Batteries, sorry another question

[saltyrob]

Hi

Have checked our two existing batteries one of which has died and needs replacing. Both are heavy duty 664 type , one serves to start the engine and the other is for domestics, 105 and 110 ha respectively, both at least 7 seasons old. From a quick check on internet appears that 664 type is a cranking battery.Would it be advisable to purchase a 664 type for engine cranking and a dual purpose leisure/stating type for the domestics.Thought is that dual role domestic battery could be back up to cranking battery in an emergency. Would charging the two different types off the alternator cause any problems.We are on a swing mooring and use a low tech charger on trickle charge when visiting marinas.Boat is 86 vintage so havent got modern electric installation.Been adviced that both batteries should be replaced to avoid weaker one drawing current off the newer one /forums/images/graemlins/confused.gif

Many thanks,

Rob,( novice battery purchaser)

 

[VicS]

A leisure battery would perhaps be a better choice for the domestics but only marginally so.

I hope your two batteries are connected via a 1,2, both, off switch or better still have separate isolators.

Start with just the starter battery switched in, when that's recharged switch over to the domestic battery.

Remember that if the engine is running you must switch via "both" never completely disconnect the batteries from the alternator while it is running or you will very probably fry the diodes.

The two are of such similar size that provided they are of the same type then they can be charged in parallel but it would be better to adopt the procedure above and charge one then the other. (for this purpose a leisure battery is the same type as a starter battery)

Or get more complex with a VSR to split the charging.

 

[simonfraser]

if they are 7 years old, and you are away from an 'easy fix' i'd replace both before you are left swinging without power.

 

[saltyrob]

Hi
Will be replacing batteries for pease of mind.I though a cranking battery was unsuitable for domestic duties , however seven years service appears pretty good to me. Are there any advantages of having dual purpose batteries which can both crank the engine and serve the domestics.

Rob

 

[saltyrob]

Hi

At two in morning had another thought,Numax offer both sealed and ordinary marine batteries, are there any advantages with either type.

Rob (insomniac battery purchaser)

 

[Cliveshep]

My old boat has 3 standard 110 AH truck batteries, two linked as auxilliary and one for cranking. Every other year I push them all over fitting a new one as starting battery, one falls off the end and I dump that or if it appears still good give it away. That way I've got essentially 3 batteries capable of starting the engine as I've discovered that no matter how hard I push/pull I can't "bump start" the boat if I come down after a few months absence and want to run it and the battery is flat.

However, I do have one distinct advantage peculiar to my old engine perhaps, and that is I have two alternators, one for start and one for auxilliary and that is a real bonus.

 

[blackbeard]

I once attended a talk given by Sea Start in which it was recommended that batteries be changed after 4 years, after this they are unreliable. (Although the battery in my car typically lasts 5 or 6 and arguably has a harder life.)

It seems logical that the engine start battery should be one designed to give the current needed to start engines (ie car type) and the domestic one should be designed to give more charge/discharge cycles (although no battery likes being completely discharged). A reasonably large and beefy "leisure" type battery normally seems to have enough power to start the engine in emergency if required.

I can't see the logic of charging one battery before charging the other, unless one of the batteries is well discharged; normally the alternator will give 14 volts or more provided batteries are reasonably well charged and in this case, if both batteries are connected, neither will discharge. Can anyone tell me otherwise?

And. I'm still a little annoyed at having to change a battery, used for engine starting, after 3 1/2 years. Always kept well charged, but now completely shot and destined for the battery section of our local council dump. Maybe it was in the shop too long before I bought it?

 

[brianhumber]

My boat is 87 with 80amp alternator so I would guess is similar in the KISS stakes as yours.
Whilst a lot of what has been written is in theory correct, in practice I simply buy cheap cranking batteries. Normally start the engine AND run domestics on one and keep other for emergencies. When domestic use one shows signs of loosing its ability to retain charge I buy a new one, use that as the new emergency and the old emergency then becomes the normal starting and domestic.
Batteries last 5/6 years this way on a mooring with fairly regular use.

The rule ido not allow the one on domestic duties to be discharged as cranking batteries do not last long otherwise and Nigel Calder would be driven mad by the lack of technology and simplicity of my electrics. Biggest load would be the fridge for the Gin and Tonic but I put ice bags in my fridge this allows 3/4 days channel cruising between marina charger top ups or running the engine

So advice is go cheap and simple and watch your battery monitor.



Brian

 

[Stemar]

My starting battery - ~50 AH is now getting on for 5 years old and was part of a set swapped out of an ambulance, so it had had a pretty hard life before that. My domestic battery is an 85 AH liesure battery that was the only one on the boat when I bought her 6 years ago. The only "sophistication" is a split charge relay fed off the lead from the charge warning light to the alternator. As soon as the alternator starts producing volts, it links the batteries and they can fight over the charge, but in the nature of things, the flatter of the two takes the lion's share until both are evened up a bit.

I know there are all sorts of reasons why the system shouldn't work and should kill off my batteries in short order, but they don't seem to have realised it, so they just get on with the job, just like the batteries in a million cars & caravans.

There are al sorts of opinions about why AGM and all the other fancy batteries are ther best thing since well before sliced bread/ a complete waste of money, but my limited experience leads me towards the latter opinion, at least for coastal cruising.

 

[Channel Sailor]

For UK coastal weekend and annual holiday crusiers, I would recommend cheap simple marine badged batteries (wet, not sealed). NUMAX is one that I have used a few times. Plus go for something slighty larger if you can for the domestic, because it is the frequency of deeper cycling that wears them out. 4-5 years would be a good life time for those that want 30% - 50% discharge often. Sealed batteries have a place in mulithulls, and deep cycle batteries of course have a use for very regular domestic usage. I tried the light weight batteries once, they seems just the same to me as ordinary leisure batteries. I like to have wet batteries so I can check the specific gravities at least in the winter. No nasty surprises with failed batteries then.