Battery charging voltage?

  1. Gwil Member

    Messages:
    609
    Location:
    Portugal
    My elderly camper fritzed both the engine and house battery at the same time recently. Seemed a bit coincidental. I though maybe overcharging? There's no passive drain going on and the batteries are isolated from each other when not in use.

    I put a new engine battery in, charged with a smart charger, left it to rest 24hrs, and measured it at 12.83 volts. Started the engine, ran it for an extended period but the charge voltage into this fully charged battery never dropped below 14.4 volts. Surely over a period that would produce gassing?

    I thought from my previous experience with boat systems that a good float voltage should be no more than 13.8v? Or am I just overthinking this? I have a long track record of doing just that!

    Any bright sparks (groan) who could put me straight?
     
  2. mr haynes Member

    Messages:
    664
    Location:
    Scotland
    Will say on your alternator the charge voltage.
    14.4v is a normal value especially on an older system
     
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  3. Gwil Member

    Messages:
    609
    Location:
    Portugal
    Thanks, yes it's 30 years old, and the original system. Not kind to batteries then!
     
  4. jerrytug

    jerrytug Member

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    Location:
    Isle of Wight
    Sounds like the regulator isn't regulating, should be a cheap fix. Definitely needs doing..or it will fry your replacement batteries as well!
     
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  5. hotponyshoes Member

    Messages:
    3,398
    Location:
    Somerset. Uk
    14.4v should be fine.
    How does the 2nd one charge? If they both died togeather I would check the split charging is not stuck closed.
     
  6. Melvyn Best Member

    Messages:
    599
    Location:
    Cambridge
    Has the camper been standing for long periods ? It could just be a coincidence that both batteries failed at the same time. I would expect the charging voltage to be between 13.5 and 14.5 volts
     
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  7. Gwil Member

    Messages:
    609
    Location:
    Portugal
    To update this, I pulled the alternator this afternoon and a local auto electrician put it on his test rig and pronounced it fine at around 14.4v.

    But everything I read about charging regimes says yes that's fine for bulk charging of a partially or fully discharged battery, but float should be 13.5/13.8v or the battery will suffer in the longer term. After all, that is the charging regime of a smart charger. My bike is permanently on the same kind of charger when not in use, and I changed the oe battery after an astonishing eleven years.

    The camper does get left idle, but with voltage checked and hooked up to a smart charger (which I check as well, now I'm frightening myself....). I'm also about to fit it with a solar panel and two battery controller. I should add that the second battery charging is kicked in with a simple relay, and is isolated from the engine battery. I don't trust diode packs and the like from my marine experience.

    Maybe I have to live with it, just doesn't feel satisfactory somehow?
     
  8. hotponyshoes Member

    Messages:
    3,398
    Location:
    Somerset. Uk
    Float charging is long term.
    Presumably you are not parked up with the engine running for weeks on end and if you are then you are probably using the power at the same time.

    The difference between 13.8v and 14.4v is only 0.1v per cell and that ain't going to overcharge nothing. Don't worry about it.

    Maybe look at swapping the regular relay for a volt-sensing. That would mean you could then fit a single controller for the solar panel(s)
     
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  9. Kayos

    Kayos Member

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    5,912
    Location:
    Yorkshire
    14.4 is what I'd expect from an alternator
     
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  10. Ashley Burton

    Ashley Burton Member

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    Location:
    Northamptonhire
    14.4V Is fine!

    Your overthinking it :)
     
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  11. Gwil Member

    Messages:
    609
    Location:
    Portugal
    Ok, thanks everyone. I need to get a life obviously (or psychiatric help)!

    I took out the field from my old boat's 160amp alternator and put it through a rheostat. Once we did 117 hrs motoring nonstop on a totally windless trip from the Azores. I just liked having that control over the battery bank voltage. Got ten years from the 800ah bank, so my theory holds some water maybe. But overthinking for the old camper.
     
  12. julianf

    julianf Member

    Messages:
    5,064
    Location:
    devon, uk
    Vented lead acid batteries will gas a small amount at 14.4 probably, however gassing will also clean up the plates very slightly (same sort of idea as the localised boiling in ultrasonic cleaners) so, I guess, it's pros and cons.

    Floating a sealed battery at 14.4 probably isn't the best plan.
     
  13. Ashley Burton

    Ashley Burton Member

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    4,945
    Location:
    Northamptonhire
    That's a very extreme scenario :laughing:

    Are you planning on having an auxiliary/leisure battery in your van & solar?
     
  14. Gwil Member

    Messages:
    609
    Location:
    Portugal
    Yes, there are already two batteries, one isolated when the motor isn't running then connected by an ignition controlled relay. I'm about to add a solar controller and an 80w panel. Battery capacity is fine- the house battery is never heavily discharged.

    Certainly won't be driving 117 hours non stop in the van! It was a product of unusual weather, a cross swell from heavy weather further north and absolutely no wind. The only way to deal with it was to sit in the same place rolling horribly, or motor with sail up for some damping effect. My good old (home rebuilt) 5.1 litre BMC diesel liberated from a glider towing truck didn't miss a beat, tonked away at 1400 revs and surprisingly economical.
     
  15. Gwil Member

    Messages:
    609
    Location:
    Portugal
    Surely though most automotive batteries are sealed types these days?
     
  16. Wedg1e

    Wedg1e They call me Mr. Bodge-angles

    Messages:
    6,611
    Location:
    Teesside, England
    I'm less than enthusiastic about those 'smart' chargers having had both the TVR and the Honda lose batteries despite being on them; the TVRs was an Aldi special but the bike was on an Optimate 4 so I couldn't even blame the cheapo charger. They both failed in the same winter. Possibly, although I suspect not, a coincidence, the clock and the alarm system on the car packed in - totally fried - at the same time. Both items were the only things on the car that would see permanent 12V, plus whatever high voltage spikes the 'smart' charger uses for desulphating.
    Now I take both batteries off, keep them in the house and give them a blast with a traditional charger every few weeks when laid up.
     
  17. Ashley Burton

    Ashley Burton Member

    Messages:
    4,945
    Location:
    Northamptonhire
    @Wedg1e Had no problem with my Ring one, Charged plenty of batteries with it
     
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