Charge from 6hp Tohatsu

Discussion in 'OnBoard Electronics & Controls' started by 23feet, Jun 19, 2015.

  1. BertKu
    Joined: May 2009
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    Location: South Africa Little Brak River

    BertKu Senior Member

    23Feet, like I have mentioned before, you have a technical fault in your generator. Diagram attached.

    Please , remove everything and keep only the 2 yellow wires. put a 12 Volt - 10 watt globe/lamp/bulb on those two yellow wires and start your engine, if it shines bright, when revving, you have a problem in the rectifier box.If it is not bright shining, you have a technical fault in the generator. Good Luck. Bert
     

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  2. 23feet
    Joined: Dec 2014
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    23feet Junior Member

    I will try both approaches when I get back to the boat (in a month).

     
  3. 23feet
    Joined: Dec 2014
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    23feet Junior Member

    OK - so finally wired the outboard to the battery with a 10 amp fuse.

    CDK seems to have nailed it. The battery was showing 12.3 volts before I started the outboard. The voltage went to 12.7 on starting and running unloaded at about half throttle. Running unloaded at about 3/4 throttle, the voltage went to 13. So, it seems to be working fine, but the amount of charge is modest.

    Roger
     
  4. BertKu
    Joined: May 2009
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    Location: South Africa Little Brak River

    BertKu Senior Member

    But that is fantastic for you. No technical fault. What do you mean with that the amount of charge is modest. It appears to be fine. If you have a 70 AH battery and you charge with an average of 35 Ampere, it takes you 2 hours from empty to full. In your case you started with 12.3, thus you battery was not empty and then it went to 13 Volt. What is normal. Most lead acid batteries do not go much over the 13 Volt.
    Bert
     
  5. 23feet
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    23feet Junior Member

    That's good to hear - thanks for your help.
    Roger
     
  6. BertKu
    Joined: May 2009
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    Location: South Africa Little Brak River

    BertKu Senior Member

    That was a pleasure, just to elaborate on lead acid batteries. Your gassing voltage at 25 degrees Celsius is 13.8 Volt. What it means, if your charger is giving you at open circuit: 14.4 Volt, to do fast charging, you have to ensure that it does not exceed 13.8 Volt when the battery gets full. Your water will vaporize and slowly your battery dries out, that would be a disaster, but you could still refill it with battery water and see whether you can revive the battery. For a Sealed Lead Acid battery it would drastic reduction in lifetime, as you will be unable to refill it with liquid. If you stay on 13 Volt, the last 5 % of your fully charged battery will just take longer, but want harm your battery. Bert
     
  7. 23feet
    Joined: Dec 2014
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    23feet Junior Member

    I will put a switch in the circuit so that I can turn it off when it is charged - although if the outboard is running, the autopilot is on, so perhaps unlikely to ever fully charge. It is charging two 30 amp/hour batteries in parallel.
     
  8. heikki
    Joined: Jun 2015
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    Location: Finland

    heikki Junior Member

    Recitifier/regulator

    Most likely the recitifier has a regulating function which limits max charging voltage to a safe level. If motor is run a longer period this could be noticed by measuring battery voltage which should not exceed above mentioned values. The regulating function also explains behavior without battery.
     
  9. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    Most of these small motors don't have regulators to limit voltage, mainly because the output is so low and they don't tend to be run for long periods of time where overcharging would be an issue. Since you have two batteries being charged the output is split, which even further reduces the chances of having an issue.

    If you are going to go to the trouble of installing a switch to stop the charging, why not just put in an after market voltage regulator, they are cheap and easy to install, this will elimate all potential issues. Altough thousands of small motors are used every day without regulators and it really doesn't create any problems.
     
  10. BertKu
    Joined: May 2009
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    Location: South Africa Little Brak River

    BertKu Senior Member

    Hi 23feet, I agree with Heikki, just let the generator run for some time and then measure it. As long the voltage is not over the 13.8 Volt, you are safe. You have a good change that after 4 hours running the voltage may have creeped up to just below 13.8 or even lower. Should that not be the case, then I agree with ondavr, put an inexpensive voltage regulator in, but caution, some of those regulators need a feedback from one of the alternator coils. Test it first for some time running, measure it and then come back to the forum and put your result to them. Bert
     
  11. 23feet
    Joined: Dec 2014
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    23feet Junior Member

    Thanks Folks,
    I greatly appreciate all of the help I have found here.
    Roger
     
  12. paul_ap
    Joined: Feb 2020
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    Location: Greece

    paul_ap New Member

    Hi all,
    Nice to meet you over here.
    It seems odd to be resurrecting this old thread but as my problems are similar and concern a 2018 Tohatsu 6hp Sail Pro, I thought it best to post here instead of starting a new thread. Long post follows, but I would appreciate your help.

    So, I bought this brilliant outboard last year, and it is equipped with a charging circuit. At first I did not use this capability at all. After a few months I decided to check whether the charging circuit lives up to its specifications (12 V 5A 60W).
    I stuck the multimeter probes on the leads exiting the outboard and got a reading of 6.7V at idle. Revving slightly up, I would get 8.5V. Revving further higher, the voltage would drop to less than 3V.

    I then connected the outboard to a battery (admittedly, a somewhat big one for its capabities - 77Ah), but observed absolutely no voltage increase no matter how much I would rev the engine up.

    It therefore seemed to me that the charging system was faulty. A while later I took it to the dealer and asked for them to check it out. Dealer concluded that the rectifier was blown and made it a point to prove that it was due to user error. Dealer's initial explanation was that I had actually connected the battery cable to the outboard, but left it leads unconnected, dangling around in the boat, where they would inevitably touch and short the charging circuit (!). After I told them that this certainly would not happen in my boat, the next version was that, while I had not actually connected any cable, the two small leads exiting the outboard should have been insulated with tape; if not, they may touch with each other or the engine chassis (even though they are actually insulated, and the chassis painted over there), and cause a short. I told them that (a) such a precaution is nowhere written in the manual, and (b) in any case, there is no electrical continuity between the leads themselves (as they are insulated), or the leads and the chassis. I took the multimeter out of my bag in resistance-buzzer mode to prove it on the spot.
    So the next version of events, because - as you understand - it simply had to be user error, after a telephone call with the official importer's tech dept, was that the outboard should not be started and operated without being connected to a battery, else damage to the charging circuit may occur.

    They pointed me out to page 23 of the manual, which, inter alia, reads under a CAUTION sign:
    1. Make sure that the battery leads do not get stuck between the outboard motor and boat when turning, etc.
    2. The starter motor may fail to operate if the leads are incorrectly connected.
    3. Be sure to correctly connect the (+) and (—) leads. If not, the charging system will be damaged.
    4. Do not disconnect the battery leads from battery while the engine is operating, the electrical parts could be damaged.
    5. Always use a fully charged battery
    I had always interpreted points (3) and (4) to mean that one should be careful against reverse polarity, and that certainly, one should not disconnect the battery from an already operating engine. However, it seemed to me that it would have been no problem for the engine to be started without a battery and keep operating without one. Certainly, there is no explicit warning against that, even though one, with a bit of imagination, could interpret point 3 to mean that the + and - leads must ALWAYS be connected.

    Anyway, at that point I conceded that it might have been user error indeed, and paid a discounted price for a replacement rectifier taken from a 15hp Tohatsu, and departed. I have not yet tested the new rectifier, but hope it works.
    But something in me was telling me that this cannot be technically correct.
    So, I wrote to Tohatsu USA and Tohatsu Japan. I am still waiting on Japan's answer, but Tohatsu USA responded that:
    I tend to agree with this response, but then again I am not sure.
    So...the 200 dollar questions are....
    1) did I indeed have a rectifier problem in the first place?
    2) can this outboard be safely operated without any battery connection?
     
  13. heikki
    Joined: Jun 2015
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    Location: Finland

    heikki Junior Member

    After installing the new rectifier you can do the same test which made you think the alternator is bad. If it still behaves the same the old rectifier was ok. What you told there is written in the documentation looks to me it is ok to use the outboard without battery connected.
     
  14. philSweet
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    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member


  15. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    I use the RadioShack rectifiers on small outboards frequently, they work well.
     
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