DC Battery Rig

[mtompson]

Thanks ex-calif, I haven't built this system yet so still very keen to hear ideas. I will have a good look at your idea, but more experienced people than me will need to comment. (I will try)
On the question of a dead short, I assume the battery fuse will protect the alternator? there is a lot to think about and will get back when I've had a think, thanks again.

[mtompson]

So thanks to the posts from auger01 & ex-Calif I have gone back to a very simple start point.

The ML ACR which as auger01 said, can act as an emergency bridge, looks very interesting? Anyone used one wired like this?

I have previously put the alternator feed onto the house battery post via an MRBF 2151 fuse, but if the house bank shorted (internally) & blew this fuse I'd have to move the alternator feed up to the bus bar anyway? thoughts appreciated...

(i'm leaving neg wires and other details off for now, while this rig is discussed)

[Ex-Calif]

Once again - in my opinion - if the house bank has a major issue there is no way to disconnect the house bank from the charging systems.

Putting the ACR upstream of the switches (where you have it) is not a problem because the ACR is in itself a switch and will isolate the batteries from each other based on the the battery voltages.

It also appears you have placed the alternator B+ on the house side of the circuit. I don't prefer that but it's not terrible. The questions is where you place the alternator field sense.

[mitiempo]

Originally Posted by Ex-Calif

It also appears you have placed the alternator B+ on the house side of the circuit. I don't prefer that but it's not terrible. The questions is where you place the alternator field sense.

B+ should go to the house bank. That is the bank most in need and it makes no sense to run that current past the start battery first. Field sense to house as well.

[mtompson]

Originally Posted by Ex-Calif

Once again - in my opinion - if the house bank has a major issue there is no way to disconnect the house bank from the charging systems.

I would hope the fuse on the battery would be that disconnect.

[mtompson]

Actually, if I keep all my wire sizes the same, I don't need the ANL fuses on the bus bar for the charge sources, voltage drop could be an issue going through them and a post MRBF fuse?

[Ex-Calif]

Originally Posted by mtompson

I would hope the fuse on the battery would be that disconnect.

Again a battery failure that results in an undervolt condition (i.e. shorted cells) would leave you trying to fill shorted batteries.

@ MiTiempo - No problem with that as long as the house is never shut off when the engine is started.

[mtompson]

Originally Posted by Ex-Calif

Again a battery failure that results in an undervolt condition (i.e. shorted cells) would leave you trying to fill shorted batteries.

But not if the post fuse has blown, I'm not sure if the battery short would always blow the fuse, but you would pick up problems via your battery monitor I guess.
Then switch the ML ACR to parallel until you replace the house battery.

[mtompson]

Here is a version with no ANL fuses on the charge wires, this assumes all wire gauge is the same. This may be too expensive a way to reduce small voltage drops!

[Ex-Calif]

I am not sure why this is getting lost - my fault.

Yes but then you still have a dead battery bank in line with your charging systems. The fuse will not always or necessarily blow. In fact in a shorted cell it likely will not blow. The bank voltage will go down and the ACR will not parallel.

If you manually parallel the ACR with a shorted house bank you are putting the good battery in a bad system. Again presuming the house fuse does not blow.

You will have to bring the ACR online in manual and disconnect the house leads from the batteries.

[mtompson]

Its not getting lost, I understand what your saying (so not your fault ). Its why I wrote: "I'm not sure if the battery short would always blow the fuse,"
I'm happy to move or add switches but need time to think it out, and discuss ideas with you guys ( which I really appreciate )

I still would like to be able to isolate my DC Panel from the charge sources but can see the benefits of putting a switch in between battery & busbar as you suggest.

If I stick with my method, and the house battery died but didn't blow the fuse, your right I would have to manually disconnect. I am assuming I would know to do this via my battery monitor. I like the Smart Gauge at the moment, and this has programmable alarms. Its even possible to drive external relays so that could be the switch in your favored position. I worry that starts making things too complex?

If it did die I would have to take my house battery(s) out at this stage anyway so I may as well start right away with a manual disconnect. A relay mentioned above could be good if your away from the boat?

[mtompson]

Added smartguage.

[mitiempo]

Originally Posted by Ex-Calif

@ MiTiempo - No problem with that as long as the house is never shut off when the engine is started.

Makes no difference if the alternator output (B+) goes direct to house bank positive. Never should be wired through the switch.

[Ex-Calif]

Originally Posted by mitiempo

Makes no difference if the alternator output (B+) goes direct to house bank positive. Never should be wired through the switch.

I think it is the field sense that you have to worry about. If there is no sense the regulator demands more output until the diodes fail.

[mtompson]

A few mods to this new design. Still be very keen to hear from anyone who has used an ML ACR like this.