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High Voltage on SARV3 system

PostPosted: Wed Jun 17, 2009 1:36 am
by Ian
I have had a customer come to me with a SARV3-12V problem. The installation has been in place for 2 years and has worked very well. Just recently it has been lifting up to 14.8 volts, from 14.1 volts. He has Gel batteries and has it on East Penn dip switch setting. There is no fault light coming up. When the temp sensor is disconnected, the voltage comes back down to 14.1 volts. He replaced the temp sensor but it didn't change anything. It is a bother to him because the inverter trips out at 14.6 volts. What ideas do you have for me?

Re: High Voltage on SARV3 system

PostPosted: Wed Jun 17, 2009 10:25 am
by Coulomb
The Ample Power Primer has a chart for battery temperature compensation. It is pretty general but is still useful in this situation. See:

Changing the temperature sensor didn't help because the regulator is doing what it was designed to do - raise the voltage when the batteries are cold.

There are some ways to deal with the problem:
1. Disconnect the temperature sensor and kill the batteries from undercharge;
2. Warm up the batteries;
3. Change the inverter setpoint to a more realistic value; or
4. Don't use the inverter when the voltage gets above its setpoint.

The first customer of an Ample Power diesel battery charger installed it in a home in the mountains east of Seattle. In the summer the temperature gets into the 90s, (35C), and in the winter, well below freezing. His batteries lasted 18 years.

Re: High Voltage on SARV3 system

PostPosted: Mon Jul 06, 2009 2:12 pm
by Barry Clark
I am the electrician Ian referred to as his customer. When I first investigated this complaint, I advised my customer (the boat owner) in accordance with the exact points you have now listed. The boat owner's argument (because he is reluctant to replace the cheap inverter), is that he didn't have this issue for the first 2 years after the Ample Power regulator was installed.

I did not see the "reported fault" when I first checked the system, after which the boat owner reports that he had no further problems for 2 months. I informed the owner before Ian contacted you, that I expected exactly the reply that you gave. He still doesn't want to accept this, so I will suggest to him that we temporarily fit another Ample Power SARV3 regulator. If there is no change in the way the 2nd regulator operates, we have proved our point. If there is a change, he can choose to purchase the replacement regulator. Either way, it should put an end to the complaint from this customer.

Re: High Voltage on SARV3 system

PostPosted: Mon Jul 06, 2009 4:27 pm
by Coulomb
Probably for the first two years the batteries never got so cold, or maybe the inverter has shifted the trip point for alarm. Replacing the regulator won't prove anything unless you can duplicate the cold batteries.

You can demonstrate the effect of temperature quite easily. Remove the temp. sensor from the battery and, while monitoring battery voltage, immerse the sensor in a cup of ice water. Watch the voltage go up. Now remove the sensor from the ice water and apply a little heat from a lighter. Watch the voltage decrease.