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Fitting second alternator to Isuzu 4LB33 engine


JoshS

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Hi! We've just taken ownership of our first narrowboat, so are currently experiencing a very steep learning curve regarding the electrics on board. The boat currently has (what I believe is) a 70Ah alternator, which is used to charge both starter and leisure batteries, but since there is no split charge relay it has to be selected by this rotary switch:

 

https://i.imgur.com/bIuH5f3.png

 

I'd like to do away with this switch completely since it seems like a really great way to a) forget to switch to starter battery before starting the engine b) forget to switch over after cruising for a bit to charge the leisure batteries c) accidentally switch to OFF and nerf the alternator. Luckily, the previous owner left a box containing a brand new 110Ah alternator, pulley, mounting brackets and instructions for installing alongside the existing one, which I believe will allow me to do away with that wretched switch.

 

Now, before I go ahead and start trying to find someone to install it for us, I wanted to ask if there was anything else we would need to get to complete this installation? If I understand correctly (unlikely) the "4 step alternator regulator" blue box also in that picture converts the alternator voltage to what the batteries need dependent on their current state of charge. Is that still going to be useable with the more powerful alternator? Will I also need another one for the starter battery? Thanks for taking a look! Josh

Edited by JoshS
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Just take care when mounting the 2nd alternater. The brackets may be quite flimsey and some mount on the aluminium timing chain cover. It is not unknown for them to break off damaging the casting. You will still need a battery isolating switch if this is the only one.

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1 minute ago, Mike Adams said:

You will still need a battery isolating switch if this is the only one.

I have seperate battery isolating switches for both leisure and starter batteries. Do you mean that I will need additional isolating switches between the alternators and their respective battery(ies)?

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2 minutes ago, Mike Adams said:

No. What you have is fine but that switch shown can also be used as a battery isolating switch.

I don't think it's currently wired in that way though, since I still have 12v power when it is set to the OFF position. I think it is literally just connecting the alternator to their respective batteries.

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So presumably there is are battery isolators elsewhere? To be BSS compliant the alternators need to route via their respective battery isolators, not be directly connected to the batteries.
 

Bearing in mind that to start an engine normally uses much less than 1Ah out of a typical 110Ah battery, therefore the engine battery doesn’t need a lot of charging.
 

Whereas you might take out 100Ah or more per day from the leisure batteries.

 

So, whilst I think you are planning to use the smaller alternator for the starter battery and the larger one for the domestic, an alternative approach would be to connect both alternators to the domestic battery and fit a split charge relay or voltage sensitive relay (VSR) to cater for charging the engine battery when the engine is running by connecting it to the domestic side.
 

The sterling regulator (blue box) will help a bit with charging, but not so much with modern alternators especially if you have two feeding the domestic batteries. If you are going to keep the charging systems separate (one alternator per battery) I would fit it to the domestic alternator.

Edited by nicknorman
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2 minutes ago, nicknorman said:

So presumably there is are battery isolators elsewhere? 

Yes, there are 2 separate isolators for the starter and leisure batteries. I would assume they are wired in a BSS compliant way, since it passed not more than weeks ago!

 

4 minutes ago, nicknorman said:

So, whilst I think you are planning to use the smaller alternator for the starter battery and the larger one for the domestic, an alternative approach would be to connect both alternators to the domestic battery and fit a split charge relay or voltage sensitive relay (VSR) to cater for charging the engine battery when the engine is running by connecting it to the domestic side.

That was the plan, but if it's possible to run both alternators (of differing sizes) in parallel, that does seem to make sense. I believe the boat was originally fitted with a split charge relay which caught fire, hence the previous owner removing it and installing the rotary switch! He was adamant that a relay was a bad idea, but perhaps a more recent one is going to be safer...

 

7 minutes ago, nicknorman said:

The sterling regulator (blue box) will help a bit with charging, but not so much with modern Alternators especially if you have two feeding the domestic batteries. If you are going to keep the charging systems separate (one alternator per battery) I would fit it to the domestic alternator.

Thanks for this info, so it sounds like the regulator is there to improve charging performance, rather than being an essential piece of equipment, since you don't say that I would need two of them if keeping the charging systems separate? Either way, it sounds like it's something else I should upgrade to a more modern version at the same time - if it will help improve charging performance.

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16 minutes ago, JoshS said:

Yes, there are 2 separate isolators for the starter and leisure batteries. I would assume they are wired in a BSS compliant way, since it passed not more than weeks ago!

 

That was the plan, but if it's possible to run both alternators (of differing sizes) in parallel, that does seem to make sense. I believe the boat was originally fitted with a split charge relay which caught fire, hence the previous owner removing it and installing the rotary switch! He was adamant that a relay was a bad idea, but perhaps a more recent one is going to be safer...

 

Thanks for this info, so it sounds like the regulator is there to improve charging performance, rather than being an essential piece of equipment, since you don't say that I would need two of them if keeping the charging systems separate? Either way, it sounds like it's something else I should upgrade to a more modern version at the same time - if it will help improve charging performance.

People tend to wire their single alternator to the engine battery, and then via split charge to domestic, thus maximising the current through the relay. If only people would connect the alternator to the domestic and use the relay to replace the very small amount of charge taken out of the starter battery

 

Anyway, a relay will only overheat if it is under-specified for the current, or has loose connections

Edited by nicknorman
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Using one of those rotary switches to switch the alternator output is a sure fire way of destroying the alternator if you ever switch it to off with the engine running.

Replace it with a VSR.

Have a look at Sterling products, the do a joiner that will allow both alternators to charge both batteries and act as an advanced alternator controller as well.

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34 minutes ago, JoshS said:

Yes, there are 2 separate isolators for the starter and leisure batteries. I would assume they are wired in a BSS compliant way, since it passed not more than weeks ago!

 

That was the plan, but if it's possible to run both alternators (of differing sizes) in parallel, that does seem to make sense. I believe the boat was originally fitted with a split charge relay which caught fire, hence the previous owner removing it and installing the rotary switch! He was adamant that a relay was a bad idea, but perhaps a more recent one is going to be safer...

 

Thanks for this info, so it sounds like the regulator is there to improve charging performance, rather than being an essential piece of equipment, since you don't say that I would need two of them if keeping the charging systems separate? Either way, it sounds like it's something else I should upgrade to a more modern version at the same time - if it will help improve charging performance.

Just to add some detail on the subject of 2 different alternators in parallel, if the demand from the batteries is greater than the maximum output from both alternators, they will both run flat out. As the battery state of charge starts to increase and the current demanded thus falls, if the alternators have the same regulated voltage then their currents will fall in proportion to the max outputs. Whereas if one has a higher regulated voltage or has a “magic blue sterling box” then it will predominate and the other alternator’s current will reduce, whilst that alternator with the blue box remains at full output. Not ideal in terms of load sharing, but not really a problem.

 

As Tracy says you could consider a new “magic box” from sterling that combines the output from 2 alternators and boosts the voltage to ensure faster charging.

 

I’ll also mention that there are two facets to alternator usage, one obviously being to charge the batteries, but the other being to power loads in use at the time, eg via an inverter. By combining the 2 alternators as we have discussed you probably won’t save a lot of time on fully recharging the batteries compared to the blue box on the 110A alternator, but it will allow eg a 2kw load on an inverter without taking much from the batteries. So it depends on what other equipment you have aboard and how you intend to use it.

 

Oh and finally, if you have 2 alternators in parallel it can be less obvious that one has failed and the other is now working much harder - depending on how you wire up warning lights etc.

Edited by nicknorman
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So the boat currently has a Sterling 1500W inverter which I believe is as old as the boat itself (15 years). I've not tried using it yet but when we do, it's only going to be for evening entertainment etc, no plans for a washing machine or other similar high powered electrics! Going to try to embrace the 12V lifestyle as much as we can :)

 

As with all these things, trying to find the answer to a question instead creates more questions! It sounds like the best option would be to get a new regulator / controller that allows us to combine the alternators to charge the leisure batteries, if we want to get the best from both alternators. But if that isn't going to give much improvement over just using the 110Ah to charge them (which aside from removing the not-very-idiot-proof rotary switch, is our main goal I think), maybe it's best to just connect the new one to the existing regulator and the old one to the and see how we get on with that.

 

Moving on to the actual installation, am I likely to be able to find someone who can do the whole job or am I going to need a mechanic and an electrician? Currently moored at Willow Tree Marina in Yeading, West London.

 

Thanks for all your help anyway! :D 

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6 minutes ago, JoshS said:

So the boat currently has a Sterling 1500W inverter which I believe is as old as the boat itself (15 years). I've not tried using it yet but when we do, it's only going to be for evening entertainment etc, no plans for a washing machine or other similar high powered electrics! Going to try to embrace the 12V lifestyle as much as we can :)

 

As with all these things, trying to find the answer to a question instead creates more questions! It sounds like the best option would be to get a new regulator / controller that allows us to combine the alternators to charge the leisure batteries, if we want to get the best from both alternators. But if that isn't going to give much improvement over just using the 110Ah to charge them (which aside from removing the not-very-idiot-proof rotary switch, is our main goal I think), maybe it's best to just connect the new one to the existing regulator and the old one to the and see how we get on with that.

 

Moving on to the actual installation, am I likely to be able to find someone who can do the whole job or am I going to need a mechanic and an electrician? Currently moored at Willow Tree Marina in Yeading, West London.

 

Thanks for all your help anyway! :D 

There are so many variables! If you have say 440Ah domestic batteries (4 x 110Ah) then the charging current with a standard 110 alternator will fall below 110Ah pretty quickly. If it has the blue box it will stay at 110A for much longer, but then it may overheat and if it does the blue box will shut it down somewhat so back to square 1! Whether or not it overheats depends on engine bay temperature / ventilation, and how fast it is running (faster = cooler). This is where pairing the alternators helps, even if the charging time isn’t much less, sharing the load helps to prolong the life of alternators (they run cooler) and means that any controller attached is less likely to shut them down due to overtemperature.

 

As to your last question, I’m a DIY type person but I would have thought a “marine engineer” type could do the whole job. Be careful though, there are a lot of cowboys out there, especially round London.

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1 hour ago, JoshS said:

 

That was the plan, but if it's possible to run both alternators (of differing sizes) in parallel, that does seem to make sense. I believe the boat was originally fitted with a split charge relay which caught fire, hence the previous owner removing it and installing the rotary switch! He was adamant that a relay was a bad idea, but perhaps a more recent one is going to be safer...

 

That is because people tend to instal them like they do in motorhomes, alternator feeds the starter battery and then the relay feeds the domestics. As Nick pointed out a boat starter battery requires very little from the alternator but the domestics can draw a high current for many hours and the relays don't like it. Feed the alternator to the domestics and the relay to the starter and it will be fine.

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16 hours ago, nicknorman said:

There are so many variables! If you have say 440Ah domestic batteries (4 x 110Ah) then the charging current with a standard 110 alternator will fall below 110Ah pretty quickly. If it has the blue box it will stay at 110A for much longer, but then it may overheat and if it does the blue box will shut it down somewhat so back to square 1! Whether or not it overheats depends on engine bay temperature / ventilation, and how fast it is running (faster = cooler). This is where pairing the alternators helps, even if the charging time isn’t much less, sharing the load helps to prolong the life of alternators (they run cooler) and means that any controller attached is less likely to shut them down due to overtemperature.

 

As to your last question, I’m a DIY type person but I would have thought a “marine engineer” type could do the whole job. Be careful though, there are a lot of cowboys out there, especially round London.

The boat currently has 4x 100Ah Yuasa M31-100S sealed lead acid batteries, not sure of the age or condition of them yet as we've not started using them in anger! So replacing / upgrading them is potentially on the cards at some point. Not sure how much money I'm going to end up throwing at electrics on the boat just yet. We don't have solar either and I was planning to wait until the spring for that (seems silly to buy now when we won't use it to its maximum potential for several months and the current tech may be cheaper next year?), so I might just try to live with what we've got this winter - discover how terrible it all really is - and subsequently not feel as bad about spending several thousand upgrading a whole lot of things next year!

 

Useful to hear your thoughts on sharing the load with the alternators though so I'll definitely keep all that in mind, thanks!

16 hours ago, ditchcrawler said:

That is because people tend to instal them like they do in motorhomes, alternator feeds the starter battery and then the relay feeds the domestics. As Nick pointed out a boat starter battery requires very little from the alternator but the domestics can draw a high current for many hours and the relays don't like it. Feed the alternator to the domestics and the relay to the starter and it will be fine.

Thanks for this, I definitely need to read a bit more to completely understand what order things should be wired up in, but this seems like something that could be done sooner than the rest of the planned upgrades in order to remove the rotary switch from hell!

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20 hours ago, JoshS said:

 

I'd like to do away with this switch completely since it seems like a really great way to a) forget to switch to starter battery before starting the engine b) forget to switch over after cruising for a bit to charge the leisure batteries c) accidentally switch to OFF and nerf the alternator.

 

Well a) isn't a problem as you will immediately realise what has happened. The danger you haven't mentioned is leaving the switch in the 'Both' position after you have finished moving for the day, then doing lots of energy intensive activities overnight (or over a few days), then finding out that you have flattened the starter battery as well as the domestics, and you now can't start the engine (unless you have a hand start).

 

Best to fit a VSR in place of the rotary switch. This will connect the battery banks when either is fully charged, and separate them when not. A conventional split charger will do this to allow a single engine alternator to charge both banks, but a VSR also achieves this with other charging sources such as solar or a mains battery charger.

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8 minutes ago, David Mack said:

 

Well a) isn't a problem as you will immediately realise what has happened. The danger you haven't mentioned is leaving the switch in the 'Both' position after you have finished moving for the day, then doing lots of energy intensive activities overnight (or over a few days), then finding out that you have flattened the starter battery as well as the domestics, and you now can't start the engine (unless you have a hand start).

 

Best to fit a VSR in place of the rotary switch. This will connect the battery banks when either is fully charged, and separate them when not. A conventional split charger will do this to allow a single engine alternator to charge both banks, but a VSR also achieves this with other charging sources such as solar or a mains battery charger.

 

point of order here in red:

 

No it won't

 

If its a bi-directional VSR then it will charge both banks when EITHER bank's charging voltage exceeds 13.6 to 13.8 volts and that is far from fully charged.

 

If its not bi-directional then it will charge both banks when only the sensed bank exceeds 13.6 to 13.8 volts.

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To turn this back to the first post a little bit, I found this old thread on here from someone who appears to have the same setup: 

The thing I'm now unsure about is that the OP says they leave the switch in the leisure battery position when the engine is not running, but a couple of subsequent posts suggests it should be in the OFF position (which is how I left mine when I left the boat on Sunday). Which would you say is the correct position, and is there a danger to leaving it in the wrong position when the engine is not running?

 

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12 minutes ago, JoshS said:

To turn this back to the first post a little bit, I found this old thread on here from someone who appears to have the same setup: 

The thing I'm now unsure about is that the OP says they leave the switch in the leisure battery position when the engine is not running, but a couple of subsequent posts suggests it should be in the OFF position (which is how I left mine when I left the boat on Sunday). Which would you say is the correct position, and is there a danger to leaving it in the wrong position when the engine is not running?

 

Yes But...Your switch is not switching batteries, its just switching the alternator output which is not how it is supposed to be used. Switch it off with the engine running will kill your alternator.

Get rid of it.

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1 hour ago, Tony Brooks said:

 

point of order here in red:

 

No it won't

 

If its a bi-directional VSR then it will charge both banks when EITHER bank's charging voltage exceeds 13.6 to 13.8 volts and that is far from fully charged.

 

If its not bi-directional then it will charge both banks when only the sensed bank exceeds 13.6 to 13.8 volts.

There are so many misconceptions about this. Relays, diodes, whatever. Split charge systems do NOT as we see claimed so often "prioritise" one battery. They do not charge one battery then the other, they charge both. The point is not to separate the charging of two batteries, it's to separate the discharge.

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6 minutes ago, Tracy D'arth said:

Yes But...Your switch is not switching batteries, its just switching the alternator output which is not how it is supposed to be used. Switch it off with the engine running will kill your alternator.

Get rid of it.

Yeah I get that it's just for selecting what the alternator is doing rather than the batteries (I believe this is also what the OP of the other thread I linked to has too) and I'm definitely keen to get rid ASAP! Just keen to make sure I'm using it in the best way possible until we can get it swapped out (for a VSR by the sounds of the advice on here, just need to find one that is future proof for when we add the second alternator and solar). Logically I would have thought that leaving it in OFF when the engine is NOT running would make sense, but the other thread seems to suggest it should be left in the leisure battery position (which is 1 on mine, but 2 on the other thread ? ). Presumably leaving it on both is a bad idea because you're creating a connection between the starter and leisure batteries?

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43 minutes ago, Sir Nibble said:

Leave it on one battery, doesn't matter which, switch to both with engine running.

That really is all you need to do for now.

Get your self a torch, notepad and pen; and spend some time to find out where everything is on your boat. It really isn’t like owning a house, the more you can find out for yourself the easier things will be when it comes to spending your money. Watching a tradesman spend hours of chargeable time just tracing the system before they can actually start the job you asked for is not what you want. They will of course have to verify things, but that’s a whole lot cheaper.
You could do worse than to start with the four thicker wires emerging from under the rotary switch; top left, up the right side, draped over the blue box and down the side of the blue box. Are the battery wires connected directly to the batteries, to the battery side of the battery isolating switch or to the load side of the battery Isolating switch? This sort of information would allow forum members to see if it would be safe to recommend the relocation of one wire on that rotary switch to give you peace of mind that the alternator would never be disconnected.

 

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50 minutes ago, Eeyore said:

That really is all you need to do for now.

Get your self a torch, notepad and pen; and spend some time to find out where everything is on your boat. It really isn’t like owning a house, the more you can find out for yourself the easier things will be when it comes to spending your money. Watching a tradesman spend hours of chargeable time just tracing the system before they can actually start the job you asked for is not what you want. They will of course have to verify things, but that’s a whole lot cheaper.
You could do worse than to start with the four thicker wires emerging from under the rotary switch; top left, up the right side, draped over the blue box and down the side of the blue box. Are the battery wires connected directly to the batteries, to the battery side of the battery isolating switch or to the load side of the battery Isolating switch? This sort of information would allow forum members to see if it would be safe to recommend the relocation of one wire on that rotary switch to give you peace of mind that the alternator would never be disconnected.

 

I should probably point out that I'm currently in Cambridge and the boat is moored in London. We're trying to finish up work commitments, sell all our belongings etc, with a view to us moving on to the boat towards the end of September, which is when I'll be free full time to begin to properly understand what's going on. So it's going to be a while before I can do what you suggest - which I'm absolutely keen to do - as I said in the intro thread I've got some savings and am planning to give myself a year to become boat savvy before deciding if and how we want to make living aboard our life.

 

I do actually have the original wiring diagrams in "the big folder o' paperwork" that came with the boat, so I think it would be good to retrace and redraw them, working out what has changed and labelling things properly as I go, as my first steps. And then I can keep the new ones digitally, so I can keep them up to date!

 

For now though, here are a bunch of photos I've taken the two times I've visited the boat - of course I'm already constantly kicking myself about all the gaps in them (at least I'm starting to build a list of things to look for next time we go I guess) which might be of use to start with: https://imgur.com/a/dqOf6o9

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47 minutes ago, JoshS said:

For now though, here are a bunch of photos I've taken the two times I've visited the boat - of course I'm already constantly kicking myself about all the gaps in them (at least I'm starting to build a list of things to look for next time we go I guess) which might be of use to start with: https://imgur.com/a/dqOf6o9

Just for orientation; are the white 5 litre containers on top of the domestic battery box? and is the 12 volt panel on the other side of the bulkhead to the rotary switch?

You’re going to love dealing with all that insulating tape ?

I see some interesting things on the 230 volt ac wiring. I’m not sure that wrapping three singles in tape is the same as using a 3 core flex ?. There is also a selection of different coloured singles at the top of the consumer/protection unit suggesting both old and new colour coding systems in use?, there’s a label for that! There are also some issues with the proximity of the 230v ac and 12v dc wiring, but easily resolved.

 

 

 

 

Edited by Eeyore
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1 minute ago, Eeyore said:

are the white 5 litre containers on top of the domestic battery box?

They were! That photo was taken before we bought the boat. The cupboard with all this in is nice and clean now and I intend to keep it that way (famous last words).

 

Here are two more seemingly meaningless images to help explain where things are a bit! https://imgur.com/a/YWjQNZf

The picture of the bedroom is just to show where I was stood (facing towards the port side) to take the picture looking into the cupboard, between the bedroom and the steps up to the stern deck. The cupboard door swings open to close off the aft cabin from the bedroom at night.

 

Looking into the cupboard (which is L shaped towards the stern). the domestic battery box is to the left behind the twin tub washer, on a slightly raised plinth. everything else is above the battery box on the left hand side around that corner, apart from the 12V breaker which is above the ironing board just inside the cupboard door on the right, and the inverter, which is opposite that on the left hand side just inside the cupboard door.

 

I think a lot of the wiring you can see behind the 220V consumer unit is the back of the instrument panel up on the stern deck, where both the domestic and starter battery isolators also are, down by the floor.

 

I really need to take my proper camera with a really wide angle lens to get everything in one shot!

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