Power to VHF radio

[FulmarJeddo]

Is it normal to supply the power to the VHF from the engine start battery or the domestic batteries? I seem to be using more power out of my domestic batteries than is going in, so I am following the other thread on battery usage with interest. I think my problem is the combination of the way I have a spit solar charger and a VSR between the two domestic batteries.

On Sunday I had been sailing with the fridge on and the Autopilot working hard in the rough conditions. Later in the day I was called up by one of the other boats I was racing as there was concern over one of the boats going missing. Whilst I could receive clearly my transmission was barely readable. As it was a safety call I started the engine and the radio worked fine. Whilst I know I need to sort out my charging system (solar and alternator), I am now wondering if I should have the radio fed from the engine battery that seems to always be fully charged.

Oh, and the missing boat, a Snapdragon 24, turned out to have turned back when the the wind reached 30kts and the waves huge. He had tried calling the rest of us, we were taking part in a club race around the southern Thames Estuary, but no one heard him.

 

[prv]

The VHF would normally be supplied by the service bank just like everything else. Connecting it to the engine battery might be an expedient fix in your case - you're unlikely to flatten the battery with a radio - but the real problem is that your service battery is either undersized or knackered, or your charging regime is inadequate.

Pete

 

[Burnham Bob]

Best practice is always to keep the engine start battery totally free of all other loads. If your domestic battery is running low, it would be better to upgrade the capacity rather than risk a flat start battery when you need it. As you say, sorting out the charging may solve the problem. However, for the price of a bigger battery you could invest in a hand held vhf which is very useful in any case and will solve the lack of battery charge problem. Mind you, the problem of your transmission could be a simple temporary glitch and purely conincidental with the engine start. Only wiring convention I know for vhfs is to wire them direct to the battery so if there's a switch panel failure or fire you've still got emergency contact. A voltmeter would tell you whether the battery charge is low but some radios (mine is a Standard Horizon) actually have a readout for low battery. And remember if you leave the vhf on (it does happen) and you are away from the boat for a while your starter battery could well be flat if that's how its wired.

 

[johnalison]

Unless things have changed recently, a VHF might take about 0.3 amps when not transmitting, so a day's sail of ten hours would take 3 amp-hours worth, which is not much, but taking it from the starter battery is not something I would choose to do.

 

[wooslehunter]

Normally connect to the domestic bank.

One backup is to use a small sealed lead-acid battery mounted high up. This can be kept charged & disconnected or connected to a trickle charger just to keep it topped up. Connection to the VHF can be via a changeover switch in the power lead to the VHF. If there's a big problem like a flood or more likely an electrical fire causing a total electrical failure, then at least you have a small backup to run the VHF for a limited time.

Simplest alternative of course is a handheld. I can easily connect my handheld to the mast top antenna or a spare on the pushpit if needed.

 

[Sailingsaves]

Edit - Beaten by Wooslehunter

If I ever get a cruiser again, I like the idea some others have had of powering the vhf directly (after a fuse of course) from a smaller sealed battery that is secured high up and charged via a VSR or the like.

Not likely to be flooded if taking on water, always live if something happens to rest of electrics...

 

[lpdsn]

Only wiring convention I know for vhfs is to wire them direct to the battery so if there's a switch panel failure or fire you've still got emergency contact.

That's an urban myth, or at least a yacht-club myth. The real reason for wiring directly to the battery was to minimise noise on other circuitry.

 

[FulmarJeddo]

Thanks for all the comments. I don't think the domestic batteries are at fault. Both are 110 Ah, one was new last year and the other this year. I do have a hand held Icom, one that discharges itself, but that was sitting in its charging cradle at home!
I am on a swinging mooring so trickle charging from anything other than solar power is out of the question. I do like the idea of a switched sealed battery and will look into that.

I think I probably caused the charging problems when I fitted the fridge and 2nd domestic battery. I currently have a VSR between the two domestic batteries with the idea that it would share the charge from the solar panel. I suspect the small current it is drawing is taking more than the solar panel is putting in. I already had a Maplin's split charger sharing the solar output between the engine and domestic battery. I think I need to put the solar output to the 2 domestic batteries and alter the VSR so it's not sitting across the 2 batteries.

 

[lpdsn]

Edit - Beaten by Wooslehunter

If I ever get a cruiser again, I like the idea some others have had of powering the vhf directly (after a fuse of course) from a smaller sealed battery that is secured high up and charged via a VSR or the like.

Not likely to be flooded if taking on water, always live if something happens to rest of electrics...

I did seriously consider that. I didn't do it because of concern about the weight of even a small lead acid battery at the chart table in the event of a knock down. On my boat it would've required a significant amount of woodwork to make a structure that would be guaranteed to hold it in place.

I also looked at a LiPo battery, but that would need it's own charger (not expensive, but between them they'd consume a fair amount of space).

 

[lpdsn]

I currently have a VSR between the two domestic batteries with the idea that it would share the charge from the solar panel.

Are your domestic batteries in separate circuits rather than a single bank?

 

[FulmarJeddo]

Are your domestic batteries in separate circuits rather than a single bank?

They both have separate isolator switches, so I can use them individually or in parallel. The VSR is permanently (fused) across the two.

 

[fisherman]

- you're unlikely to flatten the battery with a radio -
Pete

Sure? mine is connected to the service side, came down one day after two days away and had left the main switch on, when it gets low the squelch cuts in and the battery goes flat and noise to annoy the neighbours. The OP found that although he could receive, one amp draw usually, transmit needs 7 amps on 12 v and he had not enough power. Wouldn't risk the start batteries, on my boat they are sacrosanct. One of my VHF sets is connected direct to a battery with as little in between as possible, main switch and inline fuse only. I would by pass the main switch but I'm not reliable enough to turn it off every time.

 

[lpdsn]

They both have separate isolator switches, so I can use them individually or in parallel. The VSR is permanently (fused) across the two.

It would simplify things if you just had a single domestic bank (with the starter battery separate). Once you start subjecting them to different cycles there's always going to be one battery that's worse than the other and drags it down when you parallel them.

I'd also think again about sharing the solar output with the engine battery. I suspect you're trying to do too much with what you're getting from the panel. An alternative is another separate smaller panel with it's own controller for the starter battery.

I have thought about daisy chaining cheap controllers as a means of charging both starter & domestics, but haven't yet spent the time to investigate it properly, so I don't know if it's a good idea.

Do you have any form of battery monitor or voltmeter fitted? Even one of the cheap Chinese LED voltmeters would be very useful for you, I think. They cost only a few quid.

If it were me, I'd go into a marina for a night and plug in to make sure all batteries were fully charged as a starting point, then start monitoring the voltage when back off grid and relying on the solar panel.

 

[JumbleDuck]

One backup is to use a small sealed lead-acid battery mounted high up. This can be kept charged & disconnected or connected to a trickle charger just to keep it topped up.

I'd like to do that, using a gel cell, but it seems that nobody makes chargers for them which run on nominal 12V. The RC model flying world would love 'em, but they just don't exist.

 

[Sailingsaves]

I'd like to do that, using a gel cell, but it seems that nobody makes chargers for them which run on nominal 12V. The RC model flying world would love 'em, but they just don't exist.

Would this work?

http://cpc.farnell.com/1/1/5582-camdenboss-beg120075-battery-deep-discharge-gel-12v-7-5ah.html

I have a 12AHour one and charge it via a car battery from Aldi and sometimes via an homemade trickle charger. It rests at 12.7V.

I 'phoned Camden Batteries to ask if it was 12V or 12.7V and they said 12.7 Volt was okay. It is about 4 years old now and still going strong.

Could be hooked into a VSR and stick in a DC buck converter if you don't want anything over 13Volts charging it?

 

[lpdsn]

I'd like to do that, using a gel cell, but it seems that nobody makes chargers for them which run on nominal 12V. The RC model flying world would love 'em, but they just don't exist.

I had in mind something like this for charging a LiPo battery. Looks like it is design to charge up your model aircraft battery from a car battery, but seems it handles charging Lead acid batteries too. Not sure of the complexity of the charging algorithm.

http://www.banggood.com/Wholesale-IMAX-B6-Digital-RC-Lipo-NiMH-battery-Balance-Charger-p-46220.html

 

[davidej]

I do have a hand held Icom, one that discharges itself, but that was sitting in its charging cradle at home!

A bit of thread drift but my ICOM HH does that. I found that if you withdraw the battery after use, it holds it charge for months.

Someone told me it is because the set was originally designed for NiCads but now has LiPo batteries

 

[JumbleDuck]

Would this work?

http://cpc.farnell.com/1/1/5582-camdenboss-beg120075-battery-deep-discharge-gel-12v-7-5ah.html

That's the sort of thing. The trouble with charging them is that, as they are sealed, you have to be awful careful not to gas them, which means - normally - multi-stage constant-voltage charging with good temperature compensation. There is a good article about it at http://www.qsl.net/wb3gck/gel-cell.htm.

Lots of places sell good mains chargers for gel cells, but nobody seems to do them for a car supply.

 

[William_H]

Back to OP problem. I think it a problem to use a VSR btween 2 lots of domestic batteries whenb charging from solar. A vsr is likely to take significant current when operated. Depending on the size of the relay a large one perhaps .25 amp. Not a problem when charging from an engine alternator but a lot from solar when it will be wasting power all the time the solar is charging. As said move the dual output solar controller to the 2 domestic systems. Perhaps a smaller solar panel without controller just for the engine battery.
A said you must have a volt meter for the domestic batteries. These little guys are small and bright and very cheap http://www.banggood.com/0_28-Inch-2_5V-30V-Mini-Digital-Voltmeter-p-974258.html
Then I suggest a managerrment regime where you run the fridge from one domestic battery only. Presumably it will cut out if volts get too low.
good luck olewill

 

[FulmarJeddo]

Back to OP problem. I think it a problem to use a VSR btween 2 lots of domestic batteries whenb charging from solar. A vsr is likely to take significant current when operated. Depending on the size of the relay a large one perhaps .25 amp. Not a problem when charging from an engine alternator but a lot from solar when it will be wasting power all the time the solar is charging. As said move the dual output solar controller to the 2 domestic systems. Perhaps a smaller solar panel without controller just for the engine battery.
A said you must have a volt meter for the domestic batteries. These little guys are small and bright and very cheap http://www.banggood.com/0_28-Inch-2_5V-30V-Mini-Digital-Voltmeter-p-974258.html
Then I suggest a managerrment regime where you run the fridge from one domestic battery only. Presumably it will cut out if volts get too low.
good luck olewill

Yes, that is the opinion I have come to. I will be disconnecting the VSR on my next visit. I do have a multimeter on the boat and checked the voltage when I arrived at the boat on Saturday as I had some issues with the fridge previously. I can't remember the exact figures but the two domestic batteries were both around 12v and the engine start battery about 13.5v. I ran the engine for a while to check it was charging. The engine battery went up to around 14.5v and the domestic got up to the high 13v's, but obviously their low charge state prevented them getting any higher. I will move the dual output solar control to the two domestic batteries, and keep an eye on the starter battery. I think the engine gets enough use to keep that topped up.
We have had some very unseasonal wet and windy weather over the last few days so I suspect the solar panel has been doing very little, so the sooner I get it done the better.
David