Solar Golf Cart on a Budget - a Self Charging Battery Bank on Wheels

Hows about a self powered neighborhood cruiser that doubles as a self recharging mobile battery bank? That's what we are building here!

Living in South Florida, tropical storms and power outages are par for the course. Sure, you can have a big generator and worry about feeding it or you can opt for more creative ways to make do until power is returned. I love tinkering with solar power so this project was a melding of many different interests. Repurposing things, solar power, tinkering, off grid, and emergency preparedness rolled into one package that I can actually enjoy year round.

Folks sometimes forget the lowly golf cart lends itself well to solar charging and doubles as a sizable battery bank when the power is out. Sure, you can spend thousands hopping up a golf cart but you can have fun for much less and still build something cool.

Supplies

What you'll need...

A serviceable golf cart.

A source for used or blemished solar panels.

A diverse hardware (nuts, bolts, cabling, etc) junk pile.

A source for unwanted/scrapped large UPS gear.

Basic mechanics tools, a multi-meter, and the knowledge to use them.

Some good social skills for tactical begging/bartering.

An MPPT solar controller.

A source for lead acid batteries.

Step 1: Find an Unloved Golf Cart

Golf carts seem to have become a "thing" in neighborhoods across the country. They used to be limited to large properties and golf courses but that's no longer the case. Folks are hopping them up with big tires, sound systems, fast motors, etc. This has of course driven prices way up for nicer looking carts but one can still find cheap ugly ducklings if they search enough.

The big killer for golf carts is bad batteries. Batteries are pricey and the need to replace a pack every few years results in an older cart being put out to pasture and neglected. I picked up the red cart in the picture (pre modifications) for $250 with no batteries. That even included delivery. These deals can be found.

What brand cart to buy? In my opinion when buying an old cart, don't bother with anything but a Club Car. Why? Club Car has been using an aluminum chassis for a very, very long time. Aluminum frames last much longer and Club Car builds a premium quality product. I own a 1973 and 1985 Club Car. Both frames are holding up well.

Lead acid batteries leak and bubble when mishandled or overcharged. Battery acid eats the steel frames in golf carts. The black pile-o-cart in the first pic was an EZ-GO I bought for parts due to frame rot. It was too rusted to save so it became a parts donor for a spare motor and a few other bits. Pro tip, golf carts can be sawed up with a reciprocating saw to make the discarded frames easier to load on a scrap collectors truck!

If you opt for a brand other than Club Car, carefully inspect the frame rails around the battery compartment for rust. That's were they fail first. The frame can collapse and the cart will fold right in the center. Most anything else that ails an old cart can be fixed.

Facebook Marketplace, OfferUp, and Craigslist are good places to look for deals on old carts. Another good way to find them is ask around at places that use them for maintenance or security staff. Once the batteries die, they get pushed aside and neglected.

Step 2: Batteries - No Juice, No Go

Your two biggest expenses will be the cart itself and the batteries. Proper lead acid golf cart batteries are deep cycle and typically come in 6 or 8 volt varieties. they can range from aprox $80-170 per battery. You'll need whatever quantity it is to come up with your cart's operating voltage. Older carts tend to be 36v and more modern ones 48v or higher. If in doubt, the plate on the motor should reveal what the operating voltage is.

What batteries to get if you can't/don't want to spend big money for proper golf cart batteries? Car batteries are terrible for golf cart duty. Car batteries are designed for lots of current in a short burst. RV or marine deep cycle batteries are not exactly proper but will work albeit with a more limited range. That's what I'm running in my cart and it's working out fine. My choice was based on a good deal I got for some 1 year old RV batteries.

I'm using Exide marine/RV batteries. They are working well for me because my panel is producing enough current to defer some load off the battery bank while in motion and the batteries are always kept charged as long as the cart is parked in the sun.

If you're a hard core tinkerer, folks have been repurposing Nissan Leaf lithium batteries with amazing results but that's way beyond the scope of this instructable as it requires quite a bit of specialized skills.

Golf carts can pull a substantial amount of current when accelerating or going up an incline. This is no place for drill packs or other small batteries. Please make sure all your connections are clean and tight. Loose or corroded connections could result in overheating and melting of battery cables or terminals.

Unlike modern car batteries that are designed to be maintenance free, golf cart batteries must be serviced. The water level must be checked periodically be removing the vent caps and looking inside. It should be about 1/4" above the plates. If they look like they need water, use ONLY distilled water. Anything else can ruin a perfectly good battery.

"What about rebuilt golf cart batteries?" If the rebuilder is reputable, it may be worth looking into as you can save a bit of money. Rebuilding batteries typically involves opening the case, cleaning out accumulated debris generated by the plates, sealing the case back up, and refilling with proper mix of water and acid.

I'm sure some of you are saying "I've got a buddy at a scrap yard that can get me car batteries". Car batteries should be your last resort. They are not intended for high amperage consistent draw. They will not put up with the loads a golf cart motor can present when going up inclines or off-road.

Whatever you choose, make sure your batteries are matched in capacity and approximate age. Battery capacity diminishes with age.

WORD OF CAUTION - There's an incredible amount of energy stored in a fully charged golf cart battery pack. Be very careful with tools and cabling.

Step 3: Battery Cabling

The cabling on your donor cart may be present, it may not. If it is, check it for burns, corrosion, etc. It needs to be heavy gauge, typically 4 or 6 gauge. Replacement cable sets can be found online for just about any cart but copper is pricey. Be leery of unusually cheap cable sets. There's something out there called CCA. It's Copper Clad Aluminum. It's aluminum wire with a layer of copper on the outside. My personal take on this stuff is stay away from it.

Want a great source for free cabling with connectors already on it? Talk to I.T. folks and inquire about any large (enterprise grade) UPS systems that may be getting scrapped. The cabling used in those lends itself well to repurposing for golf carts. That's what I used (the red cables between batteries in the pic). The connectors needed a little drilling to enlarge the eyelets but it worked out fine. Thank you APC!

"How do I wire this thing up?"

Once you know what brand and model cart you have, there's plenty of golf cart websites out there that host wiring diagram collections. They are not overly complicated. Batteries, direction control (flips polarity to motor on older carts), a speed control, and a motor.

"What about adding a high amp accessory connector for an inverter or such?"

All carts have a charge port that can be repurposed to pull power from but they aren't really meant for high amperage. I would suggest getting a set of connectors like what tow truckers install on their trucks for plugging in jumper cables so they dont have to open the hood when giving someone a jump. Remember to use an inverter that is rated for same voltage as your cart. The cart doesn't run on 12v.

What about cabling for lights, sound system, etc? I used stranded 14ga-16ga THHN house wiring. It's easy to find and highly resistant to abrasion. You can probably score enough for free from anyone that does residential or commercial electrical work. The longest bit in my cart is maybe 10' so scraps work out well.

Step 4: Speed Control on Old Carts - How It Works

Unless you lucked out and got something fairly modern with a fully electronic speed control, chances are you're going to see something like what's in the picture.

For decades the way speed was controlled on golf carts was to use relays and giant resistors made up of coils of heavy gauge wire. As you pushed the GO pedal (accelerator), switches activated the different relays which routed current through the appropriate resistors. This resulted in 2 or 3 speeds. It was a GO, GO faster kind of thing. It wasn't a smooth transition. Each step up resulted in a slight lurch of speed. Think of it like driving a stick shift car with the engine stuck at a certain RPM.

All the parts to fix these old controls are available online. If you need to replace any of the relays, they must be the same voltage as the cart's motor. The resistor coils can be pricey but some experimenters have figured out that using heavy gauge solid steel or aluminum wire of the same size and number of turns can work out fine. Those coils get hot, keep stuff away from them in operation.

Ideally, it makes most sense if you can carefully take all the connections apart, wire brush all the corrosion off mating electrical connections, and put it back together. As you can see by mine, it has that "If you mess with me I'll break" look. Mine is working just fine as is so I'm leaving it alone till it fails. So far, I've put a good 40+ miles on the cart with no issues.

WORD OF CAUTION - Don't work on any wiring with batteries connected. There's plenty of opportunity for sparks and bad times. Don't risk it. Disconnect both positive and negative leads from bank while working on electrical system. Ideally, throw a (dry) floor mat or something similar over the battery bank to shield connections from dropped tools.

What about electronic speed controls? Considering this is a low buck thing, chances are you're going to end up with an old resistor cart. If you luck out and got an electronic one, it will use a potentiometer at the GO pedal to tell an electronic box how to vary the output current to the motor. These are more efficient and retrofits or DIY kits can be found online. I bought an absolutely trashed cart just to rip out the electronic speed control for a future project. Deals can be found!

Is it worth retrofitting an old cart with a modern electronic speed control? Most definitely as it will get you more run time but it's not necessary. The cart in this instructable is running fine on it's old system and my range is more than adequate for my needs. I'm not messing with it till it breaks.

"What about testing all this?"

For testing purposes, you can round up 3 or 4 car batteries that hold charge and temporarily hook them up. You'll need the cart's wiring diagram and someone who thoroughly understands wiring so they wire things up using (3) 12v batteries instead of (6) 6v batteries like the cart normally takes if it's a 36v system. The same adjustment would apply to a 48v cart, when using 12v batteries on a 48v system, it's (4) batteries.

Jack up back wheels of cart so they are off the ground, put cart in forward, slowly push on the go pedal. The motor should start humming and wheels spinning. You'll hear the clicking of the relays coincide with increases in speed. If you get no joy, find the schematic for your cart and get a meter. You don't need an engineering degree to diagnose these, just some basic electrical knowledge and a decent multimeter.

Aside from dead batteries, relays and speed resistors are common sources of trouble. The motors themselves are fairly sturdy.

Step 5: Tires - It's Got to Roll, Right?

With all the attention golf carts are getting, customization has become quite a "thing". One of the most popular mods is big tires and a lift kit. This means there's a glutton of stock tires and rims out there. I got a set of 4 matching tires and hubcaps free (pic 1) for the asking. The downside? They have dry rot but when you're moving along at an earth shattering 12MPH or so, who cares?!?

Dry rot (pic 2) presents itself as cracks in the rubber. Is it bad? Yes. It weakens the tire and it can fail. On something that moves fast like a motorcycle or car, a blowout can be devastating. On a golf cart, not so much as long as your not driving the thing like a sports car. The tire may just go flat one day or go out with a PFFFFFF. It's a risk I'm okay with. I'll laugh it off and put on another freebie.

If you're not able to get a set of 4 matched tires, make sure the two front tires are same size and two back tires are same size. Golf carts have no ABS so they don't care if front/back are a different size. Mismatched sizes left/right however can cause the cart to pull to one side and/or cause accelerated wear on the gears inside the differential.

"Is speed tied to tire size?"

Yes it is. A bigger diameter tire may give you more top speed but you'll sacrifice acceleration or hill climbing power. It will put more load on the batteries and motor. The engineers designed the thing to roll at an acceptable speed with acceptable range while keeping motor load as low as possible. Putting bigger tires on it will upset that balance at the expense of range and overheating of the motor.

"What about rolling resistance?"

Traditional golf cart tires are wide so they roll easier over grass. If you won't be driving it much on grass, There are small trailer tires like those used of jetski trailers that may fit a golf cart and have less rolling resistance on hard surfaces. On any tire, inflation is important. Since you are on batteries, keep those tires pumped up to manufacturer specs. If you're rolling on old tires like I am, it may be wise to drop 5psi or so below manufacturers spec to lessen the chance of a blowout on a dry rotted tire.

Step 6: Rot, Cracks, and Other Things

Older carts may have been subject to abuse, wrecks, etc. You may have some mending to do. Check the seat platform for rot (pic 1). It's not uncommon and an easy fix. Untack the old seat material, use the old wood as a template, cut out a new piece out of plywood, transfer all the parts, foam, and cover to the new platform. An industrial staple gun should do the trick for tacking that seat material back down.

Any old lighting (pic 2) on the cart will probably be incandescent. Ditch it all. It's very inefficient and you're on battery. Go LED like I did (pics 3 and 4). The headlight I'm using is a Chinese "offroad" light and the taillights are actually LED trailer marker lights. Some carts have actual brake light switches, some don't. If you're going to ride at night, at least get a headlight and red rear lights for visibility to motorist. Check all your lighting wiring if you're going to reuse. I ripped out all the old stuff and just ran new wire and a new switch.

What voltage? Follow the light wiring around and see how it's connected to the battery bank. There's a good chance they used the ground and positive from the last battery(ies) in the chain to run the lighting at 12v. Yes, this presents an uneven load to the bank but since they are LED, it's not a deal breaker. Just don't go crazy adding lights to the cart. Keep it simple and low drain.

Moving on to body damage. Body cracks can be patched with Bondo or fiberglass sheet and resin if they bug you. The body on traditional golf carts is just a shell on a metal frame. If ugly don't bother you, ride on and give people a good story about how a sasquatch attacked your cart one day. Strategic bumper sticker usage can work as well.

Step 7: Getting Your Solar On

Let's talk about solar panels!

So obviously you'll need a panel or more. Forget buying new as a panel this size can easily be a few hundred dollars. I went to a local solar panel dealer and asked about used panels. They had a large inventory of blemished and used panels on hand. I walked out with a huge 72v panel for $60! Why so cheap? The frame was bent so I had a little work ahead of me. I had to lay the panel on a table and carefully remove its frame, straighten the bends, and reassemble it. I used RTV to bond the frame back to the glass along with the original corner fasteners. I also added a center support to prevent the same issue from reoccurring. Pics are of top and underside of panel once mounted.

If you don't have a solar panel dealer near you or they don't carry used stuff, check the usual suspects online like Craigslist and OfferUp. I've seen good deals on panels pop up there often. Folks doing solar on their homes sometimes end up with extra panels that didn't get installed for some reason or another.

What you're looking for..

You'll want a glass face, aluminum frame, silicon panel that puts out about 20v or higher than what your cart's battery bank needs. For example, you have a 36v cart, look for a 56v or higher panel. Why higher? So the charge controller has a good margin to work with. Remember, lead acid batteries need to see a higher voltage on charge than what they normally output. A 36v pack is somewhere at 44-45v when freshly charged. The higher voltage also gives you some margin on cloudy days. Wattage wise you want to be in the 150-200w range. This will be a large panel. Mine was 81"x44".

Avoid amorphous panels at all cost. These are the ones that have a brownish look instead of blue like silicon. Amorphous panels put out roughly 1/3 the power of same size silicon and have a shorter lifespan. These are found at places like Harbor Freight. The results will be disappointing in this application.

Don't get hung up on mono Vs poly crystal silicon. The difference in output is not critical here.

"Won't it break up there?"

Solar panels are much tougher than you may think. As long as the frame is intact and well supported, it can put up with a bit of abuse. If you look at the second pic you'll see a silver aluminum bar across the center of my panel. I added that to strengthen the frame as this $60 panel was priced as such due to a bent frame caused by a weak design.

Next, how to mount it!

Step 8: Ideas on Mounting Your Solar Panel and Controller

So this step is totally a case of "what worked for me". There's plenty of pics to illustrate my solution.

My cart came with a plastic roof that I removed but I kept the aluminum uprights to mount my panel on. Could you mount the panel onto the plastic roof? I suppose so but why have the extra weight on an already flimsy support structure?

I used scrap aluminum 19" rack rails that I painted with Rust-O-Leum as cross bars to sit the panel onto. I cut them the width of the panel using a Sawzall and sanded the ends with an angle grinder to remove sharp edges. A little paint and it worked out. Added bonus is now I have a really convenient place to mount gadgets overhead where they will be well protected from rain. Attachment was done with whatever hardware I could scrounge.

In my case, it became apparent that at some point my cart was either rolled or somebody climbed on the roof. The supports weren't even. The plastic roof did a great job of hiding the difference in support heights. I ended up just shimming the panel with washers to get it even. You don't want the panel to be twisted. Is it a clunky fix? Yes. Did it accomplish what I needed? Yes. Why didn't I straighten it? Sometimes aluminum doesn't take well to be bent one way and then another.

My experience has been that I need to check the mounting hardware every so often as it works itself loose from road vibration. In the future I'll be swapping over to locknuts to put an end to that issue.

Step 9: Charge Controllers - What They Do

In the pics, you see the charge controller I used. It's mounted under the solar panel onto the repurposed rack rail. It's not rainproof so I mounted it high up and under the panel. It seems to work out fine there for now. I may end up making a cover for it in the future if rain becomes a concern but so far it remains dry in the worst of South Florida rain. The good thing about it being there is all my charge data is easy to see.

So why do you need a charge controller? If you hooked the panel straight to the battery it will eventually overcharge and damage the battery. The charge controller monitors battery voltage and tapers down the charge at a predetermined voltage.

Modern solar charge controllers come in two flavors, PWM and MPPT. PWM is a more basic controller and it just cares about reaching a set battery voltage and cutting off. An MPPT controller actually adjust voltage and amperage to find the best combination to make the most use of the solar panel's output. This tech gets you the most bang for your buck from your panel. It is a little pricier but not by much when compared to other Chinese charge controllers. MPPT controllers can also make use of a much wider panel voltage. PWM controllers require closer matching of panel and battery voltages.

Budget MPPT units seem to lack the boost function other pricier units have. What does that mean? On the better MPPT units, you can use panels that put out less voltage than your battery bank and the regulator will boost it at the expense of some amperage (nothing is free). The cheaper MPPT units require panels that have a higher voltage than the battery bank, just like the PWM regulators do. Go with a decent MPPT regulator.

A word on regulator brands and prices...

My experience with Chinese off brand regulators has been good. I read reviews and comments before making my purchase and even then, it wasn't expensive considering a comparable unit from one of the big names in solar would be 4 times as much. I have had good experiences but not everyone has the same feelings.

I've noticed the Chinese regulators lack some features and are really particular about what order things are wired in. READ THE MANUAL first before wiring it up.

In most cases the panel would feed the regulator, the regulator goes to the battery, and the load (whatever is consuming the electricity) connects to the regulator. In this case, that's not what's happening. There's no way the internal switching of the regulator could handle the golf cart motor. So in our case, we are wiring panel to regulator, regulator to battery.

A cool hack is find an LED "on" lamp that runs on same voltage as your cart and wire it to LOAD connection on regulator. Set regulator to 24hr mode per instructions. This will give you a quick and dirty way to determine if battery is run down. Light is on, you have some charge, light is off, battery needs charging. The LED pulls minimal current and you'll be charging as soon as sun comes up.

The regulator I used was from ebay but I have seen the same units on Amazon. It has worked out perfect. It gives me bank voltage along with panel voltage, amperage, and wattage. A quick glance while riding and I know exactly what my power situation is.

Step 10: Tunes? You Gotta Have Tunes Right?

I had to have at least one hop up and that was a cranking sound system! I went with a high power class D Bluetooth capable amp and some high quality 6x9's. The Speakers are mounted on the box area under the seat (pic 1) and the amp is up on the rail over the passenger area.

I could have used those "boat torpedos" everyone is using but gawd I hate the way those things look. I wanted loud and low key. The area under the seat is where the batteries live so you have limited depth between the fiberglass shell and the batteries. I found some nice spacers that gave me enough room to use standard 6x9's without fear of hitting the battery cases. I cut the holes out using a cordless router with a narrow bit set to just enough depth to cut without fear of hitting the batteries.

I went with MB Quart poly cone speakers with butyl surround. They are rainproof without the marine price tag. By using the spacers, I still have about 1/2" clearance between the battery cases and the magnet structures on the speakers. By being mounted in that big box, I get some decent full range sound.

For amplification I used a Chinese TPA3255 class D Bluetooth amp that can accept up to 48v input. That little box can belt out up to 300wpc at 2ohm but is happier at about 150wpc with better distortion specs. It's more than enough to slam those 6x9's to death. On a 36v cart, max charge voltage is 44v so the amp is perfect for my needs. If you have a 48v cart you'll have to use a buck/boost board of at least 12A to keep this amp happy. I haven't seen any of these class D amps that can put up with the 56v or so a 48v bank can present when fully charged.

Can you use a car amp? Sure but then you'll need to tap into the same batteries as your lighting and the load from an audio amp can seriously unbalance your battery bank by discharging part of it unevenly.

How did I mount the amp? I cleaned the bottom of the amp and mounting area with alcohol, then applied RTV and zip tied it in place for 24hrs. Once the RTV cured, I removed the zip ties. It's stuck on there firmly without unsightly zip ties or crude hardware. Yes, it's upside down but you wouldn't know unless you got up close to look at it.

Future mod.. a subwoofer! In the last pic there's a board I found at PartsExpress that crosses the full range speakers over at 130hz and sends everything below that to a sub. I'll be adding that in with a dual voice coil sub in the near future. Golf carts have cavernous spaces under the body so they lend themselves well to a hidden sub. Rock on!

Step 11: Learn to Drive It and Enjoy It! Don't Just Let It Sit..

If you succeeded, you have built yourself the greenest of electric vehicles, one that requires no commercial power to charge. The added bonus is you have a big battery bank on wheels that self charges and can be tapped into for other purposes.

It will ride just like any other golf cart except there's no more "I forgot to charge it" nonsense. If everything worked out fine, on a sunny day you should be able to see vastly increased range thanks to the panel. My charge time after an extended ride cruising the neighborhood has been about the same as charging off the old Lester plug in charger. The cool thing is no more dealing with the charger. I have had no need to charge it off mains ever since I did this mod and I do cruise the neighborhood with it a few times a week.

Theoretically, if connected to an inverter to run a fan and some lights overnight you should get similar results. Whatever you used up overnight should replenish with one sunny day. Keep in mind that no sun = no charge. On cloudy days you're just not going to get much charge but at least the batteries will never go flat from neglect.

Now don't forget, no sunlight = no charge. Keep that panel clean. An accumulation of dust on the panel will adversely affect it's charging ability even if you have good strong sunlight.

If you've never driven a golf cart or other battery vehicle keeps these points in mind...

Gradually build up speed. Gunning it is hard on the motor and the batteries. Longest run time is achieved by cruising along. Accelerating from a roll is less demanding on the batteries than from a standstill. Riding on grass will eat more battery than riding on a hard surface. Tire pressure is critical to getting maximum run time. Soft tires ride nice but eat battery resources.

Since this is a solar vehicle, you will notice a little more pep when riding in full sunlight when the sun is primarily overhead. Likewise, don't forget to park where the solar panel has a clear view of the sun. No sun, no joy.

My experience so far...

I've put well over 40 miles on it since I did this mod. It's an old cart with an inefficient speed control, worn out suspension, and a DC motor. I easily get 10+ miles range with two big adults, playing the stereo, and riding on pavement. I have yet to get stranded with a dead battery. I do watch the battery voltage, stay in the sun, and drive with an EV mentality.

It's a fun mode of neighborhood transportation and an emergency battery bank on wheels!