Move start battery to engine bay

[gregcope]

Hi all

Wondering what wiring needs to change if I want to move a start battery to the engine compartment. This would free up space for a third domestic. Battery bank is presently under the saloon seats.

If I understand this correctly; A new positive from the battery to the no.1 master switch. A new ground to the engine?

Is a battery likely to be damaged in a warm engine bay?

Anyone done this and care to comment?

Thanks.

 

[vyv_cox]

You simply need to transfer the positive lead from the old starter battery to its new position, assuming you had separate starter and domestic banks previously. You will need to provide a new earth connection to the engine, or wherever the existing one is connected.

I have had Red Flash batteries in the engine tunnel next to the gearbox for several years now. The original one, shown in the photo, was too small, now replaced by a Red Flash 1100. It works well and seems to cope fine with the temperature.

 

[gregcope]

Thanks Vyv. Looks neat and glad to hear the temp is ok.

Moving my present positive lead will be a challenge as it goes through loads of conduit etc.... Was thinking re-using it to parallel up the domestic bank.

But come to think of it, I could cut the cable and move it as you suggest.

 

[Plevier]

In a typical yacht engine compartment with a small engine used intermittently, temperature is unlikely to be a problem in reality, certainly in UK.
However as a general rule a rise in temp of 10 deg C doubles the rate of a chemical reaction and this includes corrosion in batteries. Corrosion is likely to be the life limiter for a starter battery.
You hear stories of batteries failing very quickly in constant temps of 40 deg in mobo engine rooms.

 

[vyv_cox]

In a typical yacht engine compartment with a small engine used intermittently, temperature is unlikely to be a problem in reality, certainly in UK.
However as a general rule a rise in temp of 10 deg C doubles the rate of a chemical reaction and this includes corrosion in batteries. Corrosion is likely to be the life limiter for a starter battery.
You hear stories of batteries failing very quickly in constant temps of 40 deg in mobo engine rooms.

I know of one owner, occasional poster here, who has had a Red Flash battery for starting a 4-cylinder Yanmar engine in the bilge beneath it for the past 10 years. The boat is in the Eastern Mediterranean.

We sometimes see temperatures of almost 40C in the saloon, so I guess the engine compartment might be a good deal warmer than this. Despite that my first battery was still OK after three years and the present one seems as new after two. Where does the corrosion occur?

 

[ghostlymoron]

Sounds like your cabling will be shorter with the battery in engine space which will be good.I'm

 

[Plevier]

On the grids, both corroding them away and affecting the interface with the paste. Also sometimes if not well sealed, the spot welds linking the cells together through the divisons in the case.
The batteries DMS badged as Red Flash used to be an unusual construction of very thin stamped plates of virtually pure lead, not the normal calcium or antimony alloy. They would be more resistant. I don't know what DMS are labelling as Red Flash now though, it's a long time ago that I was involved.
Don't forget the battery has lots of thermal inertia and is pretty well insulated internally (being an AGM type with no convection currents in the electrolyte) so won't follow quick temperature variations.
In the bilge sounds the best place. The sea won't be at 40C even in the med!
10 years is very good going. However if capacity checked I'm sure it would be well down. A quick start takes negligible capacity - if it takes 10 seconds at 200A - that's 0.5Ah. A nearly knackered (in capacity terms) battery can easily do that if it's conduction paths are not too corroded away and so the internal resistance is OK.

 

[peteK]

The battery is in engine compartment in a car.

 

[Plevier]

The battery is in engine compartment in a car.

True but does your boat engine room have a 70mph draught through it?
In most cars now the battery is quite well separated from the engine block, usually in an insulating box or at least a screen, often with ducted ventilation and even in some exotics, cooling.
It is a problem that is specifically addressed.

 

[Mandarin331]

True but does your boat engine room have a 70mph draught through it?
.

True, but then I wonder how car batteries survive in hot countries, like Dubai. Ours it right in front of the engine, exactly where the builders designed it to be and I suspect most starter batteries are close to the engine to reduce the cable lengths.

 

[Deleted member 36384]

I have read on other websites that batteries (domestic) should not be located in the engine bay as the heat will lead to a shorter life. I would assume that this is true for engine starter batteries but that the effect would be less noticeable as the battery is only used for short periods.

 

[pyrojames]

True, but then I wonder how car batteries survive in hot countries, like Dubai. Ours it right in front of the engine, exactly where the builders designed it to be and I suspect most starter batteries are close to the engine to reduce the cable lengths.

Many car batteries are now located in the boot, rather than the engine bay these days. Those that I have encountered in engine bays are at the front, so unaffected by engine bay heat during driving.

 

[reeac]

My Jag. Xj8 has the battery in the boot and that battery is coming up to 14 years old and has never needed charging from an external source despite only averaging 3000 miles a year. I sometimes wonder whether that's due to its location.

 

[Plevier]

True, but then I wonder how car batteries survive in hot countries, like Dubai.

They expire quicker than in cool countries.
Partly offset by having an easier job to do.
Heat does the damage - cold exposes it as battery output drops while starting current demand increases.

 

[PaulRainbow]

A car engine battery is nothing like a small, enclosed engine compartment on a yacht. A car engine bay has a big hole in the front of it, lots of smaller holes in various places. Air is driven in through the big hole, or blown in by powerful fans. These days, almost all batteries that are in engine compartments (which is still the most common place for them, although some are in the boot or in the passenger compartment) are enclosed by covers or insulated jackets. Maybe to shield them from heat but just as likely to protect them from cold. Cold finishes more batteries off than heat in this country.

 

[Lon nan Gruagach]

[headless chicken mode]

Ohh, doom and gloom and exploding boats.

[/headless chicken mode]

Err, just suppose there is a hydrogen build up when the starter solenoid kicks. Ideally batteries should be treated alsmost as carefully as lpg cylinders. Although the big plus is that hydrogen (should it get past the catalyst) floats up and out rather than pooling.

 

[PaulRainbow]

[headless chicken mode]

Ohh, doom and gloom and exploding boats.

[/headless chicken mode]

Err, just suppose there is a hydrogen build up when the starter solenoid kicks. Ideally batteries should be treated alsmost as carefully as lpg cylinders. Although the big plus is that hydrogen (should it get past the catalyst) floats up and out rather than pooling.

I have had first hand experience of igniting the hydrogen from a battery that had been on fast charge for a while. They do make a rather large bang !!

 

[Daydream believer]

I have had first hand experience of igniting the hydrogen from a battery that had been on fast charge for a while. They do make a rather large bang !!

As a teenager I was leaning over a battery on the floor & disconnecting a charger when I knocked a steel ladle that shorted across the poles. The battery exploded & blew acid in my face. As i ran from the shed screaming my mother grabbed me & rammed my face in the washing up bowl of water in the sink. She then turned me round & turned the tap full on flooding my face to wash the acid away & gave me a black eye where she caught me with the tap. !!!
After a visit to A & E I spent 3 days with my eyes bandaged & soon found what sort of problem blind people have to go through.
On the last day my mother took me to hospital & holding my arm walked me up some steps - which she warned me about.
She then said, " Here are a pair of doors" walked through the open one & marched me straight into the closed one giving me a nosebleed to go with it.
So the moral is - exploding batteries give you a nose bleed & a black eye & your mother will tell you to stop behaving like a nancy boy !!! & it hurts !!!!

 

[NormanS]

My battery boxes are connected to an (FLP) suction fan, so that if starting the engine after charging from shore power, any hydrogen can be removed. In practice, I never use it because I only ever have shore power when ashore in the winter, but the idea makes sense. Yes, the batteries are in the engine compartment.