Battery management

[Barry777]

I'm looking to buy a decent battery management system for my 38 footer. Currently have 3 batteries; one 95 AH for the engine and two 135AH in parallel for the domestics. I have the ususal cabin and external lights; plus radar, Auto7000 and Garmin colour chartplotter.

I use the boat most weekends, but am too mean to pay the extra for electricirty when visiting marinas overnight. My berth is in Chichester Harbour so the engine is used regularly to get to and from - about an hour or so each trip.

A friend mentioned one manufactured by Link, but I haven't found any website information. Any recommendations would be grateful.



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[tome]

Try Merlin Equipment, Unit 1, Hithercroft Court, Lupton Road, Wallingford, Oxon OX10 9BT, UK. Tel: +44 (0)1491 824333; Fax: +44 (0)1491 824466

Regards
Tom

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[dickh]

Also try Adverc<A target="_blank" HREF=http://www.adverc.com>http://www.adverc.com</A> - very helpful to deal with.

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I'd rather be sailing... /forums/images/icons/smile.gif

 

[pvb]

Step-by-step...

Best to approach this one step at a time. In order of priority:-

First, get a "smart" alternator regulator (eg Adverc, Sterling, etc) to maximise the charge efficiency.

Second, increase domestic battery bank capacity. It would make things a lot easier for you if you doubled the size of the bank.

Third, get a Link 10 battery monitor (also sold as E-Meter) to show you exactly what's happening with your batteries. You can get full info on the Link 10 from the <A target="_blank" HREF=http://www.xantrex.com/products/product.asp?did=199>Xantrex website</A>, and can also download a user manual if you want to read more.

Both Adverc and Merlin are very helpful companies.

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[Talbot]

Re: Step-by-step...

You advocate doubling his present domestic battery bank from 2x135 AH This would mean 540 AH. Did you really mean this? What size domestic battery bank do people recommend The weight penalty will be quite large as will cost, wouldnt it be more cost effective to add a wind generator or a couple of solar panels?

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[pvb]

Big battery banks...

Good question, and yes I really meant it. After a smart regulator, increasing the battery bank size is probably the most cost-effective enhancement you can make to a cruising boat's electrical system.

Weight penalty is negligible in terms of the boat's overall displacement. Cost is maybe £250-300 including wiring, tie-down straps, etc, which is less than half the price of a wind generator. But there's a big benefit in terms of performance and battery life.

Batteries - even "deep cycle" varieties - don't much like being discharged. It's best not to discharge a battery by more than 30-40% regularly if you want it to last a good many years. So a 100Ah battery can maybe deliver 30-40Ah, and that's assuming it was fully charged to start with. So Barry's existing batteries might be able to deliver 80-100Ah before they need recharging. It's quite easy to get through that on a 38ft Moody, when you start to consider fridge, autopilot, radar, instruments, lighting, nav lights, water pump, stereo, etc. Doubling the size of the battery bank will give additional endurance and will reduce the depth of discharge for a given usage - extending battery life expectancy.

The other main advantage of a big battery bank is that it will accept charge more readily. Even with a smart regulator, and regardless of the size of the alternator, the current which you can push into a battery drops quite rapidly once the battery is up to around 75% charged. Larger battery banks help to take better advantage of the capability of the alternator.

And in case you're wondering, I'm writing from experience. About 7 years ago I upgraded the electrics on my boat, with an Adverc regulator, 90A alternator, 660Ah domestic battery bank and a Link 10 monitor. Since then, I really don't have any electrical worries. And there's always cold beer in the fridge!

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