# High Amp Situation for 10 seconds

Guys, my kids came up with some great stuff this year. One of the more intriguing items that they want needs some serious power. I have looked at the engineering for the motors, the PDP, the fuses and the main breaker and we are NEAR those ugly shaded red areas for the time we need which is 200A for 10 seconds. What I cannot find is anything on the BATTERY for this level of abuse.

Any insights on how many Amps can be pulled for 10-12 seconds?

Thanks!

Regular Andymark batteries are rated at 80amps continuous and 250amp Peak for ~5seconds

The 120 Amp main breaker is going to be an issue. In addition if you pull 200 amps your battery voltage will be near or at brown out. So calculations you do on power will need to be done in the neighborhood of 7.5 or 8 volts.

At 200a the main breaker will trip between 15 and 30s (https://datasheet.octopart.com/CB185-120-Cooper-datasheet-7688.pdf)

Also remember that the impedance of the battery will limit current delivery. I’ve used 0.03 ohms as a rough guess (and this includes a few feet of #6 wire for the main battery cable). At 200a you will see a 6v drop, so your power calculations done at 12v will be lower than expected (they will be 1/4 of expected). Because of this, you will not actually draw 200a, probably less than 120 due to voltage sag.

If your 200a does not include driving, I’d be very worried about it. If it includes some drivetrain related calculations, there’s a good chance that those calculations aren’t accurate/realistic enough and your actual current will be significantly lower. From my experience modeling drivetrains, it’s common for a rough calculation to show ~300a surge current, but because of voltage sag it rarely gets above 200 and only for a very short period of time.

Yes, I concur on the main breaker as that was the first thing I checked. We would be at 166% of the main breaker for 9.7 seconds which is well within the thermal limits. Then I went a looked at the fuses and we are at 125% of the fuse ratings for the same time period. There is NOTHING going on while this is needed and it is not DRIVE TRAIN related. It is a single 10 second event.

Is this for a level 3 climb, or do you want to keep it secret?

Not trying to keep it a secret but intelligent folks figure it out anyway! My students have given me ideas and I keep sending them more questions. To be totally honest, they very close to a workable solution!