Balmar XT170 case ground alternator - grounding

[karwas]

Hello,

I have just recently installed new Balmar XT170 alternator,
replacing old Hitachi on my 4JH5E Yanmar engine.

This particular alternator is case grounded, non-isolated version.
Initially, I was thinking that this will simplify my installation by
not requiring separate ground cable. Now I am thinking it was a mistake.

I am simply afraid, that in case of any problems with a ground path
through mounting foot and adjuster assembly on top of alternator,
I will potentially run through a lot of problems, including burning diodes,
when the electrical load suddenly disappears.

Moreover, case grounding depends on proper connection between
engine block and batteries. This is the wire bolted on bell house of the engine,
and in my case is sized properly for starter motor intermittent use,
but not for charging large house bank with continuous 170 Amps for hours.
So I will need to replace this wire too.


So, as a safety measure, I would like to run separate ground wire,
assuring proper connection between alternator and negative side
of electrical system.

But here is a problem: where do I attach ground wire to the case of alternator:

The whole case is cover with paint, and the only threaded wholes are either
tiny (M5 thread), or have already their purpose (temperature sensor)
Friend of mine suggested using M10 bolt securing foot of the alternator,
which maybe an option, but there is no contact surface between
power lug and the case of alternator due to sliding spacer needed to mount
the foot securely without stressing the alternator assembly.

I am leaning toward sanding some of the paint around one of those existing
M5 holes, and bolting a proper ground power lug into that place.

Or, should I just stop worrying, and assume that ground current will always
flow through the case (all 170 Amps of it), and not worry about it at all?

Any advice?

Przemek
S/V Festina Lente

[Scott Berg]

Attach the ground to the pivot bolt or an unused lock bolt fitting

[karwas]

Originally Posted by Scott Berg

Attach the ground to the pivot bolt or an unused lock bolt fitting

I will consider one of unused lock bolt fittings on the upper flange (not shown on the picture I've posted), but pivot bolt in the foot, would rather be not the best option IMHO,
because the power lug will rest on small surface of the split spacer sitting
in the hole of the foot of the alternator.

[Wotname]

Originally Posted by karwas

Hello,

I have just recently installed new Balmar XT170 alternator,
replacing old Hitachi on my 4JH5E Yanmar engine.

This particular alternator is case grounded, non-isolated version.
Initially, I was thinking that this will simplify my installation by
not requiring separate ground cable. Now I am thinking it was a mistake.

I am simply afraid, that in case of any problems with a ground path
through mounting foot and adjuster assembly on top of alternator,
I will potentially run through a lot of problems, including burning diodes,
when the electrical load suddenly disappears.

Moreover, case grounding depends on proper connection between
engine block and batteries. This is the wire bolted on bell house of the engine,
and in my case is sized properly for starter motor intermittent use,
but not for charging large house bank with continuous 170 Amps for hours.
So I will need to replace this wire too.


So, as a safety measure, I would like to run separate ground wire,
assuring proper connection between alternator and negative side
of electrical system.

But here is a problem: where do I attach ground wire to the case of alternator:

The whole case is cover with paint, and the only threaded wholes are either
tiny (M5 thread), or have already their purpose (temperature sensor)
Friend of mine suggested using M10 bolt securing foot of the alternator,
which maybe an option, but there is no contact surface between
power lug and the case of alternator due to sliding spacer needed to mount
the foot securely without stressing the alternator assembly.

I am leaning toward sanding some of the paint around one of those existing
M5 holes, and bolting a proper ground power lug into that place.

Or, should I just stop worrying, and assume that ground current will always
flow through the case (all 170 Amps of it), and not worry about it at all?

Any advice?

Przemek
S/V Festina Lente

Balmar think the case grounding is sufficient (presumably).

Upgrade the engine ground cable if you believe it is insufficient; what size is it ATM?

I can't imagine any circumstance where the case ground could suddenly go open circuit due to the mounting bolts.

[GordMay]

What you are proposing is just an auxiliary negative ground path, so anything you provide will be an improvement over just the case ground.
FWIW: The current carrying capacity, of an M5 bolt, is roughly 50 - 75 Amps, when used on a circuit breaker or terminal strip.
This is a case of bigger is better.


According to Carling (Cct Breakers)
8-32 screw terminals are rated up to 30 amps;
10-32 (near = M5) screw terminals are rated up to 50 amps.
Carling E-Series circuit breakers also offer 1/4-20 screw terminals, which are rated to a maximum of 100 amps.
And F-Series breakers offer 3/8-16 screw terminals rated up to 700 amps.
➥ https://www.carlingtech.com/circuit-termination

[oleman]

Originally Posted by GordMay

What you are proposing is just an auxiliary negative ground path, so anything you provide will be an improvement over just the case ground.
FWIW: The current carrying capacity, of an M5 bolt, is roughly 50 - 75 Amps, when used on a circuit breaker or terminal strip.
This is a case of bigger is better.


According to Carling (Cct Breakers)
8-32 screw terminals are rated up to 30 amps;
10-32 (near = M5) screw terminals are rated up to 50 amps.
Carling E-Series circuit breakers also offer 1/4-20 screw terminals, which are rated to a maximum of 100 amps.
And F-Series breakers offer 3/8-16 screw terminals rated up to 700 amps.
➥ https://www.carlingtech.com/circuit-termination

I think you are missing a key contact point for cables terminated by terminal bolts. The major current flow is via the terminal to terminal contact. The mounting screw is only used to clamp the terminals together. That's why terminal makers get away with SS and mild steel bolts in their terminals and not more conductive copper/brass derived materials.
If those steel bolts are not correctly pasivated and torqued they will very quickly produce power loss and heat at the junction. There is a current crop of industrial batteries with 8 MM SS bolts uses as terminals extending from the lead post of the battery. A small amount of corrosion on the flat lead surface of the post is a major issue on industrial equipment where they are used.
Good luck with your vessel!

[stormalong]

You can (very carefully) drill and tap that candidate hole for a larger bolt. Just don't drill through into anything vital. If you do that in situ drill very slowly and vacuum up the tailings. It would be better to dis-assemble the alternator to do this. And remove the paint under where the terminal will go.

[Ween]

If you ask Balmar they will tell you mount a ground to one of the unused mounting holes at the top. I know ;-)

[knotnline]

Why don’t you sand the paint off at the temp sensor position, put ground lug against case, then temp sensor lug on top of that?
Copper lug has good thermal transfer.
12 v is from lug to case, not through the stud.

[kenbo]

Originally Posted by Ween

If you ask Balmar they will tell you mount a ground to one of the unused mounting holes at the top. I know ;-)

^^^This^^^

[donradcliffe]

I am not impressed with a new 170 amp alternator without a grounding post. Balmar must have been taken over by the marketing department.

They probably count on the fact that you will not be able to pull more than 100 amps out of it with a single v belt.

[kenbo]

Originally Posted by donradcliffe

I am not impressed with a new 170 amp alternator without a grounding post. Balmar must have been taken over by the marketing department.

They probably count on the fact that you will not be able to pull more than 100 amps out of it with a single v belt.

And you won't get 170A out of it for long either. No miracles in that alternator, it's still small case and the only safe way to get more amperage is more, larger wires in the stator and that means more mass and a larger case. But I'm sure it appeals to the buy high amp and derate crowd.

[MARC D]

For about the same application, I was recommended by a Balmar tech to use 6 series alternator instead of XT170 as this one was more intended for GM gas engines.

6 series alt. have dedicated negative post.

[UK Ade]

Extending an older post. I am thinking of the same alternator on a Yanmar 4JH5E. Did you resolve the negative ground? My existing Valeo is rated to 120Ah but only delivering 40Ah at 2000revs. Have installed a Balmar Ext Smart Reg ARS-5 but hasn't improved performance. Think my pos cable rating should accommodate higher amps and sizing of the XT170 fits the Yanmar block. The Balmar 200 does not. Existing Valeo alternator has a lighter weight negative cable attached to rear casing. But the engine block ground connection has a more substantial cable nowhere near as thick/AWG rating as the pos cable. Had not thought through the fact that case ground means the engine black ground cable (back to battery etc) would need to be the same rating as the pos, although in my current OEM set up presumably this is currently spec's for 120 Ah anyway.. How did you resolve your neg/ground install and also importantly what level of Ah delivery is the XT170 giving you now?

[Davidla]

Okay so what you are referring to as a case ground is in fact the 12 volt negative return path to the battery. At the risk of being flamed (I don’t care) there is no ground connection in your circuit. There is a positive and a negative path from the source. Although in this instance the alternator becomes a source when operating. If you think the bolts holding your alternator to the engine block are not of sufficient capacity to carry the charging current go ahead and add another wire to the block or direct to the battery. It won’t matter much. The path from the engine block to the battery is a different matter. If this was spec’d for example to carry a charging current from the battery of around 75 amps then you may need to increase it. I doubt it, if as like most production boats(?) this circuit also carries the starting current from the battery.
Put an ammeter clamp on the negative to the battery when it is at low charge state and run the engine at WOT. This will tell you if you need to update the cable. And I wouldn’t expect the reading to be anywhere close to 170 amps.