Outboard motor battery charger control
rporter
Registered Users Posts: 8 ✭✭
The motor is a 6hp Tohatsu with what they refer to as an 6amp 'alternator' but in reality it's a magneto coil and rectifier. The battery is a 12v approx. 75ah deep cycle battery. I've tested the output and the rectifier correctly limits the voltage output to around 14v as the engine speed increases.
This is on a sailboat. The problem is if I motor for several hours or all day, there is nothing limiting the amps being pumped into the battery. It's all about a year old and I'm afraid I have already started to damage the battery.
The boat also has a 100w solar panel that is connected to a Morningstar SunSaver controller. Typically not connected when the motor is on. That works fine at controlling the charge from the panel. I contacted Morningstar to see if the outboard charger could be connected to the SunSaver to control the charging and was told definitely not. The two systems can be connected in parallel after the charger but not before.
I have looked quite a bit and have not found any small device that
will act as a controller to cut the charging from the outboard when the battery is fully
charged.
Any help or suggestions will be appreciated.
Comments
-
6 amps ought to be safe for any flooded 12v 75ah battery, regulated to 14V. That's about what is seen in a car on a long trip.
I don't see a viable way to be damaging the battery from even 6 hours daily running.Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister , -
A car of course has a regulator that stops charging the battery when it's full.Let's say it's putting out 4 amps for 6 hours, that is 24ah. During the day while motoring the only load is a speed/depth instrument that draws 0.1a. Seems that it could be easily overcharged.After a two week trip the electrolyte level was very low (I didn't think to check it during the trip) prompting me to think it had been over charged while I motored all day for two or three days and the fluid had boiled off. The battery doesn't charge up to the same level as previous. It used to be 12.85 when fully charged. Now it's 12.62.
-
When the battery is full, it should take very little current at 14v, maybe an amp or two, but not six.
How warm/hot was the battery? Was it full when you measured the 14v limit?Off-grid.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter -
What would reduce the amperage going into the battery? The charger keeps pumping out 4 to 6 amps. It doesn't know anything about the state of the battery. It only limits it's output to 14v.I think the battery was full. I measured it prior to going out one day before I installed a permanent voltmeter so typically the battery is fully charged. I didn't check the temperature of the battery. I can read the voltage to two decimals so I can see what the voltage is while the engine is running and at the speed that I usually motor it's around 13.5v.
-
The battery itself should limit current when full, or nearly so. The charger doesn't push out amperage, it pushes voltage. The "flow" of amps depends on loads, like opening a tap. At 14v (assuming that is actually limited), a properly functioning 12v nominal lead battery near fully charged is like an almost closed tap. At a given water pressure (voltage), there's a limit to flow (amps).
Off-grid.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter -
If that is so how are batteries overcharged?
-
Batteries are overcharged by applying a voltage higher than what's recommended, this will induce current to flow into the battery, being that it can no longer store any more energy, assuming its fully charged, the energy generates heat which consumes the electrolyte and damages the plate material. So if the maximum voltage is regulated to a value less than or equal to the battery’s required voltage, it cannot theoretically overcharge if in good condition.1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding. -
> I've tested the output and the rectifier correctly limits the voltage output
Rectifiers don't limit voltage and I suspect that this is all this engine has (the limited capacity of the coil and the battery itself provides some regulation). If so, then yes, there would be some advantage to adding a voltage regulator (a shunt regulator is common).
Also note that a typical charging voltage (say 14.4V) will eventually overcharge a battery. This is why a float voltage (say 13.3V) is used in more sophisticated charging systems.
https://www.tohatsuoutboardparts.com/Electrical-Kits.html
I am available for custom hardware/firmware development
Categories
- All Categories
- 220 Forum & Website
- 128 Solar Forum News and Announcements
- 1.3K Solar News, Reviews, & Product Announcements
- 189 Solar Information links & sources, event announcements
- 886 Solar Product Reviews & Opinions
- 254 Solar Skeptics, Hype, & Scams Corner
- 22.3K Solar Electric Power, Wind Power & Balance of System
- 3.5K General Solar Power Topics
- 6.7K Solar Beginners Corner
- 1K PV Installers Forum - NEC, Wiring, Installation
- 2K Advanced Solar Electric Technical Forum
- 5.5K Off Grid Solar & Battery Systems
- 424 Caravan, Recreational Vehicle, and Marine Power Systems
- 1.1K Grid Tie and Grid Interactive Systems
- 651 Solar Water Pumping
- 815 Wind Power Generation
- 621 Energy Use & Conservation
- 606 Discussion Forums/Café
- 300 In the Weeds--Member's Choice
- 74 Construction
- 124 New Battery Technologies
- 108 Old Battery Tech Discussions
- 3.8K Solar News - Automatic Feed
- 3.8K Solar Energy News RSS Feed