This article first appeared in the August 2007 issue of RCM&E. Things have moved on a little since the article appeared and balancer plug converter leads are now available from most electric flight specialists and some distributors covering the four main Li-Po battery balance plug types you see pictured. The article went on to describe balancer units available at the time and I've omitted this section given that combined balancer-chargers now dominate the marketplace.
This article was prompted by threads and posts here on our website forum. A theme developed around the issue of Li-Po balancers and, more specifically, the incompatibility between plug types. This, clearly, is a problem all electric flyers encounter at some stage and an ongoing source of annoyance simply due to the huge variety of balance plug types found on Li-Po batteries. Anyway, this being the case I decided to have a closer look at the situation and the article you see here is the result. I've cast the net far and wide, spoken to people in the industry and surrounded myself with plugs and leads - these therefore are my findings and my grateful thanks go to Brian Collins at BRC Hobbies for his kind help with this article.
Chargers look at voltage and in doing so they look at the total pack voltage and effectively blast away (if you'll excuse the term) at the pack rather than the individual cells. Quite simply, then, a balancer unit or the balancer-charger itself holds back the voltage on the cells that dont need it. Generally speaking there are three ways of balancing a Li-Po. The easy way is to use a charger that does the balancing for you although a balancer unit can be connected between the charger and Li-Po battery (in-line) or it can be plugged into the Li-Po to act as a stand-alone unit during the charge process. In either case the balancers LED display should provide a visual indication as to whats going on. In-line balancers will usually cut off the charging process if a voltage problem is detected whilst a stand-alone unit will indicate problems audibly and await user intervention.
Its worth noting that a new generation of balancer chargers is starting to appear on the market and, as you'd expect, these do away with the need for a separate balancer unit. This is good news of course, although, if like me, you've already invested in a good Li-Po charger then you may not be able to justify replacing it just yet, so a separate balancer could be the only option.
Crunch time, and if youre an electric flyer you'll doubtless relate to what I'm about to say. It concerns connector plug compatibility or, if you like, incompatibility! Early Li-Po batteries (such as Kokams) often didnt even have a balancer connector lead, they simply had two power leads, just as youd expect to find. As the industry started to realise that the risk of cell imbalance needed addressing, so manufacturers started adding balancer leads, to which they attached a plug. Unfortunately a huge variety of different plugs started to appear and these varied between manufacturers and indeed brand names. The result is now a large degree of plug incompatibility leading to a good deal of confusion for electric flyers.
Brian Collins told me hed identified 17 different Li-Po balance connector plugs although thankfully this number can be pared down to just four main types that youre likely to find fitted to the vast majority of Li-Po batteries sold here in the UK.
Four plug types is really three too many, and when we add in a whole plethora of variations in battery pack wiring, not to mention discontinued plug types, then there is, at best, a recipe for confusion amongst flyers (not to mention retailers) and at worst, thousands of unbalanced packs across the land and a chance that at some stage, somewhere, an unbalanced pack will misbehave.
TAKING THE LEAD
Battery manufacturers have been very slow when it comes to producing converter leads for these although thankfully many electric flight retailers have now filled the gap and supply their own converter leads to go with the balancers and Li-Pos they sell. These usually retail for £1.99 each so there really shouldnt be a reason not to balance packs fitted with one of the four main connector types you see here.
Some flyers will tell you to balance your packs every time you charge, whilst others will suggest that balancing every half-dozen flights is sufficient. Then again, theres a case for monitoring the cells via a multi-meter and only balancing when you identify a need. This way, your cells may never go near a balancer. Me? Well I balance my packs at every charge - that way I've nothing to worry about.
This little piece is really just the tip of the iceberg as far as Li-Pos and cell balancing is concerned, however, for the average electric flight enthusiast (like me) I hope it has helped shed a little light on connector plug issues. If you have any opinions on the subject then join the debate on the forum - see you there......
By Tony Fransens
by Tony Fransens
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