Charge Wizard needed?

Thanks very much, Time2roll!
I've been topping up car batteries here at -20C. I put 14.8 volts on one until the current drops to a few tenths of an amp. This is after the smart charger has charged to "full". It is remarkable how much longer it stays above 12.5 volts after this treatment. Nice to know my instinct is not too far off the mark. But clearly the Black&Decker smart charger is giving up way too soon.

Harvey51 wrote:
If there is a way to deduce state of charge from voltage without waiting for an hour or two for the surface charge to dissipate, it would be very useful to RVers without battery monitors.

When battery voltage is 14.4 to 14.8 and the amps drop to 1/2 percent of capacity then battery is full. So a 220 amp/hr battery is full at 1.1 amps.

However converters do not know how much is going into the battery vs being used in an RV. This is a major difference between a converter and a charger. The best converters (PD & IOTA) use a timer to hold absorption voltage. And have a timer to give a periodic boost if they under shoot a bit.

Thanks for that, Drew. I'm trying to understand how smart chargers work and have tentatively concluded that they apply the bulk charging voltage until the current falls, then drop to a lower voltage. Or stop altogether as my Black & Decker charger does. As you point out, there may be a considerable current going to RV appliances so this method is denied to the converter charger. Sometimes the Black & Decker starts again so maybe it is deducing something from the voltage while not charging, even drawing current from the battery?

If there is a way to deduce state of charge from voltage without waiting for an hour or two for the surface charge to dissipate, it would be very useful to RVers without battery monitors.

My amateur idea is that the battery bank itself should be made smart by counting amp-hours in/out and have the means to signal the charger what voltage is appropriate. As a satisfied user of a $25 battery monitor I believe this could be done at very reasonable cost up front and an overall saving because of better charging and increased battery life. Arduino microcontoller chips cost less than $5.

Harvey51 wrote:

Wizard? I would expect a battery monitor with a microprocessor to be counting amp hours in and out so it knows the state of charge and sets the voltage accordingly until it knows the battery is 100% charged. We all know the voltage is a poor indication of state of charge during charging.

Are there any converters or chargers that have Wizards worthy of the name?

The charge wizard isn't a battery monitor, per se, at least not in the sense that a Trimetric is. It doesn't attempt to figure out the state of charge of the battery, but only has the somewhat simpler task of trying to figure out when the battery has reached a fully charged (or nearly fully charged) state so it can change from "charge quickly" to "maintain battery" modes. Monitoring voltage is probably about the best way to do this, in fact; a TriMetric monitor even resets it's idea of "battery at full charge" based on voltage, so as to prevent excessive drift over time from tracking current in and out.

The PD charge wizard is rather crude in a theoretical sense, more than just by lacking battery current measurement. It doesn't have remote voltage sense lines for the battery (which would be a real help in less than ideal DC power distribution setups) or temperature compensation, among other things. Despite these, in actual practice it works quite well for its intended purpose while requiring little tinkering or technical expertise on the part of the user.

Some solar controllers are more sophisticated, and possibly some high-end inverter/chargers also have more sophisticated or at least more configurable charging profiles. I'm not aware of any of them that work by counting amp-hours while charging.

(Current sensing would have to be at the battery to be any significant use, and so require additional work in wiring. Sensing current at the converter would not help with determining state of charge since some of the power may be powering house loads rather than charging the battery, and since it would miss any energy put into the battery by solar or other means.)

Thanks everyone. Ordered it today.

"The Charge Wizard is a microprocessor-controlled system that constantly monitors the battery voltage and use to ensure a rapid; yet, safe, recharge. The Charge Wizard can select one of three charging voltages and one of four operating modes depending on the condition and use of the battery."

Wizard? I would expect a battery monitor with a microprocessor to be counting amp hours in and out so it knows the state of charge and sets the voltage accordingly until it knows the battery is 100% charged. We all know the voltage is a poor indication of state of charge during charging.

Are there any converters or chargers that have Wizards worthy of the name?

Ckacosta,

I give give you a direct and complete answer:
Get the Charge wizard and plug it in....
That will instantly get you a very good three stage converter and you will almost never have to add water to your batteries. Your house bank will always be topped off and will actually last longer both for draw down and in years.
Without it, you have to keep track of what your house bank condition is most all the time.

I have had a PD9145 on line to a pair of GC2 for 8 years. The first year without a Charge Wizard. They are just now showing some age. I have had to upgrade to a PD9260 to affect faster recovery on the generator when drycamped. Were it not for that requirement, the PD9145 w/CW would still be onl line.

Matt

Thanks

If you have easy access to your converter, the addition of the Charge Wizard is a simple two minute job. The 9100 series does not have the wizard but does have the provision to plug it in.
The 9200 series of converters has the Charge Wizard built in already.
Barney

Do you absolutely need it? no; you can leave it plugged in over the winter with a single-stage charger and not do any real harm to the batteries so long as you keep tabs on their water level.

Is it worth getting? For $25, I think it's a no-brainer: get the charge wizard. The batteries will require less tending (checking water levels) during storage, and will charge faster when discharged. The charge wizard system works very effectively in practice.