Starting Battery

[sailliny]

This question comes from my refrigeration question. I assume the people that have added a start battery have the two house batteries in parallel on let’s say position one (1) on the switch and the starting battery on two (2). My understanding is you start your engine and run your systems on your house bank (1) and save the start battery (2) for the times you have drained your house bank down.
My limited understanding is that you should not switch your battery switch while the engine is running. So I can start my engine with the start battery (2), but how do I get my house bank recharged? Since I am at a mooring and don’t have shore power hook up. Can I switch to (all) and start the engine with both the depleted house bank (1) and start battery (2)?
Thanks for the info.

 

[Witzend]

Check to see if while on 1, both 1 and 2 are being charged by looking at the volt meter when the engine is running. On mine, the alt. only charges the bat. bank that is active, so I just leave mine on both when starting and running. This has a potential problem, if you end up draining your house bat. and then switch to all before you start with the start bat. the start bat. is then getting pulled down from the depleted house bank and may not have enough power to start. IF you have depleted you house bank some what you may want to start on 2 and run a bit, then shut down switch both and quickly start again, but if it is hard down then you will have a problem. I don't believe our selector switches are make before break. I switched mine while the referig. was running and noticed a slight drop in motor frequency. The wiring on mine needs to be corrected so the alt. will charge both bat. regardless of where the selector switch is set.

 

[Tom J]

Most modern battery selector switches are make before break and can safely be switched while the motor is running, just never switch through the "Off" position while the engine is running. To be sure, check the battery switch. It should indicate whether it is safe to switch with the engine running.
When I first got my 310, I used to use the 1 batt as a house batt and the 2 batt as start. At anchor, I'd be in the 1 position. When it came time to start the engine, I'd switch to the 2 position and let it charge back up for 15 minutes or so. Then I'd change back to the 2 position for a while, and you could really hear the engine take up the load as it charged the house batt. If I was going to be motoring for quite a while, which happens a lot in the ICW, I'd switch to "Both" and keep both batts topped off. Every once and a while, I'd switch batts and use 2 for the house, and 1 for starting.
If you're considering adding a start battery, a worthwhile upgrade is described in the July edition of Sail magazine. It utilizes an automatic charging relay, in conjuction with a dual circuit battery switch. What happens is, the batt switch separates the house and start circuits. When you're at anchor, the house batts run everything. Then, when you start the engine, the start batt cranks the engine. Meanwhile, you haven't touched the batt switch, it stays in the "Normal" position. As the engine is running, it is charging the start batt. Once the start batt is charged, the automatic charging relay pulls in and starts charging the house batts in parallel with the start batt. Then, later, when you anchor, the ACR (automatic charging relay) opens, and you are running everything on the house batts. Everything is automatic, and the start batt is always charged, ready to go.
I installed this system on my 310, Andante, and it works great. At my age, it was easy to forget to switch batts, or which batt was the house batt the night before.
Whichever way you go, get that start battery installed. It's one of the best upgrades you can do for your boat.

 

[Witzend]

I have exception to the notion that our selector switch will make before break consistently due to my perception of the power being interrupted to the refrig when the switch was being switched from Both to 1. So switch at you own peril when running the engine. Better solve the bug in the design of the circuit by providing a path for the current from the Alt. to both batteries for charging regardless of where the switch is set.