Hi guys, gals. I have a 2005 dodge sprinter (t1n) 2500. I have converted it into a campervan. I have installed a renogy dcdc charger (40 amps). After 3 months of that, it killed my alternator. It was a 150A alternator. I have upgraded to a 200A alternator on the replacement process. Now, when i turn on the dc charger , i notice my engine acts like a generator? Think of a fat kid hyperventilating for example of what im referring to. And at night when my headlamps are on, they sorta dim and then brighten at a slow and very minimal rate. Its only noticeable if you pay attention very well. What could cause this? Did i wire my charger wrong? Or is there some other electrical problem going on here? All advice and help is appreciated. Thanks y’all
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I’m assuming you are running the charge line to the DC:DC / Iso in parallel to the vehicle starting battery?
Dodge uses/used externally regulated alternators, controlled by the vehicle’s modules/computers. The starting battery is a primary signal of the vehicle field, to control the output of the alternator. Adding the aux bank in parallel doubles the battery resistance/state of charge demand signals. Add in additional variables such as lights and HVAC, and the vehicle field sense can “cycle” up down like that, as it would to equalize the starting battery, if it were discharged.
Even if the alt max output is doubled, the vehicle itself is still based on that 100A alternator. Alternators are designed to only output up to about 60-70% of their max, for the specific vehicle. So that 200A alt is still “limited” by that vehicle system, only designed for maybe 60-70A constant current, for a few minutes at a time. So if you add up to 40A of draw from the DC:DC, the vehicle senses that load is over what the vehicle system is rated for. So it cycles the amperage down to reduce heat, then back up to equalize, relying on the starting battery as the uninterrupted power supply in the system.
In short, the vehicle doesn’t know that it has this auxiliary battery system.
How that system “talks to” the vehicle is another variable. Assuming Lithium with a full charge / no float duty cycle, that’s the draw the DC:DC charger is going to put on the system. Which, the vehicle’s lead acid system isn’t designed for. Dodge (and/or Bosch) systems in particular, which tend towards higher amperage/lower voltage can be difficult when adding to the stock systems.
How old is the starting battery?
Are you using the vehicle chassis as common ground for the house/aux system?
What aux battery type/size?
What gauge cable to the DC:DC, and are you running any breakers/fuses (of what amperage) in that line?
Hi! Thanks for the response. My batter is almost a year old. Will be a year in January. It is an Interstate MTP-49/H8 100ah. I ran the positive/ negative cables (2AWG 10ft +/-) from starter battery to dc charger. Positive has a 150a anl fuse. Havnt placed a proper breaker yet… from charger to “house” batteries, i have 4awg cables That are a hit longer, maybe 12 feet? To reach. Also have 60A anl fuse between. Is my gauge to small you think? Ive read that other t1n owners install dc chargers and so far its just been a plug and play… The difference i see between them and I, my D+ is tapped into a fuse and thats where i have my switch to turn “on/off” the charger. Instead of connecting to the actual D+ terminal under driver seat… Could that be a negative factor you think?