battery and perko question

I have dual batteries with a perko switch, one is a regular car battery and the other is a deep cycle. I understand that the deep cycle is designed more for chilling and listening to the radio with the engine off but I hardly ever do that. I think I would prefer to be able to start off both batteries so my question is should I replace the deep cylcle with another starter battery? Also, the perko switch can be set to battery 1, 2 or both. If I put it on both will the alternator keep both batteries charged?

i ran 2 starting batteries and it worked just fine. both will charge if it is set on both

Yes as stated above when the switch is set to both the alternator will charge both batteries.
I would say that if you really want to stat off of both batteries then why have 2? You could just get away with one battery. Usually you have more batteries for keeping your starting and house banks seperate, or having a back up just in case. I would recommend that you while your driving leave the switch set to both. When you stop set it back to one. You could always add a Automatic Charging Relay. I would say thats it is alot "safer" to have a backup battery then it is to have a larger starting bank.

Yeah I hear you on it kind of defeating the purpose of having dual batteries if I go with two starter batteries. I guess since I don't really have much use for the deep cycle I was just trying to figure out the best set up to give me the added reliability. I go out on a fairly remote river and it is not uncommon to be several miles away from the ramp so I am kind of paranoid about getting stranded.

You can still start off a starting & deep combo no problem. You won't gain anything by going to starts.

Your deep-cycle will start the engine with no problem if needed. If the main starting battery is run down, or takes a crap, switching to "Both" will cause the good battery to try and equalize with the run down one. So just use position "2".

As long as you keep your batteries separate through the switch you have no need to go with two starting batteries (just more money). I was cautioned to not run around with the switch set to both. "Both" is for emergency starts only, ie neither battery has enough juice to start. There are a couple of issues running on "both", and I am by no means an expert. First since you are running two different kinds of batteries you run the risk of the batteries trying to level themselves out, but they are different so you can fry one of them. Also, and more importantly I think, running both to charge both at the same time is going to fry you alternator much faster, it is not designed to charge both batteries. You can get a auto battery isolator which will prevent this, but more money. I have the dual battery with the perko switch and I run half the day on one then half on two, keeps both batteries charged. I also usually don't hang out listening to tunes, but it is nice to know I can and still have a backup battery. Just my non-expert opinion.

Chris, how many amps do you have and what is the wattage on them?

The deep cycle I have wont start the boat but I think it might be bad. When I set the switch to 1 it has no problem playing the stereo and operating the blowers, pumps etc but as soon as I turn the key it clicks and everything dies, there is no electrical power at all from that battery after that. It has good voltage and I charged it just to be sure. I have an extra starting battery in the garage so I am leaning towards just putting that in there and then alternating between position 1 and position 2 every time we go out.

I just wanted to make a point about your switch. When you have the switch on pos # 1, only batt #1 is charging when the engine is running. Once the boat is started, if you do not put switch to both, both batts wont charge. Prob not your case, but after reading your posts it wasnt clear if you ever moved the switch to both , so batt 1 and 2 would charge when the engine was running.

Deep cycle should be fine as a starting battery. They usally have similar cranking amps as starting batts but are also designed to handle more cycles of discharge / recharge.

It sounds to me like you should just do 2 dual purpose RV/marine batteries. Then you can just leave it on position 1 most of the time while every once in while switch to both when the boat is running to keep the second battery fully charged. This way you are basically leaving battery 2 as nothing more than a backup. If you just leave it alone though without charging it every couple of weeks/months the battery will self discharge and you will end up with a bad battery or an uncharged battery that won't do you any good to help start. Keep in mind that if you are going to turn the switch to both while running that you make sure the switch is the type that makes the second connection before it disconnects the other connection. If it doesn't have this feature you risk blowing the diodes in your alternator.

I have the same setup.... Perko, one starting batter & one deep cycle. Plus a Guest on-board charger.
Somewhere I read this:

- Only charge in the Off position (using the on-board charger)
- If your going to sit & run your stereo for a while, turn the Perko to the 1 or 2 position that your deep cycle is on.
- And never ever change the Perko when the engine is running...... something about the spike going back up the line & frying the alternator?

Originally Posted by maxx_wake

The deep cycle I have wont start the boat but I think it might be bad. When I set the switch to 1 it has no problem playing the stereo and operating the blowers, pumps etc but as soon as I turn the key it clicks and everything dies, there is no electrical power at all from that battery after that. It has good voltage and I charged it just to be sure. I have an extra starting battery in the garage so I am leaning towards just putting that in there and then alternating between position 1 and position 2 every time we go out.

What was the before and after voltage?

Hope this isn't a hijack, but similar helpful questions:
1. I'm curious to get confirmation/clarification on what Bill Airjunky said:
- Only charge in the Off position (using the on-board charger)

- And never ever change the Perko when the engine is running...... something about the spike going back up the line & frying the alternator?

2. I just installed the following to support my new stereo system:
2 deka 31's for stereo (in addition to normal starting battery)
switch with "off, 1, 2 and 1&2)
Onboard charger
Isolator

When I start the boat up and drive around with stereo on, what setting should I have the switch on? 1 or 1&2? When I park with motor off I will switch to "2" which is just my deka's.

Brian, what is the point of the isolator if you have a perko style switch?

Also, when you say isolator are you talking about an actual diode style isolator or a voltage sensitive relay?

Good question Bill, I'm not totally sure...Mastercraft dealer installed it. It was my impression that it would assist in charging the batteries from the alternator?

Originally Posted by brian_b

Good question Bill, I'm not totally sure...Mastercraft dealer installed it. It was my impression that it would assist in charging the batteries from the alternator?

Is it an issolator or an auto combining relay?

it depends on the quality of your switch, but generally, It is OK to switch between 1. 2 or both with your engine is running. NEVER switch past, thru or too the OFF position with motor running.

as far as having a switch and an isolator, your dealer might have put the switch in so in case of emergency, you have the ability to combine or put the switch to BOTH batteries.

as far as what position you need the switch in while driving and parking, you need to know how you set up configured. Typically,an isolator is used so both batts are combined and charging when the motor is running, and seperated or isolated from each other, when the motor is off to reserve charge to re-start the boat.

Thank you, that is very helpful. Seems like my isolator is somewhat duplicitous, but I'd better find out exactly what type it is and speak to my dealer regards why I have it!