Question re possible Alternator Charging rates?

[xeitosaphil]

Further to my previous posts, adding batteries to existing banks

http://www.ybw.com/forums/showthread.php?408523-Engine-Start-Battery-Size

I have a couple of questions now I’m in the process of installing the new engine battery and circuits.

With a Domestic 310Ah battery bank and a 90A alternator, controlled by an Adverc. if the Domestic battery bank is discharged to 50% capacity, can anybody tell me what the estimated max alternator output in amps is likely to be to recharge the battery bank? I'm trying to rate a fuse for the alternator charging circuit, and wondered if I should also up rate the fuse and the cable due to maybe increased amperage needed from the alternator with regard to charging the bigger battery bank.

The present alternator cable is 10mm square Tri rated and is rated at 75A, current fuse is rated at 50A. No problems to date with my set up as it is on a 220Ah bank.

Also would this alternator charge however high it is likely to be, damage the new engine battery which will only be a Red Flash 750 AGM only 26Ah. The alternator will effectively charge the engine battery first, then the discharged 310Ah battery bank via a VSR link.
I did wonder, if it would be better to connect the alternator charging circuit to the Domestic bank as there is always likely to be more discharge in the dom/bank than the engine start, or should I keep it as it is now?
There is also a 100w solar panel in the domestic circuit at present which also charges both banks via the Bi Directional VSR.


Thanks again for any input,

Philip

 

[pvb]

It depends on the batteries, but I think you'd normally be unlikely to see much more than 60-70A charge rate. AGM batteries however will accept higher charge rates.

Your 10 sq mm cable is undersized; you'd be better using 25 sq mm. You obviously need a bigger fuse than 50A; if you use 25 sq mm cable you might use a 150A fuse.

With an Adverc regulator, you run a risk of applying too high a voltage to the Red Flash AGM battery. You may wish to risk that, or perhaps try to reduce the charge voltage to the Red Flash by putting a diode in the charge lead.

I'd wire the alternator output direct to the domestic batteries, then let the VSR connect the start battery once the house batteries have had some charge.

 

[VicS]

Further to my previous posts, adding batteries to existing banks

http://www.ybw.com/forums/showthread.php?408523-Engine-Start-Battery-Size

I have a couple of questions now I’m in the process of installing the new engine battery and circuits.

With a Domestic 310Ah battery bank and a 90A alternator, controlled by an Adverc. if the Domestic battery bank is discharged to 50% capacity, can anybody tell me what the estimated max alternator output in amps is likely to be to recharge the battery bank? I'm trying to rate a fuse for the alternator charging circuit, and wondered if I should also up rate the fuse and the cable due to maybe increased amperage needed from the alternator with regard to charging the bigger battery bank.

The present alternator cable is 10mm square Tri rated and is rated at 75A, current fuse is rated at 50A. No problems to date with my set up as it is on a 220Ah bank.

Also would this alternator charge however high it is likely to be, damage the new engine battery which will only be a Red Flash 750 AGM only 26Ah. The alternator will effectively charge the engine battery first, then the discharged 310Ah battery bank via a VSR link.
I did wonder, if it would be better to connect the alternator charging circuit to the Domestic bank as there is always likely to be more discharge in the dom/bank than the engine start, or should I keep it as it is now?
There is also a 100w solar panel in the domestic circuit at present which also charges both banks via the Bi Directional VSR.


Thanks again for any input,

Philip

I would rate the cable so that volts drop was not an issue and so that it can safely handle something comfortably in excess of the 90amps max output from the alternator. If the cable length is short then safe current carrying capacity is the main concern but if longer volts drop becomes more important.

I'd rate the fuse well in excess of 90amps because if the fuse blows the voltage surge will fry alternator diodes. The safe rating of the cable should be grater than the fuse rating.
The fuse should be at the battery end ... to protect the cable from potentially 100s of amps that the battery could supply in the event of a short.

You may have trouble with the VSR if the small engine start battery has priority charging and the domestic bank is low.

The engine start battery will quickly recharge Ok but when the VSR closes the domestic bank will drag the volts down and cause the VSR to open again, only to close again almost immediately and repeat the cycle.
Maybe there is some cunning system to stop this happening.

You could adopt the system preferred in the US, which is to use the big bank for all purposes but have a reserve battery charged via a VSR. I think you will find it described in Calder's book

 

[BabaYaga]

Also would this alternator charge however high it is likely to be, damage the new engine battery which will only be a Red Flash 750 AGM only 26Ah. The alternator will effectively charge the engine battery first, then the discharged 310Ah battery bank via a VSR link.
I did wonder, if it would be better to connect the alternator charging circuit to the Domestic bank as there is always likely to be more discharge in the dom/bank than the engine start, or should I keep it as it is now?
There is also a 100w solar panel in the domestic circuit at present which also charges both banks via the Bi Directional VSR.

The engine battery will only take the current it needs, normally very little, regardless of what the alternator is capable of putting out. What can be harmful, especially for a small AGM battery, is IMO if the voltage is too high for too long. But the Adverc should limit the voltage to nominally 14,4 V (unlike some other regulators, Sterling I think). Also note the Adverc instructions about where to connect the red sense lead, depending on how the charge splitting is set up.

Again, in normal circumstances, "charging the engine battery first" will be over in a second (if there is no delay built into the VSR).

I think the suggestion to connect the alternator primarily to the domestic bank is a good one. Also consider using a simple relay controlled by alternator D+/61 to bring the engine battery on line instead of the VSR, in order to avoid the on/off cycling problems described by VicS. Or choose a VSR that is designed not to "chatter".

 

[pvb]

The engine battery will only take the current it needs, normally very little, regardless of what the alternator is capable of putting out. What can be harmful, especially for a small AGM battery, is IMO if the voltage is too high for too long. But the Adverc should limit the voltage to nominally 14,4 V (unlike some other regulators, Sterling I think). Also note the Adverc instructions about where to connect the red sense lead, depending on how the charge splitting is set up.

Again, in normal circumstances, "charging the engine battery first" will be over in a second (if there is no delay built into the VSR).

I think the suggestion to connect the alternator primarily to the domestic bank is a good one. Also consider using a simple relay controlled by alternator D+/61 to bring the engine battery on line instead of the VSR, in order to avoid the on/off cycling problems described by VicS. Or choose a VSR that is designed not to "chatter".

The Adverc on my old boat would raise the charging voltage at the batteries to around 14.8v in colder weather.

If the alternator output goes directly to the domestic bank, there's little chance of VSR "chatter".

 

[BabaYaga]

The Adverc on my old boat would raise the charging voltage at the batteries to around 14.8v in colder weather.

If the alternator output goes directly to the domestic bank, there's little chance of VSR "chatter".

Yes, that is the case in mine too, but from what I understand compensating for low temperatures should not harm the battery. Or do you mean that the Adverc over-compensates?

I agree. But "chatter" is not the only issue with VSR's IMO.

 

[xeitosaphil]

Having visited the boat again today, I have an admission to make - the Alternator cable is 16mm2 not 10mm2 as state before.

This 16mm2 cable is Tri rated @ a Constant 100Amps, so I wondered if it would be ok to use now. Alternator to battery length is approx 3 mtrs ( or would it be better to use 25mm2 as pvb suggested ) Seems a shame to rip out the existing as it was only put in last year with all the new starting circuits and fuses. It is already installed and protected by a slow blow Midi Fuse of 75A but could be uprated to say 80A, spec here

http://www.littelfuse.com/~/media/f..._application note slow vs fast auto fuses.pdf

Set in the original carrier maybe?

As my existing 220A Domestic bank is usually never discharged lower than say 65%, I wonder if my original question re 50% discharge is really relevant especially with the extra AH of the new 310A bank. I do wonder if the alternator may only be running at maybe 75% of its capable load Max say 70A or less.
I know the fuse I was looking at is only 80A but my thinking is looking at the spec tables, that at its rated load of 80A it will run for 100 hrs, at 200% of its rated load it will run for 5 secs, and at 300% will run for just 0.5 secs. This suggests to me that I may be able to get away with even my existing fuse maybe? Or have I got the wrong end of the stick completely?

At present the alternator is fitted to the old engine battery, which will now be included into the domestic bank so I have taken on board what others have said about the Chatter aspect, and possible overcharge voltage with the Adverc, and hope they both work ok on the domestic bank without issue.

Have I got it all completely wrong? after all it is " Eletrickery "

I have made a diagram of my new proposed starter battery wiring for the new engine battery in the hope someone might check it over, and point out any problems I may have incorporated? Batteries should be in parallel and the shunt should monitor charge and discharge of domestic batteries.



View attachment 46777






I may also have to add a small Solar panel to the engine start circuit because if the domestic battery emergency engine start circuit fuse was to blow, there would be no way of charging the engine battery, unless I could put a On-Off-On DP change over switch into the existing solar panel circuit so I could divert the panel charging output to the engine battery.

As always thanks for any input

Philip

 

[pvb]

Having visited the boat again today, I have an admission to make - the Alternator cable is 16mm2 not 10mm2 as state before.

This 16mm2 cable is Tri rated @ a Constant 100Amps, so I wondered if it would be ok to use now. Alternator to battery length is approx 3 mtrs ( or would it be better to use 25mm2 as pvb suggested ) Seems a shame to rip out the existing as it was only put in last year with all the new starting circuits and fuses. It is already installed and protected by a slow blow Midi Fuse of 75A but could be uprated to say 80A

The 16 sq mm cable will do, but at 75A it will still have a voltage drop of 0.3v on the positive cable alone, plus a drop on the negative cable. The Adverc will compensate for this, of course, but a bigger cable would be a better installation.

As my existing 220A Domestic bank is usually never discharged lower than say 65%, I wonder if my original question re 50% discharge is really relevant especially with the extra AH of the new 310A bank. I do wonder if the alternator may only be running at maybe 75% of its capable load Max say 70A or less.
I know the fuse I was looking at is only 80A but my thinking is looking at the spec tables, that at its rated load of 80A it will run for 100 hrs, at 200% of its rated load it will run for 5 secs, and at 300% will run for just 0.5 secs. This suggests to me that I may be able to get away with even my existing fuse maybe? Or have I got the wrong end of the stick completely?

I don't think you'll often have anywhere near 80A charging rate, so an 80A fuse will do. Indeed your 75A fuse will probably be OK.

I have made a diagram of my new proposed starter battery wiring for the new engine battery in the hope someone might check it over, and point out any problems I may have incorporated? Batteries should be in parallel and the shunt should monitor charge and discharge of domestic batteries.

I may also have to add a small Solar panel to the engine start circuit because if the domestic battery emergency engine start circuit fuse was to blow, there would be no way of charging the engine battery, unless I could put a On-Off-On DP change over switch into the existing solar panel circuit so I could divert the panel charging output to the engine battery.

If the 250A fuse were to blow, surely you'd know about it and simply replace it? Putting another solar panel on seems totally unnecessary.

 

[BabaYaga]

After looking at the diagram I would only add two minor things:
1) It would be better if you could charge the house bank in a "balanced" way, that is pos. and neg. feeding from opposite directions.
2) I think I would connect the wire from the VSR to the engine switch at the other pole, so that the possibility to isolate the starter battery in an emergency remains. (As it is, the VSR will automatically parallel the battery banks, provided that the house bank is reasonably well charged).

 

[xeitosaphil]

After looking at the diagram I would only add two minor things:
1) It would be better if you could charge the house bank in a "balanced" way, that is pos. and neg. feeding from opposite directions.
2) I think I would connect the wire from the VSR to the engine switch at the other pole, so that the possibility to isolate the starter battery in an emergency remains. (As it is, the VSR will automatically parallel the battery banks, provided that the house bank is reasonably well charged).

Not exactly sure what you mean?

1) Do you mean take the engine ground cable from the " L " shaped set of House batteries instead of the single one his own?

2) If I was to do that, how would the VSR charge the Engine battery automatically?

If there was a problem with the engine battery, as it is at the moment I can still isolate the battery and the both banks are only paralleled when the house batteries are above 13.3v until they fall to 12.8v. If there was a dead short on the engine battery I would assume that the fuse would provide isolation anyway. Is there any other Scenario that would make it less advantageous than it is now?

My electrical knowledge is somewhat limited so always open to suggestions.

Philip

 

[xeitosaphil]

The 16 sq mm cable will do, but at 75A it will still have a voltage drop of 0.3v on the positive cable alone, plus a drop on the negative cable. The Adverc will compensate for this, of course, but a bigger cable would be a better installation.



I don't think you'll often have anywhere near 80A charging rate, so an 80A fuse will do. Indeed your 75A fuse will probably be OK.



If the 250A fuse were to blow, surely you'd know about it and simply replace it? Putting another solar panel on seems totally unnecessary.

16mm cable - I'll give the existing cable a try and see if it's ok in practice, I could always upgrade later but thanks for your suggestion.

Fuses - That's reassuring to know, glad I'm on the right track with my assumptions

Solar Panel - I did think that myself, as long as I have spares available

Thanks for your input pvb Much appreciated as usual

Philip

 

[vyv_cox]

My alternator is the standard Yanmar 55A one, feeding 3 x 110 Ah domestic batteries. First thing in the morning, fridge on all night and before the solar panels have had a chance to do anything, the battery voltage is never less than 12.4, more usually a little higher. On starting the engine the alternator delivers pretty much its full rated current, more than 50 amps. This doesn't continue for long and within about 10 minutes it is down to 40A. On that basis I see no reason why your alternator should not deliver its rated current.

 

[xeitosaphil]

My alternator is the standard Yanmar 55A one, feeding 3 x 110 Ah domestic batteries. First thing in the morning, fridge on all night and before the solar panels have had a chance to do anything, the battery voltage is never less than 12.4, more usually a little higher. On starting the engine the alternator delivers pretty much its full rated current, more than 50 amps. This doesn't continue for long and within about 10 minutes it is down to 40A. On that basis I see no reason why your alternator should not deliver its rated current.

Not sure why?

Could it be down to the size of your engine? start up taking many amps out of the battery, condition of actual batteries, Ambient Temperature only guessing don't know much about these things really.

All last year using F/Freezer 24/7 ( only 35/40Ltr mind you ) 2x110A House bank of batteries, 100w Solar Panel. never saw the alternator put in more than 20Amps at start up but engine only a Yanmar 2GM20.

I assume 12.4v on a 330Ah battery bank amounts to much more drain in amps than a 12.4v on a 220Ah bank? Say 70% of 330Ah = 30% drain nearly 100Ah. 70% of 220Ah= 30% drain only approx. 66Ah. yours are therefore approx. 1/3rd more drain in amps than mine. My 20amps + 1/3rd more = roughly 30amps ?

This might be rubbish but I'm sure others will be more knowledgeable and be along later to explain the reasons why maybe?

 

[vyv_cox]

Can only suggest a few differences that might account for it, although I would have thought the behaviour of ours was perfectly OK.

Engine is 3GM30F. It starts instantaneously, always, so no chance that the battery is being drained turning the engine over. Our fridge probably works a lot harder in Greece than yours in Devon. The batteries were new three years ago and have always behaved in a similar way, although I suspect that as they have aged they may draw a little less at start. Sealed batteries on the appropriate setting on the Sterling, i.e. lower voltage. Ambient temp about 30C or more. The previous open cell batteries on the higher charge setting behaved in a similar way, although being older they only took about 45 amps.

 

[BabaYaga]

1) Do you mean take the engine ground cable from the " L " shaped set of House batteries instead of the single one his own?

Yes, exactly! Balanced is perhaps not the right word. But with three batteries in parallel, the best way would be to connect the pos. lead to battery 1 and the neg. lead to battery 3. Or the other way around.

2) If I was to do that, how would the VSR charge the Engine battery automatically?

If there was a problem with the engine battery, as it is at the moment I can still isolate the battery and the both banks are only paralleled when the house batteries are above 13.3v until they fall to 12.8v. If there was a dead short on the engine battery I would assume that the fuse would provide isolation anyway. Is there any other Scenario that would make it less advantageous than it is now?

In normal operation, with the modification I suggested, the VSR will automatically charge the engine battery because the engine battery switch will be closed (otherwise you would not be able to start the engine from that battery).

If the engine battery is faulty, my proposal gives you the opportunity to isolate it regardless of which state of charge the house batteries are in. If the engine battery is only low you would likely want to recharge it as soon as possible. In that case you could just close the switch once the engine has fired up (from the house bank via the emergency switch). Or you could open the emergency switch and let the engine battery be charged via the VSR later, when the house bank has received some charge.

 

[xeitosaphil]

Yes, exactly! Balanced is perhaps not the right word. But with three batteries in parallel, the best way would be to connect the pos. lead to battery 1 and the neg. lead to battery 3. Or the other way around.



In normal operation, with the modification I suggested, the VSR will automatically charge the engine battery because the engine battery switch will be closed (otherwise you would not be able to start the engine from that battery).

If the engine battery is faulty, my proposal gives you the opportunity to isolate it regardless of which state of charge the house batteries are in. If the engine battery is only low you would likely want to recharge it as soon as possible. In that case you could just close the switch once the engine has fired up (from the house bank via the emergency switch). Or you could open the emergency switch and let the engine battery be charged via the VSR later, when the house bank has received some charge.

On proposal 1) yes I can see that would be better and will change it.

On proposal 2) with the VSR wire connected as you say, when the isolators are both turned off and I am away from the boat , the charge generated from the Solar panel which is fixed to the House set of batteries won't charge the engine battery via the VSR.

If left as is, and the engine battery is low, I would want to recharge it as soon as possible like you say, in which case I could just select the emergency / Both switch, isolate the engine battery so it doesn't pull the voltage of the house bank down ( as it will equalise naturally if the VSR is connected ), and let the engine battery be charged via the VSR when the house bank has started the engine and has reached reached a state of 13.3v. If the engine battery is lower than 12.8v the VSR will automatically dis-engage from the House battery bank anyway.

If the worst came to the worst and I needed to isolate the engine battery with the house battery voltage above 13.3v and joined to the engine battery, it is a simple task to just disconnect the VSR sensing wire from the Negative Block - 2 min job thereby disabling the VSR, and it will disconnect the engine battery straight away.


Not sure there is any benefit from your suggestion on this option, and down side is there will be no Solar charge to engine battery when I'm away from the boat.

Philip

 

[BabaYaga]

and down side is there will be no Solar charge to engine battery when I'm away from the boat.

I agree, and if this is important leave it as in the diagram.
Personally I would be reluctant to have a small AGM battery on charge for prolonged periods. If you do, check that the solar regulator has a float voltage level that is appropriate. You can always add water to a bank of wet cells, but not to a sealed one. Good luck with your installation.

 

[neil1967]

One of the advantages of red flash, optimax etc batteries is their very low self discharge rates. I have an optimax on the boat as an engine start battery, and unfortunately often have to leave the boat for months at a time and the engine (a Perkins 4108) starts no problem - I don't have mains at the berth and my small solar panel is used to keep my domestic bank topped up. I also fitted an optimax to a classic car, and it transformed it - given that it was not driven frequently, with a lead acid battery, it was often reluctant to start - with an optimax it had no problem turing the engine over at high speed, irrespective of when it was last used. Personally I would feed your solar direct to your domestic batteries.

Neil

 

[xeitosaphil]

One of the advantages of red flash, optimax etc batteries is their very low self discharge rates. I have an optimax on the boat as an engine start battery, and unfortunately often have to leave the boat for months at a time and the engine (a Perkins 4108) starts no problem - I don't have mains at the berth and my small solar panel is used to keep my domestic bank topped up. I also fitted an optimax to a classic car, and it transformed it - given that it was not driven frequently, with a lead acid battery, it was often reluctant to start - with an optimax it had no problem turing the engine over at high speed, irrespective of when it was last used. Personally I would feed your solar direct to your domestic batteries.

Neil

Hi Neil thanks for the input - the solar panel is indeed fitted direct to the Domestic bank, but any input that puts the voltage above 13,3v will activate the VSR thereby charging the engine battery.

I have checked the Morning Star Prostar 15 Solar Controller

Spec seen here http://www.morningstarcorp.com/wp-content/uploads/2014/02/PS2.IOM_.English.EN_.021.pdf


which says float charge is 13.7v but it also has loads of other safety features incorporated as well.

The Red Flash battery Charging Spec seen here - http://www.varleyredtop.com/pdf/vrt_charging_1.pdf

Having telephoned the Company they confirm thet Red Top & Red Flash to be the same battery /same Company / same Technology

In their Maintenance and Charging Sec it says normal float charge of - Float charge = 13.5 – 13.8V per battery at 25°C

They also say no problems with constant connection to Solar regulator as it has multiple regulation, so I think everything should be ok.

Philip