BigBattery Golf Cart 42.9v LiFePO4 and 600A Navitas on 2014 Ezgo RXV

[MrBritGolfFan]

Originally Posted by molfpedal

I just got a dealer app update for the Navitas Tac2 that has a 36v option for nominal pack voltage. That is what you needed for you pack to work. Have you seen that yet?


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Molfpedal. That is very kind of you to think of this thread and post that. I too got the update but I really appreciate you doing that.

Here is a little bit more. Navitas got with me today and I had to download an additional app which is an engineering version. Still get it delivered through Test flight. I was told that a new dealer app with controls will come out soon but until then I can get running with the Navitas Eng app.

Navitas also took in details of my battery spec and then sent me an XML file which I had to save in the Navitas Eng folder on my iPhone. Then when I ran the New app I needed to load custom settings from that file which were based on my pack.

They are going to be adding all this in the dealer app very soon, but I’m guessing they got it to me a bit earlier to get me running again.

There are a ton of settings in the XML and some really great ones for lithium.

Ones that take into account your pack charge rate, and discharge rate. Also surge current seconds (maybe your pack can discharge at surge for 300amps for only 10 seconds and not 30 seconds etc. Navitas said they want to make sure they don’t cook customer batteries) I love This setting as I was concerned about this.

They also have your nominal voltage setting. Max and low voltage setting for the pack.

There are also settings that dictate when the RXV will dump to the resistor based on your pack too.

Then the best part is the limp modes. So as the pack gets to a lower voltage they halve the current capability. So you can feel that cart slow which alerts you it’s time to get home and charge. These settings are all in your control so you can tweak them but I was real glad to know that the cart wouldn’t just come to a dead stop from full speed. At least you’ll know you are in limp mode etc.

Lastly and rather interestingly they said my pack was really good for RXV because it has a high charge rate of 150Amps. This means I can take full advantage of the regen and breaking which produces a surge current. They said some of the other packs out there have small BMS’s with 20amp charge max so they cannot do breaking properly on RXV’s. interesting.

Anyway, I am going to drive around for a week and fully understand my ranges and charges and post results here.

[MrBritGolfFan]

Originally Posted by BobBoyce

Yes, your Curtis controller can be reprogrammed for that and the speed/torque. I do it all of the time. I'm currently in central Florida helping a friend get his machine shop set up. Will be heading home early next week for a Drs appt, then lay out the route for my next programming trip. Send a PM to usgicollector and give him your information. He is the best one to help you get in contact with me.

Thank you Bob. I think I might now be good with the updates Navitas just got to me today. However I will see over the next few weeks. Thank you very much for your help and guidance not just on this post but on all the posts I’ve read from you over the years! Thank you sir! If things don’t work out on the Navitas I will reach out to usgicollector.

[molfpedal]

Originally Posted by MrBritGolfFan

Molfpedal. That is very kind of you to think of this thread and post that. I too got the update but I really appreciate you doing that.

Here is a little bit more. Navitas got with me today and I had to download an additional app which is an engineering version. Still get it delivered through Test flight. I was told that a new dealer app with controls will come out soon but until then I can get running with the Navitas Eng app.

Navitas also took in details of my battery spec and then sent me an XML file which I had to save in the Navitas Eng folder on my iPhone. Then when I ran the New app I needed to load custom settings from that file which were based on my pack.

They are going to be adding all this in the dealer app very soon, but I’m guessing they got it to me a bit earlier to get me running again.

There are a ton of settings in the XML and some really great ones for lithium.

Ones that take into account your pack charge rate, and discharge rate. Also surge current seconds (maybe your pack can discharge at surge for 300amps for only 10 seconds and not 30 seconds etc. Navitas said they want to make sure they don’t cook customer batteries) I love This setting as I was concerned about this.

They also have your nominal voltage setting. Max and low voltage setting for the pack.

There are also settings that dictate when the RXV will dump to the resistor based on your pack too.

Then the best part is the limp modes. So as the pack gets to a lower voltage they halve the current capability. So you can feel that cart slow which alerts you it’s time to get home and charge. These settings are all in your control so you can tweak them but I was real glad to know that the cart wouldn’t just come to a dead stop from full speed. At least you’ll know you are in limp mode etc.

Lastly and rather interestingly they said my pack was really good for RXV because it has a high charge rate of 150Amps. This means I can take full advantage of the regen and breaking which produces a surge current. They said some of the other packs out there have small BMS’s with 20amp charge max so they cannot do breaking properly on RXV’s. interesting.

Anyway, I am going to drive around for a week and fully understand my ranges and charges and post results here.

That sounds awesome. I hope they get it worked out soon. I had a low volt shutdown that was 4 volts above my Bms LV setting. Leroy told me today that they were working the lithium profile, but didn’t elaborate.


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[MrBritGolfFan]

Originally Posted by molfpedal

That sounds awesome. I hope they get it worked out soon. I had a low volt shutdown that was 4 volts above my Bms LV setting. Leroy told me today that they were working the lithium profile, but didn’t elaborate.


Sent from my iPhone using Tapatalk

Yeah it’s exciting stuff. Leroy was who I was on the phone with helping me get going, very helpful and said I could send him my feedback and he would send a new battery file for me to upload to my controller if needed. I can also edit the xml myself too if needed.

[MrBritGolfFan]

While I was waiting on the Navitas update I changed my cart colour and roof from this:

9B32A9D6-A227-4C50-B7EA-69E578DCE870.jpg

To this:

F0D81884-FF58-4C81-A255-E89B44254B94.jpg
4BAE29C3-D384-4497-9633-A4CEA7D8432B.jpg

Really pleased with the result!

[MrBritGolfFan]

Update time!

On sunday i was able to take the cart out and test some of the new software updates.

Navitas had sent me a battery config file (i will ask them if ok to share the XML file on here and if so will post) made for my battery.

I will list some of the items navitas told me on the phone, but would love to share the file as there are probably other items i would miss.

• The battery amp limit, or surge/ pulse/ inrush
• how long the battery can hold that surge in seconds
• when the resistor should kick in at higher voltage to dump overcharge on regen
• when limp mode1 should kick in in volts
• when limp mode 2 - or return home mode should kick in in volts
• what amps to go back to in limp mode
• battery nominal voltage
• regen amps max

my values were set low as navitas took in the spec of my battery from the web and wanted to be safe, which i really was grateful for. I could edit the xml and do as i wish, but some of these settings are based on other settings in the xml, so you have to be careful. My preference is to wait until these settings are in the UI (whenever that will be).

Anyway my continuous discharge was set to 120Amps with a max of 150 amps for 30 seconds.

As a reminder my battery specs are:

Nominal Voltage: 42.9V
Capacity: 88.59Ah (3.8kWh)
Configuration: 13S 6P
Chemistry: LiFePO4
Max Charge Voltage: 46.8V
End of Discharge Voltage: 35V
Max Continuous Charge Current: 150A
Max Continuous Discharge Current: 150A


The file had my nominal at 39v, not 42.9v - im still not sure why other than LFP cells can be 3.0-3.3 (3*13 = 39 and 3* 3.3 = 42.9).

The max amps were set to 150 amps for max 30 seconds. I am sure i can go higher than this, but we just dont know until i can find out more info from either BigBattery or TechDirect. TD said the model number for the battery is PSL040002 - so if anyone out there knows anything that would be awesome...?

One issue i did notice is that i charged to 46.8v, left it full over night and unplugged, next day the BigBattery onboard monitor said 44.4v (im not sure how accurate the onboard monitor is, looks real cheap) i dont know why i lost some volts overnight, could that be because they are second hand cells? i didnt have anything connected to it as have a kill switch turned off?

Anyway, in the file the first limp mode kicks in when my battery gets to around 44v, so i take the cart out and hit the accelerator once (good, not amazing acceleration at 150A) then do it a second time, and the 3rd time is now capped at 100-120amps, and its like a poor lead acid battery system without the acid. I still get top speeds im happy with, just takes a bit of time to get there.

Can get to 22mph easily, and will go to 29 mph if the road is long enough. Its basically always accelerating as the amps are stuck around 100-120A, so i wonder if that would cause more amp hour usage compare to getting to top end faster and then settling for lower amps at steady speed, as when you steady the throttle it will happily stay around 50-80 amps.

I drove around for 2 hours, and covered easily 20 miles. The first 30 mins there were 5 of us in the cart (2 adults, 3 kids) and our 2 small dogs. The remaining 90 mins i was alone and really just trying to test out range. The cart battery at the end was 42.0v.

I charged my cart to full and used my amp monitor i have to tell me how many ah's i had just used. It took 57ah to get it back to 46.8v. What i dont know, is if i lost any ah's when it dropped over night from 46.8v to 44v - i am going to see the drop tonight, and charge and see how many ah's.

Navitas asked me to test out and feed results back, so im waiting on a file update. I could probably tweak it myself, i just dont want to damage anything.

will post more updates when i get them.

[MrBritGolfFan]

interesting stuff, just found this spec sheet on my exact battery, but with no BMS:
https://bigbattery.com/product/48v-l...attery-module/

Much better ratings too!
Electrical Specifications

Cell Configuration: 13s6p

Nominal Voltage: 42.9V

Nominal Capacity: 88.59Ah (3.8kWh)

Available Energy: 3800.5Wh

Nominal Continuous Discharge Current: 133A

Max Continuous Discharge Current: 300A

Nominal Continuous Charge Current: 133A

Max Continuous Charge Current: 300A

Max Recharge Voltage: 49.4V

Max Float Voltage: 46.8V

Over Voltage Limit: 54.3V

Internal Fuse: Yes

i wonder???

Is the over voltage limit accurate for this cell config?

[MrBritGolfFan]

Update.

Navitas sent me a new file based on some updated battery specs.

The changed the continuous to 133A and the surge/ pulse to 300A for 10 seconds.

I tested the cart and this made a big impact. Now the acceleration is pretty good, and gets to 30+ quite quickly.

I am still waiting on confirmed specs from A123 (if they can send them to me) so we maybe still be able to up these limits.

I did notice that Bigbattery have some breand new a123 batteries in that are in 24v packs, and are not too much larger than the normal 12v SLA ones in the cart originally. If i did this again, i might consider 4 of these (two in parallel and in series):

https://bigbattery.com/product/24v-a...free-shipping/

They come with free shipping too, and the specs seem good to me, thoughts anyone?