12v draw from 24v batteries + Finder/gps

[Biff.McGerk]

Hi All,

I have been reading many posts and trying to find an answer to my wiring dilemna. There are many resources out there, but i can't find my exact answer or the diagrams to detailed for me to understand. I was hoping someone can chime in and recommend if i am going about my wiring correctly. There are a couple of different questions i will pose. Thanks for anyone offering help !

1. I know how to wire and connect up my NEW Terrova electric motor in 24v, no problem with that. I also know that i can connect my stereo and fish finders (anything 12v) off 1 or the other batteries as well. The question is is this the correct way to do this? it would probably draw 1 battery down and maybe lead to overcharging or problems in the future, at least that is what i was thinking. i know it will work, but should i be using an equalizer or some gadget that i can draw 12v off both batteries so that they drain equally ? maybe there is some gadget i can get that does this?

2. I heard that you shouldn't run your fish finders off your trolling motor batteries as it will cause interference. Is this accurate and can i go this route? I want to avoid hooking up anything to my crank battery or installing a fourth battery.

3. Previously i had a 12v minn kota on the boat and moved to the 24v motor. The main power plug in the boat is a circular plug with red and black going to it. their are 4 holes(2 on top and 2 on bottom) only the top 2 have the wires. The bottom 2 holes are empty. My question is do i need to change this plug for 24v ?

Thanks very much for the help !!!

 

[fucawi]

Re: 12v draw from 24v batteries + Finder/gps

getting 12v from 24 is always a problem ...Truck drivers use a converter to power the 12v goodies and these are quite high efficiency .....just put 24v to 12v converter in e bay for a selection.Note that 12v equipment is designed to work on 13.8v.
If you tap off the centre to get 12v you will as you say run one down first ...OK if you dont over do it and swop the batteries over for 12v duty each time you use the boat. If you charge them seperatly you will be re balancing them with each charge .

The idea of the 4 pin plug is that you feed 12v to each pair of pins and then when you plug in your trolling motor it connects it for 24v . you can also have another plug to put in so you can charge at 12v ( no link ) ...see my note in the post above on using your 24v motor on 12v rather than 24

 

[Silvertip]

Re: 12v draw from 24v batteries + Finder/gps

Low current draw accessories can be connected directly directly to EITHER of the two batteries. There is no charging problem. If all you connect is the locator/gps the batteries or the charger don't care and run time for the troller will not be significantly less. The bigger question is motor interference on the locator and even that is questionable. My personal experience is that my last five boats have all had the bow locator connected to the troller batteries and none of them ever experienced any interference issues. I might add that all of them have been Eagle/Lowrance. Furthermore, the console mounted locators never interfered with the bow mount or vice versa. If you connect to the troller batteries and have interference issues, move the wires away from the 24 volt system or move them to the starting battery. The starting battery would power the device for many days before it would fail to start the engine. My Eagle ice fishing setup runs for days on a 9 AH gel cell. Lastly, you do not need to change the plug for the troller. It doesn't matter if the plug has two, three, four or 15 terminals. You only need the two (+24 volts and ground).

 

[Biff.McGerk]

Re: 12v draw from 24v batteries + Finder/gps

Ok great answers and thanks to both of you for your quick responses.

So i have 2 D31M's in 24v. I also have a front FF and a back FF + a stereo. Do you think this is too much on 1 battery or should i split them up.

I created a diagram on how i think i need to do this.

thanks again !

 

[Bondo]

Re: 12v draw from 24v batteries + Finder/gps

getting 12v from 24 is always a problem ...Truck drivers use a converter to power the 12v goodies and these are quite high efficiency .....

Ayuh,... Havin' been around heavy trucks since the 70s,...
I can't think of Any heavy trucks that run a 24v system, other than a few old Macks, which were 24v Starters...
Those used a series/ parallel switch for the starter, but Everything else was still 12v...
Positive ground into the 70s, but still 12v systems...

Even in heavy equipment, Komatsu is the only thing I've run across in years, that run a 24v system...
Cat dropped the 24v systems Years ago...

I created a diagram on how i think i need to do this.

That'll work...

 

[fucawi]

Re: 12v draw from 24v batteries + Finder/gps

Trucks 24 v in the UK and much of the rest of the world

 

[Biff.McGerk]

Re: 12v draw from 24v batteries + Finder/gps

I missed the wiring in the diagram for the US2 trolling motor FF. Here is the updated one. Can someone yay or nay on this. Any suggestion on a better way to do this other than setting up a completely separate 12v battery to service the 12v electronics ?

thanks !

 

[fucawi]

Re: 12v draw from 24v batteries + Finder/gps

Thats fine provided its not an aluminium boat and you charge the batteries each trip to re balance them .

 

[Silvertip]

Re: 12v draw from 24v batteries + Finder/gps

That system is very dangerous for one very important reason. The jumper connection between the two batteries is ground for anything powered by the right side battery. It is +12 volts for anything on the left side battery.
. Guess what happens if you happen to have ANYTHING metal touch the chassis on devices powered by these two batteries. If none of the devices have a chassis that is at ground potential this is not an issue. However, it is very easy to lose concentration at some point in time and say I'll ground this device right here and -- well -- y0u let all the smoke out of the wire and there you are. Yes - the good thing is you can go out and buy all new electronics. Stereos draw little current unless you happen to have an amp. You also have the bilge pump on the starting battery which is what you are trying to protect. If it is an automatic type it can run the start battery down in your absence. I really hate splitting a 24 volt system like this - primarily for the accidental grounding issue but mainly because it is generally unnecessary. If you must power from the 24 volt system -- do it from ONE of the batteries. The batteries don't give a hoot and will charge just fine which is the job of the two bank charger. A standard marine radio will run for days on the start battery -- but add an amp and then that's a different story.

 

[Biff.McGerk]

Re: 12v draw from 24v batteries + Finder/gps

Ok i will have to remove those from the second battery (right side). I don't want to fry any of my electronics.

Short of adding a fourth battery and putting all electronics on it, are there any other alternatives ? what do most do? i am not certain i have enough room for a fourth battery anywhere in my boat. Also, i would have to buy another DualPro charger with 3 banks to replace the 2 bank one.

thanks!

 

[Silvertip]

Re: 12v draw from 24v batteries + Finder/gps

If your stereo is not a high power unit leave it and the console mounted locator on the start battery. The left battery in your diagram can have the bow mounted locator powered from it. You don't need a fourth battery. Not knowing what your fishing habits are and the thrust of your troller, it's difficult to say how deeply you discharge the troller batteries. Since they are group size 31's they are good size units and even if the engine didn't start, a pair of jumper cables would likely get it going from one of the troller batteries. We also don't now if you have an I/O or an outboard and what the capacity of the alternator is. A jump start box would also work for emergency starts if needed. The long and short of this is that you don't have a bunch of high current draw accessories. Four batteries are not necessary. If you frequently move from spot to spot the engine will put enough juice back into the battery in a short run to make up for what the radio and locator used. If the boat has a live well, install a live well timer so the pump doesn't run all the time.

 

[TerryMSU]

Re: 12v draw from 24v batteries + Finder/gps

Hi All,
2. I heard that you shouldn't run your fish finders off your trolling motor batteries as it will cause interference. Is this accurate and can i go this route? I want to avoid hooking up anything to my crank battery or installing a fourth battery.

Thanks very much for the help !!!

Not sure what you have for a fish finder, but (if memory serves correctly) Humminbird encourages you not to run the FF off the TM batteries. I know for a fact that I was strongly discouraged from running my 597 DI on the TM battery (also a D31M). Some trolling motors put out nasty interference on the power lines. I am not sure about the Terrova. Also check your PM as I am sending you a link that the fine people here on I-Boats are concerned might be competetive. (Sorry I-Boats, but I do buy most of my stuff from you for the great service and prices... YOU ROCK!, but that particular site has great info on TM vs. FF issues. Mods: please feel free to clean this up if it is over the line.)

TerryMSU

 

[Biff.McGerk]

Re: 12v draw from 24v batteries + Finder/gps

I found a device called the Battery Equalizer. It is used to get 12v from 24v or 24v to 12v depending on your requirements. This device is supposed to allow 12v to be taken off both batteries simultaneously and safely. Any one tried these?

Here is the blurb:

Battery Equalizers / DC Autotransformer

These versatile products perform many functions.

Sometimes a 24 V system is made up of 2 X 12 V batteries in series and a 12 V load is taken off of the one 12 V battery. This unbalances the voltage distribution of the 2 X 12 V batteries ultimately leading to the destruction of both batteries. These products maintain the voltage balance of the 2 X 12 V batteries preventing this unbalance and allowing loads to be taken off of either of the 12 V batteries in a 24 V system.
DC Autotransformers

These products have bi-directional power flow. For example the 12 / 24 V model will produce 12 V from 24 V AND can be connected backwards to produce 24 V from a 12 V source. Handy for driving a 24 V pump from a 12 V power source.

 

[Robert of Arabia]

Re: 12v draw from 24v batteries + Finder/gps

Most electronics will only require mAmps (500-600mA) to run so the current draw on a large battery will be minimal (unless the sterio is a high powered version??) If all your equipment is new (engine, battery etc) i wouldnt worry about this current draw.
If you are worried about interference while troller motor is running why not put all sensitive devices on starter battery and put bilge pump (& sterio too? most modern units have good interference suppresion) on one of the batteries in the 24v system (the 1st 12v side) As Silvertip suggest the wiring in your diagram can be dangerous if/when later you forget how you wired it up???
As for this device that convert 24-12v sounds like a head-ache... DC can only be coverted electronicly so this means this device will also use power from batteries causing a further current draw and may well cause more interference to your devices that you are trying to avoid???

R of A

If you dont need it on....turn it off!!!

 

[fucawi]

Re: 12v draw from 24v batteries + Finder/gps

Quote As for this device that convert 24-12v sounds like a head-ache...

How can it be a headache its just simple switched mode technology and if fitted will mean all the equipment on the boat is neg earth and batteries equally loaded....Them big burly truckers dont use them if they are no good .. Efficiency reaches 98%

The site refered to above is
http://www.solarconverters.com/equal1.htm

I dont think its the same as a simle 24 -12 truckers unit ..the site is 2002 and I dont see it being $25 like the truck unit....

 

[fucawi]

Re: 12v draw from 24v batteries + Finder/gps

oh yes Robert welcome to the site . have a long and happy posting time on here

 

[fucawi]

Re: 12v draw from 24v batteries + Finder/gps

just found it $248 ouch!

 

[fucawi]

Re: 12v draw from 24v batteries + Finder/gps

just found it $248 ouch!

 

[fucawi]

Re: 12v draw from 24v batteries + Finder/gps

sorry dont know what happened there ....

 

[Robert of Arabia]

Re: 12v draw from 24v batteries + Finder/gps

Hi again Biff...... look what you've started!!!!

Hi fucawi thanks for the welcome, i'll try to explain my thinking behind my post...

I've been tinkering with a friends boat and came across this site while doing some research on his engine.
I was impressed by the good advice and banana skins to avoid by many of the posters and decided to join the forum (my first i might add).
I'm also an electrical engineer and came across Biffs dilema and thought i'd give my thoughts on it...
Unless this device mentioned is designed to give a "clean" signal for this type of equipment Biff will be wasting his hard earned...248 of them...His system is already Negative earth.
I would also be interested in how this device converts 12V to 24V as this means it would have to be connected to a 12V supply? (his start battery maybe? this is something he's trying to avoid)
As for his trolling motor and batteries.. i guess they dont last all day ? so will need a charge when he returns back to land... so a small amount of "current" taken from one battery by the radio will be minimal over this period of time as both batteries will be discharging due to the troll motor running (unless his bilge pump runs continually?? Discharging it faster) I was only throwing some suggestions on the kit he already has...keeping it simple and saving him money!!!

Now.. if Biff wants to throw money at it?? What he is trying to avoid is probably his best solution!!! If he has room a second (slave) battery ? all his problems are solved...
As someone else suggested a small motorbike/dry cell battery for this equipment would work well (and wont break the back, bank or charge system) Biff could also connect it through a split charge relay to the start battery and he wouldn't even need to remove it for charging...and leave the troll battries well alone...
If he went for a bigger battery for the same application it could also be used as a get home if there is ever a problem with his starter battery and his troll batteries were flat??? This would probably be alot cheaper and easier to install than this device too...!?!

Let us know how you get on Biff...