RXV Torque Setting

[JohnnieB]

Originally Posted by sunking

Johnny B are you derating the battery Peukert Law effect to 4 Hour discharge rate? Example a T-105 20 rate is 225 AH (11 amps) at 45 amp draw the AH capacity drops to 167 or 4 hour discharge rate.

No, I just subtracted 45AH from the published AH capacity @ 20hr rate on all of the batteries listed. The premise is that the cart is driven, stop and go, from Point-A to Point-B and it takes 45AH @ 48V to move the cart that distance. Since the discharge rate during stop and go driving is variable, crunching the Peukert Effect into the equation would be difficult, to say the least.

Actually, the Peukert Effect comes into play when using the AH @ 20 hr rate because the discharge rate for lower capacity batteries is less than it is for higher capacity batteries. IE: 20 hr discharge rate is 7A for a T-1260 (12V-140AH) and 10.2A for a Ranger-160 (8V-204AH). Ironically, that results in lower AH batteries having a slightly elevated AH rating, if not for that, the differences in estimated lifespan might be more pronounced.

I used the 20 hr rate because that is the rate most people are familiar with and all I have to work with is the published data and AH @ 5 hr rate is the most demanding rate I have for Trojan batteries. I'll have to run those numbers and see if the ratios change significantly.

From the Range comparisons I used RC Minutes @ 56A, so the Peukert Effect is included, but in actual use, the average amp rate while be higher.

[sunking]

Originally Posted by cgtech

Less weight, less beer, i dont think thats gonna work...... Lithium batts will shave about 240lbs. off.

Lithium is my answer, but that digs deep into the beer budget.

[sunking]

Originally Posted by JohnnieB

From the Range comparisons I used RC Minutes @ 56A, so the Peukert Effect is included, but in actual use, the average amp rate while be higher.

OK 56 amp rate is close but still a bit light on amps. I have had two carts, one DC and now AC. I used Coulomb Counting as a gas gauge on both and to do that require current transducers. It allows me to average the current and what I found is 65 to 75 amps is about the average discharge @ 48 volts (roughly 2.1 Hp). But if you know where to look in Trojans Web Site you can get the Minutes @ 75 amps for all the Golf Cart batteries. CLICK HERE to see it and scroll down to page 7. That should get you pretty close to realistic numbers. For whatever reason Trojan does list minutes at 56 amps on their 8 and 12 volt golf cart line but not 6 volts. I have no idea why not all voltages.

[jdunmyer]

Thanks for the info on the DC -> DC converter. My RXV was bought new from a dealer, and it does have the factory-supplied lights.

I find it interesting that the brake lights are powered by a feed from the controller, not the converter. The tail/headlights are powered by the converter.

[sunking]

Originally Posted by jdunmyer

Thanks for the info on the DC -> DC converter. My RXV was bought new from a dealer, and it does have the factory-supplied lights.

I find it interesting that the brake lights are powered by a feed from the controller, not the converter. The tail/headlights are powered by the converter.

I think that is because you do not have brakes, it is all done by Regenerative Dynamic Braking using the motor and resistor under the seat.

[JohnnieB]

Originally Posted by sunking

OK 56 amp rate is close but still a bit light on amps. I have had two carts, one DC and now AC. I used Coulomb Counting as a gas gauge on both and to do that require current transducers. It allows me to average the current and what I found is 65 to 75 amps is about the average discharge @ 48 volts (roughly 2.1 Hp). But if you know where to look in Trojans Web Site you can get the Minutes @ 75 amps for all the Golf Cart batteries. CLICK HERE to see it and scroll down to page 7. That should get you pretty close to realistic numbers. For whatever reason Trojan does list minutes at 56 amps on their 8 and 12 volt golf cart line but not 6 volts. I have no idea why not all voltages.

Your PDF decoding software must be better than mine. All I see is hyphens in the 75A column for the 8V batteries. That is why I used 56A.

Since they publish the 25A, 56A and 75A data for the 12V batteries, I also have no idea why they leave off the 75A for 8V batteries and 56A for 6V batteries. I've tried interpolating and extrapolating to fill in the blanks, but I'm unsure of the validity of the results, so I avoid using it in the charts and stuff I post for all to see.

I occasionally capture the monitored data from my Alltrax DCX500 on a laptop and when I crunch them together, I average about 67A total motor current while the motor is drawing current. (0.2A min and 430A max over ~140 minutes of running time)

My bucket list includes adding ammeters and voltmeters to both field and armature circuits (sepex motor) and drive a tachometer from the unused motor speed sensor. Then capture the digital readouts on video.

Basically, a poor man's dyno.
It ought to give me some fairly accurate data from the electrical aspect, but I'll have to estimate the torque being generated based on known efficiencies at various RPM and field excitations.

[JohnnieB]

Originally Posted by sunking

Johnny B are you derating the battery Peukert Law effect to 4 Hour discharge rate? Example a T-105 20 rate is 225 AH (11 amps) at 45 amp draw the AH capacity drops to 167 or 4 hour discharge rate.

I finally spotted the source of your question.
I screwed up in the column headers.

The 45A in the sixth and seventh column from the left, should read 45AH.

I used the T-1275 as a baseline and discharged it to 70% SoC, which is 45AH taken out of a 150AH battery.
Then I took the same number of AH out of all the other batteries to simulate the same cart making the same trip using different battery pack configurations.

Originally, I use a 70% SoC for the battery I used as a baseline in a caparison of 6 x 8V and 8 x 6V 48V packs, so lesser AH batteries wouldn't be discharged below 50% SoC, and just carried the 70% SoC point over when I compared 4 x 12V vs 6 x 8V. The gap between highest and lowest AH is lower in the latter, so I could have used a lower SoC, but I didn't.

[sunking]

Originally Posted by JohnnieB

YSince they publish the 25A, 56A and 75A data for the 12V batteries, I also have no idea why they leave off the 75A for 8V batteries and 56A for 6V batteries. I've tried interpolating and extrapolating to fill in the blanks, but I'm unsure of the validity of the results, so I avoid using it in the charts and stuff I post for all to see.

Perhaps I can help by sharing some information with you. I sit on the IEEE committee 450 and 484. After years of testing data we have come up with a Peukert Correcting Factor that can be applied to any Flooded Lead Acid Battery for design and estimation purposes. Gets you real close within 5%. Based on 20 Hours Discharge rate try these correction factors. Multiple the 20 hour published rate at the new discharge rate Correction
Factor. For example a 220 AH battery at the 4 hour discharge rate 220 AH x .65 = 143 AH.

100 Hour = 1.33
72 Hour = 1.25
20 = 1
15 = .95
12 = .9
10 = .85
8 = .8
6 = .75
5 = .7
4 = .65
3 = .60
2 = .50
1 = .35

You can really tell the good manufactures when they publish specs like this one. Ever hear of a 5 year warranty on a golf cart battery? This one has one

[JohnnieB]

Originally Posted by sunking

Perhaps I can help by sharing some information with you. I sit on the IEEE committee 450 and 484. After years of testing data we have come up with a Peukert Correcting Factor that can be applied to any Flooded Lead Acid Battery for design and estimation purposes. Gets you real close within 5%. Based on 20 Hours Discharge rate try these correction factors. Multiple the 20 hour published rate at the new discharge rate Correction
Factor. For example a 220 AH battery at the 4 hour discharge rate 220 AH x .65 = 143 AH.

100 Hour = 1.33
72 Hour = 1.25
20 = 1
15 = .95
12 = .9
10 = .85
8 = .8
6 = .75
5 = .7
4 = .65
3 = .60
2 = .50
1 = .35

You can really tell the good manufactures when they publish specs like this one. Ever hear of a 5 year warranty on a golf cart battery? This one has one

Thank You - Thank You - Thank You

I'm halfway decent at crunching numbers, I just have problems finding the right numbers to crunch.

The correction factors have been added to my stash.

With that info, I can probably get pretty close for the run-time minutes at the missing Amp rates.

----------
You've got that right, not many battery manufacturers provide that much information. Crown lists there AH down to 2Hr on their individual spec sheets and some other do also, but not many. That's what happens when lawyers and accountants run engineering companies.

[HiTechRedNeck]

Originally Posted by jdunmyer

thanks for the info on the dc -> dc converter. My rxv was bought new from a dealer, and it does have the factory-supplied lights.

i find it interesting that the brake lights are powered by a feed from the controller, not the converter. The tail/headlights are powered by the converter.

Tail lights should be powered by the same voltage reducer as lights ect.
the brake light RELAY should be powered by feed from controller.