Solar Panel Efficiency?

[B27]

Yes in any mode. Acceptance rate is a hard limit on the battery. you can’t just ram more juice in to a battery. Chemistry doesn’t work like that. For normal installs you won’t usually notice but as solar banks get larger it’s a huge issue for small lead banks.

There are plenty of V/I curves published for lead acid batteries as a function of state of charge.
The OP is only talking about ~70A into 630Ah of batteries, that's not much more than 0.1C or a 'ten hour rate'. At that current the the batteries would have to be over 90% charge for the voltage limit to kick in.

Acceptance of a battery is largely a myth, you can shove in what current you like, it just takes more volts. And the charge that goes in may be stored with less or more efficiency.

 

[lustyd]

Or it’ll boil the battery it is 630A but it’s only 3 batteries.

 

[B27]

Or it’ll boil the battery it is 630A but it’s only 3 batteries.

630Ah, ~75A.

Modern cars can often poke in 100A to a 60Ah battery with a start stop ecobollocks system.

Even my 1965 car with its dynamo would shove 30A into a 50Ah battery, for a while!

 

[vas]

OP can then do a simple test:
Go to the boat after his morning coffee, run the calorifier for an hour. Turn off MPPT (easy to do with the BT and victron app).
Then turn on the main battery charger for half an hour and note how many amps that manages to pump into the bank If the charger is large (don't remember if it's discussed before) it will be a similar #
Then turn off charger, keep the calorifier on and turn on the MPPT at 12:30, note where it peaks at around 1:00, job done.

Obvs if the charger is a 30A, I've been typing bllx...

V.

 

[lustyd]

Modern cars can often poke in 100A to a 60Ah battery

Modern cars use a 100A alternator to push 30A into a 110Ah battery. Cars with 60 Ah batteries have tiny engines and alternators and couldn’t hope to output 100A

 

[PaulRainbow]

Easy to test if the batteries are taking all of the solar yield when in bulk, or at any other time. Watch the output from the controller and turn something on, like lights etc. If the yield goes up the batteries were limiting the yield, simple !

 

[Irish Rover]

I assume they are flat on the coachroof?

Yes, on the flybridge hardtop

600odd W must be 2.5X1.something is size right?

2.3 x 1.15

How long are the runs and are the cable sizes ok so there's no serious voltage drop (not that it would matter much @90V)

6/7 m and 1.5mm² cable

No mast, no sails, so no shadows (even tiny ones drop massively!)

No obstructions worth mentioning, all done in the marina, nothing significant nearby.

I expect that you get the values from the Victorn MPPT app, check history tab for the next few days,

I checked the history tab yesterday after I posted and saw I had 888W highest so that's not terribly out of line with your experience.
Thanks you very much for your input. It made me feel a good bit better about our results.
I'm going to leave things as they are for now, but my son and I were discussing the possibility of raising the panels in the centre [they're side by side fore to aft lenthway] to give a 20/25⁰ aspect and changing the connection to parallel. We may experiment with that on his next visit.

 

[vas]

6/7 m and 1.5mm² cable

what do the experts think?
isn't 1.5mm2 (AWG15?) a bit thin for a 14m trip of 90VDC @12-15A (at summer peak)?
If I got my numbers right, voltage drop calculator gives me 5.2% drop of 4.5V which is a fair bit.
IIRC for a similar run iirc I'm using AWG6 plated cable with the right expensive push-on connectors (the ones that panels typically have on their stubs)

V.

 

[lustyd]

I got 2.5V drop or about 235W lost. Personally I’d upgrade that cable to make the most of the panels

 

[andsarkit]

6/7 m and 1.5mm² cable

Are you sure this is the size?
Have you noticed any smoke coming from the cables yet.

 

[vas]

I got 2.5V drop or about 235W lost. Personally I’d upgrade that cable to make the most of the panels

hm, when calculating voltage drop on DC, don't we double the distance as in AC or I got that wrong?
no matter what if cable is that thin, it needs updating for sure!

 

[lustyd]

hm, when calculating voltage drop on DC, don't we double the distance as in AC or I got that wrong?
no matter what if cable is that thin, it needs updating for sure!

Depends on which calculator you use. 12vplanet wants one way distance.

 

[billskip]

Depends on which calculator you use.

You either do or you don't...which is it?
Or don't you know?

 

[PaulRainbow]

Depends on which calculator you use. 12vplanet wants one way distance.

It asks for one way, but uses the total return journey.

 

[PaulRainbow]

Are you sure this is the size?
Have you noticed any smoke coming from the cables yet.

They won't smoke, not with solar panels, they just loose lots of volts.

 

[PaulRainbow]

You either do or you don't...which is it?
Or don't you know?

The data that you input varies from calculator to calculator, but to make the calculation, the calculator will use the total length there and back.

 

[lustyd]

You either do or you don't...which is it?
Or don't you know?

I do know. You have to read the instructions for the calculator you’re using because some double the number and some don’t.

 

[billskip]

I do know. You have to read the instructions for the calculator you’re using because some double the number and some don’t.

It's got nothing to do with a calculator....
You either get a voltage drop across the whole circuit or you don't...which is it or don't you know?

You should really know what you are talking about before giving advice....

 

[PaulRainbow]

At (round figures) 100V @ 15a i make it about 2.5v drop.

But, that's the absolute max with 2x625w panels in series. Or, 100v @ 7a = 1.25v

Either way, i'd upgrade the cable to 4mm sq

 

[PaulRainbow]

It's got nothing to do with a calculator....
You either get a voltage drop across the whole circuit or you don't...which is it or don't you know?

You should really know what you are talking about before giving advice....

Why are you so rude and ignorant ?

It's already been explained how some calculators work.