Dual (different) Battery Question

I plan to add a second battery to my new system. I am going to leave the current stock one, and add a second to run the stereo. My question is... Can I run a gel and regular battery together, or will I have charging issues? I am not sure I am going to run a gel yet, but I would like to add a deep cycle battery of some sort. Any issues to keep in mind with two different batteries? I will be connecting them with a Blue Sea isolator.

No, not a good idea to run a Gel and Wet lead acid off the same charging source (as through an Isolator) The Gel cell has a different charge rate and the alt will leave the wet-cell under charged.

IMO, the only real advantage of a Gel is that it can be mounted on thier side. They do tend to take hi temps better tho, but don't have the Amp/hr ratings as high as a standard wet-cell deep-cycle.

Go with a god quality std deep-cycle battery with a high Amp/hr rating.

Choose an Isolator that is rated for amps higher then your alternator max output

^^^^ I agree unless you need to mount a battery on it's side or at a angle, gell cells are cost prohibitive.

Put a Perko switch instead of the isolator and you won't have a problem. Just don't charge them both at the same time. I don't know much about the gel's, but I would say go with the deep cycle as stated above.

perko switches require you switching them for them to work. The isolator set up in my opinion is a far better set up. you have a battery for the boat and one for your system and accesories. No switching involved and the isolator takes care of what battery needs to be charged.
I personaly think the biggest reason more people don`t use a isolator is due to the instalation is more complex. They do come with direction`s and if you have a little mechanical sence they are not that hard.

"the isolator takes care of what battery needs to be charged."

Not true, the alt will send the charge to both batteries. If one is run down low and the other is not the batteries will equalize...over time this will shorten the life of the batteries. and is not a good idea when running gel/wet together. Best setup is either a perko, or isolator or perko along with a combiner. Isolator alone is not ideal.

"Not true, the alt will send the charge to both batteries. If one is run down low and the other is not the batteries will equalize...over time this will shorten the life of the batteries. and is not a good idea when running gel/wet together. Best setup is either a perko, or isolator or perko along with a combiner. Isolator alone is not ideal."

Adam, Phillip is correct, your statement is incorrect about an Isolator. If they allowed a dead battery to drain a good one or equalize as you say, then they would not be called "Isolators". Each bank is protected by a diode the allows the alternator to charge each battery based on it's state of charge, but will not let current flow from a charged battery, such as the START battery, to the undercharged battery, such as the accessory battery, after running the stereo all day for example.

As stated earlier, it is not good to mix Gels and Wet-Cell.

I run a single STARTER battery and duel HOUSE batteries with an Isolator and a Perko. The only reason I have a Perko, is to switch over to the HOUSE batts if for some reason my STARTING battery takes a $h!!.

A perko is a manual Isolator, and an Isolator is an automatic Perko. They will do the same thing, just different ways.

^^^^^^ you are referign to an isolator/combiner.

A diode idolator is a terrible option for stereos b/c of the voltage drop.

A solenoid isolator is typically wired so that when the igniton is off the batteries are isolated, when the ignition is on the batteries are combined...it's a very simple device.

A standard isolator will not do the same thing as a perko. an isolator can only isolate batteries 1 & 2 and combine ( engine off/on) ...a perko allows you to isolate / combine regardless of wheather your engine is running.

Use the Blue Sea 7650 for combining batteries of different kinds it only connects the batteries when you starting battery is fully charged. This avoids your alternator having to work so hard to charge both batteries. The ACR combines the batteries at 13.0 volts and disconnects at 12.35 thus making sure your starting battery is full. The switch will allow you to combine the batteries incase your starting battery dies you can still start your boat to get home. They cost about $100.00 and are well worth the money. The also have not voltage drop associated with a diode isolator which is .7 volts. As stated above this will hurt you amps output. The problem with a solenoid isolator is that if you drain down your stereo battery completely is as soon as the solenoid combines (typically when key is on) the stereo battery will suck your starting battery down. The ACR will not do this.
http://bluesea.com/products/7650

Dual battery set up, check out www.ase-supply.com

Brandon,

Excellent post!

Credit also goes to Rod McGinnis (another electrical engineer) who uses this battery combining approach. I just completed my third trouble-free year with my system done exactly as you describe.

I have a perko switch, but it is the 2 position switch, for either on or off. All it does right now is allow me to turn off the battery while not boating. I think I could use it the same, just with two batteries. Do I really need a three position switch with the Blue Sea unit?

I to have installed my system per Brandon's post.

My 07 Supra is setup identical ( from the factory) to what brandon is referring to. They refer to the combiner as a VSR (Voltage Sensing Relay)

I have a perko that switches from battery 1, battery 2, both, or off completely. It works very well.

Where online can you purchase the Blue Sea products? And how hard is it to install?