The "Truth" about batteries?.......or

Submitted: Friday, May 05, 2006 at 06:30
ThreadID: 33554 Views:2598 Replies:2 FollowUps:8
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Hi all,

I came across this thread when chasing battery monitors.Whilst the

thread originates from the boating fraternity, it raises several

issues which maybe relevant to 4wd.

Battery Monitor Thread

Quote:William_H

I feel obliged to make a comment. One thing you don't want on any

boat is more electronics. It usually means more worries and

dissapointment.
Yes with the aid of modern microcontrollers it is possible to very

accurately measure current over time into and out of a battery. but

what does that really tell you? The actual amp hour capacity of a

battery is a very variable quantity. In aviation in estimating the

time a plane could fly on battery alone, we ( government

legislator) used a factor of 55% of manufactyurer rated AH capacity

of battery. ie thats all you can reasonably rely on from a lead

acid battery during it's life. ie until it won't crank the engine.

( even that is a very subjuective guess. It is likely when

considering large capacity house batteries that the capacity could

fall far lower before you really noticed a problem. (especially for

those religiously never discharging below 50%) modern batteries may

be better but then in parctice many batteries may be found worse.
So while amp hours in and amp hours out might be interesting it

doesn't mean that you ca n get all the current out that you put in

or that the battery has anything like the capacity you may have

programmed into the device. ( or expect) So there is a contrary

opinion just so you don't go off thinking you have to have one.

regards olewill

Unquote:

Quote:jerryat

Hi Will!

I entirely agree with you!! We do not rely on the 'zero amps' of

the Battman to tell us the batteries are 'fully charged', as we are

fully aware that a good 10% or so extra is needed to achieve that!!

But what pretty well all these gadgets do, is give you is a better

'idea' of the state of play and that's extremely useful IMHO. We

never discharge our batteries below 10-15% of apparent capacity and

as a consequence, they last us for many years.

No, the MAIN reason we installed one, was to measure as accurately

as possible (short of fitting a temporary ammeter in line to each)

the real current consumption of every piece of electrical equipment

on board.

Frankly the results were staggering. The manufacturers claims were,

almost without exception, for much lower consumption (in some cases

hugely so) so that any reliance placed on our total usage based on

their figures, would have been useless. OK, that doesn't matter

perhaps if you're basically weekending your boat, but when long

term cruising it's crucial!

The fact that the unit also gives us an accurate 'at a glance'

battery voltage was another factor in our decision to install one,

and our Battman has now been aboard for 13 years and done 40+

thousand miles, so we are happy with it's long term reliability

too!!

So don't worry,we haven't 'gone off' thinking we have more than

we've got!!

Cheers Jerry

Unquote:

This goes a long way to explaining why there are contradictory

experiences in battery threads, in particular

[William_H]So while amp hours in and amp hours out might be

interesting it doesn't mean that you can get all the current out

that you put in or that the battery has anything like the capacity

you may have programmed into the device.

So......are these comments FACTUAL?

eng
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Reply By: Wok - Friday, May 05, 2006 at 06:39

Friday, May 05, 2006 at 06:39
Sorry,
Link doesn't work.....Google Search " VDO Battman III"
eng
AnswerID: 170833

Reply By: Mainey (WA) - Friday, May 05, 2006 at 22:40

Friday, May 05, 2006 at 22:40
Battman III VDO battery monitor $475

My $200 Steca Solar regulator tells me amps going in and out
battery "State of Charge" as a percentage (%)
and also battery voltage :-)

I think the Battman III may be a bit overpriced.

AnswerID: 171063

Follow Up By: Member - Mike DID - Saturday, May 06, 2006 at 08:30

Saturday, May 06, 2006 at 08:30
Unfortunately you can't use a Steca Regulator between a Car Alternator and a car battery because the Steca puts the current sensing resistor in the earth lead

Mike
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FollowupID: 426526

Follow Up By: Mainey (WA) - Saturday, May 06, 2006 at 09:55

Saturday, May 06, 2006 at 09:55
Mike, as your aware the Steca Solar Regulator is not intended to be used in the way expressed, as it’s only rated up to a maximum 30 Amps, making it absolutely imposable to be used in the alternator/battery cable, but oh just so purrrfect for its sole intended use as a feature packed LCD screened Solar Panel charging regulator.

However I reiterate; the Battman III is overpriced for what it actually achieves, when the purchase price is compared with that of said Steca Solar regulator :-))
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FollowupID: 426545

Follow Up By: Wok - Saturday, May 06, 2006 at 19:13

Saturday, May 06, 2006 at 19:13
Mainey,

Any suggestions on alternatives to the Battman that is better priced?[seen the Link 10]

I didn't start the thread about the Battman, I was researching battery monitors when I came across the YBW thread[ sorry I don't know how to link it properly]. It just struck me as odd that in battery charging threads[ particularly solar] there is no mention of overating the panel c.f the amp-hour usage....at least none that I recall?

I noticed Derek has a monitor listed in his products but without brand & specs it is impossible to research without annoying him.

If the YBW thread is accurate then I would agree that having such a "tool" is of wanking value only....hence the question

rgds.......eng
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FollowupID: 426641

Follow Up By: Member - Mike DID - Saturday, May 06, 2006 at 19:26

Saturday, May 06, 2006 at 19:26
But notice that the YBW thread doesn't suggest any better alternative !!! Decent amp-hour meters will in fact take into account all sorts of factors, Peukerts Law, battery Charge efficiency etc.

All modern Battery Gauges used in Laptops, PDA's etc are based on Accumulated AmpHours.

Because there is such a gap in the market, I've thought of developing a commercial unit - I should have the time now that I'm retired !

Mike
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FollowupID: 426643

Follow Up By: Mainey (WA) - Saturday, May 06, 2006 at 20:54

Saturday, May 06, 2006 at 20:54
Wok, I use my Steca LCD screen to tell me whats happening with my Aux battery system, I also have an Expanded Voltmeter, 10v to 16v, ($39) wired to the Aux battery system and also an Expanded Ammeter, -10 to +10 ($39) wired between the Aux battery system and the Steca Solar regulator, this tells me the actual Amps going into or out of the Aux battery system.
All three guages are grouped together so I can see instantly the complete State of Charge or discharge of my Aux battery system.
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FollowupID: 426657

Follow Up By: Wok - Saturday, May 06, 2006 at 21:59

Saturday, May 06, 2006 at 21:59
Mike,
I guess no alternative is suggested because the other players are more expensive or part of larger systems.

I am not sure if it would be worth your effort to produce an instrument that could not be universal at installation without the user needing to calibrate the product to his/her battery-bank[ aka Battman]. I base this on the comment that " input amp-hours ≠ amp-hours available" ; perhaps there is a loss in the chemistry.....? how much?How would an instrument compensate for this?
One of the authors quotes 10% as satisfactory in his system.

The second point that was brought up was that a quoted 100Ah battery would be unlikely to have this capacity [I expect the capacity would deteriorate over time anyway, but how would an instrument be able to monitor this without the user having to load test the battery @ regular intervals?

Mr.DID ....you have a challenge!...............produce a unit for $9.99 & I will be BUYER NUMBER 1
===========

Mainey,
You opened your post by saying the Steca monitors voltage & current, why the need for extra instruments, or am I misreading your setup?

rgds all.......eng
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FollowupID: 426672

Follow Up By: Mainey (WA) - Sunday, May 07, 2006 at 10:23

Sunday, May 07, 2006 at 10:23
Good question, the honest answer is: I'm lazy :-(

I leave the Steca LCD screen displaying the Deep Cycle battery system “State of Charge” in the percentage (%) mode.

Unfortunately with the Steca regulator you have to press a 1/2 inch square button on the instrument to change the relevant information screens and because my Steca regulator is mounted on the vehicle internal far wall, opposite the door and above the fridge, about 1.4 metres from the door, I’ve chosen to install the Voltage and Ammeter gauges directly underneath it as a group.

Remember, the ammeter is registering the Amps going in/out of the Deep Cycle battery system, and showing it by a swinging neadle sitting above a number, eg; if the Solar panel is putting 9 Amps into the battery and the fridge & accessories are NOT running, the ammeter will show 9 Amps on the positive (+) right side of the meter, however if the Solar panel is putting the same 9 Amps into the battery system and the fridge is actually running it will show as only 1 Amp on the same positive (+) right side.
If the sun is low or it’s cloudy and only 6 amps is being produced at the Solar panel, then when the fridge is actually running the ammeter will show 2 Amps on the negative (-) left side.

The Voltage meter display is the Deep Cycle battery system voltage and therefore does include ‘surface’ voltage as the Steca regulator is always putting the available Solar panel Amps into the battery system during the day, you can watch the voltage needle move as the clouds eliminate the sunshine from 12+ up to 14+ volts during the day depending on the regulator charging programme being implemented at the time, eg; boost etc.
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FollowupID: 426735

Follow Up By: Wok - Monday, May 08, 2006 at 02:42

Monday, May 08, 2006 at 02:42
Mainey,

Thanks for the clarification, I have avoided mobile phones for much the same reason....too fiddly.

eng
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FollowupID: 426861

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