solgato avatar image
solgato asked

DC to DC converter

My next solar electric catamaran project will be built around a one person lightweight fiberglass hull and so in an effort to reduce weight and combat balance issues, I’m going to be using brushless ROV motors for propulsion instead of the heavy more powerful trolling motors I use for larger hull conversions.

The current motors available operate at 16-20V Max, but the company is developing larger thrust motors that I intend to upgrade to when they bring them to market later in the year. These larger motors will be designed to operate at 24-30V.

I’d like to build a battery pack that I can use for now with the smaller motors that will also support the larger ones when I upgrade to them.

So, in order to protect the smaller motors and their PWM controllers, I need to reduce the voltage of my battery pack.

Looking at the DC to DC Orion products, I see units that offer Voltage Output ranges but are limited in current. I’m worried that the in rush of these thruster motors when first throttled up might cause the DC to DC converter to misbehave. I’ve read that these motors could cause as much as a 60A spike for a split second.

Can anyone offer an advise on how the the converters might react?

I there a better product I should be looking at?

After the initial spike, the motors should operate within their normal Amp draw range based on throttle position.

I also intend to install a MPPT fed with 200-300Watts of solar and a BMV-712 for monitoring, which brings me to my second question:

It seems the smaller MPPT chargers are only able to work with 12/24V battery banks? Is it not possible to use them with a 30V bank, or do they just default to 24V and then you set you charge settings accordingly?


Orion DC-DC Converters not smart
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1 Answer
kai avatar image
kai answered ·

I would be hesitant to put a DC/DC converter in the power chain between the battery and the motor controller as a general principle, precisely because of the high current requirements. I would suggest revisiting the motor controller to see whether you can get one with a higher input voltage range. Or make your battery pack reconfigurable to that you can rewire as a higher voltage bank using same number of cells (e.g. 2S2P to 4S, or whatever combo that works).

Use a DC/DC converter for the auxiliary loads, not propulsion.

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solgato avatar image solgato commented ·

Thanks Kai.

Yes, agree it’s probably wise to just make the battery pack reconfigurable and not use a converter to limit the voltage.

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