Help with inherited dual battery setup

[richard2234]

Looking for some advice

Some background first…

I’m a first time boat owner, a 1999 Cruise Craft Rival 5m runabout with a 1999 115HP 2 stroke Yamaha. The boat has a dual battery system and I replaced the cranking battery with a Century 730CCA 100Ah (Wet cell Flooded) at purchase in Dec 2016.

I have purchased a Ctek 5amp smart charger which I have recently used to recharge the cranking battery out of the boat (all 8 step process okay). When a tried to recharge the deep cycle battery the charger reported an error at step 5, meaning that battery won’t keep a charge and therefore needs replacing. So the deep cycle battery (Century N70T 100Ah wet cell flooded) has now died and I will need to replace it.

I’m not techie minded and it was worrying me that I didn’t really understand how things were wired up in this system and how I should manage it on the water, particularly now that I wish to venture outside for some in-shore coastal fishing (not too far out). So I bit the bullet and got down and dirty in the back of the boat to see how things were connected. I have now documented this as best I can in the wiring diagram I have attached to this post.

My questions are:

1. Can I replace the deep cycle battery with an AGM type battery and therefore mix battery types in the dual battery system, one wet flooded and one AGM? (My research seems to suggest that there are some advantages to AGM including no risk of acid spills, no maintenance beyond recharging, quicker recharging, and hold their charge longer during periods of no use)

2. Whatever type of replacement battery I choose I'm thinking to replace the deep cycle with a dual purpose (cranking and semi cycling battery) which might offer better redundancy on the water if my cranking battery unexpectantly dies. Any thoughts?

3. Can I use my Ctek charger to recharge the batteries in situ (wired up in the boat) either one at a time or both at the same time with the existing wiring setup? What is best practice?

4. Does the dual battery wiring setup (main cable connections between batteries, isolator switch and motor) reflect a standard setup that reflects good practice for such a system? (I need some confidence that everything is as it should be!)

5. How do I manage this system on the water so that battery health/capacity is efficiently maintained for a day out of stop/start cruising with the family or a longer run out to in-shore coastal fishing spot?

Hope you can help.

[kingfishbig]

It's probably best not to mix chemistry types. As to charging, yes you can leave them in the boat, just try to keep them ventilated (eg hatches open). Charge one at a time with the isolator switch in the off position. And yes I would have 2 cranking/ general purpose batters of a suitable size for your motor.

[Guest Guest123456789]

Did you check the water levels in the n70T? Should be just touching the plastic. You need to use demineralised water. It might be the last owner used tap water and this could have caused corrosion.

i have the N70T for my electric and I top up the water bi annually using demineralised water. Had faultless performance over 3 years.

its arguable but the research I have indicates lead acid batteries will outlast gel (as we as being cheaper to buy). 

[Sigma]

@richard2234,

Did you want to keep the same set up or did you want to improve it?Noticed that you don't have a VSR (Voltage Sensitive Relay) on your boat. 

Maybe have a read of this article where we discussed dual battery set ups and then decide what you want to do.

I love my set up as it's all automated and no flicking of switches between battery 1 or 2...only on or off.

Cheers

Dave

 

[antonywardle]

HI

 

I think we have about the same setup.

From how you've got it wired, you would set the battery switch to two when you start the engine and then when running you might change the switch to both to charge them both and then when you stop the engine, turn the switch back to 2

Looks like a reasonable setup. As mentioned above, consider getting a VSR. That connects the batteries together and it will chage the second battery (deep cycle) when the starter battery is full, which means you've never need to change your switch from 2.

If you want to replace your deep cycle, then I would stick with a deep cycle. You can use this to start your motor too, but maybe consider taking a small portable jump starter as well. 

 

Yes, you can charge your batteries on the boat. That is what I do. I actually, take the lid off my outboard and connect my charger to the the plus and neg terminals, and then this will charge which ever battery the switch is set to.

Q4, looks to be a standard setup and other than the VSR, I think it looks fine.  One thing though,  you should probably fit a fuse between your deep cycle and the stereo system. 

 

Q5, The night before, put your batteries on charge, then start on number 2, and when running, switch to both, switching back to 2 when you stop.

If I'mnot too clear on anything, feel free to ask, you'll probably find @zmk1962 will pop in with a comment too

Nice look boat!

 

 

Edited December 28, 2018 by antonywardle

[richard2234]

Thank you everyone for your comments, they help me build some confidence that things are basically okay with the setup (but maybe add a VSR) and I can manage the isolator settings to preserve maximum available capacity on both batteries.

One clarification please, the advice includes switching from battery 2 (crank battery) to battery 1+2 after starting the motor. Is it okay to switch like this when the motor is running?

Also, if I'm underway with a 1+2 setup this presumably means the current draw from equipment (instruments, radio, sounder, GPS plotter, etc.) is being shared equally across the two batteries AND similarly each battery is sharing the alternator charge offered by the motor and the net diff between charge and consumption means that each battery is slowly increasing capacity back towards a full charge capacity. This would mean that the cranking battery takes longer to restore to full capacity than if the isolator is on battery 2 only. Have I got this right?

 

 

[kingfishbig]

I wouldn't switch when the motor is running. It doesn't do the motor any good cutting off the electrical supply. This will happen if you inadvertently go through the off setting. I'm not sure about going through the both setting but I would play it safe and only switch when the motor is off.

[antonywardle]

The 1 , 1-2, 2, off switch says on it not to turn it to off when the engine is running. I believe that it is OK to switch to 1 or 1-2 or 2 when the engine is running though, just don't click through the off position.

Yes, when set to 1-2 when running your alternator will be charging both batteries at the same time. Usually the starter battery will take longer to charge, depending on how long it took you to start the engine. I guess when the engine is stopped, then if one battery is less charged than the other, it will steal charge from the better battery, so try to remember to change this when you stop.

This is where the VSR is really good. For me, I'd much rather be able to start the engine than listen to the radio, so I always leave mine on 1 (my starter battery), and when running and it gets full, the VSR will then allow charging of the second battery. 

cheers

Edited December 28, 2018 by antonywardle

[zmk1962]

Hi All, just catching up on posts... been very busy with work and getting things in order before an overseas trip. 

I thought this topic brought back memories of a deja vu discussion... and sure enough @Sigma had quoted that post - I just reread it and boy did we cover a lot of ground - just about every eventuality. Thanks Dave, I think that post is at a level where it deserves to be pinned !

So applying some of that discussion to @richard2234's set up -- 

This is a classic 2 battery set up. It will work, nothing basically wrong with it, but its probably most important that @richard2234  understands its limitations.

There are basically two reasons why you have multiple batteries -

1. redundancy (to ensure you can power essential services - start motors, run Nav lights. If you are offshore I would also add to this essential services list - bilge pump, VHF radios, GPS - why GPS? well basically because the first questions you get on the radio are identify yourself and what is your lat/long location).  

2. capacity (to ensure you have enough electrical power on board to run all the gear that you want to for as long as you want to. In essence this is the easy consideration as it just a matter of calculating the combined current draw of all the devices you run simultaneously and how man hours you want to run them for - then ensuring you have a battery or set of connected batteries big enough to handle that load).

@richard2234 I understand from your post that you want to start venturing offshore (not too far out). To me that puts you in the offshore category regarding powering essential services eg  you would be in more danger 100m offshore drifting toward rocks with a dead battery then being 10km offshore. Offshore is offshore.

In your set up, the battery switch mainly controls which battery will be used to start the motor and which battery will get charged from the running motor.

All the electronics are hard wired to run off battery 1.  Battery 2 is dedicated to being a start battery.

If you analyse your set up from a redundancy perspective.

Battery 2 dies, you use the isolator switch to swap over to battery 1 and start the motor - but you have to make sure battery 1 has sufficient charge. So with all the toys running off battery 1 you could end up with insufficient charge to start the motor (my EFI motor needs minimum 8-10V run the EFI pump - without this minimum charge I cannot even pull start it !) 

So you need to think about how you will monitor battery 1 charge ( install a Volt meter on the dash?) and then manually handle switching to ensure its charged when the motor is running.  Or will you install a modern VSR that does the charging automatically for you.

Now let's consider if battery 1 dies. You lose all electronics. In your set up - you lose essential stuff like radio, GPS, bilge pump. (Your diagram does not show where your Nav lights are wired - so perhaps they are gone as well).  The only way I can see you getting these working is if you switch the isolator to 1+2 and start your motor. But the concern with this is what was the nature of that battery 1 failure? If it was a dropped plate like in my case, the dead battery 1 would rapidly drain your battery 2 as they are connected. In severe cases a shorted battery may even explode if its being charged. 

To overcome some of these issues  you might consider a simpler set up - eg I have moved all my toys and devices to run off the Feeder pole from the isolator switch - and I have a large capacitor in the wiring to suppress electrical noise. I have also wired in a Volt meter to run off that Feeder pole. So it tells me either the battery charge or the charge coming out of my motor when its running. I have two identical batteries (Century Marine hybrids - strong CCA and reasonable performance on deep cycle use). I run off 1 until its drained (hardly ever happens) and then switch to 2. They are identical batteries. You use deep cycle batteries to get better lifespan if you are going to continuously drain them close to flat - but I got 10yrs out of one of my marine batteries using it as above. I have also wired into mine a charging circuit so that I can easily plug in a trickle charger when home on the driveway to keep both batteries fully charged. I often run out to the fishing grounds with both batteries 1+2 and switch to 1 when there, keeping 2 as a full backup.  

Alternatively, consider adding a modern VSR arrangement that actually let you charge and run of either battery.

 

23 hours ago, richard2234 said:

One clarification please, the advice includes switching from battery 2 (crank battery) to battery 1+2 after starting the motor. Is it okay to switch like this when the motor is running?

Please talk to Yamaha as the answer may be manufacturer and model specific and also switch manufacturer specific.

In my case, I have checked my isolator switches and there was definitely no connection when moving between switch positions. Just turn on your nav lights and switch between the positions - my lights switched off in between. Also regarding my motor (Merc 200hp EFI) the answer is definitely NO - do not run without a battery attached.  I was running on a single starter battery which had a catastrophic failure (dropped a plate causing an internal short). In effect I had no battery connected for the short time it took for the engine to die - yet there was a huge concern whether the current that was generated by the motor charging circuit (which had no where to go) had created a spike that damaged the ECM, the VRs (voltage regulators) and other electronic components. 

The recommendation from Merc was to stop the motor before switching between batteries.

-------------------------------------

Ok thats all I have time for at present Be back later.

Cheers Zoran 

 

 

Edited December 28, 2018 by zmk1962

[Fishop]

Just to throw a spanner in the works......I'm pretty sure someone on fishraider told me not to run with 1+2 selected.  I'm not sure why but I have since just stuck to the one battery for each trip.  Batt 1 one day.  Batt 2 the next trip. Etc.  Can't remember the reason tho. Lol.  Makes sense thst if you have an hour drive to a fishing spot you would put it on 1+2 and then you should have two full batteries when you get there!! 

 

[zmk1962]

4 hours ago, Fishop said:

Just to throw a spanner in the works......I'm pretty sure someone on fishraider told me not to run with 1+2 selected.  I'm not sure why but I have since just stuck to the one battery for each trip.  Batt 1 one day.  Batt 2 the next trip. Etc.  Can't remember the reason tho. Lol.  Makes sense thst if you have an hour drive to a fishing spot you would put it on 1+2 and then you should have two full batteries when you get there!! 

 

Hi @Fishop you are pretty well describing the "simpler" set up that I mentioned above. Running with 1+2 selected is the same as running with one bigger capacity battery.  While this charges both, there is no redundancy until you separate/isolate the batteries and maybe thats why the other fishraider did not recommend it.  But that is also why I suggested installing a Voltage meter so that at least you can monitor what is going on.  With engine running you should see 14 - 14.4V indicating good charging is in progress. If you see less you know something is wrong.  

Since I have installed my Drum Anchor Winch I actually run with 1+2 all the time as the winch manufacturer recommended to have the capacity of two batteries online to spread the current draw.  Also, given my experience with losing a battery and nearly frying the electronic components on the motor, I feel that if one of the batteries drops a plate, I'll have more plates online to absorb the charging current.  As per the post that Dave quoted,  I have also installed a 3rd battery which is my backup motor starter - call me anal but ......sh*t happens!.

Cheers Zoran

 

[Fishop]

Thanks for the clarification.  As always great advice!