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Hi all,can anyone tell me if my current alternator (75 amp)would be capable of charging 4 leasure and a starter battery,many thanks.

 

I'm looking at upgrading for the new season next year and don't no weather to go with three or four 130 amp with a smart meter,at the moment I have two leasure and a starter,led acid,I don't want to add to them I want to replace all with new ones,

 

Edited by dreadnought
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1 minute ago, dreadnought said:

Hi all,can anyone tell me if my current alternator (75 amp)would be capable of charging 4 leasure and a starter battery,many thanks

 

The answer is yes, but how long it will take is open to question. That depends upon how deeply you have discharged them

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1 minute ago, dreadnought said:

Hi all,can anyone tell me if my current alternator (75 amp)would be capable of charging 4 leasure and a starter battery,many thanks

 

The simple answer is "no reason why not"..... a 75A alternator is quite powerful.

 

Assuming you have something like 4 x 110Ah Lead Acid or AGM, and a similar starter battery, and a way of sharing the current, your starter will be topped up within minutes of starting the engine, and the leisures will receive a decreasing current over time until it falls to such a level that they can be considered full - this usually takes several hours.

 

What are your batteries, Make/model/Ah?

 

Have you got a battery monitor, NASA BM1? Victron BMV***? Smartgauge :( ? or something similar?

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I would have thought whether a 75A alternator was big enough depended on how much energy was being drawn from the battery bank each day.

 

You need to do a power audit and post it up here to get any meaningful advice. I'm pretty sure Tony explains how to do one on his website, tb-training.co.uk (from memory, might be wrong).

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It depends on your lifestyle (boating style?).

If you go for nice long cruises every day then it will probably be ok.

If you run the engine just for battery charging then a bit bigger would be really good.

Despite what many say a good alternator controller (Adverc etc) can often really help too.

Getting the voltage right (as high as you can for the battery type) is also important.

If you are driving off a single 12mm V belt then 100amps is about the limit.

 

 

 

 

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A vehicle alternator is just that - it's for charging a car etc and its normal load duty.

For boaters usning what to day is regarded as 'essential' devices you really need a larger alternator PLUS a controller such as an Adverc.

Been there etc.

 

I start my boating day with the Adverc turned off and wait 1/2 - 1 hour for the engine to warm up and  start charging. Then I swich the Adverc on for the rest of the cruise - otherwise at lower engine revs the alternator stalls and the drive belt smokes....

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1 hour ago, OldGoat said:

A vehicle alternator is just that - it's for charging a car etc and its normal load duty.

For boaters usning what to day is regarded as 'essential' devices you really need a larger alternator PLUS a controller such as an Adverc.

Been there etc.

 

I start my boating day with the Adverc turned off and wait 1/2 - 1 hour for the engine to warm up and  start charging. Then I swich the Adverc on for the rest of the cruise - otherwise at lower engine revs the alternator stalls and the drive belt smokes....

The alternator replaced the dynamo partly because car electrical loads wre getting too much for dynamos.  The electrical load has gone on increasing and gone beyond the capability of the early Bosch and Lucas alternator offerings. A modern car alternator is much better cooled and driven than the A127 and its ilk  so capable of operating at high outputs for long spells. Unfortunately they are now designed to be controlled by the ECU, as a spare time job.  The ECU controls the charge,  makes sure the alternator and batteries don't get too hot, belts maximum power into the battery when  on overrun, etc etc.  All far too difficult for most boaters to replicate,  excepting Nick Norman who has devised and implemented a widget that does do the ECU's job for his lithiums.. 

 

The normal  answer is  to buy a biggish  older style of alternator and not use it's full capacity all the time.  Fortunately Lead Acid batteries automatically the reduce the output of the alternator as they charge.

 

 

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19 hours ago, dreadnought said:

Hi all,can anyone tell me if my current alternator (75 amp)would be capable of charging 4 leasure and a starter battery,many thanks.

 

I'm looking at upgrading for the new season next year and don't no weather to go with three or four 130 amp with a smart meter,at the moment I have two leasure and a starter,led acid,I don't want to add to them I want to replace all with new ones,

 

I have 4 x 130 agms and a 110 start. My 70a alternator copes perfectly via an Adverc. I did have two 70a alternators but when the mounting for one failed I hardly noticed the difference so didn't bother to replace.

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I have an older Beta 35 with a 40 Amp alternator dedicated to a single 110 AH Start Battery and a 70 Amp alternator for domestic bank via an Adverc system and also split charge unit to charge the bowhruster battery.

My domestic bank is 8 x 110 AH Sealed Lead Acid and Bow Thruster is 110 AH SLA.

I have Smart Battery Monitor with shunt and can see exactly what is going to or from the Domestic Bank at any time.

Overnight my batteries usually drop to between 90 and 95% SOC as measured by the monitor that was calibrated at 100% when I installed it.

When starting the engine I can see that even on tickover the alternator is pushing around 45 amps to the batteries and over about 4 to 5 hours this drops steadily to just under 2 amps float as the bank becomes fully charged showing a steady 14.2 v 

So my old 70 Amp alternator copes with 990 AH of batteries with no problem at all.

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3 hours ago, MarkH2159 said:

So my old 70 Amp alternator copes with 990 AH of batteries with no problem at all.

 

As mentioned earlier the size of your battery bank has little bearing on what alternator you need to keep it charged.

 

What counts is how many AH per day you consume, as the alternator has to be capable of replacing it. 

 

 

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You need to calculate your energy used, running hours available to replace it and understand how to fully charge your batteries to an end current of 1%  to 2% maximum of their rated capacity.

Smart battery gauges will tell lies, your batteries will no longer be capable of retaining 100% of their original capacity. They need resetting periodically.

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2 minutes ago, Tracy D'arth said:

You need to calculate your energy used, running hours available to replace it and understand how to fully charge your batteries to an end current of 1%  to 2% maximum of their rated capacity.

Smart battery gauges will tell lies, your batteries will no longer be capable of retaining 100% of their original capacity. They need resetting periodically.

 

And unless he has altered it, I suspect @MarkH2159's monitor may be re-synching at 4% tail current, so that will make things even worse re true SOC.

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3 minutes ago, Tony Brooks said:

 

And unless he has altered it, I suspect @MarkH2159's monitor may be re-synching at 4% tail current, so that will make things even worse re true SOC.

True. Are they made to wreck folks' batteries unless the user knows that they need altering on installation and in use as well?

I manage without any of this sophistication, just a car voltmeter, Sterling controller and a clamp ammeter. But then I am a dinosaur. But my batteries last very well.

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3 minutes ago, Tracy D'arth said:

I manage without any of this sophistication, just a car voltmeter, Sterling controller and a clamp ammeter.

 

Sterling controller? 

 

None of that sophistry on my boat.....*

 

 

* Apart from one of them Smart Gauges, but it doesn't actually do anything to affect charging. 

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1 minute ago, Alan de Enfield said:

 

Are the other 2 not wired in now ?

 

Are we still working on "the best of three ?"

 

Same comment applies to all my boats. They all have Smartgauges re-calibrated as necessary to make them actually work. But as I said, SGs do nothing to affect or control charging. 

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32 minutes ago, Tracy D'arth said:

True. Are they made to wreck folks' batteries unless the user knows that they need altering on installation and in use as well?

I manage without any of this sophistication, just a car voltmeter, Sterling controller and a clamp ammeter. But then I am a dinosaur. But my batteries last very well.

 

Ditto  except my ammeter was permanently wired shunted type and no controller since I fitted a 14.5V alternator. It's the fully recharging that gives good battery life.

 

I think they are largely readout's for readout’s sake, a bit like boy racer vacuum gauges etc. All that they need is volts, amps and arguably Ah out so battery capacity could be assessed now and again.

Edited by Tony Brooks
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My replacement alternator pushes out 14.5V and the Adverc is disconnected. I shall remove it completely when I have time. I don't seem to struggle to charge the batteries but three new ones every five years isn't the end of the world.

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5 hours ago, Tony Brooks said:

 

And unless he has altered it, I suspect @MarkH2159's monitor may be re-synching at 4% tail current, so that will make things even worse re true SOC.

re true SOC

Following the instructions I set the monitor when i first connected it to my now 6+ year old bank of batteries.

Having ensured they were fully charged, ie reading 14+ volts and taking just under 2 amps to maintain them at that voltage for at least 2 hours, I set the total AH capacity and then zeroed the meter to read 100% SOC.

With engine/charging stopped for several hours my batteries hold a resting voltage of 12.8 and will do so for considerable time.

With use, lights, fridge, 4G router, watching TV overnight the voltage will drop to around 12.6 and in the morning the monitor will show around 93 to 95% SOC.

I believe this to be as accurate as it gets and definitely much better than the SOC as indicated on my MPPT controller which comes up with some strange percentages,

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6 hours ago, MarkH2159 said:

re true SOC

Following the instructions I set the monitor when i first connected it to my now 6+ year old bank of batteries.

Having ensured they were fully charged, ie reading 14+ volts and taking just under 2 amps to maintain them at that voltage for at least 2 hours, I set the total AH capacity and then zeroed the meter to read 100% SOC.

With engine/charging stopped for several hours my batteries hold a resting voltage of 12.8 and will do so for considerable time.

With use, lights, fridge, 4G router, watching TV overnight the voltage will drop to around 12.6 and in the morning the monitor will show around 93 to 95% SOC.

I believe this to be as accurate as it gets and definitely much better than the SOC as indicated on my MPPT controller which comes up with some strange percentages,

 

 

 

All I can say is that 12.6 rested volts is not generally accepted as 90% charged, probably more like about 80 to 85%. As you seem to be using tail current at more than 14 volts you probably are more or less (a bit less in your case) fully charging the batteries regularly, so that is good but unless you regularly infer the state of charge and then use the Ah out reading in the morning to ass the present capacity of your batteries the meter will be assuming that you have  a far larger bank capacity than you actually have because of sulphation. That probably explains the difference between the shown SOC and the SOC inferred from  rested voltage. However, that type of  meter typically, straight from the box use a much higher tail current than you do to assume 100% charged are recalibrate themselves so really need re-setting on initial installation.

 

I fully agree that a state of charge shown on a solar controller will be a fiction unless they are using Smartguage technology, which I doubt.

 

Anyway, size years and still working to an acceptable level means you are doing a lot right battery wise, but please treat the SOC figure on your    gauge with scepticism, expect it to overstate the SOC. The longer it has gone since the last full charge and recalibration, the more any discrepancy is likely to be.

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59 minutes ago, Tony Brooks said:

 

 

 

All I can say is that 12.6 rested volts is not generally accepted as 90% charged, probably more like about 80 to 85%. As you seem to be using tail current at more than 14 volts you probably are more or less (a bit less in your case) fully charging the batteries regularly, so that is good but unless you regularly infer the state of charge and then use the Ah out reading in the morning to ass the present capacity of your batteries the meter will be assuming that you have  a far larger bank capacity than you actually have because of sulphation. That probably explains the difference between the shown SOC and the SOC inferred from  rested voltage. However, that type of  meter typically, straight from the box use a much higher tail current than you do to assume 100% charged are recalibrate themselves so really need re-setting on initial installation.

 

I fully agree that a state of charge shown on a solar controller will be a fiction unless they are using Smartguage technology, which I doubt.

 

Anyway, size years and still working to an acceptable level means you are doing a lot right battery wise, but please treat the SOC figure on your    gauge with scepticism, expect it to overstate the SOC. The longer it has gone since the last full charge and recalibration, the more any discrepancy is likely to be.

Rested voltage is 12.8 not 12.6 and they take several hours to come down from 14+ fully charged to sit at 12.8 which they will do for a very long time if relatively unused.

Although my bank is labelled as 880 AH I put 800 into the meter settings to allow a bit for age.

I also set and calibrated the meter on installation about 3 weeks ago when i replaced my old less accurate unit.

This morning the voltage is 12.65 and the meter reads 90.6% SOC which to my reckoning is pretty accurate.

 

I have 540 watts of solar which generally covers my daily consumption and easily keeps the batteries between 95 and 98% full.

I also note that if they are at around 90-93% it takes several hours of alternator charging to get them to 100%

The rate of charge might initially be 40+ amps but it tails off more or less in a linear fashion, but with the last 1 or 2 % taking about 2 hours or more to achieve.

All of this tells me that my batteries are in a relatively good state and as you say, i must be doing something right for them to be approaching 7 years old with no real problems.

Edited by MarkH2159
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17 minutes ago, MarkH2159 said:

Rested voltage is 12.8 not 12.6 and they take several hours to come down from 14+ fully charged to sit at 12.8 which they will do for a very long time if relatively unused.

Although my bank is labelled as 880 AH I put 800 into the meter settings to allow a bit for age.

I also set and calibrated the meter on installation about 3 weeks ago when i replaced my old less accurate unit.

This morning the voltage is 12.65 and the meter reads 90.6% SOC which to my reckoning is pretty accurate.

 

I have 540 watts of solar which generally covers my daily consumption and easily keeps the batteries between 95 and 98% full.

I also note that if they are at around 90-93% it takes several hours of alternator charging to get them to 100%

The rate of charge might initially be 40+ amps but it tails off more or less in a linear fashion, but with the last 1 or 2 % taking about 2 hours or more to achieve.

All of this tells me that my batteries are in a relatively good state and as you say, i must be doing something right for them to be approaching 7 years old with no real problems.

 

Rested voltage can be any voltage between zero and about 12.7 to 12.8 volts. Rested voltage means the battery voltage with no current being drawn and after any surface charge has been dissipated so where you say "voltage will drop to around 12.6 and in the morning the monitor will show around 93 to 95% SOC " then 12.6V is the rested voltage of the bank as long as you are not drawing any current. So you seem to take 12.6v to infer a 90% SOC. That is not the typical inference, as I said.

 

The also few percent of charge taking a very long time is normal and this is what leads many inexperienced boaters to stop charging too soon for optimum battery life.

 

As a matter of interest, you may well find that the solar (and any smart charger) will go into float long before the batteries are fully charged so, for the benefit of others, a charge source in float should not be taken as indicating a 100% SOC.

 

 

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  • 2 weeks later...
On 14/08/2021 at 19:12, dreadnought said:

Hi all,can anyone tell me if my current alternator (75 amp)would be capable of charging 4 leasure and a starter battery,many thanks.

 

I'm looking at upgrading for the new season next year and don't no weather to go with three or four 130 amp with a smart meter,at the moment I have two leasure and a starter,led acid,I don't want to add to them I want to replace all with new ones,

 

It is not really the number of leisure batteries you have assuming that 4 are the domestic set, it is the Amp hours they total that will determine how long they take to charge. The 4 batteries are linked together in effect making one large 12v volt battery normally or possibly X2 24v batteries.

 

In my own setup I have 3 leisure batteries of 130 ah each so a total of 390 (or rather half of that as I do not discharge below 50%) and is charged by a single 70amp alternator plus a starter battery.  The start battery is of no real significance and will take little time to recharge from starting the engine. My setup takes around 4-5 hours cruising to recharge the batteries from overnight use.  We do not have any high electric consumers on the boat ie no microwave etc.

 

What you suggest will recharge the batteries OK but it depends on how much you drain from the batteries overnight or rather how much you need to put back into them to get to100% charge and how long that will take that matters and only you know that.

 

If you want to go for 130 AH domestic/leisure  batteries I can recommend the Crown 31DC130

 

31DC130 Crown Battery 12V 130Ah - Crown Batteries (tayna.co.uk)

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On 15/08/2021 at 21:43, Cheshire cat said:

My replacement alternator pushes out 14.5V and the Adverc is disconnected. I shall remove it completely when I have time. I don't seem to struggle to charge the batteries but three new ones every five years isn't the end of the world.

After consulting Adverc and receiving advice from someone on this on this forum I upped the output via my Adverc to 14.8 v. (AGMs fitted) On very rare occasions the overvolt light comes on but only for moments on startup.

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