Please help mpp LV2424 not charging

[gdpetti]

What happens if the 3 panels in series produce over 115v that the MPPT solar charge controller can handle? Does the MPPT just shut down, burn out..? Or as Hunter937 discovered, voltage goes in but nothing comes out? Shutdown? Does it restart on these units automatically? the solar controller is on even if the inverter is turned off, correct? and why we need a breaker/shutoff switch on the wires going in?

The "Y" connector is interesting.... sort of like purposely shading the beginning of the one panels cells? not sure if that would be top or bottom, wherever the cell's series starts... right? to limit the current just enough to keep it within the MPPT range up to 115v... either way is bothersome, but a factor of using these All-in-Ones it seems.

 

[Hedges]

Since max Voc spec is 145V, exceeding 115V by a bit won't cause damage. Voltage in but no current out. It probably starts up automatically after the panel warms in the sun and voltage drops under 115V.

Didn't think about deliberate shading. Yes, just covering one panel would drop the voltage under 115V so it could start. Whether that is acceptable for an extended period of time depends on whether bypass diodes in the panel were selected and heatsinked adequately. Reportedly some brands of panels can't tolerate that.

If you're going to be away for a long time so total consumption is lower but you need a fridge operating, having 2 panels in the circuit should be reliable. If you're there and just want it to kick in, shading the 3rd panel briefly should do the trick. Panels are so cheap these days I'd just get 4 panels and do 2s2p. I'm orienting strings in multiple directions now. Panels are cheap, batteries are expensive, so I want to spread production out over more hours of the day rather than for maximum peak production.

It is good to have disconnect switches to interrupt current flow before you unplug panels. The MC connectors aren't rated for make/break.

 

[gdpetti]

So, series connection of 3 panels is really only a problem with this unit in ideal conditions? Is that the experience of most solar panels in use? They don't usually go over their Vmp do they? Do they often go near their Voc? let alone go over it? I'm wondering if this is a problem or something to only worry about when in ideal conditions? In which case, it would only be for a few hours at peak conditions of full bright sunlight in somewhat cool weather... isn't that right? Heat causes the voltage to drop some as the panels heat up... I wonder if Hunter937's charge controller turned back on by itself after such 'ideal conditions' passed? Or perhaps his system was too far over the specs of the MPPT range? In my case, that overage of specs, would only be for a limited period of time most likely... so perhaps I should just series connect and keep watch for those times that could shut the controller down temporarily? As long as it doesn't harm the controller that is.

 

[gdpetti]

Just trying to setup the system in K.I.S.S. manner so I don't have to think much about it... if possible, which is why I liked the idea of the All-in-One's to begin with... the 'plug and play' aspect.. appealing, but comes with its limitations and problems that I didn't realize existed until this thread showed up.. I just thought there was plenty of range on the unit... but it seems there isn't. So, now, the issue is whether that is a problem most of the time or only rarely when/if I boondock down south in full sunlight days.

 

[mrdavvv]

What happens if the 3 panels in series produce over 115v that the MPPT solar charge controller can handle? Does the MPPT just shut down, burn out..? Or as Hunter937 discovered, voltage goes in but nothing comes out? Shutdown? Does it restart on these units automatically? the solar controller is on even if the inverter is turned off, correct? and why we need a breaker/shutoff switch on the wires going in?

The "Y" connector is interesting.... sort of like purposely shading the beginning of the one panels cells? not sure if that would be top or bottom, wherever the cell's series starts... right? to limit the current just enough to keep it within the MPPT range up to 115v... either way is bothersome, but a factor of using these All-in-Ones it seems.

You shouldnt overvoltage the MPPT's, indeed they can burn, also the voltage (VOC) could increase in low temperatures so its advise able to leave some margin:

Sizing an array for MPP Solar LV2424

I was thinking that maybe the 2000W PV input limit its based on the 80A maximum power that the MPPT can supply to the batteries. So in that case and according to the guys or the link that i posted, we can safely go little bit higher...

diysolarforum.com

 

[Hedges]

It doesn't take much light to get fairly near full voltage. It does take full light to get full current.
Voltage varies with temperature and unit to unit variations. It has to do with electron carriers in a diode - they are thermally excited away from their atom and become available to carry current. Hot panel, more carriers, more current gets carried across the diode for a given voltage.

Your situation is right at he edge - specs add up to 120 Voc and charger will only operate up to 115 V. As the sun comes up in the morning it should start working before voltage ever gets that high, and so long as current is being drawn it'll stay below 115V. Once batteries are full and current draw drops to zero, on a cold day it may exceed 115V so the charger stays off line until voltage drops in the afternoon/evening. Perhaps not a big deal if you don't need high uptime from an unattended system.

K.I.S.S.

Here are pictures from a test I just ran. Voc was a bit below label, but Isc went 15% over!

 

[iceledoar]

Thanks for your reply, It is powered by 4 100ah 12v lithium ion batteries. I originally booted it off of the batteries. And my settings are as follows

I would try taking it out of power saving mode.