Need help with my fathers golf cart setup

johanns · March 2018

Hi,
First off I know very little about solar panels so please bear with me as I try to help my father with his golf car configuration.
He has a single Solar Frontier SF170-S panel that is attached to the roof.

	SF170-S
Maximum power	170 W
Module efficiency	13.80%
Open circuit voltage	112.0 V
Short circuit current	2.20 A
Voltage at maximum power	87.5 V
Current at maximum power	1.95 A

He also has a 36V battery bank (6x6V)

We are trying to figure out what solar controller is needed for the panel to charge the batteries?
I am not even sure if his solar panel is correct, so any input anyone can provide will be much appreciated.

Thank you!

littleharbor2 · March 2018

You need to find an MPPT charge controller that will charge a 36 volt battery bank.

This panel outputs less than 2 amps at 87.5 volts this should translate to a tad over 3 amps into the 36 volt battery. Bear in mind the solar panel alone will only supplement regular charging. By itself you wouldn't have enough amperage to properly charge the battery, which would result in the batteries getting prematurely sulphated and basically ruined.

The higher end MPPT charge controllers do 36 volts. Most of the cheaper ones only do 12/24 volts The forum's host, Northern Arizona Have a great selection of charge controllers which will do the job.

mike95490 · March 2018

Sadly, you are going to have to spend a lot of money on a high end charge controller, to provide a tiny bit of charge,

In the daytime, you might get an additional 50 or 60 feet of range on the cart, that's how little the solar will contribute.

westbranch · March 2018

here is a link on a solar powered Golf cart, headaches and all but successful in the end.
http://midniteftp.com/forum/index.php?topic=3142.0
and this one about using a MidNite solar KID CC on 36 volt batteries.
http://midniteftp.com/forum/index.php?topic=3941.msg38467#msg38467

johanns · March 2018

thank you, for your responses back.
So if I were to purchase a 36V charge controller, what should be the AMP on the MPPT Solar Charge controller?

What would be the ideal amperage and voltage needed into the 36V battery bank to make it charge properly?

Estragon · March 2018

The charge regime should be done as per battery maker spec. For typical flooded lead acid golf cart type, absorb voltage (set in the charge controller, and temperature compensated) might be around 44v. A 170w panel will likely put out more like 100-120w in real life (suboptimal angle, etc), so the controller might put out something like 2.5a@44v.

Note that the panel appears to be high voltage - low current, with Voc over the limit for some lower end mppt controllers.

At a 2.5a rate of charge, a 50% discharged 225ah bank would take something like 50 hrs (10 days at 5hrs full sun equivalent per day). Realistically, 2.5a is enough to float a full bank, but not to charge a depleted one. To charge properly, you would want 10x or more (25a) rate of charge.

littleharbor2 · March 2018

Your choices are quite limited for a MPPT controller that has a high Voc. limit and does 36 volts. I just looked on the NAWS site here and you will need a 30 amp minimum controller. The Midnite kid is under $300.00 the rest are costlier. I thought the Morningstar 15 amp MPPT controller would work for you but the Max Voc. is too low for your panel. You might think of getting a different panel with lower voltage so you can save money on the charge controller.

BB. · March 2018

For your 36 volt battery and if you use a PWM controller (I believe some of the MorningStar PWM controllers can be programmed to 36 volt charging with a PC and comm interface--not free). The Vmp-array would need to be ~52.5 to 60 volts. That could be 3x ~130 watt @ ~18 volt Vmp panels in series, or 2x ~200+ watt panels in series (Vmp~30 volts). Picking your "optimum" configuration will require you to paper design several options and see what works out best.

atts	Module	Single Module Price	Single Module	Pallet Prices
130	Solartech SPM130P-S-N 12V	$273.00	$2.10	$1.995
130	Solartech SPM130P-WP 24V	$286.00	$2.20	$2.09
140	Solartech SPM140P-S-N 12V	$200.20	$1.43
190	Solarland SLP190S-24	$224.00	$1.179
290	AXITEC 290W all black	$217.50	$0.75
295	AXITEC 295W mono	$191.75	$0.65
295	Hanwha Black Q.Peak 295W	$215.35	$0.73
300	Hanwha Q.Peak 300W	$228.00	$0.76
305	Canadian Solar 305W	$222.65	$0.73
310	Silfab Solar 310 Watt	$272.80	$0.88
325	Panasonic HIT 325 Watt	$310.00	$0.954
330	AXITEC 330W poly	$222.75	$0.675
350	Silfab Solar 350 Watt	$269.50	$0.77
Other solar panels may be available - this is what we normally stock in depth

For MPPT controllers--It is usually better to run higher voltage Vmp arrays--Call it ~70-100 Volts Vmp-array for a typical higher end MPPT charge controller with ~140-150 VDC maximum panel (cold winters/warm summers)--If you have a narrower temperature range (tropical island).

There are many different Wattage and Vmp configurations for panels... The above are pretty common. The ~140 panels tend to be more expensive ($$$/Watt) vs the >200 Watt panels. You have to decide on the price and charging current you would like... ~5% is Fine for weekend/sunny season use. >10% rate of charge is better for daily usage.

You also need to figure out how much energy the golf cart uses per day (Watt*Hours or Amp*Hours @ 36 volts). And the size of the batteries (i.e, 6x 6 volt @ 200 AH golf cart batteries?).

We need to know both the AH of the battery bank (and if flooded cell, AGM, etc.) and energy use per day + the rough location (nearest major city--Hours of sun)--They are two different calculations that both need to be satisfied.

Also, is this intended to be the only charging power (i.e., charge during the day, and drive after charged or charge day 1 and charge on day 2, etc.) or if it is intended to "float the battery bank" during storage/off season (typically 1-2% rate of charge).

-Bill

Photowhit · March 2018

I don't know where you are located, I, personally, would bail on using that panel. It has high VMP, but will be difficult to match with a charge controller. It's possible in many places to find, if you hunt a bit, 60 cell panels for less than $1 a watt. 60 cell panels will normally have a VMP of 27-30 volts I'd find 2 - 60 cell panels and run them in series and use an inexpensive PWM charge controller.

That will handle 36 volts. I helped find this with no idea of it's quality for a fellow on Facebook group, he's using it and it appears to be functioning very well with his 48 volt system.

https://www.amazon.com/Intelligent-Regulator-Controller-Environment-Charging/dp/B015MOC3VM/ref=sr_1_12?ie=UTF8&qid=1520821960&sr=8-12&keywords=36+48+60+charge+controller

It's easy to find inexpensive panels around 60 cents a watt, but shipping get's ugly! Look locally on craigslist and through facebook market place, letgo phone app. If you give your general location. I'd be glad to hunt a bit for you.

Here is an example, near to me but still 110 miles away. a couple of these at $120 for 235 watts each would cost $240 plus the controller for $50 and for about the price of a Midnite Kid charge controller + gas, you could have a realistic 6 amp charging 36 volts in full sun.

Trina 235 watt
https://columbiamo.craigslist.org/mat/d/new-in-box-trina-235-watt/6482747166.html

mryimmers · March 2018

Get him a proper battery charger and be done with it, haha!!

Need help with my fathers golf cart setup

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