golf cart roof charger

[rcpaisley]

I am building a golf cart roof around a single 260W solar panel.
The cart has a 48v battery setup. I am trying to figure out the best way to mate the panel to the batteries.
Most panels have too low of a voltage to simple connect through a typical MPPT controller.
I have not purchased a panel yet. If I could find a panel with around a 100v output this would be easy.
I have found "Boost MPPT Controllers" that can step up the voltage internally to feed the batteries, but they are quite expensive.

Any one have an easy answer (or reasonable cost answer) for this project?

Thanks,
Robert

[inetdog]

I am building a golf cart roof around a single 260W solar panel.
The cart has a 48v battery setup. I am trying to figure out the best way to mate the panel to the batteries.
Most panels have too low of a voltage to simple connect through a typical MPPT controller.
I have not purchased a panel yet. If I could find a panel with around a 100v output this would be easy.
I have found "Boost MPPT Controllers" that can step up the voltage internally to feed the batteries, but they are quite expensive.

Any one have an easy answer (or reasonable cost answer) for this project?

Thanks,
Robert

I am not aware of any simple and inexpensive way to do what you want. The few solar roofed golf carts that I have seen (for maintenance staff on a university campus, and probably purchased more for PR value than practicality) have used thin film panels in a high enough voltage configuration to use a conventional MPPT CC.

[rcpaisley]

Boost controller

I found the Genasun 48v/8a Boost Controller on Ebay for $239.
That sounds like it would do the job.

The golf cart sits in the sun 90% of the time, and gets driven for a few minutes here and there (mainly for restroom runs).
My hope is that it rarely needs a plug in after adding the panel.

Robert

Here is the controller manufacturer page:

http://genasun.com/products-store/mppt-solar-charge-controllers/golf-cart-solar-charge-boost-controllers/

[Sunking]

I have built a few solar roofs for friends using a EZ-GO RXV cart that uses 48 volt battery. First thing is you are going about this all wrong with the one panel concept. As you have discovered there is no 60 Vmp panels unless you go with thin film. Think 2 or 3 panels in series.

You do not have to custom design anything as there are companies who make solar panel roof replacements for any make and model golf cart. What I will tell you everyone I have done one for or know has been very disappointed. Most of them actually use them to play golf everyday or as a NEV or both. All they really are is a range extender and a poor one at that. The carts still need recharged every night with charger after use. So don't go getting rid of you cart charger as you will still need to use it. The problem is simple physics as a golf cart efficiency is around 350 wh/mile, and at best on a full sunny day all the panel can do is give you about an extra mile out of the 15 to 20 miles the battery can deliver on a full charge.

[SunEagle]

I have built a few solar roofs for friends using a EZ-GO RXV cart that uses 48 volt battery. First thing is you are going about this all wrong with the one panel concept. As you have discovered there is no 60 Vmp panels unless you go with thin film. Think 2 or 3 panels in series.

You do not have to custom design anything as there are companies who make solar panel roof replacements for any make and model golf cart. What I will tell you everyone I have done one for or know has been very disappointed. Most of them actually use them to play golf everyday or as a NEV or both. All they really are is a range extender and a poor one at that. The carts still need recharged every night with charger after use. So don't go getting rid of you cart charger as you will still need to use it. The problem is simple physics as a golf cart efficiency is around 350 wh/mile, and at best on a full sunny day all the panel can do is give you about an extra mile out of the 15 to 20 miles the battery can deliver on a full charge.

At my old job they purchased a golf cart with a solar roof. It was supposed to provide all of the power needed to keep the batteries charged. Big disappointment. The panel barely provided a trickle charge when it was stopped under full sunlight. They had to charge the batteries at night the conventional way with a standard charger. It seemed to be a nice idea but did not pan out as expected.

[rcpaisley]

charging efficiency

At my old job they purchased a golf cart with a solar roof. It was supposed to provide all of the power needed to keep the batteries charged. Big disappointment. The panel barely provided a trickle charge when it was stopped under full sunlight. They had to charge the batteries at night the conventional way with a standard charger. It seemed to be a nice idea but did not pan out as expected.

Yes, that is why I am going to build a golf cart roof around a 260W panel. That's a lot of power.
I have one on my motorhome and never have to run the generator anymore. I sometimes see 18A coming off the panel (at 12v).
This would correlate to 4.5A at 48 volts which doesn't sound like a lot of charging power. However if the cart sits idle 90% of the time,
it should certainly stretch out the charge duration. I guess I will find out!


Robert

[Sunking]

Not going to work with one panel.

[inetdog]

Not going to work with one panel.

Will work with one panel if he uses the specific boost MPPT CC he posted a link to. However I cannot give any evaluation or recommendation with respect to particular CC since it is new to me.

He will need to watch out for the limitation that it will only work reliably if the panel Voc never goes above the lowest voltage of a discharged battery bank.
That could be a problem for some grid tie panels, and even worse if he was using a 36 volt battery bank, which the CC also supports.

The cost of a 260w 12 volt battery panel will be higher than the cost of a 260w grid tie panel, but at least it will be within the operating parameters of that CC.

[russ]

Yes, that is why I am going to build a golf cart roof around a 260W panel. That's a lot of power.

When oriented correctly and in full sun you may get 50% of the 260 - normally you will probably get a small fraction of that.

I think you have no idea what the panel on your RV actually produces - you are just assuming while the RV alternator does the charging.

[Sunking]

The cost of a 260w 12 volt battery panel will be higher than the cost of a 260w grid tie panel, but at least it will be within the operating parameters of that CC.

He asked for the easiest best cost effective solution.

Well I have done a few and the easiest best solution is to use 2 or 3 grid tied panels wired in series with a MPPT controller. As you know GT panels are half the cost of battery panels. To take it one step further he does not need to reinvent the wheel here as there are already golf cart roofs with the 3 panels already fabricated. Problem is he does not want to hear any other solutions or experience. It is his way or the highway. So good luck. Just keep your regular cart charger because you are going to need it.

[Mike90250]

Well I have done a few and the easiest best solution is to use 2 or 3 grid tied panels wired in series with a MPPT controller. As you know GT panels are half the cost of battery panels. To take it one step further he does not need to reinvent the wheel here as there are already golf cart roofs with the 3 panels already fabricated.

That's about what I was going to say, build a roof frame to hold 2 or 3 GT panels in the 200w range, and
a Rogue or Kid MPPT controller. But for the expense, you will only get bragging rights for 1 extra mile a day. If it's only used for beer runs (load & unload) maybe it will keep the charge up, but it's got to be parked in full sun all day. Maybe some tilt (20deg) to the roof to improve the sun angle.

[rcpaisley]

panels

Will work with one panel if he uses the specific boost MPPT CC he posted a link to. However I cannot give any evaluation or recommendation with respect to particular CC since it is new to me.

He will need to watch out for the limitation that it will only work reliably if the panel Voc never goes above the lowest voltage of a discharged battery bank.
That could be a problem for some grid tie panels, and even worse if he was using a 36 volt battery bank, which the CC also supports.

The cost of a 260w 12 volt battery panel will be higher than the cost of a 260w grid tie panel, but at least it will be within the operating parameters of that CC.

Thanks Inetdog for actually reading my proposal. I would love to use more panels, but there is only so much room available above the cart. I do in fact understand the panel output on my RV as it is fully instrumented. My RV also sits for several days with only the single 260W panel providing input to the batts - it works great!

I am also an EE who understands the ramifications (and limitations) of the project. I also live in SoCal with lots of sun available. 350wH per day on a 260 watt panel is not a stretch. And if that gives me a mile of driving, I am pretty close to not using the charger often if at all.
The cart will also be instrumented, so I will know exactly how things perform.

I will happily report the results of my project (or failed project, to those who will read it that way) after the parts are bolted together.

Robert

[rcpaisley]

step up charge controller

Here is another step up (boost) charge controller:

http://www.solarconverters.com/index.php/products/81-power-tracker-chargers/cv-charge-controllers/111-cv-24-48-6pv

$219 from solarsellers.com
Robert

[thastinger]

What is the appeal of an electric golfcart? My FIL has a gas one we use to putt around the property and it uses very, very little fuel. Why would one buy electric over gas considering the 1K battery replacement every 3 years or so?

[rcpaisley]

electric golf cart

Valid question,
I received a very nice electric cart for almost nothing - family deal.
Doing a little customizing is a bad habit of mine, hence the solar project (and other items).
I just put a new set of 8V batteries in it for a little over $660.
The solar project will add close to another $1000 by the time a new roof is fabricated.
Does it make sense financially - probably not.
If I was out shopping for a cart, a gas engine would certainly be high on the list.

245W panel is arriving today. Materials to fabricate the new roof will arrive this week. I'll have to choose one of the step-up charge controllers.
Ebay LCD ammeter and voltmeter ordered.
A little welding and wiring and viola.

Robert