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Old 14-09-2020, 20:46   #1
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Join Date: Feb 2015
Posts: 145
Was asked to inspect a friend's boats charging systems

--------This is a long read, can skip to the end for the main questions where I'd enjoy some input, initially----------

It is a mid 70's hull with dual Detroit diesels. Lots of people have worked on it over the years. Some professional looking work, some much less so. Looks like periods of care intermixed with long periods of neglect.

No wiring diagrams, nothing is labelled, but it is not 'too' hard to follow individual cables from end to end, just time consuming and requiring some bodily contortions. I plan on drawing a wiring diagram and labelling things, after some input, on what I found.

Each DD has its own starter battery, 2 parallel 8D lifelines, port side engine the Lifeline 8Ds are brand spanking new. Starboard 8d's 'several' years old. Battery bank in center, 190AH AGMs, 4 6v's west marine branded, I'm told are 'about' 5 years old. Boat has not been used much. Lots of shorepower.

It has a Magnum inverter charger, not sure the model #, but the magnum remote display maxed out at 107 charging amps after we ran the inverter for an hour powering ~35 amps of load. ( residential fridge +?...) Batts quickly dropped to, but then maintained, 12.32 v powering 35 amps of load for that hour.

Each DD engine has a large frame alternator. I have separate questions about these alternators for later in this thread, or another thread. Owner said they were supposedly 'top of the line' back in the mid 90's.....IDK.

From each alternator runs 2awg + cable toward One of two individual Blue seas ACR's mounted side by side. The SB engine's alternator 2 AWG cable goes directly to a 300 amp blue seas battery fuse on the SB ACR input stud. The other terminal on this ACR goes to a perko On/OFF switch that turns the Center 'house' battery bank of the 4 6v GC-2's

These 2 side by side ACR's Both studs had a blue seas battery fuse, rated at 300 amps. 4 side by side 300 amp fuses.........

The Starboard side ACR has a jumper (2awg) cable going from ACR input to to port side ACR INput and a 4/0 OUTput cable to the house battery ON OFF switch and a 2/0 cable to SB side lifeline 8d's.

This 300 amp fuse jumpering the SB to Port ACR was blown. The output stud of the portside ACR ( with its own 300 amp fuse) has a spliced 2awg to 2/0 awg cable to Starboard side 8d battery. I was afraid to look too closely at this splice but It looks like hammer crimp butt crimps under the thick heatshrink.

Each 8D starter battery duo, for each engine, has another ON/OFF Switch at the battery box, that cuts power to the starter only. There are No battery fuses on the battery itself, and I assume the Detroit diesels would blow a 300 amp fuse when starting, and is why the fuses were on the ACR inputs AND output, rather than the batteries.

Time got short, Owner wanted to start the port side engine, which has not been started in a long time. It started with its new dual 8d parallel starter bank.

Both engines were started when the house battery bank was providing 35 amps to the inverter.

I measured SB 8d batteries with engine running, 12.54v
I measured port 8d (new) batteries with port engine running, 12.88v.
I measured middle battery house bank with engines running, 12.41v

I clamped my DC Clampmeter over StarB side Alternator output cable. 25 amps
I clamped my DC Clampmeter over Port side engine alternator output cable, 0 amps.

Magnum display said inverter was still drawing 35 amps.

So it seems to me the Port alternator is done, there is only one of 2 v belts attached.

The StarB alternator seemed to max out at 25 amps. There is a 'wart', with multiple wires attached to side of SB alternator. I have pictures.

A few months ago, on a very brief inspection the starboard engine alternator had the Sb starter bank at 14.9v. Lifelines, no good, if that lasts.

When we shut down the engines the New port side starter 8ds rebounded to above 12.9 instantly, and the Sb side older 8d's took 15 minutes to rebound to 12.85v+.

The house bank was still inverting, sucking 35 amps from them, and their voltage was back in the low 12.3's.

Turned off inverter, everything. I R&R'd 300 amp fuse, and plugged into shore power.

Magnum inverter charger charging amperage rose to ~108 amps over about 20 seconds then held steady at 105 amps measured by my clampmeter and as shown by the display. I heard both ACR's click and then all batteries showed the same voltage on the main analog panel. Batteries still accepting 100+ amps when we buttoned everything up.

The Magnum is set to the 'flooded #1' charge profile and was floating house and starboard at 13.2v when I entered boat. Port 8d's were not hooked up.

The west marine AGM gc-2 house bank likely have a higher recommended float voltage than teh lifelines. I am not sure who makes them, but perhaps EastPenn?

There is room for 8 GC-2's as a house bank. Owner wants 8, not just 4. Lifelines will be purchased even though the west marine AGMS still have some life in them.

Some of the wire terminations/ joinery looks OK, some Looks to have used a hammer crimper. I did not peel back the heat shrink, yet, still assessing things.

Does anybody see any reason for the four 300 amp battery fuses to be on the ACRs input and outputs. I think it was the most convenient place to place such a fuse, and that the 300 amp rating is far excessive for the wire gauge.

I was thinking about putting one 300 amp fuse on the Magnum's 4/0 output cable, and moving the battery fuses to the batteries or the battery switches, using 175 amp fuses, just so they are close to battery but are not asked to pass starter current.

Both 4/0 cables to both engine's starters, are unprotected, and in fact in contact with the metal supports in the area. Obviously I will protect these better.

Regarding the alternators, it appears one is unficntional and the other appears to max out at 25 amps. They are the biggest alternators I've touched, I'd expect them to be rated for 200+ amps.

I know the 14.9v the Starboard alternator was holding the starter 8d lifelines at is far from ideal, but no idea the voltage once things would warm up.

I could likely talk the owner buy into a new large frame alternator and a balmar 614 voltage regulator, maybe two, one for each engine. I'm not sure how capable of a system he really wants, or needs. Spending other people's money can be fun, and I'd enjoy gaining the experience, and work.

Its hard to tell as I did not have a proper straight edge, but I think the SB alternator suffers from parallel belt misalignment. 2 V belts, different brands, one much tighter than the other, both belts vibrating badly with engine running.

Does anyone see any reason some previous worker, who likely installed the magnum charger inverter, to put battery fuses (300 amps) on the blue seas ACR's input AND output studs, rather than at the batteries?

I think it was simply easier as access is right there, but this assumption could be ignoring something else

I think the one 300 amp fuse was blown as the Port side battery bank was toast, and current from the Starboard starter battery, while engine was running and had triggered the ACR's, tried to supply the port engine starter.

I'm Looking at this boat's wiring as a challenge. The owner has funds to throw at quality parts, and labor, and I'd like to safely dial it the charging system, and gain experience and gainful employment.

Supposedly, the most previous workers on it, to install the Magnum inverter charger, were well paid highly recommended professionals, but what I have found seems to indicate they were far from, and took lots of shortcuts.
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Old 15-09-2020, 20:15   #2
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Re: Was asked to inspect a friend's boats charging systems

Too much to read. Draw diagrams...
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Old 15-09-2020, 22:30   #3
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Re: Was asked to inspect a friend's boats charging systems

Was mainly wondering if there was any good reason I could not think of, why some previous marine sparky put Blue seas battery fuses on the circuitly distant Blue seas ACR's rather than on the battery + terminal, as designed.

Starter current and nuisance fuse blows, is a concern but I can put them on the On/off perko switch mounted at battery box and avoid that possibility an be much closer to the battery, as opposed to ~4 meters away.

I know they wont fit under the mounted switch as is.
I've got a plan for that.
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Old 17-09-2020, 21:56   #4
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Join Date: Sep 2014
Location: Auckland, NZ
Boat: Compass 790 , 7.9 metres or 26 ft
Posts: 1,740
Re: Was asked to inspect a friend's boats charging systems

Sternwake as you know from my previous thread I know little about electrical systems but reading between the lines I think it is a mistake to try & save $$ for owners who just want something that works right now & can afford to pay for it.
Following yr experience with interest.
I've never had the luxury with working on unlimited budget on my own projects but have done a few where I had no idea what the limit was & it's definitely a mistake to try & save money then
I'd ask mainesail to devise a system that suits the owners parameters & you can do the install.
You can ask him for explanations for why he does it the way he does.
Get the price, present it to the owner & work from there.
Good luck
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boat, charging

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