The Association of Model Submariners.

Would you like to react to this message? Create an account in a few clicks or log in to continue.

* THE FORUM FOR ALL THOSE INTERESTED IN BUILDING AND OPERATING MODEL SUBMARINES *



Join the AMS - Registered Forum users can become members of the AMS and it's free ...... To join send an email with your name , address and phone number to amstreasure@googlemail.com


For a guide to past events see the "Shows and Events" section.

Who is online?

In total there are 3 users online :: 0 Registered, 0 Hidden and 3 Guests :: 1 Bot

None


Most users ever online was 180 on Tue Nov 05, 2019 6:03 am

Latest topics

Statistics

Our users have posted a total of 11474 messages in 1887 subjects

We have 935 registered users

The newest registered user is geofrancis

2 posters

    Simple, elegant voltage shut off - Lipo protection perhaps?

    david f
    david f
    AMS Treasurer

    Posts : 2187
    Join date : 2010-11-10
    Age : 71
    Location : Cumbria

    Simple, elegant voltage shut off - Lipo protection perhaps? Empty Simple, elegant voltage shut off - Lipo protection perhaps?

    Post  david f Wed Feb 15, 2012 8:53 am

    A rather interesting link from John Main of C for Microcontrollers.

    http://www.best-microcontroller-projects.com/rechrgbatprotect

    Let us know if you use the circuit principle. I already use a MOSFET in a slightly similar way as an on/off switch (Triggered by magnet and reed switch.)

    David
    johnrobinson
    johnrobinson
    Guest

    Posts : 97
    Join date : 2011-06-10

    Simple, elegant voltage shut off - Lipo protection perhaps? Empty LIPO PROTECTION PERHAPS LOL

    Post  johnrobinson Wed Feb 15, 2012 7:39 pm

    HI David
    Problem with lipos is you need to monitor each cell in the pack because one cell will always go down in voltage first, you should not really take a cell down below 2.95V or you risk damageing the cell. The circuit that you showed will just monitor the hole pack and that is not the way to do it.

    If you had a 3 cell pack of lipos just say 1 cell was at 3.5v and the next was at 3.5v but the last cell was at 3v the 3v cell should be switching the power off to speed controller or what ever but if you put 3.5 and 3.5v together would make 7v plus 3v for the cell that should be turning the power off add voltage up it comes to 10v but if you carried on discharging pack down to 9volts the cell that was at 3volts when the pack voltage was at 10volts by the time it got to 9volts would now be damaged and that is how you would slowly cream cracker a lipo pack. This is just the basic idea that's why it is the best thing to monitor all cells in the pack, say you went to 10 cells now gets worse and becomes more important to monitor the cells
    SUB JOHN
    david f
    david f
    AMS Treasurer

    Posts : 2187
    Join date : 2010-11-10
    Age : 71
    Location : Cumbria

    Simple, elegant voltage shut off - Lipo protection perhaps? Empty Re: Simple, elegant voltage shut off - Lipo protection perhaps?

    Post  david f Thu Feb 16, 2012 9:06 am

    Hi John,

    In a perfect world it would be best to monitor each cell but it can make it much more complicated.

    I think you are speaking more of aircraft applications - many cells and drawing very high amps.

    The lipos I have used in subs for several years are only 3 cells and I only draw about an amp. In these circumstances I suspect you don't get big voltage differences between cells and I always balance charge them. I also don't push my luck and sail for too long (I have never had a low voltage alarm.)

    So I think in the absence of anything else this type of circuit would give your Lipo a good level of protection.

    David

      Current date/time is Tue Oct 19, 2021 2:35 am