LiPO Chargers

I recently bought a new LiPO battery and decided to measure its capacity on an electronic load. I was disappointed to find that the measured capacity was about half the manufacturers quoted figure. Further investigations showed that the problem was the charger. The charger type is an IMAX B6. Charging the LiPO with a constant current source delivered the full capacity from the battery. I’m wondering if my charger is faulty or if they are all like that?

Anyone done any measurements?

Battery is 2200mAh 3S type.

I also own an Imax B6, and I’m going out this weekend for a multiday activation with my 3s 1300 mAh Li ion battery. I always take a small lcd battery checker, so I’ll make a note at the end of each day. I can’t really offer anything more accurate. I use an MTR3b, for which a 360 mAh is more than enough for day trips. I haven’t used the big 1300 mAh battery yet, so I’m curious to see how it does.

I use a 3S 9000 mAh custom battery (balanced, made from individual laptop battery elements by a friend of mine) and I use this type of charger:
The battery is always full capacity charged and gives me many hours of activation in SSB with 10W from an Icom IC-703.

The ubiquitous IMAX B6. :slight_smile:
This is the most copied, cloned, charger in the world!
It started life as the Accucell6 (still sold by Hobby King) and morphed into the IMAX B6.
Probably 90% of all IMAX B6s are copies and not original stock.
The originals all have holographic label on the rear, and the SKYRC label on the front.
If you follow the RC forums, you’ll find that most of the clones are actually made in the same factory.
Where they differ is that they are not calibrated in the factory (that takes time and costs money).
The chances are that all you need to do is run through the calibration sequence as it appears that yours are finishing charge long before they are complete.
Google and YT are your friend…

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I was briefly optimistic when I read your reply.Sadly my unit does not show the calibration menu and attempting to reflash the MPU seems like a lot of hassle. LiPOs charge quite happily with CI-CV charging from my programmable power supply so I will stick with that I think. Thanks anyway.

For what it’s worth, my Li-ion battery charged up perfectly and held its charge well throughout the trip. As I write this, it still has 64% capacity remaining after 6 summits and 64 contacts. My Imax B6 does have the hologram sticker on the back and when I bought it from Hobby King the page said ‘Genuine’ at the top. Hobby King do also sell the copies, but the fact that they are copies is clearly indicated on the page. The only problems I’ve had have been with the batteries (LiFePo), never the charger itself.

I’ve never used LiPO batteries so apologies if this is nonsense. I’ve been put off these batteries because of the reports of them catching fire when charged. It appears this is due to using the wrong type of charger - are you sure your CI-CV charging is ok? Do you also have to ensure the cells are balanced?

I wouldn’t risk it myself. You should really monitor the individual cells to ensure that no single cell is ever over-charged or over-discharged. If you only monitor the overall voltage of the battery pack you can easily run into trouble if the cells get out of balance. But I’m sure you can get away with it if you’re careful.

Actively balancing the cell voltages is not essential for safety, but is a really good idea to get the most out of the battery. Excessive need for balancing is likely to indicate a weak cell and imminent demise of the battery pack.


You can make a simple LiPo charger that is CV and current limited using a few transistors and an LM317 regulator. You make one for each cell, so for a 3S LiPO you need 3 chargers. Keep the max current low and you can sleep peacefully. Balanced charging by default.

Sadly you can normally buy a super-gizmo smart charger from China for the less that the components cost :frowning:

My own LiPOs are charged with a slow charger that can take 4-5hrs to charge a 4AH pack. I have no evidence other than circumstantial but it seems that slow charging gives a long life. I know my two 2009 vintage packs don’t seem quite so zingy and full of zap than when they were new. But nearly 8 years use most weekends is good enough for me.

See this: SHDesigns - Lithium Ion Charger

Still very happy using this small and lightweight charger :slight_smile:

For less than 10 Euros, I didn’t bother making one myself.

It is slow (Imax is 1.5A), but as Andy says … maybe better for the battery life.
I charge a commercial LiPo 5800mAh pack with it, as well as several homebrew Li-Ion packs via the balancing wires (I have 2S 3S and 4S packs in use, and not just for SOTA, e.g. my bike lights are also powered from a 2S Li-Ion pack hi)
And it works on 12V in the car too, so I can charge while driving from one summit to another.

Luc - ON7DQ

(edit) : this was the latest pack I made, 4S2P, 20A car fuse built in, made from Dell laptop cells, estimated capacity 4800 mAh. It served all my operating with the KX3 at 15W (using the automatic voltage reducer) on 17 summits in EA6, and all 22 summits on my recent FH trip, easily doing 4 summits in one day without recharging.