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Old 08-19-2005, 02:02 PM   #1
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Lightbulb NEW LiPo Prototype Battery Charger Questions.

Hi Guys,

I work for a company called Innovative Circuit Technology LTD., and we are an established manufacturer of general and industrial use power supplies, power conversion and charging products. The bulk of our offerings are available to view at www.ICT-Power.com or http://www.ictcorporate.com.

We have recently looked at diversifying into alternate markets due to internal interest from some of our design and sales staff, and one we’ve all agreed on is the hobby charging market, and more specifically, charging Lipo batteries. As it stands right now we have a working charger that is moving through the prototyping phase, but as I took a look at the market research I was surprised to see that we had previously perhaps overlooked some of the features end users may want. The things we’ve included to this point are as follows:

- Graphical White Backlit LCD ( 128x64 )
- 1mA Charge current steps
- The ability to charge up to an 8 cell pack
- USB output with PC software that can program new charge profiles, load included profiles ( 10 at this time ) and store graphical data
- Rotary Encoder for menu selection, and perhaps 1-2 other buttons
- Charge(8A)/Discharge (3A)/Storage Charge (50%)/Cycle
- Temperature Sensor
- Fan Cooling
- Dynamic graphing, so you can view extremely detailed sections of a charge, or see the entire graph profile in lesser detail


Reading through various forums I’ve noticed a trend toward end users actually modifying multi-cell LiPo packs to be able to charge the individual cells to more precise voltage levels. As we are still in the design phase, I want to get an idea of whether a charger that has multiple outputs is of great interest or not. We are looking at leaving our main output able to charge up to an 8 cell standard pack, but also adding 1-5 depending on size restraints and costs, individual outputs capable of only charging a 1-2 cell pack. This would give our unit the ability to charge not only the person who buys an 8 cell pack and wants a good efficient and effective charge, but also the enthusiast who wants to modify his pack and charge the cells individually, without having to buy multiple chargers. The limitation would be the additional outputs would only be able to do 1 or at most 2 cells at a time, so you couldn’t hookup 5, 4 cell lipo packs to the unit. We are trying to release a product into a market where there are established manufacturers already, but as our namesake indicates, we’d also like to try and be able to give a charger that has some features not readily available yet.

Any thoughts on what you’d be willing to sacrifice in terms of size and cost to achieve something like this, and any features that are overlooked in not only our prototype, but current production chargers is greatly appreciated. Other forums for us to work with would also be good points.

Ryan Kennedy
ICT, Engineering


Last edited by ICT-POWER.COM; 08-19-2005 at 03:57 PM.
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Old 08-19-2005, 02:34 PM   #2
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I like the idea, and you'll probably find yourself more input on an Airplane forum, since that's where most of the Li-Po stuff is right now. RC Universe has a pretty good sized RC plane forum, you might want to check there.
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Old 08-19-2005, 02:47 PM   #3
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Again a place like rcuniverse has more airplane ppl. Although being into electric planes myself, and also working at a hobby shop i have a little input.
I really like a lot of the features that are listed, i like the ability to charge 8 cells at once. I dont know of any chargers that do that right now, then again i dont need anything that big. If the price of the charger is under 200.00 there will be a much better chance of it getting sold. Working at my LHS i have noticed that it is very hard to sell the chargers that are really big $$. Also giving it the ability to charge Nicd and NiMH batteries will open the market up to the electric guys as well.
Keep us updated though i would like to see some pics and more specs when its done.
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Old 08-19-2005, 03:04 PM   #4
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Default Thanks....

for the input.

I wanted to post here as well, because while we are focusing on the LiPo side, this charger will be able to charge NiMH and NiCd as well once its finished. It won't have motor warmers in it, and the curve's might not be as advanced, but the functionality will be there.

I'll post up as it moves along, and I also didn't mention, but it should have auto-cell count on the LiPo side, which is very hard to program for effectively, but we think we should be able to do it.

Ryan Kennedy
ICT, Engineering
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Old 08-19-2005, 03:48 PM   #5
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Although the airplane market is more into Lipo we will see a steady growth in the car market so it's great to see your interest here.

-Lipo's are starting to get used to power transmitters and receivers/ servos, but is not used much to actually power the electric cars (yet!)

-I do not see individual cell charging as important as being able to balance the cells in the pack. I would guess the difference in cost is high, but if not it would be a cool feature.

-I do not think the auto-cell count is a good idea. The risk is too high.

-The maximum charge current should be 5A or more. 3A is not enough for the high end unit you are describing

-The temperature sensor is a good idea.
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Old 08-19-2005, 03:57 PM   #6
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Default Updated

I updated the specs above to reflect this, but the Discharge current is limited to 3A, but the charge current available will be 8-10A for this unit.

The individual cell charging seems to be driven from the Airplane side of LiPo's where people are taking they're 2/3/4 cell packs, cutting them open, and adding smaller charge wires to charge the cells individually. This requires multiple chargers on the user's part, which hopefully we can help to avoid with this design.

The auto cell count is one of those things out there that when someone gets it to work properly, its going to put that product through the roof. We've only looked at that briefly, but will be putting it through extensive testing to see if it works correctly. If it doesn't, it will be left out of the design. I can see it being based on a couple of inputs the charger will get, and if over multiple readings it can't correctly decide if it a X number pack, it will stop and prompt the user to choose the correct number. This is only an issue on the output that can charge up to 8, deciding between 1 or 2 on the other outputs should be do-able.
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Old 08-19-2005, 04:09 PM   #7
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-I know more and more batteries are coming with wires attached to each cell, but as far as I know they are mostly used to balance the cell voltage (with a charger or a dedicated device), and not actually charge the cells individualy.
Charging them individualy is probably even better, and if it does not make the charger (much) more expensive you should do it.

-The way you now describe the auto-cell count and software setup it should be very good!
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Old 08-19-2005, 10:19 PM   #8
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for nimh cells heres what the best CHARGERS(not worrying about discharge/motor run/whatever) should have imo

vitally important
  • temperature sensor, to be used as a cutoff.
  • ability to have 3 (maybe more, but 3 prolly is fine) charge stages. this is very important as we are trying to get our nimh packs to an operating temperature during the charge phase. something like this:

    1/3 2500mAh ,7.0A Flex no
    2/3 2530mAh, 0.2A Flex no
    3/3 3900mAh, 4.0A deltapeak 00, temp cut 47C
    Repeak 1 > Repeak delay 5:00 > Capacity limit 300mAh

    with x/3 being each of the 3 stages. as you can see high current to build charge, then slowlly continue filling cell up so as not to build heat, then final stage finalizes charge and builds operating temperature....then repeak maintains temperature.

nice for usability
  • nice display
  • ability to alter charge current during charge (so you can compensate for starting pack too early or too late

i think the only things you dont have are stages, and altering charge current during charge.

also on the note of cost at least for cars, features related to computer connection are of less importance than most all other features, simply because most racers wont have pc's with them at races. i am by no means saying that they arent useful, just practicality for the majority of users probably isnt there.

honestly for the model of necesary nimh charger features, i'd recommend looking at Team Much-More, CTX charger. it really has all the features needed by world class professionals, mainly because its used by the best drivers in the electric car world! but that doesnt mean that it is as good as it could be!

i look forward to seeing your product!

Last edited by floodo1; 08-20-2005 at 02:31 AM.
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Old 08-22-2005, 04:21 PM   #9
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Default More good input

Thanks guys. I've also posted this as recommended over at RC universe and RC Groups.

We've been looking at all the responses thus far and it been very helpful. For this first prototype it will most likely be strictly LiPo as the NiMH and NiCD markets are pretty saturated with chargers already, and coming in as a new company would be difficult.

We are looking at perhaps being able to charge two seperate 5-6 cell batteries simultaneously as a starting point, giving people with multiple packs a way of charging them more quickly than is currently available through a single charger.

Keep the ideas coming,

Thanks
Ryan
ICT, Engineering
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Old 08-22-2005, 04:40 PM   #10
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just to let you know there are a couple of chargers (ni-mh) that can charge more than one pack of 6 cells simultaneously.

Dont know if you were talking about Ni-Mh or Li-Po though.
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Old 08-23-2005, 02:24 AM   #11
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I have been running Lipo's in a CW Sprinter since April... 10T x 2 motor... My Lipo's I have been testing 7.4 volts at 4900 mah, six cell packs. They have power equal to if not better than GP3300's and a lot longer run-time.

Due to the rumors/experiences of my airplane buds these batteries like to catch fire, blow up and other wild things. Mostly because the batteries are being pushed beyond specs.

I have been using the Duratrax Ice Machine and have had no problems with the batteries getting hot during charging. Only warming slightly under hard use ... and not as warm as 3300's ... they do get a little warm when run down to their minimum voltage limits with a hard load. The batteries are 6 ounces lighter than 3300's I have found no need to bump them like you do NiCads and Nimh's even after sitting for 2 weeks, they really hold their charge. Loosing 6 ounces in your car is a big plus!

Since Lipo's have not been approved by the sanctioning bodies... I don't know how they would do in a real tough race. But they do pretty good here, for me racing on a weekly basis. I win with them quite frequently... but have been advised not to use them when the point season starts...

Getting back to it:

Your charger will need a temperature sensor as not to overheat the battery during charging. Max suggest temp is 95 degrees F. Also need a "Fail Safe", when the charger is set for Lipo's, Temp probe must be used, charge cannot exceed, __ C of the battery rate, etc.... Something I inadvertantly did one night was to select the wrong Lipo Charging program... the Ice Machine was able to "know" this and stopped the process..

To be honest the Ice Machine has it all about covered for an average guy to use Lipo's as long as he explicately follows instructions. Immulate them and improve on it, keep the $$ reasonable. Put in a back light... My pit buddies have gotten use to the batteries and see that not all the rumors are true. We are quite comfortable with them in the pits...

Being here in Arizona, it is just plain hot... temperature outside seems to be above 95 degrees most of the time..LOL.. a built in battery cooler would be the "cats meow". After use, I have had to put them in the freezer to get them down to a temperature that they can be charged again and used for later heats. Lipo's don't heat up much under normal charging...but, here, they are slow to cool! In April when it was cold, I put them in a heating pad to warm them up before use... they perform different with a little heat in them....right at 95 degrees F. BTW these batteries always have set in my home-made cooler when they are being charged.... a 4 inch fan blows directly across them on 3 sides...

At this point in time of my testing, I see no need to cut them apart and charge each cell individually... as I see it Lipo's are not physically strong due to their construction, the "foil" bags, and pos/neg tabs welded together... and wrapped in shrink wrap, leads coming out from the center (weak area) and won't take much physical abuse.

Lastly, I am not too concerned about graphs and computer stuff when running two or more classes on race night. I just need to be sure my chargers charge and do and as I expect ... the fluff would be nice at a time when I have the time to check batteries elsewhere... but I also don't want an information overload.

Hope this helps...
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Old 08-23-2005, 03:38 AM   #12
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Is LiPo technology matured yet ? I heard possible of fire hazard if LiPo get charge at wrong amps or being overcharge.

BTW, I vote Li Po for RC future. Soon EP cars could run with fuel cell and run 1hr until next charging.... awesome dude!!
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Old 08-23-2005, 03:41 AM   #13
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Quote:
Originally Posted by ICT-POWER.COM
Hi Guys,

- Graphical White Backlit LCD ( 128x64 )
- 1mA Charge current steps
- The ability to charge up to an 8 cell pack
- USB output with PC software that can program new charge profiles, load included profiles ( 10 at this time ) and store graphical data
- Rotary Encoder for menu selection, and perhaps 1-2 other buttons
- Charge(8A)/Discharge (3A)/Storage Charge (50%)/Cycle
- Temperature Sensor
- Fan Cooling
- Dynamic graphing, so you can view extremely detailed sections of a charge, or see the entire graph profile in lesser detail
I'm not much of a LiPo user yet. But I have opinions.
I like the feature list. I'd like to see higher discharge, maybe as an addon unit. You can make 10/20/30 Amp dumb "load unit" that is controlled by the charger. When the unit is plugged in you can discharge up to 30 Amps, without it you can discharge 3 Amps.
There has to be motor run feature. I'd like one where you can adjust both the voltage and the current, like in high quality power supply. Lets say I want the high quality power supply control, that can run motors, built into the charger.
There has to be NiMh and NiCd charging.
The Kiss principle is always good. That is; take great care in keeping the charger simple to use. I'm always annoyed when I have to read a 100 page manual to adjust my radio endpoints.
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Old 08-23-2005, 06:42 AM   #14
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Quote:
Originally Posted by asw7576
BTW, I vote Li Po for RC future. Soon EP cars could run with fuel cell and run 1hr until next charging.... awesome dude!!

Man fuel cell are not rechargeable ... you need fuel for get electricity.

... somewhere in the east (guess taiwan) they just discover a new sort of fuel cell that work fine with urine ... so just piss on the cell and you get power ....

e_lm_70

PS: The pissing cell it is designed for medical tools where only one drop of piss is enough for make a single test in a portable device ...
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Old 08-23-2005, 06:51 AM   #15
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Quote:
Originally Posted by ICT-POWER.COM
Thanks guys. I've also posted this as recommended over at RC universe and RC Groups.

We've been looking at all the responses thus far and it been very helpful. For this first prototype it will most likely be strictly LiPo as the NiMH and NiCD markets are pretty saturated with chargers already, and coming in as a new company would be difficult.

We are looking at perhaps being able to charge two seperate 5-6 cell batteries simultaneously as a starting point, giving people with multiple packs a way of charging them more quickly than is currently available through a single charger.

Keep the ideas coming,

Thanks
Ryan
ICT, Engineering
Man you are right about charger for RC CAR ... and LiPo is still used by 0.1% RC Car people ...

But also for Lipo ... I don't see the advantage to allow multiple charging in the same time ... actually there are already nice products for properly balance multiple lipo cells ... like Schulze Lipo balance unit.

So it is going to be an hard time to find the right market area ...

e_lm_70

PS: About new opportunity with multiple parallel charging I just see the side-by-side battery used for Cars ... charging and discharging all the 4/6 NiMh cell independently without disassamble the pack... in this area there is still no product on the market

P.S: In the LiPo arena now relative good charged can be found for around 50$ ... and with 100$ you get already the ICE ... and for profy with the need to balance the Lipo, they mainly need to be fiendly with the LiPo tabs ... so the schulze offer for 80$ it is already the state of art for charge safaly a xS Lipo pack !!!
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