Charging the House Battery Bank with a Small Outboard
- Thread starter O’Day 222
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All of these replies are 100%
The cheap charger in a tohatsu 6hp only puts out its peak rating at a throttle which is higher than what you need to make a 22ft sailboat hit hull speed in normal conditions.
After 1 season I stopped bothering connection the tohatsu charger wires. Pointless for charging a lead acid group 24 battery, nevermind a lithium bank.
The rate 5 A 12 VDC output is PEAK output. You won't see that most of the time unless you run at way more throttle than needed.
I suspect one of those old wheel mounted generators they had on bicycles in the 60s would be as effective.
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The tohatsu 6 hp and sailpro has a rectifier as stated by the original post.
I used to have a Tohatsu 6 sailpro. Wonderful little kicker. The charger was "semi-smart" in that it would not show any voltage with a voltmeter unless it detected a load. Not sure how that worked ... but when I hooked the leads to a dead battery and tested the voltage, I got closer to mid 13V levels.
Funny.... but the multimeter serves to close the circuit even without the load present. Presumably with a very high resistance and minimal current but it is still a closed circuit. Although we pretend otherwise, the act of measuring a circuit creates a parallel alternative route for the flow of electricity. The internal resistance of the multimeter is set at a very high level relative to the circuit being tested so that the error is negligible. BUT, the multimeter would not work at all unless some current passed through the meter.
I don't remember now. I took the motor back to the dealer thinking the alternator was not working. He put it in a tank and hooked the leads to a dead battery and then we measured the voltage. He then told me that the alternator does not put out unless it detects a load... So there must be some way it detects current flow and if there is no current, it shuts off. I don't understand how that works. I'm guessing it is a safty thing in case a lead comes loose. (?!)
I had the same set up with a Honda 9.9 that I used to own.
I had the same set up with a Honda 9.9 that I used to own.
Aw, come on. You're taking all the fun out of an online forum.Time to ask Tohatsu support, instead of speculating
While the discussion of how a small outboard engine alternator may or may not work is helpful, it still doesn't reflect the fact that a lithium battery bank should not be charged by an unregulated alternator.
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Aww come on... Let's do it and see what happens.
Its both really... The tohatsu 6hp DC output is practically useless.. so the discussion of using it for charging a lithium bank is moot.
.. and you shouldn't charge a lithium battery with anything but a charge controller meant for lithium.
Outboard = solar. Unless you run the engine all day and full rpms, not enough to amount to anything. at actual rpms, probably 30w for 1 hour = 2.5 Ah perday, vs. 40 Ah for a 100W panel. Little more than a rounding error. In fact, 40 Ah per day, plus a small battery deficit, should be enough for a 22-foot boat. Recharge at marinas.
As requested here are the pics. It needs a bit of adjustment as it was put back up to simply get it out of the way (the yard typically requires me to take it off for haulout). This was made by cutting a bimini bow in half. I added some dyneema (highlighted in blue) because I found that the stern rail assembly was racking quite a bit. the other end is attached to a car on the spinnaker T track. I waited a few weeks to replace the dyneema at the beginning of the season and the stern rail mounting bases ended up a bit bent. My outboard and inboard are connected to the inboard's fuel tank. The solar wiring enters the hull at the same spot. With different hardware it would be possible to route the wiring through the half bimini supports. Zip ties work for now. The angle of the panel is adjustable and I do plan on cutting off the excess aluminum angle. This setup can also be turned around so the panel is above the cockpit
I'd also suggest looking into the Great Loop Cruisers' Association. It looks like an incredible resource and a great group of people
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Great! Thank you very much!
Very nice install.
What make and model boat is this?
How many watts of solar do you have?
I’ve been a member of the AGLCA for some time.
Thanks Again!
Rod
It's a '78 O'Day 25. I have one Renogy 100w panel. It charges a a dead FLA battery in less than one summer day in Chicago
