Malfunction- ACR or operator

[Pagan Baby]

The other day I was setting up to flush my engines cooling system and connected the transfer pump to my emergency starting battery since it is easier to access from the engine compartment then the house bank. We’ll, I turn on the pump and no joy. Put a meter on the battery and it’s reading 7 volts, so shot. The house bank on the other hand was reading 97% on the SOC.
My setup is a house bank of 4 Trojan 6V, and a 12V group 24 “emergency” start battery. I have a 1,2,off switch for selecting and an on/off switch to the main positive bus. The positive bus goes to a blue seas ACR which is connected to the “emergency “start battery. (I’ll have to look for my wiring diagram). Charging occurs through a Magnum 30A charger/inverter. I had charged up the previous week with shore power to 100% SOC. I’ve been finishing up a major project so haven’t had the boat out of the slip since last fall.
I’ll be the first to admit that my “emergency” start battery doesn’t get as much love as my house bank - a lesson I will take to heart - since it is not as easily accessible as the house bank.

So my question is is this potentially a problem with the ACR, or more likely the result of malicious battery neglect by yours truly?

 

[Don S/V ILLusion]

Age of battery? Sometimes, batteries are killed; sometimes they simply die of old age.

 

[dlochner]

If the ACR is probably wired in place then it is probably either old age and a battery near it EOL or operator error.

An undersized fuse on the ACR to Start Battery may also be the culprit. If the start interrupt on the ACR is not connected when the motor is started the surge may blow the fuse. If the fuse is blown, the battery won't be charged. Best solution is to connect the SI circuit.

The operators errors could be simple, like accidentally switching to the start battery and running house loads which will kill a Gap 24 quickly benign neglect, like forgetting to water the battery.

 

[Head Sail]

Your problem represents what happens when you don't use your start battery to start. You won't know it's bad until you need it.