Suitability of SAR v2 with LFP Batteries?

For all issues involving the Smart Alternator Regulators, V1, V2 and V3

Suitability of SAR v2 with LFP Batteries?

Postby jfry on Tue Mar 15, 2016 9:21 pm

I have a SAR v2 regulating a hot rated Amptech 125 amp alternator on a relatively small engine Beta Marine 14 hp diesel. I am looking into upgrading to LFP batteries and have some questions about the suitability of my SAR v2.

1. I would like to limit the maximum charging voltage for the LFPs to around 13.8 to 14 volts. Can an adjustment be made to limit max voltage to around 14 volts, or is the only options to use the “Locked at 13.8 volt mode”? Will the “Locked” voltage mode still use the soft start the alternator and use other charge steps such as adsorption and float? If so, what would be the absorption and float voltages?

2. With the small engine, I need to retain use of the Duty Cycle Current Limiting Mode function, and in this mode have the voltage to around 14 volts max. The 13.8 volts in Locked mode would be ideal. If I use the Locked Mode with 13.8 volts, will this also limit the voltage to 13.8 volts in the Duty Cycle Limited Mode?

3. Can any adjustments be made to limit max alternator amperage output in Locked Mode? (separate from the Duty Cycle Current Limiting Mode toggle switch?)

4. Can an alternator temp sensor be used with the SAR v2 to control/limit alternator output based on temperature?

5. Can the maximum battery temp be adjusted to optimize for LFP batteries?

6. Finally, how much heat is generated and airflow is needed for the SAR unit? It was previously located in the engine room above the engine. I would like to relocated it into a bin under the quarterberth where it will not be subjected to engine room heat, but it would have limited air flow in the new location. Is this advisable?

Thanks so much for help with these questions.
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Re: Suitability of SAR v2 with LFP Batteries?

Postby Coulomb on Mon Mar 21, 2016 12:46 pm

The SARV2 is a design from 20 years ago and probably not suitable for new technology batteries.
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Re: Suitability of SAR v2 with LFP Batteries?

Postby jfry on Sat Apr 02, 2016 12:02 pm

Well, actually LFP batteries do not seem to require a terribly complicated charge sequence. What works well is an alternator and voltage regulator that can pump out lots of amps until the batteries reach around 13.8 to 14.0 volts. Then instead of float charging, most experts seem to agree that it is best to shut down the charger until the LFP batteries need charging again.

The SAR v2 may be perfectly adequate for this, and have the benefit of the Duty Cycle Current Limiting Mode function and remote shut off function, which as I noted are important for the engine/alternator installation. The alternative, at least until the marine voltage regulator designers better catch up with LFP batteries in marine applications, is a Balmar voltage regulator but it does not easily provide for the three charging modes provided by the SAR v2: full amperage output within a voltage limit (for short engine run times), a user adjusted current limiting mode (for long engine run times or more power to the prop), and remote shutoff (for very long engine run times or full power needed to the prop).

My original questions should not be very difficult for someone knowledgeable about the SAR v2 to answer. Since Ample Technologies does not accept direct emails or phone calls, I would appreciate enough information to make an informed decision for my circumstances.
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Joined: Tue Mar 15, 2016 12:01 pm

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