Charger-need translation from German

[matic]

I think a lot of people will benefit from translation

http://www.universalhost.de/html_bit/b-charger.htm

[Ads]

Just follow the schematic. You can’t go wrong! Get the data sheet from http://www.maxim-ic.com You can use the MAX712, MAX713 for NiCad/NiMH or the MAX846A, MAX745 for Li batts. You can get FREE samples of these sent right to you door. Note: the MAX846a and MAX745 are smd compontents so you will need to be handy with a soldering iron.

[ph2t]

Hey Ads! Good to see you’re still around dude! :smiley16:

As for a translation, here’s the link to the site matic posted via the transation program babelfish:

http://babelfish.altavista.com/babelfish/urltrurl?url=http%3A%2F%2Fwww.universalhost.de%2Fhtml_bit%2Fb-charger.htm&lp=de_en&tt=url

Basically this guy has gotten the datasheet from maxim and put in the values for the resistors where needed based on the attributes of the Bit-CharG batteries.

He has made two chargers actually. One circuit is for charging a NiMH battery, the other circuit is for charging a NiCd battery. You can build either circuit, you don’t need to build both. Each circuit is based on a different charging chip, either the MAX713 or MAX712 respectively.

I’ve got some of these chips from maxim-ic just as Ads says above as free samples. I’ve yet to put a test circuit together, just too little time and too many projects…….

This is the circuit form the german page:

Looking at it closely everything is stock, ie: the same from the datasheets EXCEPT where it is detailed in RED or GREEN, these are the vaules you need to calculate based on the capacity (mAh) of the battery and how many batteries you would be charging, ie: single, dual/tri cells….

My only suggestion is that IDEALY you would need to put a switch in the car that takes the battery out of circuit (ie: disconnects it from the PCB) when it’s being charged. Otherwise you would have some current going into the circuit which would (theoretically) put the sensing circuit on the maxim chips off a bit. I dunno for sure, this is just my thoughts…..

ph2t.

Edited by – ph2t on 02 February 2004 13:30:48

[matic]

Quote:

Otherwise you would have some current going into the circuit which would (theoretically) put the sensing circuit on the maxim chips off a bit. I dunno for sure, this is just my thoughts…..

ph2t.

I dont think that PCB could affect the sensing circuit because circuit only checks the voltage of the battery… Or maybe I`m wrong, lets wait and see if some expert answers this…

[Ads]

Ph2t, yep back in the hood!

The beauty of the MAX712/713 is they supply the batteries load as well as charging the batt!! So this chip is perfect for the bit-chars or any other batt that needs to be charged in situ. I have all the R values at home for 50mAh Nicad, 150mAh NiMH, 200mAh NiMH charged at a “safe” rate and all pin connections if you want them. (they may be the same as in the schematic above….just don’t know them off the top of my head.)

I too have to find time to finish this project (I have the board printed ready for etching). Will hopefully have done by next week and let you know how it goes.

Pretty damn cheap DeltaV charger if you ask me. Those chips go for $30ea from RS I think too.

[ph2t]

Cool man, let us know those values, you charging at 2C?

ph2t.

[Ads]

Ok. All of these relate to the schematic on the MAX712/713 Data sheet!

At I_fast = 200mA (4C for 50mAh, 2C for 100mAh, 1C for 200mAh)

For the number of cells:
No of Cells : PGM1 : PGM0
1 : V+ : V+
2 : open : V+
3 : Ref : V+
4 : Batt- : V+

So from this you can setup a 4pole switch between PGM1 and the options.

For a timeout of 66mins, with deltaV termination; Leave PGM3 open and tie PGM2 to V+

The power disipation of the transistor = 2.16W

To choose a value for R1 use:
R1 = (min transformer voltage – 5V)/0.01
R1 = 800R to 1k2 if using a 12v transformer.

R_sense = 0.25/I_fast = 1.25R

All this should make sense I hope. Any Q’s ask.:D

[matic]

Ads, can you send me board picture and R values by e-mail plz?

[Ads]

Once I get Protel reloaded in the computer (Had a virus and had to format my HD!) I will send you the PCB diagram. You at least give me an excuse to get on with the job and finish what I started:smiley2:

[matic]

:):):)

[matic]

Just a question: Max712 is for NiMh ONLY and Max713 is for NiCd ONLY ?

If you look at this link
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1666/ln/en

From here MAX713 can be used for BOTH types of battery.

Anyone knows for sure?

[ph2t]

Depends on the charge rate of C. If you look at the data sheet it says that at or below a charge rate of 2C you can use the MAX713 for both types…….. There’s a table on one of the pages, can’t remember which, sorry……..

ph2t.

[matic]

Thanx Ph2t,I know about those tables but I don`t really understand the meaning of the 2c, 4c or c/2. I build a circuit exactly following the above scheme, adding two LEDs for power and charge (connected to DCin / V+ and V+ / FASTCHG)using 9v adapter, 1/2 ohm Rsense 390 Ohm R1,but that thing doesnt work like it should. Current is sometimes low like 200 mA sometimes over 1A. charge LED goes on and of, sometimes fast sometimes slow, and a slope temination never occurs.

Obviously something is wrong, so I`ll be very gratefull if someone can tell me the values of R1 and Rsense for charging 1-2 batteries at cca 700 mA
…or any other tips will be appreciated…

Edited by – matic on 13 March 2004 21:49:38

[matic]

Anyone?

[ph2t]

dude, let me look into it tomorrow. I want to build this now as I kinda need a proper charger for my madforce……

cheers,

ph2t.

[matic]

sorry for being so unpatient but this thing bothers me a couple of days now… You know how it is…
And one more thing; shouldn`t R4 be 22k not 33k ?

[matic]

sorry for being so unpatient but this thing bothers me a couple of days now… You know how it is…
And one more thing; shouldn`t R4 be 22k not 33k ?

[Author]

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