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Dynastart - boiling battery

Posted: Sun Jul 23, 2017 10:14 am
by jocke76
Hi

Ever since we bought our Ballad, last year, there have been a bad smell when we're using the engine. Actually I hadn't made the connection about "when we're using the engine" until yesterday. We've always thought the smell came from the holding tank. So during the winter and spring I took out the tank and cleaned it, made a larger hole for ventilation, installed a air filter and connected a hose to the deck, so that we can empty it from there too and replaced all the hoses.

Yesterday we came home from a week long trip and on our way home the smell got worse and worse. Until the point where I started to become scared that something actually were wrong with the engine. So we stopped and drifter while I opened the engine compartment and checked everywhere. But the smell came from the v-birth. I opened the hatch to the batteries and the smell became worse and I found the source. The starter battery were boiling! It's a brand new 60Ah MultiMarine AGM battery (link in swedish below). I bought it just because of the recommendation of not having a larger battery due to the charging "mechanism" of the Dynastart. (Constant voltage and "floating" current depending on the battery's internal resistance and if you use a large battery the current could go above 11 amp and damage/break the dynastart or the charging relay. Please correct me if I got it wrong.)

Luckily the battery didn't catch fire or anything and nothing leaked, except smelly gases. We used one of our batteries from the "consumption" battery bank and connected as the starter battery. Then when the engine started, we disconnected that battery. The engine worked as expected but the electrical system in the boat behaved a little strange. Lamps flickering and one of the engine warning lamps lit now and then for just a second or two. But we made the trip of about 10nm home. The wind was only about 1-2m/s so sailing would have taken forever.

So, the questions is..
Is the dynastart-charging-relay broken/not working as expected?
Shouldn't I use a AGM-battery?


Battery:
https://www.hjertmans.se/produkter/el-b ... i-60ah-12v

Re: Dynastart - boiling battery

Posted: Fri Jul 28, 2017 10:20 am
by peterohman
The dynastart does obviously not work as expected when charging. I would disconnect the charging function to prevent it from breaking. How that is done can be found in "praktiska tips/elsystem" on balladklubben.se when you are logged in.
AGM is a good choice of batteries, but they are sensitive to overcharging so a malfunctioning charger kills them quickly.
/Peter

Re: Dynastart - boiling battery

Posted: Wed Aug 02, 2017 8:05 am
by jocke76
Hello again...

Thank you Peter!

I've tried to modify the installation to match the suggested changes, but with a "separation relay" (Skiljerelä in swedish).

But while trying to do the suggested fix I became more and more confused. :?
Somehow I, or the previous owner, had mixed to two positive cables so that the battery that I thought were the starter battery, actually was my "consumption" battery, and vice versa!

So when I connected, what I thought were the cables from the starter battery to the ac-generator, the other batteries were charged?!
After scratching my head for a couple of hours I realized that the cables were switched.. And I came to the conclusion that it wasn't the dynastart which were broken, it was the ac-generator!
Since we were going on an overnighter the next day I just disconnected the charger relay for the ac-generator and switched the cables so that the starter battery was charged from the dynastart.
While on motor I went down and measured the voltage a couple of times and the dynastart charged with a bit above 15V at about 5 knots, so we slowed down a bit and everything was fine. Atleast no boiling batteries!!

After posting my first post I ordered a new charger relay for the Dynastart, which I'm allowed to send back if that wasn't the error. But since the dynastart sometimes goes above 15V I'm thinking about keeping the new one. (I refitted the old relay since I came to the conclusion that it was the ac-generator that gave 16V+) Any suggestions on keeping it, since the dynastart delivers more than 14.x volts... ?

Re: Dynastart - boiling battery

Posted: Tue Sep 05, 2017 10:04 am
by patentnick
Hi Jocke:

When you say "AC generator" do you mean a battery charger that's connected to shore power?

Nicholas

Re: Dynastart - boiling battery

Posted: Tue Sep 05, 2017 10:45 am
by jocke76
No, the AC generator that is fitted to the engine.

I'm not sure if the ac generator is standard on all Ballads with MD6A, but mine has one.
I'ts mounted in the top right corner of the engine, when viewed from the front.

See this picture for reference. You see three belts in total. Two belts go to the Dynastart (with the green "wheel") and one belt goes to the grey/metallic ac generator. (This is a picture I found online and is not my engine)
img_0223_50a6678c9606ee20ddc054fd.jpg
img_0223_50a6678c9606ee20ddc054fd.jpg (109.89 KiB) Viewed 21147 times

Re: Dynastart - boiling battery

Posted: Tue Sep 05, 2017 11:43 am
by patentnick
Oh, OK. I'm not familiar with the old Volvos. My boat had been re-engined by the previous owner with a Sole Mini 26 which has a 40A Hitachi alternator.

As far as AGM batteries go, they aren't particularly sensitive to voltage as previously noted (GELs on the other hand are VERY sensitive). They can tolerate short periods of 14,8 V but are happier with 14,6 V (I've checked this with the manufacturers of my batteries). I have an Exide Maxxima 900DC AGM for the engine and two Whisper Power 145Ah AGMs for service.

I've found AGMs to be extremely reliable. Mine are entering their 7th year of service with no apparent loss in capacity. The one thing I've noticed with AGMs though is that they can absorb more amps from any given alternator than other batteries, which means that the alternator is working much harder. Unfortunately, most marine diesel alternators are essentially automotive units and may not be able to handle such loads for extended periods of time. This isn't such a great worry for me because my batteries are being kept topped up by solar panels and an MPPT regulator but, on occasion, when starting the engine following a prolonged period at anchor, I've noticed that my 40A alternator is forced to pump out 26-28A for an hour or so.

When money allows, I plan to replace the existing alternator with one from Balmar.

Nicholas