Minimum lithium ah for shuttle

[dougs_huntingcart]

1998 EZGO shuttle
I have 5.5 year old ranger 160's installed in this shuttle and considering a move to lithium power by the summer or longer depending on the performance of this set. The purpose is to achieve a significant weight reduction and gain range as well.
We usually get less than 5 miles out of our drive because of the hills...depending on our route, (according to my watch) we gain about 236 ft of elevation versus 315 ft of loss . Lots of up and down hills an elevation of 900~1100ft above sea level.

Considering this cart, the area we use it and the usual passenger load of 4+, would a minimum of 100ah lithium set up be considered minimum? Or what would be your suggestion? Thank you in advance.

[Volt_Ampere]

What voltage are you running? If 48V, I would say you want a minimum of 100AH.

[dougs_huntingcart]

Originally Posted by Volt_Ampere

What voltage are you running? If 48V, I would say you want a minimum of 100AH.

yes 48v. cart new was spec'd for 8 - 6v batteries .

[Sergio]

As far as AH you need about half as much in Lithium as You have with FLA to get the same or better performance and range.

Your existing Lead Acid pack cannot deliver anywhere close to the 20 hour rate at the average discharge rate used in a golf cart and that number is also not realistic since it assumes that your cart could actually reasonably operate when the FLA batteries get below 30% SOC.

The average current rate at your cruising speed is more important for a trouble free operation.

As long as the lithium setup you are considering has a continuous discharge rate that exceeds your average cruising current, you can setup your controller not to exceed the lithium BMS "Max discharge Rate" as it is unlikely your cart will use more than the average cruising current rate for an extensive period of time.

If Your controller has data logging capability or you have an amp meter in your cart you can use that to get the needed information.

If not, You may want to consider getting an inexpensive amp meter to get a baseline idea instead of guessing how much current your specific cart is consuming given your specific driving conditions.

[dougs_huntingcart]

Originally Posted by Sergio

As far as AH you need about half as much in Lithium as You have with FLA to get the same or better performance and range.

Your existing Lead Acid pack cannot deliver anywhere close to the 20 hour rate at the average discharge rate used in a golf cart and that number is also not realistic since it assumes that your cart could actually reasonably operate when the FLA batteries get below 30% SOC.

The average current rate at your cruising speed is more important for a trouble free operation.

As long as the lithium setup you are considering has a continuous discharge rate that exceeds your average cruising current, you can setup your controller not to exceed the lithium BMS "Max discharge Rate" as it is unlikely your cart will use more than the average cruising current rate for an extensive period of time.

If Your controller has data logging capability or you have an amp meter in your cart you can use that to get the needed information.

If not, You may want to consider getting an inexpensive amp meter to get a baseline idea instead of guessing how much current your specific cart is consuming given your specific driving conditions.

Thanks Sergio. I'll hook up my computer and grab some data. I have the Alltrax SR48500 controller. I completed re building this cart a few weeks ago, so its probably a good time to check this information.

[ThreeCW]

Originally Posted by dougs_huntingcart

The purpose is to achieve a significant weight reduction and gain range as well. We usually get less than 5 miles out of our drive because of the hills.

Your Trojan Ranger 160's are rated at 204 amp-hrs (20 hr rating). To optimize the life of a lead acid battery, it is recommended to not run them below a 50% discharge if possible. Thus, your 160's effectively deliver 50% of the 204 amp-hrs or 102 amp hours for your 5 miles of hilly driving with a loaded cart.

Lithium batteries are usually set up to deliver approx. 80% of their stated amp-hr rating ... so a 100 amp-hr pack would deliver approx. 80 amp-hrs of energy. As you know, the lithium pack is a lot lighter than the lead acid pack, so instead of getting 80% of the lead acid distance (4 miles) your cart might still get the 5 miles you are getting now.

Your stated purpose is to reduce weight and gain range ... it does not look like a 100 amp-hr lithium pack will meet your gain range objective and you will need to consider a larger pack.

Originally Posted by dougs_huntingcart

Lots of up and down hills ... usual passenger load of 4+

A heavy cart and lots of hills requires a lot of amps from your batteries. Your driving style / speed requirements can also affect the amp requirements ... if you need to drive with the pedal to the metal to maintain speed up a hill, that is going to result in a higher amp requirements as well. I did some testing with my heavy cart today ... driving up a moderate hill, driver only, not much additional weight, at a moderate speed (estimate ~12 mph) and I was at a battery discharge rate of 250 to 300 amps. I expect you might see similar amps drawn under your conditions.

As Sergio suggests, in order to properly spec a new lithium pack, you need to get a good understanding of your present (and future if any changes are planned) amperage draws. You need to consider your continuous amperage, peak amperage and duration of peak amperage to size your lithium pack when you have a heavy cart. Some lithium batteries are rated for only 1C continuous discharge rate (i.e. 100 amp-hr battery = 100 amp continuous discharge). Others may be rated higher ... 2C or 3C. Peak discharge rates and durations also need to be factored in ... if you are climbing a hill at 300 amps and the hill is 10 seconds long that is one situation ... you also might be climbing a hill at 300 amps that is 2 minutes long ... and an entirely different lithium battery specification may be required.

[Pat911]

You will not be getting 102Ah out of the 204Ah rated batteries. The 204Ah rating is at C/20 rate, fully loaded going up hills and you’d be lucky to get half that. Halve that again for 50% discharge and you end up with about 50Ah.

100Ah Lithium, even allowing for 80% discharge will give 80Ah, or over 1.5 times the range.

Cheers
Pat.

[ThreeCW]

Is the 100 amp-hr lithium not also a C/20 rate?

Updated:

Using the Trojan Ranger 160 as the example battery, it has a 204 Ah capacity at C/20 and a 169 Ah capacity at C/5 (as shown the spec sheet below).

I had a quick look at 5 or so lithium batteries online and all of them only quoted a single Amp hour rating ... none of them even identified at what rate. I also looked at the Trojan Trillium 12.8 v 110 Ah ... it quoted 111 Ah at C/20 and 110 Ah at C/5 ... so the capacity does not change much over various discharge rates for lithium batteries.

So I agree that a more valid comparison might be to use the C/5 rate for both Lead Acid and Lithium. So for Lead Acid use 50% of C/5 = 50% x 169 = 85 Ah and for Lithium use 80% of C/5 = 80% x 100 Ah = 80 Ah (remembering that we are comparing to the 100 Ah batter not the Trillium 110 Ah). So we are back essentially to the same range in the higher discharge rate comparison (neglecting the effect of the lower battery weight with lithium).

[Sergio]

ThreeCW, FLA ratings are tricky, You only get that 20hr rate if you discharge that trojan battery at a constant 10 amps.

The amount of energy you can get out of an FLA battery is not fixed, it varies depending on the actual discharge rate according to its Peukert coefficient, which says the faster you get the energy out the less total energy the battery can deliver.

The AH ratings on Lithium cells are regardless of the discharge current as they are practically 100% efficient on energy storage (not 100% electrically efficient as it still takes a little more energy to charge than in it is actually stored).

That Trojan Ranger you posted can deliver 56 amps for 160 minutes (2.7hours) so if your cart consumes 56 amps at cruising speed, you only get 56 amps * 2.7 hours = 150AH.

It gets worst, look at the little "B" superscript by those ratings, The battery will only deliver that much energy if you use it until it gets down to 1.75vpc or your 48v pack is down to 0% SOC or 1.75vpc * 24 cells = 42v.

Furthermore it has the qualifier "Capacities are based on peak performance at 80F temperature".

That is why I said earlier that it was not realistic your cart could actually reasonably operate down to that low level needed to obtain the AH rating.

The Lithium cell on the other hand will deliver good performance all the way to near empty.

When you consider the weight reduction which will further reduce the discharge rate, You can get a good guestimate of half the FLA 20hr rate when looking for a lithium battery.

[dougs_huntingcart]

Originally Posted by Sergio

ThreeCW, FLA ratings are tricky, You only get that 20hr rate if you discharge that trojan battery at a constant 10 amps.

The amount of energy you can get out of an FLA battery is not fixed, it varies depending on the actual discharge rate according to its Peukert coefficient, which says the faster you get the energy out the less total energy the battery can deliver.

The AH ratings on Lithium cells are regardless of the discharge current as they are practically 100% efficient on energy storage (not 100% electrically efficient as it still takes a little more energy to charge than in it is actually stored).

That Trojan Ranger you posted can deliver 56 amps for 160 minutes (2.7hours) so if your cart consumes 56 amps at cruising speed, you only get 56 amps * 2.7 hours = 150AH.

It gets worst, look at the little "B" superscript by those ratings, The battery will only deliver that much energy if you use it until it gets down to 1.75vpc or your 48v pack is down to 0% SOC or 1.75vpc * 24 cells = 42v.

Furthermore it has the qualifier "Capacities are based on peak performance at 80F temperature".

That is why I said earlier that it was not realistic your cart could actually reasonably operate down to that low level needed to obtain the AH rating.

The Lithium cell on the other hand will deliver good performance all the way to near empty.

When you consider the weight reduction which will further reduce the discharge rate, You can get a good guestimate of half the FLA 20hr rate when looking for a lithium battery.

Thank you for all the information. We plan to use this cart in this area which has plenty of hills. I want to create a power source to accommodate our needs. I created a log from this morning with 4 of us (let's say 650lbs) . I chose the hill to demonstrate the most strenuous climb that the cart is required to undertake, multiple times a day. We plan to use the cart to travel around this area for a solid 10+ miles a day. I removed all the data that did not show value or errors.
On a side-note, I have an RXV with the 350amp controller that does this whole area like it's nothing. I mean we can drive all day, so the expectation is to have this cart do the same, unless that is not a reasonable expectation....then I just need to sell it.... which then makes me wonder, and get what that would meet our expectations in a 6 seater.

I have a D&D 10:2 motor (170-010-000-0002)

The distance is .14 miles .
Travel time 1.26
Elevation : 915ft to 1026ft.

I just did another run on "flat" ground and attached the pdf with flat.
That was +7ft over .14 at 14mph max