leaving batteries for an extended period

eidiohir

eidiohir

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Next winter Jerod will be left for a period of just over six months as we are journeying to southern lands for an extended holiday. The question I need help with is what is the best thing to do with the batteries? I would normally charge them every couple of months to keep them topped up but that is out of the question. I did think of connecting up a charger to the shore power by way of a timer but the longest I can find is a seven day. I am toying with the idea of leaving a low powered charger such as those available from Aldi or Lidi permanently connected. The battery bank is 440 amps so one of those little things might keep them topped up without doing any harm. Then again would it do much harm just to leave the batteries as they are just disconnected for the whole period? Any one faced this one before?
 
It would help to know the type of batteries installed

AGM in good condition should be fine if fully charged and left disconnected over winter.
Trojan T105s lose charge pretty quickly and would need to be topped up or float charged to prevent damage
Other battery types will probably be somewhere between these extremes.

Self discharge rate drops with lower temperature and increases as batteries get older. I think that Trojan quote a max. self-discharge rate of 4% per week (prob. at 20-25C but no temp. quoted). AGMs will be much lower, poss. 1% or less per week for some brands. Low winter temps. will help as rate will be lower than quoted.
 
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eidiohir said:
I have two 220 amp lead acid in the domestic and one lead acid 180 amp for the starter. I did think of a solar panel but there won't be much light esp in the shorter winter days.
Click to expand...

I leave a 65W panel connected over winter and it doesn't quite cover self discharge for 4xT105s over winter on Costa Blanca. It's marginal late Dec. - mid. Jan. but otherwise OK. That doesn't really help you, although it's easy enough to calculate the expected Ah/day for each month in Ireland.

It would help to have more information on battery type. I'm assuming you don't have AGM lead acid batteries but have flooded lead acid batteries. You don't mention Trojan so I also assume you don't have golf-cart type deep cycle batteries.

Guessing that you have newish sealed leisure batteries that might make 2% per week a reasonable starting point (if they are in good condition). That means you need to find a minimum of around 14Ah/week. (2% of 620Ah + bit for inefficiency). That's 2Ah/day so not too bad.

An 80W panel should give about 2Ah/day in Dec. and around 2.5Ah/day in Jan. in Ireland (25Ah/day in May-June).

Self-discharge rate I've assumed is only a guess, best to get actual figures for the batteries you actually have. However, it might give you a ball park figure to start. N.B. Even a 40W panel would help as it would slow the discharge rate by a lot (you can do the math). Or just use a small charger to keep the correct float charge if mains power is reliable.
 
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Will the boat be on the hard or in the water. If on the hard fully charge the batt's and then leave disconnected. However in the water you need to keep connected for the bilge pumps. So then the answer is to fully charge and then disconnect everything apart from the bilge pumps. We left ours in the water for a period of five weeks as above. When we got back all batt's were still in good shape.

Good luck
 
If you disconnect, don't use the switch. Remove the neg. cable!
I found a solenoid drawing constantly 300 - 400 mA.
Bilge Pump of course should have a direct connction with a good sized fuse.
 
A 7 day timer is fine..... Once it gets to day 7 it starts all over again....

You've obviously got mains available so get a battery charger that is designed to be left on and has an automatic float charge. I have one of these :- http://www.ringautomotive.co.uk/uk/products/Cars/Battery+Care/SmartCharge-plus-/RSC512

They do a 16A version - mine lasted about a day and got sent back, apparently they have problems with those so I went with the 12 and it's been perfect for 3 years now. Used on the boat, car, motorcycle.....
 
I have two large leisure batteries on board, boat kept ashore Nov - March. This winter and the last I have left them onboard, switched off but connected. One is in a plastic box, the starter strapped to a tray. They have held their charge throughout, although I have the facility to top-up in the spring.
For various reasons I had a brand new car battery surplus last year (55 amp I think). I fully charged it and stored on board for emergency use. Last week I took it to workshop, put on trickle charge. It was up to full in 15 mins.
Just my experiences, otherwise I know nothing about batteries.
 
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