Adding High Output alternator to a Westerbeke 7.6 BTD?

[dtfeld]

Since I've added a large inverter battery bank, I have been thinking about ways to keep all the batteries on the boat charged with a minimum of engine run time. One idea that I've been looking at is adding a Balmar high output alternator on my Westerbeke 7.6BTD.

In looking at the Balmar alternators, there are a couple options. Looks like a 100A version could be added using the single drive belt already installed, anything rated higher would require serpentine belt conversion. The good news is they make pulley kits for Westerbeke auxillary engines, and the best I can tell the 30B Three auxiliary is the exact same engine as in the 7.6 BTD. I crossed the water pump/pulley, crank pulley and alternator, and they are the same, so the AltMount 48-WSP-12C should fit and I'd end up with a J10 serpentine belt. The serpentine belt would likely be a better option as single belt would likely wear out much faster.

Then the issue become will the engine produce enough power to run the AC and DC side at the same time. Not sure about how much power I could draw off. The base engine on the generator is about 12 hp @1800 RPM, and capable of 27HP@ 3600 in the auxillary engine version.

The online product selector recommends something in the 70A-170A range.

 

[GnrlPatton]

Interesting idea, I'll be following your research on this. I've had good luck getting in touch with Westerbeke for technical questions like this, maybe reach out to them to get their take on it.

 

[dtfeld]

Interesting idea, I'll be following your research on this. I've had good luck getting in touch with Westerbeke for technical questions like this, maybe reach out to them to get their take on it.

I put a call into Balmar to get started, but they will be on the list as questions arise.

Edit: I fired of a couple emails to Westerbeke and a Balmar installer to see if this this has been done or recommendations...We'll see where it goes.

 

[kevin27]

Help me out here. So you want to charge the battery's with an alternator driven by the generator? These boats already have battery chargers( even large amp chargers if you want) powered by the generator. So I'm having a difficult time understanding what you would gain with this alternator step up that a battery charger already does. All the same in the end you're just doing it a different and more complicated way it seems. You have the run the gen either way so that is a wash. Plus you aren't going to run a Westerbeke at 3600 rpm nor would anyone want to simply based on the noise alone. I loved my Westerbeke I had years ago cause it ran at 1800 and was so quiet the water from the exhaust was the loudest part. My last gen was a Next-gen. Very reliable Kubota diesel engine and gen but ran at 2800. Had 3200 hrs on it but was a little loud.

 

[ttmott]

I would agree with the above. It seems that running an alternator to bulk a large battery bank at high current off of a generator would be quite a bit less efficient than installing a large charger. Plus, quite a bit more expensive. Also the drive belt arrangement on the generator would all need to change which begs the question - how, using WB pullies? But it's intriguing. For some reason I thought your Magnum inverter was an inverter/charger. I can't remember if you went 12 volt or 24 volt on the bank. Who was it coming up with a hydraulic drive off the generator to drive an alternator about a year ago on this site??
I think you would be much better off installing something like a Victron Centaur 12/100 or 24/100 charger. This way either your generator or shore power can charge the bank at up to 100 amps and not worry about all of the additional mechanical stuff. And I'm sure it would be a couple thousand cheaper.

 

[dtfeld]

Easy answer...Charge Time. I'd like to be able to fully recharge my inverter bank in 2 -3 hours of generator run time.

The Magnum does have a charger, however, if cranked to its full potential, it consumes 18A, and with how SR set up the AC panel, it overloads, so I have limited the charge output to prevent the Main breaker from tripping (or turn off the big draw items, but that's the only time I run the generator so that wont work). That equates to charge times that far exceed how long I run the generator, or only partially recharged batteries. Adding a second AC charger, would overload the other leg. SR just didnt intend this boat to be used this way.

If this would work (I have my doubts), I would have full 7.6kW of AC and the DC charging would be (mostly) done from the DC side. Just trying to use the power sources I have and use to spread the load given the way the boat is already wired.

 

[dtfeld]

The basic premise is this. Westerbeke bought and used little 2, 3 and 4 cylinder Mitsubishi diesels as the basis of their generators and auxiliary engines. The 7.6 BTD used the same engine as the 30B Three. Balmar and others are making kits for charging large house batteries with these engines, so this is commercially available off the shelf.

The issue in my mind is can the engine be fitted out this way without overloading the engine, or overheating the cylinders. Just because you can doesn't mean you should.

 

[ttmott]

Can't you simply add a circuit breaker sized for a charger?
A 100 amps of 12 volt charge is 10A mathematically at 120 VAC right?
100 amps of 24 volt is 20A at 120 VAC....
These numbers are well within the margin of your generator as long as the wiring and circuit protection is correct.

I believe the kit for the Westerbeke is primarily for when Westerbeke is for propulsion, like a sailboat.
To adapt to their generator configuration may be a bit more challenging.

 

[FootballFan]

I have what you are describing, factory installed.

My engines each have separate battery banks, 24V. I have a separate house bank (12V). My port engine has two alternators, one is 24V and charges the engine bank. The 12V charges the house batteries. I have 3 ways to charge house batteries: Shore power and Genset or the Port engine. There have been times when the Genset went down (water pump, impeller, etc.) that it was very nice to be able to feed the house batteries with the port engine.

The 12V is on its own belt.

 

[dtfeld]

Victron 100A charger draws 15 Amps at full load per the manual. Another consideration is where to locate it, I'm running out of places to hide things!

That's what led me to adding an alternator to the generator. It fits in the same place/space. Others are adding single or dual HO alternators as above, but that gets into more complexity/ expense.

Just rough (really rough lol)back of the napkin #s...

7.6 BTD produces 12 hp at 1800 rpm.

12 hp x 746 W/hp = 8952 W

8952-7600W= 1352 excess watts

1352W@12VDC= 112A.

I'm thinking its capable of rinning a 120A -150A alternator, as I'm not maxing out the AC side.

Cost is $1k-1.5k depending on a few factors, fits in the same space and is automatic, no user input required after install.

Will in work IRL...don't know!

 

[FootballFan]

I realize my scenario is not exactly the same as your thought, extra alternator on a main engine versus genset.

But it does offer a level of redundancy for keeping the batteries which the inverter draws from in place.

No question on whether or not the idling main has the power. On my boat a main engine idling is not that much louder than the genset running.

 

[kevin27]

If you have extra ac power which you do just upgrade your charger. I still am having trouble following your line of thought. These big boats are really ment to have power on all the time. Sure you can definitely do without the gen for a while but I ran mine most of the time away from the dock plus it keeps the gen reliable the more you use it.

 

[kevin27]

Plus if the gen died your main engines should also charge the battery's.............

 

[kevin27]

One more thought forget about turning up the rpm on the gen. The back end is designed to operate at a certain speed.

 

[dtfeld]

If you have extra ac power which you do just upgrade your charger. I still am having trouble following your line of thought. These big boats are really ment to have power on all the time. Sure you can definitely do without the gen for a while but I ran mine most of the time away from the dock plus it keeps the gen reliable the more you use it.

Cant upgrade the charger on the inverter itself, I'm already derating it not to overload the starboard system. I don't have enough excess AC power available on the port system to add a large AC battery charger, mounting space is also issue.

My boat is set up to be able to run everything without the generator for a minimum of 24 hours, as the genny is very noisy as its located right under/next to the main cockpit seating and aft cabin sleeping area. Common complaint on the 410. Looking to add a sound shield in addition.

As to why? The issue is being able to recharge a large battery bank in a reasonable amount of time. I judge that to be 2-3 hours of generator run time a day.

I posted these in another similar thread

https://stevedmarineconsulting.com/...ry-bank-size-and-charge-capability/?print=pdf

https://seabits.com/wakespeed-ws-500-regulator-review/

The Sea Bits article shows a great set up if your moving from anchorage to anchorage, but we dont do that. We tend to spend time in an anchorage for 2-3 days, using generator for cooking/hot water etc. and its a lot more complex to set this up.

 

[km1125]

Could you also integrate some type of load sensing on the A.C. side of the genset and use that to drive down the field current on the D.C. alternator so when the genset is highly loaded on the A.C. side then the D.C. side wouldn't have any chance of overloading it? Maybe even just a delay circuit that would cut off the D.C. charging for a specific amount of time (that would match whatever the cycle is for a large AC unit or the water heater?).

 

[dtfeld]

Can't you simply add a circuit breaker sized for a charger?
A 100 amps of 12 volt charge is 10A mathematically at 120 VAC right?
100 amps of 24 volt is 20A at 120 VAC....
These numbers are well within the margin of your generator as long as the wiring and circuit protection is correct.

I believe the kit for the Westerbeke is primarily for when Westerbeke is for propulsion, like a sailboat.
To adapt to their generator configuration may be a bit more challenging.

I think to add 100A charger would be 12-13A AC input assuming 85-90% efficiency. Keep in mind PO added a 3rd AC unit, so I'd have to manually shut something off. Not impossible, but I'm lazy. I'd have to take some critical measurements, but I'm usually 30 amps on the right side and 20ish on the left. It would be pretty tight on the AC side electrically.

The kit is for an aux engine, but the kits should fit...its the same engine, same pulleys etc. The difference is the aux has a transmission, the generator has a back end.

The question for a generator setup is wheather or not there is enough "exceess" power able to be produced without lugging, overloading or overheating the engine. This is where I have my doubts.

 

[dtfeld]

Could you also integrate some type of load sensing on the A.C. side of the genset and use that to drive down the field current on the D.C. alternator so when the genset is highly loaded on the A.C. side then the D.C. side wouldn't have any chance of overloading it? Maybe even just a delay circuit that would cut off the D.C. charging for a specific amount of time (that would match whatever the cycle is for a large AC unit or the water heater?).

Interesting thought.

Current thinking is to size the alternator based on how much "excess power" it can produce above and beyond the AC generator ends requirements.

 

[ttmott]

Interesting thought.

Current thinking is to size the alternator based on how much "excess power" it can produce above and beyond the AC generator ends requirements.

The Balmar external regulator has a feature called Belt load management which dials back the output based upon belt capability.

 

[dtfeld]

The idea for this came from these guys. This is talking about using the propullsion engine, but these principles apply to a diesel genset as well. He starts talking about the way AC generators are sized and run at about the 18:00 mark, and how much energy can be harvested. Basically, the way marine Gensets are sized and ultimately run, leaves a lot of energy going to waste, that could be captured.

->

Same is true on a 7.6 BTD. Looking at the base engines power curve, I pretty confident I could get upwards of 2000+ Watts of DC out of it pretty easily.