Upgrading Generator Alternator for House Bank

[O C Diver]

So this thread is most appropriate and the timing is perfect. Over the past few months I have been going through the this same mental exercise of trying to figure out how to decrease the generator run time to replace the 95-120 amp-hours and to do it in a manner that is cost-effective. Currently it takes about 3-4 hours of generator run time to replace ~100 amp-hours via the ProMariner 50-amp battery charger (House bank capacity is 745 amp-hours using six 6-volt wet-cell batteries.)

ted had read your earlier message at discharging 70% not 30%.. 4 hours sounds about right, an hour bulk or so and 2-3 hrs accept. that's kind of a normal day in the life for lead acid.

Kev,
Marty indicated that his 4 hour charging was to replace 95-120 amp hours. 120 amp-hours is less than 20% of his batteries capacity. If the goal is to get through the bulk and absorption stages, there's no way it should require 4 hours to restore 20% of the battery. 2 hours or less is very realistic.

Ted

 

[BruceK]

....
For the life of me I cannot see the logic in putting big DC charging hardware on the front of an 8BTD when it has a capable AC electrical end already installed that could easily drive an inverter/charger...

Well put.The only reason I can think of is to get all you can out of an already running genset, for free. That makes sense, but you have to acquire and fit the new big alternator and you have to cable from it to the batts to be charged. One gain would be redundancy,eg. if the charger died.
Generators usually just charge their own starting battery, under used ones don`t do that so well. My genset batt has it`s own regulated 25w solar panel to cover that.

 

[FlyWright]

Kev,
Marty indicated that his 4 hour charging was to replace 95-120 amp hours. 120 amp-hours is less than 20% of his batteries capacity. If the goal is to get through the bulk and absorption stages, there's no way it should require 4 hours to restore 20% of the battery. 2 hours or less is very realistic.

Ted

I agree. With genset run time, the amount of charge required is not so much a % of battery bank size as it is the need to restore what electrons I've consumed since the last recharge. The key is having a house bank sized to keep you in the 60-85% range most of the time. In that range, the acceptance rate of a deep cycle LA battery will be the greatest and will still give you a 10% buffer from what many consider the floor (50%) for draw down.

For example, my 660AH bank is sufficient to support my 100-150AH per day electron appetite. That 25% range from 60-85% provides me 165AH.

If you use 200AH per day and have a 100A charger, you should be good to go with a 2-2 1/2 hr charge. Assuming an AM and PM charge, you only need to recharge 100A/1-1.25 hrs charge periods twice per day. That's pretty common to do while prepping in the morning and cooking dinner in the evening.

To me, it's all about staying in the sweet spot of max charge acceptance rate.

 

[FF]

"To me, it's all about staying in the sweet spot of max charge acceptance rate."

This is what most experienced cruisers do , but there IS a price.

As the bank seldom gets to 100% charged it slowly sulfates and shrinks in total capacity.

Most seem to think it is an acceptable trade off compared to endless hours of noisemaker to get from 85% to 100%+.

Starting out with a bigger house bank is one solution that does not cramp your lifestyle .

 

[kev_rm]

Have you looked at the front of that gennie and seen what it will take to put a big alternator on there? And what kind of alt and reg it will take to get good charging? The hardware alone will take some serious engineering and fabricating.

For the life of me I cannot see the logic in putting big DC charging hardware on the front of an 8BTD when it has a capable AC electrical end already installed that could easily drive an inverter/charger.

If you want a big alternator for good quick charging, it is best on the main engine where it can work when boat is going somewhere. If on the hook, let the gennie do it through it's more than adequately sized electrical end.

I have looked at it and it looks a lot like every single other old school alternator I've ever seen, and I'm not sure what if any engineering needs to take place to put an 80 or 120 amp guy on there netting me another 40 or 80 amps for something on the order of $150. Adding a big AC charger makes no sense to me... extra conversion and far more dollars per amp.. But I will have to try to see.

 

[O C Diver]

I have looked at it and it looks a lot like every single other old school alternator I've ever seen, and I'm not sure what if any engineering needs to take place to put an 80 or 120 amp guy on there netting me another 40 or 80 amps for something on the order of $150. Adding a big AC charger makes no sense to me... extra conversion and far more dollars per amp.. But I will have to try to see.

One of the considerations in using a standard automotive style alternator is that you really need a different regulator. The stock regulators limit maximum voltage to around 13.8 volts. Most deep cycle (golf cart battery ) manufacturers specify a voltage greater than 14.6 for the bulk stage. Charging will take much longer at the lower voltage.

Ted

 

[FF]

Voltage is not the hassle with auto V regulators , the brain is.

In car service 95% full on start is the norm and simply holding up the voltage for lights and blowers is the designed task.

The auto brain will allow about 50% of what is needed at any state of charge.

A cruiser with a 100A bat set down 50A will see 50A till the batt warms up and then drop to about 30A of charge (25 for the batt and 5 to push it in).

The next hour there may be a 17A flow , 12.5 for the charge and 5 to push it in.

A car V reg charge pattern is Why the 3 & 4 stage regulators were invented.

Back in the day a cruiser would install a "T Mac" which was a resistor in the field line and adjust the voltage, as the batt charged.No problems during the start of the charge , but the attempt to push the batt to 100% SOC gave many boiled batteries.

And of course the usual 55A Motorola would get really hot if its 55A was asked to charge a large 200A++ house batt set.

For most folks a 135 large frame alt brand new from a truck shop and a good 3-4 stage V reg should be the second purchase.

The first a SOC meter , so you can watch the auto alt struggle and eventually the better setup do the real job.

Some weekend folks can get away with just the SOC , and a big bunch of care.

 

[sunchaser]

I have looked at it and it looks a lot like every single other old school alternator I've ever seen, and I'm not sure what if any engineering needs to take place to put an 80 or 120 amp guy on there netting me another 40 or 80 amps for something on the order of $150. Adding a big AC charger makes no sense to me... extra conversion and far more dollars per amp.. But I will have to try to see.

Are you sure your existing sheave, alternator placement angle and belt size would be correct on the genset to drive an 80 or 120 amp alternator? If not the cost to do this "conversion" could become a bit more than merely buying a standard alternator.

Then how about the cost of a first class regulator, wiring and fusing setup.. Plus, you may well be short of quick charging amps you're desiring as pointed out in FFs post #67 (whew).

Quite simply you are wanting do a laudable amp increase for less money than a new larger inverter and or charger. Go to eBay and look for used larger marine units and post a wanted on TF. Don't forget a great big 110V cost effective charger can be bought from Wal Mart too. You may surprised as to where you end up on this quest.

 

[FlyWright]

"To me, it's all about staying in the sweet spot of max charge acceptance rate."

This is what most experienced cruisers do , but there IS a price.

As the bank seldom gets to 100% charged it slowly sulfates and shrinks in total capacity.

Most seem to think it is an acceptable trade off compared to endless hours of noisemaker to get from 85% to 100%+.

Starting out with a bigger house bank is one solution that does not cramp your lifestyle .

Didn't mean to imply I always live at 85% or less when cruising. The house alternator packs a punch and in a couple of hours has me very close to 100% while running on the mains. This summer I'll probably move every clouple of days. Besides a change of scenery, this will provide me with plenty of hot water and a better battery SOC.

After a few weeks out, my boat returns to her slip and is restored to 100% with dock power. If I stayed out as a permanent cruiser, I'd have to seriously consider solar to provide the float to 100% while on the hook.

 

[MartySchwartz]

Great discussion. I really do not want to hijack Kev’ thread but since this is essentially the same subject I will explain my situation a bit further.

This is gonna be long so bear with me. I have reduced my DC usage as far as possible (mostly anyway) by replacing all lights with LEDs and by making sure I turn off anything not actually required when not in use. Given that, my typical usage, tracked with a Trimetric battery monitor is between 75 and 100 amp-hours in approximately 24 hours while on the hook. The primary usage is the Novacool refrigerator.

I have twin Ford Lehman 120s with the stock 52-amp Motorola alternators. The two alternators are ties together at a Sterling Alternator-to-Battery charger that combines the two outputs into a 100-Amp 4-stage charger.

Since the House bank is 745 Amp-Hours I can go a couple of days without running the generator since I can replace that 150 to 200 amp-hours with about 4 hours of engine run time. If I plan on staying put for more than a couple of days, then I generally run the generator to recharge the house bank each day so that I am not having to replace more than 100 amp-hours each day. I generally have to run the generator for 3-4 hours to push that 100 amp-hours back into the house bank (again tracked by the Trimetric battery monitor).

All of that is what led me to thinking I might be able to find a reasonably inexpensive way to reduce the time it takes running the generator to recharge the house bank. Things I considered are:

1. Adding a big alternator to engine side of generator. Serpentine belt kit can be had for ~$400 and 150-Amp alternator that has max output at around 1800 RPM can be had for about $400 so we are looking at an expenditure of close to one boat buck. The issue is that the generator will likely have issues trying to drive that alternator and maintain the 1800 RPM for the AC generator at the same time.

2. Get a nice Magnum inverter charger. This would be simple but would cost about $1500 +/-. I already have a working inverter (charger part does not work, Xantrex – we’ll not go there) that I really don’t use so replacing it is not really cost-effective.

3. Replacing the 50-Amp ProMariner charger with a 90-Amp IOTA charger and 4-stage controller (thanks for pointing me in that direction FlyWright). I can do this one for ~$300 plus some additional cost to upgrade wiring. The down side is that I could not run the water heater at the same time since it the IOTA charger draws about 22-Amps under full load.

4. Or I could change nothing and just live with the long charge times.

Marty.....................

 

[FlyWright]

Marty, I think you'll find the Iota draws much less than 22A. My DLS-55 says its max is 13.3 which is the limit to my Honda eu2000i. Normally, the Honda is relatively quiet, but gets a bit noisy on high RPM. I've NEVER heard my Honda run at high RPM with just the battery charger on.

Could that be a hypothetical peak power requirement? I've sure never seen it in real life on the generator.

 

[O C Diver]

I have twin Ford Lehman 120s with the stock 52-amp Motorola alternators. The two alternators are ties together at a Sterling Alternator-to-Battery charger that combines the two outputs into a 100-Amp 4-stage charger. Marty.....................

Does 1 of your Lehman 120s have a coolant loop to heat the water heater? If so, replace the alternator on that engine with the 150 amp alternator, and use your Sterling 4 stage regulator on that engine. When necessary run that engine for 1.5 hours at 1400 rpm to make hot water and mostly recharge the battery bank. After that, you could finish the absorption phase with the generator and battery charger.

2nd idea: Can you plumb the coolant loop of the generator to make hot water and then just buy the bigger battery charger?

Ted

 

[FF]

"2nd idea: Can you plumb the coolant loop of the generator to make hot water and then just buy the bigger battery charger?"

Co Generation , the way to GO , and use the 1/3 of your fuel that is heating the ocean.

Using the exhaust heat is a bit harder.

 

[MartySchwartz]

Does 1 of your Lehman 120s have a coolant loop to heat the water heater? If so, replace the alternator on that engine with the 150 amp alternator, and use your Sterling 4 stage regulator on that engine. When necessary run that engine for 1.5 hours at 1400 rpm to make hot water and mostly recharge the battery bank. After that, you could finish the absorption phase with the generator and battery charger.

2nd idea: Can you plumb the coolant loop of the generator to make hot water and then just buy the bigger battery charger?

Ted

Actually, the hydronic furnace loops through the water heater since that is the most common time we need hot water (all winter at the dock). Since there is only one loop in the water heater I do not currently have that option. Smallest water heater with two loops is a 15-gallon and that will not currently fit. I have actually been thinking about what it would take to add a heat exchange that would allow multiple sources for that water heater loop (different conversation altogether).

Had not even considered using on of the mains as the generator. That might not be a bad idea. I could probably sell the Westerbeake and replace it with on of those Efoy power cells (Fuel cell) and then just upgrade the inverter. Oh boy, you may have just started something my wife will NOT be happy about......

Marty.............................

 

[O C Diver]

Actually, the hydronic furnace loops through the water heater since that is the most common time we need hot water (all winter at the dock). Since there is only one loop in the water heater I do not currently have that option. Smallest water heater with two loops is a 15-gallon and that will not currently fit. I have actually been thinking about what it would take to add a heat exchange that would allow multiple sources for that water heater loop (different conversation altogether).

Two 3 way valves would solve that problem. I use a 3 way valve on the return side of the water heater coil to either direct coolant back to the engine or through the cabin heaters. You could easily use two three way valves on the water heater to select source and return. Pretty simple to plumb and only requires a few seconds in the engine room to switch from generator to propulsion engine.

Ted

 

[FF]

Folks that get told a low limit for pulley mounted alts , should ask the engine builder if the low load is a front bearing problem , or a crank robustness problem.

If its the front bearing TWO alts , one on either side can solve that.