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  1. Andrew Lenton
    May 30, 2019 @ 15:31

    H I do not agree with “Once they reach the 12volt mark they are flat and you should not use it anymore as damage will occur”

    A fully charged 12 Volt Leisure battery, will very quickly fall to 12.5V or less in a hour or so of moderate use, at 10.5V it would be considered fully flat. All Leisure batteries like to be kept close to full charged, once charged their shelf life is very long when new. I would say you need to start thinking about recharging at 11.5V. A 200 Watt solar panel will allow you to wild camp all summer, providing you have an MPPT charger, or at least a PWM charger. A DC current clamp meter is the best way to find out where the power is draining away.


    • Paul Fabrizio
      May 30, 2019 @ 21:24

      A while back I would agree with your figures but generally 12 volts or under is regarded as flat. These figures are not from me but from battery manufacturers, some retailers have the same information.
      You can run a battery much lower but there will be damage to the plates and will be very difficult for the battery to recover shortening the life of the battery.
      Of course the most manufacturers recommend a 50% depth of discharge (DoD) which is actually around 12.4 volts. Just remember these voltages are measured when the battery has no load.
      So when the battery is connected to the motorhome or campervan you sort of have to guess as the voltage will be lower under load which makes battery management even more of a challenge.
      I have tried to explain batteries a bit more in this blog post;
      Here is some info from Yuasa Batteries


  2. Andrew Lenton
    May 30, 2019 @ 22:46

    Hmm ???? it sounds like to me the manufactures do not want to admit the fact the full deep cycle batteries only have 50 to100 cycles. So at 30% discharge they want you to recharge so to extend the life.

    They should then reduce the advitised AMP Hour capacity as 32Ah not 110AH.

    My background is submarine lead acid cells we only came up to recharge when we had to




    • Paul Fabrizio
      May 30, 2019 @ 23:24

      I think you have hit the nail on the head. The sweet spot for wet batteries seems to be about the 30% mark to get the number of cycles advertised.
      The only batteries that seem to get round this are the lithiums which can be discharged 80% for thousands of cycles. They are about a grand to buy so you have to use your batteries seriously to get your moneys worth.


  3. Carol
    November 23, 2019 @ 08:35

    Are my leisure batteries(2) dead /need replacing. It’s winter .. I have no electric hook up. But 2solar panels. I am stationary waiting for other work to be done on my Motorhome and in the wait..I am living on board Last night I charged the battery by running the engine .. after about 15mins it reached 12.8 on my interior digital readout..after switching everything I could off ie heating, lights, at 2.30am I still had 12.2 in the readout.. but by 6.45am it was down to 10.8
    I have charged it again by running the engine and am back to 12.7
    I will be able to get EHU tonight..
    How do I know if I should replace them or not?
    Thank you in advance


    • Nigel Murphy
      May 18, 2022 @ 08:59

      Hi Carol, did you get it dorted. I have a similar problem. I had the battery load tested and showed as OK, but still doesn’t hold yhe charge. On board display shows between 0 and 0.2 amps being drawn so should be fine.


  4. Sian
    June 15, 2020 @ 11:23

    Hi Paul,

    I’ve recently installed a new battery and VSR to my camper and have noticed it hasn’t been charging. In fact on some drives the leisure battery power seems to drop significantly. Could it be that the starter battery is drawing power from the leisure battery? I thought power could only flow the other way through the split chargers? And if I’m right could it be a faulty split charger do you think? My starter battery did recently go flat so I recharged it with a battery charger. So the leisure battery is in a better state than the starter battery. But as I said I thought that power could only be drawn into the leisure battery not the other way around.
    Any help would be greatly appreciated.



    • Paul Fabrizio
      June 26, 2020 @ 10:12

      Hi Sian
      You might have a faulty split charger. The first place to check is the actual batteries. I would fully charge the batteries. Test the batteries with a battery tester which puts then under load (they are about £30) to make sure they are in good shape. Disconnect each of the batteries in turn and see if there is any power drain. So, just have the leisure battery connected but not the starter battery, leave for a few days and vice versa. Test the voltage at each stage of both batteries.
      This will let you see if the batteries are holding a charge and if there is something pulling down the power.
      You may want to check that your leisure battery is actually getting a charge when the engine is running, the voltage should be over 14V when the alternator is charging.
      I had a really poor battery in our motorhome. It took a while to find the problem but the faulty battery was pulling the power from the good ones. All was well with the multimeter and each battery looked fully charged. When a load was put on the battery it was a different story – the duff battery would just die but would show a healthy voltage of about 13.4V.
      It can be time-consuming finding faults in the van. One of the things that killed one of our batteries was the inverter, if you have one make sure it’s off.
      Hope this helps a bit


    • Margaret doolan
      September 23, 2022 @ 16:22

      Our engine battery and leisure battery have both died , we are just back from a week away 3 nights on electric hook up then drove about 30 miles home o n Sunday 18th , tried to turn it on yesterday ,


  5. Andrew Lenton
    June 27, 2020 @ 17:01

    Paul’s advice is sound, I cannot fault it. if you have a clamp meter, and you join two batteries together that are fully charged there should be no or little equalising current, this was not the case with Apollo 13, they had shut down all power, as their fuel cells in the command module utility’s module had loss all its oxygen; The crew need 20 Amps max to bring up the guidance computer, but the batteries in the command module could not supply this for the time required, the answer, was to connect the LEM batteries in parallel before they discarded it, this gave them enough power to bring up the computer before they let it go! So you are not alone with battery issues!!


    Andrew Lenton


    • Paul Fabrizio
      June 29, 2020 @ 21:57

      Your van sounds exciting Andrew, look after those LEM batteries!
      (Loved that film, by the way)


  6. Caleb Pottebaum
    October 22, 2020 @ 05:37

    To be honest your article is informative . I search many site to know about The main causes of battery drain is a faulty leisure battery. but I didn’t get the information I needed.
    I saw your site and I read it. I got some new information from here. It is beneficial for many more like me.
    Thanks for share your kind information.


  7. Pete
    October 23, 2020 @ 17:39

    Hi guys, can I have my motor home completely rewired with a whole new system – charger, control panel etc….. .? Thanks in advance pete


    • Paul Fabrizio
      January 26, 2021 @ 08:53

      It’s certainly possible, I would imagine it would be a pretty big job with a cost to match.


  8. Andy
    November 9, 2020 @ 16:36

    Interesting and informative article, thanks. Can I ask a question?

    If you had a new 115ah battery that you knew was working perfectly, but every time you switched on the habitation area 12v system the voltage dropped significantly, to the point where lights were dim and the water pump dropped the voltage dramatically when in use, where would you start troubleshooting?

    I’m in Scotland as well 🙂


    • Paul Fabrizio
      January 26, 2021 @ 08:57

      Hi Andy
      I would start at the fuse box for the habitation side. Pull the fuses one at a time (power off, then power on once the fuse is pulled) and see if there is a particular circuit that’s causing the problem. Hopefully, there is and you can narrow down the search.


  9. Andrew Lenton
    January 26, 2021 @ 11:33

    Hi Andy,

    Something is puling a lot of power, (assuming it is not your command module guidance computer that you will need for re-entry and considered essential !)

    You could put an ammeter across the fuse terminals (fuse removed), however, if the current is over 10 or 20 Amps, this may well blow the internal fuse of your amp meter, so a word of caution.

    Another way, as Paul, says is to remove all fuses and replace one at a time, measure the voltage on the incoming supply to the fuse, than fit the fuse and check the volt drop. For example lets say you have 12.7V coming in, and you fit the fuse and the voltage drops say to 11V, than you know you are pulling some high current, or your wiring is very thin! if is drops to 12.6 then that circuit is fine or not doing very much. lead acid batteries can deliver 1000’s of amps, so be careful.

    I do recommend a Digital Volt meter with a current clamp. make sure it works on DC not all do, They are not expensive from the right supplier £25 or so. see for example. The beauty of these meters is they do not disturb the wiring, just clamp around the wire feed your circuit.

    BR Andrew


    • Brian
      March 23, 2022 @ 09:15

      I have a 350w solar panel.
      2 x 110 batteries my epever unit tells me 100% even if I use a little power like an led or anything else immediately it starts reading 56% how can it loose so much power so quickly


      • Paul Fabrizio
        March 28, 2022 @ 18:43

        Sounds like a cell problem in a battery. Need to test each battery individually and see if they can carry a load.


  10. Abi
    August 22, 2021 @ 08:47

    Hi this is a great article thanks…

    We live on a boat so similar, just larger set up with our leisure batteries. We had 5x110ah leisure batteries which has run everything in our boat seamlessly including a 24/7 240v system via 1500w inverter for our fridge. (lots of boaters now use this as fridges are so energy efficient these days the discrepancy in energy usage between that and 12v is minimal).

    As i say this has been perfect for us until the past 5 months or so…our inverter started to beep at around 5am suggesting not enough energy to power it. This has been a saver for our batteries because it stops them being discharged too much. We disconnected everything and tested each battery in the morning, so not fully charged, and 1 was showing 10.8v while the other 4 were at 12.85v. we removed this battery from the circuit hoping it was the culprit…but the inverter still went off in the early hours.

    We are stumped. We run nothing but the fridge overnight which up to now has never been a problem. we do have lights to the voltmeter on out switchboard so could it be something on here discharging them??

    We haven’t tried testing the batteries under load. It’s a bit hard to disconnect batteries for a few days when we need them for our water pump, fridge etc.

    I’d love to hear any ideas you have…

    Many Thanks

    Abi & family


    • Paul Fabrizio
      August 26, 2021 @ 20:59

      Hi Abi
      Sounds like a great system you have set up.
      I had a problem with one of our batteries. It would show a nice 12.8V, or thereabouts, but under load, the voltage would drop dramatically.
      There is no easy way to detect this but I did use one of these – – a Battery Load Tester
      It puts a large load on the battery – looks like a heating element inside it. This will show up most problems with batteries.
      Probably quite useful when you have as many batteries as you have.
      Hope this helps.
      Kind regards


  11. Andrew Lenton
    August 27, 2021 @ 10:44

    Hi Abi, are the five batteries in parallel? this makes 550Ah, !! there is no perfect set up, if one 12V battery is down, it will hog the charge from the good batteries. I presumed they are charged from the the alternator or solar panels or both?

    check cells are fully covered and none are dry, assuming it is not sealed

    Load test the low battery, see what happens, if any cell bubbles than it has gone to the big battery in the sky!

    If it is just flat (unlikely, as all would be flat), and no cells will bubble, try recharging it on its own, if it does not get up to 13.8 -14.2 on charge after a few hours at the 20 A charge rate, it is toast, check cells are fully covered and none are dry, a duff cell may bubble. When fully charged and the charger is a constant voltage 13.8V the cells should spit slightly. What is the age?

    leisure batteries that are fully charged and only drained to 80% then recharged should do some 1000-1500 cycles, to get a battery to 100% you need an intelligent charger MTTP type. Hoe this helps

    BR Andrew (ex submarine engineer)


  12. Joe
    March 22, 2022 @ 14:06

    What a helpful page, thank you! I measured the current flowing from my leisure battery to the campervan and found a constant flow of 0.66 amps. Most of it goes to a circuit that I think has just a stereo on standby and a usb charger that is switched off.
    Am I right to think that is far too high?
    (By my reckoning that level of drain gives me about three days of camping (without even using any reading lights) before the 105ah battery needs recharging.)
    I appreciate you answering folks’s questions. Joe


    • Paul Fabrizio
      March 28, 2022 @ 18:46

      Hi Joe
      That does seem to be a bit much. Try disconnecting the stereo and see if you can isolate the power drain. If it’s not the stereo you will have to try and find what’s drawing the power.
      We had an inverter in the motorhome that would draw about the same power as you are seeing while just sitting – could it be an inverter?


  13. Diane
    April 1, 2022 @ 15:13

    Hi we have just got out first camper a Renault master timberland endevour. battery seams to have died. Message in display reads engine started system disabled. We have solar pannel which said fully charged. Has anyone had this problem.?


  14. george
    June 6, 2022 @ 12:01

    Hi guys i have a problem with my Leisure batterys run down whilst mobile in my motorhome,I have done all the standard tests but i am confused what the cause may be, I can charge up my batterys to maximum through the mains sytem no problem drive for say 3 hours park up i may be lucky to have 2 hours power for the tv ect pretty poor, charge up my batterys ,remove the fuse to my altenator from my leisure batterys on board system whilst driving ,job done 12 hours and more of power all batterys in good condition also the invertor is new,nothing left on to draw power just confusing. thank guys George.


  15. david otter
    March 16, 2023 @ 16:39

    what power drain is normal from a engine battery transit t175 autotrail


  16. Geraint Williams
    August 5, 2023 @ 16:51

    My motorhome battery voltage shows a pretty constant good 13v but the ‘capacity’ indicator drops from full to 25% over a week when not being charged (internal charger).
    Is this an indication that the battery needs replacing /
    Battery is 7 years old.
    Thanks in advance.


  17. Geraint Williams
    August 6, 2023 @ 11:00

    Advice please.
    The leisure batteries in my mobile home show a good and pretty constant 13 v but the AH capacity indicator shows a rapid drop from 100% to 25% if the internal charger is not switched on (even with the solar panel). (with nothing on in the van drawing power)
    It also takes a considerable time to come back up when the charger is on.
    The batteries are now 7 years old…….. do I need to replace them ?
    Thanks in advance
    Geraint Williams


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