Perko Switch

[KamaSupra]

I had a question regarding hooking up two batteries with a Perko switch. I decided to buy a Perko switch with a 1,2, and all feature with no alternator disconnect. I purchased a 2nd battery (dual-purpose) to use for accessories (stereo, auto bilge, etc) and already have a starting battery for my main. My question was I asked someone that worked at marine store that I bought my perko switch and he said that it was ok to run the ground wire of the 2nd battery to the 1st battery so long as the 1st battery was also still grounded to the engine. This made sense to me and it was cheaper as the cable required is much shorter. However when I installed it this way I have been experiencing problems.

One thing that might be contributing is that the starting battery was a little undercharged but i started the boat using the 2nd battery and then while I was cruising a switched to all so i could charge both. When I tried to put the boat back in neutral it wouldn't shift easily and when I got it to shift into neutral the Voltmeter went from 12 to about 8 and the engine was making a really loud whining noise almost like it was running at a really high RPM.

Has anyone else ever heard of any issue like this or have any suggestions?

Thank you and I appreciate the help

[Mani]

I have the perko switch and have the same setup as you: Two batteries, grounded, one through the other, then to the engine block. Never had any problems because of the setup. I did have problems with a faulty alternator, but not the batteries, or the setup itself.

[saltare inverts]

You can have problems if you run different batteries. From what I understand they must be same brand size etc. The stronger of the two batteries will drain and ruin the other when on dual mode. I had it happen with a optima and a stinger. The optima sucked the stinger dead to were it wouldnt even recharge. Ok Ok it wasnt a stinger it was a Duralast (autozone), but it did kill it and the optima was 6 years old duralast was new. It may have something to do with being a gel cell and other not but I have heard of it happening with similar batteries just different brand age etc.

[KamaSupra]

Also normally I would turn the key to check to see how many volts the battery had and some times it engages the starter and starts the engine and then the engine makes the same noise where it sounds like it is running at a high RPM, so I quickly turn it off.

[Mani]

I hear that the solenoid disengaging problem is a due to low amps.

[KamaSupra]

Mani - were you running two of the same batteries? Two deep cycles? Or were you running a starting and a deep cycle as that is what I am using. Do you think that could be causing the problem? They are both the same size 24M the only difference is that the starting battery was almost completely discharged when I hooked it up.

[Mani]

No idea if two different batteries could be the problem. I'm sure Saltare knows more about that. Mine are both the same. Deep cycle dual purpose. They can be used as starting batteries.

The solenoids do stay engaged when there is a low amperage problem on the older boats like my 86 sunsport. It could be a faulty wire, bad battery, etc. Just process of elimination.

[rludtke]

Generally speaking, all grounds should be common to each other. The problem occurs when you engage both batteries with the switch, which effectively creates one large battery from the alternators viewpoint. One of the batteries was at a lower state of charge (voltage) than the other, which put a large load on the alternator. The two batteries want to equalize as well, which will, unless the batteries are identical make/model and charge, diminish the performance of the best battery.

I think the Perko switch will require some manual control on your part. You should not use the both setting, rather select the lowest charged battery. One way to do this is to feed one electrical system (or bus) from each battery. Starting with fully charged batteries, select battery one for the first start and run of the day, then switch to the second battery for the next strat and run of the day.this will allow each battery to start the engine and recharge. If any battery fails, you can select the back up.

There are devices that you can purchase that will allow dual charging of indipendant batteries in dual electrical systems. The device will switch the charging circuit back and forth between the two batteries until the large voltage difference goes away. These are common in motor homes. This prevents the problems you described.