Li-po / Lith Ion batteries in parallel

[ge_rik]

I've tried seeing if this has already been covered somewhere but not managed to track down the thread. I have a feeling I've seen somewhere on here that it's not advisable to connect Li-po batteries in parallel - or am I imagining it?

I've bought one of the Li-pos which Mel suggested on this thread - http://www.gscalecentral.net/m206304 but I'm wanting to run two motors in tandem for my recent http://www.gscalecentral.net/tm?high=&m=216042&mpage=1#216952 < Link To railmotor kit-bodge and am thinking that two motors might drain a single battery too quickly.

What's the collected wisdom on this?

Rik

 

[Neil Robinson]

Re:Li-po batteries in parallel

I would advise against connecting any batteries in parallel.
One alternative for one 12V LiPO is to use two 6V motors in series. Actually they don't need to be 6V motors just motors that are good for at least 6V and are geared to run at an acceptable speed on 6V.

 

[whatlep]

Re:Li-po batteries in parallel

I've tried seeing if this has already been covered somewhere but not managed to track down the thread. I have a feeling I've seen somewhere on here that it's not advisable to connect Li-po batteries in parallel - or am I imagining it?

I think you mean Li-ion rather than Li-po, but the basic principle is the same. Don't parallel rechargeable cells due to the risk that they contain different charge and one tries to starts charging the other.

A more basic question to me is why you would need more than one battery. The 6800 milliamp rated Li-ions that I use as standard willpower my LGB Schoema for several hours. How much current is your motor drawing? Even if it averages 500 milliamps you've got 13.6 hours in theory between charges. Probably 75% of that in real life.

 

[Madman]

Re:Li-po batteries in parallel

I use a 14.8 volt Li-On battery to power my dual motor wizzy cranks 2095. It goes for hours without a problem.

 

[ge_rik]

Re:Li-po batteries in parallel

A more basic question to me is why you would need more than one battery. The 6800 milliamp rated Li-ions that I use as standard willpower my LGB Schoema for several hours. How much current is your motor drawing? Even if it averages 500 milliamps you've got 13.6 hours in theory between charges. Probably 75% of that in real life.

I'm considering adding another motor to the trailer on my railmotor set as it is underpowered with only one motor. My thinking is that as the trailer will also be powered I'll have to add weight - so why not add that in the form of another battery and so double the run time? Clearly the two motors will have to run together at the same speed and hence my thoughts about connecting them.

Rik
PS - Yes - you're right it is a 'Polymer Lithium-ion' battery. As you can tell, this is new territory for me.

 

[MRail]

Re:Li-po batteries in parallel

I use a 14.8 volt Li-On battery to power my dual motor wizzy cranks 2095. It goes for hours without a problem.

Dan, do you have details of the battery?
It's a minefield trying to find the "right" type on the net.

 

[GAP]

Re:Li-po batteries in parallel

Quote, I've bought one of the Li-pos which Mel suggested on this thread - http://www.gscalecentral.net/m206304 End quote.

Could I please get some comments/recommendations on the use, etc, of this battery?
At present I am using AA NiMH batteries but this looks like it may be the way to go in the future.
I saw Matthew's thread recently where charging and using it was discussed, but not knowing the details of it, the comments about charging plugs and output plugs left me a little confused (which at my age doesn't take much).
I take it is Li-ion and not Li-po (which I will avoid like the plague).
Any help greatly appreciated.

 

[vasim]

Re:Li-po batteries in parallel

Yes, avoid Li-Po's like the plague. My Dad flies radio controlled planes and their only virtue is their lightness. Only helicopter and aeroplane modellers tend to be forced to use these.
You need a balanced charger to charge them otherwise they could explode. You need to monitor them as they charge in a non combustible area as they can catch fire if you charge them for just slightly too long. They must not be trickle charged and each cell must not be charged over 4.2 volts 0r they may explode. Also, if you discharge them below 2.5 volts per cell, the battery becomes scrap. If you store a Li-Po, it must be kept charged at around 50% capacity. If you forget about it and it discharges completely, then it is scrap. If a Li-Po shows signs of puffing or swelling, or feels softer than normal, do not attempt to charge it.
Strangely, this is a battery that children are allowed to buy and you are allowed to dispose of them in the dustbin, but if it gets damaged it could explode. A trick before disposal if you are unsure of any charge left in it is to bang a nail through it.

Anyway, if you really do want an expensive, dangerous, lightweight and fussy battery - read this link first and watch the video >>
http://www.rchelicopterfun.com/rc-lipo-batteries.html

http://www.youtube.com/watch?feature=player_embedded&v=VswaFOrVM6I

 

[Madman]

Re:Li-po batteries in parallel

I use a 14.8 volt Li-On battery to power my dual motor wizzy cranks 2095. It goes for hours without a problem.

Dan, do you have details of the battery?
It's a minefield trying to find the "right" type on the net.

Here is where I purchased my original Li-on batteries. As I mentioned, these batteries have given me excellent service. However, in the never ending quest to be as cheap as possible, I have also purchased some of the Chinese batteries on Ebay. I am also quite happy with them. They are smaller and have been useful where I wanted to place a battery in the loco or trolley. As some have said, you really should not need two batteries.
http://www.all-battery.com/li-ion14.8v4400mahpcbpreotectedrechargeablebatterywithbareleads-31023-01

 

[Fairlie]

Re:Li-po batteries in parallel

I would advise against connecting any batteries in parallel.
One alternative for one 12V LiPO is to use two 6V motors in series. Actually they don't need to be 6V motors just motors that are good for at least 6V and are geared to run at an acceptable speed on 6V.

One problem with running two motors in series on uncoupled wheelsets is that if the wheels driven by one motor slip, that motor is deloaded. Since the motors are in series, the current to the other motor is reduced also. This will probably result in a stall. With the motors in parallel, the other motor retains full power.

 

[ge_rik]

Re:Li-po batteries in parallel

PS - Yes - you're right it is a 'Polymer Lithium-ion' battery. As you can tell, this is new territory for me.

There is no such battery as a Polymer Lithium Ion.
It is either a LITH POLY or a LITH ION.

Just quoting what it says on the label on the battery - 'Polymer Lithium-ion'
Not at home at the present (and won't be for another week) so can't double-check - anyone else got one of these batteries following Mels original posting just to confirm I've not misread the label.
Rik

 

[ge_rik]

Re:Li-po batteries in parallel

Just changed the title of the thread to include 'Lith-ion'. There's a lot of useful info on here which someone in the future might want to access so it makes sense for Lith-ion to be included in the title should the thread some up in a search

Rik

 

[CoggesRailway]

Re:Li-po batteries in parallel

not sure that they are as useless for trains as vasim suggests if you are know what you're doing. I really wouldn't bang a nail through one either. if you want to get rid of it just take it to the battery disposal at the local authority dump ensuring the accept lith. in the main i agree with vasim - i have biggish locos and weight is good for traction so I went NIMH. The biggest factor was they are less fussy/dangerous for the rank amateur tinkerer that I am!

 

[whatlep]

Re:Li-po batteries in parallel

Just quoting what it says on the label on the battery - 'Polymer Lithium-ion'
Not at home at the present (and won't be for another week) so can't double-check - anyone else got one of these batteries following Mels original posting just to confirm I've not misread the label.
Rik

Here's a cross-reference to my thread on the subject. http://www.gscalecentral.net/tm?m=165095&high=lithium-ion The first post contains a picture of the two types of battery I have used (and which Mel - yb281 - also uses after seeing mine!). I think the text is pretty readable. Both are 12 volt, 6800 milliamp/hour capacity packs with a switch.

For those who've asked the question in earlier posts, there are umpteen batteries of the 12 volt Li-ion type on eBay. The basic question you need to answer is how many milliamhours (mAh) you need. I use the 6800 mAh variety simple because the price-performance is better than the 4800mAh types and the size is less of an issue in getting a battery into vehicles than the higher-capacity 9600 mAh types.

To look for suitable cells on eBay, use keywords "12v 6800 li-ion". Substitute 6800 with 4800 or 9600 as appropriate.

 

[ge_rik]

Re:Li-po batteries in parallel

It seems I must be wrong then

Rik

 

[whatlep]

Re:Li-po batteries in parallel

It seems I must be wrong then

Rik

Rik - the important bit is whether you've got enough info to get a battery for your original requirement to satisfy a 2-motor loco. My hunch is that a 12 volt 6800mAh Li-ion cell should do, but you'll need to do some checking on the beastie's current draw (milliamps) and possibly how many volts you need to run at a speed which looks right to you. Suggest you check the volts bit first. If you need more than 11 or so when running, a different battery solution may be what you need. If you're running on track power when testing, remember that when you remove the pickups to go to battery power, there will be less "drag" for the motors to overcome, so you'll likely get away with 1 volt less on battery power than you need for track power.

If that's all double Dutch, feel free to PM me!

 

[ge_rik]

Re:Li-po batteries in parallel

Rik - the important bit is whether you've got enough info to get a battery for your original requirement to satisfy a 2-motor loco. My hunch is that a 12 volt 6800mAh Li-ion cell should do,

This is the eBay page for the battery which I bought - which I think differs slightly from the one shown in your photos.

http://www.ebay.co.uk/itm/290656714473?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649 < Link To http://www.ebay.co.uk/itm...ksid=p3984.m1423.l2649

You can see my confusion as it's actually advertised as a Li-po - but somehow I don't think it is. As mentioned earlier, I'm working overseas at the moment so can't actually get to the battery itself - however, whatever it is, it appears to be listed as a 12v 6800mAh battery of some sort so I imagine it will do the job of driving two motors - if that's the route I decide to go down to solve my power problems.

Rik

 

[whatlep]

Re:Li-po batteries in parallel

Hi again Rik. Yes, I can understand any confusion: the listing clearly says Li-Po, but in the picture of the battery which shows the side with text on it, the writing is just legible and it says.... Li-ion battery!

The guy you've bought from is the same as I have used in the past, so I'm 99.99% sure that you've bought a Li-ion battery which should be fine for your loco.

 

[Tony Walsham]

Re:Li-po batteries in parallel

Yes it definitely does describe it as a Li-Po battery.
However, I can see no way it can be balance charged from the supplied charger. In which case you should be very wary about using it.
My guess is it really is a Li-Ion pack that is being mis-advertised as a Li-Po.

 

[yb281]

Re:Li-po batteries in parallel

Well I've posted this at least twice before, but either the previous posts have been ignored, or they don't comply with certain agendas?

These batteries are lithium-ion, I now have 4 of them, the chargers that come with them have always worked and come with the correct pins for British use (presumably having been delivered to a British address). The li-po description is wrong, but his Engrish is still better than my Chinese. The batteries are easy to use (with the usual care) and last for weeks, if not months between charges when used to power a single motored loco (including my G3 pannier tank) and I have absolutely no hesitation in recommending them.

However, to answer your original question Rik, I wouldn't recommend them for your proposed doubling up idea.