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Old 27-12-2009, 11:37   #1
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Two Battery Banks Correctly Charged?

I have the usual setup, 500amp house bank plus start battery. Split diode, standard alternator. The batteries have therefore sulphated badly, presumably due to chronic undercharging as a result of the system design. I'm about to replace them, but don't want the same issues again. Ive looked at various options, split charge, smart regulators, alternator to battery charger, echo chargers etc- the alternator to battery charger seems to do everything I need, independant 4 stage charging for each bank, rapid charge, hose battery temp compensation plus alternator temp sensing. This is the product Sterling Power Products: Alternator to Battery Charger
However, it's got two drawbacks: 1) No backup if it fails 2) expensive.
So I looked at smart chargers: Sterling Power Products: Alternator Regulators (I have no connection to Sterling)
If I was to fit one of these for each bank, (total of 2) it would give me built in redundancy, and also reduce the cost! But- would it cause any problems, running two regulators from the same alternator? I can't envisage any issues, but bow to the superior knowledge on this site!
PS I also run solar panels, these charge the house bank via their own mppt controller.
Any feedback is appreciated
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Old 27-12-2009, 12:40   #2
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been through the charging delema and found the simplest is the best option.. Run the solar to the house bank and the alternator to the starter.. then install a switch to charge between the two from the alternator..
your starter batteries will remain isolated, your house bank will be charged by the solar, and if it drops to the point you need it charged, flip the switch and let the alternator charge the house bank..
for shore power, a pro 20 or 40 works great.. seperates the banks and charges each independently..
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Old 27-12-2009, 14:24   #3
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I have recently purchased some reconditioned batteries to run some farm machinery with good results. These have been desulphanated by a small charger that put out high voltage pulses and should be ableto be puchased
locally. Ordinnry charging will not remove the sulphated layer and will lead to dissapointment with battery capacity
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Old 27-12-2009, 14:30   #4
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Bryan and Wendy,

I am not familiar with the Sterling alternator-to-battery charger products, but I've read the literature. Seems to me that: (1) the claims are exaggerated; (2) the products are very expensive; and (3) in claiming much faster battery charging they pretty much ignore the all-important factor of alternator heating (even tho there's a temp sensor). You can't just take a regular alternator and get it to put out full power for very long without burning up the rectifier diodes.

In any case, there are very good alternatives. One would be to route all charging sources...alternator, solar, wind, battery charger, etc....to your house battery bank. Then, use a device like the Xantrex EchoCharge or the Balmar DuoCharge to keep the start battery topped up. It doesn't require much charging anyway, since engine starting requires very little AH draw (lots of amps, but for seconds only).

There are good external regulators available, too, which are fully programmable, have temp sensors, are fully potted for marine application, etc. The Balmar MC-612 would be a good choice, as would the Ample Power regulator. The Balmar has temp sensors for both the alternator and battery bank, however.

You're right to be concerned about sulfation of flooded batteries. This is what kills most of them in marine applications, since they are often undercharged for long periods of time. Occasional equalization helps. The MC-612 has an equalization cycle, and many battery chargers do, too. So, depending on your cruising style, it would be a good idea to be prepared for equalizing the house batteries using either the alternator or a shore-powered battery charger.

External regulators are not all that difficult to connect. There are lots of good instruction sets available, and even tutorials on how to convert an alternator from internal to external regulation.

Finally, in this sometimes murky world of flooded battery care and rejeuvenation, there are lots of claims and lots of proponents of this or that procedure. What I can tell you having investigated a number of these -- including an 18-month study of the little "desulfation pulsers" -- is that there's no convincing evidence that they really do anything, despite the glowing reports by manufacturers, retailers, and users. A respected scientific lab found the same thing as we did.

However, there IS a preponderance of evidence that keeping your batteries fully charged and occasionally equalizing them DOES make a big difference in their longevity and, particularly, in maintaining their capacity to store and deliver energy.

Fast charging, by the way, is NOT a way to extend longevity; it's harmful in the long run, however necessary or desirable it might be for a cruising boat wanting to limit charging times.

Bill
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Old 28-12-2009, 03:51   #5
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Thanks to everybody for this v aluable info. I will now expand my search of chargers further afield as per your suggestions. I have question:
If i connect my charge sources (lets just consider the alternator for now) directly to the house bank (ie bypass the diodes so no voltage drop) will this:
a) Charge the bank to full capacity faster than using a smart charger
b) 'look after' the batteries as well as using a smart charger- ie this will not have 4 stage charging, but i assume the charge rate falls off gradually as the battery resisance increases as charge level increases
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Old 28-12-2009, 05:25   #6
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No and not necessarily.

You definitely DO want multi-stage smart charging, both for relatively fast, efficient charging and to help protect both your batteries and your alternator.

You get this thru the use of an external smart regulator. The regulator does just as it's name implies: it regulates the output of the alternator, based on:

1. it's internal protocol for, e.g., type of battery; bulk, absorption, float charging voltages and times; etc., and
2. inputs it receives from the battery voltage sense wire, and from any attached temperature sensors.

Some, like the MC-612, are fully programmable meaning that you can modify most any of it's parameters to better suit your situation.

They also have very useful features like delayed startup, soft-rampup, information feedback, equalization cycle, etc.

We'd all like a simple solution to what is not a simple problem. A smart regulator, once set up properly, will give you that since it will take care of most things you'd otherwise need to worry about. Except for adding distilled water to the batteries every so often -- they won't do that :-)

Bill
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Old 28-12-2009, 05:53   #7
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Bill's advice is right on target, as usual!

My setup was a 600 AH house bank, charged by a large-case generator with a Balmar M612 external regulator, and a Link 10 to monitor charge state. The start battery was charged through a Balmar Digital Duo-Charge regulator, pulling the small amount of amp-hours needed from the house bank.

You'll almost never get your house bank up to 100% charge condition with an alternator, the exception being when you're motoring for several hours. The charging rate drops to a trickle when the batteries are nearing full charge, so running the engine/alternator for that last 5-10% is counter-productive. That's where a solar panel or a wind generator would come in handy--topping up the bank.
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Old 28-12-2009, 07:48   #8
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The first product you mentioned, the website says if it has a failsafe, it apparently just directly connects your alternator to your batteries if it dies. Problem I have with this is it appears that your batteries are now connected together and you will need a manual disconnect when you turn off your engine.

The second product looks to be a regulator to control the alternator. You can't use two of these. What it does is connect to an alternator without an internal regulator. It then turns the alternator on and off to control the output. You can't have two devices trying to turn on and off one thing.

I also know nothing about Sterling other than what I've been reading on their website since your post.

Quick question about your installlation as it sits now. If you have a standard internally regulated alternator does it have a remote voltage sensing wire and if it does is it connected at the battery or at least the house battery side of the diode splitter? If not then your alternator has never charged your batteries very far. The voltage being sensed is .7 volts higher than what the battery is getting and therefore the alternator's output is reduced long before the battery is close to charged.

Another possibility of a correct installation is an alternator I've heard of but never seen. It has two output studs, one that puts out .7 volts higher than the normal stud to compensate for the diode drop.

Anyway it might be you could get adequate performance with your current system by fixing that one problem of incorrectly sensing the voltage. If you do want to upgrade, a 3 stage regulator will charge your battery faster with less run time.


We ran into this on a charter boat. The batteries would never charge. My friend who was with us has to have everything perfect, even on a 10 day charter, discovered that they had slapped a diode splitter in the system without anything else. He bypassed it and we used the master switches to separate the batteries after charging. The funny part was returning to the charter company. They spoke french, even though my wife has a degree in french, her knowledge of technical terms did not go very far beyond "pile". It didn't help that they didn't know anything about electricity in the first place and had just added the splitter without knowing how to do it right. They finally asked does it work right now? Yes, if you use the switches as before adding the splitter. Good. Good bye.

John
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Old 28-12-2009, 12:39   #9
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Hi John,
thanks to you and all for the further info. To answer you questions re my setup, I currently have a factory fitted split diode system, with internal voltage sensing alternator, thus the chronic undercharging and sulphation problem. I was thinking about implementing a system which would effectively give me split charging, deleting the diodes completely. But I dont really want to fit a relay to do this. A smart regulator with two outputs, 1 per battery bank would be ideal, but the only product I can see which does this is the battery to alternator charger, as above. BY the way, the reason I'm looking at Sterling products, is that I'm based in the UK and ideally want a 'local' manufacturer for best after sales service
thanks
Bryan
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Old 28-12-2009, 12:58   #10
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Bryan,

I understand your thinking about a "split charging system", but I think there's something you're missing. Don't worry, very few people fully understand this and internalize it until they've really thought it through deeply.

THE START BATTERY REQUIRES VERY VERY LITTLE CHARGING. That sentence should be a poster in the engine room! In a typical marine installation, the starter draws about 250 amps. While that sounds like a lot, it draws those 250 amps for perhaps 3-5 seconds if the engine is in good shape and, maybe up to 60 seconds if it takes a lot of cranking to get started.

Let's take a value of 10 seconds...more than most engines take. 10 seconds = 10/60 or 0.16667 minutes / 60 = .0027777 hours X 250 amps = 0.69 amp hours.

Yes, that's right. It takes less than one amp-hour from the start battery to start the typical small diesel.

This energy is quickly replaced...in minutes...by the alternator once the engine starts. After that, all that is required is a very small charge to overcome the start battery's self-discharge rate (1-5% per MONTH) and any fans or other items which may run off the start battery.

Unlike automobiles, diesel-powered sailboats typically don't have headlights or heaters or big stereo systems or other 12V DC accessories powered from the start battery, nor does the diesel engine itself require ANY electricity to run.

In other words, it takes almost NOTHING to keep the start battery topped off. The typical alternator is just idling along after the first few minutes of engine starting.

That's why it makes sense to route the alternator's output, and the output from all other onboard charging sources, to the house battery bank. Then, one just uses any one of several little devices to bleed off a bit of current from the house batteries to keep the start battery topped up.

I agree with you about relays: I don't like them either (battery combiners, and the like), partly because they sometimes involve mechanical relays which can fail and partly because they often combine a near fully charged start battery with a deeply discharged and much larger house battery bank.

What, then, is the solution? Simple. Just use an EchoCharge or a DuoCharge (or another similar device) to maintain the start battery. I have an EchoCharge on my boat which has been flawless for the past five years, just as have others I've installed for clients. It's basically a voltage follower device, but it has some smarts, too. Today, for example, I was aboard and put an equalization charge into my house battery bank using a high-end Victron MultiPlus Inverter/Charger. When the equalization voltage climbed into the 15's and as high as 15.9VDC, the EchoCharge limited the charging voltage on the start battery to 14.6VDC, which is perfectly fine.

The more costly Balmar DuoCharge is actually programmable and will handle up to 30A, but it's overkill for most installations, IMHO.

By the way, all switching within the EchoCharge is solid-state....no mechanical relays.

Bill
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Old 28-12-2009, 13:29   #11
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Thanks Bill,
My main concern with the starting battery was overcharging, as i realise the actual current drawn is minimal. I had looked at the Balmar duo, but it does seem like overkill- however Ive just looked at the Xantrex charger-
Power Store
which does look ideal.
Thanks for the info- most appreciated
bryan
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Old 28-12-2009, 15:22   #12
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I agree with Bill entirely about overcharging your start battery, IF you have a 3 stage charger. If you have a regular internally regulated alternator the voltage setpoint is constant and you won't overcharge either battery any more than a car does.

John
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Old 30-12-2009, 09:36   #13
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The sterling uinits are both effectively alternator regularators the newer digital one is a full IUU 3 stage unit, whereas most alternator smart regulators as 2 stage or just simple max current types. Either is better then the internal regulator, even if you compensate for diode drops by battery sensing.

Usingv the echocharge to handle the starter batteyr is a very good way to go as its removes any conerns about ober charging that battery
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Old 13-01-2010, 21:34   #14
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this is a related problem I'm having;

Recently I started the diesel (volvo d2-55) and got a battery warning. The alternator (standard 60Amp) was putting 13V out on the engine display when normally it's 14V (ALWAYS). When I idled to 2000rpm the output rose to 16V. I have a 3x4d gel house bank (550Ah) and 1x4d gel start batt, so I shut down for fear of flying the batteries.

I'm guessing the internal regulator is shot, hence the varied V output???
The Link 2000 was showing 0-30 amps jumping all over the place (usually it's 60).

The boat is relatively new to me and I'm still learning the systems, like how exactly are my batteries charged but here is what I know. From the alternator the + runs to a split, from which it goes to the Start batt, and to the inverter (then to the xantrex 110V charger??? for the house batteries)
Everything has been working well so far, and I've never really had a problem with the batteries but I also never had to charge the batteries via the Diesel.

I'm now faced with what to buy;
- new internal regulator -$280 from Volvo
- New external regulator - $300 form Bomar (can I hook it up to the old alternator???)
- new HO alternator with ext. regulator - $800

I'm planning on cruising the boat for a month in may, and would like to be self sufficient on power (ie. no portable generator if I can help it and I have no solar/wind)

Also, had this happened on the water and I needed to motor for an extended period, what should I do? disconnecting the alternator is the best idea but how to do it without frying anything?

thanks
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Old 13-01-2010, 22:46   #15
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Before you spend the big bucks, I"d recommend that you spend a few bucks for an hour's time of a qualified marine electrician. He could check your setup and look at it in its entirety, rather than piecemeal thinking about this or that.

One thing right off: your 60A alternator is woefully undersized for the approx 730AH battery (house + start). Those batteries can suck a lot of juice when they're down aways...much more than your alternator can supply. The main danger here is burning out the alternator, since they weren't meant to supply near full capacity for an extended period, but were designed to maintain start batteries in cars (which requires very little charging).

Bill
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