Charging cell using rc charger, voltage jumps, is it normal?

i am using HTRC b6 v2 (very similar to imax charger) keep me posted on you results.

 

Are you chargin

First your google doc access settings need to be changed so we can see the data you posted. Currently only says "request access."

Are you charging an individual module or two modules together as a block when you get this 16v reading?

If it's just one 8v module giving a 16v reading when charging that's what I've seen from modules that have failed. But if it's two modules charged as a block, than that's normal.

 

First, I think you're starting the cycle from the incorrect menu. That's why it's starting with the charge.
You need to press the forward arrow a couple more times to get to the "NiMH Cycle" screen. Make it show D->C, set your charge amps, discharge amps and number of cycles desired. Then hold the start button for a couple seconds until it beeps and the cycle will start.

Second, if you watch the video, the charger is trying to obtain the programmed 5 amp goals. It's going to go to whatever voltage it needs to, to overcome any resistance on the wires or module. Small gauge wires have high resistance. Bad modules have high resistance. Any combo of the above has high resistance.

It's using the high voltage to get the charge rate, (it hit 4.6 amps) which is about 1.3 mAh per second. It looks like your mAh counter is increasing at about that rate, so that makes sense. While in the charging sequence, the charger will frequently drop to 0 amps to check "delta V" to see if the charge is complete. During this time, the mAh counter will stop increasing, because the charge rate is reduced to zero. Notice, when the voltage drops to 7, your mAh counter no longer is increasing. It's merely monitoring the module voltage, not applying charge voltage, to see if the charge is complete.

 

If it does this for every module, then I would look at getting heavier gauge wires for charging or lower the amps to 2ish to see what happens.

If it's only doing this on some modules, I would say those modules are no good due to having significant internal resistance.

 

Hey, I believe I had a similar experience with a Venom pro quad charger. It's basically the same as all the other 4 button chargers, display looks identical.

I saw numbers up to around 9.5v when charging. And it usually hit my cutoff (7200mAh) instead of turning off via Delta peak.

As soon as charger was disconnected, I saw numbers drop to about 8.2-8.5v. I do recall seeing slightly lower numbers on my volt meter when charging vs the charger display.

Someone in another thread suggested that maybe the charger isn't calibrated correctly. But I'm not sure about that.

I eventually decided it probably isn't anything to worry about. A 12v battery charges around 14-15v, so a 7.2v battery charging around 9-10v shouldn't be that big of a deal. A 12v charges at 14 to bring the charge voltage up to about 13, so what we are seeing I think is normal. Charge voltage of 9-10 to bring battery charge voltage up to 8.5 or so.

I've read quite a few posts saying that these batteries don't produce a great Delta peak, so the auto shutoff on these chargers doesn't work well with them. I know mine didn't.

I did find that if I charged at lower amperage (2 amp or so), it was less likely to hit the Delta peak, if I charged at 5 amp, it would hit it more often. But even then it was probably only 1 in every 5 charge cycles.

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A test meter attached to the battery, while be charged, will let you know EXACTLY what is going on.

 

Voltmeter on the battery should be the accurate reading. The charger reading must be off. Charging a "good" module at 6.5a, the voltage does not exceed 9.25v

 

Did the IMax 6BAC (50 watt) charger rebalance your modules without damaging them? Between the concern you raised and a different thread said a 50 watt charger would not work and that an 80 watt charger was needed for Prius modules, I thought I'd check before buying the charger. Thanks, Gerry

 

Imax are great for charging up individual modules and most Prius have 28 total modules. However methods to balance all 28 modules with exact same voltage don't work very well because it requires you to divide that 50watts or 80watts by 28 different modules after rewiring the pack in parallel.

For best results the balancing stage is best done with the pack wired up in its standard series as a high voltage pack that is then trickle charged with a high voltage charger. The prolong charger by hybrid automotive being the most sophisticated design.

 

Thanks. I'm hoping to use the smartphone software on the newest IMax 6BAC to do several modules a day. How long does it take to run 3 - 5 cycles on the IMax 6BCA?

 

The discharge is only 10watts on IMAX so it's very, very slow... I prefer to use cheap 12v-20w and 12v-50w halogen bulbs...

I start out with both of them at 70w total discharge per module and then back off on the wattage as the charge goes down. I've been told and tend to agree that this is cheating and not as thorough as an optimum 250ma discharge, but it allows me to discharge a module in less than an hour, which is similar to amount of time it takes to charge it back up.

And to speed things up even further, I have seven discharge systems and seven charging systems... But it's super primitive compared to my buddy in Oregon who has $30K in lab grade gear and he can work on up to 80 modules simultaneously if he wants. You get what you pay for I guess?

Anyways, here's what my latest rack looks like:

 

Hi there, i just got one of these chargers and i wanted to know what is the capacity limit that you put on the modules to charge them? i need to know because i don't want to overcharge them. Thank you.

 

I use the the existing settings... Doesn't matter much when I've changed them... I just charge in NiMH mode at 3.4amps and monitor the voltage level and do the best I can to shut off the charger at 8.7v or so. I never leave it up to the machine to shut itself off correctly because it's not designed for cells as large as these. Fortunately they tend to shut down too soon, rather than too late...