How many 12V batteries do you have onboard?

[Capt Hook]

The PO of my boat had it set up for extended cruising.

The #2 battery was a single battery in the sail locker.

The #1 battery was a bank of 4 (only 3 when I bought the boat) Group 29 batteries he had mounted under the cabin sole.

I pulled the remaining 3 and had them tested.

One tested bad (and I've replaced with a new Group 27 Deep Cycle), one tested good and one tested 0% charge.

I had the last one charged and tested and it tested bad.

I'm thinking of going ahead and replacing that one with Group 27 Deep Cycle twin to other I installed.

All three batteries showed dates of manufacture in 6 or 7 of 2010.

I don't think I really need three batteries for the #1 bank and I'm hesitant to reinstall a 6 year old battery, even though it tested good.

What do you guys have for a house battery or house bank?

[Ken Cave]

It all depends what you have on board and is contingent on battery power.

On our CD 28, we do extensive traveling-over 500 miles this year so far, and have
a bank of four 6 volt batteries, two in the starboard locker, and two in the port locker
for the house system, which includes an Adler Barbour refrigeration. (yes, I do make ice)

For the engine, we have a group 27 deep cycle battery in the bilge area.

It is recommended that you replace all the batteries on one circuit at the same time.
If the older one goes bad, it will drag down the newer one, etc.

I have Interstate top of the line wet batteries, and have not had a problem with them.

Hope this helps

Ken Cave

[Neil Gordon]

I'm a fairly light user of electronic/electric gadgets, have done well with two deep cells. I use one as a house bank and reserve the other for starting, switching every month.

[Jeff and Sarah]

I have 4 6v batteries for 430 amp/hr serving as the house batteries and another 12v battery as an emergency start reserve (the two banks are connected with an echo-charger). I have never used the 12v battery to start the engine as I run everything (house loads and engine start) off the house bank. I do not have refrigeration but do have an auto pilot whom I let steer just about any time I'm not in a channel or docking. The lowest I've ever seen the bank get was 83% and that was after a full day sailing and 2 days at anchor with zero battery conservation techniques in practice (my anchor light is the only non-LED light on board... anyone want to climb my mast)? I don't have a real need for a 430 amp/hr bank but I didn't have a big enough bank for the auto-pilot so I upgraded and left enough extra capacity to add refrigeration in the future. I also added a 120 amp Balmar alternator though I regulate it down to 90 amps.

[Capt Hook]

I've been curious why some of you have been using two six volts or in some cases four six volts.

All the specs I've been looking at tell me how many cold cranking amps or reserve minutes, nothing on Amp Hours.

I did a little more surfing and now I find that a 6 volt Trojan T-105, which I've seen mentioned here, has 225 Amp Hours and a Group 27 only has 90 even though the physical size is similar. 720 cubic inches for the Group 27 and 805 for the T-105, which is a BCI Group GC2.

I had the notion that energy storage capacity and physical size were related.

Apparently not.

[Jeff and Sarah]

A general rule of thumb is if the battery specs do not list Amp Hours, it isn't a deep cycle battery. ...Or so I'm told.

One of the simple advantages of 6v batteries is 2 6v batteries are easier to man-handle than 1 large 12v battery with the same Amp Hour capacity. The decision to use 2 or 4 (or 6+) is based on capacity requirements and involves both series and parallel wiring.

Battery sizing and selection is a complicated subject. I studied the concept for about a year before finally making my decision but I wouldn't consider myself an expert. I went so far as to hire the well-respected Maine Sail as a consultant to review my wiring diagrams and equipment selections.

For what it's worth, I purchased my batteries from Sam's Club (Duracell EGC-2) for about $114 each. They have held up well so far but my installation still isn't quite a year old.

[Jim_B]

A simplistic approach is to determine how many amps are needed between charges and then size the battery bank for about 4X the calculated amps. In my situation I use about 100 amps a day, so have 400 amp house bank (4 6V Trojans). Using 150 watt solar panel and a 125 amp alternator with a smart charge regulator allows the used up amps to be replace pretty efficiently. If it's sunny (and not too warm to make the frig run continuously) I can get by charging every 2nd day.

[Capt Hook]

A simplistic approach is to determine how many amps are needed between charges and then size the battery bank for about 4X the calculated amps. In my situation I use about 100 amps a day, so have 400 amp house bank (4 6V Trojans). Using 150 watt solar panel and a 125 amp alternator with a smart charge regulator allows the used up amps to be replace pretty efficiently. If it's sunny (and not too warm to make the frig run continuously) I can get by charging every 2nd day.

When you say amps is that actually Amp Hours (AH)?

And when you say you can get by charging every 2nd day do you mean running the engine to charge? If so, how long do you have to run the engine to charge?

[Steve Laume]

"I did a little more surfing and now I find that a 6 volt Trojan T-105, which I've seen mentioned here, has 225 Amp Hours and a Group 27 only has 90 even though the physical size is similar."

There is no free lunch. And if it seems too good to be true and all that. You need to divide the 6V Amp Hrs by 2 to get the 12V Amp Hrs. So the T-105 would only hold a little over 100 Amp Hrs.

Raven runs two group 27 deep cycle house batteries and a group 24 start battery on an Echo charger. No frig and I am miserly with power in general, Steve.

[Capt Hook]

"I did a little more surfing and now I find that a 6 volt Trojan T-105, which I've seen mentioned here, has 225 Amp Hours and a Group 27 only has 90 even though the physical size is similar."

There is no free lunch. And if it seems too good to be true and all that. You need to divide the 6V Amp Hrs by 2 to get the 12V Amp Hrs. So the T-105 would only hold a little over 100 Amp Hrs.

Raven runs two group 27 deep cycle house batteries and a group 24 start battery on an Echo charger. No frig and I am miserly with power in general, Steve.

I was thinking of AH in terms of energy and neglecting the voltage.

It would make more sense if that rated batteries in KWH instead of AH.

[Paul D.]

I refitted my electrical system after our first season spent worrying about having enough juice left to start the battery which was the only charge source onboard.

After a winter of gathering information, including thoughts from this board, (Hamilton Ferris was a great source of advice at this time) I replaced two dual purpose 12v Group 27's with 2 Trojan T-105's for the house bank and a 12 volt start battery. I added a 60 watt solar panel with regulator, echo charger and Link 10 battery monitor (now called Xantrex LinkLITE). The last piece, which I have not installed yet, is a 100 amp alternator and Max Charge regulator. Haven't needed them yet but they are ready to install. I needed to fiberglass in some added shelf space in the cockpit locker for the extra battery. Last season I finally upgraded the old school 120v AC charger which I rarely used to a Charles 20 amp so I don't need to worry if that gets left on now either. My whole philosophy is set it up so there are no worries.

I had worked out my usage at about 100amp hours/day max with autopilot and fridge full on. Most days would be less use and mostly fridge. I figured during that max time I could happily run the motor some and would likely do so to get in and out of places (also heat up some fresh water).

It's been 13 really good 'electrical use' seasons now and two years ago I just replaced the batteries when I noticed some decrease in performance. I don't worry about power much, (though the new autopilot may challenge this usage amount, that's another story) I never worry about the start battery getting charged because the echo charger is automatic, and the solar panel charges the house and start banks just fine while we're away and they are all full when we arrive without plugging in. Also , over these years I have upgraded slowly each cabin and nav light to LED, which really helps dramatically cut down usage.

This is how we do it and I Highly recommend something like this if your usage is similar.

I recommend this system highly. I leave the batteries aboard all winter (checking water at winterization and spring fitting out) and

[Tom Keevil]

We also have two Trojan T-105's and a 12v starting battery connected to the house bank via an echo-charge. We don't use a lot of electricity, and the Trojans are now 9 years old and doing fine.

We also installed a Blue Sea dual circuit battery switch to replace the 1-both-2-off switch. This connects the starting battery only to the starter and the house batteries only to the distribution panel. So when we arrive at the boat we switch it on, and don't touch it again until we leave, when we turn it off. If necessary, the switch can connect the house bank to the starter.

We also have a Link 10 monitor, but it has ceased to monitor anything other than voltage. Will replace it with a Victron soon.

This system doesn't require a lot of thought, which is good. As we get older, we need to conserve our increasingly limited thought capabilities for more important activities.

[Astronomertoo]

"I did a little more surfing and now I find that a 6 volt Trojan T-105, which I've seen mentioned here, has 225 Amp Hours and a Group 27 only has 90 even though the physical size is similar."

There is no free lunch. And if it seems too good to be true and all that. You need to divide the 6V Amp Hrs by 2 to get the 12V Amp Hrs. So the T-105 would only hold a little over 100 Amp Hrs.

Raven runs two group 27 deep cycle house batteries and a group 24 start battery on an Echo charger. No frig and I am miserly with power in general, Steve.

-----------
I would like to clarify a misconception here on battery amp hours which I did not find anyone else catching. Pardon me if it has been corrected.
AMPERE HOURS:
Lead acid (typ) deep cycle batteries are like any other batteries which are built to provide power over a period of time, dependent on the purpose and cell design. Storage batteries are always provided with a cold cranking time at certain temperatures for high current starting functions, and for our purposes, the available ampere hour (AH) rating at different currents for how much time. In the case of the Trojan 6V T-105, the listing often quoted here is the 20 hr rating at 225 AH. That rating is assuming a continuous discharge of 11.25 amps (225/20), to the cutoff of the battery power curve. This assumes a new battery with full charge, and corrected electrolyte in all cells. An older battery will not do so well. If you look at their data sheet, they also list other curves, ie, 5 hr rate = 185 AH, 10 hr rate = 207 AH, and 100 hr rate = 250 AH. Per the last option, if you are only drawing a house load of 2.5 amp, then your battery could last 100 hrs, or 4 days.
The data sheet also provides for short term high current dischages of 25 amps fofr 447 minutes, and 75 amps for 115 minutes. For house battery purposes we do not utilize these last 2 curves, unless you have a need for a high capacity bilge pump.
SERIES PARALLEL, Volts and Amps:
For the purpose of designing and maintaining DC battery powered equipment, we need to understand that if you put 2 equal sized good batteries (ONLY of same voltage, ie, 12V) in parallel, we would have twice the ampere hours available. So, if you have 2ea 100 AH 12V batteries, the parallel circuit would still be 12V but with twice the AH, 200 AH. Keeping in mind each 12V battery has 6ea 2V cells and if one of those cells is shorted, going bad, it can drag down the pair reducing AHs, thus reducing the total power, and charging capabilities. Batteries are better off charged separately for that reason.
For batteries in series we have an opposite case. The total sum of any (add the voltages) 2 equal batteries in series, ie, a 6V in series with any other battery will be the total of the two; ie 6 + 6= 12V, 12 +12= 24V. However, since you are adding voltages, the AH for 2 equal size batteries will have the same total ampere hour capacity at twice the voltage. If each battery is a T-105 rated at 225 AH for a 20 hour rate, then the sum of 2 of them in parallel for twice the voltage (and power/watts) is still 225 AH for a 20 hour rate, You do not divide or halve the ampere hours in series circuits.
However where some division confusion might have crept in, in earlier postings, there is electrical and electronic equipment out there which can run on multiple power supply voltages, in which case the circuit load might be half the current at 24 volts compared to the current in a 12V supply. But that has nothing to do with the series or parallel battery power capacities, calculations or fuse/breaker sizing.
It goes without saying you should never parallel different voltage batteries (ie, 6V + 12V) because that would directly short the larger voltage battery to the smaller voltage battery, and you can have a resulting explosion, with injury and fire.
And BTW, we all also know the older boats have circuit panels and wiring which may not meet the current standards for conductors, and protective DC battery short circuit protective fusing per the American Boat & Yacht Council (ABYC). If you are upgrading your DC battery or AC power systems and have any questions, it might be a good idea to see if you need to perform any other cable or short circuit protection enhancements for the safety of your boat. There is good info out there from ABYC, and Blue Seas, and others.
BobC

[wsonntag]

Two batteries; 1 series 27 deep cycle as the house battery, one 24 series as starting battery. I have no refrigeration and a minimum of electronic gadgets; most all lights now low draw LEDs; the alternator charges the batteries nicely; batteries stored inside in heated space for winter on a approx 2 week trickle charge regimen; just replaced the 24 series after 11 years of service! Suggest Nigel Calder's maintenance book for by-the-numbers calculation of demand and very belt and suspenders recommendations. Did I mention the kerosene lamp and tiki candles?

[Jim_B]

Suggest Nigel Calder's maintenance book for by-the-numbers calculation of demand and very belt and suspenders recommendations.

Agreed, would highly recommend anyone with a somewhat complicated boat to get and read Calder's "Boatowner's Mechanical and Electrical Manual". I had to read sections of it several times to get the concept and 'balancing act' of electric demands, batteries and charging. Well worth the time and investment.