48v Mppt controller

Re: 48v Mppt controller

I don't believe you will find anything out there that will play with "off the shelf" parts.

The 48 volt battery bank needs a solar array with Vmp>~70 VDC minimum.

In my limited experience, I do not know of any >200 Watt Vmp~70 VDC panels out there.

I don't think there is any solar charge controller (off the shelf) that can "boost" a low Vmp-array voltage to the >60 volts needed to generate a 48 volt battery bank.

Most high voltage panels are either 60 or 72 cell panels (~30 volt or 36 volt Vmp). It would take two to three of these panels in series to get Vmp-array>70 volts. Or 4x 36 cell (Vmp 17.5 volt) panels in series (typically ~140 Watt or smaller, and these panels are more expensive on a $$$/Watt basis).

What may be the cheapest is 4x ~140 watt panels in series with a Xantrex/Schneider C40 PWM charge controller (more expensive panels, cheaper charge controller).

But 2-3 of the Vmp 30-36 volt panels in series with a Midnite Kid MPPT controller may also be cost effective too.

I do not think you can meet your cost goals either way--Unless you can find some used panels cheap locally.

Also, check the price delivered to your front door--Especially solar panels. Panels are expensive to pack and ship in less than full pallet loads at a time. Panels over ~140 Watts usually need to be shipped by truck.

Of course, you can try EBay and Amazon for panels and controllers--Some of their prices are hard to resist (may include shipping in some cases).

-Bill

Re: 48v Mppt controller

Then you are looking at 4x 50 watt 17.5 Vmp panels in series... about $3 per watt from our host (larger panels are $2 per watt, or even close to $1 a watt for ~200+ watt panels).

Amazon appears to have a bunch of 50 Watt panels for less than $90 shipped... Don't know anything more about them.

-Bill

Re: 48v Mppt controller

If you go around 70-80 volts Vmp-array--Then any PWM or MPPT controller will work fine (assuming they support 48 volt battery banks).

Before you start picking/buying hardware, you really need to figure the basics of what you want power wise.

For lead acid batteries, around 5% to 13% rate of charge works well with solar. If you discharge daily, you may want 10%+ rate of charge minimum.

Also, how many Watt*Hour per day you want to drive, and how many Watt*Hours per day from the panels.

Will you also have an AC/backup battery charger too?

For the most part, it is difficult to have a workable electric vehicle that will get sufficient energy just from solar on its roof.

200 Watts of solar may push a reasonably efficient vehicle (like a golf cart/car):

• 200 watts * 0.52 charging eff * 4 hours of sun * 1/300 WH per mile = 1.4 miles per day in reasonable sun

If this is a very efficient recumbent trike --you might get as much as (flat ground, no wind?):

• 200 watts * 0.52 charging eff * 4 hours of sun * 1/32 WH per mile = 13 miles per day in reasonable sun

-Bill

Re: 48v Mppt controller

By the way, I had a typo in an earlier post... I typed "4 Days of Sun" per day, I have corrected it to "4 Hours of Sun".

What is the Amp*Hour rating of the battery bank? Are they Lead Acid (flooded cell, AGM, or GEL) or some sort of Lithium chemistry?

Using PV Watts for Miami, flat mounted array (zero tilt), the daily sun looks like:




Month
Solar Radiation
(kWh/m²/day)


1
3.48


2
4.41


3
5.16


4
6.15


5
6.02


6
5.77



7
5.97



8
5.67


9
4.88


10
4.34


11
3.53


12
3.34


Year
4.89



That is "not a lot of sun" during during the wetter (?) months of the year (not New Mexico kind of sun anyway).

-Bill

Re: 48v Mppt controller

Basic energy calculations (ignoring losses, discharge rate, etc.):

• 170 AH * 48 volts * 70% discharge = 5,712 Watt*Hours of energy used
• 2,856 WH / 43 miles driven = 133 Watt*Hours per mile driven (like gallons per mile)

And how much array to recharge 43 miles driven in one day:

• 5,712 WH * 1/0.77 panel+controller derating * 1/0.80 lead acid batt eff * 1/5.5 hours of sun per day = 1,686 Watt array minimum

This is the "killer" for solar electric vehicles... You really need a fixed charging station that uses Grid Tied solar+Utility or a stand alone solar array + battery bank (or swappable battery bank) to get the mileage you want and not be burdened with an over sized solar array on the vehicle (and the problems with cross winds, drag, weight, size, etc.).

Did I get all the numbers right? 48 volt battery bank?

What kind of batteries. And what is the vehicle (heavier like a golf cart/light weight car or light like a bike/trike)?

-Bill