D3400 or XP3000

[David Jensen]

Long story short, I was rocking a 600amp battery as my starter in the engine bay with a D3400 in the back, no isolator. Eventually the 600amp up front couldn't take anymore so I only have a D3400 which I now use as a starter battery up front. I have a DC 15" and Sundown saz1500, unfortunately with only the D3400 it causes a lot of stress on the car and the headlights dim, etc... Considering the prices of the D3400 and XP3000 are similar, would it be recommended to get another D3400 and keep them the same voltage, wired up together with no isolator, vs purchasing a XP3000 in the back, with an isolator (I assume)?

Big 3 already done, 160amp alt thanks. 

[Mr DeeBeez]

You would not need an isolator if you ran d3400 and xp3000 together. I run a d3400 up front, and 6 xp3000's in back. Many others also use these batteries together.

I would recommend the xp3000 if running it in back. much higher reserve capacity. Only reason not to run the xp3000 under the hood would be because the case is not designed to withstand the heat of an engine bay. 

[David Jensen]

Without an isolator wouldn't the eventually XP3000 eventually damage the D3400 and constantly be sucking juice from it? 

[SkarredSierra]

No. Those two batts should be close enough on resting voltage to not harm anything. Isolators are only needed if your playing for long periods with the car off. Also the only thing it would do is lower the voltage in the higher batt to wat the lower one is. It can also shorten the higher batts life over time from wat ive heard but ive had a standard lead acid up front with a small agm in back for years with no isolator with no issues.

[Mr DeeBeez]

12.9 and 13.1 would be the difference between the batteries. That .2 won’t do any damage to either battery. I know many people who run these batteries together with zero issues. 

Your issue with battery resting voltages comes from running agm and wet cell batteries together with long periods of time with the car off. There is a much bigger gap between lead acid batteries and agm. 

Again, there is no need for an isolator with an xp3000 and a D3400. 

[AlpineNut]

I have a duralast battery under the hood and a Reikken PB1600 in the back to help the system and its been like this for almost 2 years now and I have not had a single issue what so ever!