edwalker Posted March 20, 2016 Report Share Posted March 20, 2016 One of Santa's presents this year was a pair of LiFePO4 batteries for the Phoenix. I spoke with Jim, and he approved the following replacement: http://www.batterytender.com/Batteries/480-CCA-Lithium-Engine-Start-Battery.html They were on sale for half price, so I thought I'd give them a try. I'm now out 4 months and I've been very pleased with the performance so far. I cannot tell any difference other than the ability to get more duration out of the forward battery which is my soaring battery (rear saved for restart). This is a drop in replacement, kind of.... the battery is a tiny bit longer in length, requiring a little sculpting of the battery box foam, but Jim gave me very clear instructions. Basically, I took a wood chisel/knife and took out the foam from both short ends of the battery boxes and then slipped the battery in. It's also a bit shorter in height, so plan on using some of the supplied foam blocks to keep it a bit higher in the box. The real trick is wiggling your way to the back of the plane around the parachute box to do the back one. Plan on a visit to your Physical Therapist after you're done if you're over 30. The process is the same - unhook the webbing at the back of the baggage area and do your best. It's not difficult, just awkward. One tip - these are motorcycle batteries with nut and bolt connectors. The nut is in a little box, and it can easily get out and get lost. I used a small square of foam with adhesive backing to trap the nut in position so that all I had to do was put the screw in and let it find the nut. Make sure you use the right kind of charger - this is a different charging paradigm. So far so good. I'll let you know how it does over the Spring to Autumn flying season. Quote Link to comment Share on other sites More sharing options...
mikeschumann Posted March 20, 2016 Report Share Posted March 20, 2016 If these batteries use a different charging paradigm, how do they work with the generator and charging system built into the ROTAX engine? Quote Link to comment Share on other sites More sharing options...
edwalker Posted March 21, 2016 Author Report Share Posted March 21, 2016 Hi, Mike - Seems to be ok, and I was told it would be. Here's what I was told by the battery engineers at Starkpower.com. The AC charger issue is that SLA batteries have a 3 stage, temperature sensitive changing voltage paradigm that moves the batteries through charging levels with terms like charge, float and maintenance. SLAs slowly lose charge if not maintained over time, so these chargers are designed to remain connected. The LiFePO4 batteries use a different AC charger with a constant voltage process which maintains a rather flat current curve that falls off rapidly at the end of the charging cycle and then goes to zero, encouraging the charger to turn off. If you catch the last few moments you'll see the battery voltage remain high and the current drops off over a few minutes to zero and then the charger goes to sleep. You're correct in worrying that an alternator might pose problem, however the LiFePO4 cells in the box are connected to a battery management system which handles this for in-flight charging, but it is not designed to ward off the continuous changing current and voltage of a 3-stage AC charger. In other words, there doesn't seem to be a problem with in-flight recharge (the BMS handles that), but continuous use of a 3-stage SLA charger isn't recommended. Having said that, the SLA chargers can be used in a pinch if monitored. I think the worry is about walking away and leaving the LiFePO4 on a maintenance charge in between flights. Quote Link to comment Share on other sites More sharing options...
Martin Stepanek Posted March 23, 2016 Report Share Posted March 23, 2016 Hello dear friends! That is interesting... I fully agree that it is not easy to access to battery box - sorry for that. What is the weight difference? Batteries are normally installed behind CG so if is new battery significantelly lighter is good to check new CG position. LiFePO is normally very safe system (definitely much better than Li-Po, probably also better than Li-Ion). If you don´t recharge with hign current I beleive that there is no risc of fire. I have one sample of LiFePO battery here and weight is only a bit over 1 kg = great! It is able to start Rotax engine without problem, but because we don´t use Dynon we have very low energy consumption during gliding. It means that we can´t compare our and your conditions. So - every experience is very welcome :-) Best regards! Martin Quote Link to comment Share on other sites More sharing options...
Gfeldman Posted March 30, 2016 Report Share Posted March 30, 2016 Jim installed a LiFe as one of the 2 batteries in my Phoenix when it was new in December and after 22 hours have had no problems. George Feldman Quote Link to comment Share on other sites More sharing options...
Registered Eric Greenwell Posted March 30, 2016 Registered Report Share Posted March 30, 2016 14 hours ago, Gfeldman said: Jim installed a LiFe as one of the 2 batteries in my Phoenix when it was new in December and after 22 hours have had no problems. George Feldman Was that for the rear battery, and primarily used for engine starting? Quote Link to comment Share on other sites More sharing options...
Gfeldman Posted March 30, 2016 Report Share Posted March 30, 2016 Eric, It is the front battery and I alternate batteries every flight, so each battery is used for everything half the time. G Quote Link to comment Share on other sites More sharing options...
Registered Eric Greenwell Posted March 31, 2016 Registered Report Share Posted March 31, 2016 What is the advantage of having one of each type of battery (SLA and LiFe)? Quote Link to comment Share on other sites More sharing options...
Gfeldman Posted April 4, 2016 Report Share Posted April 4, 2016 The LiFe is untested in this plane so I thought it wise to keep one battery SLA. Quote Link to comment Share on other sites More sharing options...
sheridan9sc Posted April 15, 2016 Report Share Posted April 15, 2016 I have replaced the front battery with the Battery Tender LiFePO4 and left the rear battery intact. On long flights Jim suggested that I select the rear battery so that there was no issue with overcharging the LiFePO4. So far, no problems but haven't determined endurance for soaring flights with the Dynon and transponder on. Quote Link to comment Share on other sites More sharing options...
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