Timer on battery charger?

[Deleted User YDKXO]

Somebody has told me that it is not a good idea to leave batteries on charge connected to shorepower for weeks on end because eventually it fries them and has suggested that the battery charger on my boat be fitted with a timer such that the batteries are only on charge a couple of hours per day. But I thought battery chargers had regulators which reduced the charging amperage according to battery voltage status anyway so why do I need a timer?
What does the learned panel think?

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[longjohnsilver]

I think you should fill a few suitcases with extremely large, heavy batteries and fly out immediately!

Think you are right, they fully charge the batteries and then change to float mode. The only problem is if the charger malfunctions, could then damage the batteries, but only a small risk of that eventuality.

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[Talbot]

Whilst LJS is correct as far as proper marine step chargers are concerned, if your chargers are the cheaper automotive sort, then they will just keep charging until they fry the battery (and will still not have achieved as much charge as a proper marine charger)

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[Mollari]

You can buy a decent switch mode type charger from Marine Superstore (port solent) for about £160. I believe they do mail order, as a Marine electrician I would recommend this charger and have used it for many clients.

http:\\mysite.freeserve.com/leisure_marine_elec

PLUG PLUG PLUG

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[tcm]

hah panel, geddit?

ahem, anyway i fink it will have a timery thing which makes sure it doesnae fry the battery. Otherwise everyone would have fried batteries, thousands of them. Decent azimut pretty sure will have one of these and alistairr's boat does too.

You can check that this is wot happens by turning off everything on the 12v side and listening in the engineroom and there'll be a bzzzz sound which is the charger. But then it goes off. Then wham on a load of lights and the bzz starts again soon enough. ok, this is a bit sad but at least you know what is going on.

Axshully, i left the shore power unconnecteried this time. Cos after all, batteries in decent nick, no lights on, boat not leaknig so why leavit connected?

of course you have to check the battery levels with the Special Water.



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[halcyon]

It's a yes and no situation, if you leave a battery on float charge ( 13.6 volt ) for extended periods it does kill batteries. The idea of float charge comes from stand-by batteries which are maintained by charging at 13.6 volt, but periodically they must go through a full charge cycle ( ie upto around 14.6 volt ) to maintain there life. The other issue is that float charge is only maintaining the battery, so you are running the charger for 24 hours a day for no gain, and avoiding a very small loss. The best solution we came up with was a battery charger with a sleep mode, this would turn it's self off when you were not using power, but turned it's self on to give the battery a pulse charge. The length of pulse and period between them was based on the charge state of the battery, resulting in a full battery being on charge for 1 minute in the hour. We also made a little unit that did the same for a standard battery, fitting inline with the mains supply, and monitoring the battery volts.
But to cut a long story short, if you leaving the boat for long periods, fit the timer, and set it for a hour a day, saves 23 hours electric. Also as the charger will go through a full cycle, you could maintain a better battery level as a bonus.

Brian

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[Deleted User YDKXO]

Look, we're talking Italians here so what battery charger you get probably depends on how good a lunch old Giuseppe from Stores had and whether Juve won the night before. Actually one thing I've learnt today is that you boil batteries not fry them but I think I prefer my batteries marinaded in garlic and lightly grilled

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[Deleted User YDKXO]

Thanks, Halcyon, thats useful

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[terryw]

I was told that batteries work better/last longer if they are constantly being cycled. You can achieve this by leaving a light on, or as I do by keeping the cockpit fridge on 12v (also means cold beer always available), and leaving the charger on 24/7.

Terry

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[rog]

Provided your charger's got enough power, which i think most have, doesn't this just result in the charger powering the fridge when required with sufficient charger capacity left over to continue to trickle feed the batteries 24/7, which isn't any different to the problems already described?

I was also thinking about possibility of adding a timer but was considering wiring it into the 240v line from shorepower so that it'd also prevent some of the galvanic effects that mains power is said to cause. Was thinking of an in-line timer suitable for outside use, normally leaving it inside cockpit - but bit unsure as to real practicalities - and that's if i can source a suitable timer, of course.

I've also got a fridge constantly running, so gotta make sure the time on charge is sufficient to make up the power taken by the fridge - guess it'll not be a scientific calculation as fridge requirements change with weather and charger output rate will vary with battery voltage? May suck it and see

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[boatone]

Hang on chaps.......

.....I'm a little bemused by all this.
Presumably you all have alternators that recharge your batteries when under way?
I almost never use shore power except when overnighting in a marina.

My battery capacity has been beefed up to give me enough useable power for up to 48 hours before needing to recharge which is approximately 100 AmpHours for my normal useage which includes a fridge. It only takes a few hours of running to return this to the batteries. (I have three 108A/H batteries parallelled to provide domestic power so I am only using the 100A/H or so that lies between 85% and 50% charge level).

So can somebody enlighten me? Why the need to leave the batteries charging all the time when you are not there?

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[PhilF]

Re: Hang on chaps.......

I also have 3 100 amp batteries for domestic and another for starting, all pretty new.
If I leave my EDC's on for 2 weeks the starter battery runs down and wont start the engines.
If I leave the fridge on battery power the domestics run down in a week.
The reason they leave their chargers on is to stop the batteries dying when they leave their 12volt fridges on - I think.
Me I leave the shore power on and chargers off and burn up anodes by the score.

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[boatone]

Re: Hang on chaps.......

For my enlightenment......

a) dont have any experience of EDC's.....but why do you leave them on if you are not there and should they drain current if they are not actually active?

b) why leave a fridge running if you are not on board?

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[PhilF]

Re: Hang on chaps.......

1. Good Question. Company that fitted them didnt fit isolators and the Baterries went down. Morse said get them to fit isolators on both battery banks and now its okay. Was just illustrating how easilly batteries drain.

2. I know you are joking

Philf

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[Deleted User YDKXO]

Re: Hang on chaps.......

Agree with PhilF. We like to leave the fridge on whilst we are away to save it from defrosting and depositing all its water over the galley floor. The second reason is that, in the event of water ingress, the bilge pumps may have to operate for long periods and this will also discharge the batteries

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[boatone]

Re: Hang on chaps.......

Still a bit puzzled by all this fridge business.

We run our boat almost every weekend and for at least two or three longer periods during the season. Routine is to leave fridge off and door open when not on board and switch on as soon as we arrive. Yes, that means it takes a while to cool down but we take cold stuff down in a cool box and its quite safe in there until fridge is ready for it. Theres even room for a few cold beers if thats a critical issue. We dont leave any foodstuffs in the fridge when we're not there, taking anything left home in the coolbox.

Dont think we've ever had to defrost the fridge cos our way it never runs for such long periods that this becomes a problem.

As regards the possible emergency running of bilge pumps thats another issue. As a matter of interest, I wonder how many boats are fitted with float switches and left with batteries on continuous shore power support for this reason?

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[Deleted User YDKXO]

Re: Hang on chaps.......

Well I guess the bilge pumps are the main reason why boats are left on continuous shore power, certainly is for me. We tend to leave longer life food in the fridge and freezer for the next trip as well as beer. There's nothing worse than having to drink warm beer after struggling to get to the boat

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[duncan]

Re: Hang on chaps.......

tough one that - which is really worse ; warm beer or no beer?

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[Deleted User YDKXO]

Re: Hang on chaps.......

Mmm, difficult one

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[jfm]

this fridge business

We always leave fridges on, and we leave shorepower connected for that reason and to power bilge pumps if disaster struck.

I can't see point in turning fridges off. Can leave some food in there fore next visit. I mean you dont turn your home fridge off when you go to stay a few nights on the boat (do you?)

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