Bavaria 40 emergency paralleling of batteries

[MagicalArmchair]

So on visiting Mirage to service the engine, I get the antifreeze ready to run through, and go to start the engine. The battery is dead! Okay, so I need a new battery, but what if I was at anchor? Is there a way of using the domestic batteries to start the engine if required?

[geoff]

I keep a jump lead in with the batteries to join the positives if my engine start fails. Never been used but reassuring to have. Geoff

[Symphony]

You can wire a switch to parallel the 2 banks or you can do what I did on my 37 of similar age and fit a BEP Marine switch cluster which has a built in VSR, separate switches for each bank and an emergency parallel switch. In reality, though if you buy a good quality new start battery you should get many years' life as it will get very little actual use just starting the engine and just rely on a pair of jump leads as geoff suggests.

[MagicalArmchair]

I visited the boat to service the engine and turned the power on when I arrived. Some eight hours later, after many little jobs, I was ready to turn the engine on to draw through the antifreeze - the engine battery was dead though! I discovered the ignition had been left on, so when I turned the master battery switch on it must have drained the battery over those eight hours through the ignition being left on. I now have a bucket of antifreeze in my boat, and none in the engine 😂👍. If only I had some jump leads on board - I tried the battery booster I have in my car that is supposed to be able to jump start cars - no luck using that though.

I’ll get some decent jump leads just in case and replace the battery. I was surprised the battery died in just eight hours of the ignition being on. Strange there is no buzzer - I might wire one in!

Thanks for the advice. Does anyone know how much juice the ignition on its own draws?

[Symphony]

Nothing that would drain a charged battery. There is nothing to draw current apart from the warning lights. The only significant current draw from the start battery are the glow plugs which have a button to activate and the starter motor. Everything else draws from the house bank. Pretty sure the start battery does not go through the master switch. Have you checked the voltage of the start battery? and also the connections. Do the warning lights and buzzer sound when you switch on the engine panel?

While the original factory wiring is simple and reliable it is worth changing to the switch cluster I suggested and fitting a battery monitor so that you have much better control over your system.

[MagicalArmchair]

Ahh that explains it then! Whilst it wouldn't have drawn much, it was left on for weeks whilst I was away from the boat if it wasn't tied to the main battery switch. It seems bonkers its not tied to the main battery switch though - what's to stop someone coming along and starting the boat without needing to go down below in that case?

I did have the power plugged in to the boat though, with the green light on the 240V panel that I assume means the boats on charge?

The voltage on the engine battery at the point I check after failing to start the engine was sub 10V 

[Symphony]

The mains charger is often only connected to the house bank. Not really necessary to have it charging the start battery as that rarely needs a shore charge. However some chargers do have more than one output so you may be able to connect it. I had that on the Synergex charger I fitted to my 37.

You may well find there is nothing wrong with your start battery that a shore charge won't cure.

[Fenders]

As others have mentioned, I carry jump leads.
When we bought our boat we knew the starter battery was a bit iffy as it had been checked by the surveyor.
On collection of the boat we took with us tools, etc and some jump leads. Just as well as we found the battery could only just engage the solenoid. Jumped the battery from the domestic one and away we went.
Needless to say a new battery was our first “must buy”.
Still carry the leads but not been used since.

[Odysseus]

Please remember dumping a fully charged battery into a flat one through a switch runs a severe risk of wrecking the good battery by distorting  the plates.

Odysseus

[Salty]

.....................and go to start the engine. The battery is dead! Okay,............Is there a way of using the domestic batteries to start the engine if required?

Here is a diagram showing a simple switching arrangement I fitted to my boat to allow such switching for an emergency starting of the engine. This system was requested by the coding surveyor at a time when my boat was coded for charter. Points to keep in mind are for the new wires to match the cable thicknesses of the existing wires, and that the new switch is capable of carrying the starting load. Also, as soon as the engine is running I would suggest switching off the emergency start switch. In addition and to ensure that use of the emergency start was not turned on by mistake, I separated the switch key from the switch, and screwed the switch key to the under side of the battery locker lid. That way it’s use was only by a deliberated choice to do so rather than an automatic choice of switching everything on and forgetting about it until it was time to walk ashore, assuming they even remembered to switch things off then !!!

Nb. Some existing cables have been omitted from the drawing for clarity.

[Rampage]

I’ve fitted exactly the same setup as Salty.  Never actually had to use it yet but it’s there if needed.  Good tip on the switch key: going to do the same when I get out to the boat.

[Yngmar]

Our boat has the battery combiner switch Salty describes and we've used it once when we had a fault that caused the engine battery to be no longer charged, resulting in a low battery. Worked brilliantly. Switched it off as soon as the engine was on.

When replacing our faulty VSR, I've noticed the new Victron VSR (Cyrix I think) has an optional feature where you can use the VSR to bridge batteries on demand by pushing a small (thin wire diameter) button. This saves you one set of thick wires if you already have a VSR anyways, and it will automatically separate them again, so no chance to forget.

[Craig]

Guys,

Is it really worth the effort to spend time, money and effort to install a switch to connect the house batteries to the starter battery.
1. It costs money.
2. It is another part that can fail.
3. It is easy to leave Ön".
4. I'd rather be sailing than working with my head down and my bum up in a tight work space.

A set of Jumper Leads from any Car accessories shop anywhere in the world at a cost of less than 10 pounds, 12 euros or $15 would work just as well and not prone to failure.

I have just had my second Starter Battery fail in 10 years. Both times used the jumper leads to start the engine to get me out of trouble. No worries.

Craig
"Shirley Valentine"
Gold Coast
Australia

[Symphony]

Less than £20 for a switch and cables and an hour or less to fit. Nothing to fail. Only ever used in an emergency so difficult to see how it can be left on - and even if it is no harm done. Salty has already suggested a routine for ensuring you don't leave it on. While it is easy to use jump leads in boats where the two banks are in the same location, but on my 33 the start battery is at the bottom of the cockpit locker and the house bank is under the port saloon seat so jump leads are simply impractical.

[MagicalArmchair]

Thanks all, that's really useful stuff. I especially like the inclusion of the booze locker... now I'll definitely fit one of those...

[Salty]

Thanks all, that's really useful stuff. I especially like the inclusion of the booze locker... now I'll definitely fit one of those...

Your welcome MA, and the booze locker came as standard on my B36(2002).

Craig, I see your point, but I didn’t have a set of jump leads that I could leave onboard so I would have had to buy some, so that cost could be offset against the cost of the fixed system.

Yes, the system could fail, but properly put together cables with hydraulically crimped on ends are very reliable, and so too in my experience have been battery switches. I have seen some jumper leads where the springs for the crocodile clamps on the ends have been rather fragile. That aside, as the boat had to be coded for charter, there was no option on whether I had a permanently fitted solution for a dead starter battery. If it wasn’t fitted the surveyor would not have signed off the coding survey.

It’s easy to leave on -  that was the one thing that had me worried, so I deliberately made it a difficult choice for charterers to switch on in the first place, in that they would have to unscrew the key first before it could be put into the switch. It was unfortunate that charterers usually knew how to switch things on, but switching them off when not in use................sigh !!

You’d rather be out sailing, me too, but sometimes when the weather is below average, though you may be able to find other words beginning with B and A !!  On those occasions, and during the winter lay up, I do also enjoy finding things to do onboard whether it be maintenance or an improvement (hopefully) or two.

But whatever, it’s your choice what you do on your boat, so all you have to do now is remember where you last left those jumper leads.
My system is fixed in place where it’s not going to be mislaid and its not going to be buried under a pile of other yachty stuff in the back end of some locker.