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12v power loss issue-gctid810361

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    12v power loss issue-gctid810361

    I know you guys are genius and this is probably something stupid but I've lost all 12v power and can't understand why.

    Last night lights looked a little dim and I checked charger and it had reset from when my friend turned of shorpower for 2 weeks by accident. Tried to use power today and there is nothing. Tried starting boat and nothing, no horn, pumps, not low or flat but dead. Charger is a new Sterling 12v-20a Pro Charge Ultra which should start boat even if batteries are flat. Have checked breaker on engine, is there anything else that could cause everything to be dead. I don't know of another fuse or breaker that could cause this.

    Boat is a 2855


    I would start simple by putting a volt meter on each battery. Assuming you have something over 12v I would then start tracing grounds. To be completely dead seems unusual, especially if you have more than one battery.

    In addition, some chargers will simply not charge a completely dead battery as they only start charging when they register a certain voltage (say over 10.5v for example).

    I am sure others with more experience and knowledge will chime in and they will want to know more detail, such as:

    How many batteries?

    Do you have a MBSS battery switch?

    Separate house bank?

    Good luck, wiring issues are always a fun challenge!


      90amp main fuse at the starter
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        Joon has your answer... Main breaker.

        With low batteries the current draw increases as the voltage drops. That amperage increase likely popped the breaker.


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          Thanks for the advice guys!

          So last night I had 12v and lights were slightly dim. This morning I checked charger and it was off so switched it on, realisticly everything was off overnight so there should have been no more drain on batteries (2 newish batteries, both were/are switched on). As I said I have checked breaker and that's fine. The only thing I haven't checked is the fuse at the starter. I had to replace this a few years ago when the alternator burnt out but by all accounts it takes some blowing but I will go and check.

          Just cannot understand what could have happened during the night.. Went to bed and it was fine, woke up and it was dead???


            Ok prolem solved and not at all what I would have expected. Here's the story for anyone interested.

            When I installed the new charger and batteries last year I made up new leads. The charger says to put online fuses on each output for the total ammount + 20% (20a + 4a = 24a, nearest 25a fuse). I slightly oversized everything for safety sake but what has happened is the springs in the fuse holders have heated up like elements and burnt out. It was only when I put a meter on everything and inspected the connections did I see the holders had melted on one side. It's strange how they have been fine for a year and suddenly ovenight burnt out but I'm thinking it might be this (and those in the know correct me if I'm wrong). New batteries and new charger for all this time have had to do little work so only on for brief periods to top up. After the charger had been turned off accidently and the batteries run down, once it was back on it was on continuous for a long period and caused the burnout. This is still not right and not good I know. and I will have to look into getting something with a stronger rating. The prtoblem getting larger holders was not being able to get small enough fuses.

            Anyway just thought I'd share that with anyone interested.


              I am glad you seem to have found the cause of the issue. Now, to make sure that all is well, you may want to do the following:

              1 - Be aware that totally draining your batteries will have shortened their life. Keep an eye on them regularly to see if they are perfectly able to hold their charge.

              2 - Go over and check to make sure that you have set the programming correctly, for the correct type of batteries used.

              3 - I would definitely install the temperature sensor; this would be connected to the negative lead of the warmest battery, i.e. the battery that usually is run down the most.

              4 - Be aware that if the batteries are switched ON during charging, some of the incoming charge current will also be going out to the load. This means charging the batteries shall take longer.

              5 - This next point is probably the reason why the springs became hot and malfunction occurred! If the batteries are completely empty when charging is started, they will take in the maximum current that the charger can supply and do so for a longer time. This means 20 amps (or more) current will pass through the fuse block (into the batteries) for a long time. Possibly made worse by any poor contact at the fuse holder, the resistance of the connection will cause heating, for a longer time. I am not sure what springs you are referring to but I would try to eliminate fuse holders that rely on spring pressure to pass 20 - 25 amps for long periods. Replace your fuse holders.

              Good luck.
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                MonteVista, thanks for the tips.

                1. Hopefully not too much damage as will be gutted, only about 10 months old. From meter they were run down to about 5.5v, not sure how much this would damage them and surprised this would stop all power, even horn or LEDs but it did.

                2. Reset charger and it's fine. Default setting is sealed lead acid and that's what it's always been on (that's what the batteries are).

                3.Temperature sensor is onstalled although I must check that it's connected to the negative as thought it said posotive.

                4. Boat is moored in marina so not a problem as shore power is on all the time. Only switch to single battery when staying overnight on the river to ensure full battery charge for starting.

                5. Agreed, and this is what I said. As the batteries had drained I think this was the first time a charge had been passed through the lead for a long period. The max the charger is supposed to be able to give is 20a. The leads/cables are slightly overrated and the fuses are as specefied, 25a. The holders were supposed to be rated at 30a but it was the springs that compress the fuses that let the unit down. Was thinking last night, and not sure if I'm right, but although the springs look much thicker than the fuse wire, I'm guessing it would make a difference if they were of cheaper metal offering more resistance?? Also could it make any difference as they are in a coil?? Just food for thought.

                Anyway have crimped ends together to bypass fuse holders for now and will have to go through the labourios task of trying to find an alternative. Ideally would like to put a midid in but they only start from 30a, do you think that would be ok?