Battery switch use?

[DougH]

Greetings,

I have a Perko battery switch in my boat that currently has only the main battery hooked up at this time.

My question is:

Could I run another set of cables to one of my 3 trolling motor batteries and hook it up to battery #2 on the (big red) Perko battery switch?

The switch is a big red round thing with a big black knob that allows one to choose from either "off", batt # 1, "all" or battery #2.

My thought is for a situation like this morning when I got to the lake and the big motor battery was basically dead cuz I forgot to put the charger on after last weeks tourney. The jumper cable to a trolling motor battery wouldn't transfer enough juice to start the engine. I had to actually unhook a TM battery and put the starting cables on it to start the big motor. Basically, a bad day from the get - go.

But if I could have just flipped the switch to "battery #2" I would have been able to start the big motor in less than 10 seconds. This would also be good insurance for the end of the day after running live wells , bilge pumps, electronics, and the such all day long on a weak battery.

Ya-ya, I know, just buy a good battery...

But, I want to know if there is any fatal flaws with the thought, and since I already have the switch, all I need are 2 short battery cables.

I should also probably turn the switch to "OFF" when not in use, as it seems there always seems to be a little bit of a draw from that old EFI...

Anyways, thanks for your thoughts in advance,

Doug

[scottsweet]

Yup...I have that in my boat...but as a separate switch.

Only one thing...be sure you use a battery from the end of the trolling motor batteries and the ground is right. You don't want 24 or 36 V. .

[DougH]

Hey Scotty, how are ya?

so to ID the "last" battery, would I just put my meter on each one till I get to the 12 volt one?

Now I forget how thse things are wired... I guess they are looped to get to 36v...?

[jimmy87]

each battery is 12 volts. they get wired in seires to = 24 or 36 volts. they are wired + to - like the batteries in a flashlight.

[blkdog812]

dont switch the battery switch while the engine is running or you will fry the motors electronics

[DougH]

hmmm,

So to switch from (Perko switch position) #2 back to #1, after the motor is started, would fry the EFI's electronics?

OK ! I don't want to do that I suppose.

So then to wrap this up;

TM batt #1 (+) goes up to bow to TM plug receptical
#1 (-) goes to Batt #2 (+)
#2 (-) goes to Batt #3 (+)
#3 (-) goes to bow to TM plug receptical

So which battery would I grab from for the remote starter battery?

Dang! this is confusing...

[scottsweet]

The best way is to use a battery at the end of the series. Based on what I am seeing below, I would use #3.

[DougH]

ok, a few more facts I have found.

Every battery in series meters at 12v, regardless of being connected in series. I'm guessing that the 36v doesn't happen until the trolling motor switch is depressed, thus completing the circuit.
I have no way of identifying which battery is #3 as the wires go "away", but I dont think it matters.

Of more concern now is that the PerKo switch, I found, is more of a "disconnect" of the (+) wire between the battery and the motor. The (-) battery wire just goes to the motor.

So, in order to do this, I would need to run the TMbattery (+) to the #2 battery post of the PerKo switch, and then run the (-) TMBatt to the (-) side of the big motor battery. And that is the scary part. I almost think I need to install another PerKo switch for the (-) wire too. And at this point, are we just getting a little bit silly? Unless I can find a different switch that includes connections for the (-) wires too...

THis is what I get for trying to think of a good idea....

[FATGUY]

I HAD A TWO BATTERY SYSTEM AND A SWITCH ..SWITCH WAS #1..BOTH #2.. FRIEND AND I REPLACED BOTH MY BATTERIES AND WHEN I WENT TO #1 THINGS WERE OK .I SWITCHED TO BOTH AND FRIED THE SWITCH . MY FRIEND HAD INSTALLED HIS BATTERY BACKWORDS!! SO AFTER READING ALL THESE MY SUGGESTIONS I WOULD BE TAKE IT TO A LICENCED MECHANIC!!!!!!!!!!!!!!!

[scottsweet]

Doug, you can't put it on any battery because you may not get the proper voltage because the other batteries are connected. When you are on the end of the series, you are getting actually 12V.

Please call me and we can discuss this further.
818-448-3366.

[bmshepherd]

I am wondering if you can have a perko switch with just on/off for a 24v system. I think i can but just want to be sure.

[kopper_bass]

Doug,
I would be concerned with putting a TM battery in circuit with your cranking battery because you'll be contaminating the (-) ground plane of your electronics with your TM and getting lots of noise\interference.

The perko switch is great kill power to a circuit and to switch batteries in the same circuit, but not to cross over from the TM circuit to the electronics/big motor circuit.

i would just stay with jumper cables.
if your original attempt to use the jumpber cables didnt work, you probably needed to let it sit a few minutes longer to charge up your crank battery before trying it.

Kopper

[DougH]

Final action:

I installed two new starting marine batteries, and left the trolling motor batteries alone.
Now I have a total of 5 batteries in the boat, and can run EVERYTHING full time, all day, and the big motor still has plenty of juice to start up. No funny switching, no cross connections, no grounding issues, no problems at all.

I had to do a little surgery and engineering to get everything to fit cleanly, but that's just a fun project for a retired guy!

Thanks for ya'lls thoughs, and Scotty especially,

fat dougie