So I've been scouring the boards here, MaineSail's site, and taking on board advice from a number of you regarding rewiring my "factory" battery and charging system. I'm learning a lot, and greatly appreciate everyone's willingness to educate others. This weekend I did a **rough** test to determine the usable Ah capacity of the batteries on my new-to-me boat of 9 mos ago. The results follow, and I'd be very interested in your thoughts.
Boat: 2009 Hunter 36 purchased in June 2018.
Batteries: 2 x 198Ah East Penn (West Marine branded) 4D AGM batteries of unknown age wired in manufacturer/dealer standard configuration (wired separately to 1, 2, Both, Off switch). Batteries in cockpit locker separated from engine. Since my purchase boat kept in slip w/shore power and batteries kept fully charged except for weekend overnights when engine charging used to replenish. Largest discharge event 69Ah in 2018 sailing season. Batteries run in “Both” configuration for duration of this test.
Monitor: Victron BMV-712 battery monitor wired through shunt.
Notes: Load varied between 3 and 10 Ah during test. Load overnight from 2308-0816 varied between 2-7 Ah, mostly on the lower end of that range. 3YM30 29hp engine is original with 398 hours on it, and the alternator appears to be stock and original. Belts changed and tensioned before test. Engine started for first time since winter layup and started on first crank from low battery charge state. Engine and alternator charging run for 10 minutes and shut down, at which time shore power ProMariner ProTech 1230iPlus 30 amp charger in AGM 2 setting engaged and run for ~50 min for final reading. Shore power charging continued after end of test to regain full charge and then maintain float charge.
ProMarine ProTech manual extract of charging profiles:
Observations:
- Batteries appear to have ~50% of original capacity available (400Ah bank; 200Ah usable capacity; 106Ah actual capacity to 50% SOC)
- Alternator appears to be putting out ~2/3 its rated capacity even when cold
Questions:
- Did I really run the batteries down to 50% SOC? If not, what should the ending voltage reading be at 50% SOC? (MaineSail writes in his www.marinehowto.com site of using a 12.1 @5.2 amps as cutoff for one of his tests to discharge a battery down to 50%)
- Is the observed alternator output normal for a cold 60 amp alternator (temp at engine start 50 deg F)?
Boat: 2009 Hunter 36 purchased in June 2018.
Batteries: 2 x 198Ah East Penn (West Marine branded) 4D AGM batteries of unknown age wired in manufacturer/dealer standard configuration (wired separately to 1, 2, Both, Off switch). Batteries in cockpit locker separated from engine. Since my purchase boat kept in slip w/shore power and batteries kept fully charged except for weekend overnights when engine charging used to replenish. Largest discharge event 69Ah in 2018 sailing season. Batteries run in “Both” configuration for duration of this test.
Monitor: Victron BMV-712 battery monitor wired through shunt.
Notes: Load varied between 3 and 10 Ah during test. Load overnight from 2308-0816 varied between 2-7 Ah, mostly on the lower end of that range. 3YM30 29hp engine is original with 398 hours on it, and the alternator appears to be stock and original. Belts changed and tensioned before test. Engine started for first time since winter layup and started on first crank from low battery charge state. Engine and alternator charging run for 10 minutes and shut down, at which time shore power ProMariner ProTech 1230iPlus 30 amp charger in AGM 2 setting engaged and run for ~50 min for final reading. Shore power charging continued after end of test to regain full charge and then maintain float charge.
ProMarine ProTech manual extract of charging profiles:
Observations:
- Batteries appear to have ~50% of original capacity available (400Ah bank; 200Ah usable capacity; 106Ah actual capacity to 50% SOC)
- Alternator appears to be putting out ~2/3 its rated capacity even when cold
Questions:
- Did I really run the batteries down to 50% SOC? If not, what should the ending voltage reading be at 50% SOC? (MaineSail writes in his www.marinehowto.com site of using a 12.1 @5.2 amps as cutoff for one of his tests to discharge a battery down to 50%)
- Is the observed alternator output normal for a cold 60 amp alternator (temp at engine start 50 deg F)?