Battery charger and automatic relay

[brak]

If I have a dual bank shore power charger connected to two battery banks, and also an automatic relay (ACR) installed between the positive ends of both banks - would ACR close when charger is on? If it would - is that going to affect charger operation (meaning it will sense its own voltage on from another bank or some such?). Or is that not an issue for chargers (or is ACR smart enough not to close if it senses higher voltage on both sides)?

As a separate issue, at this point I have engine alternator connected to the same wire that goes to starter - which seems to be pretty common and saves on wiring. I am replacing two equal battery banks with one starting battery and one bank of deep cycle batteries. So now alternator will always begin charging the single starting battery first, until ACR kicks in. Is that an issue worthy of re-connecting alternator directly to the house bank?

[sailingdog]

The ACR has two voltage settings that are user adjustable.

The first is the threshold voltage, which it has to sense on the primary side to parallel the batteries. The second is the over-voltage level at which it stops combining the battery banks.

Chances are pretty high that if you have a shore power dual bank charger, charging both banks, that the voltage will be high enough to trip the second level and close the ACR. Mind you, I haven't actually tried this... so I can't say exactly what will happen.

I would have the alternator charge the house bank and then have the starting bank charge via the ACR. The starting bank, being smaller, will top off before the house bank does as a general rule.

[CapnHand]

It may be a problem or it may not, depending on the type of charger you have. Read this for recommendations: http://bluesea.com/viewresource/94

Regarding alternator hook up, I'm not sure why one would want to have the alternator charging the house bank first, leaving the starter battery partly discharged. The way I looked at it, I wanted to recharge my starting battery asap, so I connected the alternator to it. Once it is charged, the ACR connects to the house bank to start charging that.

[sailingdog]

Unless your boat has a problem starting, the amount of electricity used to start the engine isn't all that much, especially compared to the loads on a cruising boat's house bank. By having the alternator connected to the house bank, you keep them more fully charged than by connecting it to the starting bank. Also, there really isn't and delay in charging the starting battery, since the ACR will combine the banks within in minute of the alternator going on or so if it is configured properly.

[brak]

Thanks for the link about ACR and chargers. Charger on my boat is pretty old so I am sure it is not smart enough to do separate levels on two outputs, guess ACR won't do any harm then.

As far as moving alternator connector goes - from what I am reading here, I guess it is somewhat of a wash in terms of results. And in terms of work - its a hell of a job, because I'll need to route another fairly high diameter wire.

Plus, there is an additional connector spliced together with alternator output ring terminal, where they connect to the starter relay. I am not sure what it is for and moving alternator wire would require me to figure out (i.e. do i move it together with that wire or do I keep it where it is). Wire harness on this engine is extremely complex (and I also have alternator regulator connected making it even more so)

[CapnHand]

Originally Posted by sailingdog

Unless your boat has a problem starting.....

That's just it, do you always know if you're going to have a problem starting? Of course not, which is why I prefer to keep the starting battery fully charged.

Originally Posted by sailingdog

By having the alternator connected to the house bank, you keep them more fully charged than by connecting it to the starting bank. Also, there really isn't and delay in charging the starting battery, since the ACR will combine the banks within in minute of the alternator going on or so if it is configured properly.

There is minimal current draw from the relay (<0.2A) when its closed so if the last statement is true, then the statement preceding it must be false.

Is the last statement true? From the factory, my ACR was set to combine at 13.5V. Charging volts won't get there until the batteries are ~85% charged. So, unless there is a very small house bank, or a very large alternator, it could take some time (several hours) to get the house bank 85% charged to where the ACR would parallel the batteries and charge the starting battery.

Configured properly; how is that, exactly?