Should I use 36v PV panels

[Jen-in-Wellies]

1 hour ago, Higgs said:

 

This may or may not be appropriate. I charge my electric lithium bike battery from the load output of the charge controller and feed it through a gadget that can increase the voltage to 42v. The current needs to be set and is set in line with what the mains adaptor for the bike is set to - 2A. On a battery with a low charge state, the battery would probably accept more than 2A, but it might not be healthy to allow that. 

 

As it is a dull time of the year, the charge controller couldn't meet the 2A demand, so the output of the voltage booster gadget was set to 1A, in order to maintain a voltage output. Solars are not at their best at this time of year. At this time of year, the amps are just not available in large amounts. 

 

Between now and Dec 21st, we will lose another 35 minutes of light. 

 

In the summertime, the problem will be how to use the amps available. Once your batteries are charged, the amps available will not be utilised unless there are other things that can make use of the potential of the solar panels. 

 

 

The problem is not with the number of solar panels we have, or the charge controller, or even with the sun. The problem is with the tilt of the earth and the wide swings in sun elevation and length of day that leads to. We should be doing something about that to make solar usable all year round. Every one get out of their boats and push the planet when I say. A good heave at midnight by those in the northern hemisphere and a similar effort at midday by those in the southern on December 21st  to move it upright should do the trick. 😀

[David Mack]

19 minutes ago, Jen-in-Wellies said:

Every one get out of their boats and push the planet when I say. A good heave at midnight by those in the northern hemisphere and a similar effort at midday by those in the southern on December 21st  to move it upright should do the trick. 😀

 

"Give me but a firm spot on which to stand, and I shall move the earth."

Archimedes

[magnetman]

7 hours ago, blackrose said:

 

I don't really understand why you'd need to limit the charge current of any MPPT controller? As I said previously, if the current specification of the controller (in your case 30A) is exceeded, the MPPT will simply clip the charge current coming out of the controller. It's the voltage specification of the MPPT that's the critical value not to be exceeded to avoid damaging it.

 

So what's your MPPT controller spec 30A/???V

Sorry I did miss your post.

 

100/30. 2 x 36v panels in series.

 

It can be worth limiting the current output in some situations if you actually don't need it. You can then use thinner wires.

 

Another one of my controllers is a 50a version connected to a pair of 415w panels. I do not currently need the full output from these large panels in the summer so I have limited it to 25 amps via the Victron app partly on account of the wire size from controller to battery terminals. If I required more power in future there is capacity but wire size from controller to battery would need to be increased accordingly.

 

There is an argument for overspeccing but it is also possible to underspec the controller (in terms of amps) and not have problems.

 

 

 

 

 

 

Edited November 26, 2022 by magnetman