MTTP with low Volt load disconnect

[mrzed001]

Hi

One of my friends want to make a small night light system (offgrid).
Already has:
- 1 piece 305W 40Voc solar panel
- 1 piece 12V lead battery 70Ah
- 1 piece 12V LED street light (self regulating with night switch and movement detector)

So he needs an MPPT (30-40A output).
Will this be too much for a 70Ah lead acid battery ?

Yes, he could wire the lamp directly to the battery, but then if it needs to work all night then the battery will be over discharged.

Is there an MPPT that has 3 connector:
- PV
- Battery
- Output load (to lamp)

So if no PV (night) and battery voltage is down then it disconnects the load ?
(maybe smart with bluetooth settings )

Thanks

 

[snoobler]

Hi

One of my friends want to make a small night light system (offgrid).
Already has:
- 1 piece 305W 40Voc solar panel
- 1 piece 12V lead battery 70Ah
- 1 piece 12V LED street light (self regulating with night switch and movement detector)

So he needs an MPPT (30-40A output).
(1) Will this be too much for a 70Ah lead acid battery ?

Yes, he could wire the lamp directly to the battery, but then if it needs to work all night then the battery will be over discharged.

(2) Is there an MPPT that has 3 connector:
- PV
- Battery
- Output load (to lamp)

So if no PV (night) and battery voltage is down then it disconnects the load ?
(maybe smart with bluetooth settings )

Thanks

(1) You haven't told us how much power the light consumes and for how long it will be drawing power.
(2) Yes. Many do. Whether they have low voltage load disconnects is the question.

The panel is too big for the battery. 70Ah battery should be charged at 7A. 305W/12V = 25A

Start over. Find out how much power you need and for how long. That determines battery and panel.

 

[mrzed001]

1) even the guy does not know it (yet) ... and not even if it needs 12V or 12V regulated
2) Yep, that is the question ... witch one (MPPT) has low voltage disconnect ?

In this case he already has items (solar panel, LED, battery), and needs a solution to use it.

For the charge, I can say to buy 3 more 70Ah battery and use them parallel (280Ah), so 7A x 4 = 28A ... and that is lower than max 25A charge from MPPT.

 

[snoobler]

Given the existing purchases, it would probably be better to buy a charge controller that can restrict charging output.

The Victron 75/15 should do everything needed stated thus far:

https://www.victronenergy.com/upload/documents/Datasheet-SmartSolar-charge-controller-MPPT-75-10,-75-15,-100-15,-100-20_48V-EN.pdf

It's load output is limited to 15A, so 12V * 15A = 180W is the most output it could provide. Hopefully, that's more than enough.

Bluetooth app interface, monitoring and control. Read datasheet and manual to ensure it meets your need. I would not purchase until you've identified the light.

Alternatively, there are much cheaper controllers without that feature. You could connect direct to the battery with some kind of timer or light sensor to prevent use during the day.

 

[mrzed001]

I think load output is more than enough. And it can manage it, so that is great !

So this can limit the charge current for the battery (for 10A) and not use all the 305W (Voc=40V, so maybe 35V 9A) that the solar panel is generating ?

Thanks