I’m appealing to the guru’s for some help. I just soldered together 6 AA batteries to make a 7.2 volt pack for the R/C in My live steam project. I have a fancy Passport Ultralite 50W charger that I don’t entirely know how I should use. I can select that I want NIMH. It then has a default charge rate of 1 amp. Is this correct for this size Pack? What setting should I use? I believe once I have I have this correct I should be able to move right on to the actual charging. Any help is appreciated. Obviously I’m in over my head.
1 amp sounds a bit high. it would help if we knew the MAH rating of the batteries. the charge rate is usually based on the amp hour rating of the batteries.
OK, I went and gave the batteries a look over and… Survey says, 2600mAH.
If they are good cells and you have a smart charger, you can charge close to 1C, which is 2.6 amps, but few cells are built for this, mostly drill batteries, and also the life is shortened.
1/2C is normally fine, which is 1.3 amps. So try your one amp charger on DISCHARGED cells and see how warm they get. They should get just a little warm, never so warm that you don’t want to touch them.
Greg
Stop! First, we need to find out who manufactured the AA cells you have, are they customer brand button top or industrial grade flat top? Because, each manufacturer has a data sheet that tells you what the charge and discharge rate is of their cell and each cell is different.
So, who is the manufacturer of the cell (Sanyo, Tenergy, Panasonic) and is there a part number on the cell like: HR-AAU or 10306?
If I can get a little more information I can tell you how many milliamps to charge your pack.
Thanks,
Rick Isard
Cordless Renovations, LLC
I understand that it’s almost impossible for an automatic charger to charge nimh at .3C and below. I said .5C would be fine, 1 amp is .38C, sure seems more than safe.
So Rick, what current do you recommend in general for a 2.6 amp hour battery?
Greg
The batteries are Powerizer that I got from Batteryspace.com. They have sat almost a year though and I’m afraid they are probably shot any way so we will see when I get home tonight. Thanks guys I really appreciate the help. I’m not sure if I can select the charging voltage but I assume it should be about 7.6 for my 7.2 volt pack?
I looked at the manual, it seems all that you can do is set the max charging current, the voltage is adjusted automatically, i.e. it apparently senses the number of cells in series.
Your 7.2 volt pack has 6 cells in series (or a combination of 6 paralleled sets in series), so the nominal voltage of each cell is 1.2 volts (which checks).
minimum charging voltage is usually 1.4 volts per cell, which would be 8.4 volts, but again, let the charger do the work for you.
You DO have the manual, right?
Greg
Thanks for all the help Greg. This all sound good. I do have the “manual”, just one large sheet, but I didn’t see anything about it auto setting the charging voltage. Granted I probably did not read it all as thoroughly as I could have. I’ll report back on how every thing goes tonight. Thanks again guys!
No, there is no way you can set the voltage yourself, thus the system MUST choose the charging voltage itself.
Since you do input the battery chemistry (type of battery), it knows the nominal voltage for a cell… by applying some current and then checking the voltage, it can determine the number of cells, and select the appropriate voltage which is most important near the end of the charge. Near the beginning of the charge, the current is most important, basically the voltage to achieve the proper charging current is irrelevant (unless it is way out of whack)…
So you can set the chemistry and (apparently) the max charge current.
There is a section for each battery chemistry. Seems like a pretty nice charger, is equipped for many different chemistries.
Greg
I have a Park Flyer charger, and I can set the current, battery type, but not voltage. Mine also will do a “trickle charge” when first turned on. For completely flat batteries, you may want to trickle charge them a bit, so the charger can sense what voltage the pack should be. If your charger has that feature. My charger will not work on packs below 6 volts.
Plugged in and charging away! Ive just went and checked and they are up to 1990 mAH . They were dead flat when I started. It started out at 7.9V and is at 9.1 120 minutes in. Next I’ll run the break in sequence in the battery instructions, and get the pack tidyed up and wrapped.
I just looked at their data sheet and it say’s you can charge these cells at 2.6 amps per hour. I would not. Those are customer grade button top cells and I’ve never come across a AA Nimh cell that could charge over 1.5 amps and last for 500 cycles. If I were you and to prolong the life of these cells, I would charge them at 500 milliamps per hour.
Rick Isard
Cordless Renovations, LLC
RCS America