AGM Leisure Battery

Discussion in 'Mech Tech' started by Adam W, Oct 9, 2019.

  1. Hello all. Everyone's favourite topic again :) Sadly the search function on the forum won't let me search for 'AGM' as its 3 letters and deemed unimportant, so another thread is born!

    So, there is a lot of chat from what I can see about having to use a low height leisure battery if mounting on the N/S of the engine bay, underneath the spare wheel well. Fair enough. But, as most batteries are the standard 175 mm wide, could an AGM battery not be simply mounted on its side? Obviously wouldn't want to try this with a flooded lead acid battery... There would be enough height to raise the battery up off the floor over the seam, and it would conveniently present the terminals inside the engine bay instead of under the wheel well.

    Anyone done this?
     
  2. mikedjames

    mikedjames Supporter

    Yes you can but your charging arrangements need to be specialised.
    The wet cell starter battery has a different on charge voltage to the AGM battery.
    The AGM is 0.2 volts higher than the wet cell. Means you will fizz the electrolyte out of the starter battery before the AGM battery is fully charged if you use a VSR. You would need one of those Ctek battery to battery chargers to bump up the volts ..
    Also..

    The AGM battery uses sealed internal build up of gas pressure to force recombining the hydrogen and oxygen back to water in an exothermic reaction. This can become runaway if while you charge it, it gets hotter than around 40 deg C..
    Then it vents, stinks the place out and becomes scrap metal.


    Life is easiest to match technologies. Use a small AGM starter battery with an AGM leisure battery, a VSR and a Stirling digital alternator regulator ( to boost and privide 4 stage charging off the alternator) and it would be brilliant.
     
  3. Thanks @mikedjames an excellent response! I had wondered about it, thinking that AGM charged slightly lower and slower than wet, but with the dynamo on there it seems there’s lots of risks that just using a wet battery would avoid so I think that’s the best option. My ctek will do agm, so maybe when they both die again I can do it then. Hopefully I’ll have installed an alternator by then too!
     
  4. What’s your thoughts on using lithium batteries Mike?
     

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