2nd battery install ,couple of questions

[sfc2113]

I am planning on installing second battery using a selector switch but have a question concerning the ground, do I run a ground cable to each of the neg posts and connect the engine and acc ground to the starting or cranking battery. Or, do I install a buss bar and attach all the ground leads to it. And , should my batts be exactly the same or can I get away with 2 that are close cranking amps, say one is a good marine deka cranking batt and the other is a standard marine batt from sears.

The reason I am asking this is if I have the selector switch on "both" while running back in from fishing will it damage my engine charging circuits if they are not exactly the same.

 

[seasick]

You can run a ground from one battery negative to the second battery negative terminal. Just size the cable appropriately.
You can use two different batteries but they might not charge as effectively when in BOTH as when in 1 or 2. You should still be ok but make sure they are the same technology: lead acid, etc.
I am sure you know this but never switch the battery selector past OFF with the motor running. That can cause serious damage to the alternator/regulator.

 

[wanderer200]

If one battery needs charging and the other is fully charged, running on both will overcharge your full battery. To eliminate that you can install a battery isolator. Without one, its best to start with the full one then switch to the dead one once running.

 

[cdwood]

Be careful going from one battery to another while engine is running. Think you might be asking for trouble doing that.

Think I read that you can take out your alternator doing this.

 

[CJBROWN]

Be careful going from one battery to another while engine is running. Think you might be asking for trouble doing that.

Think I read that you can take out your alternator doing this.

The selector switch has a constant bus-bar from 1 to all to 2. No problems there for switching.

The rest of the advice is sound. It's really best to keep a good cranking battery in reserve, fully charged. A second charge circuit from the outboard is the best scenario to do this. Otherwise, run on the one that will deep cycle best and recharge it when shoreside and can put an electronically controlled charger on it. And if you don't have a second charge lead for your reserved cranker then monitor it's charge level and switch to it when running to keep it fully charged.

You need either a very accurate volt-meter or for lead acid types, a hydrometer. That way you can keep track of where you're at with them. You do have the volt vs. charge state chart on hand or committed to memory, right? The dash gauge is a poor substitute, but a rough indication nonetheless. I'm not even going to get into the various battery types, like gels, absorbed mats, and etc.

A starting/cranking battery will not survive long if deeply discharged very often, or left partically charged. It will end up with sulfated plates and cease to fully charge or hold a charge. If you disconnect your batts for storage and come back in a couple of weeks with a 50-70% charge left, you know its days are numbered.

An isolator is just a stop gap. It connects them when the charging ciruit is live, so a disparity in charge level or capacity can cook the good one as wanderer has said. Batteries can be grounded together, it's not 'till you connect the positives that they become joined in the circuit. That's why banks in parallel must be changed out/replaced in sets, like for like. Otherwise its not important as long as you keep them independent, individually or like for like banks.

EDIT: I was just thinking...I've seen a bad cell in one of a pair or parallel set and the good battery will get cooked from overcharging because of that one bad cell. I have also seen a bank of three or four where they replaced just one out of the set and boiled its water out and cooked it. They stand there scratching their head wondering why that new battery went bad so quick. The poor battery company gets left holding the bag. :cry:

 

[Curmudgeon]

Here's what I've done with every single engine outboard I've owned. I run two deep cycles (now AGMs) of the same size because they will start and deep cycle without damage. I start and run all day on one batt, maintaining the 2nd one as a charged reserve. I'll switch to #2 should the need arise (once or twice in 19 years), but go to BOTH only in a starting or communications emergency (hasn't happened, yet).

I think folks get too hung up on "cranking" and "house", and fail to size their electrical management system to the real needs of the boat. If you don't need separate banks because of heavy house loads, why interject that complication? I run a Honda 225 idle trolling for hours with a baitwell pump and 3-piece electronics operating (slight net amp discharge), and have used AGMs or deep cycles for 19 yrs without adverse issue. Even with multi engines there's often little need for overly complex systems. I'd create a system where I had at least one dedicated battery for each engine, a stand-by 'reserve' batt, and a way to connect and/or isolate both engines to any or all of the 3 or all (in an emergency).

Electrical system maintenance and monitoring is as important as fuel management for my single engine operation. I know what's happening before I leave home, and I monitor voltages through-out the day. Run the same type batteries, be anal about care and feeding, and you should only have to worry about something breaking, not disparate technology or unequal sizes or complex electron routing. :wink:

 

[BobP]

I think he will be ok switching batteries by going thru the both position while running, not the OFF position. Should be no breaks in circuit that way.

I don't think the two batteries will stay charged on motor alone unless running at speed for long durations, a battery charger may be in order.

With one motor you can connect the two battery neg posts together,and also add your other neg connects also, just be careful if you have to remove one battery from the boat and end up disconnecting a neg feed to something needed. That's why a bus bar is preferred, you have more terminals to use and the batteries tie into the bar separately, so removing one battery has no effect. Nothing else on neg battery terminal.

Blue Seas makes an assortment of bars with various size connections and some with various size on same bar.
I have several on my boat, some pos and neg.

 

[sfc2113]

I thank you all for your input. Good stuff.
I am definetly not looking to switch batts while the engine is running.. ouch.

But say If after a long day-night of fishing about 15miles offshore , I would like to start the engine in the both selection and run back in to charge them both at the same time. My concern was if the batts are not exactly the same would I be doing damage to the charging systems on the engine. But I think I would be better off just running on one and if it runs down just switching to the other. I always bring a jump box as well.
and theres always sea tow. But , at that far out if I have no juice I have no radio.
I think I am going to go with the bus barr. I think it would make it easier if I need to remove one without interupting the other devices grounds.

 

[wanderer200]

If this helps: I fish all nite sometimes into all day too. I run on batt 1 ( an agm batt crank/deep cycle) from start to finish on all my trips so far. I can stay at anchor all nite with anchor lite,cockpit lites,fishfinder,radio and always had restart in the morning. If batt went dead, I could switch to batt 2 (an 875amp lead/acid crank batt)and have a full charged crank battery. I could stay on that if I wanted or after start up, switch from 2 to both to 1 and charge the dead one while I run. If you leave it on both the alternator sends heavy charge for the dead one but also to the charged one as it is in line. An isolator is like a one way check valve and will cut off input to the charged batt preventing overcharge when more than one batt is in-line. My boat had three batteries, 1 crank and 2 deep cycles run through an isolator. I now run with what you have and got rid of the extra batt for weight reasons. I also don`t use the isolator. It`s fine switching batteries when running, just don`t go to OFF.
Buss bars are nice additions also, makes wireing easier/neater.

 

[BobP]

I don't think that motor is enough to fully charge two batteries at once, however, if and when you parallel 2 batts to make one bank, make them identical and same age.

If you use an isolator and run any two in parralel to charge, I would reserve one battery only for starting and the other for auxiliaries ths way the start power will always be there to get home. In this case the aux battery can be much larger with isolator.

If you use a lot or power, you may still have to use a dock side charger otherwise you may return and leave the boat for the week with less than fully charged batts, not good for batt life.

 

[sfc2113]

I picked up 2 dual purpose batts from west marine, they are actually made by deka, another question is do I need to use 2 awg cables or 4awg, they are going to be in stern under the aft seats and are only going to need 6ft cables to connect them. I am thinging 4awg will work fine to that distance. I think the engine cables are 4awg and they are 5ft long.

 

[uncljohn]

Do yourself a favor and install a bus bar for the negatve ground, and run ALL your negatives there (motor, batteries, electronics). Its much easier to spread your negatives out over 4 connections than trying to cram a bunch onto the 2 battery posts.

 

[SmokyMtnGrady]

ok, real stupid question here. I always thought when having multiple batteries with the factory installed selector switch that both batteries are being charged in any of the three positions? Is this accurate? Does the switch have to be on both to charge both? The batteries are wired in parallel, but I guess if the switch is set to 1, it isolates battery 2 for current going out, thus would isolate it for current coming in to charge. I typically run on batt 1 and have had dual batteries on my old 192 too, used the same practice with that boat.

 

[CJBROWN]

ok, real stupid question here. I always thought when having multiple batteries with the factory installed selector switch that both batteries are being charged in any of the three positions? Is this accurate? Does the switch have to be on both to charge both? The batteries are wired in parallel, but I guess if the switch is set to 1, it isolates battery 2 for current going out, thus would isolate it for current coming in to charge. I typically run on batt 1 and have had dual batteries on my old 192 too, used the same practice with that boat.

Not a stupid question, easy to assume they were thinking for you.
The selector switch does isolate the batteries from each other as indicated, 1, 2, or all. In the 'all' position your main charge circuit will charge both batteries, with caveats as mentioned prior.

The other popular configuration is with the auxilliary charging circuit that is an option on newer Yamaha outboards for a second battery. My assumption, as I don't know for sure, is that there is a secondary voltage rugulator for that circuit as well, to accomodate batteries at differing charge states.

 

[sfc2113]

Do yourself a favor and install a bus bar for the negatve ground, and run ALL your negatives there (motor, batteries, electronics). Its much easier to spread your negatives out over 4 connections than trying to cram a bunch onto the 2 battery posts.

Yea...I got a 4pos bus bar for the grounds, like you said why stuff the 3-4 neg ground connections on the batt post.

 

[SmokyMtnGrady]

So Chris, they only both charge when it is set to all? I have never had a battery problem, but this got me thinking.....

 

[SmokyMtnGrady]

Ok, read my manual. It makes no mention of charging batteries other than not to switch it off. It neither confirms or denies both batteries will be charged in either the 1 or 2 positions. They state rotate between position 1 and 2. One could assume the system is only charging the battery as indicated.

 

[SmokyMtnGrady]

Looking at the schematic provided by Grady on the pergo switch and battery configutation. On the 228, they have 40 amp main and engine crank coming to the switch. There are 3 12 v constants coming out of switch, 2 for bilges and 1 for constant, 10 amp. The grounds go to a common bus fed by battery 1, both positives go to switch.

They split the constants between battery 1 and 2. Based on the diagram each battery is only charged under both position or for the specific battery.