Lithium batteries

[TimF]

We have started a transition to the use of Lithium (technically, Lithium Iron Phosphate or LiFePO4) batteries in the Club gliders. We are doing this because we have found that the existing Lead Acid batteries are not surviving more than about 18 months and several instances have occurred where a battery failed part way through a flying day. A battery going flat is likely to cause damage to the internal cells and this may be the cause of their short life.

Lithium batteries have been around for many years and we now think it is worth trying them in our gliders. They have the advantage that they are considerably lighter than Lead Acid types (typically around a third of the weight), and they contain electronics to protect the internal cells. However they cannot be charged with a Lead Acid battery charger.

Things to note:

a) We are starting the transition with three Lithium batteries. These are clearly marked on the top surface, and you will notice they are considerably lighter. There is one with a black case and two with green cases. The Lead Acid batteries all have grey cases. It is recommended that only the green Lithium batteries are used in the K21 as they have the highest capacity. The black Lithium battery is best used in the Alliance (once modified - see below) or Astir as the electrical demand is less in these gliders.

b) The charging station in the workshop has been upgraded to charge both Lead Acid and Lithium batteries. The two types of battery are wired differently so that only the correct charger is used. The first three charging ports from the left can cater for both types of battery. These are clearly marked. If you plug a Lithium battery into one of the Lead Acid-only ports (the three on the right), it won’t charge (but it won’t cause any damage). The meter shows if the battery is charging. The charge current for Lead Acid batteries may up to 2.5 Amps and the current for Lithium batteries may be up to 1 Amp. We will upgrade more charging ports as we get more Lithium batteries. Note that when the red mains switch is turned on, both chargers for that port become active but only the correct charger is used.

c) Gliders are being modified to accept both Lithium and Lead Acid batteries. At the time of writing this note the K21 and the Astir have been modified. The Alliance needs to be de-rigged to modify it so that will not happen for a while. The DG505 will be modified as soon as it comes back from being repaired. A glider modified to cope with both types of battery will have a label placed near the battery tray indicating that either type can be used. If you plug a Lithium battery into a non-modified glider, none of the electrics will work.

d) In the case of the DG505 which has two batteries, a mix of Lead Acid and Lithium batteries will work (once it is modified). If you are not familiar with how to share the electrical load between the two batteries, please take the time to read the laminated card in the glider or ask someone who knows.

e) The Discus has its own dedicated pair of Lead Acid batteries - none of the other batteries will fit this aircraft - and so Lithium batteries will not be useable in this glider until further notice. Do not attempt to charge the Discus batteries using the workshop charging station – use the dedicated charger (red box) in the Office. More to follow on this in the next few weeks.


So please follow these guidelines:

• Only charge a Lithium battery in one of the first 3 ports from the left on the charging station. Connect (and disconnect) batteries only with the mains switched OFF. Observe that the meter shows a charging current when the mains is switched on (it may take a few seconds to show).

• Only attempt use a Lithium battery in a modified glider. Eventually this will mean any glider except the Discus.

• Get into the habit of switching the glider Master switch OFF after every flight to preserve the battery. There is no reason at all why a battery should not last all day. Remember; turn the K21’s Vario OFF first!


Any questions, please ask.

Tim Fox
Technical Officer

[Adrian]

Well done Tim - quite a lot of work in preparing the chargers and gliders to do this.

Geoff and I have two Lithium batteries in our LS8. They came with the glider in 2016 and were used for some time before that. When fully charged one battery will run the LS8 fairly heavy electrical demand, including the transponder, all day. Neither battery shows any sign of reduced capacity. The only time I have had to switch from one battery to another in flight is when we forgot to charge them.

While the Lithium batteries cost quite a lot more to buy than Lead Acid if these perform well then there should be an overall saving as the lead acid batteries don't seem to last anything like as long.

Adrian

[skylark4]

I too can echo Adrian's comments.

I run two Pbq 10a models on the Pilatus and can switch from No.1 to No.2 if needed, but, can report that this has never been necessary. They are the same size physically as the old Yuasa 7a and have endured extremely low temperatures for extended periods. I have never had any problems with them and believe that they have greater natural endurance than the old lead Yuasa types.

A good move by the club.

[TimF]

The Alliance has now been modified to accept Lithium batteries.

All our operational gliders (except the Discus) can now accept Lithium batteries. The DG505 will be modified to accept both types as soon a practical after we get it back.

Tim