Lightweight 12v battery

matg

matg

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Hello,

I'm looking at installing a lightweight battery on my boat rather than spending out on an alternator kit for my outboard. I'll keep the battery at home and charge it before taking it down to the boat. It'll only be running a bi-data unit when I'm out sailing and possibly a vhf.

Just wondering whether any 12v battery will do, as I've seen this that weighs under 2kg:
http://www.criticalpowersupplies.co.uk/csb-UPS122406

Would this suit the purpose and could I charge it using a car/motorcycle charger?

Many thanks,
Mat.
 
Probably do fine provided there is not too high a demand on it. Why not use a small solar panel to charge it on the boat instead of taking it home every time.

I use a golf trolley battery with solar panel to run a bilge pump on my old wooden sailing boat which leaks like a sieve. Seems to work OK.

Solar panels available for under £15 on Ebay but be sure to get a waterproof one or seal it yourself - take it to bits and stick it all together again with CT1 or Sikaflex.
 
Lets assume that the VHF will transmit for 5% of the time so 6a = .3a, receiving on speaker 50% so @1.2a = another .6a, bidata is another .35a so including the VHF on standby for 45% of the time your average consumption would be about 1.2a so that thing would last you about 5hrs before it was discharged to it's claimed 100% discharge capability. (I have used manufacturers equipment ratings @ 13.8v so as the battery gives less than that as it discharges the current will increase and consequently reduce the time). You could adjust the times that the currents are drawn to reflect your own expected usage but even then there would be little margin.
 
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Note that the 5 AH is the 20 hour rate, ie about 0.25A. Discharging at a higher rate will give less amp-hours. Also, regularly discharging the battery to less than about 60% charge will lessen the battery's life.

Ian
 
Thanks for all your replies. Really useful information from everyone.

I'll possibly look to buy a slightly heavier battery with a higher AH rating.

Definitely interested in the solar panel option, will do some further research into that.

Many thanks,
Mat.
 
It will power your Bidata no problem.

Likewise, I would expect, a VHF RT on standby
Once actually recieving a signal the current consumption will rise perhaps up to 2 amps at max volume. This could start eating into you battery capacity.
The current consumption when transmitting is likely to be around 6 amps at 25W power output. This will soon eat up your available battery capacity if you were in a position where you need to transmit for many minutes.
There is no data on the battery specification page to indicate how long you could draw 6 amps before the volts dropped to the point that the radio performance would deteriorate. Not long at all I feel based on the data that is there.

IMHO the battery is not large to properly support a VHF RT.

As for charging, any small automatic charger would do the trick. ( Lidl and Aldi often have them at an attractive price.)
A small solar panel would also.
 
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I've gone for a 12v 12Ah battery, weighing in at 4kgs. Recommended for golf carts and mobility scooters.

I'll most likely just be running the Bidata from it. I'm looking to change my old VHF for a handheld anyhow.

Thanks for all the advice.
Mat.
 
matg said:
I've gone for a 12v 12Ah battery, weighing in at 4kgs. Recommended for golf carts and mobility scooters.

I'll most likely just be running the Bidata from it. I'm looking to change my old VHF for a handheld anyhow.

Thanks for all the advice.
Mat.
Click to expand...

I bought a Lucas 12v., 12Ah mobility battery 2 years ago to keep on the dayboat to pump out rain and leakage water. I find that it will serve a whole season without needing a recharge but the blade type terminals are rather fragile and I ended up containing it in a plastic box with wiring from the battery terminals to a waterproof socket on the side of the box. That way I make and break using the plug and socket rather than clipping and unclipping at the terminals.
 
I had a couple of battery packs made up for my sailplane.

NiMh super D cell size. A 13 A/Hr pack weighs in at just 1.8kg. A great power to weight ratio and an excellent current delivery capability coupled with a good long shelf life. They do need a special microprocessor controlled charger however.

( and they did set me back north of £220 for each custom made pack and charger. )

But it was worth being able to shift the C/G back a couple of mm! :)
 
Lightweight battery

My VHF draws .45amps on receive. I think additional current on transmit and when receiving signals can be disregarded. (depends on traffic) If bidata is .35A that makes .8 amp drain for a 5AH battery. So perhaps 5 or less hours of life to fully discharged. So from this and other's estimations you might want more AH. These kind of batteries are available in a large range of AH ratings. Larger of course means heavier. So if you go this way taking battery home you need to juggle weight and AH. I would find taking a battery home a burden but then i walk to my boat.
If you go the route of a solar panel then you will want a larger battery. Eventually you might find the common car battery is cheapest due to large market. Indeed you might want to update your car battery to new and fit the old to the boat. A solar panel in the 5 to10 watt range will recharge possibly over a week (don't buy a regulator).
I use a 5w solar panel that is probably only producing 1w these days due to corrosion etc into an old wet Nicad battery good for about 6AH this suits my lighting and radio needs but I confess i don't leave the radio on while sailing. I lash the panel to the top of the boom cover when I leave the boat. I stow it for sailing. I havn't had a battery flat situation for many years but then we get lots of sun. olewill
 
Why not look at the combined starter/battery/compressor type devices that are available?

They come with a tough enclosure, charger and cigarette lighter/croc-clips as standard. A 17AH model can be had for £40. I use mine as a backup starter battery (will easily spin a 1GM10) and general emergency 12V source. It also has a USB power connector that will run phone, camera and iPad.
 
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