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  1. #181
    Co-Pilot BobH's Avatar
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    Asgard,

    The LiPo battery I've got is a Haijiu HJTX4L-FP-1, which I believe is a sort of 4 amp hour battery. It may not be strong enough to start the engine on its own, but I've got two of them, so I may fit them in parallel. Each one weighs in at 460 grams, so even with both of them fitted they'd be much lighter than a lead acid equivalent.

    I've just been looking up the spec for the LiPo battery I've got, and came across an advert on Ebay for them. In amongst the blurb I found the following quote;

    "Easy charging - any standard 12v motorcycle battery charger can be used with Lithium Ion Batteries."

    So, the question is can I use any modern motorcycle reg/rec for charging the battery, and if so, would something like this do the job?

    https://www.ebay.co.uk/itm/Kinroad-1...gAAOSwSxZdUy6f


  2. #182
    Co-Pilot Antoni's Avatar
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    https://earthxbatteries.com/engine-c...hium-batteries

    That article has some oversimplifications and some downright errors. All the same it's a bloody good attempt to demystify the subject.

    The Key West reg reg/rectifier is superior to anything Rotax have ever supplied. I'ts not been manufactured for many years.

    There is more than one type of lithium cell/battery of cells. They are all particular to a greater or lesser extent about how they are charged and discharged/used.

    And, if you simply string them all together into a battery of cells, one cell is certain to reach full charge during charging before the others; one of them just has to get there first. After that point it will be overcharged while the charge system is trying to bring the whole battery's "terminal voltage" up to what it should be.

    In the oldest days it just didn't matter how much you overcharged an original type lead and acid cell. The extra energy was easily absorbed by the act of chemically separating water by turning it into hydrogen and oxygen [or other mechanisms which are based on dissipating overcharge energy as heat]. It takes a hell of a lot more charge energy to create these two gases than it would to simply heat the battery or even evaporate that same water - and that is why charging system designers a long time ago could comfortably rely on telling the user to add more distilled water as and when.

    Now, there has to be a monitoring system in a battery of cells which looks at each individual cell's voltage and diverts the battery charge current away from where it would be dangerous if all currents through all the cells were left equal.

    With the enormously higher power densities of modern cells comes a much higher level of care and feeding. Ask Boeing.

    As you will have noted this epistle is long on opinion and short on fact. I hope I won't have to put my tin hat on and crawl under my lathe.
    Last edited by Antoni; 20-09-19 at 11:01 AM.
    "The single biggest problem in communication is the illusion that it has taken place" - G.B.S.


  3. #183
    Co-Pilot BobH's Avatar
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    Antoni,

    As I am rubbish at electronics, your opinions are probably much more informative than most of the 'facts' I've read about LiPo batteries and their chargers.

    Just to let you know, I've ordered up a couple of cheapo Chinese reg/recs, as shown in the link I put in my last post. These are five wire items. The five wires are;

    Yellow: - AC input from single phase generator
    Pink: - Neutral AC input from single phase generator
    Red: - 12v DC output
    Green: - Earth
    Black: - Load monitor (has to be connected to the switched side of the ignition so that it can monitor the load on the system)

    These units are rated at 110 watts input, so I may need to use two of them in parallel to spread the 170 watts output from the Rotax generator. I'm hoping that one or both of them in parallel will be able to keep my Haijiu LiPo battery charged, but being ignorant in these matters I don't know if you can use two reg/recs in parallel like this, or whether they'll cook the battery.


  4. #184
    Trainee Pilot tomshep's Avatar
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    I ran the Aliant battery and it became very very hot, swelled up and then went open circuit, , having destroyed the trim display chip and the fuel computer on the way due to the spiky stuff from the regulator despite a 10 ohm 50W resistor across the supply in parallel with a very expensive capacitor rated to 200Volts. (I do this stuff for a living!)
    My advice to Bob is to throw the regulators away. The unit for a VT600 Honda costs around 12. it is designed for a 370 Watt alternator putting out 26 Amps. It has three yellow wires and any TWO can be used for the Rotax's 150 Watt alternator, reducing the maximum current by a third.(>16A) Measure the voltage developed at maximum RPM and if greater than 14.4 Volts, put a 20A 50V rectifier diode in series with the output of the regulator and connect the battery to the other end of that. Fit a 22000 microfarad cap across the output; 25 Volt will do just to ensure that there is no high frequency filth getting to the battery. Lithium batteries are light but need careful management. AND MAKE VERY SURE THAT ALL YOUR EARTHS ARE CLEAN TIGHT AND CLOSE TOGETHER!

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  6. #185
    Co-Pilot goldrush's Avatar
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    Quote Originally Posted by Antoni View Post
    https://earthxbatteries.com/engine-c...hium-batteries

    That article has some oversimplifications and some downright errors. All the same it's a bloody good attempt to demystify the subject.

    The Key West reg reg/rectifier is superior to anything Rotax have ever supplied. I'ts not been manufactured for many years.

    .
    My understanding is that the Key West regulator IS still manufactured and IS still available, although probably not by the original company.
    https://www.aircraftspruce.com/catal...tregulator.php

    Please remembert that the chemistry used in for example the LiPo and LiFePO4 etc batteries are totally different.. what suits one does not always suit the other!!.. and as Boeing found out LiPo battereies can and do get VERY hot and catch fire if everything is not 150% to their liking
    LiFePO 4 chemistry is somewhat more foregiving.
    Last edited by goldrush; 20-09-19 at 16:58 PM.
    Wally Hayward

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  8. #186
    Co-Pilot BobH's Avatar
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    tomshep,

    I've followed your advice and just bought a regulator for a Honda VT600. My only question would be what do the various wires connect to? There are three black wires, which I assume are the inputs from the generator. Then there are four other wires. Of these two appear to be red with a black stripe, and the other two appear to be black with a white stripe.

    VT600 regulator.jpg

    I just found a wiring diagram for the VT600 and it seems that the output wires are doubled up. So the two red and white wires are the same, and the two black and white wires are the same. In which case all I need to do is connect one of the red wires to the positive terminal of the battery through the ignition switch and a 30 amp fuse, and one of the black and white wires to the negative terminal of the battery. There's no extra wire for monitoring the system load, so I can only assume that something in the regulator is able to sense when a load is applied via the red wire and automatically responds.
    Last edited by BobH; Yesterday at 01:08 AM.


  9. #187
    Trainee Pilot tomshep's Avatar
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    Yes, the paired wires are parallelled so that the connector blades are not running over their rated current so you should solder each pair of the same colours together. Use any two of the yellow ones for the input and tape off the third one. The load sensing is largely done inside the regulator because it knows the voltage and current it is supplying and regulates it accordingly - it is, after all called a regulator!
    You are using a pair of parallel 4 AH batteries which in Lithium terms is very much frowned upon. The principle is that no two cells are alike. (My firm uses them in a life critical application where we throw many cells away, new because they will not balance. As a result, Poole has bicycle lights that can send morse code to the ISS.) as one cell is fully charged before the other, it is destroyed by the overvoltage needed to charge the second one. I plan to buy a grunty one for the Rans but suggest that a 12 A/H unit would be the minimum fit for a 447. Nigel will, of course know what the starter needs, I think it was 10 A/H.

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  11. #188
    Co-Pilot BobH's Avatar
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    tomshep,

    I don't want to use both my LiPo batteries, but I don't know if just one of them will have the power to turn over and start the SCDI 447 with the M5? It might do, as I can use just one of them for starting my Briggs and Stratton 5hp engine with no problem. However, if using the batteries in parallel won't work then that begs the question of how do you determine what is the lithium equivalent of a 12 A/H battery?

    According to the AllBatteries website, the correct batteries for starting a Rotax 447 engine are listed on this web page; https://www.allbatteries.co.uk/aircr...436/447ul.html

    As you can see, the cheapest LiPo type battery listed is 129, and is a 4,6 A/H battery. It is a Lithium Iron Phosphate battery, or LifePo4. I'm not sure what my Haijiu battery is, whether it's a LiPo, or a LifePo4, but I think it's also rated at around 4 A/H.

    Incidentally, my reasons for wanting to fit a Lithium battery instead of a lead acid one are twofold.

    1. I want to keep the starter cables as short as possible, which means mounting the battery just behind the firewall, but that will make the nose heaviness even worse than it currently is, so I need a very light battery.
    2. The lithium batteries I have are very light, each one weighs 460 grams, so they're ideal for mounting just behind the firewall, and can be mounted lying down without any adverse effect.

    So would I gain anything by spending 129 on a new LifePo4 battery when I already have two of very similar A/H spec?


  12. #189
    Captain Randombloke's Avatar
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    I'm trialling a LiFePO4 battery on my XJ900, I can stop at any time, and get off. If successful it's the same one as is allowed for the Skyranger.

    The proviso with chargers for those batteries is that if you are going to use them, they must not have a rescue or de-sulphate type mode or this will trash the LiFePO4 battery.

    I bought a dedicated charger for my LiFePO4 battery.

    They are now a comparable cost with the best high tech lead/acid ones, AFAICT. YMMV.

    Big thanks to Tom for technical details.
    Steve U.
    PG, HG & microlights
    "Weekend bimbler, day to day car driver & genuinely undeserving Southern oik who has never done anything of any worth"


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