You don’t “own” the thread Rick, if people want to discuss the issue, it’s their business.
It’s an interesting discussion, and we actually seem to have real experts discussing it.
I see that TOC and Michael have a lot to offer here in real experience that can be backed up with fact, so I’m all ears here.
Greg
Greg Elmassian said:
You don’t “own” the thread Rick, if people want to discuss the issue, it’s their business.
It’s an interesting discussion, and we actually seem to have real experts discussing it.
I see that TOC and Michael have a lot to offer here in real experience that can be backed up with fact, so I’m all ears here.
Greg
I agree. Learning a lot.
One thing that really needs to have more understanding/definition is “smart charger”.
The term is used all the time, but my idea of a smart charger is something that does a number of things “for” me, not just turns off at the end of a charge.
A charger that must have the chremistry, charge current, number of cells “input” is not very smart in my book.
Moreover, it seems to me, since I read virtually all posts on all forums, that many problems are caused by improper settings.
I still have a MAHA C777 Plus II that works perfectly and it at least varies charge current, duration, and charge voltage automagically.
I wish there was something that smart still available.
Greg
David Maynard said:
So the best solution, if possible/practical, would be to get one pack with twice the capacity of the packs in question. Then there is no parallel to worry about.
Am I right?
You are absolutely correct.
As the originator of this thread I will explain why I went with the parallel option.
Basically I could have used a 14.4V 5000mAH LiPo battery, but with all the negative press both on forums and on the net has made me LiPo shy, so I opted to go for NiMH which gave me only half the capacity of LiPo, so to get the extra capacity I paralleled them.
Also usin LiPo would have meant dismantling my loco every time I wanted to charge the battery as I would not be happy charging a LiPo in-situ.
That is what raised the question of charging.
Again I have seen so many different opinions both on forums and the net that I am none the wiser, but separate charging seems to be the preferred method.
As for thermostats I have no idea if the cells have them or not. Frankly I had never heard of them being fitted to batteries till this thread.
Duplicate post removed
Hi Graeme, now I see your issue. Did you contact Tony at RCS in Casino, NSW to inquire about the Battery Install Kit? We use it here in the states and this enables you to charge your battery inside the loco. I have been selling this part for 24 years and it is the best kept secret for some reason. Tony has it listed for $33 AUS.
Don
RCS of New England, USA
TOC has suggested the simplest method.
Two packs feeding into a DPDT selector switch. Switch could even be centre off if you wished.
Charge each pack separately via the one charge socket. The switch steers both charge and run to each pack.
I agree… there’s a compelling reason to do it this way, it really depends on how “smart” your charger is.
If your charger terminates charge based on the DV/DT method, diodes should not matter in proper charge termination.
I do believe though, that if you are charging 2 battery packs in parallel, you should have diodes on both, and you should have the charge current limited so if all the charge current goes to one pack, you are not exceeding the charging specifications. This would happen if one pack developed an open, for example.
But if your charger stops charging based on terminl voltage, the diode drop will prematurely terminate charge, because the pack will actually be 0.7 volts under the target voltage.
Using a switch to select one pack at a time has no such diode drop, and works well.
Regards, Greg
Greg.
The other circuit using diodes to prevent back feeding has the charging ports between the battery pack and the diode. The diodes have no bearing on the charging.
That works well as the system automatically takes whatever pack has the highest voltage. However there is the expense and complication of the extra charging jack and wiring.
Greg Elmassian said:
I wish there was something that smart still available.
Greg
I don’t know how well it compares with what you need, but versions of this are still available. Charges numerous chemistries . It works for me.
"I still have a MAHA C777 Plus II that works perfectly and it at least varies charge current, duration, and charge voltage automagically.
I wish there was something that smart still available."
Does that Tenergy vary charging current as it charges, or do you have to set it?
does it automatically determine the number of cells in the pack?
Thos are some to the things I wanted.
If so, please post the model number.
Thanks John,
Greg
Greg Elmassian said:
I still have a MAHA C777 Plus II that works perfectly and it at least varies charge current, duration, and charge voltage automagically.
I wish there was something that smart still available.
Greg
If you are talking about NiMH, or even NiCad, have you tried to make your own using the Maxim chip? I made one for my NiCad pack using that chip and it allows for charging of up to 19.2 volt packs (16 cells), but you needed to set it up for the number of cells desired. This was long ago so maybe they can even do 24 volt packs with “self-realization” now.
Greg Elmassian said:
"I still have a MAHA C777 Plus II that works perfectly and it at least varies charge current, duration, and charge voltage automagically.
I wish there was something that smart still available."
Does that Tenergy vary charging current as it charges, or do you have to set it?
does it automatically determine the number of cells in the pack?
Thos are some to the things I wanted.
If so, please post the model number.
Thanks John,
Greg
You need to set the maximum charge current and number of cells. I believe it does charge in stages varying the current as it goes. At least that’s what the front panel display indicates. Specs and Manual are in Chinglish so nothing is certain. It does have memory pre-sets so you only need to figure that out once. It is smart enough to verify the cell count (by voltage sense) before starting the charge and will abort if voltage is not withing range for the cell count. It also has a max charge timer that you can set for an additional safety margin.
My smart charger, a Park Flier, senses the number of cells, and switches to trickle charge when the unit senses that the cells are charged. All I have to do is set the max current for charging (with a knob). It also has a switch so I can set it for NiCad or NiMh. I believe that is what Greg is saying he would like, a unit that varies the charge currents and senses cell numbers automatically.
I have a charger that seems to have the same programming as the Tenergy charger. When charging LiIon batteries, the charger initially charges at the current level that you set. As the batteries begin to reach full charge, the current reduces to a much lower current. When the charger senses that the battery is full, the charger drops to a state that inficates the battery is full.
Interesting, I see a term I was not really familiar with from the old days: “peak charging”… apparently instead of using the 2 different methods of peak charge detection (negative dv/dt on nicad and zero dv/dt on nimih), they just watch for the peak voltage… which should be fine, maybe a bit early on nicads.
Is this what you guys understand “peak charging” to be?
Greg
My brain hurts reading all of this…but it is interesting so I’m going to keep going, going, going…just like the Energizer Bunny.
Thanks to all of you for your expertise!!
Richard
I don’t know why you guys don’t just make your own using a Maxim chip for a few dollars and some other components. They have chips for charging whatever with all kinds of detection/limiting.
When I put the on-board TE in my FA, I made my own charger using a Maxim chip, and that was for just one train.
Todd
The Maxim chips are GREAT, suit multiple needs, plentiful, inexpensive and robust. BUT not everyone likes to work with electronic projects. So the rest of the world just spends there money for instant gratification or not…
Michael
Greg Elmassian said:
Interesting, I see a term I was not really familiar with from the old days: “peak charging”… apparently instead of using the 2 different methods of peak charge detection (negative dv/dt on nicad and zero dv/dt on nimih), they just watch for the peak voltage… which should be fine, maybe a bit early on nicads.
Is this what you guys understand “peak charging” to be?
Greg
Greg,
Far as I know; peak charging is synonymous with dV/dt and or dT/dt charge algorithm’s. Either reaches a peak and terminates charge.
-dV/dt is best for NiCD’s, but can be problematic with NiMH yet is widely utilized and REQUIRES a NiMH peak charger… Intelligent micro-processor based chargers utilize said algorithms with additional gates i.e., timers, voltage plateaus. temperature thresholds, slopes and more, thus mitigating the problematic issues with NiMH (false peaking/over charging).
Additional thoughts:
Smart charger refers to a charger that communicates with a smart battery. A “smart” or IC equipped battery at the very least identifies itself, its cells individually and suggests what algorithm to put to work. Lithium technology based chargers typically known as balance chargers are close as at it gets in our world to the best of my knowledge.
-dV/dt refers to the rate of change of voltage over time charging algorithm. As a Nickel battery is charged at constant current, the voltage increases, reaches a peak, thereafter the voltage dips slightly and charge terminates. So the charging circuitry looks at the rate of change of the voltage (or simply the change in voltage). When charging voltage starts to decrease, charging is finished.
dT/dt refers to the positive rate of change of temperature over time charging algorithm. An ancillary thermistor/sensor/probe is required and placed against the cells. Nickel batteries are charged at a constant current continuing all the way to charge termination. As the voltage increases (possibly even reaching a peak) and once the temperature threshold is reached the charge is terminated. The charging circuitry looks at the rate of change of the temperature (or simply the change in temperature).
CC/CV refers to a constant current, constant voltage charging algorithm. Charging begins with providing constant current to the battery, once the specified battery voltage is reached, charging switches over to constant voltage, topping off the battery. When the battery is topped off at a constant voltage, the charging current decreases as the battery is charged until it drops to a sufficiently low value and times out and or a voltage specification is reached and charge is terminated. All Lithium based chemistries must be charged in this manner, including LiFePO4 cells.
Lead acid batteries also charge by constant current, constant voltage.
Generally speaking all the aforementioned charge algorithms would work in harmony with a time-out (timer) safety function to limit MAX time under charge… These timers are often set for a default value; chemistry dependent, but often can be programmed to user defined parameters.
Michael