Battery Wiring Advise

[Grazer]

Hello fellow Brats,

I am upgrading my battery system from a single to dual battery (starting and house). Currently, I have a rather simple system consisting of the usual stuff lights, wipers, bilge pump, VHF, GPS, Radar and a Toyo cabin heater. I want to add a charger to maintain batteries. I have attached a wiring diagram below to see from the electrical experts on this forum if I got it accurate. From this I'll hopefully be able to order parts and install the system upgrades. I appreciate any and all comments or advise.



Cheers,
Grazer

[Aurelia]

I am no marine electrician but did wire my 25 to the gills with a flexible system. I later learned another way to approach the multibank system problem.

Consider a DC to DC unit to save you some trouble.

Check out the diagram on page 2 of this PDF

http://www.sterling-power-usa.com/library/ProCharge-B%20IP68%20B2B%20owners%20manual.pdf

Simply wire a quality AC charger of up to 30 amps to only your start battery (I use a 5amp), and your all set for dock recharge or charging while parked on the trailer. Saves you the need to switch anything as well.

[thataway]

Nice diagram. Some of us might do it differently. You have the electronics and engine start on the same circuit--not isolating the engine start from the house. You are then choosing what battery you will use that day...and not using the other one--as well as not charging it. There are perhaps some better ways with the use of the VSR. The "Sterling" adaptor may have some advantage for different types of batteries and in some setting such as charging trolling batteries, but not for the average C Dory user with similar batteries. (Lead Acid and AGM use close enough to the same voltage that they do not need a separate type of charge from the engine).

I might put the engine hard wired to the engine battery. Wire the house loads thru the 50 amp breaker to the house circuit and also fuse the heater (which you probably have although it is not shown on the diagram). Use a VSR to join the two batteries for charging. The engine will then charge the engine, and when the voltage reaches 13.7 volts it will join the two batteries. As the engine start battery drops below 12.7 volts, the batteries are disconnected (thus isolating the batteries when you are not running a charger or the engine). The battery charger can also be hard wired to both batteries, or alternately to just one battery (especially if you have a bi directional VSR).

One goal is to isolate the electronics from spikes, and lows from the engine starting. This will prolong the electronics.

[Grazer]

Aurelia,
Thanks for your thoughts. I had no idea that was even an option. So as I understand you, one can wire the motor to a start battery with an on/off isolation switch and then wire a "Sterling system" to your house bank. Run everything from your house bank and while underway the engine alternator will charge your start battery and in turn charge up your house battery. How then do you isolate your house from your start battery so you don't end up waking up to a dead battery?

Thataway,
In a previous thread you mentioned that it is better to go with an "old fashion" type of 1-2-both-off switch and that the VSR systems have a draw unless there switched from the battery. I may have the wiring schematic wrong but I believe the 6007 Blue Sea Switch is able to isolate the batteries as


I will only be using our boat for weekend forays (a couple of overnights with cruising and fishing in between). The boat will then be trailered and plugged in to maintain a charge on the system

[jkidd]

This is what I used in Voyager and it works very well.



Here's the wiring diagram for it. This is what Dr. Bob was talking about.



There are other brands out there that would probably work too.

[Aurelia]

The Sterling unit activates at 13.3 volts and protects your starting battery at a level of 13 volts while sensing constantly for any changes in the power coming into the starting battery either from your motor or an AC charger connected to your start battery. The connection from start to house is broken as soon as any charging stops so your start battery is automatically isolated upon loss of charging source without any manual intervention. A manual switch is not actually required to exist with the sterling.

The unit is fantastic for trolling motor batteries and even comes in 24 and 36v output models but the house bank on a small cruising boat is used just like a fisherperson uses a trolling motor. They draw from it for long periods of time while preserving the charge on a start battery and also needing to take advantage of the best possible method to get power back in those batteries when they move to the next location or need to extend fishing for multiple days without a plugin. Cruisers run accessories and heat at anchor and also need to run day after day keeping the house batteries as charged as possible.

One thing the Sterling does not do is allow you to do is manually combine the start and house to draw from the start battery for house loads. That is a delicate dance most would gladly avoid. Start the motor in that case and your back in business.

If you ever had a start battery total meltdown, you could simply jump the start from the house for which I carry a light set of jumpers on the boat.

AC charging:

I use a relatively simple 5 amp AC multistage charger connected only to my start battery which it turn powers the Sterling unit and charges the house bank at the same time. Your starting and house batteries can also be different sizes and types with this unit which is handy if you only need a regular cranking battery for starting but would like to use something bigger for the house, such as a nice AGM unit or two which you can safely keep under a seat in the cabin without worrying about gassing issues.

From the manual:
The Sterling Battery-to-Battery Charger constantly monitors the engine start battery. When the
starter battery voltage exceeds13.3 volts (which is usually the case when it is being charged) the charger
will activate itself. It will then start its charging operation during which the starter battery voltage will be
pulled down to no less than 13 volts. This enables the engine battery to still receive sufficient charge and
ensures that the alternator works at its full potential. The unit takes the 13 volts from the starter battery into
the control box and boosts it up to a maximum of 15.0 volts (depending on what battery type has been
selected) at the output. This will charge the secondary bank of batteries to their full capacity. The charger
then automatically calculates the optimum absorption time and keeps the voltage at absorption level until
the batteries are fully charged. After that, the system will maintain the batteries at a lower float voltage,
while always ensuring that the engine starter battery has priority.

It also de-activates itself completely when the charging source is lost so it will not run down the start battery with any parasitic losses.

[Sunbeam]

Since it came up in this thread, I just thought I would mention that I have re-wired my ACR so as to avoid the small parasitic load normally associated with it. Now, as we have determined previously, I'm no electrical expert, so I'll just explain what I did:

So, I found out and confirmed that the Blue Sea ACR draws a small (very small) load even when it's "off" when wired in the usual (?) way. The first suggestion I got was to put a small switch in the black wire that comes out the bottom of the ACR, then switch that off if I was going to be leaving the boat in storage and wanted the small load deactivated.

Well okay, but.... that just didn't thrill me. I mean, the system design is supposed to be sort of "hands off" except for turning the battery switch on and off (I have an "On-Off-Combine" from Blue Sea), so to add some other little switch that I have to mount, keep from accidentally getting bumped, and then remember when it's only an occasional thing, so not in motor memory.... well, I could just see it leading to one of those "Did I leave the iron on?!" sorts of scenarios. Or, more likely, it would go on a check list, but would annoy me every time.

I also wasn't sure exactly what type of switch, so I called Blue Sea. The tech fellow (very reasonably) stepped back a level and asked me what I was trying to accomplish. I explained. He agreed with my mission and listed three ways to accomplish it:

1) A small switch in the black wire coming out the bottom of the ACR, to be left on most of the time and switched off when I wanted to be sure there was no parasitic load from the ACR.

2) Re-wire the ACR so that it is switched off whenever I turn my main battery switch to "Off" (thus no parasitic load).

3) Wire in a solenoid so that the ACR is de-activated when I turn my ignition switch off.

Well, #2 sounded perfect to me. Simple and automatic, like I thought it would be in the first place (I don't mind manual systems at all - in fact I usually prefer them - but I really didn't want a hybrid). When I was on the phone with Blue Sea I didn't have exact information on how my system was wired up, so he didn't give me the precise way to rearrange the cables, just the concept. So I later called the person who helped me to set up the system (apparently there is more than one way to properly wire in the ACR) and he had me check a couple of things and get back to him, and then what I did was this:

a) Remove short jumper cable that ran from the Safety Hub to the ACR right side terminal. No longer needed.

b) Replace that cable with one that goes to either the #1 or #2 "cold side" terminal in the battery switch.

c) Take the cable that ran from the ACR to the battery switch already and move it to the #1 or the #2 "cold side" terminal in the battery switch, such that it's on the opposite one that the other ACR cable is on (i.e. one ACR cable goes to #1 cold side and the other ACR cable goes to #2 cold side on battery switch).

I'm awaiting the longer cable from step "b" but otherwise have this effected. As we know I'm no electrical guru, so follow this at your own risk, etc. I have not been able to test it yet because of not having the one new cable.

Sunbeam

PS: It did not occur to me at the time to ask how this affects things if I hook up a charger (I don't have one now, although I did just order a Battery Tender for maintenance charging). There may not be any difference, but I just don't know so I will check.

[Aurelia]

Nice work Sunbeam and I think you just reinforced my point.

I did try AC static charging through a VSR in the past and it did activate the relay to pass on some current to the house bank. How much? Hard to say. Did it over or under charge one side or the other? You bet.

122 bucks for VSR/switch from Defender plus add wiring
177 bucks for Sterling unit from Defender comes pre wired

Guess which one will save you time and trouble.

[Sunbeam]

[Aurelia]

You are on the right track for sure and I would not remove your current system either. Just learn to use it and enjoy the boat.

An AC charger connected to the start battery will trip the relay to the house if it is large enough to get the start battery above the relay trip voltage which is about 13.3-13.5 in most cases. So a tiny float charger may not even do it but a simple 5 amp unit would have no trouble.

Once the relay connects your start to the house, the charger will keep trying to charge the start while the house siphons off power to charge as well like some phantom load. This is good and bad. The good part is they are connected and sharing the power. The bad part is that the charger can no longer "sense" what either set (start or house) needs so it just keeps pumping or goes to float mode based on what it senses on only the battery its connected to.

This could be fine if you used batteries of the same size and chemistry for both house and starting as they would charge relativly balanced and evenly. However, that is not ususally the case so the smaller battery gets over charged while the larger battery is undercharged ignoring that the battery type could further increase this affect.

You are not likely to blow anything up with a small charger connected through a relay like this but it is not good for battery health and would have you buying more batteries prematurely. It would be safest to limit the duration of this connected charging or use your manual switch to break the connection and charge the banks separately while stored.

The DC to DC unit is a brain and charger sitting between your banks managing the health of both sides without the need for you to bother with details.

It is simply another option (better in my opinion obviously) to consider when looking to manage two banks of batteries on a boat or other vehicle.

[Sunbeam]

Thanks for explaining further - much appreciated. So here is a question:

Say I have my system set up like I do, that is:

1) A dedicated starting battery, AGM, "cranking" type, and smaller than the house battery. No parasitic load

2) A dedicated house battery, AGM, deep-cycle type, larger than the start battery. Both are the same age (now).

3) The ACR.

Okay, so when I use the Battery Tender 800, I think I will just leave the battery switch "Off" and just charge each battery independently. At any rate, it's such a minor charge that probably not an issue either way, right?

But let's say I get a 10-25 amp charger, one with two outputs that I could theoretically hard wire. I see what you mean about the ACR (just like the engine, but now we're talking dedicated charger not just alternator) passing current through the smaller start battery to get to the house battery. Apparently this doesn't seem to have the negative effect one would expect when just going through the alternator, but maybe it would with the dedicated charger. Or maybe one would just prefer not to even take the chance.

So.... here are two scenarios I'm wondering about.

1) Forget about even charging the start battery with the dedicated charger and only hook it up to the house battery. I mean, it should never really get discharged (just takes a short burst to start the engine, and then by definition it is being re-charged by said running engine), and AGM's don't really self-discharge much. The charged house battery could always be combined with the start battery to charge the engine if necessary.

2) Or, if that is not advisable, could one hook up the dedicated charger to both batteries and then use the battery switch to somehow direct loads?

Thanks again,
Sunbeam

PS: Instead of being a case of hijacking Grazer's thread, I'm hoping this info adds to the knowledge being sought in the first place (Grazer, just let me know if this is not the case!)

[Aurelia]

Thanks for explaining further - much appreciated. So here is a question:

Say I have my system set up like I do, that is:

1) A dedicated starting battery, AGM, "cranking" type, and smaller than the house battery. No parasitic load

2) A dedicated house battery, AGM, deep-cycle type, larger than the start battery. Both are the same age (now).

3) The ACR.

Okay, so when I use the Battery Tender 800, I think I will just leave the battery switch "Off" and just charge each battery independently. At any rate, it's such a minor charge that probably not an issue either way, right?

At 800ma, you are not likely to hurt anything but you also will have trouble pushing a full charge into your batteries if they are discharged significantly. That charger is really for keeping a full charge in storage and not for re-charging.

But let's say I get a 10-25 amp charger, one with two outputs that I could theoretically hard wire. I see what you mean about the ACR (just like the engine, but now we're talking dedicated charger not just alternator) passing current through the smaller start battery to get to the house battery. Apparently this doesn't seem to have the negative effect one would expect when just going through the alternator, but maybe it would with the dedicated charger. Or maybe one would just prefer not to even take the chance.

A larger AC charger connected to the start battery would overcharge the start to fully charge the house or if it was smart enough, would treat the start rather well while never fully charging the house. The relay is like a fence the charger simply cannot sense affective through

But if you wired lets say a two or three bank charger to your banks and manually disconnected the banks with a switch, it could do as well as the charger is designed for, providing each bank with what it needs.

So.... here are two scenarios I'm wondering about.

1) Forget about even charging the start battery with the dedicated charger and only hook it up to the house battery. I mean, it should never really get discharged (just takes a short burst to start the engine, and then by definition it is being re-charged by said running engine), and AGM's don't really self-discharge much. The charged house battery could always be combined with the start battery to charge the engine if necessary.

Sounds good and I agree if you have an AGM for the starting battery and don't have parasite loads in storage, it should last a few months without trouble. If your start battery is a traditional battery, I would personally keep a little float charger connected to it or at least top it off with a portable unit each month

2) Or, if that is not advisable, could one hook up the dedicated charger to both batteries and then use the battery switch to somehow direct loads?

Disconnecting the banks would allow charging independently as good as your charger can provide as I noted above.

Thanks again,
Sunbeam

PS: Instead of being a case of hijacking Grazer's thread, I'm hoping this info adds to the knowledge being sought in the first place (Grazer, just let me know if this is not the case!)

[Sunbeam]

I do realize the Battery Tender 800 is just for longer-term maintenance charging, but thanks for mentioning it. Now that I have the ACR in "non parasitic mode" I guess I probably don't really need the Battery Tender, since the AGM's don't self-discharge appreciably. However I ordered it before I got that all straightened out. For $33 it wasn't a big expense, but I haven't even opened it yet, so maybe I'll send it back and either go as-is or with a ~10-watt solar panel. I guess it depends on whether I'm more likely to have 110 or solar gain when the boat is stored.

I think that if I do get a "real" charger (say a 10-25 amp Charles or Blue Sea or the like), that I'll just hook it up to the house battery; but I guess I'll decide when the time comes.

Thanks again,
Sunbeam

PS: I did get a new AGM starting battery (because I wanted more CCA but it just so happened I also re-wired the ACR at the same time), so now I'm starting "fresh" and with no constant drain

[Grazer]

Jody,

I been looking at the BEP model you indicated and that does seem like a great option for me. It too provides both battery isolation as Dr. Bob indicated as well as electronic protection from starting spikes. I also like that the DVSP can be switched so as to provide no load during storage. Do you have an external charging system? If so, how is it connected to the system? Thanks.

Grazer

[jkidd]