how do i hook up the 2nd batterey in 1999chev suburan v8

I fit is already set up with cables attached to everything but the 2nd battery just hook it up normal positive to positive and negative to negative.

Watch the video posted below copy & paste it to new browser window. It shows the parallel way there is other ways to do this with both charging but using only one at a time or using the other for say trailer light or just the winch or something or you can switch them and use one or the other but its not a normal switch on/off but on/off/on. The video is the normal way.

https://www.youtube.com/watch?v=dZzinsfI2Y0

Some believe this is bad for your alternator but its not true. The battery starts the car then the alternator quickly recharges the battery or batteries and runs the electrical system for the car to run including all accessories, a/c, fans ect so in real driving or engine running situations the alternator is not under any more load time and load time is reduced unless your run radio or lights or winch until they are almost dead but do start the motor up then it does have to charge up but it is the same as charging one battery and when with normal driving and starting the batteries do not discharge as far as one would and since they charge up with the same power as one would charge up coupled with the rebound rate of less discharged in the first place the alternator does not work harder but if adding a huge amp for your stereo system then you need to add a high output alternator or even a 2nd alternator. Having 2 batteries is best used to have more starting power or reserve starting power for when listing to radio and it would of drained just one battery or your in a cold weather situation and need more starting power. This can be tested with batteries set up in parallel when charging from a wall charger as the charger can use the same power to charge up 1 or 100 batteries.

Problems occur when 1 or more batteries in parallel have a dead cell or cells as the stronger battery or batteries will not be able to over come this and the output will always be the same as the weakest battery so all parallel batteries should be the same size, age and maintained and checked independently of each other and maintained the same condition.

You can however have two batteries of different condition and use them separately either by unhooking one battery when its fully charge and hooking up the other by the use of breaker switches or by removing the terminals from one to the other with quick disconnect terminals. Keeping a battery on standby.

I had two different size batteries once with my car which had a huge stereo system and I would run my stereo at times with the motor not running so if the larger amp battery (1000amp) ran too low to crank the car back up I use my quick disconnect terminals to unhook it and hook up to the less amp battery which was more then enough to crank up at 650amps then after cranked I disconnect it and hook back to the 1000amp battery to charge it back up and every so often I hooked back up to the 650amp battery to keep it charged for emergencies is what I did if the same size batteries are not used.

The breaker switch way is for mostly used when you want to have a way to do this inside the car and both batteries are hooked up but the extra terminal wires lengths for the each battery ground and positive are run to the cabin where you have each side +and- from each battery connected to the two breakers with two sides each with a on/off/on positions, while hooked to one battery at a time. Takes two breakers. both - wires to one breaker switch and both + to other breaker switch which each mount to their breaker switch one battery terminal on one side and the other battery terminal on the other side just keep one breaker switch for negative sides and the other breaker switch for the positive sides. So while hooked to the one battery you pull the negative to the neutral position and then the positive to the middle neutral position and then push the positive breaker switch to the other side and then the negative to the other side and now your using the 2nd battery.

With the breaker switch system you can pull the negative breaker to neutral to stop parasitic battery drains too and this can be done with just one battery too if there is a drain and its location is unknown or not fixed yet to save your battery power for when you need it and many people do this to stop a thief from stealing their car too and mount the breaker in a place that they know where it is and a thief will not take the time to hunt for it.

If your wanting to go the breaker route and can not find the 3 way breakers, they do cost a lot more BTW. You can use the on/off breakers just need 4 of them 2 for each battery. So basically same deal as above both are hooked up and both sides of each batteries terminal wires are put on breakers (each wire). When installing turn on all batteries terminal wire breakers to off position and then after install the battery you want to use first turn that batteries terminal wire breakers to on position positive first then the negative and to flip over to using the other battery just turn the battery that is on to the off position disconnecting the negative first then the the positive to the off position and then turn the other batteries breakers to the on position positive first then the negative and you are using the other battery. Basically when disconnecting from a battery always disconnect the negative first and when hooking up a battery always hook up the positive first.

And you can use the parallel way to run a trailer or winch or lights just like it is. Only difference is some actually mount the 2nd battery in the trailer or in a box beside the winch, you using both batteries at all time for everything. Its just that wiring for the accessory is hooked up to the 2nd battery and it is hooked to the first battery +to+, -to- and the first battery is hooked to the charging system and stater & ground.

Hope all this makes since and hope I typed it correctly as it was alot to try to explain and I will read it again later and see if I made a mistake or not and fix it or update if I did.

I will add that if your accessories are using more power than your alternator can put out or keep up with then it can over work (load) the alternator and cause to go bad faster, and all the above messages are intended to be used as a guide and under normal usage, know that you add more alternator output and or keep adding batteries for your needs, in other words if you have a high out alternator and its still not enough power either add another battery or a 3rd battery and/or a 2nd alternator and so on. If your pulling more power than you have or can make then those items & parts will fail faster as most will say pulling a load too long or all the time from an alternator will make it fail this is true in this case yes, but for normal usage with 2 batteries kept charged up it will not hurt the system but if your running big items that pull constant power like power inverters for your travel trailer and some one is back there cooking a meal and the fridge is on and all the lights on and some is taking a Hot shower then yes beef up the system or your going to be buying new alternators understand.