Battery charging rate - charger vs Alternator

Now that our boat is in the Chesapeake Bay and our use pattern is totally different than it was when we lived 5 minutes from the boat, we spend a lot more of our cruising time on the hook than we did when we lived in Long Island. A recent thread about Inverters and batt charging got me wondering...

Anyone have a rough (or accurate) idea of the charging rate of a standard type batt charger vs the charging rate for the engine/alternator on the same batt bank?

I'm specifically interested in the 32v banks and the original Lamarche Charger. I'm assuming that the charge rate of the main eng alternator is higher than the charger delivers but I don't know that for sure and don't have any manuals, etc here in Mexico.

So what will charge the batts faster, the charger (genny providing a/c) or the main engine spinning the alternator. Further, as someone suggested, will the inverter (Outback) charge the batts faster than the LaMarche batt charger if the inverter is connected to do so (mine isn't)?

I'm asking this because as the admiral and I were discussing our upcoming boat cruise, we recalled that the last time we were out on the hook, the batt bank supplying inverter power did not fully recover after a couple of days. It supplied the needed a/c power with no problem but after doing this for this period and running the genny for a couple hours a day to charge, the batt bank would not spin the engine for starting on the third day. The parallel start switch, of course, is there for that purpose and worked fine.

So obviously the batts weren't being completely recharged and the genny needs to run more than we were running it per day OR a more "powerful" or efficient charger needs to be involved.

For any of you using the 32v oem system for inverter power - how long do you have to run the genny per day to top off the batts charge-wise. I realize this is totally dependent on your inverter loads, your charger and your batt AH capacity but a rough idea would be helpful.

Mike: Following is a copy of my December 2005 post: "DC SYSTEM DESIGN"
Fast charging depends on (a) the regulator and (b) the relationship between the amp hour capacity of the bank being charged and the capacity (in amps) of the alternator or battery charger. Doesn't matter what the charging power source is. but the regulator control is critical.

An alternator and a battery charger of the same capacity (amps) and using the same regulator will charge a bank at the same rate. A three stage smart regulator will control either so as to charge faster than an old (taper) regulator which gradually tapers off the charge.

To get the fastest charge, use a big bank with AGM batteries and a big charger/alternator..with a three stage smart regulator....details follow below. Your original LaMarche charger is likely a ferroresonant taper type charger and will be generally SLOW in recharging. I replaced a 60 amp Sentry ferroresonant (old technology, likely similar to your LaMarche) with a "smart" 40 amp Statpower and the new smart charger was FASTER than the old!!!

I have three 40 amp Statpower plus and 150 amp from an inverter/charger so I can charge 250 amps at 12 volts when my genny is running. (It's more than I need for six 220 amp hour 8D deep cycles because I don't let them deep discharge.) I can run for weeks and weeks at about 45 minutes daily gen run time, about one hour daily if I also run a freezer in addition to my fridge.

All this discussion is accurate regardless of whether the bank is 12v, 24v, or 32 volt.

DC SYSTEM DESIGN
When your charging source ( amps) is properly matched to your battery bank capacity (amp hours), and your battery bank capacity to your daily load in amp hours, you can reduce genny run time to a minimum. This is VERY valuable for long term cruising away from shorepower because a balanced dc (battery) system reduces genny run time (and wear and tear), limits noise periods, and extends battery life. It pays for itself in marina fee savings.

Design steps are NOT rocket science:
(1) Determine your daily amp hour load, (say, 150 amp hours, is typical).
(2) Pick batteries (amp hour capacity) of your choice at least three or four times the capacity of your daily load, or more, (This limits daily discharge cycle depth resulting in longer battery cycle life, permits more rapid charging, and daily charging reduces sulphation.) (4 x 150 is about 600 AH, about three 8D's. Four or five is even better.)
(3) Size your charging source to about 25% of the battery amp hour capacity for wet cell, 40% for gel, 100% for AGM. (If well cell, you should charge at about 25% of 600 or 150 amps. AGM's will take close to 600 AH!)

You should be able to recharge from, say 50% to 85% or so in a hour.

Poof: you have a well balanced dc system! Of course you need the genny power to charge at this level, and perhaps power AC loads at the same time (such as a water heater and microwave) if so desired.
One way to help this along: perhaps eliminate electric cooking (a heavy draw) and convert to propane. If you run your genny all day anyway, as for air conditioning, the above accomplishes little.

Your Alternator is proubably 60A
your Lamarche is proubably 40A
Your Outback is proubably 60A

Your Alt will only out 60 if it's turning fast enough around 1600 RPM

You would be wise to hook up the outback to charge it's a much more modern sophisticated charge source than the old Lamarche it can be programmed to work any way you want it to and is capable of equalizing.

Brian

Good info Reb!

Brian, since you mentioned it, I seem to recall that the LaMarche is 40AH. So I guess another project when I get to the boat (ONLY 5 MORE DAYS!) is to connect the Outback to enable it to charge.

Am I correct in assuming - again, no instruction manual here - that the Outback could, if connected to both battery banks, completely replace the Lamarche as the boat's 32v battery charger?

Calder's book has a very detailed discussion on this and the worksheets to help with the figuring. It'll amplify REB's comments and provide explanations and options.

You can download the manual from outback but I'm pretty sure the outback is not a multiple bank charger Which means that without some other device it can only regulate and charge one bank. There is equiptment available to make it work on 2 banks but most of that stuff is 12V only. An isolater would work but I don't like them at all because you will get a voltage drop thru it. One thought might be to use the isolater and adjust the charge rate on the outback up to compensate for the voltage drop but I'm not sure if that adjustment would be linear or constant through the voltage/ amperage range. When I hooked up mine I combined both banks to make one big bank I did this so I could use the outback to charge and have the largest possable battery capacity. So I combined start and house bank into one obviously this presents a problem if that bank was taken down to far as I would not be able to start an engine or generator. To fix that I built a seperate bank of golf cart batteries dedicated to the generators so now I can always get a gen started to get things charged if I run them down. Using the outback to charge greatly reduces the amount of water the batteries need and the frequency in whick they need it. The outback is a modern Bulk/Absorb/ float type charger much better than the old Iron Horse Lamarche.

Brian

THanks - I found the manual on the Outback site...

So, I guess what I would do would be to disconnect the charging capability of the Lamarche to the one batt bank and connect the outback charger to that one, leaving the Lamarche circuit to the other bank in place.

OR - combine both banks and connect the Outback with the possibility (slim based on what I've experienced so far) of depleting both banks. Since I have a separate 12v system to start the NL genny, if both 32v banks were too depleted to start the mains, the genny/charger could still be started to charge them. Obviously not ideal in an emergency but workable I suppose.

Quote:

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Originally Posted by MikeP

THanks - I found the manual on the Outback site...

So, I guess what I would do would be to disconnect the charging capability of the Lamarche to the one batt bank and connect the outback charger to that one, leaving the Lamarche circuit to the other bank in place.

OR - combine both banks and connect the Outback with the possibility (slim based on what I've experienced so far) of depleting both banks. Since I have a separate 12v system to start the NL genny, if both 32v banks were too depleted to start the mains, the genny/charger could still be started to charge them. Obviously not ideal in an emergency but workable I suppose

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Combining the banks works well for me it gives me more capacity when I'm inverting and even if you don't need the aditional capacity your better off keeping the % of discharge as small as you can. I didn't remove the Lamarche It's a back up and aditional charge capacity if I need it.

Brian

Mike,
If you want to get all of the functionality out of the Outback, you need the Mate control module. This will allow you to change the default settings for charge rates, etc. You might also want to send a PM to Jcrlaw on the forum. He installed another part for the Outback and I can't remember thier name for it. It also plugs in where the Mate does but it offers even more control of the charge and invert functions. He needed it to monitor total AH draw down as he didn't want to let his brand new Roll/Surrettes get too low before charging. The Outback will also start your genny when needed to charge the batts if you set it up that way (another module, I think).

I had thought about using the charger off of the Outback for the house back while leaving my other charger on the start(sbd) bank, but since my Major Power charger is a newer smart charger, I have not done that (yet). The only reason I might consider it is to increase the charge rate to the house bank as you are thinking and to give some redundancy.

You definitely need to monitor the amp/hr drain by using an Emeter or Link 10 meter. You do not want to overdischarge those batts. You do not want to discharge them more than 50%. If you do you are killing that batt bank. An Emeter will allow you to monitor volts, amp/hr discharge and charge , amps being drawn/charged back into the batts real time and time to go (at that discharge rate ) . You can program all the parameters and also it keeps a history that can be useful. It also has a neat little graphical read-out that shows where you at a glance. Lead acid batts are not the best for inverter use as they cannot withstand the high charge currents that an AGM can and therefore take longer to charge back up .Personally I don't like the idea of using house /starting batts for an inverter. ................Pat

Mike, when you are here, look at my Link20 meter. It is very good for this kind of thing.

The LaMarche, which is an old ferroresonant charger if I am not mistaken, does not charge very efficiently. The charger in the inverter is almost certain to be a HFO type charger and much more efficient, with a flexible charging profile. If it can switch for different kinds of batteries, I would bet that it is.

What you might think about is adding better regulators to the alternators- external regulators that are programmable. They make the alternators much more efficient and will control them to shape a charging curve that is like the one a modern HFO charger puts out. I did this and (after my mysteriously blown alternator was repaired) I like the way the system performs. I had no problems with dead batteries with this system with the prior engines.

The best way to set up a boat's DC systems is to have both engines start from one bank of dedicated starting batteries and the house loads on a dedicated bank also. One engine charges the starting batteries, the other charges the house bank. They can be paralleled if need be, and there is an echo charger or combiner to keep them both charged if only one engine is running. This system is not that difficult to set up and it really does work better for all uses.

Mike,
If you want to get all of the functionality out of the Outback, you need the Mate control module.

I was thinking he had that but yeah if you don't for not much money you will know what's going on.

Brian

Before you start cranking up the charge rate for a faster charge. You had better look at the heat and the hydrogen that the battery is putting out at this fast charge rate . No battery likes heat and fast charges create heat.
Just a thought.

Bill

Most of the smart chargers have optional temperature monitors which can be hooked up to the batt bank. The Outback has that functionality as I recall from the manual.

60amps at 32v with the outback should result in some fairly quick charging depending on your battery bank.

We use about 400AH in 24 hours (for the fridge mostly) AT 12Volts... at 32V that would be around 180AH... which your outback should charge in 3 to 4 hours or genset run time.

just make sure that you relay system doesn't get confused if it sees power coming from the inverter... probably not but make sure that doesn't cause an issue because when you're going to connect the input to the outback, it's going to go in pass trhu mode.

speaking of inverters, has anyone used Magnum inverters ? they have a nice 4000W true sine with built in transfer switches and dual inputs which a client is is considering. The specs look good, made in the US and 3 year warranty.

Re this and batteries - I saw a great battery quote today:

"Very few batteries die of natural causes; most are murdered!"

Mike
I found the controller that jcrlaw installed. It's called a flexnet dc. Here is the link:

http://www.outbackpower.com/FNDC.htm

FWIW, the Outback 3232 has a 45a charging circuit.

Quote:

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Originally Posted by doc g

You definitely need to monitor the amp/hr drain by using an Emeter or Link 10 meter. You do not want to overdischarge those batts. You do not want to discharge them more than 50%. If you do you are killing that batt bank. An Emeter will allow you to monitor volts, amp/hr discharge and charge , amps being drawn/charged back into the batts real time and time to go (at that discharge rate ) . You can program all the parameters and also it keeps a history that can be useful. It also has a neat little graphical read-out that shows where you at a glance. Lead acid batts are not the best for inverter use as they cannot withstand the high charge currents that an AGM can and therefore take longer to charge back up .Personally I don't like the idea of using house /starting batts for an inverter. ................Pat

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Pat - So I once left a 32V light on and completely discharged my house bank in the warehouse over winter. It was dead for about 3 days before I plugged in and recharged it. Did that hurt the batts? They're Rolls HHG25PMs (4 X 8V = 32V bank). I know that hurts non-deepcycle batteries, but I thought deep cycles batteries could take a full discharge occasionally.

Doug

Every time you discharge a battery completely or near, you loose 20 percent of the battery's capacity. As Mike said, batteries don't just die we kill them.

BILL

Doug,
I can't answer your discharge question, but I do worry about leaving something turned on. So, while in storage, I always turn off all 4 of my main battery disconnects. It becomes routine to just reach in the ER and turn the house disconnect on and off as you come and go throughout the winter. It's cheap insurance against completely discharging a battery bank.

It's impossible to judge how much a single complete discharge would hurt a particular battery bank. If left discharged for a period, damage is greaty increased. If the battery is old it could spell the end. In cold weather, the damage is likely less pronounced. You can likely get some figures from battery mfg sites....seems like I read about 3% or 5% might be a rough estimate of power loss due to a single complete discharge...

I know that I cycle my inverter batts between 50-90%. This what the manufacturer (Lifeline) rec's . They say an occasional discharge to 30 % is ok .Every batt has different specs and yes if you fully discharge any lead acid batt you have damaged it,deep cycle or not. Deep cycles just don't get damaged as much by deeply discharging as say a starting batt would.......Pat

The only difference I see in a deep cycle batt is the thickness of the plates. Thicker plates take more time to charge, hold more amp hours of power and take more time to discharge or get the power back out of them. Thinner plate starting batts, provide power more quickly for starting applications, but they do not retain the power as long as deep cycles. If you want a good deep cycle batt, just look at the weight. More lead, means more amp hours. I don't see how completely discharging either type will have any difference on longevity. Both will be damaged.

I stumbled across a statement in Calder's Boatowners book saying maybe 100 complete discharges would end a battery's useful life...just an approximate generalization....