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Starting Battery Issues

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Category: Hints and Tips
Forum Name: 415/418
Forum Description: 415/418 Hints, Tips and News
Printed Date: 12 April 2021 at 17:52
Software Version: Web Wiz Forums 12.01 -

Topic: Starting Battery Issues
Posted By: Nethermead
Subject: Starting Battery Issues
Date Posted: 13 January 2021 at 16:30
I just bought a 2017 Hanse 415 in September, and I am about to replace the starting battery for the second time.

As far as I can tell, something is draining the starting battery while the boat sits, and then the charging system over-charges it to the point that it heats up and the walls of the battery swell.

When I went to take delivery of the boat in September, the batteries were dead. It seems that perhaps the broker or surveyor left the engine panel on for about a month. I connected the boat to shore power, and everything seemed to work fine, so I set sail. But when I went to restart the engine a day later, I discovered that the starting battery was dead and had actually started to split in half, probably from overcharging. I am pretty sure I made the rookie mistake of starting the engine while connected to shore power, not realizing the battery had already been ruined. Or maybe the alternator overcharged the battery while motoring. Not sure. I replaced the engine battery.

I then left the boat hauled out for two months, not plugged into shore power. The house bank was fine, but the new engine battery was down to 4.5 volts when I returned. I recharged it with shore power, and it started fine. When I drew down the house bank a little and plugged the boat back into shore power, I noticed that the starting battery was extremely hot and could be heard "sizzling." The charger was hitting it with 14.4 volts, even though it hadn't been used to start the engine recently. I'm guessing the battery had been damaged while sitting at 4.5 volts for two months.

I am about to install a new starting battery, but I wanted to see if anyone had any idea why mine keep getting ruined. It seems like a brand new battery should have been able to sit for a couple of months without discharging so deeply and getting ruined. (The house banks sat an equal amount of time and were fine.) It makes me wonder if there is some phantom draw from the boat that is discharging the starting battery.

I am also trying to understand if the WhisperPower battery combiner installed on the boat may be to blame. As I understand it, it is supposed to combine the banks at certain voltages. I looked at the manual and don't understand if it is wired to charge the starting battery first and then combine the banks to charge the house bank or vice versa.

Thanks for any thoughts anyone can share.

Posted By: High Time
Date Posted: 15 January 2021 at 12:04
When you leave the boat for any length of time do you turn off the engine battery? If you do, and it is still discharging, you can rule out all circuits beyond the battery switch.

If you don't turn it off, the quick fix may be to turn it off and see if it still discharges.

If it discharges even when the battery switch is off, then the only item connected is the combiner, through a 125A fuse. I have a Sterling combiner so can't comment on the Whisper Power item, except to say the combiner is usually wired to give priority to the engine battery.

To do a proper check you need a simple multimeter (less than £10 from Amazon), ideally with a 10A current range. You can then disconnect various circuits, working back from the battery and inserting the meter, on the 10A range, in series with the disconnected circuit.

You will also need the latest wiring diagrams to see what is connected.

If the wiring diagrams do not make any sense to you (they are not the easiest to follow), then it maybe time to ask an electrician, or an engineer friend, to take a look.

Good luck.


High Time (415 #038)

Posted By: Nethermead
Date Posted: 15 January 2021 at 13:01
Thanks for your thoughts. I will definitely try checking any current draw off of the new starting battery once it's installed. 

One question that comes to mind is whether the battery charger is connected correctly as designed. The Mastervolt charger that came with the boat has outputs for two separate battery banks, but the way Hanse wired the boat seems to be to only utilize one charger output. I believe it charges the starting battery first, and when that reaches a certain voltage, the combiner relay closes, and the house bank is connected and begins charging as well.

The issue I see with that is that the Mastervolt battery temperature probes are only on the house batteries. So theoretically, when it's first charging the starting battery, it's sensing cold (house) batteries, even though the full charge current is being directed to the small starting battery. I don't know how the temperature input affects the charge voltage, but I'm guessing it leaves it in the bulk phase longer than it ought to since it thinks the battery is cold, when really it's very hot.

Posted By: Fendant
Date Posted: 15 January 2021 at 14:15
just some additional comments on the leads given by Roger.
I assume that you have the original batteries from 2017, AGM's as house and starter battery.
You observation of 4.5 V at the starter battery clearly points to a damaged AGM. The smell of "Amperetrioxide" of your overheated battery is another clear hint. 4 Years lifetime in nice climate like Georgia sound normal.
AGM's have a "sudden death" behaviour, meaning that the voltage is fine after charging, maybe one start. I had the same experience with my service bank, 14.0 Volt after disconnecting shore power, then falling to 13.6 Volt after 2- 3 hours and then sudden death to below 11 V.
If you have the starter battery above the engine, I suggest that you have some new longer cabling made.
Exchanging will be much much easier, although you miss learning some new dirty words from the mechanic.
The VSR ( voltage sensitive relay ) couples starter and service battery when charging > 14 Volt. When charging is discontinued it separates starter and house batteries, so you don't drain the starter battery with your ice maker :)


Posted By: Nethermead
Date Posted: 15 January 2021 at 14:25
Thanks, Frank. I purchased this latest starting battery last September, so it seemed strange that it failed so quickly. I am going to investigate phantom draws from the boat.

That is interesting about AGMs holding a charge temporarily and then quickly dying. The information is much appreciated!

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