Emergency battery for radio?

[Carduelis]

I'm currently fitting a new dsc radio and so my mind has turned to emergency radio messages etc. One drawback to the fixed set would seem to be that in the event of the boat being flooded, the batteries, being low down, would very soon be shorted out by seawater rendering my smart new radio useless. In fact if the leak was caused by (say) a broken sea-cock, the electrics going off would probably be the first I knew about it!

It occurs to me that I could perhaps fit a smaller rechargeable battery in the alcove behind the set. Something like a motorcycle battery might do. If I did this, what would be the best way of keeping it charged? Also would it have to have a changeover switch This latter wouldn't be ideal as it would be something else to remember in an emergency.

Or maybe it would be better to use the 'emergency' battery as the main source of power for the radio and keep it topped up via a 'follow me' type charger?

Any thoughts anyone..?

 

[Sailingsaves]

A very good idea I think.

If regular batteries were flooded e.g.

I haven't done the sums, but a small deep cycle gel battery sitting on a shelf with maybe a small solar panel may be enough for it to be the only battery supplying radio.

Or use small battery as back up but on trickle charge and have a great big red button for switch over.

A really good post.

I wonder who has already got this set up going?

I'm currently fitting a new dsc radio and so my mind has turned to emergency radio messages etc. One drawback to the fixed set would seem to be that in the event of the boat being flooded, the batteries, being low down, would very soon be shorted out by seawater rendering my smart new radio useless. In fact if the leak was caused by (say) a broken sea-cock, the electrics going off would probably be the first I knew about it!

It occurs to me that I could perhaps fit a smaller rechargeable battery in the alcove behind the set. Something like a motorcycle battery might do. If I did this, what would be the best way of keeping it charged? Also would it have to have a changeover switch This latter wouldn't be ideal as it would be something else to remember in an emergency.

Or maybe it would be better to use the 'emergency' battery as the main source of power for the radio and keep it topped up via a 'follow me' type charger?

Any thoughts anyone..?

 

[charles_reed]

I'm currently fitting a new dsc radio and so my mind has turned to emergency radio messages etc. One drawback to the fixed set would seem to be that in the event of the boat being flooded, the batteries, being low down, would very soon be shorted out by seawater rendering my smart new radio useless. In fact if the leak was caused by (say) a broken sea-cock, the electrics going off would probably be the first I knew about it!

It occurs to me that I could perhaps fit a smaller rechargeable battery in the alcove behind the set. Something like a motorcycle battery might do. If I did this, what would be the best way of keeping it charged? Also would it have to have a changeover switch This latter wouldn't be ideal as it would be something else to remember in an emergency.

Or maybe it would be better to use the 'emergency' battery as the main source of power for the radio and keep it topped up via a 'follow me' type charger?

Any thoughts anyone..?

Have a handheld - preferably waterproof. You'll need one for the grab-bag and your life-raft!
I find I use the handheld more often than the fixed DSC radio. Even though it has 1/3rd the power. That might have to do with being single-handed though.
I also find the obsession with "EMERGENCY" extraordinary - after all travel by boat is safer than travel by car.

 

[Seajet]

Possibly the safest answer is a waterproof handheld radio and an emergency aerial; if you have time, rig the aerial for increased range, if you don't have time you can take the handheld with you.

As for emergency power onboard, how about one of those battery booster packs for emergency car starting etc ? It could be taken home and recharged periodically - with a hi-speed inflator it could inflate the dinghy quickly too.

Halfords sell them but no doubt one can get a similar thing better & cheaper elsewhere.

 

[Carduelis]

I do also have a handheld, but it is less powerful, has a shorter range (being lower down) doesn't have DSC And isn't linked to the boats MMSI number etc. So using the main radio in a real emergency is an altogether better idea IMHO.

I just want to be sure that's its available when I really need it...

 

[cpedw]

I was on a charter holiday in Greece in 2013. That boat was equipped with a small separate battery (perhaps 30/40Ah) for the VHF and a bit of electrickery (a VSR?) that charged it from the main electrics. I was told this was required by a Greek regulation so it's not a brand new idea but seems to make sense. The battery was mounted high up in the cabin (beside the VHF set).

I didn't think much about it then and didn't study it closely. Someone round here will know more detail I expect.

Derek

 

[wooslehunter]

I have a waterproof handheld thats normally clipped to my lifejacket -I sail mostly single handed so wear that most of the timein any case.

The handheld antenna screws onto an SMA connector so I also have a small adaptor that allows me to connect it to the masthead antenna or the AIS one on the pushpit. That way, I get as good receive performance as the fixed set & as good transmit as I'm going to get with the handheld power. It's far better than the normal rubber duck.

The oly real downside it the battery life which is going to be much less than a fixed set with an aux battery.

If you fit an aux gelcell battery, we careful of the transmit time though. On full power transmit, a fixed set could draw more than 5A so the gell-cell needs to be a reasonably big one.

 

[lw395]

I'd agree it's no substitute for a handheld.
But, over the years I've been on a few boats where the main batteries have gone flat through various tales of woe.
Also owned one where starting the engine used to brown-out the GPS, so I had the GPS and VHF wired to a small 12V lead acid.
(that was a basic 1/2/both two battery set up, no dedicated engine battery)

Charging the sealed lead acid battery needs thought. They don't like the high voltages we use for house batteries.
I used a buck boost regulator to take the 14.2 of the main charging circuit down to the 13.8 the sealed battery wanted to float at.
A network of diodes fed the GPS and VHF, so if the house battery was higher, they drew from that.

I'm also not sure that flooding the hull would 'instantly' short out the main batteries?

 

[Jabs]

How about feeding the VHF from a sealed motorcycle battery direct.
Use a bridge rectifier through a one ohm resistor to charge it direct from the domestic bank.

Cheap and effective solution??

Tony.

 

[lw395]

How about feeding the VHF from a sealed motorcycle battery direct.
Use a bridge rectifier through a one ohm resistor to charge it direct from the domestic bank.

Cheap and effective solution??

Tony.

Bridge rectifier will drop over a volt, so it will not charge very well.
It depends how often you have the engine on, vs how much you use the radio.
If it is continuously listening on a channel crossing under sail, that's a fair amount of battery.
I think my old Impala just had a changeover switch to run the VHF from either small or main battery.

 

[SimbaDog]

Not a bad idea :encouragement: However, if the electric system is down, surely the GPS signal to the radio will be lost? That limits it to radio only

 

[pmagowan]

2 things;

You seem to be trying to treat the symptoms of a potential problem rather than the problem itself. If you are worried about flooding your batteries then perhaps you should address the issue of bilge alarms and suitable battery protection. It is not hard to make a box for the batteries that would keep them good for quite some time, depending on location.

Second, I suspect that a complete alternative such as a handheld would be a better option for if your main power fails.

 

[prv]

Not a bad idea :encouragement: However, if the electric system is down, surely the GPS signal to the radio will be lost? That limits it to radio only

So give the radio its own GPS. Manufacturers have finally cottoned on to this idea and started including them, or you can buy an NMEA "puck" for £25 - £30 which is what I have. It's connected to the radio's power circuit so if the radio is on then the GPS is on, and it's independent of any other plotter etc because I don't always bother turning those on.

Pete

 

[brokethebox]

This is a really good idea, i saw that Greece has it as law in one of the posts, and so does Ireland for any commercial boat (ie charter).

You could have your domestic battery charge a dedicated VHF battery located somewhere higher up with something like this...http://www.victronenergy.com/battery-isolators-and-combiners/cyrix-battery-combiner-kit/ that would charge whenever the domestic was being charged.

With a bit of thought and a changeover switch you could have that battery there and never used except when you really needed it

J

 

[SimbaDog]

So give the radio its own GPS. Manufacturers have finally cottoned on to this idea and started including them, or you can buy an NMEA "puck" for £25 - £30 which is what I have. It's connected to the radio's power circuit so if the radio is on then the GPS is on, and it's independent of any other plotter etc because I don't always bother turning those on.

Pete

I like that idea Any suggestions on where to get one?

 

[lw395]

So give the radio its own GPS. Manufacturers have finally cottoned on to this idea and started including them, or you can buy an NMEA "puck" for £25 - £30 which is what I have. It's connected to the radio's power circuit so if the radio is on then the GPS is on, and it's independent of any other plotter etc because I don't always bother turning those on.

Pete

You can make your own NMEa gps, by getting a ublox gps module, a voltage regulator, antenna and one transistor from ebay.
I liked the idea of the GPS being kept alive though, if you get an old fashioned receiver they use a lot less current than a modern plotter with colour screen.
You could have a Magellan HH GPS in a bracket like mine, ready to go with the grab bag.
Since it does about 16 hours on 2 AA's, it would only be drawing 40mA or so from an efficient regulator from 12V.

 

[lw395]

2 things;

You seem to be trying to treat the symptoms of a potential problem rather than the problem itself. If you are worried about flooding your batteries then perhaps you should address the issue of bilge alarms and suitable battery protection. It is not hard to make a box for the batteries that would keep them good for quite some time, depending on location.

Second, I suspect that a complete alternative such as a handheld would be a better option for if your main power fails.

A hand held has very much less useful range.
If you draw a map of where you can reliably get the Coastguard on a handheld in the central English channel, it's not much. You're probably better off with Vodafone?
That might vary for other locations of course.
Even assuming a DSC handheld, which I don't have, to reliably get ships might be pretty limiting off the West Country?

I suspect you do not need to box the batteries in to keep them working in a flooded bilge, simply insulating the terminals might do?
But I've seen too many instances of flat batteries from other causes, such as wiring faults, alternator failures, operator error....

 

[prv]

I like that idea Any suggestions on where to get one?

Here's one for £30 delivered (they used to be a bit less, but the price seems to have gone up in the last couple of years): http://www.ebay.co.uk/itm/NEW-Globa...-Star-IV-/131315022887?_trksid=p2054897.l4275

You cut off the DIN plug on the end, revealing 4 wires. Red and black are power, the other two are NMEA in (for programming, you can ignore it) and NMEA out with position info. From memory the latter is the green one, but do check.

The only complication is that this unit expects 5v, not 12. Forumite "Angus MacDoon" used to sell a little board which converted the power and also provided more convenient screw terminals to attach the radio to, but he seems to have stopped doing so. I made up a similar board myself using a 5v regulator and two capacitors, but these days it would probably be even easier just to gut a 12v->USB phone charger (USB power is 5v).

Pete

 

[lw395]

http://www.ebay.co.uk/itm/VK16D-ubl...sGames_RadioControlled_JN&hash=item3ce9c1d767

Might be worth a play.
NB, I still disapprove of indoor GPS antennas, but something like this could be mounted outside quite easily.

 

[Sailingsaves]

View attachment 46379Must confess, I did assume OP had a handheld radio already.

Still like idea of dedicated or backup battery on shelf. 12Ah on £42 such as below.

http://cpc.farnell.com/jsp/search/b...cAttributeId=&prevNValues=411+214346+705+2005

Attached photo is one of my handhelds (I have 2 identical Standard Horizon ones - must be about 10 years old now and in mint condition) with emergency aerial and I carry various adapters in the bag in the top of the aerial case. Background is a gel deep cycle 12Ah battery (easily lifted in one hand).

You then have choice of handheld (only any good if you extend the aerial as others have stated - but still only 5Watts) or the ship radio with mast height aerial (if mast is still there) at 25Watts with this Greek? idea of backup battery.

Prepare for the worst, hope for the best.
Train hard, fight easy.