House Battery Bank Switch

[millennium]

I am installing a new battery bank(8 group 31 AGMs) and would like to have a shutoff switch if there is a electrical problem. The bank is fused but I want the positive control of a switch.

A conventional switch would involve runs of heavy cable and the voltage loss.

I am considering a heavy relay to use as a switch. Has anyone tried this?

 

[Keith]

http://bluesea.com/category/1/productline/407

 

[millennium]

Thanks Keith. Looks perfect.

 

[FF]

Switches have the ability to pass monster Amps during an engine start.

Solenoids with 2000A ratings will be expensive and still not reliable.

Buses have proper amperage knife type cut off switches that might be set up with a remote pull OFF cable , and manual reset.

You will probably fry the alt disconnecting a running engine , but it might be worth it ?

 

[FlyWright]

FF wrote:
Switches have the ability to pass monster Amps during an engine start.

Solenoids with 2000A ratings will be expensive and still not reliable.

Buses have proper amperage knife type cut off switches that might be set up with a remote pull OFF cable , and manual reset.

You will probably fry the alt disconnecting a running engine , but it might be worth it ?

*From the size of the bank, it sounds like a house bank, not a start bank, so the high current draw might not be an issue.*

Many experts advise that you connect the alternator directly to the battery.* If you do this, you won't fry the alternator when isolating the battery bank with the engine running.* If you need to stop the charge into the bank, you can stop the engine and remove the fuse.

 

[markpierce]

 

[RickB]

If you could start with a blank sheet of paper and draw that system plus show where and how to bypass a failed component it would be more impressive, not to mention more useful than a camera if you had a problem away from the dock.

 

[FF]

"Many experts advise that you connect the alternator directly to the battery. If you do this, you won't fry the alternator when isolating the battery bank with the engine running. If you need to stop the charge into the bank, you can stop the engine and remove the fuse."


A far simpler way is to use a better quality distribution rotary switch that has a field cut off built in.

It is a break before break setup, the field is killed before the switch shuts anything off.

KISS

 

[FlyWright]

Perhaps simpler for some, but not necessarily. And, according to my guy, not better.

After consulting my mechanic, I learned my wiring was insufficient to carry the current of my yet-to-be-installed 100A alternator. He feels that wiring directly to the battery is by far the best route to go. Since I was planning to add a battery monitor, it was far simpler to abandon the old wiring, eliminate the helm ammeters, and carry the charge via heavy cables directly to the batteries. I also installed separate start and house switches and located then in an accessible location out of the ER.

So my switches select load only and the charge never changes. I can turn off all loads and still charge my battery banks via the alternators. If one alternator or engine dies, the other alternator charges both banks automatically through the combiner. Fool proof and fail safe...just the way I like it.

 

[Tom.B]

What gauge wire would you use from 100A alternator to batteries? I have about 12' to go and this is the first thing I need to change out.

 

[FlyWright]

I'll have to look on the boat, but I believe it's either 2 or 4 gage, probably 4. My mechanic said I overdid it, but I feel better with a larger cable. GenuineDealz is a great source. http://genuinedealz.com/

 

[Per]

FlyWright wrote:
Perhaps simpler for some, but not necessarily. And, according to my guy, not better.

After consulting my mechanic, I learned my wiring was insufficient to carry the current of my yet-to-be-installed 100A alternator. He feels that wiring directly to the battery is by far the best route to go. Since I was planning to add a battery monitor, it was far simpler to abandon the old wiring, eliminate the helm ammeters, and carry the charge via heavy cables directly to the batteries. I also installed separate start and house switches and located then in an accessible location out of the ER.

So my switches select load only and the charge never changes. I can turn off all loads and still charge my battery banks via the alternators. If one alternator or engine dies, the other alternator charges both banks automatically through the combiner. Fool proof and fail safe...just the way I like it.

*FW, are you referring to the bluesea combiner switch? in that case it is not fool proof.

this switch isolates one bank if the voltage on either bank drops below 12.75 Volt and if you have been away for a few days or longer it doesnt take much to drop under 12.75 volt and then you "loose" the Amps of the other bank. Sure they will take charge but as soon as the charge stops, unless both sides are over 12.75 you only have the capacity of the one (house) bank. i ended up manully overriding the combiner in order to use some of the current off the engine bank.

I would consider to use the newer bluesea switch with the manual override option built in.

 

[FlyWright]

My system uses a Yandina combiner which is not as stout as the Blue Seas ACR, but I think the combining logic is similar. For the purpose of this discussion, let's assume a single engine with the alternator charging the start battery and the ACR between the start and house banks. The windlass is on the start bank and is only operated when the engine is running.

My understanding is that in a normal non-charging state, both banks are isolated and load on one bank cannot draw the other bank down. All house loads come from the house bank and all start and windlass loads come from the start bank. When charging is present and the start battery reaches a predetermined voltage indicating a significant charge (i.e. 13.0V for 90 sec or 13.6V for 30 sec), the ACR closes to allow the charge to be shared with the house bank. If, during charging, the start battery voltage drops below a predetermined level (12.35V for 10 sec, 12.75V for 30 sec) due to a high demand windlass operation, the ACR opens to allow the start battery to receive ALL of the alternator charge. In all cases, when the charge stops, the ACR opens and disconnects the tie between the banks, regardless of battery voltage. In the event of a voltage regulator failure and the charge voltage reaches 16.0V, the ACR opens to prevent overcharging of the house bank (note that this will not prevent overcharging of the start bank). The installation of an override switch allows you to combine or separate the banks at will, regardless of charging condition or battery voltage.

If your system is tying the banks together when no charge is present and you don't have an override switch, you might have something miswired. I had similar problems with my boat until I discovered the PO had miswired the battery switch which caused both banks to be paralleled when I selected bank 2. This caused both banks to draw down when I thought I was drawing only from the house bank. It took a while for me to figure it all out, but once I did and I replaced all batteries and recabled correctly, all has been well.

 

[Per]

it sounds like the logic is similar when a charge current is present on either bank however the bluesea switch combines both banks as long as the volt on either bank is > 12.75 volt.
i actually think this is a good feature and would have preferred it kept the "combining" down to perhaps 12.3 volt instead.

in many situations it is equally critical to have power on your house bank for stuff like communication and navigation.
if your house bank is isolated from receiving charge current, (your alternator current goes into the start/engine bank) then what..

 

[rwidman]

millennium wrote:
I am installing a new battery bank(8 group 31 AGMs) and would like to have a shutoff switch if there is a electrical problem. The bank is fused but I want the positive control of a switch.

A conventional switch would involve runs of heavy cable and the voltage loss.

I am considering a heavy relay to use as a switch. Has anyone tried this?

*

Well, the thread went off on a tangent and I don't want to get involved with that so:

You can use a relay and there are ones available.* Unless they have a mechanical latching device, there will be a standby current needed to hold the relay closed.* I like to reduce or eliminate any wasted current draw to prolong my time away from shorepower.

Why not use a conventional mechanical switch close to the battery wiring and just switch it when necessary.* It may be inconvenient, but if you're only breaking the circuit when there's a problem, you may never have to get to it.

*

 

[FF]

"You can use a relay and there are ones available. Unless they have a mechanical latching device, there will be a standby current needed to hold the relay closed. I like to reduce or eliminate any wasted current draw to prolong my time away from shore power."

The tried but true RV setup, the acc terminal on the engine run key closes the merge solenoid .

No lost juice ,the engine is on when the solenoid is closed, no thought required , a solenoid is $18. at the RV dealer.

Seamless , your brother in law could cruise the boat.

KISS

 

[PeterMcc]

A friend and neighbor lost his boat several years ago when his alternator shorted out. His wiring had the alternator wired directly to the battery as is being suggested here. He could put the fire out, but it would immediately restart as the entire house bank was being dumped into the shorted alternator with no way to disconnect it.

Cheers,

Peter McCorison

Stuck ashore.

 

[bshanafelt]

Don't forget to use a properly rated fuse when connecting your large house bank to either the alternator and/or panel to protect the wire.

I imagine the boat in Peter's story lacked this.

 

[Tom.B]

Wouldn't a fuse have as much of a chance of blowing and leaving no load on the alternator?

 

[FF]

Wouldn't a fuse have as much of a chance of blowing and leaving no load on the alternator?


You bet , a 100A alt will produce above 100A on start up so a 125A class T fuse would be a good investment.

Its a fine line , if the fuse nucance blows you will be purchasing new diodes for the alt,

too large a fuse and that fire will be happy to reignite.

 

[rwidman]

FF wrote:
"You can use a relay and there are ones available. Unless they have a mechanical latching device, there will be a standby current needed to hold the relay closed. I like to reduce or eliminate any wasted current draw to prolong my time away from shore power."

The tried but true RV setup, the acc terminal on the engine run key closes the merge solenoid .

No lost juice ,the engine is on when the solenoid is closed, no thought required , a solenoid is $18. at the RV dealer.

Seamless , your brother in law could cruise the boat.

KISS

If it's a house bank, the key would have to be left in the ACC position and there would be a current draw to operate the relay.

*

 

[millennium]

I am the origional poster of this thread. Thanks all for the input.

I just finished installing two Balmar alternators(twin engine boat), a bank of 8 agm batteries for the house,inverter, and about a hundred pounds of upgraded cabling.

I wanted the ability to disable all DC current from flowing if there was a electrical problem, those batteries and alternators put out a lot of amps. All wiring is protected by fuses and Cbs but I still want to be able to manually cut off supply. And be able to do so without entering the engine spaces.

I used the Blue Sea remote battery relay( http://bluesea.com/category/1/productline/407 ) as suggested here by Keith. I also installed switches in the alternator field cables to disable their output if necessary.

Probably overkill but for the cost of some switches and relays I think worth the effort.

PS The remote battery switch only requires 12v to open or close the relay.




-- Edited by millennium on Tuesday 13th of September 2011 06:46:13 AM

 

[FF]

If it's a house bank, the key would have to be left in the ACC position and there would be a current draw to operate the relay.

No the house batts are hooked to the house loads as normal.

The run position is what fires the merge solenoid when the main engine is operating.

The ACC position can be used in the slip to fire the solenoid to charge the engine batt from the house charger if needed.

When the merge solenoid is operating either the engine is on or the dockside charger is operating so 1/2 an amp is no problem .


-- Edited by FF on Tuesday 13th of September 2011 04:12:48 AM