To add or not to add a spare battery?

[bbilly]

I have a motor boat (OMBRINE 700) with only 1 battery. I do not intend to add services (fridge....) at the moment but my concern is if I get stuck with a flat battery. My reasoning is that the diesel inboard has a relatively low risk of breaking down on me if maintained correctly. If this does happen the chances are this will be fuel problems and as such something I can probably fix. However if I have a flat battery I am stranded. Adding a second battery is an alternative but it seems quite a task as no provision is made and this implies drilling holes and mounting battery boxes, switches, wiring, optmizing the charger and all the related issues. My current line of thinking is bending towards assuring that the single starting battery is always in serviceable condition. Can anybody advise me on what I need to do or know to be 100% sure that my battery is ALWAYS able to start my engine. Secondly is an automatic battery isolator a good idea to shut off the battery if services (lights, CD player) risk flattening my single battery. Or - should I fit a second battery for emergencies.

Thanks in advance for any suggestions insight.

Bill

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[Rohorn]

Hi......if you look back over the last few days the battery question has been argued over ad nauseum. I posted "many small batteries?", and others, in order to get some informed opinions, and generated an avalanche, for which I was very grateful.
I sense from what you say that your installation can evolve further fairly soon. (Mine also is being rehashed from scratch) Well you can spend a packet on various goodies as you progressively ameliorate your system, but for now, just to be safe, and NOT spend a packet till you're ready, get a new sealed maintenance free battery, one of these new ones with calcium separators which self- discharge only very slowly (Delphis for ex.) Find one the same size and configuration as your existing one, so it will exchange easily.. Check it's well charged up, then stash it safely in a convenient locker and leave it there till you need it....it'll be ok for some months...should be ok in there for a whole season. Check it occasionally if you like. It'll always be useful later anyway when you're thinking of a second bank and looking at diodes and voltage sensing relays, battery management systems, smart alternators, exotic battery types, solar panels and windmills... ...
Denny Desouter, the first editor of PBO no less recommended this about 20 years ago when such batteries first became available.
Cheers.....R

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[StephenW]

Another alternative is to always have onboard one of those jump-starter battery packs - you can also get them with a built-in invertor for short term use of 240 volt drills etc.

As long as you keep it charged (by taking home for example) it should always be able to get you out of trouble. Best to check for a good capacity to ensure maximum reserve

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[halcyon]

If fitting one of these batteries in the locker, check carefully on how it should be charged, may need different charge voltage. As R say's they appeared 20 years ago, at the time Westerly started fitting them (AC Delco freedom ) we were suppling panels and charging systems to them. The new batteries caused that many problems with lack of charge, little capacity, that I spent 2 months research on them, and we found out that they needed a extra volt to charge them ie 15.2, against 14.2, without it the electrolyte was not mixed. It worked on a car because the vibration of the car mixed it, new cars in stock had new batteries fitted as the old ones were dead from standing in stock yard. Another problem found was that if the batteries were left over winter 50% dischargered, it had a memory, thus a 100 amphour became a 50 amphour battery. New batteries can have new, or in some cases old poblems, everyone is the altimate design, until the next one arrives, check spec carefully.

Can you fit two smaller batteries, or one larger and a smaller one ie 60amphour and a 40 amphour, Fit cd etc to the small one, engine to the big one, you the have a good reserve for starting, and at worst a flat small battery and no CD !!. Then all you need is a small split charge relay between the two batteries ( should have isolattor switches so fit relay between them ). Use cheap liesure type batteries and you are as bomb proof as you can be.


Brian



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[William_H]

You will be caught with a failed battery eventually. Batteries in cars are lucky to last 4 years. You need an alternative battery for additional start power when your battery gets tired. It is sensible to set it up to use for services so that you don't have to be concerned about using lights CD etc. Suggest then a voltage sensing relay to connect the new battery to be charged when the engine is running . Use a jumper lead or dedicated switch to paralell the batteries when you need the extra start power but don't be tempted to always start on 2 batteries as you will then never know if the engibne start battery is gegtting tired.Yes you will need to fit a box of some sort to hold the new battery which can be almost any sort you choose. Regards will

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