Apollo AV-1 motor heat generation problem with lithium battery

[sh_underwater]

The AV1 had a 17 AH battery so it would usually be fully discharged before it overheated. I have been through this, there is
nothing to absorb the heat from the motor. I surrounded the motor with aluminum heat sink but it didn't help much, just a few extra minutes, no place for the heat to go. Air doesn't absorb much and the case is a good insulator. I transferred the parts from a ruined AV2 to add the cooling plate and gear housing and that helped, but it still wouldn't run full speed continuous without overheating. Ultimately I just went for the AV2. They will run full speed continuously.

I heard that the motor was not cooled sufficiently even when using the AV-2 aluminum gear case and cooling plate. Is it in the state of propeller pitch 1?
I was interested in the AV-2 cooling system, but Apollo didn't sell the part to me.
So I decided to drill a hole in the AV-1's motor compartment and use aluminum and copper materials to create a system that indirectly cools the motor with seawater.

 

[sh_underwater]

Ha ha ha ha ha but before you start drilling holes in it man ha ha ha ha ha!

Hmm?
I have three AV-1, so it doesn't matter if the modification fails and the AV-1 breaks.

 

[happy-diver]

Lucky boy, as long as you have two left, one for spares

You must show us what you will use for through fittings

Now it becomes "very interesting"

 

[Jona Silverstein]

The AV1/SV900 does not like being overvolted. the problem with the larger packs is the voltage sag is less allowing more current to pass through the motor. I built a 4s Li-ion pack for one and while it went really fast when the prop was at full pitch, it would overheat after about 20 minutes. To mitigate this, you can drop the pitch of the prop down to reduce the load on the motor or you can use a lower voltage pack. switching to a 3s Li-ion pack worked well for me but still cannot run at full pitch for an entire dive.

 

[sh_underwater]

The AV1/SV900 does not like being overvolted. the problem with the larger packs is the voltage sag is less allowing more current to pass through the motor. I built a 4s Li-ion pack for one and while it went really fast when the prop was at full pitch, it would overheat after about 20 minutes. To mitigate this, you can drop the pitch of the prop down to reduce the load on the motor or you can use a lower voltage pack. switching to a 3s Li-ion pack worked well for me but still cannot run at full pitch for an entire dive.

My battery is a lifepo4 battery so it's not overvoltage. It is 14.4v with 3.6v 4 cells.

 

[sh_underwater]

For the time being, I made such a modification. All parts are made of copper and aluminum. An indirect cooling system that uses seawater.

 

[rjack321]

My battery is a lifepo4 battery so it's not overvoltage. It is 14.4v with 3.6v 4 cells.

Read what @Jona Silverstein said again
Li-ion don't have a voltage sag under load like the stock SLA. So the voltage says high at full pitch and thrust. So compared to the stock battery you are running at a higher than "normal" voltage in actual use.

 

[Gone for diving]

Lithium iron max charge on a 4 pack is 14.4V, (3.6v per cell)
but that is not nominal voltage.... 3.2v per cell X 4 cells is 12.8V.... on use it drops to 3.2 v relatively fast and holds the voltage... anything below 3v, capacity drops fast...

 

[happy-diver]

How did you seal the through fittings man!

 

[rjack321]

Lithium iron max charge on a 4 pack is 14.4V, (3.6v per cell)
but that is not nominal voltage.... 3.2v per cell X 4 cells is 12.8V.... on use it drops to 3.2 v relatively fast and holds the voltage... anything below 3v, capacity drops fast...

This is incorrect
Max charge for li-ion is 4.2V per cell. a 4S pack is 16.8V and despite the ~15amp load is not likely to drop below 15V when fully charged - which is way higher than an single SLA battery. Which is exactly what Jona was explaining above.