2GM20 Alternator Upgrade?

[KevO]

I am upgrading my domestic bank from a single 70ah to a pair of 110ah wired in parallel. My 2GM20F has the original Hitachi LR135 (35amp) alternator. I have been offered a brand spanking new Hitachi LR155 (55amp) to upgrade it. I believe it to be fully compatible with the 2GM.

Question?

Apologies for the biff question but has anyone else done a similar upgrade and can you recall how the new alt was wired in? Was it just a straightforward swap one for the other job?

Kev

 

[prv]

I think the 55amp was a standard option on the 2GM20 - it's mentioned in the workshop manual. In fact, the workshop manual is probably a good place to look for how to connect it.

http://motoren.ath.cx/menus/yanmar.php

http://www.yanmarmarine.co.uk/pdfs/service_manual/EPB5494.pdf

Pete

 

[GrumpyOldGit]

I am upgrading my domestic bank from a single 70ah to a pair of 110ah wired in parallel. My 2GM20F has the original Hitachi LR135 (35amp) alternator. I have been offered a brand spanking new Hitachi LR155 (55amp) to upgrade it. I believe it to be fully compatible with the 2GM.

Question?

Apologies for the biff question but has anyone else done a similar upgrade and can you recall how the new alt was wired in? Was it just a straightforward swap one for the other job?

Kev

Question ? Is that a really HUGE alternator or have you got tiny hands ??

 

[prv]

Question ? Is that a really HUGE alternator or have you got tiny hands ??

Pete

 

[KevO]

Small......

Far away...

(actually not my hand... it belongs to the lady behind the counter)

 

[xeitosaphil]

I am upgrading my domestic bank from a single 70ah to a pair of 110ah wired in parallel. My 2GM20F has the original Hitachi LR135 (35amp) alternator. I have been offered a brand spanking new Hitachi LR155 (55amp) to upgrade it. I believe it to be fully compatible with the 2GM.

Question?

Apologies for the biff question but has anyone else done a similar upgrade and can you recall how the new alt was wired in? Was it just a straightforward swap one for the other job?

Kev

Thats exactly what I want to do, can I ask where from and how much? need to work out a budget! or find similar SH.

Incidentally that is what is quoted as being an option for the 2GM20 in the Workshop manual as previously mentioned.

I downloaded and printed the manual from the German Web site, and found it invaluable.

As I understand it ,if you have an insulated return set up as all original 2GM20 were supplied with, it is a direct replacement. If not you will have to supply an additional earth to the alternator from the ground. Others with more specific knowledge may confirm.

 

[Bosun Higgs]

Am surprised. Both the 2gm20s I had had 55 amp alternators as standard.

Anyway, all alternators are wired in essentially the same way. You'll not have a problem.

But dont think that you will input twice as many amps and charge in half the time with the bigger alternator. Doesnt work that way. The current flow depends on the circuit resistance and the difference between the alternator output voltage and the back emf of the batteries. So you only really benefit from a bigger alternator when the batteries are near flat. To give you an illustration, I have a 60 amp alternator and 300aH of batteries but I have never yet managed to get alternatoir output above 45 amps and it very quickly falls back to 10 to 15 amps when the batteries are 80% charged.

 

[awol]

Am surprised. Both the 2gm20s I had had 55 amp alternators as standard.

Anyway, all alternators are wired in essentially the same way. You'll not have a problem.

But dont think that you will input twice as many amps and charge in half the time with the bigger alternator. Doesnt work that way. The current flow depends on the circuit resistance and the difference between the alternator output voltage and the back emf of the batteries. So you only really benefit from a bigger alternator when the batteries are near flat. To give you an illustration, I have a 60 amp alternator and 300aH of batteries but I have never yet managed to get alternatoir output above 45 amps and it very quickly falls back to 10 to 15 amps when the batteries are 80% charged.

Have to agree. I have 2x110Ah charged by the 35amp Hitachi. It didn't seem to matter how long I ran the donk, I never got them fully charged until I added a Sterling regulator. The improvement was a revelation.

 

[Xcinquemila]

Just a few pointers:
Done it before;

Mechanically:
The pully needs to pull the heavier loads to, hence in my case needed to make a double pully with 2 belts.

Electrically:
Ohm's and Watts and volt are at play here.
- If your "charging" wires are not upgraded you will never make the amps. Hence double them.
- your current/charger regulator unit, you keep that the same? or is it build in the alternator?
- does the alternator need to carry loads other then charging you battery bank?

All what a bigger alternator does, is speeding up the process, but mind you, if your rpm's of the alternator do not meet the designed spec, you might blow a fuse or simply still remain underpowered in amp's

 

[charles_reed]

I am upgrading my domestic bank from a single 70ah to a pair of 110ah wired in parallel. My 2GM20F has the original Hitachi LR135 (35amp) alternator. I have been offered a brand spanking new Hitachi LR155 (55amp) to upgrade it. I believe it to be fully compatible with the 2GM.

Question?

Apologies for the biff question but has anyone else done a similar upgrade and can you recall how the new alt was wired in? Was it just a straightforward swap one for the other job?

Kev

I ran the 35amp Hitachi (which is the standard for all the raw-water cooled versions) for about 4 years, with 300ah of batteries and an Adverc external regulator. It was just up to the job.
After it had its 2nd diode bridge replaced I fitted a 90 amp Lucas unit which was in turn replaced by a 110 amp Magnetti Marelli, which survived the 2GM and was put on instead of the alternative 60amp Hitachi when I re-engined with a 3YM.
When I got round to fitting the Hitachi (the Magnetti Marelli was so obsolescent that the diode bridge replacement was not to be found in Crete) it lasted half a season and promptly melted.
My advice would be to carry on with the 35amp unit until it dies and then replace it with a standard short-body auto alternator.

The replacement for the melted 60 amp Hitachi cost me €49 in Agrinio - a nameless 90amp unit which took the standard Hitachi connections.
The Hitachi alternators suffer from a lack of sufficient cooling air and their strange connectors are quite easily rewired to work on any standard alternator especially as you don't have to bother with the rpm feed.
So - to answer your question - it's easy to replace the Hitachi alternator. With your size of battery bank and no external smart charger the 35 amp alternator with be quite adequate, even a 50amp unit will take as long to charge your batteries (and with just the onboard regulator that will take about 4 hours to get to 80% charge at which point it'll stop).
My recommendation would be to save your money towards an external smart regulator (Adverc, Sterling or Balmar) and when the little Hitachi alternator finally dies, replace it with a bigger output one designed for a diesel-engined van, but not an Hitachi.

 

[KevO]

Mmmmm.....

The 55amp Hitachi is only £60 brand new from the dealer. With a vsr or summat fitted surely that's got to be better for a combined 220 + 70 ah battery setup than the 35amp alt?

 

[awol]

Mmmmm.....

The 55amp Hitachi is only £60 brand new from the dealer. With a vsr or summat fitted surely that's got to be better for a combined 220 + 70 ah battery setup than the 35amp alt?

It won't do any harm but without some form of smart regulator it won't put the last 20% or so into the batteries any better than the 35amp yin. It will, as has already been said, fill really empty batteries more quickly.

 

[charles_reed]

Mmmmm.....

The 55amp Hitachi is only £60 brand new from the dealer. With a vsr or summat fitted surely that's got to be better for a combined 220 + 70 ah battery setup than the 35amp alt?

Why do you think that?

Both will do exactly the same job - in the same time - so keep your £60 and put it towards something that will improve your charging regime.

 

[KevO]

So what is the recommendation then?

Not stupidly expensive, suitable for relatively straightforward self-installation in place of the existing 1,2,both, off switch setup, will make the most efficient use of the existing 35a or a new 55a alt (plus a possible solar setup futher down the the line), will automate the charging requirements for when I forget to switch over and yet will allow me to call upon the other batts to start the engine in extremis should it all go tots up?

 

[vyv_cox]

This seems to be heresy to some, but I am perfectly happy with a 1-2-both switch. Use the domestic bank always, it is perfectly capable of starting the engine and will be recharged by the alternator. Occasionally, when you deem it necessary, start on the starter battery, charge for an hour, then switch back to the domestic ones. Your starter battery will always be ready for emegencies and your domestics will cope perfectly well. I have done this for years with battery life of at least five years, often more.

The best thing you can do with limited funds, as you have been advised by others, is to fit a smart regulator.

 

[awol]

So what is the recommendation then?

Not stupidly expensive, suitable for relatively straightforward self-installation in place of the existing 1,2,both, off switch setup, will make the most efficient use of the existing 35a or a new 55a alt (plus a possible solar setup futher down the the line), will automate the charging requirements for when I forget to switch over and yet will allow me to call upon the other batts to start the engine in extremis should it all go tots up?

If your 55amp alternator does all that, buy it! Adverc, Sterling, whatever smart regulator + a VSR or the Sterling alternator to battery charger will do what you want.

 

[JimC]

If your 55amp alternator does all that, buy it! Adverc, Sterling, whatever smart regulator + a VSR or the Sterling alternator to battery charger will do what you want.

Based on my own (limited) experience I would question whether you need a smart regulator and a VSR. My batteries used to be charged via a diode splitter and they never got fully charged. The splitter dropped the best part of a volt when I measured it so I replaced it with a Victron VSR which (obviously) dropped nothing. My batteries now charge fully and typically show 12.65 volts resting - like the battery in my car. If you're not wasting power in splitter diodes I think you may well have no need of a smart regulator. My engine is a 2GM20 with the 55 amp Hitachi alternator.

 

[awol]

Based on my own (limited) experience I would question whether you need a smart regulator and a VSR. My batteries used to be charged via a diode splitter and they never got fully charged. The splitter dropped the best part of a volt when I measured it so I replaced it with a Victron VSR which (obviously) dropped nothing. My batteries now charge fully and typically show 12.65 volts resting - like the battery in my car. If you're not wasting power in splitter diodes I think you may well have no need of a smart regulator. My engine is a 2GM20 with the 55 amp Hitachi alternator.

The smart regulator measures and controls from the battery side of the VSR so it compensates for the 0.2v drop.

 

[wotayottie]

Mmmmm.....

The 55amp Hitachi is only £60 brand new from the dealer. With a vsr or summat fitted surely that's got to be better for a combined 220 + 70 ah battery setup than the 35amp alt?

I'll put it to you in another way Kev O. Every alternator on every battery system starts charging at an amperage figure that gradually falls as the battery becomes fully charged. Whichever alternator you have the charging rate will drop below 35 amps at the same point in the process and once it does this, the bigger alternator is putting in no more charge that the smaller one would be. I'm going from memory here but my guess would be that that lower charging rate would be somewhere around 50% charged - the minimum you would let your batteries drop to anyway.

The smart chargers simply keep the alternator charging at a slightly higher voltage for a fair bit longer . MY alternator charges at 14.2 volts measured at the alternator using its own regulator and the Sterling smart charger I have is set for 14.5 v measured at the battery. So whatever alternator the smart charger is added to will charge faster for longer but again it isnt the answer to a maidens prayer.

In your situation I would buy the bigger alternator because £60 isnt much and there will be some advantage to using it. Just dont expect it to be a big advantage.

 

[JimC]

The smart regulator measures and controls from the battery side of the VSR so it compensates for the 0.2v drop.

But there is no 0.2 volt drop with a VSR, not mine anyway, there is no vltage drop at all. Why would there be?