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Alan Shedd asked

Want to control 2 parallel Orion TR 12/12-18s by alternator temperature

Want to control charging rate of house battery and avoid alternator overload.

Upgrading energy storage on cruising sailboat. I plan to use existing 80-amp alternator to charge AGM starter battery and use 2 parallel Orion TR 12/12-18's to charge 200 AH lithium-ion house battery. Engine key switch will enable both Orions, would like to use temperature sensor on alternator and relay to switch second Orion on/off. While 80-Amp alternator can deliver 50 Amps at cruising rpm with hot alternator, I don't want to "cook" it with extended operation at high temperature. Should be able to power both Orions and charge house bank at 36 Amps, then reduce alternator load to 18 Amps when alternator gets hot. I see Cerbo GX has temperature input and relay function - perhaps can be configured to stop 2nd Orion when alternator temperature reaches elevated setpoint. (Too bad Cerbo doesn't communicate with Orion thru VE.Direct.)

Any thoughts, comments, experience with similar control schemes?

Alternative approach of using high-capacity alternator with smart external regulator (Balmar MC-618) to charge house bank directly is more complicated / expensive to implement.

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kevgermany answered ·

Look at the Orion on/off options using the L and H terminals in the manual. This will allow you to use the Cerbo to control one or both Orions. But... How are you going to get the alternator temperature in the Cerbo?

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Alan Shedd answered ·

Victron sells a temperature sensor for the Cerbo:

Victron Energy ASS000001000 temp sensor for Quattro, MultiPlus and Cerbo GX

i would connect the rig terminal sensor end to a bolt (+ terminal) on the alternator. The sensor connects to one of 4 temperature inputs on the Cerbo. From there it should be easy to set the relay to open at my max temperature setpoint. However then max temperature of teh sensor may be too low.

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kevgermany avatar image kevgermany ♦♦ commented ·

That sensor is intended for battery use and is connected to the battery negative terminal, not positive.

How to get the alternator temp is tricky. You need to temp of the windings, or to be able to infer it, then have a max safe working specification. Then match the sensor values to temps and only then can you work on the logic.

There's a product from Wakespeed that controls the alternator. I think WS500. If you look at Victron's YouTube channel there's a video there about how to prevent overloading the alternator. But I seem to remember that they use the Balmar solution which you say is too expensive.

Perhaps a larger alternator is the best way to solve this.


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pwfarnell avatar image pwfarnell commented ·

You could use that temperature sensor bolted to the case of the alternator (not the + terminal as @kevgermany says. You would need to have the set point around 85-90degC, much lower than the winding temperature. The temperature sensor should be on the rear of the case near the diodes as this is usually a hot area. The external alternator regulators such as the Wakespeed WS500 bolt the temperature sensor to the case and control to around 90degC. The relay function in the Cerbo will accept temperatures up to 100degC so setting the relay switch point to around 90degC leaves a bit of headroom to set an alarm in case the relay does not work. If you have ever read about the Apollo 13 failure, never have your switch setting at the maximum reading value. An infra red thermometer is also useful then in cross checking the winding vs case temperature.

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