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hi  jeff cote here with uh pacific  outsystems we've got a question from a  fellow boarder for our ask pys  segment so here's a question and a  pretty common one  hi jeff i've got a stock alternator and  by the way most of us do  a lead acid battery for cranking and an  agm house battery bank  is it okay to install a battery isolator  well the  alternator undercharged the house agm  banks because there's no external  regulator  all right well first of all let's just  think about regulator  your alternator if it has an internal  regulator or external regulator can only  really charge  one profile so you've got to make a  decision are you going to charge  correctly your agm battery banks or are  you going to charge correctly your flood  to lead asset battery bank  you can't really have one alternator to  two things it can only charge to one  profile  so in this instance we've got an  internal regulator which is going to  charge the battery about to 14.4 volts  okay that's basically what its target  voltage is and that's a perfect  target voltage for a flooded lead acid  battery so putting a battery isolator on  the output of that alternator  is going to mean that the flooded lead  acid battery which is for engine start  is going to be getting the right voltage  because the regulator is actually  outputting for that battery  and the agm battery is going to be  chronically undercharged  because it's not receiving an agm charge  profile  it's important to remember that a  battery isolator is not this magical  device that can actually  regulate and change battery voltage it  doesn't get an input and say oh by the  way battery  starting battery 1 wants this voltage  and start  and house battery 2 wants a different  voltage it does not  modulate or change convert the battery  voltage for different type of batteries  it's simply spreading sharing right  the different battery banks to be  charged from one alternator so  ideally when we do this sort of systems  i always recommend to boat owners  especially if you're going to have one  alternator charging two battery banks  the easiest thing is to have all of agm  right  and because you want to have the best  sort of charge profile if you have an  agm battery bank  it's definitely better depending on the  manufacturer to consider an external  regulator so that your battery gets the  exact  exact voltage on a three-phase charging  curve  so that the battery lasts longer but you  can get away with  just having an internal regulator to  charge an agm it's not great but it will  work  it's just gonna chronically undercharge  the battery and that's where  a battery charger with the three-phase  charging is perfect  so make sure that if you've got a stock  alternator with a stock regulator  that you've got a compatible agm battery  charger to recharge your batteries  uh when you're not running the engine so  that's a really good question  thanks for watching this video if you've  got further questions that we didn't  answer  please ask them below or go on our  website and fill out one of the forms and lastly if you haven't subscribed to  our channel please do so that way you'll  get the regular contents and in closing  thanks for watching  you