alternator upgrade

[dreadnought]

hi all,i`m looking to upgrade my alternator fromm the 55amp one fitted at the moment to something a bit more powerfull above 70amp,its going on my bmc 1800,many thanks

 

[Tracy D'arth]

Just now, dreadnought said:

hi all,i`m looking to upgrade my alternator fromm the 55amp one fitted at the moment to something a bit more powerfull above 70amp,its going on my bmc 1800,many thanks

 

You cannot drive anything bigger than 90 to 100 Ampere with the single belt.

[Tony Brooks]

Don't go much above 70 amps, once you get to about 90 amps you may well run into belt problems. You can get 70 amp A127s and try to get one with a 14.5 to 14.6 volt regulator.

[Steve56]

Don't go too big otherwise you will have to change belts. I wouldnt want anything above about 80 amps running on a v belt.

[BEngo]

Changing the crankshaft pulley on  BMC is fraught with difficulty because it is also a torsional vibration damper which stops the crank fracturing.

 

Why do you want more Amps?  An extra 15A or so for about 30 minutes  will not noticeably speed up battery charging unless you have a very much better regulator than the built in one or even the Sterling/Adverc products.

 

N

[dmr]

You can just (and I do mean just) do 100amps on a single belt as long as the alternator pulley is not too small (which it probably is). A good notched belt is advised and check the tension at least every few months. It works for me but we have a big (12 inch) pulley on the engine so the alternator pulley can be a bit bigger than most. 70 to 80amp is probably a safer option. An Adverc makes a huge difference to my battery charging, I could not do without it.

 

.............Dave

[Tracy D'arth]

Consider a Sterling alternator controller, I have fitted lots over the last 25 years and they do the job. Even the early ones work, the latest digital one is in my opinion superior to all the alternatives.

Ensure you have good ventilation for the alternator, it will get hotter than it ever has. It is not unusual for them to smoke a bit getting all the oily junk out the first time they start working properly.

[nicknorman]

36 minutes ago, BEngo said:

An extra 15A or so for about 30 minutes  will not noticeably speed up battery charging unless you have a very much better regulator than the built in one or even the Sterling/Adverc products.

 

N

As I have confirmed with my digital regulator, due to the soft regulation curve of a normal alternator the current at mid-charge will be higher for a larger alternator, roughly in proportion to the additional size of the alternator. So it is not just about the period when the alternator is in “bulk” (producing its max output), it is also about the higher charge current for a given battery voltage from a larger alternator during most of the charging process.

 

The myth that you and many others repeat, really needs busting!

Edited August 25, 2020 by nicknorman

[Tracy D'arth]

3 minutes ago, nicknorman said:

As I have confirmed with my digital regulator, due to the soft regulation curve of a normal alternator the current at mid-charge will be higher for a larger alternator, roughly in proportion to the additional size of the alternator. So it is not just about the period when the alternator is in “bulk” (producing its max output), it is also about the higher charge current for a given battery voltage from a larger alternator during most of the charging process.

 

The myth that you and many others repeat, really needs busting!

There is a truth in that claim, I think it is probably due to the increased current capacity heating the alternator less when in the intermediate stages of charging.

I have noticed that on engines that are very enclosed and run hot, the charging current usefully increases if the ventilation is greatly increased allowing the alternator to get cool air through its electronics.

[dmr]

5 minutes ago, nicknorman said:

As I have confirmed with my digital regulator, due to the soft regulation curve of a normal alternator the current at mid-charge will be higher for a larger alternator, roughly in proportion to the additional size of the alternator. So it is not just about the period when the alternator is in “bulk” (producing its max output), it is also about the higher charge current for a given battery voltage from a larger alternator during most of the charging process.

 

The myth that you and many others repeat, really needs busting!

I have been saying this for years but obviously not loudly and clearly enough. Disconnecting the Adverc whilst in bulk mode and watching the current fall was what convinced me. The problem is that the "alternator controllers are not required" myth was likely started by Gibbo, ex of this forum, and its very hard to disagree with him on matters electrical. ?

 

.............Dave

[nicknorman]

8 minutes ago, Tracy D'arth said:

There is a truth in that claim, I think it is probably due to the increased current capacity heating the alternator less when in the intermediate stages of charging.

I have noticed that on engines that are very enclosed and run hot, the charging current usefully increases if the ventilation is greatly increased allowing the alternator to get cool air through its electronics.

It’s an inherent “feature” of alternators, in part due to the changing resistance of the rotor windings. I notice with my regulator, which measure field current, that when cold the resistance gives about 4.2A at 100% duty cycle, whereas when it gets hot is is more like 3.7A. Less current = less magnetic field = less output.

 

Also regulators tend to have an intentional temperature coefficient to reduce voltage at high temperature as a means of self-preservation.

 

However that is not the main reason for the improved charging times with a larger alternator, that is down to the regulation curve as previously mentioned.

Edited August 25, 2020 by nicknorman

[nicknorman]

6 minutes ago, dmr said:

I have been saying this for years but obviously not loudly and clearly enough. Disconnecting the Adverc whilst in bulk mode and watching the current fall was what convinced me. The problem is that the "alternator controllers are not required" myth was likely started by Gibbo, ex of this forum, and its very hard to disagree with him on matters electrical. ?

 

.............Dave

It’s also been said that if you force too much current into a battery, it just gets lost to gassing. I’m sure there is a small amount of truth in that but it is not a major issue. Our Mastershunt calculates charge efficiency on every cycle and with the old regulator it was 93%. After a month with the new regulator it is 92% which is probably within the error of the calculation and even if not, is a pretty inconsequential reduction.

[dmr]

15 minutes ago, nicknorman said:

It’s also been said that if you force too much current into a battery, it just gets lost to gassing. I’m sure there is a small amount of truth in that but it is not a major issue. Our Mastershunt calculates charge efficiency on every cycle and with the old regulator it was 93%. After a month with the new regulator it is 92% which is probably within the error of the calculation and even if not, is a pretty inconsequential reduction.

A bit of equalisation increases the charge stored in the batteries so even if there is gassing there must still be useful charge going in. I also suspect that the equalisation increase in charge is sometimes even more than the extra amp-hours put in and I have seen reference to this on the www, but it makes no sense to me so I will ignore that for now.

I also suspect that the Adverc voltage cycling does have some advantages though possibly not for the reasons that Adverc designed it for. This cycling probably makes the Adverc a better option than the Sterling (at least for liveaboards) as the cycling is preferable to the Sterling approach of a constant hard charge and then switching into float. The Adverc could do even better if they would update the very old design and give it a bit of processing power.

 

 

...............Dave

[Sir Nibble]

Meanwhile.

The 55A alternator on that engine is very likely to be an A127. Since a 70A A127 is readily available and inexpensive and a straight swap it looks like a no brainer to me.

[nicknorman]

1 hour ago, dmr said:

A bit of equalisation increases the charge stored in the batteries so even if there is gassing there must still be useful charge going in. I also suspect that the equalisation increase in charge is sometimes even more than the extra amp-hours put in and I have seen reference to this on the www, but it makes no sense to me so I will ignore that for now.

I also suspect that the Adverc voltage cycling does have some advantages though possibly not for the reasons that Adverc designed it for. This cycling probably makes the Adverc a better option than the Sterling (at least for liveaboards) as the cycling is preferable to the Sterling approach of a constant hard charge and then switching into float. The Adverc could do even better if they would update the very old design and give it a bit of processing power.

 

...............Dave

My experience is that a bit of equalisation massively increases capacity out of all relation to the Ah put in. Not sure why though. However equalisation only adds charge if there is a degree of sulphation present.

[nicknorman]

By way of making the point, today we are tied up all day for obvious reasons. By late afternoon batteries (450Ah) down to 60% so need to run the engine for a bit. It has a 175A alternator. I added 20% SoC and then took this video, you can see that the SoC is around 80% and the target and actual voltages are around 14.6v. The alternator is still chucking in around 130A. With the standard regulator this would be more like 70A. And with a 70A alternator, more like 30A.

 

 

[Tracy D'arth]

Good'o.  Annoying the neighbours?

[nicknorman]

What neighbours?

 

well ok there is a Dutch barge thing behind, but it is so windy I doubt anyone can hear our already very quiet engine. And I’ve added 100Ah in about 50 mins, engine now stopped. That will do until we depart tomorrow.

[WotEver]

6 minutes ago, nicknorman said:

I added 20% SoC and then took this video...

Which clearly demonstrates that filing isn’t your forte. 

[dmr]

7 minutes ago, nicknorman said:

By way of making the point, today we are tied up all day for obvious reasons. By late afternoon batteries (450Ah) down to 60% so need to run the engine for a bit. It has a 175A alternator. I added 20% SoC and then took this video, you can see that the SoC is around 80% and the target and actual voltages are around 14.6v. The alternator is still chucking in around 130A. With the standard regulator this would be more like 70A. And with a 70A alternator, more like 30A.

 

 

Would you like a lesson in making neat square holes ?

[nicknorman]

3 minutes ago, WotEver said:

Which clearly demonstrates that filing isn’t your forte. 

My failure to cut out a square hole adequately was covered in a different thread (rush job etc etc excuses ...). I am still trying to get hold of a square drill, but they seem difficult to come by. And my other excuse is that the display is quite small, just over an inch, so the defective workmanship is magnified!

 

Yes OK I will have to cough up another £6 for a box from RS and do a better job of cutting the hole out. Or I could just get some black paper to cover up my sins!

Edited August 25, 2020 by nicknorman

[WotEver]

Sticky back plastic...

[nicknorman]

Just now, WotEver said:

Sticky back plastic...

Good idea! Where is Valerie Singleton when you need her?

[dmr]

I assume that's the same little display that the Arduino people use? I am surprised that nobody has produced a neat bezel for it, but last time I looked I could find nothing.

 

.........Dave

[nicknorman]

Just now, dmr said:

I assume that's the same little display that the Arduino people use? I am surprised that nobody has produced a neat bezel for it, but last time I looked I could find nothing.

 

.........Dave

Yes that’s the one, 0.95” OLED with I2C interface. About £4, fantastic value! I am tempted to look at 3D printing, but that is a project for the winter.