High voltage threat to 12v motors on lithiums?

mikedunix63 · Thursday at 11:30 AM

My furnace motor seems to have burned out early. (3 years, not a lot of use) I have been warned that the higher voltage from lithium batteries can cause problems for a motor expecting 12 volts. I have looked at voltage regulators, but the ones I found drop the voltage to 11.4 with a 6 amp (my furnace motor) load. Which is worse for the motor? 13.4v or 11.4v?
Any suggestions for a voltage regulator that maintains 12v through the load range?
Thanks for any advice.

efficientPV · Thursday at 11:45 AM

What kind of furnace is this? 12V and burning out is likely brushed and warnings like this are usually the result of a poor motor to begin with. 14.5V is considered to be in the normal voltage range of 12V systems. Two diodes in series would be the easiest way to drop the motor voltage 1.5V. Switching regulators with this tight a differential likely don't have that good of efficiency anyway. In moving air, higher voltage creates higher speed and that creates significantly increased current. If possible, mount diodes in airflow.

mikedunix63 · 2024-07-19T20:30:00-0700

Thanks for the feedback. It is a suburban sfv-35qa. I understand that most of the 12v components are ok with higher voltage, but some motors redcan be picky. I am not sure what it means to add diodes, so I will do some research.

efficientPV · 2024-07-20T04:49:35-0700

Generic silicon diodes drop the voltage about .7V regardless of current. That is called the forward voltage and it can vary from 0.2V to 1V depending on diode type. The other option is a speed regulator instead of a voltage regulator.

Zwy · 2024-07-20T05:40:35-0700

mikedunix63 said:
My furnace motor seems to have burned out early. (3 years, not a lot of use) I have been warned that the higher voltage from lithium batteries can cause problems for a motor expecting 12 volts. I have looked at voltage regulators, but the ones I found drop the voltage to 11.4 with a 6 amp (my furnace motor) load. Which is worse for the motor? 13.4v or 11.4v?
Any suggestions for a voltage regulator that maintains 12v through the load range?
Thanks for any advice.

I'm assuming a 12V motor in a camper furnace. This has nothing to do with the battery chemistry. Think of it this way, if you are plugged into shore power and using a lead acid battery, the AC to DC converter will be charging the battery putting out up to 14.6V on the 12V system or maintaining the battery at around 13.4V.

Lower voltage kills motors. It could be you have system voltage sag already or a connection problem/resistance in the circuit.

Quattrohead · 2024-07-20T09:50:13-0700

I'm thinking it's more about the quality of the motor than the voltage.

Brett V · 2024-07-20T10:25:26-0700

That motor was going to fail regardless of the battery chemistry you used.

areoseek · 2024-07-20T10:31:40-0700

As others have said, purely coincidence. That is well within normal operating range for 12 volt appliances, think of when the alternator or generator is running and charging the batteries, that's the same voltage.

mikedunix63 · 2024-07-20T21:09:40-0700

Zwy said:
I'm assuming a 12V motor in a camper furnace. This has nothing to do with the battery chemistry. Think of it this way, if you are plugged into shore power and using a lead acid battery, the AC to DC converter will be charging the battery putting out up to 14.6V on the 12V system or maintaining the battery at around 13.4V.

Lower voltage kills motors. It could be you have system voltage sag already or a connection problem/resistance in the circuit.

I've never heard of lead acid charging near 14v. Lead acid converters charge much slower and with lower voltage than lithium converters. Any way, I guess I will just not worry about it, and hope the new motor lasts longer than the original. It is complicated to replace.

mikedunix63 · 2024-07-20T21:18:36-0700

Thanks for all the feedback. Feel free to delete this thread. I don't think it will help anybody.

High voltage threat to 12v motors on lithiums?

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