Are 2 batteries as good as one on its own?

[Olly Giles]

I am wnting to move alot of my flying over to electric as it is easyier for a chap like me with limited time. I was looking at the Sebart angel s50e but it requires a 6cell battery which would cost an astronomical £160 for one. But two 3cell to make the neccercery mah'age would 'only' cost £90. Would this affect the performance or not? The batteries i am looking at are the new flightpower EONX.

[Vic. P.]

Hi Oliver,

 I've seen a set-up on a Gaui 550 Hurricane electric heli that uses two 3 cell packs  instead of one 6 cell pack, the main reasons for doing this i think were cost and the fact that a lot of heli fliers tend to already have 3 cell packs for the smaller 450 size helis.

 Apart from recharge times taking longer when charging two packs instead of one, there seems to be no reason why this set-up shouldn't work just fine so long as the resultant voltage is  the same as the 6 cell pack. Mah will only really effect the duration of the flight so the higher the better. Unless weight becomes an issue 

 EONX lipos should be fine and have a high c rating which should provide plenty of power on demand.

 I fly a Sebart Sukhoi 30 E which uses 3 cell packs (keeps it nice and cheep on batteries) and although slightly smaller than the 50 E is still a pretty good flier in all conditions except  strong and gusty winds where it tends to get knocked about a bit.

  I've also been looking at the Sebart Miss wind, (the bi-plane) but it's a bit pricey for me

 

 Have fun with the kit !

 

Regards

 Vic.

Edited By Vic. P. on 20/09/2009 14:41:42

[Tim Mackey]

First things first. You are shopping in the wrong stores - I have 3 x 6S packs, of which none cost over a hundred squid - try shopping around the likes of giant cod, and foamyjets etc.

How does the 2 x 3s packs work out at £90 for the same pack capacity ?? Dont get it.

 

Second. Assuming you have a charger capable of handling a 6s high capacity LiPo ( say 3000mahr or higher ) then using two 3s packs in series which MUST be of the same capacity will take exactly the same recharge time so not sure where Vic gets that from.

 

Example Lipo. Whopping 4300 mahr and a great make too! Under £95

 

If you can get away with 3000mahr then how about just £53 ? Same supplier.

Edited By Timbo - Moderator on 20/09/2009 14:59:36

[Vic. P.]

Hi Tim,

 I was assuming that the charger would be one of the cheaper ones that charge up to 5 cells since Oliver was steering away from 6 cell packs and therefore the two packs would need charging seperately

 Guess i shouldn't make assumptions

 

I'll also be having a look at the supplier above too, looks like a good source

 

Regards Vic.

[Olly Giles]

Vic's right.

I only have a fairly basic 5 cell charger, and the battries recomended for the Angel are the flightpower brand. I was looking at the new EONX range as these have a 5c charge rate. So two 3 cell packs would save me buying a new charger.

[Tim Mackey]

Posted by Oliver Giles on 20/09/2009 13:13:53:

I am wnting to move alot of my flying over to electric as it is easyier for a chap like me with limited time. I was looking at the Sebart angel s50e but it requires a 6cell battery which would cost an astronomical £160 for one.

But two 3cell to make the neccercery mah'age would 'only' cost £90. Would this affect the performance or not? The batteries i am looking at are the new flightpower EONX.

 

But you didnt make that clear.

You merely "complained" about the price of a 56s battery, and if the model requires 6cells.... then it requires 6cells.

You still dont expalin how 2 x 3s packs of the same capacity cost £70 less.

Packs claiming 5C charge rate have nothing to do with it....your "fairly basic charger" will not be able to charge at 5C.

[Olly Giles]

Ok i will rephrase my problem. I only have a charger that will do up to 5 cells and up to 5A output. If i bought two 3 cell, 2200mah battries and put them in series would this produce the same performance as one 6 cell battery of 4400mah? I was looking at the flightpower battries as they are recomended by Sebart. Whether a Flightpower battery is necessity or not, im not so sure.

[Tim Mackey]

Yes.

A flightpower battery is NOT required.

[Olly Giles]

I have to admit. I have just been looking at the reviews on those loongmax battries and they look like a bargin. Im not that clued up on leccy. I do have a couple of small elecrics and the ease of it compared to glow is a huge advantage. Im looking to phase most of my models over to electric eventually but wanted to start with one and see how i find it. What is the charge rate on those loongmax packs?

[Bruce Richards]

No I think you are wrong if you put 2 3S 2200mah batteries in series you get a 6s 2200mah not a 4400mah. Thus you end up with half the capacity you need. If you want 6s 4400mah you would need 2 3S 4400mah packs in series.

 

Typical charge rate for Lipos is 1C and that is what I use for my loong max packs.

Edited By Bruce Richards on 20/09/2009 20:57:48

[Bruce Richards]

You could get  this and with the money you save over FP get a new charger to charge them like this.

 

No relationship to GC except a happy customer.

Edited By Bruce Richards on 20/09/2009 20:53:43

[Olly Giles]

Posted by Bruce Richards on 20/09/2009 20:43:48:

No I think you are wrong if you put 2 3S 2200mah batteries in series you get a 6s 2200mah not a 4400mah. Thus you end up with half the capacity you need. If you want 6s 4400mah you would need 2 3S 4400mah packs in series.

 Edited By Bruce Richards on 20/09/2009 20:57:48

 I would ask timbo on this

[Vic. P.]

Hi again Oliver,

 Speaking entirely from personal experience;

 When i first started buying lipos, i went for the cheaper ones for obvious reasons, BUT, i found that even with very careful charge and discharge routines (i never over-discharged them and always ballance charged them at the recommended 1C),  these cheaper cells tended to fail very quickly with some blown cells on packs that had only done 20-30 cycles. EG: Century 2100mah 3s1p  (which cost  £29.00 three years ago)

 I then started to buy the more expensive, but well reviewed lipos and chose to use Thunder power and Flight power packs and i'm still using them now after many hundreds of cycles and without any failed cells. EG: Thunderpower 2700mah 3s1p (which cost £61.99 from Midland helicopters now)

 My point i suppose is that you get what you pay for. Based on my own experiences, i would recommend that you go for the more expensive but more reliable Flightpower  or  Thunderpower  lipos as i reckon they would easily outlast the cheaper brands and even though they are twice the price, i don't  think the cheap ones would last even half as long.

 Sometimes a manufacturer will recommend a battery based on selling an affiliated companys products, that may or may not be the case with Sebart but having used these products myself i can see why Sebart would want to pair their products with Flightpower.

 

Hope this is of some help to you in making your decision

 

Kind regards

 Vic.

[Tim Mackey]

Posted by Oliver Giles on 20/09/2009 21:01:40:

Posted by Bruce Richards on 20/09/2009 20:43:48:

No I think you are wrong if you put 2 3S 2200mah batteries in series you get a 6s 2200mah not a 4400mah. Thus you end up with half the capacity you need. If you want 6s 4400mah you would need 2 3S 4400mah packs in series.

 Edited By Bruce Richards on 20/09/2009 20:57:48

 I would ask timbo on this

 Bruce is absolutely correct. I missed that part of your post.

[Tim Mackey]

Loong max and several other budget brands these days are every bit as good as flightpower - I stopped buying FP a couple of years back. There are some rubbish cheap packs around - but Zippy and Loong Max are not amongst them!

1C charge rate.

[birdy]

In short,

2 batteries in series = 2 times voltage

2 batteries in parralell = 2 times capacity

2 batteries in parralell x 2 batteries in seiries = twice voltage and capacity and 4 batteries

 

All lipos cells are effectivy the same (except for c rating - but that isn't what we are talking about here), and the batteries are made up by putting cells of certain capacitys in seiries (and uncomminly in parralell) to reach the required voltage. The difference between brands in the way the select and match the cells; flight power will have mad sure the cells are as similar as can be, and resulting in exactly the same discharge in each cell, so they rarely need balencing probably other things that I can't think of. In a cheaper pack, the cells will just be less well matched resulting in the need to balence more often.

The other thing that changes is the capacity / c rating / weight. Slightly more expensive cells will have better capacity for the weight ratio, and c rating to weight to capacity rating.

 

C ratings:

c ratings are basically how good the cells are at discharging in comparison to their capacity:

 

cell capacity in Ah x c rating = max current output for that pack

 

so:

 

2.2Ah (2200 mAh) x 20 (most packs these days are 20c or 25c) = 44 amps

 

However it isn't recomended really that you reach the max output of a pack - make sure it has some headroom

 

The only real important bit of the post here is the top bit and that you would need four of the said batteries to acheive the big battery - also it is worth investing in a good balence charger,

Hope this helps,

 

birdy

[birdy]

Oh, and in general I agree with timbo, charge at 1c - lower is slower (haha it rhymes!), although it will also prologn the life of you packs by a small bit.

[Bruce Richards]

I can not agree with you Birdy that price is everything when buying Lipos. I have bought some very cheap Lipos that have turned out to be very good. I have never bought the more expensive brand lipos and probability never will. One good way to choose is to go with what others recommend and I cancur with Timbo that Zippy and Loong Max are good and Rhino  look to be good too.

[Olly Giles]

So the best thing is just one big battery, But this battery business is all very confusing.

Does anyone have a 50 size patternship running on 5 cells?

[Vic. P.]

Posted by Bruce Richards on 20/09/2009 21:29:22:
 I have never bought the more expensive brand lipos and probability never will.

 

 

 Er forgive me if i seem a bit confused by this comment , if you've never bought one of the more expensive brands, then how would you know that the cheaper ones that you are buying are as good as the more expensive ones?

     

       Regards Vic.

[birdy]

 

Posted by Oliver Giles on 20/09/2009 21:38:08:

So the best thing is just one big battery, But this battery business is all very confusing.

Does anyone have a 50 size patternship running on 5 cells?

 The simplest  thing is one big battery.

Theoretically, you can run anything on as many cell as you want, because what matters is the wattage. However:

 

volts x amps = watts

 

So if you have a low voltage then you need a lot of amps, which means oversized compontes and extra heat, but if you have a low ampage then you need a high voltage, which makes it harder to charge things and also eventually means you have to use a seperate rx battery or UBEC.

[Tim Mackey]

I assure you that amongst the 150 or so various Lipos that I own, there is indeed a mixture of expensive brands and cheaper varieties...including the excellent Rhino packs that Bruce mentions. Having used them all many times over many years and cycles, I reiterate again - certain cheaper packs are every bit as good, if not better than the expensive brands supported by huge marketing budgets.

I have checked retained capacity, cold weather performance, cell temperatures during high discharge, overall life span of acceptable capacity, and finally the IR of each pack - as measured by my 1010B+ Junsi charger.

Its your money..... and your choice.

Edited By Timbo - Moderator on 20/09/2009 23:17:25

[Bruce Richards]

Vic,

 

I thought I might get that comment (how do you know if you have never bought the expensive ones) when I posted my comment. I was not comparing the two just saying the the cheap ones I have bought have been good enough for me and many others in my club that use them.

[Tom Foreman]

Battery technology is evolving quite quickly, and the cheaper cells are catching up to the expensive ones my first set of 22c electrolites were quite poor and only lasted 6 months of moderate use, my second set of 25C Electrolites have now lasted a year of heavy use and are still going strong.

 

To answer the original question the only problem with linking batteries together is that for best performance they need to be exactly the same, even the same age and usage to perform like a single battery. You also add extra weight and fitting the two batteries in to the model can be a challenge. I started off using two Electrolite 22C 2600 4s1p in parallel as a 5200 in my Dualsky Extra and was only getting 7 mins duration of easy flying, I then switched to a single Electrolite 25c 4s1p 3700 which was lighter and put less stress on the undercarriage and still get the same flight times of demanding flying over a year later, basically the 22c were going knackered but the new battery is still going strong. Not very scientific I know, but the single battery is lighter and easier to fit in the model, I don't have to charge it as a pair like the others so it makes them more flexible to be used in other models.

 

Basically I'd recommend getting a cheap 6s1p from hobby king, the last one I got from them was a Turnigy 30C 6s1p 4000, worked out about £70 after shipping and taxes

 

Tom

[birdy]

As if to prove the point, the latest edition of BMFA News ( Hoping that it in now way competes with RCM&E!) had an artical that came to the concluesion that loong maxes were better then Eon x's:

The batteries were both 30 c, the loong max being of 2250mah and the flightpower 2200mah

 

At the end the loong max had heated up less

They had both delivered 93% of rated Mah

They LM delivered 86% of rated watt hours, the FP 84%

 

And thats the interesting bit... Spose I should give credit for this infor to Bob Smith

 

Birdy