Hey guys, I recently noticed my truck is putting out 16v at the battery and attached components. Is this potentially harmful in any way!? Everything is functioning normally thus far, but I didnt want to wait to find out if its a serious issue.

Only thing I can think of that would cause this, is my truck has 2 batteries.. It came that way when I purchased it. I recently directly connected the batteries together after I noticed the battery separator crumbling to pieces.. Thanks for any help guys!

 

You want to replace the battery isolator. Otherwise, the batterys will 'crossfeed' and discharge each other.

How did you hook the batteries up?

 

A battery isolator has a pair of diodes to stop the back flow of current between batteries.
Diodes cause a voltage drop (~1.8volts)... this is why there's a regulator terminal on the isolator, so the regulator sees the downstream voltage of the diodes and increases the alternator output to allow for this.
If a diode has failed, you'll get the increased alternator voltage at the battery (or no voltage).

Replace the battery isolator is my call also... double check for the correct wiring when installing the new one (it should come with a diagram).

 

I hooked the second battery right up to the primary, which may have been stupid on my end for not looking into it before hand... Right now both batteries read 16volts. I disconnected the secondary battery for now, once i get a new isolator will the voltage return to a "normal" reading? Thanks guys! Guess I'm lucky I didnt cause any serious damage

 

Forgot to ask, is there a special kind of isolator I should go for? I see there are many that handle different amperages. I probably dont need the 2nd battery to begin with, my extra componenets are essentially my sounds system and HID kits.

 

What is the second battery used to power?

 

I kinda answered that above already All my accesories are hooked up to my primary battery. I got two amplifiers, power inverter, and a flex a lite controller for electric fans.. Thats all the "extras" I got, HIDs are plug and play.

The 2nd battery has come in use when Im using my truck to light an area up, or listen to music with the engine off.

Should I be hooking the amplifiers up to the secondary battery instead?

 

There are two ways to isolate the secondary battery.

A diode based isolator.

This will supply charge to both batteries, whilst keeping both batteries and whats connected to them electrically separate.
This method, the regulator needs to know the diode downstream voltage to make allowance for the diode voltage drop.

Or solenoid based isolation.

A pair of solenoids (big relay) connected to the alternator, with each connected its own battery.
Both are triggered by alternator output (charging).
This method there is no voltage drop, so the regulator is fine.
Both batteries are connected together with the engine running, but are separate with the engine 'off'.
This can be bad if you drain one battery with the engine 'off'... there will be a big current rush when you start, as the two batteries try to equalize their charge.

I would have the basics on the start battery, and anything that is only 'on' with the engine running (T-fans for example)... anything that is potentially 'on' with engine 'off', put on the Aux battery.

 

Spillage, thank you for the very detailed post! I never would have figured that out on my own lol.

In what you described above, with one battery draining and having a potentially bad starting situation.. What could result of that? Is there a way of preventing that from happening?

I was possibly looking at something like this..

https://www.amazon.com/gp/aw/d/B001HBYXVS/ref=mp_s_a_1_3?ie=UTF8&qid=1468091484&sr=8-3&pi=SY200_QL40&keywords=battery+separator&dpPl=1& dpID=516f85YYu3L&ref=plSrch

..For my secondary battery. Would this suffice or, or would you recommend something else? Im guessing this is a solenoid isolator, as it does not specify. Thanks a bunch!!!

 

Yeah, that's a solenoid type isolator.