Reccomendations for a portable 12v battery?

Kelpie

Kelpie

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I'm planning to have the boat in a marina without shore power this winter, and will be spending the odd night aboard (without actually going sailing).
I don't want to have to run the engine just to charge the batteries so am looking at getting a smallish 12v battery that I can easily take to and from the boat. It would have to have enough juice to run my LED cabin lights and the laptop charger for an evening.

What sort of Ah should I be looking at? And should I disconnect the current battery bank so that my new little battery doesn't just drain itself into the big batteries immediately?
 
A little yuasa battery might do the job? Screwfix do an equivalent?

As for power rating well that needs more info but LED lights are not going to use much, the laptop might though, radio?

They also do a small wall charger for these batteries but a car charger set to just a couple of amps should be ok I guess, but do check that: data sheet or the like.

Enjoy those cold nights....
 
Depends on number of lights, power of laptop charger of course but would have thought 80ah should be enough. Rather than buy especially, is your engine start battery suitable?
 
Would rather not use the engine battery as it's buried under the cockpit floor.
I forgot about the heater which will need a bit of current... it's a Wallas so fairly frugal- from a quick google about 0.4A.
I realise it's a bit of a 'how long is a piece of string' question, but I was wondering if anybody was aware of batteries specifically designed to be portable, with a decent handle for example.
The jump start packs are interesting but surely designed for quick bursts of power rather than a deep cycle- but maybe that doesn't matter?
 
depends on how far the boat is from the car park,a battery may not be heavy for the first 20/30 yards,but gets VERY heavy after 200.
would you not as has been said,be better to get a secondhand battery from a breakers and then a cheap solar panel to keep it charged on the boat
 
hartcjhart said:
depends on how far the boat is from the car park,a battery may not be heavy for the first 20/30 yards,but gets VERY heavy after 200.
would you not as has been said,be better to get a secondhand battery from a breakers and then a cheap solar panel to keep it charged on the boat
Click to expand...

If going down that route, why not spend the money on more panels and connect to and use the domestic bank?
 
The distance from boat to car, including getting across the raft and up the ramp, is further than I would like to carry a car battery plus all my other clobber.

Main question remains- should I disconnect the existing battery bank whilst hooked up to a portable battery?
Also wondering about ballpark figure for the battery's capacity- am I looking at 7Ah or more like 30??

Oh and about solar... well that's a bit of a joke... fine in the summer to counter self-discharge, but the sun is a strange and seldom seen myth when it comes to the winter months in this part of the world...
 
Mavanier said:
The distance from boat to car, including getting across the raft and up the ramp, is further than I would like to carry a car battery plus all my other clobber.

Main question remains- should I disconnect the existing battery bank whilst hooked up to a portable battery?
Also wondering about ballpark figure for the battery's capacity- am I looking at 7Ah or more like 30??

Oh and about solar... well that's a bit of a joke... fine in the summer to counter self-discharge, but the sun is a strange and seldom seen myth when it comes to the winter months in this part of the world...
Click to expand...

No trolley or wheelbarrow ??

Yes disconnect the existing battery or that may well tend to supply most of the power, at least while it remains fully charged.

You have to work out what size battery you need.

Look up the consumption, in amps, of all the gear and gadgets you will be powering. If necessary calculate it from amps = watts/volts

For each one multiply the amps by the number of hours each will be used during the time you will typically spend on board. This gives the requirement for each in ampere hours (Ah)

Add all the Ah figures together. Get a battery with a capacity double that.

You may find your power requirements are so modest that you can go for several "odd nights" without recharging the battery although best not to leave it partially discharged if avoidable.

IMHO not a good idea to carry batteries unnecessarily by their "carrying" handle. I have good leisure battery here that is leaking between the case and the top. I reckon due to being carried, lifted and generally humped about using the handle.
 
Mavanier said:
W
The jump start packs are interesting but surely designed for quick bursts of power rather than a deep cycle- but maybe that doesn't matter?
Click to expand...

I had to do some work inside my boat that needed a decent light for several hours a day.

I used a starter pack to power a 12 v halogen floodlight. It worked fine and was easy to carry home each evening for an overnight re-charge.

Also a useful thing to have for starting car and boat engines when necessary.
 
Checked the power consumption on the laptop, seems it blows everything else out of the water. So maybe my answer is to charge it off the boat whenever possible and the heater and lights will barely dent the batteries.
 
 
Another option which amy help is to go for NiMH rechargeable as used in electric drills. From my research Sub C size with tags are the cheapest amp hour for pound. Ten soldered in series will give 6AH at12v. They are certainly light to carry. Another advantage is that you will not harm them by using all the AH unlike lead acid. Recharge froma 12v plug pack witha resistor for slow recharge over 24 hrs at about .3 amp. Excellent for lights possible heater also. At the price you might go for 2 of these batteries wired together in a small plastic lunch box with terminals. Remove the lights fuse ijn the boat to isolate main battery or have a changeover switch.
http://www.ebay.com/itm/10x-Sub-C-S...US_Rechargeable_Batteries&hash=item415dec14f5 good luck olewill
 
Mavanier said:
I'm planning to have the boat in a marina without shore power this winter, and will be spending the odd night aboard (without actually going sailing).
I don't want to have to run the engine just to charge the batteries so am looking at getting a smallish 12v battery that I can easily take to and from the boat. It would have to have enough juice to run my LED cabin lights and the laptop charger for an evening.

What sort of Ah should I be looking at? And should I disconnect the current battery bank so that my new little battery doesn't just drain itself into the big batteries immediately?
Click to expand...

Why not fit a solar panel? Capital costs about the same. You're a lot farther S than Muurame and I know of one boatowner who reckoned his 250 watts of PV panel kept his batteries fully charged all winter (2:45hrs sun in Dec-Jan)
 
Last edited:
I already have a 10w panel which last winter was unable to keep up with the self discharge of the 150Ah bank. That was with the boat de-rigged so no shade problems. In the long term I would like to fit a bigger panel but that's going to be a £100 project, whereas a 20Ah battery is more like £30.
 
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