Insulated Alternators?

[Tim Good]

I took my alternator in to be checked / serviced and they said it was a marine type which has an insulated terminal on where a normal one doesn't. What exactly is that? Is it just bonded into the anode loop?

Also they said it was a reasonable alternator and kicks out around 50amps. What is that like in today's standards? Its on a Perkins 80ho engine and feeds 4 service batteries and an engine battery.

Can I do better?

 

[Barbican]

Comments below assume 12v.

By insulated I guess they mean the ground connection is via a terminal that is insulated from the case rather than grounding through the case.

As for the output, depending on how much you want to spend, you can go way more than 50amps, but will need to consider several elements.

1) the drive belt, which if you have a single 1/2inch jobby will be good for a max of 100amps without having to upgrade the pulleys and belts.
2) the cables both positive and negative will need to be sized for the output amps, to avoid too much voltage drop, or melting......
3) the size and type of battery bank you are charging, and what output voltage/regulator will best serve the bank. There might not be much point in putting a 200amp alternator on if you have a 400amp sealed flooded bank because the batteries wont consume that amount of charge.
4) physical space available for the replacement. my engine space is very tight on the alternator side of the engine, so I have to stick to a small frame alternator which will still allow much higher amp output than standard (which was 80). There is space on the other side, but that would require custom brackets etc, and I don't want to spend that much.....

Not sure what type of mount you current engine/alternator have, but most variants are available.

Have a chat with a specialist like http://www.startermotor-alternator-store.co.uk/marine-alternator-21-c.asp who were helpful when I spoke to them..

 

[Billjratt]

Why did you start investigating it in the first place?
An isolated system (everything should be isolated) is good for the engine and there should be no need for obscure anodes.
50 amp is not big as generators go nowadays, but it depends on what it's trying to feed. You mention 4 x domestic and one engine battery -I guess each is circa 110AH, so now we ask the question as to how deeply you discharge them between engine sessions.
Roughly (very) if you've taken out 400 of your 550 AH it's going to take you 400 over 50 hours(8) multiplied by one over efficiency ( 1.4? ) to put it back -assuming the alternator could sustain maximum over that length of time.
Normally an alt only delivers max whack for a short time before the battery voltage rises and things settle down for the next (many) hours. You would appear to have quite a big load to charge if you have sat at anchor for a while.

 

[Tim Good]

Just opening this thread again...

I can get an updated 70 or 100amp alternator to fit directly on my Perkins engine. My current alternator is the Insulated type. But a new Insulated type is 2.5x the cost.

What are the benefits of Insulated and are they really necessary?

 

[Heckler]

Just opening this thread again...

I can get an updated 70 or 100amp alternator to fit directly on my Perkins engine. My current alternator is the Insulated type. But a new Insulated type is 2.5x the cost.

What are the benefits of Insulated and are they really necessary?

I question why you want to change as did someone else, if your batteries are good, and never deeply discharged on a regular basis, then you will never see the 50amps that your original alternator can put out. The batteries self limiting ability to absorb a charge is the important factor.
Stu

 

[PowerSlapper]

Just opening this thread again...

I can get an updated 70 or 100amp alternator to fit directly on my Perkins engine. My current alternator is the Insulated type. But a new Insulated type is 2.5x the cost.

What are the benefits of Insulated and are they really necessary?

Let me google that for you........ http://www.ybw.com/forums/archive/index.php/t-411084.html
Big question is "is your block permanently connected to battery -ve?"
If so then there would appear to be no benefit from installing an insulated alternator at 2.5x basic price

 

[VicS]

Just opening this thread again...

I can get an updated 70 or 100amp alternator to fit directly on my Perkins engine. My current alternator is the Insulated type. But a new Insulated type is 2.5x the cost.

What are the benefits of Insulated and are they really necessary?

If the engine uses the block as the common negative return there is no advantage as the negative terminal will probably be connected to the block somewhere/ somehow, other than relying on connection via the alternator mountings. ...... but they can be bridged if necessary


If the block is not used as the negative return then you will have to assess the way in which the negative connection is made and what are the implications of now connecting the block to the negative .

 

[Chris_Robb]

Let me google that for you........ http://www.ybw.com/forums/archive/index.php/t-411084.html
Big question is "is your block permanently connected to battery -ve?"
If so then there would appear to be no benefit from installing an insulated alternator at 2.5x basic price

I presume that your starter motor is also insulated return? In which case you will not have any connection to make your engine the return. So if you do change the alternator you may need to change the -Ve arrangement on to the block. This will probably mean changing the connectors and if the wires are big you will need to borrow a large crimper.

In anycase the existing wires will probably not be man enough to take the full charge of 100 amps without a serious voltage loss at that amps - you will feel it by heat! You could also just double up the cables - frowned upon as a practice but mine has been like that fro 10 years.

Do you need to do anything? that depends on your style of cruising. If you sit on marinas , I wouldn't bother unless you have to replace the alternator.

Do you have a Battery Monitor - do you know what amps pour into the batteries and at what voltage? You will find out so much about yor charging and electric usage by having one. Cheapest (and quite sufficient)_ is the NASA BM1 about £100.

At the end of the day its your cruising style that will dictate what you will need.

 

[William_H]

In making any decisions about alternator capacity you need to have an amp meter showing charge current. As said this varies and declines with battery charge so an actual typical current regime for your kind of use is what you need to know. Then you can decide if you need a higher capacity alternator and only if the existing one is charging at 50 amps or so for a long period.
This concept of an insulated alternator reminds me of a story on an aircraft some time back. The original alternator was insulated so have a hefty lead from body to the negative terminal. The engineer replaced the alternator with a standard body negative alternator. He had an earth lead going no where and a spare terminal on the alternator which unfortunately
was the terminal for centre of coils which gives an AC output for a tacho. So he attached the earth lead to the output terminal. This system had an alternator on switch in field circuit. So he runs the engine up to good revs and switches on the alternator field. The alternator pick up coils immediately saw a short circuit and the entire pick up coil structure was wrenched around with rotation until the wires were broken. beware olewill

 

[robmcg]

Careful with changing the alternator. Our new alternator came with an insulated return, the old one was non insulated and the rev counter and pressure gauges wouldn't come to life as a result of the change. Had to run a extra wire which was no problem but was initially a bit of a head scratcher ��