You need the manufacturer's specs for the cells you get. Generic LiFePO4 numbers are max of 4.1 volts, recommended charge to 3.65 volts (but constant-load discharge testing showed 3.55 volts gave the rated AH capacity with the cells I have). Minimum is 2.0 volts but I prefer 2.5 volts/cell (that's also where most of the BMS units I've checked are set).
I'd guess charge to 3.4 and discharge to 3.0 would extend the life but see what the maker's discharge test charts show as the "middle 50%" of the batteries' "happy range".
3500 / 365.25 = 9.58 years so any increase in cycle life may run beyond the useful life of the rest of the cart ;-)
The cart's a 1988 it's well past it's prime now. lol
Their specs are little looser than what I posted they say you can go a bit farther in both directions but I want them to last as long as possible. Heck in all honesty I doubt I ever get close to the low side specs it's the high side I think I'll need to keep an eye on.
Can not wait to get some taller tires. Got it stuck doing evening chores. After that I dug out a twenty year old set of 18x8 AG treads and put them on another set of rims I have. It won't get stuck to easy now until you hang the rear end on something. I know because we did it! lol we were playing a little by then though. lol lol It's a mud pie out there!
3500 cycles to 10% from 3.65 volts 4500 cycles to 17% from 3.55 volts 6500 cycles to 20% from 3.30 volts
20% = 2.8 IIRC
Last Edit: May 14, 2022 19:23:28 GMT -6 by biggkidd
6500 / 365.25 = 17.79 years. Not quite the "lifetime" battery that some LTO batteries appear to be with their claimed 20,000 charge / discharge cycles: 20000 / 365.25 = 1 cycle/day for 54.75 years. If you find some free LTO cells, I'd like 12 volts, 800AH worth of them ;-) No more than I'd be discharging them, 12 volts, 800AH of LiFePO4 would fit the space I have available and be long-term viable for fridge and furnace with 1500 watts of solar panels and sun every other day - the fridge could also be disconnected overnight (it's rated to keep things for 8 hours w/out power) so the furnace could have more power if needed overnight.
I've done a lot of running back & fourth round and round doing things today. Still made more Watt hours than I used by a couple hundred. Which tells me once I get a decent set of batteries then all should be well.
I think my newest favorite thing about having this is everywhere I take it to work I have a comfortable place in the shade to sit down. Which came in really nice today.
Last Edit: May 15, 2022 16:33:47 GMT -6 by biggkidd
Since I lifted the cart the small trailer will not fit it. Six inches is a lot to try and compensate for in two feet. lol So I went digging through my junk and found an old small cheap trailer frame from harbor freight to pull behind the golf cart. Had to adapt the tongue but it works. Now I've got to figure out a bed for it. It's one that gets a half sheet of plywood for a bed. That ain't gonna cut it around here. Someone, maybe Chris gave it to me years ago. I had a water tote on it for awhile but they kept popping the hitch loose more weight & leverage than the catch could handle. That was after the original tongue ended up pretzel shaped! lol Oh well I'll figure something out. Wish I had some aluminum plate.
If you had a typical 275 gallon IBC liquid container, I'm not surprised that little trailer gave up the ghost ;-) Water is heavy at 8.3lb/gallon, so that tote had 2274lb of water in it plus the weight of the tote itself. I don't think that trailer was rated at over a ton of capacity...
Storing and moving heavy things takes some thought and research. I saw a YouTube video of how "bad" the Harbor Freight 2500lb ATV winch was. If your ATV is in mud halfway up all four wheels, not even a 12,000lb Warn winch will get it out of the mud with a straight pull - it just plows through the mud, moving you XX feet from where you started but still hub-deep in the mud. To get out of the mud, you need some lift - put the hook at the end of the winch cable 6, 8, maybe even 10 feet up in a tree and let it lift the front of the ATV out of the mud slowly as it pulls. Operator ignorance does NOT make a product "bad". It may show the operator's lack of knowledge - or prove that he slept through his high school physics class ;-)
Something like that for a fixed drop could be welded up from angle iron (bedframe material), U-channel or square tube. Even Harbor Freight's bottom of the line 90 amp flux core welder can work on those materials if you take care to ensure a good weld. I extended some 1/2" steel rod (shepherd's crook supporting two bird feeders) to get it above the squirrels' jump capability by cutting the rod and welding in some angle iron to extend the rod's length. Not pretty, but it's still out back about 10 years later.
Oh yeah I knew that little trailer was to light for the water tote but sometimes ya just have to use what ya have on hand. I'm sure you know what I mean.
The cart has limited towing ability as it's ALL aluminum frame. The OEM towing setup is just like a lawn mower flat metal with a 1/2 inch hole for a pin. I looked at a half dozen different ways to hook it up with a regular hitch and may still one of these days. Going to need another aluminum cross member welded in first though. I think I'll want to take the body off before I try and beef up the frame with said cross member. The rig I was working on today will work for now.
Oh it'll have no choice but drop as the frame is somewhat tucked up in the body. Being as it is the frame a nd Aluminum I'd rather not drill it any more than I have to. I did consider using some flat bottom U bolts or brackets to go around it.
Unfortunately I need to give the cart a rest and take care of some other pressing homestead matters. Spring has sprung.
3/8 are my favorite all around use bolts in grade #5 I buy them by the pound! I only use grade two when I want it to brake before whatever it's fastening and grade eight anytime it just can not brake for any reason aka high stress loads.
After using this several days during fair weather I'm thinking I may not need to be in such a hurry to get batteries. I still want to get them but it's looking like they aren't a high priority at this time. The solar panel is consistently making more power than I'm using on a day to day basis. Granted we are in spring and summer is coming which will allow some breathing room. I do expect I should get them before winter though.
That's the real world test of applied solar power - if it does what you need, the system is adequate ;-) You need to know the low temperature characteristics of the batteries you are using. Sample temperature info for a 12 volt, AGM battery:
Temperature versus rated capacity of the UPG UB121000 (12 volt, 100AH) AGM battery. at 0.05C discharge (20 hour rate) 0.1C discharge (10 hour rate) 77F.....100%....................77F.............100% 50F......95%....................50F..............85% 32F......87%....................32F..............77% 14F......78%....................14F..............68% -4F......65%....................-4F..............50%
In golf cart service, you'd be looking at the 10 hour ratings (or the 5 hour or 8 hour rating if available).
Go to this site: www.solarelectricityhandbook.com/solar-irradiance.aspx It will give your location's useful sun hours by month, based on which way the panels face and their angle - including flat. I don't think this site factors in weather, although there are some that do.
There are also some solar vendors that average the best and worst months and use that numbers as your "yearly average solar hours" which is a bald-faced lie - it's the average of the best and worst months' average hours. That "yearly" average does NOT apply to the actual power available in January :-(
My summer hours peak at 5.2 in May and are 3.3 in December. If I had adequate open space facing South, I might be good for using solar. Until such time as I do that, I have 60-70& of the sun I might otherwise have and I plan accordingly. Cutting someone else's old growth trees would give me more sun time but might make them unhappy - unless we both needed the firewood. The spreadsheet I use figures in the most likely output from the solar panels (no more than 73%, their NOCT rating) so I'm less likely to be in the dark from being too optimistic about how much sun we'll have. That also provides a bit of cushion for partly cloudy days when we still have some sun, but I assume there will be near zero solar power on cloudy or rainy days, although there's sometimes a bit of power - but 5 watts from a 250 watt panel on a very cloudy day doesn't even power the laptop that's used to monitor the solar system :-( The only accurate way to know how much power you're using from or putting back into the batteries is with an AH meter that does up/down counting. When the charge AH exceeds the discharge AH (by some percentage determined by the type of batteries), the batteries are fully charged. For the AGM batteries I'm currently using, that number is 107 to 115% of the discharge AH. I usually accept 10% more charge than discharge when the batteries are at float voltage as fully charged.
Last Edit: May 18, 2022 14:48:33 GMT -6 by papaof2
I have a meter for power made and another for power used so far I'm using about 1/3 to 1/2 the watt hours I'm making on decent days. That's not to say pure sunshine but mostly sunshine. These batteries are on the way out as they self discharge quite a lot but as you said the system is working. Once I switch to some sort of lithium based battery I doubt I'll have any trouble. The only downside I see so far is I will have to acquire some sort of battery warming tech for the lithium setup in winter.
Today I had the cart down quite a steep & rough hill. I am sort of wondering if loosing the battery weight (near 300lbs) will help or hinder in those situations? Today it came up without any tire spin. Although I do have AG (tractor tread) tires on the rear now.
When you change the batteries, put the new ones either directly over or behind the axle to get the most traction benefit from their weight. If you need more weight back there, 5 gallons of water is ~42lb plus the weight of the container. Just add a few jerry cans wherever there's a place to mount them - and you'll always have some extra water with you.
Or put a karaoke system and the batteries that power it on the back of the cart for that extra weight. Then you'll always be ready to set up an instant party ;-)
Played hooky this afternoon and rode the cart to the neighbors. That's a 4 mile round trip over some rough country. Did the chores before and after plus some other running around here close. All in all I'd say about 6 miles. Anyways I used 936 wh and it made 1655 wh from solar today. I did take care to remember the proverbial rotten egg on the pedal all day.
"Anyways I used 936 wh and it made 1655 wh from solar today."
Unless you used the cart a good bit previously and it didn't get recharged, I'd be concerned about the charge AH being that much higher than the discharge AH - possibly indicating the batteries are farther gone than you thought.
Yeah they are pretty well shot. When I first started working with these batteries you could watch the multi meter and see them self discharging. That has slowed way down and they seem to be gaining a little ground with the long slow solar charging. Today I could actually feel a little more kick in the seat when running it. I know in the past long slow trickle charging has allowed me to get another year or two out of a starting battery. This seems a bit more noticeable since you can feel more than hear the difference. I also wonder if the shaking and vibrations this thing gets living well of the pavement hasn't knocked some sulfation off the plates along with the slow charging. Speaking of which it's about time to check the battery water. Not one of my favorite jobs. These are the first batteries I've had in more than a decade that you have to add water to.
Another thing I noticed driving it today is it can't really go very slow on flat ground pushing the pedal just hard enough to make it move makes it run about a fast walking speed. Which I hadn't really noticed that before either. I'm thinking yesterday's long bouncy rough ride stirred the batteries up good or had some effect on them somehow. It also seems a bit faster on the top end. As rough as it is around here you mostly want to crawl not fly.
The rough ride could have shaken some battery connections into a better place. Have you removed all the cables, cleaned all the cable connectorss and battery posts, and then made certain the connectors were tight on the posts?
I can think of several ways to get slower speeds but changing the battery pack from 36 volts to 24 volts is probably the simplest ;-) Anything else either wastes power (resistive dropper) or is expensive (electronic speed controller). The electronic speed controller is attractive because it uses pulse width modulation (PWM) to effectively drop the power to the motor by pulsing it on and off at a relatively fast rate (comparted to the motor's mechanical inertia). You get full power for starting but it can start and move very slowly.
You do have to remember that the original engineer was thinking *paved roads*, not *off road* and he designed accordingly. The cart user wanted to get to the putting green or the next hole as quickly as possible so gentle starts, low speed operation, climbing hills and being the winch for birthing calves were not part of the design spec ;-)
Last Edit: May 20, 2022 20:30:33 GMT -6 by papaof2
I switched if from 36 to 48 volts. I like the fact it has more torque and the speed it has when wanted. There are times were slower would be nice but it's definitely something I can stand dealing with. There are also times faster would be better. But like you said I'm not using it for what it was designed for. I think it does very well for what it is and what I've spent.
As to using a PWM I might do that on the other cart if I ever fix it but I feel the resistor coils are a lot less likely to have issues with any electrical impulses from man or nature. Like nearly everything I own I think of this as a prep in several ways. One cheap transport in times of need two it's another 48 volt bank we could run the house from for a short while if we had to. Third it's sort of stealthy as quiet as it is.
Regen braking would sure be nice to have as I am putting a hurting on the brake shoes. I've already adjusted them and they need it again now. Nothing but hills here you're either going up or down.
A high end PWM speed controller might include regenerative braking ;-) The question then becomes how much are the conveniences - and possibly greater range - worth? A quick check online shows some nice "upgrade" packages for $1600. The golf cart manufacturers claim about 15% more miles when you have regen braking.
One possible partial solution would be to have two 24 volt battery banks that can be switched from series (48 volts) to parallel (24 volts) depending on what you're using the cart for (speed vs power). That can be done either with heavy duty switches (100 amps or more?) or relays (possibly shorter wiring and less power loss, but switches are inherently more reliable). Either of those should be at least EMP resistant and 100 amp switches should last just about forever if you always take your foot off the go pedal before switching.
Which brand and model cart? It might be possible to add some shadetree mechanic regen braking but you'd need at least some heavy duty relays and possibly some electronic controls to prevent overcharging the batteries (not likely but overcharging can destroy lithium batteries much faster than it does lead-acid batteries). The quick and dirty "electric braking" would be to put a load across the motor windings when you hit the brake pedal and at least benefit from that extra braking effect and a bit less wear on the brake shoes. Being in a dusty environment instead of on the golf course could make the brakes wear out faster.
Last Edit: May 20, 2022 21:20:22 GMT -6 by papaof2
They are both Club Car brand. Yes Navitas and several other companies make some real nice upgrade kits. Which I plan on using if I get the other cart going in the future for now I think I'll stick with old school on the one cart I have up and running.