Charging Lipo batteries

[Julian Murch]

I have a query about charging Lipo's having purchased an Overlander 25c 1300mAh battery and a E-flight charger to go with it. The charger is rated 11.1 -15 vDC input and 0.80a output. It has red and black crocodile clips and a round 12v input.

My query is as follows. I have a 12volt charger from an electric drill with a compatible round 12 volt connector. This is rated 230v - 50hz 120mA input and 12v 500mA 6va output. I also have a 12volt transformer from an old train set rated at 12 volts 2 amp output.

I would like to set up all of the radio and servo kit with the motor before I finish the fuselage but thought I should just ask if either of the above will be suitable to use here.

[Simon Chaddock]

Julian

First you must make sure that the round 12 connector from any source has the correct polarity (+ and -) for your LiPo charger before you connect anything. The charger should be marked to show what is required.

The drill charger is a bit small (0.5A) for your charger which requires 0.8A. As long as the = and- are the right way round on the 12 v connector it should work but it could take longer to charger the LiPo.

The train transformer has sufficient power but does it have more than one output? Is the main output reversible so the train can go either way?. As stated above the 12V connector must have the + and - the right way round.

Any fixed socket on the train transformer could be AC and would be of no use for your charger.

Remember a LiPo does not like to be left fully charged for long periods (weeks) and neither does it like to be run down below a certain cell voltage. For 'bench testing' (do not fit the prop!) you will only use a small amount of its capacity so it only needs a small charge or maybe none at all..

[Simon Chaddock]

Duplicate 

Edited By Simon Chaddock on 13/03/2019 10:15:25

[Julian Murch]

Thanks for that I tried to upload a photo but could not do it. See Ebay where there are some for sale.

It does not have any form of controller just plus and minus outlets at the rear so hopefully will be suitable.

[Ronaldo]

Along with my pro peak 12v PSU's, I also use a camping/caravan 240v to 12v convertor as a spare PSU when needed. If you are confident enough to wire the lipo charger leads into a 'cigarette lighter' type plug, this may be a good inexpensive alternative to use.

**LINK**

[Nigel R]

If you can confirm the train transformer is 12V DC and get the round socket wired right, it will be ok.

Although obviously you will not be able to charge at a couple of amps, max.

Laptop power adaptors work well here too, if you can find one with a 15V DC output. Or, there are small units made for this purpose -

**LINK**

[Julian Murch]

After some delay I am almost ready to complete the model. As well as the transformer I mentioned above I also have one for a 12 volt coolbox. Testing both with a multimeter however the train one shows 15 volts and the coolbox one 13.75 volts. Is this within the range acceptable for a Lipo ?

[Simon Chaddock]

Julian

The acceptable voltage range is for the charger not the LiPo. As long as the pos and neg are the right way round the tool box transformer should be ok.

The charger will supply the voltage required by the LiPo and will charge it in a particular way to make sure each cell exactly reaches the required full voltage level.

LiPo are VERY sensitive to how they are charged which is why they must only be charged using a LiPo charger.

[Julian Murch]

When in doubt - read the instructions !! I should have realised that the question is whet is the balance charger's requirements. It states input at 11.5 - 15 v dc so both are within the range. Thanks for the help.

[Alan H]

You need to make sure that the output from a train transformer or similar device is smoothed (typically with an electrolytic capacitor) and not just half or full wave rectified unsmoothed DC. The charger will not work properly and might be damaged by an unsmoothed power source.

[Julian Murch]

Not sure I understand what that means or how I will be able to tell if this is the case. Train transformer is probably 50 plus years old so probably not ? How about the cool box. It was made for Halfords and is marked 'euro converter'

I will try to upload a photo of the lable as there are some symbols shown.

[Julian Murch]

After some exploration I have managed it !!

[Nigel R]

That would do it, I imagine.

Another route is to look at a generic 15V laptop power supply. They are not very expensive.

e.g. here - a 60W supply on ebay

The only gotcha with laptop supplies is that many are 20V (ish).

[Alan H]

As the Halfords PSU is a switching regulator it should have a fairly smooth output and is likely to be OK. Laptop power supplies are also switching regulators and should be fine. The old train transformer probably has an unsmoothed output and I would not risk it. The only way to tell for sure is to look at the output with an oscilloscope and see if it is a fairly smooth voltage or a series of humps at 50Hz or 100Hz. I think you should be OK with the Halfords unit.

[Geoff S]

I use a server power supply which is 12v and capable of sourcing up to 47 amps. They're quite cheap, too. I got mine form a firm advertising them on eBay for less than £20 several years ago. I think they're replaced as a matter of course as part of the maintenance schedule. I regularly charge 3 LiPos at 4 amps each with my iCharger Duo and Graupner Ultramat 16 both connected to the power supply.

There are a few links to be made and a bit of wiring to some suitable connectors (I use 4mm sockets) but they're very good value and far better quality than a switched mode power supply from Halfords is likely to be.

Geoff

Edited By Geoff Sleath on 26/09/2019 21:56:07

[Julian Murch]

Thanks for all the advice here.