Cause of leisure battery overheating?

Joff and Gill
Joff and Gill Forum Participant Posts: 14
edited July 2023 in Caravans #1

Upon leaving site last Saturday, when I opened the leisure battery compartment on my caravan to disconnect the hook-up cable (following the correct procedure), I realised that the battery was extremely hot. It wasn't smelly or bulging but as it was so hot, I worried about it exploding and so disconnected it putting it somewhere that it could cool down. As I disconnected the hook-up power, the caravan meter dropped from 13v to 10.5 v. Once home 6 hours later, the battery was still slightly warm and the voltage (using my multi-meter) was only 5.5v so I know I need to replace the battery. However I don't know if it overheated because:

  1. The battery (which is at least 4.5 years old) has just died of old age
  2. The battery has been overcharged by the charger (between the hook-up input and the battery)
  3. The battery has been overcharged by the solar panel (via the panel controller (CMP12))
  4. Something else

I've had no other battery/electrical problems with the same set-up since buying the caravan 4.5 years ago.

Given the urgency of the situation on site (& my ignorance about the order of disconnecting/connecting solar panel controllers), I didn't disconnect the solar panel from its CMP12 controller until today (Monday).

I reconnected my hook-up lead at home (with battery disconnected) and measured the voltage across the leads that come from the charger - 13.5v (which seems ok). I don't know if it was useful to measure the current with battery disconnected but it was 0.5mA. This leads me to think that option 2 isn't the problem.

After disconnecting the solar panel from its CMP12 controller today, the panel (in sunshine) measured 21.5 volts across the solar panel connections (in fact it measured the same when the panel and CMP12 were connected). I measured 0.82A across the solar panel connections.

With the solar panel connected to the CMP12 panel controller (but with the battery still not connected to anything), the output from the controller to the battery leads is the same as the input to the controller (i.e 21.5v 0.82A). I'm wondering if the CMP12 is now broken (either because it was anyway and thus overcharged the battery, or because I disconnected the battery from the controller before disconnecting the solar panel?

I clearly need a new battery but don't want to break that one by overcharging it.

Any advice gratefully received. Thanks in anticipation

Comments

  • dave the rave
    dave the rave Forum Participant Posts: 806
    500 Comments
    edited July 2023 #2

    Sounds as if your battery has failed,places like halfords can check it for you and supply a replacement if necessary and at the age of your battery I would expect the battery to be the problem but the onboard charger could be faulty!

  • Unknown
    Unknown Forum Participant
    edited July 2023 #3
    The user and all related content has been Deleted User
  • mickysf
    mickysf Forum Participant Posts: 6,474 ✭✭✭
    2,500 Likes 1000 Comments
    edited July 2023 #4

    Sounds like possibly just one cell, maybe two have failed rather than all. That could cause the charging system to perform incorrectly.

  • Joff and Gill
    Joff and Gill Forum Participant Posts: 14
    edited July 2023 #5

    Thanks for taking the time to reply Dave,

    I had planned to take the battery to Halfords today but got waylaid. That's tomorrow's task. As I mentioned I'm pretty much convinced the battery is dead - the question is "why?" (and I'd like to know that so that I don't ruin the replacement battery)

  • Joff and Gill
    Joff and Gill Forum Participant Posts: 14
    edited July 2023 #6

    Thanks Dorset Dave

    Re the charger, the answer is "I don't know", sorry.  Its a 2012 Bailey Pegasus Rimini II caravan that I bought 2nd hand 4.5 years ago. I can't find anything in the manual and despite trying to trace the cables, they disappear behind units that I'm loathe to pull apart. I'd hoped that mentioning there's 13.5v from the charger output (with battery disconnected) might give a clue.

     

    I've attached a photo of the top of the Hanhook battery that got very hot. There's no other information on the sides of the battery that I can see

  • Joff and Gill
    Joff and Gill Forum Participant Posts: 14
    edited July 2023 #7

    Sorry Dave - I managed to send my reply to your input to [Deleted User User] - its been one of those days!

  • Joff and Gill
    Joff and Gill Forum Participant Posts: 14
    edited July 2023 #8

    Thanks Mickysf,

    I guess that's my conundrum i.e. I don't know if some cells died of 'natural causes' which then led to the others being overcharged (& getting very hot), or if something else (e.g the caravan charger or the solar panel controller) caused those cells to fail

    From the photo of the battery that I've now added, the battery condition indication supports the battery needing to be replaced

  • Unknown
    Unknown Forum Participant
    edited July 2023 #9
    The user and all related content has been Deleted User
  • Joff and Gill
    Joff and Gill Forum Participant Posts: 14
    edited July 2023 #10

    Thanks very much [Deleted User User]. That makes sense. I'll give Tanya Batteries a call

    Is it also possible that the solar panel (via its controller) has overcharged the battery? The fact that with the solar panel connected to the CMP12 panel controller (but with the battery still not connected to anything), the output from the controller to the battery leads is the same as the input to the controller from the solar panel(i.e 21.5v 0.82A).

  • Joff and Gill
    Joff and Gill Forum Participant Posts: 14
    edited July 2023 #11

    Sadly, Tanya Batteries felt unable to advise (apart from which battery to buy).However, I managed to find the charger this morning (please see 1st photo). It looks to be part of the unit that contains the breakers, RCD etc. I found it by tracing the thick orange cable (from the 3 pin EHU input socket) and the black cable (which contains both a positive and a negative thinner cable that connect to the battery terminals) to where the charger is under the front seat. The next photo shows these cables from the rear of the battery compartment inside the caravan (the thick grey cable connects the positive battery terminal to the motor mover isolation switch)

    The black cable in the 2nd photo is the one where I measured 13.5v across its +ve and -ve wires when the EHU cable was connected. Does anyone know if this cable is used both for charging the battery when the EHU is connected, and for 12v supply from the battery when the EHU isn't connected?

    The only other wires connected to the battery (when installed) are the thin black and red ones (next to the thick blue cable) in the 3rd photo. These comes from the output side of the solar panel controller shown in that photo

     

  • cyberyacht
    cyberyacht Forum Participant Posts: 10,218
    1000 Comments
    edited July 2023 #12

    I've got an 80Ah Exide Gel battery that has been replaced by a lithium set-up. Gels are considered superior to normal leisure batteries and second only to lithiums. If you are interested drop me a line. Mangled E mail is tony-dot-gillamATicloud-dot-com.

  • dave the rave
    dave the rave Forum Participant Posts: 806
    500 Comments
    edited July 2023 #13

    Thank you for your acknowledgement.I suggested halfords because of their presence in most large towns/cities.I am another who would recommend Tanya batteries for purchase of a replacement at a reasonable price and doorstep delivery.

  • Joff and Gill
    Joff and Gill Forum Participant Posts: 14
    edited July 2023 #14

    Thanks but I've now ordered a 105Ah battery from Tanya

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