need options on battery project

[aitkenkingfish]

this is the delema I have twin engines & have been running 2 group 31 batteries. 1 for each motor & 1 gps fishifinder combo on each lights & pumps off 1 downriggers off the other. after some reading that is not the correct way. If I understand correctly I should have electronics on there own battery? I have several options since the power will be changing.

I will be running the odyssey extreme racing 40 batteries.

I could run

1 for the pair of 70 evinrudes

1 for the electronics 2 fishfinder gps units (can be run on 24 volt), led lights, nav lights, vhf, downrigger occasionally, livewell pump, bilge pumps.

2 for the 24 volt troll n tabs

or

1 for 70 hp

1 for 70 hp

1 for electronics

2 for 24 volt troll n tabs

any ideas?

[yottyboy]

There are several workable configurations. Generally, you should have a dedicated start battery for each engine and a house battery for all your other electrical needs. A trolling motor will add to this demand and a separate battery bank just for this should be part of the plan. That's a lot of batteries, and if you are away from the dock for extended periods, you need to be able to charge them from the engines. If you are simply day cruising and OK with using the house and trolling batteries until they are flat, you can get away with your simple system you outline above. NEVER use the start batteries for house loads. Only use the house battery to back up the start battery as an emergency measure.

The size of the battery will depend on how much electricity you will use per day. If you have the room, two 31s will be a very comfortable safety margin for most loads like FF, radio, and lights. If you add a stereo and fans and stuff then you might find you have flattened your house bank and the fun will be over.

If the 70 hp engines are equipped with alternators, you will be able to travel a little lighter in that the house bank needn't be so massive as it will be charged when the engines run. A single 31 will suffice along with a Yandina charge controller. There are devices available to charge the trolling bank too.

I don't want to go into too much detail without more info, but modern battery management systems will automatically charge all your battery banks from the engines without you having to be concerned that you have flattened your start battery. You no longer need a 1,2,BOTH,OFF switch for your batteries.

[Capt Rick Hiott]

Are you saying not to have battery switches Bill? I wouldn't have it any other way................

[yottyboy]

Are you saying not to have battery switches Bill? I wouldn't have it any other way................

Well, I don't use 1,2,BOTH, OFF switches in my battery charging systems. I use smart multi step voltage regulators and voltage sensing relays to charge from the alternators, so the house and start battery banks both get charged properly and automatically from the engines. I monitor the battery state with an ammeter and voltmeter at the helm station. At the dock I use a Charles marine two bank charger. No need for switches. They just add clutter and cabling.

I use Deka AGM batteries for both start and house.

In the remote instance of the start battery going flat (really really remote), I can simply swap the cable from the house battery to the power post for the starter.

Not saying not to use the 1,2, BOTH, OFF switch if that's what you like, just that I don't need them.

Edited November 2, 2009 by yottyboy

[Capt Rick Hiott]

So what you are saying is that your electrical system stays hot all the time?

What you have sounds complated and expensive. What would you do in case of a electrical fire? Do you have a main breaker that you could turn off?

(We are talking about small boats here right?)

Edited November 2, 2009 by Capt Rick Hiott

[Cracker Larry]

I agree with Rick. Every boat needs an "OFF" switch on the power, and everything should be wired to except the bilge pump. All dry stack marinas and many wet slip marinas require a battery switch due to their insurance regulations.

[yottyboy]

What you have sounds complated (sic) and expensive.

It's actually pretty simple to my mind. I just hook it up according to the directions and it works. Yes, I suppose it stays hot all the time. In case of an electrical fire I'll use a fire extinguisher!! There is indeed a main switch to kill power, but it is just a on-off switch. The boat is on a trailer when not in use. It's not cheap, no. The Yandina has a remote switch that allows emergency parallel without a dedicated 1,2,BOTH,OFF switch.

Smart alternator regulator: http://balmar.net/page17-maxcharge624.html

Voltage Sensing Relay: http://www.yandina.com/c150Info.htm