Battery charger makes charge controller think bank is charged

mryimmers
mryimmers Solar Expert Posts: 117 ✭✭✭
Good Morning Everyone,
I'm asking this question for my off grid neighbour, he is not really into researching stuff. He has about 650 watts of PV going to a xantrex WX 60 amp CC, charging 4 X L 16 type batteries. He has a 10 amp automotive battery charger hooked up to his bank.(Yes, not nearly enough) Generator is a 2000 watt Honda inverter type. He says when he runs his generator on a sunny day and the battery charger is plugged in, it causes his CC to stop charging. I suppose the charger voltage is fooling the CC into thinking the bank is charged, which makes sense, but can this be avoided or just make sure battery charger is unplugged if he is running generator during the day? Thanks HH
510 watt pv, TS-MPPT 60, Exeltech XP1100, XP600 & XP250 @ 24V, 4x Trojan 105RE, Trimetric 2030, Yamaha EF2400i gen.

Comments

  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Battery charger makes charge controller think bank is charged

    Welcome to the forum!
    This is a common "problem" for folks with more than one charging source feeding their batteries.
    Any charging source will raise battery voltage, and since charge controllers look to battery voltage to determine their state of charge, anything that raises that voltage will be seen by the controller as a higher state of charge. If the battery voltage is driven high enough, the charge controller will see that as a fully charged battery, and thus stop charging.
    I would recommend shutting off the battery charger on sunny days. This will both permit the sun to charge the batteries instead of burning fuel in a generator to do what the sun can do for free, and it will allow the charge controller to see a voltage more in keeping with the actual battery state of charge.
  • mryimmers
    mryimmers Solar Expert Posts: 117 ✭✭✭
    Re: Battery charger makes charge controller think bank is charged

    Thanks for the reply Wayne, I will pass that along to him. As you replied I was just reading a thread a bit down the page that touched on this subject too, should have looked a bit harder I guess :p. I want to get him to check this forum out as there is so much info here, this should be mandatory if you want to be off grid!!!! Thanks again HH
    510 watt pv, TS-MPPT 60, Exeltech XP1100, XP600 & XP250 @ 24V, 4x Trojan 105RE, Trimetric 2030, Yamaha EF2400i gen.
  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: Battery charger makes charge controller think bank is charged

    You can set the absorption voltage on the undesirable source (generator) a little bit (0.5-1V) lower than on the desirable source (charge controller). This will cause the bad source to back up earlier and give space to the good one. If the charger is not configurable, it is possible to configure controller to match, but this might not be a good setting for other situations.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Battery charger makes charge controller think bank is charged
    NorthGuy wrote: »
    You can set the absorption voltage on the undesirable source (generator) a little bit (0.5-1V) lower than on the desirable source (charge controller). This will cause the bad source to back up earlier and give space to the good one. If the charger is not configurable, it is possible to configure controller to match, but this might not be a good setting for other situations.

    Not with an automotive battery charger you can't.
    The good news is that if a 10 Amp auto charger can push the battery Voltage up to where 40-ish Amps on an XW controller thinks the V is too high and stops doing anything the batteries are probably pretty good shape. Usually the Voltage on an auto charger are set to autoregulate at what would be pretty low for a set of deep cycles.

    Given that, I'd check the charge parameters on the solar controller first: they may be too low.
  • mryimmers
    mryimmers Solar Expert Posts: 117 ✭✭✭
    Re: Battery charger makes charge controller think bank is charged

    Ah, yes I see what you are getting at, I can try to find the specs for his batteries,and try to see what he is set at, if I know him, (and I do) he didn't spend much time at that….
    Maybe if I can show him how valuable this forum can be he'll check it out. thanks coot, HH
    510 watt pv, TS-MPPT 60, Exeltech XP1100, XP600 & XP250 @ 24V, 4x Trojan 105RE, Trimetric 2030, Yamaha EF2400i gen.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Battery charger makes charge controller think bank is charged

    Also, many folks underestimate the voltage developed in a undersized wire with high charge currents, and that can fool controllers too.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Battery charger makes charge controller think bank is charged
    mryimmers wrote: »
    He has a 10 amp automotive battery charger hooked up to his bank.(Yes, not nearly enough)

    Ouch. Has he actually verified the voltages used by the automotive charger? Some brands are either not accurate with their voltages and can damage batteries if set wrong, or may go into a high-voltage EQ of 15v or more without the owner's permission, ala some Schumacher speedchargers. Be careful out there.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Battery charger makes charge controller think bank is charged

    i agree with pnjunction that the automotive chargers aren't all that great. if the batteries are say 90% charged the battery voltage will continue to rise in line with the auto charger's ability to go higher in voltage. open circuit voltages from these chargers go too high as many have no regulation. it won't hurt his fla type batteries, but the resulting higher voltages developed could cause more maintenance to be needed so he has to watch electrolyte levels more often and clean things off more often along with the annoyance of this shutting down the cc. the answer is as was said, shut off the auto charger. it will be fine to use the auto charger in the bulk stage of charging and you will know this because it didn't shut down the cc being battery voltage is lower at that point. as soon as it goes beyond the absorb voltage setpoint of the cc the cc will shut down.