well, i didin't asked to see if what you guys say , is correct.. i asked because you BOTH do exactly what a mechanic does. you make an extremely big deal, about something that really is a pice of crap! i dont mean isolators( wicch indeed are a great deal, solenoid or diode) but for batteries. ? Altarnators dont break down because of the batteries. Alternators break because they are from japan, and they suck ***.none of the cars i have been around (family or friends cars (many many cars) ) have ever had a bad alternator, and believe me , some of their batteries, are even 8 years old, and dont even support the lighting! every post i have ever seen related to power problems, you guys just go inside and swarm the **** out of it, about batteries in parallel or how to isolate them, without even giving the slightest input on how to solve the actual problem (telling someone to buy something is not help. ITS WHAT A MECHANIC DOES. if i wanted something bought, i wouldn't even need to be a part of a forum. i would just pay someone to do all the **** for me. )
AS FOR THE SAME OR NOT BATTERIES. god its so simple! every battery has an internal resistance. the internal resistance is a factor of its maker AND the history of the battery. that is what makes it different from another battery (at same amps).
if you connect to batteries in parallel, without any isolation, and they are different, its battery will see the other as a resistance and they will both get discharged after (allot) of time.
if there is an isolation, the loeads on every battery will be different anyway, hence CHANGING THE HISTORY, so even if you buy to same batteries, and the one runs the car, and the other the 8bilion watt sound sytem, after one year THEY WILL NOT BE THE SAME BATTARIES ANYWAY.