-77 error on 96v Lithium setup

Hey Everyone,
I did a 96v lithium swap last year from @lithiumgods and everything has been working great but I was never able to fully figure out the -77 error code that occurs when the batteries are fully charged. I either have to stop the charging before the batteries get to 96.75v or if it goes over I have to keep the head lights on until the voltage drops to 96.75v, (which can take forever). I was hoping that someone could shed some light on what I might be able to do to be able to fully charge the batteries without having this error Occur. I bought the Sentry software, so I am able to make adjustments to the controller if needed. Wasn’t sure if a more aggressive spoof would help or maybe adjusting function 14 and 15 to higher voltage would work. Cart is a 2002, E4 with a T2, 350 amp controller. Thank you for any help.

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Some of this forum details pushing the limits of components beyond normal design limits.
From what I have seen there seems to be a 50/50 chance a T2 will handle voltages higher than 96v. Some just don’t like going that high and produce questionable and confusing results.

In your case it is actually a proper error -
-77 Capacitor (1C) voltage too high during motoring.
This status code will be displayed when the voltage at 1C exceeds 96 volts during motoring.

I personally have not seen a T2 that can handle voltage above 96v.
Your spoof is on Pin1 and that make the T2 see less than 86v on that pin and will allow the car to run.
However there is something in the T2 that does not allow it to function above 96v period. We have not been able to find a way around this limitation.

I have been out of the loop for awhile so maybe someone else has found a way.

Hey guys, I’m not trying to be argumentative but I have been driving this setup for a year and it’s definitely 96v with a T2 controller.

We aren’t saying it’s a specific number. Only that its about 4v less than t4 which we run at 99 volts.
And thats the reason we recommend a 22 or 23 cell limit.
You posted about a problem. That’s the answer. :slight_smile:
Spoof is not for -77 run error. Spoof is only used to allow starting.

Gotcha. Ok, well that kinda stinks. Thanks for the help. It drives great and is super quick but I was just hoping to be able to fully charge the batteries.

Dave we have dozens of T2 Gems running @96v. maybe one out of 10 fault with that voltage. A rebuild from flight systems has fixed them every time. Your T2 is going over 96v to 96.75v which is fine. All you have to do is limit it to 96v(4v per cell) and your good. 4.0v to 4.05v is target range. For longevity cells shouldn’t be charged higher than that…Simple parameter change in the bms will do it. T4 and 5 will go a few volts higher but we limit them to 97v, 96v for a T2 is great.

For reference, it is recommended to operate an NMC lithium cell between 10-90% SOC. On a Samsung sdi cell that is 3.49v-4.01v. According to battery university limiting max charge voltage to 4.0v instead 4.1v doubles the battery life.

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