# Questions on Li batteries and charging



## wigginsn (Jan 9, 2008)

I'm getting close to converting another loco to battery and it seems like Li batts are the way to go. I already have a Li capable charger, an iMAX B5 which can do 1 to 5 cells and has a balance function built in. I've read up a bit and understand the benefits of the PCM cards that some have recommended.


First question is there a difference in the charging characteristics between Li ion and LiPo? My charger manual states "Li-ion/Polymer cell count: 1-5 cells" in the short specs, but in the Li charging detailed instructions say it should only be used for LiPo battery chemistries. Are they different or is this just a chinglish translation thing? 

Secondly does it matter which type I use? From looking online it seems most Li ion packs don't come with balance pigtails, but LiPo do. Don't Li ion need balancing? If so how do you do it?

Lastly, the charger manual says "don't attempt to charge a battery fitted with an integral charge circuit or a protection circuit." Anyone know why? Seems like that means I can't get a ready made pack with a PCM built in. Or should I just set the charger rate to lower than the PCM setting and just box on (aiming for 1C of course..)

All help appreciated.

Cheers
Neil


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## Del Tapparo (Jan 4, 2008)

Neil - I don't claim to be a battery expert of any kind, but here is my take on your questions:

It sounds like your charger is setup for LiPos only. If you intend to run LiPos. Most (but not all) LiPos are designed for the very high discharge rates used by R/C cars and park flyer airplanes. The balancing of cells becomes more important for those applications. If your battery pack doesn't have any protection circuitry built-in then you must be VERY careful not to over discharge or over charge the pack; this is where you hear all of the horror stories about lithium batteries (no protection). You can run Li-Pos in trains if you purchase a controller with a built in low battery warning/cutoff circuit. I believe my G-Scale Graphics RailBoss Plus is the only system on the market right now that offers that feature for large scale trains.


Personally, I would go with Lithium-Ion batteries (which have a built in protection board) and the appropriate charger. These chargers are only $25, they work well, and they are safe. I use All-Battery.com


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## Greg Elmassian (Jan 3, 2008)

What he said... basically you can design li-ion and li-po batteries the same... 

BUT 

For what the public "see" is as Del say, the li-po batteries that are most "common" to us, are the high current ones, which can take very high charging rates (and discharge rates)... 

What your charger company is trying to tell you is that the charger is made for high charge/discharge chemistries, so "normal rate" li-ion or li-poly batteries would most likely be damaged... 

Balancing is a technique to not only evenly charge each individual cell in a pack, but to help optimize charging and discharging capabilities. 

You don't see most "Consumer" li-ion packs with these features because they don't do the high rate stuff. 

If you were to tear apart a good quality laptop battery pack though, you would find many have the taps at each cell in a series setup... maybe more for safety and longer pack life than to optimize max current drain/charge. 

Anyway, it does not matter what you use, just get your charger matched to your battery. 

In my opinion, you will find that you never get something for nothing, i.e. getting a battery that charges faster will be offset by a battery that will not have as long life (total number of charge discharge cycles)... 

I would stick with more traditional, lower rate packs, and my opinion is that there is no need (nor long term cost advantage) to go to multi tap battery systems in our hobby. 

Regards, Greg


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## Michael Glavin (Jan 2, 2009)

Nope, current capabilities are not the variable………. 
The difference was/is the VOLTAGE rating of some Li-Ion (3.6V) cells as compared to Li-Poly (3.7V) cells. Many modern Li-Ion cells are rated at 3.7V. Accordingly a Lithium charge regimen utilizing the appropriate cell voltage is paramount for proper charging. If you have 3.6V cells due not charge with a 3.7V charger! Charging a 3.7V cell with a 3.6V charger will work, but the cell won’t fully charge… Do the math it adds up, 3.6(4)=14.4V, 3.7(4)=14.8V. 
See below for more in depth information copied from PowerStream’s website.[/i]
*Lithium Ion Charging*
Basics
These remarks apply equally to lithium ion and lithium polymer batteries. The chemistry is basically the same for the two types of batteries, so charging methods for lithium polymer batteries can be used for lithium-ion batteries.

Charging lithuim iron phosphate 3.2 volt cells is identical, but the constant voltage phase is limited to 3.65 volts.

The lithium ion battery is easy to charge. Charging safely is a more difficult. The basic algorithm is to charge at constant current (0.2 C to 0.7 C depending on manufacturer) until the battery reaches 4.2 Vpc (volts per cell), and hold the voltage at 4.2 volts until the charge current has dropped to 10% of the initial charge rate. The termination condition is the drop in charge current to 10%. The top charging voltage and the termination current varies slightly with the manufacturer.

However, a charge timer should be included for safety.

The charge cannot be terminated on a voltage. The capacity reached at 4.2 Volts per cell is only 40 to 70% of full capacity unless charged very slowly. For this reason you need to continue to charge until the current drops, and to terminate on the low current.

It is important to note that trickle charging is not acceptable for lithium batteries. The Li-ion chemistry cannot accept an overcharge without causing damage to the cell, possibly plating out lithium metal and becoming hazardous.

The question occasionally comes up "What is the effect of charging with less than 4.2 volts?" Unlike other battery chemistries the battery will charge, but it will never reach full charge, it will only be partly charged. The reason for this is that stuffing the ions into the anode or cathode crystals requires more voltage than the simple electrochemical cell voltage. The higher the voltage the more ions can be inserted. The page linked page here some quantitative data on the relative capacity of lithium-ion batteries that are charged below 4.2 volts. 


Charging Lithium ion batteries at slow rates

When the charge rate during the constant current phase is low, the charger process will spend less time during the constant voltage tail. If you charge below about 0.18 C, the cell is virtually full when the 4.2 volts is reached. This can be used as an alternative charge algorithm. Just charge below 0.18C constant current and terminate the charge when the voltage reaches 4.2 volts per cell.

Safety

Every lithium ion battery pack should have (must have?) a safety board which monitors the charge and discharge of the pack, and prevents dangerous things from happening. The specifications of these safety boards are dictated by the cell manufacture, and may include the following:
Reverse polarity protection Charge temperature--must not be charged when temperature is lower than 0° C or above 45° C. Charge current must not be too high, typically below 0.7 C. Discharge current protection to prevent damage due to short circuits. Charge voltage--a permanent fuse opens if too much voltage is applied to the battery terminals Overcharge protection--stops charge when voltage per cell rises above 4.30 volts. Overdischarge protection--stops discharge when battery voltage falls below 2.3 volts per cell (varies with manufacturer). A fuse opens if the battery is ever exposed to temperatures above 100° C. [/list] Michael


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## Greg Elmassian (Jan 3, 2008)

Well, interesting information, but I don't see any supporting information for what you contend is "the variable"... 

Where is the information that the voltage per cell is "the variable"... which you imply is the primary difference.... I don't see those numbers in your quote, nor any information comparing the difference between them. 

In fact, your quote states there is no difference: 

"These remarks apply equally to lithium ion and lithium polymer batteries. The chemistry is basically the same for the two types of batteries, so charging methods for lithium polymer batteries can be used for lithium-ion batteries." 

Got any better references? 

(note that I do not disbelieve you, just your supporting quotes do not support your assertion).... 

I'm ready to learn more, point the way... 

Greg


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## Michael Glavin (Jan 2, 2009)

Greg,
I included the "quote" to edumacate those that don't understand how Lithium charging is perfected and undercharging or overcharging Lithium is undesirable. In its entirety the aforementioned “quote” may not support my assertion on voltage variables, nor was it intended too. That said its common knowledge that chargers need be implemented with the correct charge regimen for the chemistry and cell/battery voltage in play.
It’s easy enough to validate my assertion, you can find 3.6V and 3.7v Li-Ion cells online easily.
And some chargers with Li-Ion and Li-Po regimens clearly demonstrate the chargers settings (read that cell/battery voltage parameters) are different for either chemistry.
It’s really pretty simple, match the charge regimen to the cell/battery voltage and it’s all good!
Balancing has proven to be a valuable in any circumstance, not all things are created equal, cells discharge at differing rates it’s a given. Charging a battery with multiple cells collectively is undesirable in the scheme of things with today’s technology.
Michael


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## Greg Elmassian (Jan 3, 2008)

I was hoping you would provide some links to edumacate me! ;-) (note my last line in my last post, sincere) 

Yeah, I think if there is no extra cost or hassle, monitoring and individually charging each cell is great. 

But I don't see it as a huge advantage in our lower drain applications. 

Have you been using li-po more than li-ion? 

Greg


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## Michael Glavin (Jan 2, 2009)

Greg,
You don’t need any more edumacating, you’re a Kalifornian and you can count to ten, enough said? 
Seriously, it’s all about the chargers voltage setting parameters for either Li-Ion (3.6/3.7) or Li-Po (3.7V). The abstract 0.1V difference increases/decreases the charging voltage specification employed which ultimately influences the ability of the cell/battery to adsorb a full charge or consequently over charges a 3.6V cell with 3.7V which more likely than not prematurely damages same. Albeit one cell under charge with a 0.1V difference in required voltage may be moot, but collectively as in a battery with multiple cells it adds up to overcharge or undercharge conditions. These cells are fragile (short life expectancy) enough in my vast experience why exasperate the inevitable.
Yes, of late I have more experience with Li-Po batteries. Predominately because I have had to discard well over 100 Li-Ion cells in multiple series/parallel form factors in the last few years (on-board flight packs for Giant Scale aircraft). 
I have been replacing the Li-Ions with Li-Po’s as they are cheaper initially and do not require paralleling multiple cells to get more capacity, that plus balance technology it’s an easy choice for me. And lastly I can use the Li-Po batteries in my airplanes and trains, so I get much more use out them in a given life cycle than I typically would. I use the batteries for on-board RC aircraft flight packs to power as many as 18 high power digital servos and CDI ignitions, power sources for all electric aircraft and lastly trains.
Michael


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## TonyWalsham (Jan 2, 2008)

I can understand the benefits of both Li-*** chemistries. 
However, the majority of battery R/C users I deal with want to install the batteries *inside* their locos. Having them removable so that external charging (and balancing if necessary) is problematic. Most want to charge in situ, which becomes electrically quite complicated if the cells have to be balanced. Let alone desirable from a safety point of view. 

Given that Li-Po's can be dangerous unless balanced, are Li-Ion batteries less so? 
In other words can Li-Ion say, be safely charged with just a pcb charge-discharge limiter built in and with no balancing ports? 
AristoCraft seems to think so as they sell Li-Ion battery packs with limiters but no balancing.


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## Michael Glavin (Jan 2, 2009)

Tony,
I have several engines rigged with dedicated batteries installed in the belly so to speak, It really is not difficult to find some place to access the balance/charging pigtails. I use extensions readily available to extend the JST plug connectors to extend their placement for easy access. So for me it’s know more difficult than what you describe in situ… Two plugs and it’s done.
As far as I know Li-Po’s are no more dangerous than Li-Ion’s to charge in an unbalanced state. It is true that Li-Po’s may become unbalanced to a greater degree in high demand conditions than Li-Ion with their typical low amperage demands. That said I find they all need to be balanced, matters not me thinks what technology, it’s a physics thingy. When charging typical batteries you’re charging collectively same voltage and current, some cells start at different voltages and adsorb charge at rates akin to their state of charge, internal resistance, age and physical condition. Accordingly individual cells will reach their full potential sooner than others. Balancing the cells allows the charge regimen to start with a level playing field, monitoring same as charge progresses, providing alerts when required and has been shown to greatly enhance the life cycle of said batteries.
Yes, you can charge Li-Ion and Li-Poly with only PCB’s in place. The simple PCB’s limit the static and discharge cut-off voltage of each respective cell only. In theory you can leave a battery on charge until a PCB opens the circuit at approximately 4.35V per cell, problem is by this time the cell is overcharged albeit it’s better than nothing IMO. It’s not uncommon to see this play out when cells are charged collectively as one or more is always typically lagging in charge adsorption (more obvious as the cells age).
As mentioned in posts previously and shown below I have Li-Ion batteries fitted with cell balancing pigtails in my Moguls Vandy tender, works great and often needs balancing. Charge jack, balancer socket and G-Wire Reciever are located under the tenders coal load on this LGB Mogul, within seconds I have acces to all. Batteries and Airwire decoder are in the tenders belly (harder to get too).
Michael


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## wigginsn (Jan 9, 2008)

Thanks Michael, I think you nailed the discrepancy between Li ion and LiPo from the point of view of the charger instructions . It's designed for 3.7 V per cell, and a 4.2 VPC charged target voltage. From what I read into your posts as long as the battery pack is made up of 3.7 V cells then whether they are Li ion or LiPo chemistry is not an issue. Maybe the manufacturer got cold feet and spotted potential Li ion issues after all the box graphics were signed off







OTOH they haven't changed them in the 5 or so yrs its been on the market..










And thanks for the tech stuff - very informative!

Tony I agree, I want my batteries to be internal to the loco and made as safe as can they can practically be. Thats why I want to include a PCM, with accessible balance and charge jacks in the loco - exactly as Micheal has pictured. I don't particularly want to remove them to charge - that would quickly take the gloss off things.

I still haven't figured out why having battery protection circuitry is specifically written out in the charger manual - unless there is a possibility of "smart" PCM's interfering with the internal balancing algorithms? Any takers on that one? I still need (want) discharge rate / short cct / low voltage cutoff protection in the pack and a low voltage warning like the Railboss provides is definitely desirable.

I've got no worries about the charger safety itself, Its got a standard (non balance) Li charge cycle and a balance cycle separately selectable, Charge rate is settable and cell counts entered must match the calculated count for the cycle to start. Hopefully I'm not in need of a new charger! 

Thanks again for all your input.

Cheers
Neil


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## TonyWalsham (Jan 2, 2008)

Hello Michael. 
I see how you have done it and is about how I envisaged it would be done. However, I think I need some assistance in obtaining the correct parts. 
I can see how you have mounted an "extension" balancing socket on the outside of the loco so that the battery pack can be balanced in situ. 
The sample you have shown is the opposite of what is on the battery pack. That is, it is the same as on the charger, so you must have used a cable with two sockets the same, one on each end to reverse the gender. 
Then, to access the charger from the loco port you will need another double ended cable, this time with two connectors the same as on the battery pack to reverse the gender back to suit the charger socket. 
My problem is I cannot determine which double ended cables I need to get, from say Hobby King. The pictures and descriptions they provide are just not clear enough. 
Would you be so kind as to steer me towards the correct parts for say a 4 cell pack?


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## Michael Glavin (Jan 2, 2009)

Neil, 

I'm not sure why your charger suggests it won't play with PCM's... I'll give it some thought today. 

Tony, 

Yeap, sounds like you defined my installation accurately. I'll dig up some pictures and part numbers for you when I return later today. 

Michael


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## Michael Glavin (Jan 2, 2009)

Tony,
The extension required depends on your model specific and battery needs. The battery balance pigtails plugs are not all the same type or gender. For many batteries JST-XH males are employed. 
If you propose a loose pigtail with JST-XH equipped battery accessible via a hatch or similar you merely need a 4S JST-XH male-female extension.
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9737
If you propose to mount a female socket as I did pictured previously you need two extensions one with female-female 4S JST-XH sockets and a male-male 4S JST-XH plugs. 
Use the same extensions noted above and cut then in half and splice them to obtain the required gender extensions.
Michael


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## TonyWalsham (Jan 2, 2008)

Thank you Michael. 

I think for the sake of simplicity I will show my customers how to do it the way you have done it. 

I know I am a bit thick at times but I cannot fined the same gender extension cables at Hobby King. Help!!! 

Once I get a chance to order some cables in from Hobby King I will set up instructions on how to do it for my own brand of ESC's. 
For now I will only offer the cables for 14.8 (4s) and 18.5 (5s) volt packs. They will be my most popular voltages. Plus, not all readily available chargers will handle 6s packs.


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## Michael Glavin (Jan 2, 2009)

Neil,
I pondered the dilemma you’re faced with abiding by the OEM instructions and nothing strikes me as an issue with any Lithium sans a balance pigtail. In fact since most Lithium-Ion batteries are equipped with PCB’s a quandary exists in my mind. Perhaps an inquiry with the OEM is in order. Me thinks their suggesting you mitigate use of the balance charger mode with batteries fitted with ancillary PCB/PCM’s and balance pigtails. If you had a balance charge pigtail equipped battery and a PCB/PCM in play to take advantages of same you’d omit the balance charge regimen. Perhaps some modelers can really screw stuff up??? If I wanted to use a PCB/PCM with a balance charge pigtail equipped battery I’d remove the pigtails male plug and connect the appropriate wires to the PCB/PCM eliminating the possibility for any boo-boos!
Michael


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## Michael Glavin (Jan 2, 2009)

Tony,

I'm confused, what gender are trying to match? What battery and charger is proposed?

The link I provided for a 4S JST-XH extension with male-female gender is what you need in either scenario I described previously.

Michael


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## TonyWalsham (Jan 2, 2008)

Thanks Michael. 

I am trying standard B grade Hobby King 4s Li-Po packs with what I presumed are standard balancing connectors. At least the battery balancing connectors plug straight into the I-Max B6 chargers I have. 

I see the male to female extension lead type cable which the link takes me to. 
Are you saying I have to cut and splice these to get the male to male and female to female cables I want? 
Or, can I buy cables already wired male to male and female to female ? If so, those are the things I cannot find on the Hobby King site.


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## Michael Glavin (Jan 2, 2009)

Tony,
Correct, I haven’t located a source for the cables pre-fabricated. Link below is for another option.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=140442875631+&clk_rvr_id=245105246388&item=140442875631
This link has some good info for identifying connectors:
http://www.chargery.com/doc/Chargery%20Accessories%20list%20v2.6.pdf

Michael


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## wigginsn (Jan 9, 2008)

I’d remove the pigtails male plug and connect the appropriate wires to the PCB/PCM eliminating the possibility for any boo-boos! 

Thats where I was heading in my mind for attaching a PCM, thanks for confirmation. 

Seems most places I look online have Li Ion with integral PCM's and the LiPo have balance pigtails only. One other option that occurred to me is that since I have the charging safety side covered with the charger (assuming I don't screw it up..  ) then a poly fuse for overload protection and an audible low voltage detect circuit should cover the discharge side of things. 

Cheers 
Neil


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## Westcott (Feb 17, 2009)

When I run my 6 cell LiPo, I plug a voltage display module (really cheap off Ebay) into the balance tail. 
This shows the individual cells' voltages in turn, and the total voltage. 
Also available with warning buzzer. 
Shows me when to stop running when the voltage gets too low, and acts a s a sort of fuel gauge. 
Sort of like watching the water level on a live steamer!


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## wigginsn (Jan 9, 2008)

Thanks Westcott, I think I'll be heading down a similar path. 

Cheers 
Neil


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## Randy Stone (Jan 2, 2008)

A lot of good info here for guys that already know a lot about batteries, but for me, it's mostly over my head. 

I was looking at using a 18 or even 22 volt Lithium batthery back. 

Then I was told by a couple people that a 14 volt pack wa better. 

It would last longer. 

So I ordered a 14.8 volt 7800mah 

But is this really the right way to go? 

Someone else told me today that the Revolution would need 3 of the 14 volts to run it. 

Then there is the P8 Phoienix sound system. 

Another concern I have is run time. 

How can a 14 volt pack give longer run time than an 18 volt pack? 

Seems to me you would have the trottle a lot higher with 14 volts than needed with 18. 

should I have ordered the 18 volt pack? 

By the way, the loco is an Aristo Craft Dash 9


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## izzy0855 (Sep 30, 2008)

Voltage in a lithium battery is not what makes a pack better then another, it's the cells a manufacturer uses, the milliamps of each cell and what size of weld tabs are used to discharge that pack. We use Sanyo & LG cells at 2800mah and when in parallel you can get 5600mah or 8400mah at 14.8V, 18.5 or 22.2V. Personally, I use 18.5V @ 5600mah Lithium packs in all my Dash 9's pulling 15 - 20 cars at a time with 4.5 to 5 hours of runtime. It takes more current (500 - 750 milliamps) to start and stop our loco then running at top speed. If you gradually increase & decrease your speed when starting and stopping your loco you will increase your runtime. You will find a 14.8V lithium pack will run sluggish compared to a 18.5V because the PCB in a 14.8V will cut-off at 9.6V or 6.5amps, which ever comes first. So if your drawing close to 6amps at anyone time, your lithium battery will shut-down until the PCB resets and/or the amps draw decreases. If you want to stay with a 14.8V lithium pack, please ask the manufacturer to build your pack with a 10amp PCB so you can draw more current. You will get longer runtimes with a 18.5V lithium compared to a 14.8V lithium when operating a Dash 9, because the voltage will drop faster due to the amount of current draw a Dash 9 needs to operate. 

Rick Isard 
Cordless Renovations, LLC 
Remote Control Systems of America


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## Del Tapparo (Jan 4, 2008)

I'm the guy Randy was talking to. Let's rephrase his question. When he told me he was using a 14.8V battery on an Aristo Dash-9, I thought that was not enough voltage to run at the speeds folks like to run diesels at. Since I'm not a diesel guy. How about it? Is 14.8V going to give him enough speed? I also told him the Revo, like any other ESC capable of track or battery power, will lose nearly 3 volts across the ESC (due to the full wave bridge and motor driver losses). It has been my understanding that the USA and A/C diesels require around 18V for satisfactory speeds. So somebody that owns this loco, please advise.

Randy - Your run time is primarily dictated by the mah rating of the battery pack. 7800mah is huge and should provide many hours of running, even on a power hungry diesel.


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## Greg Elmassian (Jan 3, 2008)

I have a question prompted by Rick's comment: "If you want to stay with a 14.8V lithium pack, please ask the manufacturer to build your pack with a 10amp PCB so you can draw more current. " 

I don't think you could pull 10 amps with a dash 9 under any condition (other than a short circuit)... I've only seen a loco draw 5 amps on rare occasions, and usually destructive. You will be into wheelslip at much over 3 amps. 

Rick, perhaps you could amplify, possibly you were thinking of running more than one locos, like 2 or 3? 

We do not pull the same current as model planes, definitely. (I'm fully aware of the high short term currents drawn briefly during starting)

Regards, Greg


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## izzy0855 (Sep 30, 2008)

Greg, 

Yes, that is correctly ... Aristo and QSI stall speed is around 3.5amps but if your using one battery to power more than one loco your amp draw will increase and will probably engage the PCB. So, to increase the current from a 14.8V 5600mah or 8400mah Lithium battery-pack, you increase the PCB's current output, thus 10amps. Not to plug! But, that's why I invented the RCS Booster. I have also operated two GP-40's and two Dash 9's in one consists "separately" from one 22.2V 8400mah Lithium-ion battery-pack on our C-10L Carrier Board, "wired in parallel" and pulled 7amps start & stop. 

Rick Isard 
Cordless Renovations, LLC 
Remote Control Systems of America


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