Dead batteries - do I have a charge problem...

[Chris_Robb]

I have no diodes. I have no idea how the Sterling alternator to battery charger works. Certainly an amplifier to get from 14.4 to 15.0 volts. But mine does drop the voltage to 13.6 - 13.8 volts when the batteries are fully charged.

Well there we have the difference - I have their charge controller (or booster) and you have the Alternator to Battery charger, I have no idea how this works - glad to have got to the bottom of that then! I will look at the details to understand it!

 

[Chris_Robb]

I have no diodes. I have no idea how the Sterling alternator to battery charger works. Certainly an amplifier to get from 14.4 to 15.0 volts. But mine does drop the voltage to 13.6 - 13.8 volts when the batteries are fully charged.

Just had a read of this product - sounds very interesting - and so simple to fit. Right up the street for a friend of mine who has just bought a 1994 boat with the usual charging problems.

 

[lenseman]

I have no diodes. I have no idea how the Sterling alternator to battery charger works. Certainly an amplifier to get from 14.4 to 15.0 volts. But mine does drop the voltage to 13.6 - 13.8 volts when the batteries are fully charged.

I think you will find that the Stirling, like all of the latest generation, intelligent', battery chargers on the market today rely on what is known as PWM (Pulse-width Modulation charging). They actually charge at a higher voltage than 12 volts into a 12 volt battery but for very limited time and the pulse-width changes with the charge state.

It works in a similar way as a microwave oven does when on 'defrost'. Even though you are using the microwave oven in defrost mode, it still runs the magnetron at maximum power but is quite short bursts continuously switching the magnetron on and off. You can hear the magnetron switching on and off or rather you can hear the noise created by the inrush current into the large transformer which supplies the magnetron.

 

[prv]

Sorry to hijack the thread slightly, but it is related and seems better than yet another battery thread showing up in the forum...

I'm considering fitting a SmartGauge/SmartBank to KS at some point. This is an esoteric box of black magic, but for the purposes of this discussion we can treat the SmartBank part of it as a simple voltage-sensitive relay.

In this system, the alternator is connected to the engine battery. The relay then bridges in the domestic battery in parallel once the alternator is charging[1]. Regulation is all done by the alternator.

My question is what happens when the engine battery is already nearly full (having only had to start a healthy engine with a quick burst of power) and the domestic is low. Will the regulator "see" a demand for a full charging voltage or some "mixture" of high and low demand? If the latter, will this slow down charging of the domestic? If the former, will the engine battery be overcharged as the voltage stays high to fill up the other one? As you can tell, this is an area I know little about.

Cheers,

Pete

[1] Actually I think the SmartBank lets the engine battery charge alone for a little while first, but that shouldn't matter here.

 

[RAI]

but for the purposes of this discussion we can treat the SmartBank part of it as a simple voltage-sensitive relay.

Were it just a VSR, it would work something like this.

The alternator starts charging the first bank and raises its voltage slowly to the VSR trigger voltage (probably 13.6 volts).

On reaching the switching voltage, the VSR connects the second bank. The alternator charges both.

Since the second bank is at a lower voltage than the first bank, most of the current goes there.

Without any further control, the alternator will offer the batteries 14.4 volts (about) and the current flow will decrease until the batteries are full and essentially also at 14.4 volts.

Further charging, at this voltage, will start extra gassing and use up water, but is not that harmful but still undesirable. It would be better if a controller intervened and held the voltage at about 13.6 volts to reduce gassing.

 

[Chris_Robb]

Sorry to hijack the thread slightly, but it is related and seems better than yet another battery thread showing up in the forum...

I'm considering fitting a SmartGauge/SmartBank to KS at some point. This is an esoteric box of black magic, but for the purposes of this discussion we can treat the SmartBank part of it as a simple voltage-sensitive relay.

In this system, the alternator is connected to the engine battery. The relay then bridges in the domestic battery in parallel once the alternator is charging[1]. Regulation is all done by the alternator.

My question is what happens when the engine battery is already nearly full (having only had to start a healthy engine with a quick burst of power) and the domestic is low. Will the regulator "see" a demand for a full charging voltage or some "mixture" of high and low demand? If the latter, will this slow down charging of the domestic? If the former, will the engine battery be overcharged as the voltage stays high to fill up the other one? As you can tell, this is an area I know little about.

Cheers,

Pete

[1] Actually I think the SmartBank lets the engine battery charge alone for a little while first, but that shouldn't matter here.

Hi - Yes the alternator initially charges the engine battery and as soon as that reaches a preset voltage (13.8?) it connects the domestics in parallel. So all the batteries are now effectively in one bank.

I think the draw back of this system is still the output of the alternator where it seems that most modern automative origine alternators are regulated to 14.2V, which is not really high enough for lead acid, giving something like a 40% charge rate less. (14.2V - 12.7V = 1.5V diff and 14.8v- 12.7v = 2.1v diff So the difference of 0.6v expressed as a % of 1.5 represents a significantly lower charging potential - especially as the batteries approach higher charge levels. So still room for the alternator boosters despite what smart bank say.

Having seen the spec of the Sterling alternator to BATTERY charger - which does away with the need for a link between the engine and domestics - I think that this is the way to go, especially as it is simple to fit, and does both the boosting of voltage AND splitting to the 2 batteries sets.

 

[prv]

Since the second bank is at a lower voltage than the first bank, most of the current goes there.

Thanks - I think this is the crucial wrinkle that I wasn't sure of. So a full battery avoids being overcharged, even at a higher voltage, provided there's an empty battery in circuit to take most of the current?

It would be better if a controller intervened and held the voltage at about 13.6 volts to reduce gassing.

Would the regulator in the alternator not do this? If not, why not?

Pete

 

[Chris_Robb]

Would the regulator in the alternator not do this? If not, why not?

Pete

Because its designed for the Automotive industry. They are not usually clever controllers. Do go and have a look at Sterlings Alternator to Battery Charger - it has everything you want

http://www.sterling-power.com/products-altbatt.htm

 

[RAI]

Thanks - I think this is the crucial wrinkle that I wasn't sure of. So a full battery avoids being overcharged, even at a higher voltage, provided there's an empty battery in circuit to take most of the current?

That's my understanding. The battery's back EMF ensures that there is only a small voltage difference to drive the current through. As it rises, less voltage difference, less current.

Would the regulator in the alternator not do this? If not, why not?

I think the majority of alternators are just regulated to constant voltage output. Some of them enable an external controller to be connected and can then do things like constant current charging. Some don't provide the contacts to do that and clever people like Mr. Sterling find ways of tricking such alternators into being controllable.

 

[Ruffles]

Because its designed for the Automotive industry....

More to the point it's designed for the automotive industry of the early eighties! My ancient Octavia's alternator manages 14.? volts at idle. The alternator on our VP2030 is barely charging at the same speed.

 

[DavyMac]

Thanks - I think this is the crucial wrinkle that I wasn't sure of. So a full battery avoids being overcharged, even at a higher voltage, provided there's an empty battery in circuit to take most of the current?



Would the regulator in the alternator not do this? If not, why not?

Pete

I think the SmartBank/SmartGauge people are of the view that in most applications charging doesn't happen for long enough to cause an overcharging problem. Clearly this will depend on usage - it may be more of an issue if you're running the engine for 10 hours a day every day and not using anything like the current you'd be putting back in.

There seems to be a lot of differing views on the science of lead acid battery charging, and some 'experts' seem to be of the view that charging above about 12.6 or so volts doesn't help and can actually be a hinderance. I think that SmartBank may be in this camp, Mr Sterling obviously isn't. The fact that their device will complement an alternator booster does at least suggest that this is a genuinely held view and not a claim made just to sell something but frankly I don't know.

Almost as bad as anchoring this ;-)

 

[Stu Jackson]

Regardless of whether your near Greenwich of San Francisco, 12 V batteries need the same things.

Here are references for you:

http://www.westmarine.com/webapp/wcs/stores/servlet/westadvisor/10001/-1/10001/Battery-Charging.htm

http://www.amplepower.com/tech_docs/index.html Click on the Ample Power Primer. The wiring diagrams are helpful, too. One shows a simple 1-2-B switch application. As Vic is fond of noting, us "west" longitude guys are fond of supplying the alternator output to the house bank directly with a relay to the start (reserve) bank and around the 1-2-B switch. You UK folks prefer to go to the start bank first. The disadvantage of routing the alternator output through the 1-2-B switch is that it could be turned or turned off potentially frying diodes. The advantage is that if you have a problem with battery charging, you can use the switch to turn off the power if you have a runaway battery with your engine running. I find a simple circuit breaker with a switch on the alternator output to the house bank preferable than running the charging through the switch.

Many choices: your boat, your choice.

Battery acceptance is an important feature of charging. Batteries will only "accept" a certain amount of charge and as they get fuller they accept less current.

Three stage regulators have been used to control alternator output and these have replaced the old internal constant voltage alternator regulators which were designed for automotive applications. The new external regulators provide the smart three stage charging discussed in the links above.

 

[ianj99]

The charging voltage tells you nothing about the capacity of the battery and this reduces with age and how the battery has been treated. E.g if discharged below 50% on a regular basis, or left discharged or partially discharged for long periods the actual useable capacity will drop rapidly.

If a flat battery reaches a high charging voltage rapidly, this is because it is not taking a charge or if you like: its capacity is now so small that it has charged up fully.
A good flat battery will not reach 14.2volts for possibly several hours (depending upon the charging current and actual capacity).

So in your case, the batteries need changing as their actual capacity is now a fraction of what they were when new.

I think many owners don't appreciate that the actual capacity is never in practice, what is stated on the label and the older the battery and the worse its been treated, the less capacity it will actually have. So its not the fault of the charging system!

 

[Playtime]

I think many owners don't appreciate that the actual capacity is never in practice, what is stated on the label and the older the battery and the worse its been treated, the less capacity it will actually have.

Agree

So its not the fault of the charging system. !

Disagree. The way a battery is 'treated' over its lifetime is directly related to the quality, or otherwise, of the charging system.

 

[ianj99]

Agree



Disagree. The way a battery is 'treated' over its lifetime is directly related to the quality, or otherwise, of the charging system.

Yes you are right the charging system is crucial and often not adequate, but I was referring to the way owners treat the battery.
In that they do not ensure it is recharged promptly and sufficiently and tend to assume that the original capacity will always be available until the battery suddenly dies.

This ignorance stems from the fact, I believe, that we only think of lead acid batteries in automotive terms where the alternator quickly puts enough charge back in to ensure there's enough to start the engine whilst providing all the power actually needed by the vehicle.

Boat and motorhome owners soon find out that they need to pay a lot more attention to battery charging. Some just think a larger capacity is the answer but fail to consider adequate charging.

 

[noelex]

There seems to be a lot of differing views on the science of lead acid battery charging, and some 'experts' seem to be of the view that charging above about 12.6 or so volts doesn't help and can actually be a hinderance.

Almost as bad as anchoring this ;-)

I have never seen a battery manufacturer recomend 12.6V. My own gel cells have a recomended charge of 14.7 boost dropping back to 14.1 for absorption.
You did warn than this might deterirate like an anchoring thread, but 12.6 has to be a misprint.

 

[Chris_Robb]

I have never seen a battery manufacturer recomend 12.6V. My own gel cells have a recomended charge of 14.7 boost dropping back to 14.1 for absorption.
You did warn than this might deterirate like an anchoring thread, but 12.6 has to be a misprint.

Quite - actually a discharge! probably a troll

 

[theforeman]

... probably a troll

i think you do davymac an injustice. despite the post you replied to davymac never referred to battery manufacturers. he used the expression " experts " ( note the inverted commas in his post ). perhaps you may like to read his post again.

 

[Stu Jackson]

Yes you are right the charging system is crucial...

In that they do not ensure it is recharged promptly and sufficiently...

Quite right!

Another reference source is this: http://balmar.net/PDF/2005-mc-612-manual.pdf

 

[halcyon]

I have never seen a battery manufacturer recomend 12.6V. My own gel cells have a recomended charge of 14.7 boost dropping back to 14.1 for absorption.
You did warn than this might deterirate like an anchoring thread, but 12.6 has to be a misprint.

All you need is 14.2 / 14.4 volt regulator in the alternator, and a charge rate of 10 / 20% of battery capacity, and charge early.

Monitor volts and amps, when you have 14.2 / 14.4 volt, with low amps, that is about as much as you will get in the battery. Motoring, to recharge batteries, for longer will not put much more into the battery, so is not economical just to gain another 1 /2% capacity.

Three stage charging, and high charge rates do not work, we proved this in 1983 when we designed our first multi-stage chargers. We spent most of the 1980's testing three stage charging, and it only acted as a fudge to incorrect primary charge cycle.

Brian