Duel Use of Lithiums in Cart and Boat

[Hunter450]

With the emerging lithium market of drop in replacement for lead acid, I'm researching the possibility of having a set of 4- 12 volt 100AH lithium batteries serve both my 48 volt DS cart and my fishing boat. I use the cart and boat at different times of the year so moving the pack would not be an issue. My DS cart has an OBC so that would be by-passed and I would purchase a 4-bank lithium charger that charges each battery separately. These batteries have their own BMS. The one concern I have is determining the max amp draw of my MOT-A4 motor. I seldom use more than half throttle on the cart and typically cruise around 10mph on trails.

Thoughts?

[bronsonj]

What controller do you have in your cart?

If the motor is capable of drawing 9,000,000 amps but the controller can only draw 200 amps then your max draw is 200 amps.

[Hunter450]

[QUOTE=bronsonj;1636038]What controller do you have in your cart?

Alltrax XCT500

[Hunter450]

Originally Posted by bronsonj

What controller do you have in your cart?

If the motor is capable of drawing 9,000,000 amps but the controller can only draw 200 amps then your max draw is 200 amps.

In my case, I have more controller amps (500) available than the motor can draw. I performed three run test and the road hill climb was the most demanding at 290 amps peak. So, my limitation of the drop in lithium's I'm considering is the max continuous current draw of 100 amps. I set my XCT controller to limit the battery current draw to 100 amps and it made a huge difference in performance. I plan to do the same 3 test runs to compare but I'm having my doubts that drop in lithium may not work for me.

[Sergio]

Lowering the throttle rate will also reduce the motor current demand during acceleration as it prevents the motor from getting too deep into its inefficient region.

[Hunter450]

Originally Posted by Sergio

Lowering the throttle rate will also reduce the motor current demand during acceleration as it prevents the motor from getting too deep into its inefficient region.

Yeah Sergio, from memory I think my throttle rate is set at 25%. BTW, I just checked the Trojan Trillium spec sheet and those batteries have a 250 amp continuous current rating which I could easily adjust to but at a premium cost. I'm curious if other members with big controllers/motors that have done the DIY packs are managing the high amp draw.

[Sergio]

The higher capacity Trillium, 92AH and 110AH can deliver 250 amps only for 30 seconds at a 77F temperature, much less when they get hotter.

[Hunter450]

Sergio, you are correct. The data sheet I have was from Oct 2018. Trojan has updated the Trillium specs on their website. Thanks!

[Hunter450]

Well, with the use of the Alltrax Tool-Kit program I was able to perform some run test and capture information to verify whether the 100AH drop-in 12 volt lithium batteries could safely power my cart under different conditions. First, I ran the cart on FLA settings for flat road and road hill climb. My A4 motor pulled 290 amps on the hill climb and sustained a 12mph speed. This was the most demanding for power. Then, I reset the controller to allow only 100amps to be pulled from the pack to simulate the max I could draw from the lithium pack. On the flat road run the cart did Ok but I noticed the fast/head jerk acceleration was gone. I did get the cart to 21mph on the flat road test. Then came the road hill climb test. The cart did pull the hill but at 5-6 mph. It felt like a 36volt golf course cart loaded and wondering if it was going to make it to the top. For what I mainly use the cart for the 100AH limitation will not work for me however, if I was running on coastal flat roads and staying out of the sand, this drop in lithium would probably work.