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  #31  
Old 03-01-2010, 02:54 PM
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It also applies to maintenance free batteries that are not AGM.

"To improve the quality of battery charging on BMW vehicles, the charging voltage on approved BMW chargers has been increased to 14.8 volts."

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I believe that is because BMW has switched to AGM type batteries to eliminate the need for a vent tube to the outside of the vehicle. AGM batteries apparently need 14.7 volts to get a full charge.
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  #32  
Old 03-01-2010, 02:58 PM
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That is not the charging rate. Don't confuse the two.
Explain. The charging rate is the amperage the charger is flowing to the battery.
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  #33  
Old 03-01-2010, 03:16 PM
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Be sure that the charging amperage has been set at 15%-20% above the amp hour rating of the battery. Since the Deutronic DBL-430 is only adjustable in amperage increments of 10, it may be necessary to round up to the next higher amperage setting. Failure to do so will result in an undercharged battery. For a 90Ah battery, set to 110A and for 110Ah, set to 130A."
There clearly must be some translational problem from German as, quite frankly, it makes no sense as written. There is no way that charger is delivering more amperage to the battery than the numerical value of the AH rating.

P.S. That charging quote you posted sounds quite off to me. "Battery charging must be performed using an approved battery charger (recommended charging unit: Deutronic DBL 430) at a constant voltage up to max. 14.8V." I though charging at a constant voltage went out years ago when smart chargers can into being. It is generally accepted in everything I have read that the bulk of the charging (up to 80% of full charge or thereabouts) should be done at constant current, and that only the last 20% should be done at constant voltage. Charging a highly-discharged battery using constant voltage sounds like a good way to fry a battery.

Last edited by Penguin; 03-01-2010 at 03:29 PM.
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  #34  
Old 03-01-2010, 03:33 PM
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Not a translation problem as the document was written in perfect English and is a direct quote from a BMW document. I think you are confusing how a relatively simple $50 trickle charger works with a full size programmable charging system. If you've ever used a Deutronic system you'd know they are bulletproof, incredibly sophisticated and worth the $1000 retail price.

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There clearly must be some translational problem from German as, quite frankly, it makes no sense as written. There is no way that charger is delivering more amperage to the battery than the numerical value of the AH rating.

P.S. That charging quote you posted sounds quite off to me. "Battery charging must be performed using an approved battery charger (recommended charging unit: Deutronic DBL 430) at a constant voltage up to max. 14.8V." I though charging at a constant voltage went out years ago when smart chargers can into being. It is generally accepted in everything I have read that the bulk of the charging (up to 80% of full charge or thereabouts) should be done at constant current, and that only the last 20% should be done at constant voltage. Charging a highly-discharged battery using constant voltage sounds like a good way to fry a battery.
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  #35  
Old 03-01-2010, 03:41 PM
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Originally Posted by X5 Meister View Post
I think you are confusing how a relatively simple $50 trickle charger works with a full size programmable charging system.
No, I am not.

However much it costs, words are words. And it makes no sense whatsoever to charge a battery using only a constant voltage mode. So obviously there must be something wrong with the words, as it is unthinkable that such an expensive and sophisticated charger would "charge at a constant voltage."

P.S. I have an Electrical Engineering minor with my Mechanical Engineering degree, and have been working with electricity and electronics since I was 7 years old. So no, I am not confusing a trickle charger with a "full size programmable charging system."
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  #36  
Old 03-01-2010, 03:44 PM
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I guess it's not charger per se. It's device to keep voltage at solid 14.7 during programming.

P.S. Penguin, can you give me example of device that capable of doing what I need for programming?

http://www.baumtools.com/pdf/Regulat..._DBL800_14.pdf
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  #37  
Old 03-01-2010, 03:49 PM
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Battery Chargers and Charging Methods
"Basic Charging Methods

  • Constant Voltage A constant voltage charger is basically a DC power supply which in its simplest form may consist of a step down transformer from the mains with a rectifier to provide the DC voltage to charge the battery. Such simple designs are often found in cheap car battery chargers. The lead-acid cells used for cars and backup power systems typically use constant voltage chargers. In addition, lithium-ion cells often use constant voltage systems, although these usually are more complex with added circuitry to protect both the batteries and the user safety.
  • Constant Current Constant current chargers vary the voltage they apply to the battery to maintain a constant current flow, switching off when the voltage reaches the level of a full charge. This design is usually used for nickel-cadmium and nickel-metal hydride cells or batteries.
  • Taper Current This is charging from a crude unregulated constant voltage source. It is not a controlled charge as in V Taper above. The current diminishes as the cell voltage (back emf) builds up. There is a serious danger of damaging the cells through overcharging. To avoid this the charging rate and duration should be limited. Suitable for SLA batteries only.
  • Pulsed charge Pulsed chargers feed the charge current to the battery in pulses. The charging rate (based on the average current) can be precisely controlled by varying the width of the pulses, typically about one second. During the charging process, short rest periods of 20 to 30 milliseconds, between pulses allow the chemical actions in the battery to stabilise by equalising the reaction throughout the bulk of the electrode before recommencing the charge. This enables the chemical reaction to keep pace with the rate of inputting the electrical energy. It is also claimed that this method can reduce unwanted chemical reactions at the electrode surface such as gas formation, crystal growth and passivation. (See also Pulsed Charger below). If required, it is also possible to sample the open circuit voltage of the battery during the rest period."
There is no way that a sophisticated charger is charging the battery "at a constant voltage up to max. 14.8V." So I must assume there is some problem with the words, not the charger.
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  #38  
Old 03-01-2010, 03:55 PM
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If you open link I posted above it states:
Regulated power supply AND charger.
So, I guess I need "supply" portion of it. Can I get that cheaper then $925?

Thanks!
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  #39  
Old 03-01-2010, 03:58 PM
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Quote:
Originally Posted by katit View Post
I guess it's not charger per se. It's device to keep voltage at solid 14.7 during programming.

P.S. Penguin, can you give me example of device that capable of doing what I need for programming?

http://www.baumtools.com/pdf/Regulat..._DBL800_14.pdf
That's a different question from something that charges the battery. As I have not done any programming I have not investigated this, but what you need is a regulated power supply, not a battery charger, that is rated for the appropriate voltage and maximum amperage you expect to encounter during programming. Most battery chargers will not have a lot of ripple, but they are not designed to provide a rock-steady voltage, without any short fluctuations or minor ripple, as that is not really important to the function of battery chargers.

It appear the power supply in your link is designed with this in mind and is designed as both a battery charge and as a regulated power supply. It should work, assuming it can provide the required amperage (all regulated power supplies have a maximum amperage rating, beyond which they cannot maintain the voltage.)
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  #40  
Old 03-01-2010, 04:09 PM
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So, I guess I need "supply" portion of it. Can I get that cheaper then $925?

Thanks!
You could check the electronics supply houses if you wanted to give it a try; however, most 12 volt regulated power supplies you find in electronics are actually 12 volts, unlike the "12 volt" systems in vehicles, which typically run at 13.9 volts to 14.9 volts, or thereabouts, with the engine running.

Placing a large R-C (resistance-Capacitance) across the power supply/charger terminals can remove power supply noise and provide a limited amount of voltage stability, but the problem with using that on a smart battery charger, rather than a regulated power supply, is that there is always the risk that a momentary increase in load would drop the voltage enough to put the charger back into the start of a constant current mode.

The CTEK 7002 has a power supply mode which might work... but if I were to try that, I would probably do a little calculation and put a big capacitor and a resistor in series across the power supply terminals to provide some additional ripple suppression.

Check-out the CTEK 7002 power supply mode specs and compare with the regulated power supply in the link you provided.

P.S. I just checked the CTEK 7002 specs, and they say it has up to 4% ripple. This is unacceptable, IMHO, and it would take a rather large R-C to drop it enough, i.e., I wouldn't try it unless I had an O-scope to measure the actual ripple after adding the R-C network.

P.P.S. I found this adjustable power supply for $200:

Pyramid Regulated Power Supplies

Unfortunately, they do not give ripple and voltage stability specs. But it might be worthwhile checking with them, to tell them what you'd like to use it for and get the specs and their opinion on suitability.

Last edited by Penguin; 03-01-2010 at 04:20 PM.
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