Silly Question On Sounders.

[humesy]

Howdy,

I am keen to upgrade my sounder from a Navman 4200 to perhaps a Lowrance X515C. I have recently had trouble with my batteries and am trying to diagnose the problem. I have just managed to kill 2 batteries and it is possible that I am allready drawing too much power while at anchor running a live bait pump, sounder and nav lights. running 2 batteries has been suggested and I know it would be great but I don't really have the space to fit them.

My question is, how much extra power would I be drawing from the battery running the lowrance? It runs at 500 watts RMS. The navman runs at 150 watts RMS. This is all pretty foreign to me. Obviously I need to diagnose the power problem first.

I have also read a few opinions on comparisons to the humminbird 777 and the garmin 620.

Feel free to add your thoughts on this as well.

Cheers

[Boban]

I'll start off by saying that you should make room for the two batteries, especially since you are fishing at night.

There are other power saving measure you can also easily adapt.

1. Use an LED anchor light. You're nav lights will be off when you are at anchor.

2. Get a timer for your live well pump. It doesn't need to be on constantly.

3. Turn off your sounder at anchor. Why do you have it on. If drifting I understand, but why at anchor.

As to the mathematics of it all.

A 500W sounder at 12V will draw 41.6 amps. (Your Navman would draw 12.5A at 12V). With a 100A battery that will give you just over two hours. Even with two batteries that is not good. However, I dont know how they measure the 500W. If the current to the transducer is reduced to 1V then the calculations I did above are useless. I have a suspicion that it wont be 500W at 12V because my Raymarine has the same specs and I have had no problem leaving it on. But then again the Honda alternator is 40A so that may have a lot to do with it.

I wouldn't worry too much about the sounder. I would be more worried about what is actually draining the batteries because it doesn't sound right. It may well be, but just doesn't sound right.

OK just did some research, and the current drain is in the order of 600-700 mA. This means that your sounder would take over 100 hours to drain your battery. It's just not going to happen.

Edited September 19, 2007 by Boban

[fishingrod]

A 500W sounder at 12V will draw 41.6 amps. (Your Navman would draw 12.5A at 12V).

Boban is on the right track with points 1, 2 & 3

EDIT BELOW: Boban has just corrected his original post.

His maths calculation is correct when looking at typicaly resistive type wattages/loads on a battery (such as a light bulb) HOWEVER the output of a sounder is not a direct relationship as calculated.... but 10 points to Boban for trying

I'd be suprised if either the Navman or the Lowrance 500w sounder draws any more than 1-2 amps. Upgrading the sounder will not use much more power from the battery.

A 100amp/hour battery will not supply 100 amps for 1 hour or 50 amps for 2 hours.

The rating is done at a certain discharge rate and allows to battery volatge to fall to a certain figure. There is a standard somewhere for how they calculate it. Not all the power stated will actually be usable !!

It might be 5 amps for 20 hours for example. However after (say) 15 hours the battery voltage may have already dropped to 11-11.5 volts meaning that you will struggle to start your motor or run your Marine Radio sucessfully. They still call this a 100amp/hr battery !

Sorry for all the techno stuff .... its in my blood and I want to point people in the right direction

cheers

Rod

edited: Boban corrected his post while i was typing !

Edited September 19, 2007 by fishingrod

[a boat]

Hi Humesy, as the other guys have said there is no way a good quality marine battery of about 640CCA would be killed by running live bait tank / nav lights and sounder. You could run these all night and not have a problem because they do not draw much current. Upgrading the sounder will not cause you a problem either, so if you have gone thru two batteries, than you have a problem that needs to be solved to stop you having to buy batteries all the time. Check and make sure you do not have wing nuts, have water in the battery and nice clean terminals. On the outboard side make sure the battery charging system is up to spec and failing that I can not think of what would be causing your dramas.

Let us know what you find once you check your wiring etc,

Cheers,

Huey.

[humesy]

Hi Humesy, as the other guys have said there is no way a good quality marine battery of about 640CCA would be killed by running live bait tank / nav lights and sounder. You could run these all night and not have a problem because they do not draw much current. Upgrading the sounder will not cause you a problem either, so if you have gone thru two batteries, than you have a problem that needs to be solved to stop you having to buy batteries all the time. Check and make sure you do not have wing nuts, have water in the battery and nice clean terminals. On the outboard side make sure the battery charging system is up to spec and failing that I can not think of what would be causing your dramas.

Let us know what you find once you check your wiring etc,

Cheers,

Huey.

G'day Huey,

Thanks for your input. I am having the motor checked over later this week. What is the problem with wing nuts? I take it you mean used to attach the wires to the terminals.

Cheers

[Grebbo]

Hi Humesy,

I run a 500W Raymarine on a 16AH Deep Cycle battery that I got out of UPS, it’s the size of a motorbike battery more or less, I do this so that I don’t have to run it from the main batteries that run the electric outboard, I can run it all day with out any problems. It starts of with about 12. 8 volts and at the end of the day it drops to around 11.4 volts. I think your problems extends further then just running couple of lights etc on the battery, I would check if your cabling is in order, maybe there is a short somewhere which could lead to fire and you don’t want that

[a boat]

Hi Humesy, the problem with wingnuts is the become loose and not let good voltage get to the outboard and the opposite a good current goin back to the battery to charge it from the outboard. If the current has no where to go it fries the rectifier and that can be expensive on some engines. We see it all the time and on the more modern engines with EMM and ECUs it is even a bigger problem.

I hope you get it sorted at the place you are taking it to.

Cheers,

Huey.

[humesy]

Thanks again Huey,

I will check the wingnuts to see if they are loose. I don't think this is the problem as the last battery did not have the wingnuts. I suspect the problem is either in the wiring or the charging mechanism. Thanks to everyone for their input here.

Cheers