Would a small battery do the job?

borat · 11 May 2007, 04:11

Hi there,
Im looking to fit a Garmin 140 fish finder to my rib.
At present i do not have any 12 volt electric`s on board, having pull start engines.
I am hoping to use a small 12 volt motorbike battery instead of large marine one.
Has anyone used this set up before? and how long did it power the unit for?

cheers
pete

Nos4r2 · 11 May 2007, 04:45

Don't faff about with a bike battery for that. Get a sealed one instead. It'll last just as long but won't spill acid.

JABS · 11 May 2007, 07:18

The battery on my Honda bike is sealed!

Find out the power consumption of the Garmin. Allow for the illumination. It is probably in the instructions somewhere.

Lets say it is 500mA. That is half an amp. Decide how long you need it to run on one trip. Say five hours. That means it will consume five times a half which is two and a half amp hours. So look for a 12v battery with at least double that capacity, that is five amp hours.

Maplin sell sealed batteries and chargers.

Bear in mind that 12v electrics on a boat running from a battery under charge from the engine would run at 13.6 volts. You will be running at around 12v max. The Garmin could be sensitive to battery terminal voltage. Might be worth a call to Garmin.

Or, you could run on a pack of torch batteries and carry spares. Maplin have carriers.

Hope that helps.

Hugh Jardon · 11 May 2007, 08:17

bike batteries are very fragile and can run down quite quickly and are quite expensive for their size, personally i would say if a small cheap car battery will fit on the boat somewhere that would be my preference of a way to go

i can not tell you how many bike batteries i have replaced over the years, they dont like being laid up for periods of time

havener · 11 May 2007, 08:25

Try your local country / farmers store, go for an electric fence battery. They're built to be left out in the open, generally abused, and are usually quite small in size.

Simon

vince · 11 May 2007, 09:14

We had a jet ski battery under the seat of our sib, which ran a lowrance fishfinder, nav lights and a cobra dsc radio, all tucked under the seat. The charge lasted for ages, in fact, we had that set up for about 5 months till we sold the boat, and only charged the battery twice. Cant remember the capacity of the batt, but it was small and neat, and sealed.

jwalker · 11 May 2007, 11:01

I use these.

I've got one in front of me running my indoor Navtex, I bought it in 1999 and it's still fine.

Jizm · 11 May 2007, 15:41

Quote:

Originally Posted by jwalker

I use these.

recommended!

codprawn · 11 May 2007, 21:11

For those sealed gel type batteries it is often cheaper to buy a jump start pack or a spotlamp or whatever rather than buying the battery on it's own!!!

codprawn · 11 May 2007, 21:20

Quote:

Originally Posted by JABS

The battery on my Honda bike is sealed!

Find out the power consumption of the Garmin. Allow for the illumination. It is probably in the instructions somewhere.

Lets say it is 500mA. That is half an amp. Decide how long you need it to run on one trip. Say five hours. That means it will consume five times a half which is two and a half amp hours. So look for a 12v battery with at least double that capacity, that is five amp hours.

Maplin sell sealed batteries and chargers.

Bear in mind that 12v electrics on a boat running from a battery under charge from the engine would run at 13.6 volts. You will be running at around 12v max. The Garmin could be sensitive to battery terminal voltage. Might be worth a call to Garmin.

Or, you could run on a pack of torch batteries and carry spares. Maplin have carriers.

Hope that helps.

They actually consume 3.5w at peak which is about 300mA . Voltage range is 10 - 18vdc so that's not a problem.

Jump start packs can often be cheaper as I said - you can either dismantle them to get at the battery or leave it as it is. Weight is a pretty good indicator as to the size of battery.

JABS · 11 May 2007, 22:44

Just took my rechargable torch apart.

The battery is 6Ah. It was a bargain! And came with a mains charger.

Great idea Cods!

codprawn · 11 May 2007, 23:06

Quote:

Originally Posted by JABS

Just took my rechargable torch apart.

The battery is 6Ah. It was a bargain! And came with a mains charger.

Great idea Cods!

Make sure it's 12 volt though - most of the spotlamps are only 6v.

I found this out when my battery died in my lamp - it was cheaper to buy a new lamp - still doesn't feel right just chucking it away though!!!

borat · 12 May 2007, 00:49

Thanks all for your time and advice. My minds made up, i`m going for a small battery, i didn`t really want to carry around the extra weight of a bigger marine/car one that is not needed.
Cheers
Pete

jyasaki · 15 May 2007, 16:26

I ran a 14' Achilles/Honda 40 driving a FF and a GPS off a tractor/garden battery. The battery itself cost about $35 at a home center (OSH, as I recall), and would run the electronics all day on the hook and still have enough to start the motor at the end. It's a little larger than a motorcyle battery (maybe twice the size?) but was right for the price.

I also found out (don't ask how) that the battery works fine while submerged in seawater.

jky

alystra · 30 May 2007, 12:23

Quote:

Originally Posted by codprawn

Jump start packs can often be cheaper as I said - you can either dismantle them to get at the battery or leave it as it is. Weight is a pretty good indicator as to the size of battery.

Thinking about a small battery too and fancied the SLA ones mentioned. Then saw the price of the chargers.

Twice the price of the battery. Of course I've got a shed load - well, three

old fashioned (30 yrs old) chargers, but I think they'll knacker the SLA types.

Am I right? Anybody know?

Jump start pack seems the way to go - unless I can find a good torch cheaper. Screwfix one's got a flourescent light too.

codprawn · 30 May 2007, 12:38

Quote:

Originally Posted by alystra

Thinking about a small battery too and fancied the SLA ones mentioned. Then saw the price of the chargers.

Twice the price of the battery. Of course I've got a shed load - well, three

old fashioned (30 yrs old) chargers, but I think they'll knacker the SLA types.

Am I right? Anybody know?

Jump start pack seems the way to go - unless I can find a good torch cheaper. Screwfix one's got a flourescent light too.

SLA's will actually accept a higher charging voltage than a normal lead acid. Just watch the output current doesn't exced about 10 - 20% of the capacity. For example a 10ah battery should only be charged at about 1 amp. Car chargers are usually more than this.

Lidel had a good 12v sla charger for about £6 the other day.

Of course if you buy a jump start pack it will also have the charger with it!!!