How Do Batteries Charge with Deka Battery Isolator DW08771

Question:

Hi, I have a 1997 dodge B2500 conversion van with a 117 amp alternator. I would like to add a second battery to run a winch, lighting and stereo etc. Is it best to have the second battery be the exact same battery as the vehicle battery? If not would you please recommend a special type of second battery? If I use the Deka 120 Amp isolator will it always charge the vehicle battery first or will it always charge whichever battery is lowest first? If the winch is connected to the secondary battery and the secondary battery goes dead, Will I be able to run the winch just by starting the van or will I have to start the van and wait for the secondary battery to charge up before the winch will operate? And finally, does the alternator charge the batteries when the engine is idling or do I have to drive the vehicle. Thanks in advance for your help.

asked by: Matt

Expert Reply:

If you intend to wire the two batteries together they should be the same type but if you want to add a second independent battery for the winch/lights/stereo it can be a different type and/or have a different amp-hour (Ah) rating. A separate system means no risk of depleting your vehicle's primary battery.

You want to consider the power draw of each of the items and select a battery with a high enough Ah rating. The winch will draw much more power than the lights or stereo so that is the most critical item to consider in terms of power demand.

If you want a multi-battery set-up you can use the Deka Battery Isolator # DW08771 along with installation kit # DW08769. In a multi-battery system, the battery with the lower state of charge will drain power from the battery with the higher state of charge. This battery isolator protects your starting battery power so that no matter how weak your accessory battery becomes, the accessory battery will never drain power from the starting battery. This battery isolator also saves time by allowing simultaneous charging of both batteries. The amount of current flowing into each battery is determined by its state of charge, which guarantees that each battery will get fully charged, prolonging its life.

It is recommended that you purchase an isolator with an amperage rating above that of your alternator to prevent any damage to the isolator.

expert reply by: Adam R