[lmichel]

I have an existing RV mounted Lifepo4 system that I'm trying to integrate a new Ecoflow Delta Pro + extra battery into.
The current system has 420Ah at 14v connected to 2 inverters. It also has two individual arrays, each going through its own MPPT controller (Outback FlexMax 60) to charge the LP4 bank.
- One array is always active and consists of a series string of five 165W, Imp 9A, Vmp 18.22v, Isc 9.61A, Voc 22.32v panels.
- The other array is only 4 of the same panels and active only when parked and deployed at a campground.
Because of the charge controllers, BOTH arrays always put out 14.4V at whatever amps they can pull from the available light. So I can connect them in parallel to the LP4 BMS and all is well.

- The head scratcher -
The EF DP only has a single solar input port and only draws a max of 15A.
Ok, Fine, I'll sacrifice a few amps (18A-15A = 3A waste?) if I were to just bypass the MPPTs and wire both arrays in parallel directly into the DP solar port.

BUT, how will the DP react to having two arrays connected in parallel to the same port, each with differing voltages? Typically, the 5-panel array is at about 80v and the 4-panel array at 68v.

Will the 80v array drop to 68v? Won't that strain one array or the other?

Changing either array to match the number of panels in both would be a major PITA and is a dead last resort.

I can't run the arrays through the FlexMax CCs and feed the same V to the DP, because they're powered by the batteries they normally would charge and the DP solar input port won't be providing that.

Thoughts?

Thanks!

 

[Hedges]

I have an existing RV mounted Lifepo4 system that I'm trying to integrate a new Ecoflow Delta Pro + extra battery into.

Oh, add "Solar Generator" to existing system?
How many Ah in existing system?
Does existing system have inverter?

The current system has 420Ah at 14v connected to 2 inverters. It also has two individual arrays, each going through its own MPPT controller (Outback FlexMax 60) to charge the LP4 bank.
- One array is always active and consists of a series string of five 165W, Imp 9A, Vmp 18.22v, Isc 9.61A, Voc 22.32v panels.
- The other array is only 4 of the same panels and active only when parked and deployed at a campground.

5x 18.22V = 91.10 Vmp, 5x 22.32V = 111.60 Voc
4x 18.22V = 72.88 Vmp

Because of the charge controllers, BOTH arrays always put out 14.4V at whatever amps they can pull from the available light. So I can connect them in parallel to the LP4 BMS and all is well.

Charge controllers put out whatever battery voltage is, up to their programmed voltage. Two MPPT can be put in parallel, or I suppose two PWM. Maybe MPPT and PWM can also be mixed. I don't think I'd use PWM with lithium.

- The head scratcher -
The EF DP only has a single solar input port and only draws a max of 15A.
Ok, Fine, I'll sacrifice a few amps (18A-15A = 3A waste?) if I were to just bypass the MPPTs and wire both arrays in parallel directly into the DP solar port.

Echo Flow Delta Pro "Solar input port", what is that? Specs?

You have to watch out for PV Voc, which rises on a cold day. You're already at 111.6V, and that may go up 15% in cold weather.
Some systems can't handle excess current.

Two arrays of different orientation won't have max current at same time, so that could reduce 18A to 15A or below, nothing lost.

I'd rather keep the panels going through Outback Flexmax. Why do you want to take arrays off those?
("Oh", above)

BUT, how will the DP react to having two arrays connected in parallel to the same port, each with differing voltages? Typically, the 5-panel array is at about 80v and the 4-panel array at 68v.

Will the 80v array drop to 68v? Won't that strain one array or the other?

Changing either array to match the number of panels in both would be a major PITA and is a dead last resort.

Arrays in parallel, 5s || 4s, will behave about like 4s2p.
I think you can get away with that.

The lower voltage array will sink a bit of current from the higher voltage array when MPPT SCC is not drawing current.

No great harm - I connected two panels in parallel with one in full sun, one in a dark room, and current draw was so low as to not be useful for my experiment. I then connected two panels in series in full sun, paralleled that 2s || 1 in dark room, and current draw < 50% of Isc. (looking for IR illumination.)

I can't run the arrays through the FlexMax CCs and feed the same V to the DP, because they're powered by the batteries they normally would charge and the DP solar input port won't be providing that.

Maybe you can switch some PV from FlexMax to DP.

If you have existing inverters, how about let FlexMax charge from AC input?

How do you plan to utilize power draw from both FlexMax and from Delta Pro?

 

[lmichel]

DP input port specs: 11-150V, Max 15A draw.
I can siphon some energy from the CCs, but it would have to be at 14.4v though. So that's a crummy 14.4 X 15 = 216W. Hardly worth it.
The LP4 bank BMS only takes 12.0 - 14.6v but up to 400Amps! So I can pump over 5kw into that bank except the FlexMax's are limited to 60A each, so 120A total. However it's usually around 600w with both arrays.
FlexMax requires some DC input showing up on the charge lines to adjust their output voltage to the programmed level. Ultimately, it would have been great to change the programming to 48v(58v) and hook them up to the DP (58 X 15 =870W). But they won't latch up until they see the 48v-ish at the charging side to send to. The DP port doesn't output any voltage to be detected by the CC. The LP4's do.

Knowing that I am unlikely to damage anything by connecting the two arrays in parallel to the single input port is helpful. It might be worth a try. I can then maybe 'obsolete' the FlexMax's, reconnect the arrays directly to the DP and then use the DP AC output to a DC charger to charge the LP4 bank. It sounds like the worst that I'm doing is wasting about a panel's worth of energy from the 5-string..
Thanks!

 

[Hedges]

DP input port specs: 11-150V, Max 15A draw.
I can siphon some energy from the CCs, but it would have to be at 14.4v though. So that's a crummy 14.4 X 15 = 216W. Hardly worth it.

I think that is up to 15A x 150V = 2250W. But that is a product of maximums. Is there a spec for charge rate from that port?

Since you have 4s portable panels 72.88 Vmp, 72.88V x 9A Imp = 656W. Or both arrays in parallel maybe 72.88 x 15A = 1093W

The LP4 bank BMS only takes 12.0 - 14.6v but up to 400Amps! So I can pump over 5kw into that bank except the FlexMax's are limited to 60A each, so 120A total. However it's usually around 600w with both arrays.

14.6V x 60A = 876W peak

It sounds like the worst that I'm doing is wasting about a panel's worth of energy from the 5-string..

If wired in parallel permanently, you could repurpose one panel, have the others 4s2p.
Alternatively, if one string often gets partial shading, 5s || 4s could perform as 4s2p with some shade.