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[triumphjon]

ive been making all of my models to a standard 1/12th scale , this has resulted in some of my boats being rather small @ 15 inches long , my problem being that with the standard buggy type 7.2 volt packs they are either too large for the space ive available or just far too heavy , is it possible to use the lighter lipo batteries with my existing esc s ?

[CF-FZG]

If the esc has a LiPo low voltage setting then yes no problem, (I've only seen this facility on brushless esc's though).   
I guess you're looking at 2s packs to replace the buggy packs, but because most LiPo compatible esc's require a fully charged pack to determine the cell count, (as a discharged 4s pack can appear to the esc as a fully charged 3s pack, and gets worse as the cell count goes up), also some of them calculate the low voltage cutoff as a percentage of the pack voltage on connection, so if you connect a partly discharged pack to one of these you can pull the voltage down to a dangerously low level.

If the esc doesn't then you can use a LiPo-Guard to monitor the pack voltage and it gives either/or visible or audible warning that the pack voltage is getting low.


Hope this is of some help,

Mark

[snowwolflair]

Yes but you should also wire in a battery monitor that makes a loud noise when you reach the limit of discharge of the LiPo.

the LiPo's are also less weight per volt/amps than other batteries, helpful in small models.

[triumphjon]

so what i will also need is a voltage monitor /protector , what do the 2s 3 s numbering mean ? the voltage of the pack is obvious but not these extra numbers ?

[John Mk2]

Number of cell's per pack. 2s = 2 cell's (7.2v)   3s = 11.2v  4s = 14.4v & so on.   & the C rating   A 1000mah 20c can put out 20 amp's (ish) Iam sure someone can explain it better than I can 

[gribeauval]

so what i will also need is a voltage monitor /protector , what do the 2s 3 s numbering mean ? the voltage of the pack is obvious but not these extra numbers ?

It's the number of individual cells in the pack to give the voltage stated on the outside of the pack.  So divide the stated voltage by the 2s or 3s etc and you know the number of cells in the pack.

[snowwolflair]

The C rating is the maximum sustained current draw  so C30 is 30 times the pack current rating.  Unless you are planning a fast electric its unlikely you need a high C value and the batteries get more expensive the higher the C value.

I use 5 amp C20 11.2volt packs bought on Ebay from Hong Kong for £12 in my scale models and they hardly draw 1 amp never mind the potential 100A.

Just be carefull not to short them or you will quickly see the dammage 100A can do 

[triumphjon]

im thinking of using this type of battery for both my 1/12th scale fairey huntsmans & my latest 1/12th scale water jet driven dory project , all of which are fitted with brushed motors ranging from a single 400 to twin 400s & 700 s !

[John Mk2]

Sure we can sort it between all of us on here 

[triumphjon]

was hoping to , eventually i intend to replace my brushed motors for brushless ones , but for the moment its just batteries that i require

[John Mk2]

Just let us know when you want to move on 

[wibplus]

The 2s, 3s, 4s etc works like this :

1 single lipo cell = 3.7volts
2s means 2 in series = 7.4 volts
3s means 3 in series = 11.1volts  etc.etc.

You can also get e.g. 3s2p which means 3 cells in series and 2 in parallel which would boost the amps per hour rating.

You can get almost any combination of series and/or parallel to suit various voltages or amperage.

Hope this helps.

[triumphjon]

with my existing set up in my huntsman31 im running two 7.2 packs to give me 14. 4 volts , would i be right in thinking that i would only need one battery to acheive the same voltage ?

[CF-FZG]

with my existing set up in my huntsman31 im running two 7.2 packs to give me 14. 4 volts , would i be right in thinking that i would only need one battery to acheive the same voltage ?

Yes, 1 x 4s pack will give a nominal voltage of 14.8v, although as you already have the mountings for 2 x 7.2v buggy packs, I'd be tempted to series up 2 x 2s packs and use the existing mounts  

Edit: Because I neglected to clarify the safety aspect, (thanks wibplus ) if you use 2 x 2S packs in series as I mentioned above - a proper charging regime needs to be adhered to to prevent a potentially dangerous imbalance between the packs.

Mark

[wibplus]

with my existing set up in my huntsman31 im running two 7.2 packs to give me 14. 4 volts , would i be right in thinking that i would only need one battery to acheive the same voltage ?

Yes thats right. one 4s pack will give you that same voltage because that is 4 x 3.7volts in series to = 14.4 volts.(14.8 nominal)
The paralleling in the pack will boost the amps. You can get e.g. 4s2p (4 in series 2 in parallel )
                                                                                          4s3p (4 in series 3 in parallel )  etc.etc giving longer running time for the same voltage.

Some MAJOR do,s and don't,s

DO use a dedicated LiPo charger                       DONT use any other type of charger
DO charge in a metal box or LiPo sack                DONT charge on flamable surfaces
DO always attend a charging LiPo                      DONT take chances and leave it
DO charge within the correct range                   DONT ever charge a an excessive rate (they can violently explode)
DO maintain it above minimum charge                Dont ever run it flat they are not designed for that
DO use a monitor and alarm                              DONT attempt to guess the runtime

Be sure you know as much as you can find out about LiPos. Be aware that they can explode into violent fire if they are mistreated or damaged. The Lithium will burn quickly if exposed to atmosphere. Never use a damaged or swollen pack.

[wibplus]

...................................................., I'd be tempted to series up 2 x 2s packs and use the existing mounts


Mark

IMHO that could be very dangerous. When LiPo batteries are charged, the charger will balance all the cells in a pack so that they are all of equal voltage. If you connect two (or more )packs in series, you are, in fact, creating a 4 cell pack which is not likely to be balanced and could make some of the cells overwork = overheat= go on fire and the chain reaction will destroy all the cells and anything around it.

Much safer to use a properly charged and balanced 4s pack

[CF-FZG]

IMHO that could be very dangerous. When LiPo batteries are charged, the charger will balance all the cells in a pack so that they are all of equal voltage. If you connect two (or more )packs in series, you are, in fact, creating a 4 cell pack which is not likely to be balanced and could make some of the cells overwork = overheat= go on fire and the chain reaction will destroy all the cells and anything around it.

Thanks for pointing that out   I've edited my post to clarify the issue

[RaaArtyGunner]

The 2s, 3s, 4s etc works like this :

1 single lipo cell = 3.7volts
2s means 2 in series = 7.4 volts
3s means 3 in series = 11.1volts  etc.etc.

You can also get e.g. 3s2p which means 3 cells in series and 2 in parallel which would boost the amps per hour rating.

You can get almost any combination of series and/or parallel to suit various voltages or amperage.

Hope this helps.

Just to make sure I am following it, that in the example if it was a 1 amp battery I would have a 11.1Volt 2 amp hour battery

[triumphjon]

the huntsman31 hasnt been fitted with any battery mountings , they are currently laying loose in the bottom of the hull !

[CF-FZG]

Just to make sure I am following it, that in the example if it was a 1 amp battery I would have a 11.1Volt 2 amp hour battery

No, if you had a 3s2p 1000mAh pack then it would be a 1A pack.

Years ago it was the only cheap(ish) way of getting packs over about 2000mAh, as the cells only went up to aboput 1500-1800mAh, to get a 3s 2200mAh pack they wrapped 2 x 3s 1100mAh packs together to give the 2200mAh.  As the battery chemistry has improved so much over time, they're mostly only used nowadays for REALLY big packs.


Mark.

[CF-FZG]

the huntsman31 hasnt been fitted with any battery mountings , they are currently laying loose in the bottom of the hull !

4s pack it is then