Motor goes out on overload

[WayneWoody]

Our high school team entered a solar powered boat in the Sacramento Municipal Utility District's (SMUD) Solar Regatta Friday, May 3rd. Two 230W solar panels powered a 24V brushed DC motor to drive the 15 foot piloted, wooden boat. We used an EP Ever 30A solar charge controller. After a few minutes on full power the solar charge controller shut the motor down and displayed an "overload, Load short circuit" error. The EP Ever manual said it would go out if the load current exceeded 100%. The manual also said the power would be restored. The time to restoration was based on the size of the overload.
How does the solar charge controller know the rated amperage of the motor? Is it based on the battery data we input into the solar charge controller? We used two 12V, 7A batteries. Contest rules limited the battery pack to 180W. Would the overload error go away if I set the amps to the amp rating of the motor (350W/24V=15.5A)?
Thanks in advance for any clues to our problem.
W W

 

[sunshine_eggo]

Our high school team entered a solar powered boat in the Sacramento Municipal Utility District's (SMUD) Solar Regatta Friday, May 3rd. Two 230W solar panels powered a 24V brushed DC motor to drive the 15 foot piloted, wooden boat. We used an EP Ever 30A solar charge controller.

A few things...

230W * 2 / 24V = 19.2A maximum yield from the sun in PERFECT conditions (not flat on a boat). You're probably lucky to get 15A-ish peak, and that's only at high noon. Less before and after.

After a few minutes on full power the solar charge controller shut the motor down and displayed an "overload, Load short circuit" error.

If you are using the load ports of the EPEVER to power the motor, those load ports have a current limit. I you exceed that, it will overload. In You would normally connect the motor directly to the battery.

The EP Ever manual said it would go out if the load current exceeded 100%. The manual also said the power would be restored. The time to restoration was based on the size of the overload.

Again, if connected to load ports, motor should be directly connected to the battery.

How does the solar charge controller know the rated amperage of the motor?

It doesn't. It probably saw a load that exceeds its rating, so it cut power.

Is it based on the battery data we input into the solar charge controller? We used two 12V, 7A batteries. Contest rules limited the battery pack to 180W.

You mean 180Wh.

Would the overload error go away if I set the amps to the amp rating of the motor (350W/24V=15.5A)?

No. You should connect the motor to the batteries.

The batteries are what powers the motor. The charge controller charges the battery.

IMHO, you will not be able to continuously sustain max power for very long. You likely need to monitor the MPPT output and try to match your motor load to that incoming amperage. 7Ah isn't much of a buffer. Alternatively, you could probably simplify the process by picking a target voltage of 24-24.4V and vary throttle to maintain it.

 

[seneysolar]

Interesting contest!

Are the panels required to be in fixed position? Having them tilted up and on some kind of turntable, pointed at the sun as you go would certainly optimize production.

My high school was definitely not this creative...