Voltages of batteries differ at terminals


  #1  
Old 09-27-21, 07:50 PM
Y
Member
Thread Starter
Join Date: Sep 2021
Posts: 1
Upvotes: 0
Received 0 Upvotes on 0 Posts
Voltages of batteries differ at terminals

Hello there, guys!

My front battery “NAPA Power no.65” 70 Ah, cca: 675 A, ca: 830 A, sits about 14.1-.6 at the front battery terminals while idling, while my d3400 starts around 13.1 and moves up to 13.5 while idling, according to the few times I’ve checked. I charged my d3400 with hf1215 last night and it was at 12.9 when I plugged it in.

2 1/0 runs: front battery -> dual fuse -> rear fuse holder -> rear battery, though the front to rear battery connection is unfused in the trunk. I just realized that I should probably fuse it. I have a smd fuse holder that functions as a bus on one side and can be fused to amps or anything else on the other. I have a total of three battery wires connected to the bus, so they should all be in good working order. My amps perceive the same voltage as my front batteries, yet at idle, my d3400 rises from 13.1 to 13.5.

The d3400 is set to 12.5 while connected to the system and the engine is turned off.

When linked to the system and the engine is turned off, the factory battery has a voltage of 12.3.

When bass hits strongly at the terminals, the voltage loss on the d3400 is modest. (Playing lows, it went from 13.6 to 12.6)

If none of this information is sufficient, I may supply more figures after the batteries have been charged overnight.

Finally, is this typical, or is there something wrong?
 
  #2  
Old 09-27-21, 08:51 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 64,928
Received 3,947 Upvotes on 3,540 Posts
Welcome to the forums.

Your primary battery sitting at 14.1-14.6 while running is normal.
Depending on how you connected (isolated) your rear battery from your front battery.... 13.1-13.5 is fairly normal. As the charge in the battery goes up that voltage could rise to match the front battery. If you use a diode type battery isolator.... then a .7v difference is typical.

Heavy duty battery cables (+ side) must be protected at both ends when interconnecting batteries.

Secondary battery at 12.5v when not running is normal and will slowly go down based on load.

I charged my d3400 with hf1215 last night and it was at 12.9 when I plugged it in.
That is a 15A three stage battery charger. Your secondary battery voltage should rise very fast and very high when first plugged in. I'd imagine a voltage of +/- 14v would be normal at first and then lowering during charging.
 
  #3  
Old 09-28-21, 10:56 AM
cheese's Avatar
Forum Topic Moderator
Join Date: Jul 2001
Location: USA
Posts: 15,972
Received 142 Upvotes on 131 Posts
What is this on and what is the application? This doesn't sound like a lawnmower or any outdoor equipment I can think of.
 
  #4  
Old 09-28-21, 11:29 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 64,928
Received 3,947 Upvotes on 3,540 Posts
Thread moved to automotive forums.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description: