Solar Electric UTV (Polaris sucks, Bad Boy Buggy sucks, Club Car wins)

Step 1 completed:  Acquired a used late-80s EZGO 36V golf cart with charger locally for a decent price.  It uses 6 X 6V batteries wired in series.  As per the weblink in the 8/12/2022 entry above, I'm hoping over time to mount a 300W solar panel on the roof and run the power through an appropriate controller into the battery pack.  Now having driven the cart a bit on our terrain, I feel no compulsion to up the power on the unit as the person in the web-link had done.....with our flat property and no 'need for speed', the torque provided by the electric motor is more than sufficient for bucket hauling and moving light loads of wood.

One question I have relates to battery maintenance....as this acquisition is encouraging me to learn more about deep cycle battery feeding and care.  The current batteries in the cart are standard lead-acid deep cycle golf cart batteries.  Although it would be an expensive exchange, I could get into "36V golf cart replacement packs" of lithium batteries, in this case three batteries, each battery (36V/60 Ah) wired in parallel.  Truthfully, my own reason for wanting to do this is to lighten the load, lighten transfer of the batteries for storage in the off-season, and potentially have a more worry-free battery over their life-span.....(??)....yes?....maybe?  Are there additionally any benefits or drawbacks to a lithium vs lead acid battery system when designing a solar charging system around them?  I've read that 6 X 6V systems will out perform 3 X 12V configurations (series wiring) in power and averaged duration before re-charging but don't know how this may relate to the 36V parallel wired batteries now being offered and that I'm considering.

At this point I'm impressed with what the unit can do and how little charge we have used up in short trips around the homestead. Thoughts on the above?  Thanks!.....

Edit:  Looks like the replacement pack in question is actually 3 X 12V series-wired Lithium iron phosphate batteries.  They sell 36V batteries, but the golf cart replacement pack is not sold that way.

I may have a contender for this use.  Taylor Dunn has made electric utility carts for decades, mainly for industrial uses.  I just picked up a B2-48 that was made in 2005.  It already has a solid-state controller.  One downside is there isn't a lot of room between the seat and the steering wheel and foot pedals.  If you are a large-frame person you might have problems.  However, they are considered bulletproof.  The one I got is rated to carry something like 3,000 lbs and tow 12,500 lbs.  That is probably on a level paved surface, but still that is more than I will ever need for work around my homestead.   There are configurations available with a 2nd row of seats and I think they will fold down to a larger flatbed.

It seems like the concept of electric vehicles (EVs) is spilling over into the rural/farm sector at an increasing rate.  Many if not most of the major agricultural equipment brands are offering some sort of electric version of an ATV/UTV at this point and no doubt they have been able to borrow extensively from the decades of technology development in the golf cart sector.  While I'm still interested in solar juicing my current golf cart with a rooftop panel, I'm being seduced by current ads for some of the newer golf cart/UTV offerings, some from traditional manufacturers and some from new start-ups.  Typically these are 48V or higher, but there's a new twist if I'm reading the history correctly:  AC motors instead of DC motors as the power plant of the vehicle.  Although there may be advantages of an AC motor over a DC motor, it appears there's added complications as the DC current from the batteries needs to be converted to AC.  Minimally this would seem to incur a power cost.  Additionally, when I inquired at a local sales outlet about replacing the lead acid batteries with LiFePO4 (48V driving AC motor) they responded that some interface changes would need to be done and would not be something they could do locally.

Have any other tweakers and DIY-ers out there encountered these issues in the farm-based electric vehicle realm?  Is the AC motor the new trend and is it likely to phase out the DC motors of past electric golf carts?  I'm certainly finding that, as an 'ageing homesteader', these vehicles are worthy companions in getting work done.  Thanks!....

So I hope it's not considered a hijack of this thread to continue to post on progress in outfitting an older 36V golf cart (EZ-GO) to supplemental solar charging.  I've decided to stick with lead acid batteries (6 batteries @ 6V/225 Ah) until next year, but went ahead with a local purchase of a used solar panel:  original rating of 327W, ~54 V, and ~ 6 A.  See the link in the  8/12/2022 entry above for some background and this link for specs on the panel:  https://us.sunpower.com/sites/default/files/media-library/data-sheets/ds-e20-series-327-residential-solar-panels.pdf

In the video link from the 8/12/2022 entry above, a charge controller is recommended that, upon inspection of the specs, does not have a setting for LiFePO4 batteries.  Yet it appears that some manufacturers of MPPT charge controllers do in fact sell controllers that can adjust between both lead acid and LiFePO4 types of batteries.  Can anyone here please recommend a charge controller that may fit the bill for my system that I could use now for my lead acid batteries, but also use when I've switched to LiFePO4?  Also, if I connect the output (from the controller) to the leads that originate from the charging plug (grid powered stock cart charger -- 36V/18A), will this cause problems when I want to use the stock charger or will the controller sense this and not allow 'backfeed' of current into the solar charge controller and panel?  

Thanks for any questions, comments and recommendations you can offer!....

John Weiland wrote:In the video link from the 8/12/2022 entry above, a charge controller is recommended that, upon inspection of the specs, does not have a setting for LiFePO4 batteries.  Yet it appears that some manufacturers of MPPT charge controllers do in fact sell controllers that can adjust between both lead acid and LiFePO4 types of batteries.  Can anyone here please recommend a charge controller that may fit the bill for my system that I could use now for my lead acid batteries, but also use when I've switched to LiFePO4?  Also, if I connect the output (from the controller) to the leads that originate from the charging plug (grid powered stock cart charger -- 36V/18A), will this cause problems when I want to use the stock charger or will the controller sense this and not allow 'backfeed' of current into the solar charge controller and panel?

I bought an EPEver that seems robust for the price and does both LA and LFP, but is only 12 or 24V. I'm seeing others at Amazon in that price range or less with decent reviews if you are willing to go that route. It would be nice to find a source better than Amazon for stuff like this...

paul wheaton wrote: ............Overall, I think that if I could do it all over again, I would get:  a standard body club car (not the long body we have now) with seats in the back that fold down to carry stuff.  The straight axle stuff (no fancy suspension) means there are no boots or wimpy axles to deal with.  And because it is something that is built by the thousands, it is designed for heavy use.  The polaris and the bad boy buggies seem to be built as an occasional use novelty.  I do think I would get something that is just two years old instead of 20+ years old.  

Just going back to the OP and adding some follow-up to my project outlined more in this past link:

https://permies.com/t/221392/PV-panel-hook

It's now been several weeks since the install and the system has exceeded my expectations.  Just going over the finances that involved some new, some used additions on the the base EZ-GO golf cart:

Used 1990 EZ-GO 36V Marathon golf cart       $1500.00 USD    (note:  stock configuration....could be lifted and larger wheels added for clearance)
2 "new" (used) 6V 225 Ah lead-acid batteries to replace 2 that were bad     $100.00
New flip-down seat to replace rear stock configuration                                ~$400.00
Used 327 W solar panel purchased locally                                                        $100.00
MPPT solar charge controller, 40 A, 12/24/36/48 V                                          $150.00
Associated wire/charge status meter/multimeter                                          ~$100.00

So this project cost under $2500.00 (wall charger came with the cart) and as noted in Paul's original post, exploits the oddity that golf carts are built with amazing durability given what they are used for.  It's no secret that changes are afoot and city codes are allowing more "street legalized" carts like this on urban roadways, which in turn is producing a new import market for the ~$10-20K range electric UTV.  The durability and user-friendliness of those new vehicles remains to be seen, but in the meantime the usual media outlets for used items typically have a rotating selection of used golf carts anywhere from sub-$1000 to $10K.  I could have avoided the $400.00 flip seat if I had just waited a bit longer and found a cart that already had one installed....the flip seats are pretty common and allow for a small 'truck bed' like platform when needed.  The stock sun canopy was removed and I bolted on angled metal rail (from any hardware store or big box version) to the existing supports in order to mount the PV panel.

The original thinking was that I would just reduce the frequency of charging from our power grid by virtue of the solar panel.  It's been a pleasant surprise that, given our usage of the cart for just shuttling feed buckets, firewood, etc. around the property, I've not needed to plug it in at all.....and typically charges by solar power back to 100% between uses (northern Minnesota USA, .... will see as winter approaches how long this remains the case).  So much nicer than firing up the various gas/diesel vehicles for similar tasks.  As the cart was used and I sense could use some brake/lubrication work, I probably will spring for just hauling it to a local EZ-GO maintenance/dealer for the once-over.  But as a great starter project, it's been fun and useful to boot!

Didn't know if this warranted a new thread or not, but decided to follow my last post in this thread with description of a new "member of the family" :-)

Following on the success of 'solarizing' the EZGO golf cart in the entries above, it was decided that we needed something more robust than our gas Gator for cold weather operation.  In short, we do not have heated storage for our vehicles so they must be able to start and operate below zero F, sometimes down to -30 degrees F.  We opted to stay with lead-acid battery technology since operation and charging of LiFePO4 batteries is still quite temperature dependent.  Even at the sacrifice of power in cold weather, the lead acid batteries will function and recharge in cold weather, providing sufficient power for my wife's animal feeding needs.  The golf cart in previous posts rides a bit too low, is not 4X4, and does not have the same cargo capacity as the Gator had.  So I was able to find a used Polaris Ranger EV (48V) which so far has been great!  We haven't tested it below zero yet....that should happen during the coming week.  But at $6K as a used unit in great shape (275 hours) and fairly new batteries, it seems like a worthy purchase.  (New machines from name brands for electric 4X4s tend to run near $20K or higher, but there are several newer imports for around $12K.) For snow in winter and mud in the spring, the 4X4 likely will aid us much. I've already planned out the solar addition to this cart as I was so pleased with way the EZGO worked out.

There appears to have been no additional posts since my entry from this past spring of a 2012 Polaris Ranger EV.  Although we are still running it on lead acid batteries, the newer offerings in LiFePO4.....in particular those with battery heaters for cold climates.....have me planning to upgrade to that platform probably next year.

In the meantime, I just finished installing a solar charging station for it.  A ~385W solar PV panel was purchased locally for about $150.00.  The Ranger runs on a 48V battery bank, but the output of the panel hovers around 40V.  So I bought a buck-boost controller (20A, 12-24-36-48V capable, range of battery types compatible) and began the install.  Photos attached.  I still need to integrate some 'protection'.....grounding, breakers, etc.... but have a master shutoff between the PV panel and the controller.  In the last photo of the previous entry, you can see a 'dummy' plug where the gas-fill port is located on the petrol Rangers.  I drilled that out with a hole saw and inserted a 3-prong connecting plug (male) that is used for RV connections at camp sites (?.....), the back of which was wired with 10AWG to the battery bank mains.

After connecting all wires to proper locations with solar feed "off", it was pretty seamless plug and play:  A 20A 3-prong (female) extension cord wired into the battery side of the controller was plugged into the Ranger port bringing the controller immediately to life.  Hoping all was well with load recognition by the controller, I threw the switch on the PV panel and all shook hands and started operating perfectly!  A phone app for the controller allows one to monitor solar panel feed and battery state of charge.

My one concern is that it appears on the one hand that the charge profile in the controller gets up to a float voltage of ~56V whereas the Ranger EV literature indicates ~53+V as being fully charged.  I can see on the phone app that at 53V, the controller is still pushing ~5A of power to the batteries....and i'm concerned about letting it go much higher to see if it will enter float mode.  I do not see a place in the app to modify the charge profile to start floating at a lower voltage.....Thoughts on this?  Thanks!

56V on a 48V nominal lead acid battery would be equivalent to 14V to a 12V nominal battery (or two 6V batteries as the case may be). Cars typically put out more than that, so it wouldn't be harmful in the short term to see if it does settle in to a lower float voltage once the amperage output is reduced. A charger has to be at a higher voltage than the battery in order to charge, and if it was still pushing 5A then the battery was taking a charge. My understanding with lead acid is once you start getting below 1/20th of the battery ampacity, that between the design and internal resistance you aren't doing any harm to the battery. With 5A in to 225A it's like filling a bucket not quite one pint per hour.

Another thing I've noticed after a bunch of battery babysitting is the difference between the voltage output at the charger, and the voltage of the battery. This is especially noticeable at higher amperage because the total resistance of the circuit amplifies voltage drop as current draw increases. Plus in the case of lead acid, they have much higher internal resistance than Li-Ion/LiFePo. In extreme cases you can end up with a partially charged battery and the charger stopped because it read the voltage as full, and possibly heat damage around connections because all the energy that didn't make it to the battery turned in to heat. I see lots of people online using thermal imaging cameras to find the causes to issues like these.

If you have a halfway decent meter handy to check the voltage, you can try measuring the voltage directly at the charger terminals while it is giving close to 5A, measure the voltage as close to the battery as possible, and then disconnect the charger for a few minutes (with no other loads or charging) and read the battery again. You will probably end up with three slightly different voltages. This means the voltage the app sees (assuming this is just the charge controller and not a BMS like found on some Li Ion/LiFePo packs) will always read slightly higher than what the battery actually sees. Hopefully you can find someone with the same type of setup and experience with the same charge controller and app.