Small draw on starter battery

[skunther]

I’ve noticed that my starter battery will show a 0.3A draw immediately upon the fridge compressor kicking in, which quickly drops to alternate between 0.0A and 0.1A. When the compressor switches off, the draw becomes predominantly 0.0A, which an occasional 0.1A showing.

Obviously this isn’t a huge deal, but I’m curious why the start battery would show a draw when the fridge is connected to the house bank, and the banks are not combined.

 

[JoeWhite]

Could you show where you are noticing this current? Do you have a separate battery monitor for the starter batter?

 

[Don S/V ILLusion]

Probably some parasitic load which is always on but will draw more current as voltage decreases because the compressor goes on. You can easily ‘see’ it if you monitor voltage when the compressor starts. id bet both banks are combined by an ACR which itself draws some current to energize the relay.

 

[skunther]

Could you show where you are noticing this current? Do you have a separate battery monitor for the starter batter?

I’m seeing the current on my Xantrex battery monitor, which shows both banks.

 

[skunther]

Probably some parasitic load which is always on but will draw more current as voltage decreases because the compressor goes on. You can easily ‘see’ it if you monitor voltage when the compressor starts. id bet both banks are combined by an ACR which itself draws some current to energize the relay.

That makes sense. I have a Balmar Digital Duo Charge in place of an ACR. I’m not sure the passive draw, but it must be the parasitic draw I’m seeing. So you’re saying that the Duo Charge draws from both banks, and that the voltage drop on the house bank when the compressor turns on causes the Duo Charge to compensate by pulling more power from the starter bank?

 

[jssailem]

Yes that would be my guess based on what you stated.

It might be relevant to verify this conjecture.
Check the load on the house battery to confirm what you are seeing on the start battery is caused by what is happening on the house batteries.

 

[JoeWhite]

I’m seeing the current on my Xantrex battery monitor, which shows both banks.

i do not undersyand, if your battety monitor displays the battery condition for the house battery and the starter battery it must be when they are combined with the 1,2,both switch, how can you tell the condition of the starter battery only. Is the battery monitor switched also to house and starter separately?

 

[skunther]

i do not undersyand, if your battety monitor displays the battery condition for the house battery and the starter battery it must be when they are combined with the 1,2,both switch, how can you tell the condition of the starter battery only. Is the battery monitor switched also to house and starter separately?

The monitor has a selector for which bank to view. It shows one bank at a time, but you can select which bank.

 

[JoeWhite]

Thank you for clearifying, mine is the old fashioned type single display.
For a test, disconnect the monitor's connection to the house battery, also disconnect the starter battery cable from the battery switch. Then turn on the compressor and view the starter battery monitor. I will wait for the result of the test. I believe there is a low amount of leakage of current in the switch contacts.

 

[Benny17441]

Don't fix it, if it isn't broken. If your batteries are performing to your satisfaction forget about it. Many times attempting to diagnose inconsequential matters may lead to real damage.