Battery Configuration

[Charliemciver]

I bought a 43ft second hand élan 434. I intend to cruise the UK south coast and further afield and have a young family, and expect a family friendly domestic setup!

Frustratingly, all the batteries on board needed replacing - survey doesn't catch that kind of thing!!! There's 6 batteries: 1 starter, 2 domestic, 2 bow thruster, 1 windlass.

I bough a pair of Lifeline AGMs for the domestic and Numax Sealed
Marines ones for the rest...
And set to work...

The previous owner looks to have botched some things up and left a bit of a mess, with some the windlass battery not connected and the bow-thruster pair not charging!

My alternator has a 2 bank separator; my shore power charge looks to support 3 banks, but 1 is unused.

It looks like the bow-thruster and windlass have been joined to the domestic circuit. I guess this is good in that the bow thruster and windlass batteries are relatively rarely used and so their capacity is available for domestic use, which would be useful. But the lead acids for the windlass and bow thruster will be ruined by deep domestic use, as will the AGMs by cold-cranking of windlass or bow thruster. And joining lead acids to the AGM domestics is a no-no too, right?

But joining them to the starter is also a bit of a waste too, and would lose the 'protection' of the starter battery. There doesn't seem to be a 'standard' setup out there from what I can find. Any guidance about how to configure them?

The other option is to replace my 2 bank alternator splitter with a 3 bank one, and put the bow-thruster and windlass in their own bank, and perhaps put a switch in so I can choose to 'steal' from the bank if the domestic sets get low.

Anyone got any advice?

Would love to know what config others have!

Thanks,

Charlie

[btrayfors]

Originally Posted by Charliemciver

.................

I bough a pair of Lifeline AGMs for the domestic and Numax Sealed
Marines ones for the rest...
And set to work...............

Charlie

Charlie,

I sure wish that folks would ask these questions BEFORE going ahead and buying stuff. Now that you've made the investment -- in AGMs and sealed batteries -- I guess you'll just have to work with it.

Your questions have been posed and answered and debated ad nausium on this and other Boards. While there's no one "right" answer for everyone, a few things might help you.

1. AGMs and flooded batteries have practically identical charging profiles. While it's not ideal to connect them together, it can be done will little ill effect.

2. "Sealed" "marine" batteries are generally not to be preferred. They're not real deep-cycle batteries nor are they the best sort of starting batteries for a boat. But, you're stuck with them for the present.

3. AGMs are indeed meant to be deep-cycled; they can deliver a lot more amperage fast than can flooded batteries.

4. The "ideal" setup involves having a sizeable house battery bank to which ALL onboard charging sources are connected, including alternator, battery charger, solar panels, wind generator, etc. Then, use either a voltage follower device like the Xantrex EchoCharge or the Balmar DuoCharge -- or one of many battery combiners to automatically maintain the start battery. You can also maintain a windlass battery the same way, or you can have a separate means of charging. All depends on your setup and your preferences.

5. Golf-cart batteries are often the best bang for the buck (or the pound, in your case). You've already made some battery decisions which obviate this choice for the present, but keep them in mind. They are relatively inexpensive, relatively robust, take a lot of punishment and have a useful life on the order of 5-7 years if treated properly.

6. With a setup such as mentioned in #4 above, you don't need a charger with multiple outputs nor do you need a splitter on the alternator. You run ALL charging to the house bank, and take excess current from there to charge the house (and windlass) batteries. These require very little charging....it takes less than 1AH (yes, one amp-hour) to start the typical diesel. This is replaced very quickly.

7. For a 43-foot family cruising boat, a house bank of 400-700AH total capacity would be about right. This is the equivalent of four-to-six 6V golf-cart batteries in series/parallel.

8. To take advantage of AGM charging capabilities you really would need a BIG alternator and external regulator. Lifeline AGMs can easily take 100% of their amp-hour capacity in charging amps when they're 50% discharged, so 200AH of these AGMs could take 200 amps charging current easily. Almost no boats are already set up to really take advantage of AGMs....one wonders what the fascination is with them :-) But, again, you're already stuck with them so will have to make the best of it unless you really want to redo your alternator/charging systems.

Don't mean to be overly critical, and perhaps I'm super sensitive about batteries and charging systems because I work with them every day. Some of the most dreaded words I hear from my customers mouths are "I've just bought a new XYZ; could you please come and install it?".

More often than not that means that one has to settle for something less than "ideal"....not what I like to do with my customers.

Good luck,

Bill

[mitiempo]

I agree with Bill Trayfors post above.

But why so many battery banks? At the very least the windlass could share the thruster batteries - as long as they are both 12 volts. My preference would be to not have batteries forward at all and power these 2 items from the domestic bank with the proper large cabling. Less batteries to maintain or replace. All charge sources to the domestic bank as posted above.

[Stu Jackson]

Whew, Bill & Bryan have done you a great service: you've gotten 35 years of professional service in two replies.

There's also this resource, have at it.

Electrical Systems 101

[alexandlorna]

Charlie
When our new engine install was done ,the electrics were re-configured to include 50a 3 output Victron Centaur charger and in order to realise relatively quick charge times we had two 120A alternators fitted
The batteries are 3x 125ah domestic , 2x 125ah stern thruster , 1 x125aH bowthruster /windlass , 1x 90aH starting battery
All of these are flooded lead acid except the bowthruster ,which is AGM
The alternators go through a ( 2input 3 output ) combiner/splitter and charge everything
The Victron unit similarly charges all except the AGM bowthruster batt as it has different characteristics
Bow thruster charge is engine only and has never been a problem
Our thruster batteries are semi-traction rated and even though they are often drawing large (300-500A) currents they seemto hold up very well
All battery banks are electrically separated

Alex

[mitiempo]

Simple is always better.

Small batteries (or small battery banks) are always less efficient than a bank of the same size combined into one.

Charging systems are always better when not split for charging multiple banks of batteries.

I cannot think of one good reason for as many separate banks of batteries on both Charlie's and Alex's boats. Heavy wires forward for windlass and thruster are expensive, but a one time expenditure. Batteries are a continuing expense as well as an increase in maintenance.

[alexandlorna]

While I would agree re simple being better etc, surely use of bow and stern thruster would rapidly discharge the whole system leaving , the domestic bank very low .
These units often draw 3-500 Amps and will blow fuses constantly unless properly rated
The main reason for a separate bow thruster bank , is precisely to avoid huge cable cross sections and long runs
Our main batt banks are in the stern and running a reasonably sized chaeging cable forward , is much more efficient than having enormously long , heavy and expensive thruster cable running 30 -40 feet . ( the thruster cables are about 1" dia !)
Vetus specifically recommend against long runs or too smallcables for obvious reasons

Alex

[mitiempo]

I have installed systems with both bow thrusters and windlasses on larger boats than yours with cables run forward for both without problems.

If your main battery banks are in the stern why a separate bank for the stern thruster?

Use of thrusters and windlass should not discharge the whole system - after all the engine will be running when either are in use.

[alexandlorna]

I would not say it cant be done , simply that electrically such heavy current items are best on short cable runs , I simply followed the manufactures strict guidelines , but did have a marine engineer and electrician do the actual install .
The stern thruster has its own bank simply to avoid drawing down any other batteries. We have never had issues with lack of domestic power even when using the inverter
I agree re engine running when thruster in use , but I prefer domestic, starting and stern thruster banks to be separate entities
Can I respectfully ask , are you suggesting one large bank for all these services?
Alex

[sailinglegend]

Originally Posted by alexandlorna

.... Can I respectfully ask , are you suggesting one large bank for all these services?

I would suggest this is a good idea - IF you have auto disconnect relays to isolate them when they are energized.

Bow thrusters should only be used when absolutely necessary. My observations of 7 years liveaboard here in the Med are that people use them too much. If you anchor most of the time them you should never need a bowthruster. When you go into a marina then the marineros in their joker boats will be a much better bow thruster if you need it.

If your AGMs are ONLY charged via the engine then you are going to murder them very quickly - don't then complain that AGMs are no good!!!!

Use all the spare battery power for your service battery bank and charge them all from all your charging sources and they will last much longer.

[Charliemciver]

Thanks for all the advice so far. I'll digest it all a bit later today.

I have got the nasa BM1 device to fit (it's taken me way too long to figure out the physical wiring of the boat) before I tackled fitting it and now need to remake the wiring harness for it because of the length from my battery to the power management area of the boat!

Another quick question... I do various electronic and software product development for my
business. Does anyone like the idea of battery management data coming out over (proprietary?) NMEA and onto iPhone/iPad apps for convenience? Would anyone pay the extra $50 in a nasa BM1 type device for the hardware software to do that?

[alexandlorna]

Sailing Legend
I can accept that there are many ways to achieve the same result , and as an engineer have often found that others can shed illumination on a problem from a different viewpoint .
I will say that the AGMs for bow thruster have so far showed no signs of anguish by being engine charged over the last 2 1/2 years , however time will tell . We moor on an extremely busy and often windy, narrow river ,and so especially when single handed they do get a lot of use .
As far as I am aware though all power from the twin alternators is combined and then supplied where require by the splitter unit
Similarly with shore power (excepting BT AGM)
I should say that I did not design and install the system ,it was designed and installed by marine/electrical engineers and it works

Alex

[jgbrown]

Originally Posted by mitiempo

Simple is always better.

Small batteries (or small battery banks) are always less efficient than a bank of the same size combined into one.

Charging systems are always better when not split for charging multiple banks of batteries.

I cannot think of one good reason for as many separate banks of batteries on both Charlie's and Alex's boats. Heavy wires forward for windlass and thruster are expensive, but a one time expenditure. Batteries are a continuing expense as well as an increase in maintenance.

Cable size required can become nuts. Impractical to run the wires in some cases and can interfere with other systems when under high load.
Have only had to do a separate bank once but it was the only practical way. As a general rule not a great plan, and you are correct. Exceptions exist to prove the rule

[Scott Berg]

To pick up on a previous comment or two,

We prefer dedicated windlass and thruster banks (hopefully the same bank) if room permits. The voltage drop while either are running can cause issues with inverters, electronics, radios, etc.

Even if you can handle the cable introduced voltage drop (10% or less with proper wiring) it won't stop the battery voltage from dropping. In some cases I've measured actual battery voltage from a good bank to drop below 11v (amazing what a 100+ amp load can do). As noted above, this won't harm the battery, but will cause voltage sensitive equipment on the house bank to cough a bit which can be very irritating.

As for building up a battery bank from smaller cells, assuming proper connections are used, no difference should be noted from having the battery manufacturer do the same (an 8D is just 6 2v cells in one case. A bank made up of 6v golf cart batts or, if room permits, 6 2v L16 size cells, will outperform one large battery in most deep cycle operations and be much easier to install.

Scott
CHARDONNAY BOATWORKS

[Pete7]

Originally Posted by Charliemciver

Another quick question... I do various electronic and software product development for my
business. Does anyone like the idea of battery management data coming out over (proprietary?) NMEA and onto iPhone/iPad apps for convenience? Would anyone pay the extra $50 in a nasa BM1 type device for the hardware software to do that?

Hmm, probably not. The reason folk choose the NASA BM1 is its cheap and works. Your idea of intergrating this into NMEA is probably of more interest to those who want to link lots of instruments together. If you were starting from scratch to do this then B&G Zeus would take a lot of beating and can already be linked to an Ipad I think.

Zeus Touch

Now produce a widget to measure the SWR of a VHF for $30 and you are on to a winner. There are lots of SWR meters but for some reason VHF ones cost a fortune and yet there is a huge market if you can keep the cost down to accessory level for recreational sailors. I am available in the UK for product testing btw (hint)

Pete