AC charger smarter than the 3 stage "smart" charger?

[CSY Man]

Coming back from the Bahamas the other day we motored for 9 hours straight at regular "cruise" RPM and the batteries was fully charged, then some.
The solar panels also gave some juice between the rain showers.

Back at the dock I plugged in the AC charger and it kept pumping another 60 AMPs in the banks.....Huh?

The AC charger was brand new last year, a Xantrex 40 AMP unit with sensor wires to the batteries and all the bells and whistles. (Except temp sensors)

The batteries was also new last year, 4 golf-cart @ 220 amp/6 volts = 440 amps @ 12 volts.
Also a new start battery, but it should not be a factor.

The ship's "smart" 3 stage regulator is getting old, but seems to work well. The alternator is 150 amps strong and in good shape, so is the wireing and all.

So, the question is:

1) Why can/will the AC charger pump more juice into the batteries than the alternator/regualtor?

2) why is the batteries accepting more charge from one source than the other..?

3) Should I "crank up" the ships 3 stage regulator to pump more juice in?

(The new AC charger is installed and set to facotry specs, lead-acid and all that, not a wrong setting, or bad connection, or whatever.)

Looking forward to hear what the experts think as I am scratching my nogging on this one: Either the batteries are fully charged, or they are not.....

[btrayfors]

Several things might be going on.

1. Assume you mean the Xantrex 40-amp charger was putting out 40 amps into the "fully charged" house battery bank, not "60 amps".

2. I'd first check and clean all the connections between the alternator, smart regulator, and battery bank. Surface corrosion and loose connections could cause the alternator to undercharge the batteries. Also check that the wiring from the alternator and regulator is properly sized for your 150-amp alternator.

3. Next, I'd let the batteries rest for a couple of days, then measure their specific gravity and their voltage to determine their state of charge. Are they really fully charged, or near so?

4. For how long did the Xantrex put out the 40 amps? Many "smart chargers" have a little routine they go thru which includes running up the voltage/amperage at the beginning of that cycle. On some, for example, you could turn off a charger which had been on for a week and had been in the third stage of charge ("float"), wait a few minutes, and turn it on again...at which time it might well go into the first stage "bulk" charge for a short while, then cycle to the second stage "acceptance" charge for a bit, and finally get back to the "float" stage. The length of time required to go through all three stages can vary quite a bit from one charger to the next. I have one I'd like to toss overside for this reason, but it's really just an annoyance if you know about it.

5. Assume there are no battery isolaters in the charging circuit(s); these can cause an undercharge because the diodes drop the voltage as seen by the regulator.

6. It might be very useful sometime to borrow a clamp-on DC ammeter and take a couple of measurements near the battery bank to see how much the alternator and the charger are really putting out.

7. A 150-amp alternator is big enough to severely overcharge and damage a 440AH golf-cart battery bank if it isn't regulated correctly. You wanna be sure that the smart regulator is working properly and has this hummer in check!

Good luck sorting this out.

Bill

[hellosailor]

I'd look first to see if there were any bad wires, and if the charge sense leads from both systems were attached to the same point. It is possible that the two charging systems have been set with different voltage set points but ideally they would be calibrated and set to the same voltage, and neither would be "smarter".

If you check that, and confirm the voltage levels with a voltmeter, it is always possible that one of the chargers has gone daft in its old age.

[CSY Man]

1. Assume you mean the Xantrex 40-amp charger was putting out 40 amps into the "fully charged" house battery bank, not "60 amps".

Well, the 40 AMP charger can only put out 40 AMPS.
What I said, or parhaps meant to say if I was not clear, was that it pumped another 60 AMP/HOURS into the battery banks over a few hours.

Having installed a Xantrex battery monitor

http://www.xantrex.com/web/id/96/p/1/pt/5/product.asp

last year I am much more aware of what is going on and many times I get a surprise.

Again, I have no reason to belive that there is any bad connection, corrosion or anything wrong with the ships charging system.
If we assume that all is okay in that department: Why would one system put more into the battery banks than the other....?

it is always possible that one of the chargers has gone daft in its old age.

Yeah, but all the indications are normal.....

I'd first check and clean all the connections between the alternator, smart regulator, and battery bank. Surface corrosion and loose connections could cause the alternator to undercharge the batteries. Also check that the wiring from the alternator and regulator is properly sized for your 150-amp alternator.

It is all okay.

3. Next, I'd let the batteries rest for a couple of days, then measure their specific gravity and their voltage to determine their state of charge. Are they really fully charged, or near so?

Yeah, the above mentioned Battery Monitor tells me all the little secrets about fully charged and all that.
I am also aware that you add 20%.
(Say you drain the bank 100 amp/hours, ya need to put back in 120.)

For how long did the Xantrex put out the 40 amps? Many "smart chargers" have a little routine they go thru which includes running up the voltage/amperage at the beginning of that cycle.

Good point: I did turn it off after a while, then back on as I did not belive the numbers, or my eyes.
Yet, it should measure the batteries and look for an acceptance charge instead of pumping full power into fully charged batteries.

We are not talking about the boat sitting for a week, just hours after I got back from sailing/motoring.

Assume there are no battery isolaters in the charging circuit(s); these can cause an undercharge because the diodes drop the voltage as seen by the regulator.

Got an isolator in the system.
As well as a Solar Regulator.
There could be a problem with too much "stuff" in there, but still: Either too little juice from one source, or too much from another...?

It might be very useful sometime to borrow a clamp-on DC ammeter and take a couple of measurements near the battery bank to see how much the alternator and the charger are really putting out.

Got a digital multimeter on the boat, it should tell the same tale, never done it however.

A 150-amp alternator is big enough to severely overcharge and damage a 440AH golf-cart battery bank if it isn't regulated correctly. You wanna be sure that the smart regulator is working properly and has this hummer in check!

It has been working perfectly for the 8 years I have owned the boat, and another 5 for the previous owner.
There was never a problem, or a doubt, until I installed the new Battery Monitor and the new AC battery charger last year.

I keep maintaining the system, overhauling the alternator, checking for corrosion, cleaning wires, etc, etc....All is A1, just a nagging feeling that the AC charger is smarter than the old 3 stage "regulator"..

[btrayfors]

A digital multimeter won't tell you the same thing....there's no way you can put 150A thru such a meter. You need a clamp-on meter or a clamp-on attachment to a multimeter to measure substantial amperage flow.

Where is the isolater located in the system? Do both the alternator output and the battery charger output go thru that isolator?

[CSY Man]

I should add to the above that the alterator is indeed "putting out", it will charge at 14.2 to 14.4 volts whenever that house bank has been "down".

That being said, I never take the house bank down more than 75% or 110 AMP/Hours.

Coming back from the Bahamas the other day I was down 103 amps as per the digital Battery Monitor: It had been raining and the solar panels (2 X 75 watts Siemens) got a good break from the cloudy skies, putting out next to nothing..

(Need advice on a small, quiet, powerfull and cheap wind-generator. )

Motoring across the Gulf Stream it took 3 hours to fully charge the batteries,
Then the "float charge" kicked in and kept the banks at 13,6 Volts or so.
All normal and all good.

The puzzle however is that the AC charger, when plugged into the dock, was able to pump another 60 AMP/Hours into the battery banks......

[CSY Man]

there's no way you can put 150A thru such a meter.

Nah, I have never seen 150 AMPS from my 150 AMP alternator.
Never go that deep into discharge anyway, and only operate a single belt.
I have seen 93 AMPs charging on the above mentioned Battery Monitor.

I have a shunt on the system, but hooked up to the Battery Monitor...It should tell the same story..?

Where is the isolater located in the system? Do both the alternator output and the battery charger output go thru that isolator?

Not sure...Will check on that.

You could say that the batteries could eat 44 amps, plus system losses, which might bring it to 50-55A, trying to push the last 10% of the charge into the bank.

Good point, that may be the problem, or the solution..

Thanks for the help, I will keep checking and will report back.

[CSY Man]

I generally have got away from anything Xantrex. They have terrible support but I love my Link 10 monitor and it does work quite well. I just installed a new Balmer Smart Regulator.

Roger on that.

I am very happy with my Xantrex stuff, but never had to call customer support.
Hopefully never will.
Then again, there ain't no Santa Claus.

Good comments on all of this, thanks again guys...

[coot]

Originally Posted by CSY Man

The puzzle however is that the AC charger, when plugged into the dock, was able to pump another 60 AMP/Hours into the battery banks......

I have no answers yet, but I have some questions:

How do you know it added 60 AH to the battery bank?

How long did it take to add that 60 AH?

What is the AC charger doing now?

When you say "it took 3 hours to fully charge the batteries", does that mean that the amp-hour meter indicated 440 AH, or just that it indicated 13.6 V? What else do you know about the state of the batteries at the time you docked?

What is the water level in the batteries?

Maybe the answers will lead to some ideas about what is happening.

[Vasco]

I have a Link 2000. In two winters in the Bahamas I've watched it very carefully. It does some wierd things if you have wind or solar charging which I don't understand. If you charge using the engine or a Honda generator and AC charger , the monitor will automatically reset to zero on the "amp hours used" when you stop alternator or Honda charging even if the batteries are down 30 amps or so. (It just gets too slow to fully charge the batts at this stage so I stop mechanical charging) I have monitored it over a few fairly windless days when I ran the engine every morning. The monitor would reset to zero every morning after alternator charging even though I was down 20 or so amps, so cumulatively over the three days my monitor would show zero on amps used when I knew it was still down at least 60 amps. I could never understand this nor could anyone explain this so I learned to live with it. This "fault" is not unique to my monitor. It happens on all Link 2000's. It seems to happen if you have solar or wind charging connected.

[hellosailor]

Bill-
"A digital multimeter won't tell you the same thing....there's no way you can put 150A thru such a meter. " True, but a DMM can tell you many things and actually CAN be used to measure the 150A current--if you use a shunt, or measure voltage drop in a known length of cable. The resistance for 2AWG, 4AWG, etc. is known and available, if you then measure a cable length precisely, you can actually use one of the primary cables as a shunt and get a reasonably accurate amp reading from it. Outboard shunts can cost as little as $25 for 100-200A capacity but if the last couple of percent aren't critical, they're easy enough to fabricate as well.

CSY-
By a very rough measure, if you have a 440AH 12.6V battery bank, and you use a hypothetical 1/10th volt drop for each 10% of capacity...You could say that the batteries could eat 44 amps, plus system losses, which might bring it to 50-55A, trying to push the last 10% of the charge into the bank. Especially if one or the other charger was reading the voltage as 1/10th of a volt off--due to the charge sensor leads or a calibration difference. Or even just the logic behind their charging algorithms.

It might pay to ask each manufacturer what their opinion of this is, there may be a very simple answer based not on how "smart" each charger is, but just on how they've been programmed to do their jobs.

[Pblais]

I notice a similar things as well. With a smart charger you can't input all that many amps all that fast. It's why many cruisers spend most of the time between 50% and 85% of capacity in the bank. The last 15% takes a lot longer to refill and you rally don't want the bank below 50%. I find I never get the last 60 amp hours back (I have 2 group 4 AGM's) until the solar pannel finishes the job over a period of time after return from a trip or I stay plugged in at a marina. I use a Xantrex Link 10 and it tells a lot of good info just like you monitor does. I generally have got away from anything Xantrex. They have terrible support but I love my Link 10 monitor and it does work quite well. I just installed a new Balmer Smart Regulator.

[ssullivan]

This is simply a guess... a shot in the dark...

Could it be that the charge controller on the alternator is not set at the same breakpoints that the "smart charge" controller is? I mean... maybe the alternator "thought" the battery was full, when in actuality the smart charger was able to stuff another 60AH in there?

Might be worth exploring, since I think most new smart chargers are very adept at getting batteries up to full charge.

[CSY Man]

Could it be that the charge controller on the alternator is not set at the same breakpoints that the "smart charge" controller is? I mean... maybe the alternator "thought" the battery was full, when in actuality the smart charger was able to stuff another 60AH in there?

Yeah, maybe they sense the "full charge" different....
But there is also something about how much the batteries will accept the charge?

I will break out the manual for the 3 stage regulator and see if there is any adjustments to be made, althought I hesitate to screw with a system that is working great and has been for years....In other words, I am not sure it is broken, and I hestitate to fix it....

[btrayfors]

Don't forget to check the location and wiring of the isolator. This could be the problem if the alternator charging current goes through the isolator, but the battery charger doesn't.

Bill