I have a minkota 50lb thrust electric outboard and two 85ah leisure batteries to run it off.

Now the batteries are absolute rubbish, they were fine the first season i used them but now they only last about 2 hours each opposed to about 8 hours before, i always keep them topped up with water but did leave them dead for about 3 months plus i use a standard car battery charger to charge them.

I am going to get a new 110ah battery for this season and i dont want the same thing to happen to this one as they are not cheap, can any one tell me the correct way of storing and charging these type of battery.

Cheers

Lee

Try here:-

http://www.batteryfaq.org

Jim

cheers jim,

some of that is a bit technical :confused:

[ 18. April 2004, 09:26 PM: Message edited by: Lee-sox ]

Leaving it dead for three months is enough to kill off any battery. I don't know how much boats differ from cars, but I'm wondering if you should be using leisure batteries at all.
I found this on another website, which may, or may not be useful:
"Leisure batteries are designed to tolerate reasonably deep discharges (80%-ish should be your limit) over some number of hours. They are designed to withstand this type of duty several hundreds of times before the battery is significantly reduced in effective capacity. They are not designed to provide very high discharge currents of the type associated with cranking over a car engine to start it." Perhaps this is different for boats, but I know nothing about them. Perhaps you should have a starter battery and a leisure battery.
"You might need to measure a few volts across the battery when it is charging. Expect to see a minimum of 13.8 volts and probably nearer 14.00 volts. Anything less will mean you are not charging properly. Anything much more than 14.2 will mean you are over-charging and can potentially damage your battery."

[ 18. April 2004, 10:01 PM: Message edited by: Peter Sharpe ]

Lee-sox - the charger you use needs to have settings for both a normal (as you use for cranking a car) and a deep cycle battery. Else you need two different chargers. They need totally different handling

And it is critical to keep the battery at full charge between uses.

Peter - the plates on the deep cycle batteries are much thicker. Designed (as you noted) for many discharge/recharge cycles. Depending on the trolling motor he has, it may only need a single battery or it may require a pair (or more). Our trolling motors are designed for 12 volt DC operation or 24v or 36v depending on the power output. A 50 is right on the border. Very possibly needs a pair of batteries to operate.

[ 18. April 2004, 10:41 PM: Message edited by: Newt ]

I see...I thought leisure batteries were something 'her indoors' needed when her man can't perform.

quote:

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Originally posted by Andy Macfarlane:
I see...I thought leisure batteries were something 'her indoors' needed when her man can't perform.

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... yup & you can get them at Poundland

The quoted capacity of a bettery is usually the 20 hr discharge rate. An 85 Ah battery is therefore guarunteed to deliver 4.25 A for 20 hr. This is probably about the current needed to drive the motor on its lowest setting. If you draw more current, the battery will run down faster. The greater the difference between the 20 h curent and the curent actually drawn, and the greater the apparent loss of capacity. Discharging the batteries at more that the quoted rate can also damage them.

A 50 lb thrust motor probabaly takes about 50 A at full power, so if you spend any significant amount of time at more than setting number 1, you will get a lot less capacity than you thought and shorten battery life quite significantly.

The way around this is to hook your batteries in parralel which increases the capacity without affecting the voltage. It is a lot more efficient to flatten two batteries together that to flatten them one after the other. It also does a lot less damage to the battery.

I now have hree batteries in the boat, giving a total capacity of 305 Ah. This means I can be guarunteed a current of just over 15 A for 20 h. That equates to about 15 lb of thrust, which is plenty.

The abtteries are all spread out so that the boat is nicely balenced, and the wiring was all designed carefully so you hardly know they are there. The difference in battery life is quite surprising. Even in quite strong winds I can fish a whole weekend with no noticable loss of power.

Also - Halfords do a really good battery charger that automatically switches into a 'maintain' mode once the batteries are fully charged. I keeep all three batteries permanenntly rigged in parallel and attached to the charger. Another tip - look in a caravan show room, you can get some fantastic quick release terminals which snap onto the battery posts.

Cheers StuMac, very helpful

All a bit technical!

Easy answer is yes you should use leisure batteries as they are designed to be repeatedly charged and discharged.Car bats are not.

Never leave your bats in a discharged state,allthough you have all ready learnt this expensive lesson!