Alternator regulators

[Guest]

Should I buy one of the new Digital Sterling rgulators or is the 'old' type OK please?
I have two large end terminal batteries on my dutch steel boat, one for domestics and the other for starting and bow thruster. I am replacing the domestic 165AH unit this spring with a proper domestic battery - will the Sterling regulator do both batteries? I hear they are very good

 

[John7]

I have an 'old' regulator charging two 75Ahr batteries. I have fitted a switch on the sensor wire so I can switch the Sterling out if I know the full charge isn't needed. I haven't been able to fine out any thing about new controllers as the web site i can find is still under construction (1998?!). But the problem with the 'old' one is the charge cycles are fixed times and if you need more, or less there is nothing you can do other than fitting a switch or turning the engine off to reset the sterling back to boost.

I wouldn't fit one of the old ones again but having said that am rewiring my one onto a new engine as its better than the regulator fitted as standard. If they have improved the control a new one might well be worth fitting as new, but compare its specs with others, one that has a programmed charge based on the condition of the battery rather than timer is better.

 

[Guest]

I did not explain that the 'old' Sterling unit I am thinking of buying is brand new but new digital ones are also available now. Old ones are £40+ cheeper and that appeals!

 

[softop]

I wouldnt have a Sterling reg again. I wrecked 400 A Hr battery bank last year,when I checked the charge voltage it was over 16 volts! When I phoned Sterling the guy on the other end put the phone down on me and I wasnt being rude! You get what you pay for, look around there are much better units available. Take a look at the Balmar website balmar@balmar.net

 

[HaraldS]

I have an analog Sterling, but haven't seen the new digital one, so can't comment on it. The analog one I would class as ok, but not particularly great. Voltage levels are not kept very accurate and staging appeared a bit dubious. I'm keeping mine as a spare right now.

Modern regulators seem to all be digital and I think they are probably cheaper to produce, still the accuracy and quality will depend on a few analog parts.

The Sterling has the advantage that it works with almost any alternator. On those with built in regulator, Sterling propose to have theirs work in parallel, so you have fault tolerance. But this is only good on the assumption that the Sterling would always ask for more power, never less. In the later case it will end up with what the built in regulator determines.

Further alternators may be positive or negative excited, some may allow both. The Sterling regulator can handle both modes. All the Balmar regulators that I have seen work only with positive excited alternators.

All these multi stage regulators do in essence the same, but more or less accurate. The idea is to have you alternator work at full power as long as the battery can accept such current without gasing. In practise this is possible up to about 85% charge level. All regulators determine this level by measuring the voltage.

There is a set of problems: If the voltage is sensed at the alternator, it may appear higher than the actual battery voltage because of the voltage drop on the wire from alternator to battery and possibly an isolation diode. The result is too slow charging, but it will not damage your battery. The fix is a separate sense wire from the regulator to the battery and good regulators have separated sense from regular plus, so has the Sterling.

The 'right' voltage level is dependent on battery type and should be settable. The Sterling has two settings GEL and other, which is generally good enough. Digital regulators allow you a wide range of programmable voltage to best suit your particular battery.

Another factor determining the 'right' voltage is the temperatur of the battery, and some good regulators have a temperature sensor for the battery. The (analog) Sterling does not have that.


Producers of these regulators and chargers tend to give different names to the different stages, but in essence they are doing the same. Loading at full alternator power up to that magic voltage is often called boost, bulk charge phase. Once that is reached the voltage is kept constant and the battery accepts less and less current over time, until it is eventually full. The strategies to detect that fact are different: Most use time, which is a problem if you stop your engine and restart, and it is not very accurate. So they are all playing it safe and switch to float state after say half an hour, which probably means your battery is about 90% charged, from there it creeps forward at float charge level, which is a voltage level that will never cause gasing, even when the battery is full.

Very few measure the current that the battery still accepts and use that to determine when to advance to the next stage (float). (another magic level of about 1 amp per 100Amp hours of battery capacity).

On most non GEL batteries you also need an equalization phase once and so often, to stirr up the electrolyte and prevent sulphating plates.

Allthis may not matter much if you have a good shore power charger and if you are connected reasonably often for a night.

If you need to be very self sufficient on your power generation, these details deserve more thought.

In short, the digital ones give you a lot of values to play with and still you might not be able to do evrything you want.

Finally, some regulators have a slow ramp up, so they do not put load on the cold engine and avoid slipping belts, and some also have temperatur sensors to protect alternators from overheating. The later is a desease of the ultra compact high power alternators, like some of the Balmars, but usually not a problem for regular ones. Consequently Balmar regulators have that feature.

 

[Guest]

Thanks to you all for the infinite knowledge on this subject. Seems like there is more to this than meets the eye. Can anyone confirm if I can use a Sterling on two batteries or is it only for use on one - say the domestic 'semi traction' battery I am about to fit? I only have one alternator on my single engine.

 

[HaraldS]

Not so simple: A standard automotive regulator just regualtes to one voltage, in the range of the float volatge, that all batteries except Gel can absorb indefinitely. So Batteries in parallel are helping themselves, but get charged very slow.
For a starter battery that's fine since it is never discharged much and just needs topping up after starting.
If you apply differnt load patterns to your batteries, they would need different treatment, especially when you want to optimize charge time.
There are different ways of separating batteries: Splitter diodes or automatic separator switches. Diodes are very reliable but cause a voltage drop, switches are more expensive and more error prone. With diodes an standard automotive regulator will fail, since the voltage drop off about 0.7 Volts on the diode will mean an even lower voltage on the battery (about 13V), so it will barely charge.

So a separator switch with an automitive regulaor will work, but as bad as before.
A Sterling regulator can sense the voltage at the battery and can compesate for the voltage drop and work just fine. Except that it could overload your engine battery, as it will be directed mainly by the emptier battery.

To avoid that problem, you could put an additional diode in the wire that feeds the engine battery. It will cause enough voltage drop, to make things about right for the topping up job.

Easiest would be to use just one diode twoards the engine battery, it will prevent current to flow back from the engine battery into the domestic circuits, and you could connect the domestic batteries directly to the alternator output. The problem with that is that while you are cranking, the engine battery voltage will drop quite low (like 8V) and the domestic battery will try to help. While that sounds like a nice feature, you would need a very powerful diode, or several of them in parallel. Not too practical.

So you will need a diode splitter (or the switch) and in addition a single diode added to the engine battery feed.

There is also the option to charge one bank after the other. Having this work automatic is also more complicated, doing it manually with battery switches is possible, but error prone. You might forget to cut of the engine battery after some time, or end up with no battery connected which can kill your alternator.

Hope this helps.

 

[stevebirch2002]

I am afraid i disagree. I found the Sterling Booster very good. I have now fitted them on over ten boats and never had a problem. Sterling are very knowledgeable and have always answered any queries I have had.

Steve Birch

Albin Vega "Southern Comfort" V1703

 

[Guest]

Steve, sorry to sound thick but what do you mean by 'booster' - 'alternator regulator' or a 'charger' please

 

[stevebirch2002]

The booster is an Alternator Regulator. Sterling etc.

Regards


Steve Birch

Albin Vega "Southern Comfort" V1703