Battery Charging Routine Basics

[deletedaccount]

Without wanting to speak too soon I think I've improved things a bit. Given what I've read here I experimented turning things on and off and seeing how it affected the meter and played around with reving the engine a bit.

 

When idleing the volts don't change (they were around 12 whith everything off). Tickover was the same. When I gave it a bit of wellie for a second or two it jumped up to 13 or so, and 13.2 with everything off. Whats more, the voltage has stayed there now that I'm idling again.

 

I know it's past eight but there's nobody around but the boat in front and they've got their engine on anyway so I'm going to leave it for a couple of hours and see where I end up. I've only got one set of lights on and everything else (apart from the traqvel powered laptop) is off.

 

Hopefully it'll improve my charging rate.

 

I'm going to get myself one of those ampmeters as well.

[pistnbroke]

Virtually everything said above is of no help to you..

 

 

1/ your batteries will not be fully charged unless you can get them up to 14.4-14.7v

 

2/ dont fit an ammeter as the voltage drop upsets the voltage regulator in your alternator ..they were never intended to be used with an alternator

 

3/ if you want to know charge current use the type of ammeter which goes around the cable ..prferably a digital one

 

4/ the max charge you can get into a 100ah battery is about 25 A so if you have 600ah you need alternator capacity of 150 A

 

5/ you may need to fit two alternators to get to this capacity ...the simple way to do it is fit a big switch to join the two B terminals [of the domestic and start alterantor??] and when you have run for 10 min to charge the strting battery throw the switch

 

6/ you need to have your alternator at 6000 rpm to get full output so chceck your engine revs and belt ratio...( with engine at max rpm the alternator should be geared for 12000 rpm)

 

7/ make sure its all linked up with at least 50 mm2 cable inc the cables to the alternator B terminals

Edited September 2, 2009 by Dhutch
Edited to add text in square brackets

[Smelly]

However getting anywhere near 6000 rpm on a narrowboat may be difficult... My pretty ubiquitous 35 horse Isuzu cruises at between 12 and 1600 revs so even if I pulleyed up to 3:1 I'd not be getting the apparently magic 6000 revs at the alt, niether I imagine would anyone else. My engine only goes up to 2500 rpm flat out and we don't want to be running flat out, ever...

 

Alternators seem to have developed around cars, so we can't hope to get the optimum out without a significant change of propulsion design so it's more a job of making the best of what we've got.

 

OP will prob have read by now that 14.4-14.7 is the best range for charging so the question is how to get there, if only charging; well trying to, at 13 ish then the voltage is the first thing that needs addressing.

 

Paralleling alt's is a good idea if you're consigned to living with the fact that batteries are consumable and the magic 100% charge point is for the most part un-achievable. Although you might squeeze in more amps early on, you still live with the interminable wait as the charge level drops. Bear in mind once the voltage gets up to 14.4 (well, actually the regulation voltage of one of the alternators) then one alt will be doing now anyway. That point is reached much more quickly the higher the amount of charge you squeeze in so there's not the economy in parallel alts if you're looking to maximise battery life as well.

 

I'd question the big switch method tho, again OP, best to wade through the paralleling thread pinned at the top of the equipment forum and make your own mind up. I'd reckong with a Sir Nibble within range you could manage a modded alt' regulator; assuming you're got twin alternators of course.

 

I think I'd be plugging the travelpower into the charger sharpish to get a decent charge in.

[pistnbroke]

It normal to have a 3 to 1 ratio with a diesel road engine so if your max rpm is 2500 then 5 to 1 would not be a problem to acheive

 

No need to mod regulators buy a Bosch RE55 external regulator you can fit a switch to it to give you a choice of voltages

[Sir Nibble]

Virtually everything said above is of no help to you..

 

 

1/ your batteries will not be fully charged unless you can get them up to 14.4-14.7v

 

2/ dont fit an ammeter as the voltage drop upsets the voltage regulator in your alternator ..they were never intended to be used with an alternator

 

3/ if you want to know charge current use the type of ammeter which goes around the cable ..prferably a digital one

 

4/ the max charge you can get into a 100ah battery is about 25 A so if you have 600ah you need alternator capacity of 150 A

 

5/ you may need to fit two alternators to get to this capacity ...the simple way to do it is fit a big switch to join the two B terminals and when you have run for 10 min to charge the strting battery throw the switch

6/ you need to have your alternator at 6000 rpm to get full output so chceck your engine revs and belt ratio...( with engine at max rpm the alternator should be geared for 12000 rpm)

7/ make sure its all linked up with at least 50 mm2 cable inc the cables to the alternator B terminals

Virtually everything said above is of no help to you..

Oh good grief, another one who is uniquely qualified.

1/ There is a period of time when the alternator is running flat out before the battery reaches regulated voltage. This is called bulk charge.

2/ A remote shunt ammeter will minimise cable volt drop leaving only the tiny loss across the shunt. Battery sensing will compensate for both. Many of us have just such a set up, and I don't mean sales victims, I mean competant engineers.

4/ This is not definative, max current is whatever the battery will take at regulated voltage.

6/ Most alternators give full whack at around 3500 rpm, many considerably less. (This sourced from a combination of manufacturers performance graphs and test bench readings).

7/ Weren't you scoffing at the idea of 50mm charging cables a short while ago?

 

OP, there is wildly varying opinion on all electrical matters, consensus does emerge and you will learn to identify those who really know what they are on about and have the qualifications and experience to back it up. I have before now taken components off the shelf and tested them and STILL had folk who have "read a book" tell me my readings are impossible. A good rule of thumb is to look at those who contribute to the debate and avoid those who simply declare that only they know and all the rest of us are fools. I would suggest that two opinions you can really trust are Gibbo and Arnot.

 

I now await being told that 35 years of experience as an auto and marine electrician count for nothing and I have been misreading instruments all this time.

[alan_fincher]

Our alternator charges virtually as well on idle, as it does when running at cruising speed. As we idle at a little under 700 rpm, and have a 3 to one pulley ratio, it can be doing little over 2000 rpm until the engine is opened up, (because that ammeter I musn't have tells me so!).

 

The performance graph supplied with the alternator new, (which I think was based on actual test measurements for that unit, rather than theoretical data), supported the fact that most of the output is already achievable at such low revs, and that you don't have to push it massively higher than that to achieve full output. It's not a fancy alternator - it was £40 on e-Bay.

 

Others will have different arrangements where this is not the case, (surprisingly it seems the alternators on many engines sold for marine use are only pullied at 2 to 1 - seems daft to me).

 

I totally support Sir Nibble - I suggest you listen to those with an established track record of working in the business, and who have consistently given the right answers.

 

Even for us amateurs, it is very easy to see from our own limited practical experience that blanket statements like "you need to have your alternator at 6000 rpm to get full output" are b*ll*cks, so even if other advice that someone is giving is good, how can you sort that from the stuff that can easily be proved as being nonsense ?

 

Ignore me, that's fine, because it's my hobby not my job, but ignore Sir Nibble, Arnot, Gibbo, etc at your peril. They do know their stuff.

[nb Innisfree]

As we are CCers there is no shore power available to us so we cannot charge our batts fully each day, several hours charging is fine on shorepower but financially unrealistic with an alternator unless you happen to cruise for long periods. At the moment to achieve a realistic charging regime with our slightly tired AGM batts we charge with alternator for 1.5 to 2 hours daily (partial state of charging) and do a full 6 to 8 hr charge every week or so. We have 2:1 reduction with a Leece Neville alt which gives full output at 1600rpm engine speed.

 

This is not a theory, it is what we do each and every day throughout the year and works very well. I must add to this that our alternator is better than most and quite large which charges at quite low rpm. A standard alt will need higher gearing as has been mentioned.

 

We use a battery monitor which tells us what amps and voltage is going in or out of batts, very useful.

 

We use 1.5 to 2 KW hrs per day depending on whether we use washing machine and we have no power supply issues (yet!)

 

There it is, a system that works very well with no drawbacks other than a reduced battery life, in these conditions expect cheap batts to last 18 months to 3 years, AGM or similar perhaps double this if you are lucky.

 

I am not an expert and have no qualifications but have planned this setup and after 4 years continuous use don't think I can improve on it, perhaps solar panels but financially a bit of a non starter really.

Edited September 2, 2009 by nb Innisfree

[churchward]

Our alternator charges virtually as well on idle, as it does when running at cruising speed. As we idle at a little under 700 rpm, and have a 3 to one pulley ratio, it can be doing little over 2000 rpm until the engine is opened up, (because that ammeter I musn't have tells me so!).

 

The performance graph supplied with the alternator new, (which I think was based on actual test measurements for that unit, rather than theoretical data), supported the fact that most of the output is already achievable at such low revs, and that you don't have to push it massively higher than that to achieve full output. It's not a fancy alternator - it was £40 on e-Bay.

 

Others will have different arrangements where this is not the case, (surprisingly it seems the alternators on many engines sold for marine use are only pullied at 2 to 1 - seems daft to me).

 

I totally support Sir Nibble - I suggest you listen to those with an established track record of working in the business, and who have consistently given the right answers.

 

Even for us amateurs, it is very easy to see from our own limited practical experience that blanket statements like "you need to have your alternator at 6000 rpm to get full output" are b*ll*cks, so even if other advice that someone is giving is good, how can you sort that from the stuff that can easily be proved as being nonsense ?

 

Ignore me, that's fine, because it's my hobby not my job, but ignore Sir Nibble, Arnot, Gibbo, etc at your peril. They do know their stuff.

 

I agree with Allan the guys he listed give good advice.

 

Our alternator though doesn't charge that well at idle RPM the amp output is not that bad but the voltage at idle is low only around 13.6V-13.8V a few more RPM and it will reach 14.6V-14.8V. Some of this effect may be to do with the Sterling Alternator to Battery Charger device I have fitted.

 

Personally I am not that keen on fitting an ammeter as I don't want a shunt in the cabling but that's just me and I certainly wouldn't fit an in-line one. I use one of the clip on devices when I want to measure alternator output. I do have a Smartgauge though which is a great bit of kit and very simple to fit. I think of it as my fuel gauge for the batteries it generally tells me all I need to know on a daily basis.

 

The original pulley ratio on my Beta was nearer 2:1 as well which wasn't great for amp output. I have since sourced a smaller pulley to go on the alternator and that has improved things quite a lot. You have to be careful though with very small pulleys as on a larger out put alternator they may not have enough contact area for the belt to get sufficient grip and cause slipping. From the specs of alternators I gave seen and how we use our engines on the whole you are unlikely to be able to over rev an alternator as they will spin up to 10,000 rpm give or take a bit.

 

Even so with my new pulley I get good and near full output (70 amp alternator) at normal cruising speeds and my batteries charge within a few hours each day. Normally the state of charge is about 70-75% in the morning.

[deletedaccount]

Well I managed to put more in than I took out last night with only a 1 and 1/2 hours charging via the alternator. I looked it up and it's a 110a jobbie and my batteries are 660ah not 600. Giving the engine a blast of revs at the start does seem to have made a difference. Maybe I've got that 'D' thing someone mentioned disconnected or something.

 

How do I go about plugging the travelpower into the inverter/charger? It's only a 50a charger but will deff help I think. Running an extension cable from a plug socket to the back of the box sounds a bit dodgy to me, Iif it's even possible.

 

So the things to look at now are ratios and the possibility of using my starter alternator (50a) in parallel with my domestic one (110a).

[JonL]

Now I'm no electical expert, but I've solved a number of problems over the years with the "take it all apart, give it a good clean and put it back together" approach.

Before you start re-wiring, adding meters and spending loads of money, give everything a good clean up.

It might just solve your problems.

[Sir Nibble]

Now I'm no electical expert, but I've solved a number of problems over the years with the "take it all apart, give it a good clean and put it back together" approach.

Before you start re-wiring, adding meters and spending loads of money, give everything a good clean up.

It might just solve your problems.

I've known that many times but generally it's because the strip and reassemble has re-made an undetected dodgy connection. Clean is nice tho'.

[deletedaccount]

Yeah, that's worked with computers a lot too

 

I am a bit worried that my batteries have never been above 12.8 or so though, even after 8 hours cruising. Could there be something wrong with my alternator controller, or charge monitor? I'm using my powermaster combi sl 1500 to measure voltage. They went bust last month but the details are still here: http://www.brightgreenenergy.co.uk/powerma...i_inverters.asp

[Sir Nibble]

I'm afraid that whilst the system itself is fairly simple, battery charging on a narrowboat with a great big domestic battery bank and little engine meant for a van or a harbour launch it gets a bit complex working out what's happening without being on the spot. Broadly speaking the voltage should rise to 14 ish within a comparatively short time (cannot be specific, too many variables) and then when the motor is shut down and batteries off charge the voltage will settle down to a value which if no load is being drawn is reasonably indicative of the state of charge. Your voltage never seems to rise to regulated level suggesting that the load, ie the degree to which the batteries are discharged, is such that the alternator is unable to fully supply it. This could be because the alternator is not big enough, spinning too slowly, or something is broke. It would help if you could identify the alternator to start with either by reading info off the unit or posting a pic.

[deletedaccount]

I'm afraid that whilst the system itself is fairly simple, battery charging on a narrowboat with a great big domestic battery bank and little engine meant for a van or a harbour launch it gets a bit complex working out what's happening without being on the spot. Broadly speaking the voltage should rise to 14 ish within a comparatively short time (cannot be specific, too many variables) and then when the motor is shut down and batteries off charge the voltage will settle down to a value which if no load is being drawn is reasonably indicative of the state of charge. Your voltage never seems to rise to regulated level suggesting that the load, ie the degree to which the batteries are discharged, is such that the alternator is unable to fully supply it. This could be because the alternator is not big enough, spinning too slowly, or something is broke. It would help if you could identify the alternator to start with either by reading info off the unit or posting a pic.

 

Cheers nibble. I'll get a pic/read on it tonight. It's a 110a unit if the manual that came with the boat is accurate. Next time I move it I'll get someone to watch the meter to see if it goes above the 13.2 max I've seen at idle and hits 14+ when the engine is at high revs as well (which should tell me that the problem is the alternator spinning too slowly, right?).

Edited September 2, 2009 by deletedaccount

[Sir Nibble]

Next time I move it I'll get someone to watch the meter to see if it goes above the 13.2 max I've seen at idle and hits 14+ when the engine is at high revs as well (which should tell me that the problem is the alternator spinning too slowly, right?).

That would be pretty diagnostic of a speed problem yes, but you have to be a bit swift to be sure it is the extra revs giving the increase rather than the time on charge. The fact that you have to increase speed to get a voltage rise which remains when you return to idle suggests the same. Do you not have an alternator warning light fitted? If so, at what speed does it extinguish?

[WotEver]

Next time I move it I'll get someone to watch the meter to see if it goes above the 13.2 max I've seen at idle and hits 14+ when the engine is at high revs as well (which should tell me that the problem is the alternator spinning too slowly, right?).

 

Probably

[deletedaccount]

That would be pretty diagnostic of a speed problem yes, but you have to be a bit swift to be sure it is the extra revs giving the increase rather than the time on charge. The fact that you have to increase speed to get a voltage rise which remains when you return to idle suggests the same. Do you not have an alternator warning light fitted? If so, at what speed does it extinguish?

 

I've not seen a warning light. There's certainly not one on the engine panel.

 

The inverter/charger has a battery charge state with four bars. Yesterday it was at 1 bar, this morning it was at 4. Not sure how accurate that is when I'm only reading 12.2v though

[Gibbo]

1/ your batteries will not be fully charged unless you can get them up to 14.4-14.7v

 

Incorrect. 13.6 volts will fully recharge a battery. It will just take longer.

 

2/ dont fit an ammeter as the voltage drop upsets the voltage regulator in your alternator ..they were never intended to be used with an alternator

 

The voltage drop with a decent shunt ammeter is minimal. Usually around 50mV max. That will make almost no difference.

 

3/ if you want to know charge current use the type of ammeter which goes around the cable ..prferably a digital one

 

The most innaccurate type of ammeter known to man.

 

4/ the max charge you can get into a 100ah battery is about 25 A so if you have 600ah you need alternator capacity of 150 A

 

Depends upon the type of battery. Gel and AGM will accept substantially more than this. Even wet cells commonly take 30 to 35 amps per 100ahr on average throughout the charge cycle. You need to look up amp hour law charging. A 100 ahr wet cell at 25% SoC will easily take 80 amps or more.

 

5/ you may need to fit two alternators to get to this capacity ...the simple way to do it is fit a big switch to join the two B terminals [of the domestic and start alterantor??] and when you have run for 10 min to charge the strting battery throw the switch

 

6/ you need to have your alternator at 6000 rpm to get full output so chceck your engine revs and belt ratio...( with engine at max rpm the alternator should be geared for 12000 rpm)

 

Rubbish. Most alternators are producing 90% rated output by 3000 RPM. Many even achieve this at 2400 RPM

 

Gibbo

[WotEver]

The inverter/charger has a battery charge state with four bars. Yesterday it was at 1 bar, this morning it was at 4. Not sure how accurate that is when I'm only reading 12.2v though

 

Well, at 12.2v the battery is around 60-70% charged. Full charge (if you can ever get it up there, and only with a 'good' battery) would be 12.7v. That's why, as Gibbo pointed out, 13.6v will indeed fully charge a 12v battery (eventually).

 

Tony

[deletedaccount]

Well, at 12.2v the battery is around 60-70% charged. Full charge (if you can ever get it up there, and only with a 'good' battery) would be 12.7v. That's why, as Gibbo pointed out, 13.6v will indeed fully charge a 12v battery (eventually).

 

Tony

 

So with 13.2v going in (the highest I've got while idle) how high should I be aiming at charging without encountering to much in the way of diminishing returns - 80%? I've heard that keeping them between 50 and 80% is a reasonable approach. What v would that be aprox? 12.4/12.5?

[WotEver]

What v would that be aprox? 12.4/12.5?

 

Yep. 80% is approx 12.5v. Gibbo won't say so, so I'll recommend you splash out on a Smart Gauge. Think of it as a fuel gauge for your batteries (as someone recently said on these forums - maybe even this thread?)

 

T

[nb Innisfree]

So with 13.2v going in (the highest I've got while idle) how high should I be aiming at charging without encountering to much in the way of diminishing returns - 80%? I've heard that keeping them between 50 and 80% is a reasonable approach. What v would that be aprox? 12.4/12.5?

 

Think you'll find 50% is a bit low, with your batt capacity you could cycle between 60% and 80% but you must give them a full equalising charge on a regular basis or your voltage will keep dropping.

[Sir Nibble]

Woa! 13.6V will charge your battery eventually but don't go thinking that means everything is all right. The extra volt will make a huge difference. The key word is "eventually". You could raise a family and grow old waiting.

[deletedaccount]

Points taken!

 

I'll try and maintain 12.1 to 12.5 (60-80%)

 

And a weekly blast back up to 12.7 at some higher input than 13.2v, preferably 14.4v. Somehow. (by regular you mean weekly, right, or can I get away with every two weeks? - I'm planning on doing a days cruising every one - two weeks anyway)

[Gibbo]

I'll try and maintain 12.1 to 12.5 (60-80%)

 

12.3 to 12.5 (60-80%)

 

And a weekly blast back up to 12.7 at some higher input than 13.2v, preferably 14.4v. Somehow. (by regular you mean weekly, right, or can I get away with every two weeks? - I'm planning on doing a days cruising every one - two weeks anyway)

 

As often as possible really.

 

Every day is good but often not very practical.

 

Every fortnight is better than never, but every week is better than every fortnight. And every 3 days is better than every week. You get the idea?

 

Gibbo