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    LiPo Batteries and Charging problems
    by StuartE πŸ‡¬πŸ‡§ ( Chief Petty Officer 2nd Class)
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    26 Posts 25 Replies 2 Photos 38 Likes
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    dave976
    Master Seaman
    πŸ“ LiPo Batteries and Charging problems
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    Country: πŸ‡¬πŸ‡§ United Kingdom
    Online: 19 hours ago
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    Hi Chris
    Apparently not on this Hydra15 system. It does recognise the type of battery based on the battery voltage which is not ideal as a discharged or faulty cell battery may result in the wrong type. Balanced and fully charged batteries should not be at risk.
    I do believe we have established that LiPos should be:
    Fully charged, preferably with a balanced charger, before use;
    Not discharged below the recommended safe voltage (3v - 3.5v as per manufacturers specs, preferably by an ESC that will reduce the current output;
    Stored at the recommended voltage between usage;
    Not mentioned but important:
    Not used or charged if the battery temperature is above room temp or the battery is damaged or shows signs of "puffing".
    Hopefully this will help Stuart and others new to LiPo batteries to sail safely
    Dave
    2
    ChrisF
    Chief Petty Officer 2nd Class
    πŸ“ LiPo Batteries and Charging problems
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    Country: πŸ‡¬πŸ‡§ United Kingdom
    Online: 6 hours ago
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    Good stuff Dave. I know it's generally accepted that 3.0v is the cut-off for LiPos but some manufacturers state a higher voltage, like I said for the Giant I use it's 3.4v per cell so I set the ESC at 7.0v for a 2S.

    Do you know if it's adjustable on the MTronic?

    Chris
    dave976
    Master Seaman
    πŸ“ LiPo Batteries and Charging problems
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    Country: πŸ‡¬πŸ‡§ United Kingdom
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    Hi Stuart
    I looked up the literature on the ESC and it is LiPo friendly. I spoke to Mtronik today and confirmed it is LiPo friendly in that the battery is identified when connected and a cut off voltage of 3v per cell applied. In your case 6v. Once this voltage is reached the motor receives reduced power, which was the slow down you experienced. As we have already discussed you believed the batteries were charged and ready to go when received. Possibly the battery was also unbalanced and that is the cause of the demise. The ESC measures the overall voltage so one cell 3.5v and the other 2.5v maybe. With your new charger I would expect the new charged battery to give you no problem and a timed run would ensure you stop sailing before the cut off point is reached.
    Dave
    1
    dave976
    Master Seaman
    πŸ“ LiPo Batteries and Charging problems
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    Country: πŸ‡¬πŸ‡§ United Kingdom
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    Hi Stuart
    Glad to hear you have bought a Giant Power charger and it has successfully charged your new battery.
    The two old batteries are not recoverable as they have been in a discharged state for too long Please do not even consider trying to revive them as due to the time they have been in such a low discharge state the internal chemistry will have changed making the batteries very unstable if you attempt to recharge. You were lucky they did not cause problems when you did a fast charge. Disposal is the only option you should now consider.
    As other have said you do need something actually on the boat monitoring the battery voltage and warning you when it approaches the recommended low state. Modern batteries seem to recommend 3.5 volts as the safe limit and I have used this on my Sea Queen without problem. I can actually see the individual cell voltages on a screen on my TX and as soon as the voltage nears 3.6v on any cell I bring the boat back a slow speed as the voltage drops very quickly once the cells are depleted.
    Many modern ESC are LiPo friendly and offer a set up you can set to the recommended cut - off, they also reduce the power when the voltage is too low. There are also warning devices you can fit that emit a loud noise to warn of low voltage. They work fine but may be difficult to hear at a distance in a noisy environment.
    At full throttle using an 11.1v LiPo and drawing 27amps my Sea Queen lasts between 15-20 mins so you could use a stop watch to monitor your time on the water. As watts is the product of the voltage and current, using 7.4 volts would result in higher current draw and a shorter run time.
    Another useful piece of equipment is a Wattmeter that will measure your current draw whilst you hold and run the model in water. This will give you an indication of the max draw as the prop will draw less current when in motion.
    What motor and prop do you have installed?
    Dave
    2
    StuartE
    Chief Petty Officer 2nd Class
    πŸ“ LiPo Batteries and Charging problems
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    Country: πŸ‡¬πŸ‡§ United Kingdom
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    Hi Chris,

    The boat is in my harbour as I ran a build blog here on this site for it over a year ago. Fairey Huntsman - Roaslie.
    The ESC I used was an Mtroniks G2 Hydra15, which I dont think has a cut-off system, but I'll check the instruction booklet or look up on the website.
    Rowen
    Lieutenant Commander
    πŸ“ LiPo Batteries and Charging problems
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    Country: πŸ‡¨πŸ‡¦ Canada
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    Do not think your batteries are scrap. Think worth seeking out advice on recovery as have done it successfully.
    Not familiar with your Huntress model; but on my 34" long brushless, triple screw Brave Borderer running on a 5000mAh 3S battery running at speed gives under 60 mins operating duration.
    If you operating at near full speeds your run time is not unreasonable.
    Do recommed using a battery discharge warning though. They work well, protect the cells and allow for max. duration operation.
    Glad you are getting the hang of Li Pos, they do offer many advantages in higher speed models.
    1
    ChrisF
    Chief Petty Officer 2nd Class
    πŸ“ LiPo Batteries and Charging problems
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    Hi Stuart

    Great that you bought the Giant charger. Yes those two batteries are scrap! And your new one is in danger of going the same way as you can't rely on judging when the performance is dropping off - by then the voltage may well have dropped too low. You were lucky that it was still 3.2v per cell. Your particular batteries should tell you what minimum voltage is acceptable. I use Giant Power and they state 3.4v per cell so I set the cut-off at 3.5v

    As Nonsuch says ideally you need an ESC that has the facility to set a low voltage cut-off. I take it you bought the boat ready built with the ESC etc. already installed? A low-voltage buzzer as already mentioned is another option.

    Be interested in a photo of the boat, I'm a big Fairey fan, but more importantly, can you provide details of the ESC so that we advise on the suitability of it or not for use with LiPos.
    2
    Nonsuch
    Chief Petty Officer 2nd Class
    πŸ“ LiPo Batteries and Charging problems
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    Country: πŸ‡¬πŸ‡§ United Kingdom
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    I must confess to having no experience of electric powered boats at all. I do however have 15 years of flying LiPo powered fixed wing 3D and helicopters. I have always used a balance charger and have never had an issue with either 2S or 3S LiPo.
    What I find disturbing is you say that you "noticed a drop in performance" so brought the boat back in. That suggests that you are not using LiPo compatible ESCs as these have low voltage protection, shutting off or reducing power as a warning of low voltage. Shutting off and then reapplying the power from the transmitter then accesses a "power reserve" to get the model back safely before damage to the LiPo's occurs.
    If your ESC is not for LiPo, that's the problem, not the charger.
    3
    StuartE
    Chief Petty Officer 2nd Class
    πŸ“ LiPo Batteries and Charging problems
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    Country: πŸ‡¬πŸ‡§ United Kingdom
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    Hi all......an update!
    I bought the GIANT battery charger as has been suggested and connected both dead LiPo's, one at a time. The first one connected gave a cell charge of 0.88V and 0V and the second 1.03V an 0.34V.
    I first tried a Balance charge on each of the batteries and the Charger responded immediately with a Voltage error. I then tried a fast charge and after 25mins, the battery cells would only charge to 1.3V and 0.8*V. neither battery would charge any higher.
    So am I right to assume they are now both unchargeable and disposable?
    I did buy another 4000mH 7.4V 2S and that charged nicely on balance charge to 4.1V from 3.4V and used it for about 30mins in the Huntsmann. I noticed performance drop and quickly bought the boat back.
    Once at home, I put the battery on the charger and both cells were down to 3.2V, so charged them to storage charge before putting away for next outing.
    Thanks for all your help guys!
    1
    Rowen
    Lieutenant Commander
    πŸ“ LiPo Batteries and Charging problems
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    Country: πŸ‡¨πŸ‡¦ Canada
    Online: 2 hours ago
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    I do much the same.
    Always use a cell discharge monitor whilst using a Li-Po. I usually set the warning to a minimum of 3.2 volts per cell.
    After use, recharge to storage setting. The evening before use fully charge.
    Always take the charging precautions and I never charge at more than 1.5 Amps.
    Have an intelligent balance charger and am quiet satisfied with Li-Po batteries.
    2
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