*NEW - now won’t start / Waeco Crx50 / General Voltage Conundrum

Discussion in 'Mech Tech' started by MadFrankie, Aug 19, 2019.

  1. Hi,

    Playing around with my wiring I’ve just noticed that when it’s connected to the mains and the fuse box has no draw against it it sits at around 13.6v, perfect.

    However, as soon as I turn the fridge on it drops immediately to around 12.4v and seems to sit around there for a minute until it drops steadily again for about a minute until it hits 12v then obviously dies as battery has nothing more to give.

    If I then turn the fridge off the battery returns to 13.6 within a minute as the mains kicks back in.

    Now, I’m sure this isn’t right as I’d expect the mains to keep up with the fridge draw, especially as it’s a compressor and supposed to be low power etc.

    So, anyone out there with an idea of where to start to diagnose? Fridge wiring? Faulty fridge? Dying battery?
  2. Check the wiring, doesn't sound right. It's a while since I wired mine but from memory it wires separate so should pull from both battery or mains.
  3. At the moment I’ve got it wired into my fuse board which is fed from the leisure battery.

    My thought was to wire it directly to the leisure battery, ie bypass the fuse board but I’m not sure that’s my problem as the fuse board works as expected for everything else until the fridge is turned on.

    I’ll pull out the fridge another evening and take a look at that end to see if there’s anything untoward there.
  4. Manual says it draws 1.1ah/h on average so it certainly shouldn’t be pulling that much surely.
  5. Could be the battery as it dies when a load is applied.

    Or I believe the CRX 50 has a low voltage cut out, maybe that needs adjusting, so an initial startup load doesn't trip it out.
  6. Will try and find the wiring diagram tmoro but I thought it wired separately from the mains and the leisure.
  7. Your hookup is not charging the battery and the battery is dead. It has a tiny capacity which makes the voltages look right but which will discharge fast with the 5 amps or so when the compressor runs. The 1.1 amps is an average for about 20% duty cycle..

    Try a 21 watt brake light bulb on the leisure battery directly across the terminals : watch the voltage these bulbs draw about 2 amps. The battery should hardly notice the load as if it is healthy it can supply it for several days.

    If you want to, buy a car battery analyser for about £20 on eBay.. these give you the CCA equivalent of your battery.. a healthy leisure battery can manage 400-800A equivalent. ( they measure by loading it with a couple of amps and measuring the tiny voltage drop, unlike the old ones with a massive resistor that actually do draw hundreds of amps...)

    Last edited: Aug 20, 2019
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  9. Hi,

    Right, bit of an update as I thought I’d try to diagnose the errors before I ripped it all out and started again as I don’t want to bring back in faulty parts.

    So...been measuring the voltages at main, leisure and fusebox to see if I can pinpoint the fault.

    All were at 13.3v a few moments after I took the trickle charge off - so my control voltage.

    With no devices drawing from either batteries other than the clock and radio backup - ie practically nothing.

    Over the course of the next 24 hours the main dropped and settled to around 12.8v and the leisure to 13v.

    Turning the engine on the main battery went up to 14v and then after a minute dropped and settled to 13.3v, and then the leisure rose to 13.3v and settled there.

    So far so good - I think.

    Now this part I know isn’t right. While the leisure battery is at or above 13.1v, the fusebox connected to it has power and powers the devices. As soon as it drops to 13v the fusebox has 0v going to it.

    Engine on / charge the leisure battery back up above 13v and fusebox gets power again.

    Next issue is the fridge, when the fusebox has power to it and I turn the fridge on - lets say at 13.3v - within 2 minutes it drops to 13v and then the fusebox loses power and the fridge goes off.

    With the engine on and doing the same, the bolts drop to 12.4v and continues to drop until there’s no power left...

    Sooooooo, any ideas what the hell is going on?

    I’m guessing batteries are ok, I have an issue from leisure to fusebox, (perhaps dodgy wire causing voltage drop), and also a separate one with the fridge connection.
    Last edited: Aug 21, 2019
  10. Have you checked the negative side it sounds like you have a high resistance somewhere.
  11. This ^^^^^

    I recently completely rewired the leisure side of things BUT ran twin wires to all electrical components powered by the leisure battery ensuring everything had a good earth .
    Basically fridge, lights , Propex and 12v sockets all have a separate positive from the leisure fuse box , next to that is an earth from the leisure battery and a bar connecting all the earths together so nothing is actually earthed to the van .

    seems to work well

    Sent from my SM-G960F using Tapatalk
  12. Hummm, that could be it...I wonder if I’ve got some crud underneath my earth connection on the leisure battery or fusebox.

    If that’s the main potential then I’ll just take everything out, give them a good tidy up / update and then put them back in new and carefully checking all the way.
  13. You should realise that that 13.3 volts is not charging either the main or starter battery.. so your alternator isnt delivering enough welly, maybe brushes or regulator/grounding.

    A shutoff voltage of 13 volts should be the low limit when batteries are linked "on charge". The alternator should eventually get battery voltage up to about 14.2 volts with the engine at reasonable RPM .. not necessarily at idle.

    For a battery which is not charging, the fridge should be disconnected at about 12.1 volts, not 13 volts.

    Methinks you are using the wrong relay to connect the fridge ...
  14. What split charger have you got? It actually sounds like the fusebox has power when the split charger is on, then nothing when it disconnects.
  15. Alternatively and more simply, alongside your ineffective charging circuit and knackered battery, you are connecting the fridge to the feed intended for an absorbtion fridge, which uses so much power 7-8 amps it can only be connected to the 12 volts when the engine is running.
    As you have a more economical fridge, you should be able to connect it simply via a fuse to the leisure battery.
  16. Ok, so here we go for a day of electrics.

    Started a fresh, main battery out, checked with my CCA, results = good battery.

    Cleaned battery terminals
    Put on new terminals
    Brushed earth chassis area and bolt
    Starter lead looked a little corroded so cut off ends, stripped wire back to reveal new copper and reconnected to battery terminal.

    All good so far

    Voltage looks fine and stays steady...however I’ve noticed that with the engine on the voltage doesn’t increase as expected - until I rev the engine a little and then voltage increases up to 13.8 / 13.9v.

    I’m thinking it’s always done this but now I’m really focusing on it I’ve noticed it.

    Checked various voltages around alternator and it’s 0.14v from battery negative to alt case, which I believe means an alternator on the way out???

    I’m going to move on to the rest of the split charge / leisure battery part now as if it is the alternator it’s a different problem to what I had before.

    Any thoughts so far anyone?
  17. No that is just the voltage drop on the earth return through the engine, gearbox earth strap body and battery earth strap.
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  18. Yes, but I was thinking that was quite high, surely 0.14v drop is a lot, I was expecting 0.05 or less? Which would mean the alternator earth is off...or is 0.14v acceptable for an old van?
  19. I thought it was 0.14V which is OK
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  20. I just measured alternator to engine block 0.01 ohms, engine block to battery negative 0.01 ohms. Quite hard to measure, my meter has a 30.00 ohm range and a zero button. So 0.01 means maybe even less..

    So 0.14 volts would be quite OK if the current is over 14 amps..

    Dont forget that when you rev up your engine if it has a relay with voltage hysteresis, the voltage on the starter battery will ramp up then drop as the relay closes but stays closed because the " relay open" voltage (13.0) is lower than the "relay close " voltage e.g. 13.6

    After a good few hours driving the voltage on the battery will eventually hit 14.2 volts.

    But that is why you cant really charge a leisure battery only off the alternator. You need hookup or solar to provide the bigger amp hours ..so you have a half flat 100AH battery. Typically engine running might give you 20 amps charging. Thats 2 hours 30 mins of fast driving to top up 50 AH of the leisure battery. Or 5 hours on 10 amp hookup charger, or about 200 watt solar cells.
    Last edited: Aug 24, 2019
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