Solar powered golf cart

Hi, I just joined the group.

I'm building a solar powered golf cart using a 36v (6 6v batteries in series) ezgo electric golf cart.

I'm replacing the roof with a single 30 volt 300 watt solar panel (2 panels is not an option).

My problem is the voltage of the panel (30v) is lower than the voltage of the battery bank (36v). Most mppt chargers as far as I know can only step down voltage and not up. I'm thinking of one of the two solutions below:

1) use a step up transformer between the pv panel and mppt charge controller.

2) use a 12v mppt charge controller and connect it a 3 parallel strings of 2 6v batteries within the 6 6v string that powers the golf cart motor.

Does anyone have any thoughts on this?

 

Transformers don't work with DC voltage.

Your best bet is to find a charge controller for 36v. The only problem is 36v is super common for golf carts and forklifts but is the least common voltage for charge controllers and inverters.

I have never heard of anyone successfully connecting three different 12v chargers controllers in serries to 3 seperate 12v batteries and having it work.

There is a small market of 36v stuff for golf carts, but not as much selection or as high tech as the 12, 24 and 48v stuff.

Your solar panel sounds like a grid tie panel which isn't particularly useful in 12, 24 or 36 volt systems.
You are probably going to have to get a different solar panel because I can't find a real mppt 36 volt solar charge controller.

Mppt charge controllers can step up voltage if it's a real mppt charge controller. If you have an mppt charge controller that won't step up voltage then you probably have a Chinese made piece of junk that's just a pwm controller that they labeled as mppt so they can sell it for a few more $.

 

Thanks yard dart!

Oil pan: I guess I meant boost converter rather than step up transformer. I was under the impression that neither mppt nor pwm controllers can step up voltage. Ill do more research. Thank you for your response!

 

A quick Google search brings up a myriad of 36 v mppt controllers, most specifically for golf carts...and some state they will up convert.

Btw, do not connect batteries in parallel and in series simultaneously...its called a dead short!

 

Welcome to the Monkey tree!

 

Hi techsar. I have a victron 150/35 which can be set to 36 volts. I must be doing something wrong. Ill do more research. Thanks!!

 

PV voltage must exceed Vbat + 5V for the controller to start...according to victronenergy
https://www.victronenergy.com/uploa...lueSolar-charge-controller-MPPT-150-35-EN.pdf

See note 1b

 

Hmm... I see. Does anyone know of a good mppt for this application?

 

I'm not going to be of much help on that, I'm afraid. I've not had need to go down the 36v road...but it would seem a 48 to 60v (nominal) panel would allow you to utilize the controller you already have.

 

Welcome!!!

 

Welcome!! I'm feeling like I read something about this on offgridham. Off Grid Ham - Keeping amateur radio on when the grid is gone I can't get into it just now, but I'll see if I can find more tomorrow.

 

I have genasun mppt lithium charger controller that will start charging a 13v lithium battery with as little as 8 volts and I tested it.
I tested the panels when the sun was just starting to come up the panels were making 9 volts an amps were starting to flow to the batteries at 13.2v.

 

I think you are going to be disappointed on how much that single panel an produce.
In the long run I recommend several panels on a fixed location with a significant battery bank being fed and use the battery charger off an inverter from that bank what ever the voltage is . a 12 volt battery can still drive a 110 volt inverter .
If the load requires 20 amps and your panel can only provide 4 amps you have a problem.
Secondly one should not rely on nomenclature on equipment ,
Have trusted meters to prove what you getting /using/demanding . Many ratings are established on optimum conditions in which case they do not exist in real life.
I have a switch panel that handles every single aspect of the system , so I can isolate and test every single component .

 

That's true.
A panel laying flat is only going to peak at around half it's rated wattage.
Been there, done that.

 

Thanks all for your responses. I think because the golf cart will be driven only 15 minutes or so around the property per day a single 300 watt panel with 6 batteries will be adequate. Currently, the panel is laying flat and I'm producing 1.5Kw per day. Winter will probably require supplemental power however.

 

I think I may go with a Genasun GV-Boost 8 Amp 36 Volt MPPT Solar Boost Charge Controller. Looks to be just what I need.

 

1.5kw per day with a flat 300w panel?
Where are you at?

 

Tucson, AZ