Li-ion Battery Packs In Series Or Parallel - Ok Or A No-no...?

Zerogee

Zerogee

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When using the Ansmann Li-Ion packs, all of which come with a built-in protection board, is it OK (read: safe) to connect two or more packs either in parallel OR in series, or will that cause problems with the individual protection circuits and/or confuse the charger?

The reason for the question is that while 14.8 volts and 5.2Ah can be most easily achieved by a single 4S2P pack like this:
http://www.rapidonline.com/electric...attery-pack-li-ion-4s2p-14-8v-5200mah-18-4128
there will be some loco applications where this pack, although very compact for the power it provides, still won't physically fit.

In such a case, there would be two possibilities for achieving the same total voltage and capacity - either two of these:
http://www.rapidonline.com/electric...ry-pack-li-ion4s1p-14-8v-2-6ah-inline-18-4126
in PARALLEL, or two of these:
http://www.rapidonline.com/electric...ry-pack-li-ion-2s2p-7-4v-5-2ah-inline-18-4122
in SERIES. Either set-up would still give 14.8V with 5.2Ah capacity, but is such a connection safe to do, or is it setting up potential (no pun intended) problems...?

Jon.
 
OK, partly answering my own question.... I've just looked at the description of the packs again, and noticed this which I'd compeletely missed before:
"The battery pack is ideal for use right away, or for making higher capacity or voltage battery packs by connecting it in parallel or in serial to other battery packs."

So, yes, it looks as if they can be RUN in series or in parallel - but I'm still unsure of whether they can be CHARGED that way? I'm leaning towards assuming the answer is yes, because there is nothing to warn against it - but has anyone here actually done anything similar or got any other relevant experiences?

Jon.
 
Hm shades of Boeing Dreamliners here. Wait till someone says definitively OK.
JonD
 
A good idea, Neil, just done so! I guess it's always best to get an answer from the professionals, I was just wondering if anyone on here had direct experience of anything similar.....

Will of course report whatever answer I get on here, for info to others!

Jon.
 
Well, questions asked and replies received!
I asked Rapid's tech people first, and while they were very helpful they were not 100% certain, so referred me direct to Ansmann in Germany; this is what I asked the Ansmann technical dept:

"Hello, I have a technical question regarding the use and charging of your Li-Ion battery packs with built-in protection boards. I have bought several of these packs in the UK from both Rapid Electronics and CPC Farnell, for use in large scale model railway applications. The information on the packs from Rapid indicates that two (or more) packs may be connected in PARALLEL to increase the overall Ah capacity; my specific question is this: If I used two of your 2447-3032-01 (4S1P) packs wired in parallel, to give me 14.8V and a total capacity of 2 x 2600mAh = 5200mAh, could those packs be charged while still connected in parallel - or would this cause problems with the charger and the protection boards in the packs - for example if one pack reached peak charge first, would the charger sense this and shut down, or would it continue until the other pack was also full? The reason that I can't simply use one of your 8-cell 4S2P packs is due to size limitations in this particular case. If the charging of the two 4S1P packs in parallel WOULD be OK, then is one of your 9C94131-01 chargers (which I already have) a suitable charger to use for this set-up? Many thanks, sorry this is such a long question, hoping you can give me a definitive answer!"

That was yesterday; today I received the following answer, from Ansmann's UK branch (which I didn't realise existed, otherwise I'd have emailed them directly!):

"Dear Jon
Thanks for your question, which has been forwarded to the Ansmann UK office. It is a question that we have been asked before. Our technical team in Germany has advised that it is OK to connect, charge and discharge these Li-Ion battery packs in parallel as long as the capacities of the battery packs are the same and that the battery packs are in the same state of charge when they are connected. The point about state of charge is very important.
Given that battery capacity deteriorates with age and usage, it would be wise to use battery packs with similar histories. The battery packs should also be replaced as pairs when they reach end of life.
The safety boards in the batteries are designed to prevent overcharge (because of safety issues), overdischarge (to avoid degradation of the cells) and overcurrent/short circuit (because of safety issues). The safety boards in the two battery packs will operate independently and protect each battery pack independently by disconnecting that pack from the circuit in a fault condition. The safety boards will detect overcharge at 4.325V per cell, i.e. approx 17.4V for a four cell pack. The charger will charge the battery packs as a pair to 16.8V and terminate the charge when the charge current has dropped to a certain level. As such the safety boards should not detect an overcharge situation in a normal charge cycle.
Our 9C94131-01 charger will be suitable for the set-up you suggest.
I think my answer might have been longer than your question. I hope it helps. If you require any further information please do not hesitate to contact me directly. "

A well-informed and detailed response, which I consider to be excellent customer service! :)

Hope this info may be as useful to others out there as it is to me - it certainly opens up the list as to which locos these batteries can be used in, as there are far more models which could take two of the 4S1P packs than have space of the single 4S2P pack. From the reply, I would take it to be a good idea to charge each pack separately to full capacity before installing them, so that once they are wired in parallel they will be as close a "match" as possible.

All I need now is to find some time to put some of this theory into practice.... :rofl:

Jon.
 
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So, really the answer 'yes' was conditional on several factors like matched pairs. So if you don't match the two banks of batteries then presumably the safety boards will provide protection?
 
trammayo said:
So, really the answer 'yes' was conditional on several factors like matched pairs. So if you don't match the two banks of batteries then presumably the safety boards will provide protection?
Click to expand...

As I read it, yes. The protection board in each pack will prevent that particular pack from overcharge or over-discharge (including excessively fast discharge due to faults or shorts), regardless of what the other pack is doing. The requirement of having both packs in a similar condition and similar state of charge before connecting them in parallel is just common sense, you wouldn't use a fully charged battery in parallel with a 50% discharged one with ANY battery chemistry, even dry cells.....

Jon.
 
Zerogee said:
As I read it, yes. The protection board in each pack will prevent that particular pack from overcharge or over-discharge (including excessively fast discharge due to faults or shorts), regardless of what the other pack is doing. The requirement of having both packs in a similar condition and similar state of charge before connecting them in parallel is just common sense, you wouldn't use a fully charged battery in parallel with a 50% discharged one with ANY battery chemistry, even dry cells.....

Jon.
Click to expand...

Well, 'we' wouldn't.. But there are some really stoopid people out there!!
And, we all make the odd error..

I recently acquired some red-outer Li-? batteries amongst an evilBay purchase.. They are sitting in a corner 'sand-bagged', just in case, whilst I work out if I am going to use them and get a suitable charger.. The seller stated he was going to get another charger, and they were £7 each. - That sounds way too cheap for a decent charger to me??
 
PhilP said:
Well, 'we' wouldn't.. But there are some really stoopid people out there!!
And, we all make the odd error..

I recently acquired some red-outer Li-? batteries amongst an evilBay purchase.. They are sitting in a corner 'sand-bagged', just in case, whilst I work out if I am going to use them and get a suitable charger.. The seller stated he was going to get another charger, and they were £7 each. - That sounds way too cheap for a decent charger to me??
Click to expand...

Quite, Phil.... "Make something idiot-proof and nature will make a better idiot..."
I think the thing to remember in this is that if we're going to use packs in parallel, buy both packs at the same time, charge them both up fully before connecting them and keep them as a pair throughout their operational life.

Re your charger question, yes, that does sound a little cheap.... the Ansmann charger I'm using is just over 25 quid. I guess that cheaper ones are available that MAY be perfectly good (after all, even the Ansmann branded ones may well be Chinese-made - though I've just had a look at mine and it doesn't actually say that anywhere...), but then again they may not.....

Jon.
 
Zerogee said:
As I read it, yes. The protection board in each pack will prevent that particular pack from overcharge or over-discharge (including excessively fast discharge due to faults or shorts), regardless of what the other pack is doing. The requirement of having both packs in a similar condition and similar state of charge before connecting them in parallel is just common sense, you wouldn't use a fully charged battery in parallel with a 50% discharged one with ANY battery chemistry, even dry cells.....

Jon.
Click to expand...

Absolutely - lowest common denominator thingy! Apart from that, it's useful to know about the paralell bit. Me, I have not gone much beyond Leclanche cells! I prefer to remove the batteries for charging because my conversions or scratchbuilds are small motors not drawing much current and (usually) consist of AA sizes.
 
Great response from Ansmann.
Now I have a little question.
I have one of Ansmann's quad intelligent chargers that can do four different batteries (up to 14.8V) of different (or same) chemistries in one go.
They supply balancing leads for connecting Litho batteries but the batteries that Jon is using have their own balancers on board.

My question is...with the batteries that you are using Jon, would I just connect to the charger to the Litho packs with the two wire system as for all other battery chemistries? And the 'smart' charger would do the detecting of charge level etc.
I am pretty sure that the twin wire method is the way but just in case........ I know that Li-FePO4 batteries need the balancer connection but your Li-Po ones seem to be just the two wire charge.
 
beavercreek said:
Great response from Ansmann.
Now I have a little question.
I have one of Ansmann's quad intelligent chargers that can do four different batteries (up to 14.8V) of different (or same) chemistries in one go.
They supply balancing leads for connecting Litho batteries but the batteries that Jon is using have their own balancers on board.

My question is...with the batteries that you are using Jon, would I just connect to the charger to the Litho packs with the two wire system as for all other battery chemistries? And the 'smart' charger would do the detecting of charge level etc.
I am pretty sure that the twin wire method is the way but just in case........ I know that Li-FePO4 batteries need the balancer connection but your Li-Po ones seem to be just the two wire charge.
Click to expand...

Yes, Mike, it's a simple 2-wire connection, which is what makes these batteries ideal for charging in-situ for applications where access (or lack thereof) makes it difficult or impractical to remove the batteries from the model every time you want to charge them - as you don't have to worry about also plugging in a multi-pin connection for the balancer. All the protection and balancing requirements are handled by the integral boards under the shrink-wrap of the battery pack.

Jon.
 
Interesting. I suppose the built in board provides protection. For dry cells, it is not recommended to run in parallel because of the reason Ansmann UK referred to - differing voltages (state of charge). A battery in a higher state of charge will try to rapidly balance the other battery and the heat produced can be significant. Toy safety regs specifically forbid parallel connection.
When I was in the toy industry many years ago (15) we short circuited a standard AA battery with one of those giant paper clips (don't try this at home disclaimer!). It got far too hot to handle.
 
I'm a little suprised that a manufacturer/dealer would recommend charging packs in parallel.

Normally this is ok with the qualifications they state. But they have no control that the paralleled packs are not matched. In the US most companies would be afraid of being sued.

If the packs were matched well when new, and always charged and discharged together, then I would not worry, no more than the usual care to watch for any anomalies in behavior during charging or discharging.
 
Well, some of the complete battery packs that Ansmann supply ALREADY contain parallel-connected cells - as denoted by the terminology describing their cell arrangement: the 8-cell 14.8V 5200mAh pack is described as "4S2P", which means 2 parallel banks (the 2P part) of 4 cells in series (4S). Each cell is a 3.7 V Li-Ion cylindrical type of 2600mAh capacity. Similarly, while you can buy the 4-cell packs in 4S1P (4 cells in one bank, giving 14.8V at 2600mAh) you can also buy the same 4 cells wired as 2S2P, which is 2 parallel banks of 2 cells, thus giving 7.4 V at 5200mAh.
Even this simple 2-cell pack:
http://www.rapidonline.com/electric...battery-pack-li-ion-1s2p-3-7v-5200mah-18-4119
is a 1S2P, where the two cells are wired in parallel to give a 5200mAh capacity at 3.7 V.

If you look at the table of voltages/capacities in the link above, at the extreme there is a 7S3P pack, which is 21 cells in THREE parallel connected banks of 7 cells each, giving a voltage of 25.9V at a huge 7800mAh capacity, for those that want a LOT of power......

Also consider the current (ha!) electric cars which use Li-ion battery tech - especially the high-performance cars - they use banks of dozens or hundreds of cells, and they can't all be connected in series or the voltages would be huge - so they use many multiple banks connected in parallel:
https://en.wikipedia.org/wiki/Tesla_Roadster
There may be some scare rumours around, but I can't actually recall any news reports of any such car suffering a catastrophic battery explosion?

Jon.
 
Humm..
I think I would prefer hydrogen to batteries in an accident..

At least the hydrogen would flare off upwards..
 
I can see how parallel connected batteries with in-built protection could be ok. What about those high-discharge rated packs with cells in parallel? I read (can't remember where) that batteries connected in parallel when not in use will discharge each other, because the voltages are never exactly the same. This makes sense and I wonder how they get around that.

Personally, I would always have a double pole power switch that disconnects the batteries from each other when off.
 
Beddhist said:
Personally, I would always have a double pole power switch that disconnects the batteries from each other when off.
Click to expand...

That seems to be a sensible suggestion.:)
 
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