Batteries

[Stevan47]

Guys/Gals: Advice and suggestions, please. Currently, I have two 12V (BCI Group 24) starting batteries in my vessel( 600 CCA, RC 130, Rated Capacity@C20, 80AH). These batteries, sealed and maintenance -free, were manufactured in Feb '12 and have given no trouble in all this time. The engine starts first time every time, after just a few turns. Considering they are now just over five years old I consider it great they have lasted this long. Naturally, they are always under cover within the engine compartment and generally always on charge on the trailer when not at sea, so they 'live' in a protected environment and that probably assists with the life span. The onboard charger is a Pro Mariner, Pro Nautic 12-20P, a marvelous device, I might add. For information, both batteries are connected in parallel( I think I've got that correct). The engine is a Yanmar 3YM30.

Recently, after my last period underway, and after leaving the charger off for a few days, , I tested the batteries and found one to be a little under charge, compared to the other. Basically, one was reading 12.87 volts, while the other was down around 12.00 volts, or thereabouts. This is unusual, as generally they have always corresponded, + or - 0.1volts. From this I suspected that one battery is 'on it's way out'.

Anyway, to cut a long story short, noting that five years has elapsed, and not wanting to risk battery failure/total power loss while underway, I thought I should just change out the batteries now.

We have a good choice of battery brands here, so with cost and efficiency in mind I did some research. I have decided on a different brand of battery, same BCI Group (24), same CCA (600), but with slightly lower RC (125) and Capacity (73AH). Also, the physical dimensions are about 1mm less all round, which makes it a better fit in the tray at the back of the engine.

My question is: noting the CCA (600) of each battery is the same, will I still get the same starting/cranking effect from the new batteries, although the other specs (RC and AH) are slightly lower? I understand that while linked in parallel (as mine are) the combined voltage remains the same (12), however the CCA and RC are doubled, as opposed to being linked in series ( I think I am correct here, but please correct me if necessary).

My main reason for choosing the new brand batteries is the lower price and slightly smaller dimensions. Otherwise, they are similar quality and with a two year warranty period.

I would appreciate all suggestions and advice and I trust this post is not too convoluted.

Kind regards, Stevan

 

[Romakeme IV]

I don't know your entire setup - do you have a house bank as well? I am curious why you use 2 group 24 in parallel to start a single diesel. I would suggest you would be better off with a larger single group 31.

To answer your question - yes the same cranking amps should be available with the new batteries - with the lower RC and AH they may draw down slightly quicker.

Regards, Rob

 

[Stevan47]

Hi Rob: Thanks for the response. The two batteries were set up that way when I bought the vessel, second-hand, from the dealers here in Perth. As I understand it, that's the way since it has been since acquired new from the factory. I don't have a house bank, as I really have no use for that, noting I only do day/fishing/cruising trips, with the occasional o/night at anchor in local waters. The nav lights, VHF radio, chart plotter, 'frig and other basic (standard) appliances have never run the batteries down to an unacceptable level during an o/night stop. Start up the next day has always been faultless. My vessel is just the basic R21-EC, with 3YM30, as delivered from the factory, with the addition of a Raymarine E7D MFD chart plotter/depth sounder. Thoughts? Regards, Stevan

 

[knotflying]

You should be fine. I am not sure of the wiring setup on the 21, but both batteries in parallel all the time seems odd, especially when there are a couple of "house" items to power up. Usually when there are two batteries there is a selector switch to use battery 1 or battery two or both, which would be parallel.
Also, your statement about checking the batteries and you got different voltage readings confuses me if this is in fact a parallel hook up. If both batteries are in parallel then you would get the same reading if they are joined. the only way you could get different readings is if you disconnected them before testing.

With the switch set up I mentioned earlier you would usually start your engine on one battery, let's say battery 1. After an overnight you would switch to battery 2 and start your engine since battery 2 should be fully charged, having been isolated from overnight draw from house items used. If you have charging relays then all the batteries will get charged while underway.

 

[SGIDAVE]

Hello Stevan,

I suspect your two batteries are NOT paralleled...except when the Blue Seas ACR combines the batteries into ONE bank for charging purposes whilst underway.

Furthermore, If the batteries where paralleled in a fixed, permanent manner, they would read EQUAL voltages (i.e., you won't get 12.8V on one battery and 12.4V on the other battery. I believe you described getting differing voltages from the two batteries...

IF your setup is as you describe with (2) 12V cranking batteries in parallel, then you have NO REDUNDANCY for when the 'start' battery fails or gets low...cuz if they REALLY are paralleled, then BOTH will be dead or at least low and you can't crank your engine. Bad scenario.

My 21EC came with (2) Gr24 12V batteries...one was "house" and the other was "start." Trace the red wire from the starter to one of the batteries...THAT is your start battery.

Do you have a blue seas ACR? Is there REALLY a 'jumper' between the (+) and (-) terminals on your two batteries (which would denote true, fixed parallel set up)?

I would suggest you move to electrically separate the two batteries so you have a dedicated, isolated 'start' battery. The Blue Seas ACR will easily accomplish this.

/dave

 

[Stevan47]

Hi Dave: although all the other guys have provided valuable advice, yours seems to clarify things a bit better. Maybe it is just me! In any case I will have another look at the wiring setup today and get back to you for further guidance. There is an ACR which is linked in to the system so you may be right. Once again, thank you to 'Knotflying' and 'Rob' for your input - it is appreciated muchly. Talk again soon. Stevan

 

[Stevan47]

Hi Dave: I finally managed to attach some photos to my album. You can see them at 'Stevan47'. I am sure all my comments and queries will be of interest to the wider Tug Nut community, even though some of them may be fairly simplistic. I read your email thoroughly and it now appears the batteries may be connected in series, as you suggest. There is definitely not a jumper directly connecting positive to negative terminals - that is what made me think it was in fact a parallel set-up, not a series arrangement. Am I correct in that assumption?

The two negatives are directly linked by a yellow jumper, which then is connected to a ground harness plate at the port side of and below the aft end of the engine. The two positive battery cables are not directly linked: one leads away to the starter motor (B1), while the other (B2) leads to the busbar, which is also linked to the starter/control panel and battery isolator in the wheelhouse. There is also a second positive cable from B1 which is connected to the Blue Seas ACR and thence to the busbar. Of course, there are other links, but that is the basic layout which I have traced.

I could not see a direct (jumper) link between a positive and a negative battery terminal,indicating a series connection, so I assumed it was in parallel. Can you see where I am coming from? Anyway, jump into my album (Stevan47) and have a look at some of the photos, including the pencil sketch of the schematics. Appreciate your thoughts and 12 volt tuition! Kind regards

 

[knotflying]

For information, both batteries are connected in parallel( I think I've got that correct). The engine is a Yanmar 3YM30.

I think you are confusing parallel and series. From the pictures I saw, your batteries are neither. They are independent of one another, except when your ACR kicks in. Then it joins them and they are parallel. The negative (yellow wires) always run together to create a continuous bond throughout the boat and that may be what is confusing you. As a matter of fact you can see that each cable is marked, one for house and one for engine. I could not read your schematic clearly so I relied solely on your pictures.

 

[Stevan47]

Hi Knotflying: that is great advice. David also gave me similar advice. All starting to make sense now, albeit still somewhat 'muddy' at times! It has been a big help chatting with you all on this topic. Kind regards. Stevan

 

[knotflying]

As I stated earlier I am not as familiar with the 21 as the other models. I would think that there would be a switch that would allow you to combine the two batteries in the event that the engine battery died. The switch would make life easy. However, without the switch you could always remove both wires from their respective batteries and switch them to pull the fat out of the fire.

 

[SGIDAVE]

I would think that there would be a switch that would allow you to combine the two batteries in the event that the engine battery died. The switch would make life easy. However, without the switch you could always remove both wires from their respective batteries and switch them to pull the fat out of the fire.

Yes, having a way to 'combine' or switch to a 'fresh' (or 'fresher') battery would be nice. I modified my 21EC to allow this.

The whole philosophy of combining a 'dead' battery with a good battery doesn't make much sense. It is a common strategy though. Using an OFF/1/BOTH/2 switch would also work to allow simply switching to a 'good' battery instead of 'combining' bad+good batteries. This would be pertinent in the situation of a dead start battery when away from the dock where your options to restart the engine are more limited.

I've read authors who recommend for ONE bank of batteries to be used for all house/start loads and to have a second, single battery as 'back up' which is charged by an ECHO type devise

in combination with an OFF/1/BOTH/2 type of switch. In the event of a low 'main' bank of batteries, you switch to a fresh back up battery (sized sufficient to start your main engine) rather than combining dead with good batteries which MIGHT not be up to the task of restarting your engine especially if extra 'cranking' is needed.
Just another option to consider for your electrical set up.

With the Blue Sea ACR, remember that it will not combine batteries if one of the 12V batteries is discharged to less than 9.5-10V. This happens easily in a 21EC when the "house" group 24 battery gets run down by the stereo memory if you forget to turn off the switch under the throttle/gearshift console. The ACR has properly 'opened' to separate the batteries...so your "start" battery is fine. You crank up the engine but still have no 'house' power. And you won't have house power until you somehow bring the dead house battery to 10+V so the ACR will recognize it as a 12V battery (and not a juiced up 6V battery) and combine them so it can recharge. Vexing but unavoidable situation when using the ACR. And I like (and use) ACRs by the way; this isn't a bash on them - just a cautionary note of how they function.

fair winds and charged batteries,

dave

 

[captstu]

Sealed, maintenance free batteries are neither sealed, nor maintenance free.

They are built with chemistry that uses less water when charging. Some of the more expensive batteries have "recombiners" that catch the expelled hydrogen and re-combine it with oxygen to replace the water used in charging (assuing they are lead/acid batteries or one of several other common types.)

Before you trash an otherwise sort of working battery that is a few years old, either AGM or standard flooded), pry off the caps - AGM batteries take 19 mm thin walled sockets).

Look at the level or the condition of the mat. If the level is low or the mat looks try, slowly add distilled water until it is nearly full. Let it sit for a few hours and put it back into service.

Several years ago, I was in a lonely anchorage and both my starting AGM and my 8D house agm died. I had no place to buy another - so unscrewed the sealed caps, added some tap water (all I had), and did the same on all 12 cells of both batteries.

By the time I was done, the engine started easily - and the fridge had come on - both batteries recovered to the point that I decided to replace the starting for safety, but kept the house another 2 years until I sold the boat.

I've helped 2 other boats with dead batteries, both recovered enough to continue on to their destination.

Give it a try, you have nothing to lose. /Stu

 

[Stevan47]

Thanks again all you guys, Capt' Stu included. Great advice. I have now started a file with all your emails - sort of like a working reference manual. Really handy. Kind regards to all. Stevan