72v -vs- 48v efficiency with Navitas AC drive in Club Car Onward

[fstop]

I just recently switched out the stock motor / controller in my Club Car Onward (2018, factory lifted, 23" tires) to a Navitas 5KW AC drive system.

Performance is decent - 30 ish top end, better than stock acceleration (but not by a whole lot).

I have the stock 48v 6x8V PD Plus Club Car batteries (US Battery I think).

At WOT on a just-off-the-charger battery, voltage drops to 44.5V on level pavement. Drops to 42.5 under hard acceleration. Batteries are in good shape, 6 months old and doing what they should - motor draws a lot of current (I have #2 wires on cart, but didn't make any difference from the stock #4).

I believe that this 5KW AC system was designed more for applications that are more extreme than mine - lithium and / or higher voltage.

Anyway, in looking at the stock 72v EZGO AC cart, which uses 6x 12v FLA, this cart appears to be popular because of good range (and power potential with aftermarket or modified controller).

I use my cart for neighborhood transportation, and am not racing other carts, so I'm not interested in killing the range or making the cart scary, but would like to find a sweet spot of solid performance that makes the cart fun to drive without giving up too much range for practicality. I realize the faster you go the worse the range all things being equal, but for short bursts here and there it's nice to have the power when you don't need to go 20 miles on a charge.

So I wonder if using around 440LBS of batteries that make 72v would be more efficient than using around 400LBS of batteries that make 48v?

Obviously EZGO thought so, but their motor / controller was designed for it.

My Navitas is good to 72v, so that isn't a problem

Higher voltage generally means lower amp-draw also, so possibly the voltage sag would be less on the 72v system, and some less capable LiOn packs may work also with 63-72v due to less amp draw while still delivering improved performance.

I'm sure somebody knows how 72v FLA compares with 48v FLA (same number of batteries) using this Navitas AC setup.

Thanks for any insight on the subject.

[Gainerman]

Does that controller offer data logging ,? Have acess to a amp clamp ? 3 decent 12v batteries ? And a smaller set of wheels and tires? What's the rpm limit of that motor? I would try to find the sweet spot of your personal combination then go from there if you are only utilizing half the rpm potential of your new motor and controller and not going off road it may be time to downsize tires

[fstop]

Originally Posted by Gainerman

Does that controller offer data logging ,? Have acess to a amp clamp ? 3 decent 12v batteries ? And a smaller set of wheels and tires? What's the rpm limit of that motor? I would try to find the sweet spot of your personal combination then go from there if you are only utilizing half the rpm potential of your new motor and controller and not going off road it may be time to downsize tires

I agree there is likely a more efficient combination. Tire size will need to stay the same since the cart is lifted and the ride comfort with the larger tires was a primary concern. I suspect that 72v would provide more efficiency overall, even with another 40lbs or so added to the weight if I went FLA.

Ideally I think I need to increase the voltage to a more efficient level (I know 48 isn't it, but not sure if it is 72 or somewhere in the middle), and lose the FLA weight and voltage sag (which further degrades efficiency) under load by going Lithium of one kind or another. Loosing the additional weight of the FLAs would help braking and overall efficiency yet again.

[dougrobling]

I also have the 5kW Navitas, and it has the ability to log current (both motor and battery)
If you check the current draw on the batteries with your 48V system, the same load would draw 2/3 of that amount at 72V.
For instance if you draw 100A at full acceleration now, you should draw approximately 66.6A at that same load with 72V batteries...
I have ordered a 72V 120aH lithium battery for mine for the same reasons.

[dougrobling]

I ran a battery current log on mine today (still on the 48 batteries) and it was averaging right at 100A at 35mph on level ground. It climbed to about 200A on the uphill sections and slowed down to about 25mph. Hopefully the 72V batteries will allow us to maintain higher speeds on the uphill sections as well

[Gainerman]

Wow 100 amps at 35 mph , mine pulls 50 at 35 , with a amd series motor 205 60 10 street tires no windshield or roof .just for reference.

[fstop]

Originally Posted by dougrobling

I ran a battery current log on mine today (still on the 48 batteries) and it was averaging right at 100A at 35mph on level ground. It climbed to about 200A on the uphill sections and slowed down to about 25mph. Hopefully the 72V batteries will allow us to maintain higher speeds on the uphill sections as well

What is your cart setup / tires?

[russb442]

might want to check your brakes also. 100 amps on. level ground is a LOT! maybe its different for the ac set up.