Charging Batteries - Dual Batteries

[G-Mack]

I was thinking.... and I think I over thought this .... I have not read any manuals or other forums just started thinking

I have a dual battery set-up with a Perko switch. Say I was out on the lake and have the switch on Bat 1..... hanging out listening the stereo engine off and run Bat 1 down to the dead.

To start the boat....If I switch to 1+2.... will I surge the good battery with the heavy draw from the dead battery and cause damage over time or affect the starting of the boat?

or switch to Bat 2 to start the boat (seems safer option)... can I then switch from Bat 1 to Bat 1+2 while running to charge the dead battery... with the instantaneous switching affect anything ie a surge of voltage or voltage droop that could harm the electronics now that the key is on and the boat is running?

Thoughts on the best/safest way....

[Bobby Light]

I was thinking.... and I think I over thought this .... I have not read any manuals or other forums just started thinking

I have a dual battery set-up with a Perko switch. Say I was out on the lake and have the switch on Bat 1..... hanging out listening the stereo engine off and run Bat 1 down to the dead.

To start the boat....If I switch to 1+2.... will I surge the good battery with the heavy draw from the dead battery and cause damage over time or affect the starting of the boat?

or switch to Bat 2 to start the boat (seems safer option)... can I then switch from Bat 1 to Bat 1+2 while running to charge the dead battery... with the instantaneous switching affect anything ie a surge of voltage or voltage droop that could harm the electronics now that the key is on and the boat is running?

Thoughts on the best/safest way....

In either scenario you described your batteries will equalize. I don't think it will do any damage to them as you'll be giving them a charge after you start the boat. If the battery is a cranking or starting battery and not a deep cycle it can shorten the life of them. Those batteries are not supposed to be completely depleted.

[JerrysLSV]

In either scenario you described your batteries will equalize. I don't think it will do any damage to them as you'll be giving them a charge after you start the boat. If the battery is a cranking or starting battery and not a deep cycle it can shorten the life of them. Those batteries are not supposed to be completely depleted.

I have the battery isolator. You should have all the wires up there on the perko you need, one from the alternator, one going to bat 1, and one going to bat 2. You probly will need an exciter from the ignition switch to the isolator. I have no start battery discharge during setting with radio playing for hours, and the isolator picks which battery needs more charge and never lets them get together.

[Ndawg12]

I was thinking.... and I think I over thought this .... I have not read any manuals or other forums just started thinking

I have a dual battery set-up with a Perko switch. Say I was out on the lake and have the switch on Bat 1..... hanging out listening the stereo engine off and run Bat 1 down to the dead.

To start the boat....If I switch to 1+2.... will I surge the good battery with the heavy draw from the dead battery and cause damage over time or affect the starting of the boat?

or switch to Bat 2 to start the boat (seems safer option)... can I then switch from Bat 1 to Bat 1+2 while running to charge the dead battery... with the instantaneous switching affect anything ie a surge of voltage or voltage droop that could harm the electronics now that the key is on and the boat is running?

Thoughts on the best/safest way....

Just be very careful doing this, I've heard, but haven't found out the hard way, that if you accidently switch a perko to off while boat is running that you'll almost instantly fry the alternator...

[scfdfireman]

Here's an interesting article:

There are many switches, relays, solenoids, and other variations of

switches on the market that claim to be battery isolation devices.

This CANNOT be! IT’S THE LAW! These cannot isolate; they simply

disconnect one battery from the other when “OFF,” but reconnect the

batteries when turned “ON”. In the “ON” position the full battery can

discharge at an uncontrolled rate into the low battery. If the low battery

is substantially lower than the other battery, this current can be so high

that the wiring, plugs, and the switch contacts can overheat, creating a

possible fire danger. Many switches on the market will have stuck

contacts after only one such abuse…a serious situation when a family

believes that the auxiliary battery is disconnected from the cranking

battery and it in fact is not.

Another serious problem is when the engine is again stopped soon after

starting. The two batteries have been connected long enough to cause

the cranking battery to discharge into the auxiliary…a period of time that

is measured in seconds…and now the vehicle will not restart. This is a

common problem. If the auxiliary battery is low, the main battery WILL

discharge into the low one and the engine may have to be operated for

a considerable period of time before it may be safely turned off. Many an

engine has failed to restart because of this problem.

And here's a good article on ARC's- http://www.trailerboats.com/output.cfm?id=2457217

I just finished installing a second battery, on-board 110v charger, Blue Sea ARC and a Cole Hersey Battery Switch. I mounted the second battery above the stock one (on the backside of the hull), made a carpeted holder for the switch and mounted it to the compartment opening. It's easy to access and see...

[RTS]

Good information.

Having recently installed a second battery and Perko switch, I have given some though to what would be a good normal operating procedure.

I do not like being 'forced' to combine the batteries, however briefly, when switching from one battery to the other.

I think I am going to 'upgrade' to this switch so I will have the option to never have batteries combined. Then I'll just use one battery one day, the other the next, always keeping the battery from the last use in reserve.

Edited July 6, 2010 by rts

[scfdfireman]

That's what I used, but just another brand...

[G-Mack]

The set up we had on our old boat had 1 marine starting battery for the engine, one deep cycle for the house load (stereo) and a isolator... the set-up worked very well. The typical set-up in most boats is to use the perko switch.... so I assume the system is tried and true. If I ever leave myself stranded I will probably install the isolator to stupid proof myself. Agreed that a starting battery is not good for cycling but I don't want to toss a battery if it is still working. The comment on using the exciting lug on the isolator. Are the alternators self excited on our boats or externally excited (keep it clean) or does it vary?

[scfdfireman]

Forget using an isolator, use a Blue Sea Automatic Charging Relay (ACR). Many of the articles regarding isolators said that they produced heat since they operate by using diodes and needed to be mounted where there was plenty of air. This left out mounting it in the front compartment, also they said that the diodes reduced the voltage output to the batteries from the alternator. The ACR operates simply; when the main starting battery is fully charged it switches over and charges the second battery. The battery switch will easily allow you to isolate each battery if one is discharged...