Battery-Charging Voltages

[Rick]

Once you have attempted to use Amp-hour law charging and the battery has been on float, say overnight, put the charger back on at the same drive level that you used to get maximum current from your carger (that equaled the number of missing Amp-hours on the previous charge cycle). Note the current. For those of you who have AGM or gel-cell batteries if the capacity of the battery has been recovered (note that I did not say state-of-charge) then the charge acceptance current will be near zero.

Near zero means about 100mA per 100 Amp-hour rating of the battery or less. If you observe this then the internal resistance of the battery is minimum and the capacity is likely to be maximum. More tests can be made as noted in other contributions in the history in this forum.

[Sandero]

From what I understand the regulators out there such as the MaxCharge612 have some sort of pre programmed set of charging profiles (3 stage) which is driven only by battery voltage, not by the missing amp hours.

What Rick is recommending is that if you KNOW the amount of missing amp hours then with the regulator you can manually tune the alternator's output by changing (upping) the voltage and keep the output of the alternator to match the value of the missing AH. Apparently the pre programmed charge profiles don't do this.

My questions are:

How can you know with any reliability the missing AH, especially if you monitor is out of sync? Or how do you know IF your AH reading is accurate? I understand the concept of starting from a topped up batter.

Assuming that you DO have an accurate AH figure, how do you manually change the field voltage? How do you do it with a MaxCharge and how do you do it with some other regulator. I assume it has to be an external one.

Can we assume that the present systems will continue to go out of sync over several cycles until the next gen charge parameters are in place in regulators?

[Rick]

First answering Bob: You can reset the accumulation of Amp-hours on the Link20 without disconnecting power. With no loads at all on the battery banks (perhaps verified by removing wire to a positive distribution post to guarantee) note the current readings of both banks. The readings should "rack" back and forth between 00.0 and -00.0 with and equal amount of time spent on the average on each "side" of the positive and negative (no positive sign shown). If the unit does not display in this manner the unit needs to have its zero point calibrated. There is a proceedure for both channels to do this.

If, on a previous charge cycle, you have met the charged parameters and the batteries have been on float for several hours then manuall zero out any accumulation (don't have to do this for positive accumulation because it will zero automatically with any drain on the bank). From here you begin your discharge cycle and the end reading will be accurate, assuming that the shunt wiring is correct and you do not have any "sneaker" wires to loads not passing through the shunt.

defjef; above explains how one can know the measured missing Amp-hours. Manually changing the field is easy if one has an alternator regulator with an adjustment such as the Alpha or the Incharge. Balmar regulators have a pain in the rear proceedure yet can be done. Others may not. Present systems should not "go out of sync" with proper monitor calibration and setup.

[bob kingsland]

Thanks Rick: when I said in my earlier post that that I shut it off and rezero I mis spoke... what I actually do is simply rezero, per the normal procedure. But I have to do it every time I use the charger, so the Link 20 is obviously not properly calibrated. Will see what I can do to recalibrate the zero point this weekend before messing with changing charging parameters. Am pretty sure that shunt wiring is correct but I'll check it again, and I know I have no sneaker wires to loads not passing thru the shunt. So it must be the calibration.
Thanks again,
Best, Bob S/V Restless

[Sandero]

Speaking of "sneakie" wires....

I have an "always on" circuit which is not defeated by the main switch and which are be wired to a pos bus off the batts for bilge pumps and radio / clock memories, propane alarm...but all negs return to a neg buss and then through the neg shunt. I assume these are not "sneakie" wires.

Does the Link20, for example include it's own load? If not wouldn't that over time skew the AH reading?

[Rick]

The zero calibration (done from front panel digitally) procedure is not in the manual although you may have read of it from a long ago submission.

Defjef, you must remove all loads including "always on" to check the zero of the meter. The link20 draws less than 20mA unless the ambient light is high. There is a phototransistor to sense ambient light which adjusts the intensity of the display so that in dark conditions it doesn't blind you. You should experience less than 1/2 Amp-hour for a 24 hour period. A significant accumulation of negative Amp-hours is either a real load over time or installation having a large common-mode voltage on the shunt relative to the black wire into the Link 20 or there is indeed a zero calibration offset.

[Sandero]

Rick,

Got it, Take everything off the pos side and see if the meter goes back and forth between -0.0 and 0.0. for equal times.

If it doesn't? and the procedure is not in the manual, can you provide a link?

Thanks!

[hellosailor]

Rick-
Less than 20mA sounds like a power pig these days. Wouldn't 20µA be more in line with modern electronics? (G)

A hundred plus bucks for a battery monitor is unreasonable to me. The Link is more of a total charging state monitor, and perhaps not unreasonable for that purpose, but given how useful a $20 dmm can be...one has to pause. Or at least, might be forgiven for pausing.

Reading back to your comment about what is or isn't a "proper" charging voltage...how do you feel about the perspective of more modern charging systems, i.e. MPPT systems from solar setups, where the "proper" charging is actually set by a look-up table and a microprocessor that is constantly leading the battery voltage by a set percent, and then pumping amperage instead?

From what I have been able to dig up, three stage, four stage, whatever-stage chargers are really obsoleted now, and the only "proper" charging regimen should be one similar to MPPT, where the battery voltage is monitored every few seconds and the charging voltage and amperage both adjusted to suit.

Now for THAT, I'm willing to pay more than $20. (G)

As to why a dedicated little voltage or amperage meter should start at $50-60 and rocket up from that point, when an entire DMM containing a lot more than just that is half the price, I've just accepted that some things in this universe will always baffle me.

[Rick]

Hellosailor,
No LED display will work on microamps. It normally takes 2-20mA just for one segment to say nothing of 4 digits having 7 segments. As it is we strobe the segments to keep power down. Even the Link 2000, which has an LCD display takes about the same power when the backlight is on.

If you read back on various threads discussing battery monitoring you will understand that a DMM will not suffice for battery monitoring. One needs a dedicated, permanently wired in monitor that is capable of simultaneously measuring, with good accuracy, dynamic range, and stability Amps and Volts. Calculations are made beyond that. No DMM can do that.

Peak power point tracking regulators for PV panels do not do any calculations or have look up tables. The algorithm is actually fairly trivial for control. The "regulator" merely measures Volts and Amps, multiplies the two together and either increases or decreases the buck voltage one increment at a time to "see" if the output increases or decreases. It keeps racking back and forth or up and down to keep power at a maximum. Voltage is not regulated, per se, in this scheme. This has nothing to do with what voltage a battery needs for a deep discharge capacity recovery. The idea for an MPPT device is that maximum power of a PV panel occurs at a voltage higher than a battery voltage under charge.

[GordMay]

Originally Posted by Rick

... One needs a dedicated, permanently wired in monitor that is capable of simultaneously measuring [and remembering], with good accuracy, dynamic range, and stability Amps and Volts. Calculations are made beyond that. No DMM can do that...

Might you have said measuring AND REMEMBERING and calculating ?

[Rick]

Gord's right, I forgot to remember!

[hellosailor]

Al Gore and no tables needed, an even lower parts count.

I'm aware that LEDs take more power--but I'm not stuck on LEDs. How about an LCD display instead, or regardless of display, having the display power itself off unless there's a human sitting in front of it? (I miss OFF switches!) My last LORAN drew about 440mA when in use--only 40mA for the LORAN, the other 400mA for the LEDs lighting up the display and keypad. You can bet I learned to keep THOSE off except when needed.

"a DMM will not suffice for battery monitoring."
And onceuponatime not so long ago, how did we monitor batteries without Link systems? A DMM may not be as good--but in many cases it will indeed suffice. Certainly better than the typical analog "9 to 16" expanded range voltmeters, which I've seen off by as much as 2 volts at one end of the scale if you adjusted them spot on at the other end.

How about a bluetooth app to let iPhones monitor battery state? And a little BT-endowed shunt to make it work? Come on, let's go make a fortune. (G)

[decktapper]

Hello Rick:
I would like to be clear on what you are saying. I know little about batteries, but have designed electronics.
If I have a 100 AH battery, and I equalized it at full charge, I then ran my refrigerator until I had withdrawn 50 AH I would initially charge at 50 amps, but I would cut the current in an exponential decay. When the battery was discharged by 40AH I would be charging at 40A etc. When the battery was within 5AH it would then go to a float charge for 24 hours.
There is no need to know voltage, we are interested in amp hours not watt hours?

Did I miss anything?

If you were handed a complete tested design for a N battery monitor/Charge controller and battery charger, with a local display, how much would the design be worth? How much could the device way, and how much space would be tolerable? Would it be a big disadvantage if the battery charger portion was limited to a maximum of XX amps? If my battery charger could only output 25 amps, should the charger charge one battery at a time to be closest to the ideal rate of charge?

How much should I expect the life expectancy of the batteries to improve over my old 3 bank 10 amp battery charger and dumb alternator?



Thanks Rick.
Decktapper

[Rick]

Decktapper,
You did not miss anything. We know that with marginal 3-step charging, or an acceptance voltage less than 14.4V @ 20 deg. C, that it is necessary to know kW-hrs in additon to Amp-hours in order to make a reasonable determination of what constitutes "full" (in addition to CEF and "charged parameters"). When using the Amp-hour law charging regimen determination of "full" is much easier and more reliable.

For flooded-cell batteries the Amp-hour law charging regimen can recover a 100% depth-of-discharge in less than 4 hours. For gel-cel and AGM batteries it will be 3.5 hours or less.

We know that the charger should be sized to deliver approximately 25% of the Amp-hour rating of the bank to guarantee sufficient current density to the discharged plates for uniform conversion of the sulphate formation to oxide formation.

Such "good" charging may make a life difference from as little as one year to 10 years (depending upon abuse, etc.).

Excluding the actual charger module I believe that the monitor/alternator regulator could be made to retail for around $350 and occupy less space than the Link 2000R. The Link 2000R could be reprogrammed to perform the Amp-hour law regimen today (or yesterday) if that product was under my control. Don't think that Xantrex makes that product.

A shore/genset charger design would necessarily be a switch-mode design and, therefore, quite lightweight and compact. The design would include the capability to "source current share" more than one module so that one could add 50A modules for up to say 500A. The caveat on such design would be the necessity of having to adhere to international requirements (like in the EU) for conducted and radiated emissions which raises the cost considerably over those which do not meet such requirements. Regardless, you can get a good idea of size, weight and costs by looking at existing switch-mode chargers on the market.

[BlueSovereign]

This is an excellent thread Rick, I wish I could understand it!

This is the ONLY area of yachting that sends shivers up and down my spine. I’m mechanically and engineering oriented (my early HS education insured that), but electrical concepts and principles twist my mind, and I feel extremely vulnerable regarding this as it is very vital to a modern BWC.

I worry, after I spend time and money on my new electrical power system, (Toyama AGM/Gel batteries, Mastvolt charger/inverter, Mastervolt MICC) I’ll somehow screw it all up because of my "mental block".

Any thoughts on "my confession"? That aside, your personal opinion please on the above equipment I intend to purchase/have installed.

Willliam