Battery management

[AlanH]

I'm getting paranoid here. There seem to be endless dicussions about battery management on this forum but I can't see the problem for those of us who are not living and working on computers aboard. We've had this boat for 7 months now and used it most weekends and a couple of separate weeks away so far. Our last boat, admittedly small and with an outboard had only one 85Ah battery and charged at 6A and we had no problems on that.

Our setup seems minimal compared to those that many here describe:

 

Single 55Ah alternator

2 X 110Ah leisure batteries

Relay split charger

Compressor fridge

No TV but occaisional use of Laptop and portable DVD player

Car type radio

Usual strip lights plus some spotlights.

Shower and water pumps

12 Vac

No battery management system

 

We don't use the fridge for weekends but it is on permanently when cruising for more than a couple of days.

 

My problem is that I don't have a problem. The batteries have never looked like going flat. Never had a voltmeter reading below 12.1v and usually well above that. Am I doing something wrong? Why should I need a fancy management system/extra alternator etc?

Edited July 3, 2008 by AlanH

[alan_fincher]

No, you are doing nothing wrong.

 

You already have more alternator and battery capacity than would ever have been considered necessary, say 20 years ago, and people's batteries didn't use to repeatedly go flat just because they didn't have an on-board equivalent of Battersea power station.

 

The trend towards multiple high-power alternators, alternator controllers and massive battery banks is a modern one. Similarly inverters. It is brought on largely because people are convinced they can't survive without electric kettles, irons, hair dryers, microwaves, washing machines, etc.

 

If you are happy with what you have, get out there and enjoy the canals like we do. If it's worked for you up until now, it will continue to do so, and you can feel smug that when you need to replace your domestic batteries, it will cost you maybe £150, not three times that figure.

 

This is not intended to be a dig at those who can't be without their creature comforts - just to point out that many of us live happily with exactly the set-up that Alan has described, (and don't find ourselves pursuing warranty claims with Sterling as a result....).

 

Alan

[blackrose]

This is not intended to be a dig at those who can't be without their creature comforts - just to point out that many of us live happily with exactly the set-up that Alan has described, (and don't find ourselves pursuing warranty claims with Sterling as a result....).

 

Alan

 

Using this word figuratively of course...

[John Orentas]

My problem is that I don't have a problem. The batteries have never looked like going flat. Never had a voltmeter reading below 12.1v and usually well above that. Am I doing something wrong? Why should I need a fancy management system/extra alternator etc?

 

Good God however have you survived.

 

Well Alan you have already found two people who have also managed all the privations.. As Alan says if can survive without a hair-dryer you can enjoy your boat without the feeling that you live in a telephone exchange..

 

It is worth considering the fitting a modern type alternator if you haven't got one already, that charges in the region of 14+ volts and be aware that your fridge is the the major user of all those precious electrons. The rest will look after itself.

Edited July 3, 2008 by John Orentas

[blackrose]

How easy it is to tell people that they don't need mains appliances onboard when you can simply go back to your nice house after a weekend of boating and have them all there!

 

Depending on whether they are on shore power & how much they move their boats, those who actually live aboard and who may wish to use some of these appliances may find themselves investing in bigger battery banks, more sophisticated charging systems, generators, solar panels, etc, etc. Or they may just charge more frequently.

[BlueStringPudding]

How easy it is to tell people that they don't need mains appliances onboard when you can simply go back to your nice house after a weekend of boating and have them all there!

 

[alan_fincher]

How easy it is to tell people that they don't need mains appliances onboard when you can simply go back to your nice house after a weekend of boating and have them all there!

 

Depending on whether they are on shore power & how much they move their boats, those who actually live aboard and who may wish to use some of these appliances may find themselves investing in bigger battery banks, more sophisticated charging systems, generators, solar panels, etc, etc. Or they may just charge more frequently.

I can't argue with a word of that Mike.

 

But the original poster was clearly not a live-aboard, as he described his boat use in a pretty detailed way.

 

Many of course do live aboard, often with less than the original poster describes.

 

We've had 4 aboard a smallish (by your standards!) boat for 3 weeks, and not encountered problems with our arrangements.

 

If I was moving permanently on board, more space would currently be more important to me, than more electricity.

 

But yes, of course it's easier if you can take several bags of washing back to a land based address - I never meant to say it wasn't. The original poster presumably also has this luxury.

[Ex- Member]

 

We intend to live without too much in the way of 240 consumer electrics. However we did opt for a 240 volt fridge and have a basic motorised tub washing machine. We got a 3kw inverter. We could have easily used a smaller inverter for the fridge and wee tub washer, but got such a good deal on the inverter it was viable to get it knowing that extra power was there if needed. It's not so much that we need that much power, but knowing It's there if needed for any reason gives some peace of mind. Likewise with the batteries, we'll have a bank of nine, and living frugally (fridge off) energy wise would probably last several days without need to recharge, again it's like a back up, if an engine problem arises we might have several days power available until any problem is solved.

 

It's great if people can exist on such minimal power requirements, which we also wish to do, but having all the extra equipment we have in comparison which is readily available, we believe gives us many more options, and scope if we need to adapt in any way.

Edited July 3, 2008 by Julynian

[blackrose]

I can't argue with a word of that Mike.

 

But the original poster was clearly not a live-aboard, as he described his boat use in a pretty detailed way.

 

Many of course do live aboard, often with less than the original poster describes.

 

We've had 4 aboard a smallish (by your standards!) boat for 3 weeks, and not encountered problems with our arrangements.

 

If I was moving permanently on board, more space would currently be more important to me, than more electricity.

 

But yes, of course it's easier if you can take several bags of washing back to a land based address - I never meant to say it wasn't. The original poster presumably also has this luxury.

 

Yes, I was just pointing out the difference. The OP was questioning why some forum members had complex electrical intallations when he felt he didn't need them.

[AlanH]

How easy it is to tell people that they don't need mains appliances onboard when you can simply go back to your nice house after a weekend of boating and have them all there!

 

Depending on whether they are on shore power & how much they move their boats, those who actually live aboard and who may wish to use some of these appliances may find themselves investing in bigger battery banks, more sophisticated charging systems, generators, solar panels, etc, etc. Or they may just charge more frequently.

In my original post I excluded liveaboards. Of course their power requirements are higher. Nobody was suggesting that liveaboards should give up these appliances. It is you who are getting paranoid now.

[BlueStringPudding]

It is you who are getting paranoid now.

 

[Guest]

Is this the right room for an argument?

[alan_fincher]

Is this the right room for an argument?

I've told you once!.....

[paulcatchpole]

The OP was questioning why some forum members had complex electrical intallations when he felt he didn't need them.

 

As part of the redesign process for our little 40ft boat, I'm currently working out where to find 12U of 19" rack space, and whether what's left of my reel of stranded CAT6 UTP will suffice... No joke...

 

PC

[blackrose]

In my original post I excluded liveaboards. Of course their power requirements are higher. Nobody was suggesting that liveaboards should give up these appliances. It is you who are getting paranoid now.

 

Oh really?

 

Yes, you did exclude liveaboards, but others who answered your post didn't and specifically referred to living happily without and living in a telephone exchange.

Edited July 3, 2008 by blackrose

[paulcatchpole]

living in a telephone exchange.

 

I quite like comms rooms, the fan noise is soothing and the air cool...

 

But maybe that's just me...

 

[Gibbo]

As part of the redesign process for our little 40ft boat, I'm currently working out where to find 12U of 19" rack space, and whether what's left of my reel of stranded CAT6 UTP will suffice... No joke...

 

Shouldn't this be in that other thread about anchors?

 

Gibbo

[paulcatchpole]

Shouldn't this be in that other thread about anchors?

 

Gibbo

 

Are you calling me an anchor, Gibbo? Charming!

 

PC

[Gibbo]

Are you calling me an anchor, Gibbo? Charming!

 

PC

 

No just your 12U of ballast.

 

Gibbo

[Justme]

Is this the right room for an argument?

 

 

Its a thread about power so yeh must be.

 

 

 

Justme

[Gibbo]

My problem is that I don't have a problem. The batteries have never looked like going flat. Never had a voltmeter reading below 12.1v and usually well above that.

 

I'll read 2 things into this.

 

1. You have relatively small loads and are never really discharging your batteries by much (this is good for them). The fact that you have never seen less than 12.1 volts is indicative of this. Even with fully charged batteries most people see less than this when a hefty load is put on them.

 

2. You may well have a relatively modern alternator which already charges at a higher voltage than the older ones. They were typically about 13.8 Volts. Newer ones are typically somewhere between 14.2 and 14.6 Volts. This makes a HUGE difference.

 

If you have one of the more modern alternators charging at this higher voltage then an external alternator controller (nastily called "battery management systems" by some people - they don't manage the battery, they manage the alternator!) will do next to nothing anyway.

 

Gibbo

[Guest]

I'll read 2 things into this.

 

1. You have relatively small loads and are never really discharging your batteries by much (this is good for them). The fact that you have never seen less than 12.1 volts is indicative of this. Even with fully charged batteries most people see less than this when a hefty load is put on them.

 

2. You may well have a relatively modern alternator which already charges at a higher voltage than the older ones. They were typically about 13.8 Volts. Newer ones are typically somewhere between 14.2 and 14.6 Volts. This makes a HUGE difference.

 

If you have one of the more modern alternators charging at this higher voltage then an external alternator controller (nastily called "battery management systems" by some people - they don't manage the battery, they manage the alternator!) will do next to nothing anyway.

 

Gibbo

 

[Arnot]

My problem is that I don't have a problem. The batteries have never looked like going flat. Never had a voltmeter reading below 12.1v and usually well above that. Am I doing something wrong? Why should I need a fancy management system/extra alternator etc?

First, if you have no problem, it’s better not to mess with it. Having come from a boat with very limited power availability, you have already learned how to be frugal and this will save you a lot of money for the future…

 

There are many sophisticated battery management systems but none so intelligent as learning to use less than you have!

 

Now to the equipment;

Battery management (IMHO) is an oft misused term, leaving aside the intelligent use method, my take on battery management in this context is that it is the controlled charging regime employed by charging systems that vary the charging voltage supplied according to the state of charge of the battery as determined by the current drawn and occasionally the battery temperature.

 

The benefits of this sort of system are that when a battery (bank) is left on charge for considerable lengths of time (say 10 hours plus) the charge rate can be maximised in the early stages of charging and then reduced latterly to a level that will not overcharge or damage the battery.

 

This sort of charging regime is great for boats that are shorelined, sometimes for weeks or months at a time. It will maintain the battery in good condition and fully charged.

 

Battery charging from an alternator in the average narrow boat is a different matter. In this case it is unlikely that the engine will be running continuously at a speed that would allow the alternator to produce it’s maximum output for more than ten hours. In consequence the need for long term float charging is minimal. Not only this but at the charging voltage is likely to vary with the engine speed from time to time, the charging voltage cannot actually be fully controlled by electronics.

 

It is my take that multi stage alternator regulators that emulate the mains powered “Battery Management Systems” are frankly a waste of money in the vast majority (99%) of cases. It’s a perfectly good solution - just applied to the wrong problem.

 

One thing that that “Battery Management” does not do (although it is an additional feature of some systems) is to compensate for the often-extended wiring used in narrow boat alternator charging systems. This feature is in fact highly beneficial.

 

Now lets look at alternator regulators, and start with the internal/ external question. This is actually a red herring, it doesn’t matter where the regulator is, just what it does. However, in practice, the majority of internal regulators are designed to charge batteries fitted in vehicles or plant, a similar load characteristic to the engine battery on a narrow boat. They are not intended to recharge the large domestic batteries usually installed at the longer periods of high current required. The upshot of this is that external regulators are usually a better bet for domestic battery charging but more of this later...

 

Now the “digital” thing that is quoted in the sales blurb for high cost alternator regulators… Charging a battery (analogue) from and alternator (analogue) driven by an engine (analogue) is really best achieved by an analogue regulator. It’s not that a digital regulator is inferior, just unnecessary and unduly complicated. There are long-term benefits to be had (let alone cost savings) by keeping it simple.

 

Now let’s skip back a bit and look at the issue of compensation for the wiring losses with an alternator charging system. As stated earlier, the majority of alternators fitted to narrow boats were originally designed for vehicles or plant and have a fairly rudimentary regulation system that merely prevents the alternators output from exceeding a preset level. Since it only takes about 0.1 ampere hours to start an engine, this is easy to replace and could almost be done with a bicycle generator! Recharging a typical 440 ampere hour battery (bank) that is only half discharged will require over 2000 times the power.

 

The problem comes from the sustained high current the alternator has to provide to achieve this. The losses in the alternator and the associated wiring a proportional to the square of the current, i.e. if the charging current is raised from 25A to 100A the losses don’t rise by a factor of four, they go up sixteen fold! There are two undesirable side effects of this, the resistance of the wiring, connectors and any split charging system to the battery limits the charging current and as well as this, a lot more heat is generated (the losses).

 

The limiting effect of the circuitry between the alternator and the battery can compensated for by a battery sensed regulator system (be it internal or external). With this system the regulator measures the actual battery voltage rather than the alternator output and controls this to the required voltage when the power is available. It is known as a closed loop control system and for this there has to be a sensing wire to the battery positive to feed the information back to the regulator. If the alternator has an internal regulator without a sense terminal it will have to be modified internally, this is best left to a professional. Ideally such systems also have the ability to be preset to a charging voltage suitable for the batteries used.

 

The downside of this (and any other method of increasing the charging current) is that the alternator will inevitably run much hotter but there is nothing that can be done about this. The consequence is that the alternator life will be reduced but since they are generally made to operate for a number of hours that relates to a lifetime of cruising it rarely matters much. Having said this it is a good idea to keep a careful watch on any alternator that has been modified to a battery sensing system for the first few hours of it’s operation. If you wet your finger and touch the alternator stator after it has been running at speed for 30 minutes or so and it hisses, it’s probably too hot. Ditto if the smoke escapes…

 

Finally and in answer to the original post, if it is reasonably cheap and feasible with your alternator (but you didn’t say what sort it was) it may be a good idea to modify it to battery sensed. It would tend to charge your batteries more effectively providing more stored power should you need it and in addition it would tend to prolong the life of the batteries significantly.

 

Don’t feel inadequate if you don’t have a digital, all singing and dancing highly expensive battery management system. 100Ah in and 101Ah out equals misery, 100Ah in and 99Ah out equals comfort.

 

Hope this helps, I'm off - I can hear the Stukas coming....

 

Regards

 

Arnot

[Gibbo]

I'll go along with everything Arnot says apart from this bit.....

 

"It’s not that a digital regulator is inferior, just unnecessary and unduly complicated"

 

The reason almost everything is designed with "digital" these days is because it is:-

 

A. Easier.

B. Cheaper.

C. Simpler.

D. Quicker.

E. More reliable.

F. More versatile.

G. Better in almost every single aspect.

 

And finally, when (not if) the first manufacturing run is wrong (it ALWAYS is) it can almost always be corrected with a software update instead of manually modifying each unit.

 

Gibbo

[magnetman]

so is it no longer possible for hardware to be faulty?

 

 

(I see now yout said 'can almost always')

Edited July 6, 2008 by magnetman