Lithium Conversions Cuts out at full throttle
 

Hi all,
Just did a lithium conversion yesterday using a 7module Leaf pack with integrated BMS from techdirect club. Stock Controller with plumquick bandit motor on a lifted 2010 Club Car precedent. Pack was charged at 100%.

When I took it for its first test spin it rode fine until I hit full throttle. When I did it died. I hit the tow switch to push it back to my garage and when I flipped it back to Run everything worked fine again. Took a second test run and the exact same occurred.

I did not bypass the OBC in my setup as I have seen others do.

The pack says it will do 60A continuous and peak at 120A. Wondering if I am trying to pull to many AMPs at full throttle? Will a controller change fix this or possible a BMS configuration change? Any help/suggestions will sure be appreciated!!

Re: Lithium Conversions Cuts out at full throttle
 

I agree with you, sounds like one of your components tripped a shutdown. The question would be which one and what are the settings?

What controller are you using? Are you able to plug it into a computer and see/change settings?

What BMS are you using? Are you able to see/change settings? Is the system utilizing relays or a contactor to disconnect for HV/LV shutoff?

As for the OBC, I believe they are only utilized for charging. Not actual driving. Are you using the stock cart charger for the lithium pack?

Re: Lithium Conversions Cuts out at full throttle
 

I took a look at direct tech's web site and find it somewhat difficult to surf through. I see they have 7 module leaf packs, and BMS monitors, and apparently BMS "boards" but the descriptions of these are very short and vague. I can't find any technical information about them nor any "user manuals".

If you can provide a link to the user manual for your BMS that would be helpful. Or you could perhaps call the seller and ask them what they believe the issue is.

Re: Lithium Conversions Cuts out at full throttle
 

If emailed the company to see if I can get documentation on the BMS

Re: Lithium Conversions Cuts out at full throttle
 

You are running 58V nominal which may be too much for your stock controller. It was for mine (Yamaha) and I had to upgrade to Altrax.

Re: Lithium Conversions Cuts out at full throttle
 

Since the BMS is rated at 120A, most likely they have all current, charging or discharging passing thru the BMS. When you exceeded the 120A, the BMS shut you down. If full current from a hopped up golf cart is going to pass thru the BMS, it must be wired thru with at least #4 and be rated 300-400A. This is a much more expensive BMS that way. Check with them via email about options.

That is why the Zeva BMS uses the shunt or hall effect sensor.

I'll bet if you drive like your grandmother is in the seat beside you up to near max speed, it won't trip out. IMHO

Re: Lithium Conversions Cuts out at full throttle
 

I agree, but it does not take a hopped up golf cart, a regular golf cart will use more than 120 amps just to go from 0 to 5mph.

Please keep us posted on what the vendor does (if anything) to resolve your issue.

Re: Lithium Conversions Cuts out at full throttle
 

Here is the vendors reply:

How many pack do you have?
BMS is 60 amp continuous and 120 amp peak if you have 1 pack the current is not enough.
Check your motor and see that is the Amp require
The BMS is 14S Smart BMS
Thanks

So looks like PingEye3 is correct. Also judging by the vendors own video its clear that current flows through this cheap BMS.

SO what to do? I can certainly give things a try by removing the BMS and attaching running 4 gauge to my controller but I'm a little concerned about running without a BMS and/or a smart charger. I could change out the BMS also. Any suggestions? I really looking to get 2-3 rounds of golf per charge.

Re: Lithium Conversions Cuts out at full throttle
 

I would do as PingEye3 suggested and invest in a quality BMS. ZEVA has a good reputation and has served many members on here very well so far.

I wouldn't risk running my lithium pack without a BMS. All it takes is one time to over discharge or over charge a cell to damage your investment.

EDIT: Also, I don't think you're going to be getting 3 rounds of golf out of your 7 module pack unless you live on the course.

Re: Lithium Conversions Cuts out at full throttle
 

Based on the Chinenglish on the reply it looks like TechDirect is a direct Chinese reseller.

Those BMS are designed for toys like e-bikes and scooters, so You will need to make some changes to make it work on a Golf Cart.

Since the BMS can handle the charging current, leave that part alone, meaning the Anderson connector will only be used for the charger connection.

Run new 4ga or 2ga cables for the pack positive and negative directly to the Solenoid B+ and to the Controller B-.

Get a 48v relay coil like the one below to provide the LV cutoff for the cart power.

https://www.mouser.com/ProductDetail...HWoVRadw%3D%3D

Disconnect the wire that goes to the "cold side" of the key switch (the side that only has power when the switch is ON).

Connect that wire you disconnected to the "COM" terminal of the relay.

Run a new wire from the key switch "cold side" to the relay "NO" terminal and to one side of the relay coil.

Connect the other side of the relay coil to the negative coming off the Anderson connector.

Install a diode in parallel with the relay coil, the side with the stripe goes on the same side as the wire from the key switch.

That will allow the BMS to still provide cell level LV and HV cutoff, but instead of cutting the entire current path OFF to the cart, it will only prevent the controller from operating in case of an LV condition.

It will also eliminate your shutdown due to excessive current unless that current causes the pack to drop below a safe level.

Edit:

I just noticed that there are no bus-bars in that design, just the circuit board copper traces to carry the cart current.

Unless they are using pretty hefty 6oz+ copper traces, that does not seem safe to carry much current.