Improved Battery (Bank) Handling

[SEMIJim]

Rather than continue hijacking Omatako's thread, I'll start anew. So, in response to Maine Sail's, mitiempo's and Stu Jackson's points...

Over in Omatako's Perko 4-way switch thread, I'd made a suggestion to which some exception. Executive summary: I want to isolate the start bank from the house bank using a Blue Sea Dual Circuit Plus battery switch. Some feel that's sub-optimal, because it doesn't give one the ability to use the house bank to start in the case of a start bank failure.

Very well. I'd hate to be thought closed-minded, inflexible or worse. (Tho the "worse" is probably inevitable .)

I will grant that the Blue Sea Dual Circuit Plus switch solution does have that one potential failure mode, and acknowledged that, up front, right off. Tho I remain highly confident that, with a quality (start) battery, properly maintained (which incl. replacement at appropriate intervals), that failure mode is highly unlikely, I will give it more weight.

So now I'm thinking that, at little additional cost over the BS DCP switch, I can do one of these



for the starting circuits (starter + ignition + automatic fuel shutoff solenoid + engine instruments) and one of these



for the "house" circuits. Plus the Echo Charge. The engine alternator output, like the shore power charger, would go straight to the house bank, and the EC over to the start battery.

This way I get the starting/house isolation I desire and the flexibility the three of you deem critical. (And I concede is not a bad idea.) I.e.: In the case of a start battery failure I can switch the starting circuit to the house battery/bank. In the case of an Echo Charge failure I can bridge the two batteries/banks by switching the starting circuit switch to "1+2." (I particularly like the Blue Sea switch, because it doesn't require that you switch through "1+2" to get to either.)

The only thing I'm not certain of is which is more intuitive: That each switch should be switched to "1" under normal operation, or that each switch should be switched to the right/clockwise under normal operation? I'm thinking the latter--which also makes the house battery/bank "1" and the starting battery "2".

Btw, Maine: We have had the GPS reset itself when we've been switched to "1" or "2" and started the engine. Our A4's starter really isn't all that demanding, and both batteries are new or nearly new and in very good condition. Switching those starters in and out I'm certain generates serious spikes.

Jim

[mitiempo]

Yes, it would work but I don't really see what the second switch adds to it. The first switch pictured will do all of the above without the added complication.

With all charging going to the house bank and the EC taking care of the start battery the first switch does everything. Start on either the start battery or house as you choose. Switching to any position including off is not an issue when the engine is running - exception being electric fuel pump.

[SEMIJim]

Originally Posted by mitiempo

Yes, it would work but I don't really see what the second switch adds to it.

Again: I want the house bank (well, battery, at the moment) isolated from the start battery. In this way the start battery is reserved at all times for starting the engine, and the instruments, etc. don't see any starting surges, sags or other starter-induced power artifacts.

Jim

[mitiempo]

I understand. I have never had a problem with electronics while starting.

[Maine Sail]

Originally Posted by mitiempo

I understand. I have never had a problem with electronics while starting.

I have not either but Jim does not have a house "bank" per se just a single house battery. Starting on a single battery can cause voltage induced drop outs.

With a properly wired multi-battery house bank drop outs are very, very rare on small aux engines. I have started our engine as low as 30% SOC and still not dropped a single piece of electronics. Most however are not properly wired so drop out can still occur. Bad connections, improper bank wiring, undersized wire, bad grounds and other glitches can all lead to a drop out.

We have been conditioned and convinced drop out is bad but I have yet to see it cause a "confirmed" issue. Nearly every single vehicle on the planet drops out "sensitive" electronics and they still work fine. For over 18 years I started my company cars with laptop computers plugged into the 12V socket on the front seat. Never had a computer failure but the charging circuit dropped out every time.

My buddies walk around fishing boat drops everything out multiple times per day when he starts. The electronics are now due to be replaced because they are simply outdated. None of them has died from drop out and he starts and stops that boat many times per day. The boat has radar, depth, speed, stereo, VHF. instruments, fish finders = 2, plotter etc. etc.. It is more of a PITA than anything else but he could care less about it. I've installed a combiner for him and tried to talk him into a wiring scheme that would prevent this but he's really pretty unconcerned.. When in the "BOTH" position it does not drop out but he wants to always save one battery for an emergency.

For Jim's situation, and drop out, his switch works for what he wants. I would simply add a second on/off and wire switch to tie the house bank to the starter in an emergency. This is an easy wire up. You would have both banks available to start the engine without needing to use the combine feature..

[SEMIJim]

Originally Posted by Maine Sail

For Jim's situation, and drop out, his switch works for what he wants. I would simply add a second on/off and wire switch to tie the house bank to the starter in an emergency. This is an easy wire up. You would have both banks available to start the engine without needing to use the combine feature..

The new design doesn't use a DCP. It uses a traditional 4-position switch for the starting circuit and a 2-position switch for the house.

Jim

[hellosailor]

Jim-
I would expect the GPS resetting indicates the starter is pulling the circuit voltage below whatever the GPS wants to see, a spike wouldn't normally reset a GPS, it would blow it out.
However, I think it was CreeX (one of the top producers of premium LEDs in the US) that published a "white paper" for automotive lighting designers, in which they said flat out that a simple automotive type starter and alternator WILL throw spikes up to 600VDC and commercial/truck applications will see spikes up to something like 2000VDC, and that their LEDs are specifically not warranteed for use in those applicaitons (i.e. tail lights, marker lights) unless the design integrates spike protection.
Yes, the folks with the fancy EE degrees are certain that starters throw spikes. If your GPS is not spike protected, it and all electronics should be off during engine starts/shutdowns.

Could be that your starter is pulling down the battery voltage AND that the wires powering the GPS are thin enough so that they're adding the final straw to break the camel's back, causing too much voltage loss in that low-voltage condition, but not in normal operation.

[SEMIJim]

HS,

As regards your last question: That's possible. Another thing on the To Do list (see Lucas' thread) is to rewire those bits of the wiring that need it. She's got some wiring that, while not down-right scary or unsafe, for how we use the boat, is not up to my standards and I wouldn't want that way out in the middle of an inland sea. Either way, tho, one way to obviate the problem of sags and spikes during starting is not run the boats electronics off the same battery/circuit that used for starting.

Jim

[Stu Jackson]

I'll say it again: It All Depends on How It's Wired.

So, to the OP's original question and followup, those "two switch" arrangements have been used successfully by many of our skippers. One fellow, who I worked with designing his system, particularly desired, wanted, insisted on the two switch concept.

His wiring diagram can be found via reply #5, here: Electrical Systems 101

His point was simple: whether or not electronics should, should not, or do drop out, for whatever reason, he found it disconcerting that it occurred when his guests started the engine when returning to their slip and the GPS crapped out.

However you wire your boat, you certainly should have a simple foolproof method of using your house bank to start your engine. This can be done with the simple 1-2-B switch wired as Maine Sail, Brian and I have been discussing, or the two switch method which also, you may cleverly note, includes a 1-2-B switch anyway(!!!). The DCP has that pesky illogical design flaw.

[SEMIJim]

Originally Posted by Stu Jackson

The DCP has that pesky illogical design flaw.

It all depends on how you use it. As Maine Sail noted: I could has as well accomplished what I wanted with the DCP and the On/Off switch. But that would've been Yet More Expensive, and I feel the two-switch design I propose more user friendly.

Okay: Nobody seems to see any down-sides to my design, so I think this is the way I'll go.

Thanks, everybody, for your review and comments.

Jim