Question on sizing from Panel to Batteries.

[nikitis]

I had purchased solar panels and MPPT Charge controller and a 3000W inverter years ago. I haven't used them for anticipation of a solar project later or in preparation in case there was a Doomsday event, I'd have SOME power, even if only a little bit. (Somewhat of a prepper), and now I plan to use this stuff on my Bus.

I just went through my inventory of what I had to see if anything was dated or not usable with a modern solar setup used today, and everything looks good except maybe the MPPT charge controller, I think the voltage is sized right, I want a 24V System, but the max amperage seems low, 60Amps, They are 320 Watt panels, times 6 panels, so 1920 Watts total.

1920 Watts divided by 24Volts, = 80 Amps. My MPPT states it does 60Amps. So I may have undersized my MPPT.

Though I do have a question if anyone can answer for me as electrical is my weakest area. The panels though 320 watts, show a configuration of 9.50Amps of operating current, which times 6 would be 57 Amps, and a max of 10 Amps which is 60 Amps, The panels also show 33Volts operating and 40volts Max, so maybe it's not quite 24V, but slightly higher configuration to work at 60 Amps and is likely why I went with it originally. So I'll be maxing it out, but I think it is within spec? Anyone disagree?

Higher output voltage on panels = lower amps

So if it's sending out 40V maximum, 1920W/40V = 48Amps, which is under spec at Maximum, and 33V which is the operating voltage under load = 1920W/33V = 58.18Amps. So I think I'm good there?

Let me know if anyone disagrees


And I guess the MPPT Charge controller as long as not going over the input Amps, will charge the batteries at 24V? Or what is required to get that?

 

[Danjo-SKO]

Might be helpful to list the make/model or sticker from the controller and from one of the panels

 

[Rucker]

Might be helpful to list the make/model or sticker from the controller and from one of the panels

Yes-that's needed because it's also things like max voltage.

 

[nikitis]

Here ya go. It's a Chinese knock-off brand from like 3 years ago and it's the 6015F model. (It lists a couple of different models they sold). I see on the silver sticker it states 32V for 24V Battery system, and Max Solar Voltage is 146V.



And in the other picture is the Renogy panel that states it's 33V operating, 40V max.

 

[Banjo Joe]

I think you'll want to wire the solar panels in a Series/Parallel configuration so that the voltage and amperage is within spec of the CC. DIYSolarForum has all the answers for you. With MPPT charging, the panel voltage should be higher than the battery voltage for efficient charging.

 

[Jono14]

Should work

An MPPT solar charge controller (SCC) generally has 2 ratings:
1) The maximum input voltage (this is a hard stop and voltage over this rating can break the unit)
2) The output maximum amps (this is the 60A cap where if your panels are producing enough watts that more amps could be flowing to the battery, the SCC will just cap out and nothing is injured.

For your 60Amp unit, you should be fine on the amp side. In reality, your panels are unlikely to reach maximum in most real life conditions and the Victron MPPT selection site recommends a 60Amp SCC for your 6 panels when configured either 2 parallel strings of 3 in series or 3 parallel strings of 2 in series.

However, I am not sure if the MPPT SCC can handle the voltage - you should see if that rating is listed. 2 series panels give a Voc of about 80V so might be OK if the MPPT can handle 100V (got to figure some headroom of at least 25%). If the MPPT can do 150V then you could put 3 panels in series (or be very safe with just 2 in series.)

You can also do all 6 panels in parallel, but that is a lot of amps for standard solar wiring and MC4 connectors so better to have some in series as Banjo Joe stated.