charger or battery tender.

[8v fury]

I just recently purchased a XSPower d3100 for my system (it will be the second battery). I still have the main battery under the hood. Was wondering if I should get the XSPower Intellicharger HF1215, HF1415 or the HF1615 or get some battery type of battery tender. 

[Dragonsyph]

Wondering same thing, if it’s like 12v out of box can u just toss it in the car? 

Will the cheapest charger there is work for charging a d3100 or is ther a special type u need?  Because 250 dollars for an xs charger is crazy.