ob1n

My Feedback: (14)

Ok....I have a "method" or "process" of charging that has worked for me for a long, long time!!! However, I now have newer peak chargers and they do not trickle charge like my old "timer" charger. Plus, I've been reading all about these "wall mart" chargers and how to hook them up to a 24 hour timer. Is there some "tech formulas/equations" for charging batts if I were to use wall mart chargers? I have 7.2v 1500 and 1800 Nicds. I found some old wall chargers and here is what they say..... 1) 9v DC 600mA 2) 9v DC 200mA Those are the ones that I have found, but what if I found another....like a 12v or 10v or something like that. I would guess that the formulas will answer that......correct?

JNorton

My Feedback: (2)

Divide the charge current into the pack capacity to get hours. Add 40% www.rcbatteryclinic.com Red has a good article on modifying wall warts.
Be aware some wall warts are power supplies meaning they have good voltage regulation, other were design as constant current chargers. You only want to use the charger style as the transformer in it is designed to mimic constant current - poor voltage regulation.

The easiest way to tell the difference - what was it used for? Charging a Black and Decker screwdriver - Yes, or powering a set of satellite speaker for your PC - bad. I know I sound like a goofus but the darn things look the same. Make sure they say DC on it also, using an AC adapter is a really quick way to ruin packs.

Use an amp meter in series with the pack to monitor current levels your looking for something around C/10. Keep checking the temperature od the wall wart and the pack if either get hot you're in trouble.

John

Rodney

Mr. Norton gave you some good advice. Unfortunately, most wall warts are not very elite units (made as inexpensively as possible) and may be as simple as a half wave rectifier. Most are simple full wave rectifiers with no filtering so put out a pulsing DC voltage which, when open circuit, provide quite a bit higher peak voltage than the battery being charged. They depend on the internal resistance of the transformer windings to limit the current. That is why they always get warm when you use them. Also, the current measured with a normal ammeter will not read the true current flowing because of the high ripple content. The only way to be sure of the current is to use a true RMS meter or an oscilloscope to monitor the output.

richrd

As John stated you can use those cheap chargers BUT ! you must correctly test them with a meter to verify one that it does output a direct current voltage, two that it exceeds the final charge voltage app. 1.45V per cell and third doesn’t exceed C/10 current unless you are willing to watch the charge the whole time. Next connect it up with amp meter in series plug in and verify C/10 then set back and wait, check if wall charger not getting to warm. The first time I check every hour the current and voltage until done, that it did not over charge by exceeding Vpk and that battery or wall charger did not get to warm. Then tag the charger with a note on what battery it’s good for.

ob1n

My Feedback: (14)

ok guys....I hooked my 7.2v 1500mah pack to the 9v 600mA wall charger. When I checked the voltage of the wall charger BEFORE attaching it to anything....the DC voltage was a constant 13.65v. Ok....then I attached it to my batt and ran my DVOM in series to check the current. At first, it read about 325mA and would bounce around from 322mA to 327mA. It has been charging for a while now...and the wall charger is barely warm(a good sign) and the batt has finally raised about room temp a little. It is currently running at approx. 520mA....therefore, I am correct to believe that if it reaches 600mA(the max capacity of the charger) that it is done?!?!!! Of course, I'll be closely monitoring the temp....but would this be a good indication? Thanks for your time, fellas. Laters.

JNorton

My Feedback: (2)

One other thing to note. If you do use a power supply wart wart instead of a current supply the wall wart will get "really" hot!. If you are unsure put a fuse in series with the wall wart about twice the value you expect to charge with or slightly higher than the rated output of the wall wart whichever is lower.

Rodney's right about the accuracy but its still within about 10% at least it gives you an idea. Richard's right about testing it for DC voltage first also, though I usually just look on the charger itself.

Have fun. It's not as complicated as we've made it sound.

John

ob1n

My Feedback: (14)

Ok ...thanks dudes....now....did ya happen to notice my 2nd post?

JNorton

My Feedback: (2)

Okay turn about fair play. Opps, but did you read my 1st post?

7.2v 1500mah pack to the 9v 600mA wall charger. 1500/600 = 2.5 hours. Now this is over a C/10 charge and you could easily over charge the pack using it. If you charge over C/10 you should use a delta/peak charger. You should try for a 150 mA charger for this pack.

John

richrd

NO NO ! Current and charge have no relation wall chargers will constantly output current until you pick little pieces off the walls[X(] if you excede C/10 and leave to long on charger. So your in the no sleep mode if you use this charger. Plot the voltage of the battery at C/2 you will see the delta peak at about 6*1.45 = 8.7 volts look at all the grafts out thier in cyber world, you must watch your battery period... you are over charging it with this wall charger to leave alone for 10 hrs ,, this is not a form charge. Guessing if dead to begin with and a good battery it's as said 2.5 hrs start to peak and get warmer and warmer...
Rich

ob1n

My Feedback: (14)

Ok.....C/10 and C/2 are confusing me....but I've now taken my brand new 7.2v 1800mah batt.....and hooked it up the 9v 200mA charger that I found. This is it's first charge.... I've watched the current flow for over 30-45 minutes...and it has read about 245-250mA. With this information, would it be correct to believe that I would charge this batt(watching it closely, of course) at this equation.....1800/250=7.2 hours....give or take a few minutes?!!??!! I also assume that 1.45 is max volts for each cell in your 6*1.45=8.7v equation.....correct?!!??! Is the C/10 meaning, for example..1800/10=180mA??!?!! And the C/2 meaning, for example..1800/2=900mA?!!! Thanks for your help, man. Laters

ob1n

My Feedback: (14)

wait a minute....C/10....Capacity/by HOURS= how many(theoretically) mA to charge with!!!....right?!!?? 1800/10=180mA......therefore(theoretically) it would take 10 hours to charge an 1800mah pack with 180mA?!!?? Correct?!!

Alfalfameister

In a perfect world, yes. But there are gross inefficiencies, that's why people say charge at C/10 for 14 to 16 hours (i.e., that's a 40% - 60% loss).

Is the Sirius Pro Former an "elite" unit? I'm thinking of ordering one (it's not the price that's bothering me; it's the price and hassle of shipping to the Philippines -- Well, that's why, if it's worth it, I'll go order two).

What kind is the Sirius Pro Former?

Do I have to do all of these testing stuff with the Sirius Pro Former, or can you guys just flat out recommend that Pro Former?

Bah! Engineers! I knew yous guys were good for something! Ha ha!

Cheers, fellas!

ob1n

My Feedback: (14)

Kumusta Ka Na Philipino!!!! I am married to a beautiful Filipina from Paranaque', Manila PI.....so cool.....are ya looking to get something from here in the states? We ship stuff home to Manila occasionally.

JNorton

My Feedback: (2)

The Pro former is a constant current charger. Dial it for a C/10 charge and in 14 to 16 hours the battery is charged. It's great for larger packs.
John

richrd

On the right track C is capacity in amps per hour so as current changes so does time.
C/10 is slow rate and very safe can leave on extra hours typ. 10hrs plus 2hrs for losses with out damageing the battery, it can save itself. Without getting technical. Thats why as you charge greater than C/10 current rate the battery charger (or you personally) must detect when done or you damage it. Vpk app. 1.45 is in the middle as charge changes do does everything else go figure[>:]

Hey I resemble that remark see true engnieeir cannnt splell
Rich

JNorton

My Feedback: (2)

Hey I resemble that remark too!