How many amps can a battery bank take?

[ QUOTE ]
So, from what you're saying, it might be better to run the engine for a little longer but every 48 hours, rather than 24? This way, my shortfall will be about 80 amps or 22% of (domestic) battery capacity. Does this make sense?

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Yes it does make perfect sense, but even at 78% you're going to have trouble getting that last bit in with the engine. This is why many people recommed having 3 times the capacity you expect to use as realistically it is not easy to get a battery up to 100%. Fine if you have a good charger and spend all night plugged in, or you're motoring for long periods and the charging is just consequential, but using the engine as a generator in these circumstances it will be difficult to get it all to add up on paper in the same way it will actually turn out in reality.

220A/h a day does seem a lot though, I would just go with the dugeon and solar panel and keep an eye on the battery voltage and top up with the engine when it gets low to maximise efficiency, rather than trying to run for a specific, pre-calculated time per day. You'll probably only get about 75% of the alternators rated output at acceptable revs, 10% or so of which will be lost to the void. As soon as your regulator(smart or not) starts regulating this, you're wasting fuel which could be better spent another time when the batteries are able to accept it all.
 
What?

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As soon as your regulator(smart or not) starts regulating this, you're wasting fuel which could be better spent another time when the batteries are able to accept it all.


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Don't understand this - do you know what a smart regulator does?
 
Re: What?

Basically a true statement, once you start regulating to maintain a fixed voltage you start loosing amps. Back in the early 80's when we were developing multi-stage chargers, we found that if the nominal charger output was 10% of battery capacity, equalization charging was a complete wast of time. Once you started the fixed voltage run, the charge rate would drop from 25 amps to 2 amps in around 3 minutes. Charging at a very high rate will put a lower % charge into the battery for a given voltage, thus equalization charge will put in the missing amps, but by running at high voltage for protracted periods. But still on a declinning rate.

Brian
 
Re: What?

You seem to be saying that it's true to say that when a smart regulator increases the alternator's voltage so as to increase the charge rate, this wastes fuel.
 
Re: What?

No, once it starts regulating the voltage when it enter's it's equalization phase, your charge current is decreasing, thus you are spending increasingly more £'s per amp that you put into the battery.

Brian
 
Re: What?

The man said,

once your regulator starts regulating,

this means controlling the output to maintain a fixed voltage, your charge amps falls, thus you have the law of demissing return.

What bit is confussing?

Brian
 
Read the post...

Read the post. What he actually said was "As soon as your regulator(smart or not) starts regulating this, you're wasting fuel...". A smart alternator regulator (such as Adverc, Sterling, etc) will increase the charging voltage, thus increasing the charging current, so as to maximise charge efficiency. There's no way this equates to wasting fuel.
 
Re: Read the post...

I think that what he was saying is that when the bulk charge is going in you are putting a lot of AH into the battery. After that stage the amount of power going into the battery is reduced and therefore your use of fuel becomes relatively less efficient. Using a smart charger will give you better results, but it will still be putting in less than when bulk charging.

That's how I read it anyhow. It makes sense.
 
Re: Read the post...

I think people are getting confused here by the differences between mains-powered chargers and engine-driven alternators. An alternator controlled by a smart regulator such as the Adverc can only have its normal charge rate increased by the smart regulator. In contrast, mains-powered chargers can drop to a lower float voltage (and hence a minimal charge) once the absorption phase is over. As the original query was about using the engine to charge batteries in mid-Atlantic, we're obviously looking only at smart alternator regulators which, once they start working, can only increase the charge rate.
 
Re: Read the post...

I'm not sure if we're talkng about different things here.
My understanding is that a smart regulator still pushes less POWER (i.e. volts x amps) into the battery in the later phases. It's more efficient than a not-so-smart regulator but it's still bunging in less than during the bulk phase and therefore costing more in fuel....which is the point that was originally being made...I think! /forums/images/graemlins/crazy.gif
 
Re: Read the post...

Last time I looked Stirling were using Bulk and float phases, and Adverc were using a pulse system that droped the voltage to a lower level to stop excessive gassing. In passing Hella were selling this sytem in the mid 1990's for cars to stop excessive gassing on load runs, at the time it retailed for around £60.


Brian
 
The lowest voltage....

The lowest voltage that either Sterling or Adverc alternator regulators can drop to is the voltage of the alternator's internal regulator (usually 14.0v). This is because both these products work in parallel with the alternator's own regulator - providing a useful failsafe mechanism if the Sterling/Adverc were to stop working.

In the US, some marine alternators do not have an internal regulator at all, and rely solely on an external regulator. In these instances, it's possible to have a smart regulator which offers a true 4-step charging regime, with a lower float voltage. An example of this is Balmar's unfortunately-named ARS-4 regulator, which drops down to 13.4v on float.
 
Re: The lowest voltage....

What's the point, if you regulate at 13.6 volt, or 14.6 volt, once you start the charge current will start to fall.

Brian
 
There\'s no point....

Seems there's no point continuing this, Brian. Like most people, I'm a firm believer in smart alternator regulators, which by increasing charge voltage can greatly enhance charging efficiency in the real world. Your argument that any sort of regulation causes charge current to fall seems to be purely academic, as I'm not aware of any alternators in boat use which don't have some sort of regulator fitted.
 
Re: There\'s no point....

pvb, all I was saying is that it is harder get the power back into a battery that is in a higher state of charge.

I am a firm believer in smart regulators too, but if you are using the engine as a generator then you want to be getting all the available amps into the battery. No regulator, no matter how smart, can force the kind of amperage you would expect in the bulk-stage of charging into an almost fully charged battery. Of course the whole process will be more efficient with a smart regulator, but you still get the most out of them in the bulk stage.

Do you not see the logic here, I am talking about the efficiency of converting diesel into electricity. You dont want to be running a 30HP engine to turn a 60A alternator if the batteries are only capable of accepting 20A. You would be better off using that same diesel at a time when the batteries can accpet the full 60A, no?
 
Ah, now I\'d agree with that....

Ah, now I'd agree with that, and in fact I'd already suggested that with a decent battery monitor to track exactly what the state of charge is, then "you might find that the most fuel-efficient charge regime during your trip is to let the batteries drop to say 65% of capacity and then recharge them to only 85-90% of capacity". Similarly, I'd also suggested a bigger battery bank, which is another good way of using the maximum available charge rate for as long as possible.

I only disagreed with your statement "As soon as your regulator(smart or not) starts regulating this, you're wasting fuel", but if that's not what you actually meant, then fine.

Smart regulators make a big (positive) difference and ought to be standard-fit on all new boats. Most new boats also have a woefully inadequate domestic battery bank, bearing in mind the trend towards heavy use of fridge, radar, plotter, entertainment, etc.
 
Re: This is getting complicated!

....and I'm a simple soul!

I can understand that I may have less battery storage than ideal but with the duogen (excluding the solar) I won't be taking much out of the batteries anyway - only about 2 amps per hour, assuming my cautious budget. The duogen then will be able to cope with just under 90% of my power. So if I take SvenglishTommy's point on board and run the engine for a few hours every two days (maybe even three) and ensure I don't fall below 50% of battery capacity, I'll be OK, right? I appreciate that even with the Duogen, I'm using power via the batteries, but this won't count as charging load on the batteries (will it?) since I'm using the power all the time.
 
Re: There\'s no point....

A regulator controls the charge system.

To regulate, it to limit the output voltage to prevent damage to battery, to do this you cut charge current. The higher the recharge level the greater the charge current is cut back as cell resistance is increasing as well.

I do not think anyone said increasing voltage would not increase recharge level.

But until a alternator reaches a regulation point, it is running uncontrolled, only limited by it's wattage output and the internal cell resistance of the battery.

Brian
 
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