Charging batteries with a gen

4ptbuck
4ptbuck Registered Users Posts: 12
First post here,... so a little background.

I've gott a remote offgrid cabin in Princeton BC.

I've got 1 120W panel, connected to a Morningstar PWM controller, charging 2 golf cart bateries.

For loads, it's minimal, just 11W, 12V lights. Typically, 1 or 2 on at a time, for a few hours at night.

Other loads may include recharging small appliances, NDS, Laptop.

I also have a 1200W invertor that is only used for low draw items, ie, speakers for the ipod.

Overall I am quite happy with what I have.

In the summer, the sun keeps up with charging. In the winter, after about 2-3 days, the batteries drain to 'yellow' on the Controller, indicating 12V I think.

Anyways, I have a 10A charger, and a 200/40/2 charger. 200 is only for engine start.

Well, at the cabin last time up, we managed to drain the batteries to 'yellow' so I stared the generator, 3000W coleman. Plug all the chargers in and measured with a clamp on amp meter.

There was almost nothing in amps, generator at idle. I bumped the idle up to run the generator fast, and got:


0.7A from the 10A charger
5A from the 40A charger (at the 40A) setting

All the while being supplemented by about 5A solar.

Is this normal performace for a charger?

Is there a better setup for this? I was thinking about an upgrade to an autostart generator that would kick on at certain Voltage and run a charger till the batteries are full with a bulk charge, leaving the rest to solar.

thoughts on design?

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Charging batteries with a gen

    Welcome to the forum.

    I'm going to suggest you buy a hydrometer. About $5 from Princess Auto. Check each cell on those batteries. I rather suspect they've been chronically under-charged, as one 120 Watt panel isn't really enough to keep a 220 Amp hours @ 12 Volt battery bank properly charged. If my suspicions are correct, sulphation has set in and the actual capacity of those batteries has decreased significantly. That is why they won't draw much current even from the battery chargers.

    If this is an occasional use cabin you will probably want to at least double the solar panels to keep the batteries charged. Normally you try for a maximum charge current of 5%-13% of the batteries' total Amp hours. That would be like this:

    5% (minimum) of 220 Amp hours = 11 Amps peak charge current. @ 14.4 Volts charging = 158 Watts, after derating (77% efficiency typically) which means an array of 205 Watts minimum. You'll probably need to change the charge controller to something that will handle the greater current too.

    You should only need to run one of those AC battery chargers, not two together. Put them on at 40 Amps and let it go for several hours (after checking to be sure the water level is above the plates). Then let them sit for a few hours (no load, no charge) and check the specific gravity. You should see numbers improving (like from 1.225 to 1.250) and consistency across all cells. If not, repeat the process a couple of times and see if there's any improvement.

    Automotive type chargers are not ideal for deep cycle batteries, but it ought to be able to manage Bulk charging at least. Trouble is your solar controller probably doesn't do the full 3 stage charging procedure either. It doesn't take long to wreck batteries without proper charging. I suspect you'll need new ones.
  • 4ptbuck
    4ptbuck Registered Users Posts: 12
    Re: Charging batteries with a gen

    I do have a hydrometer.

    I did have a problem with one of the cells. After about 3 years, not sure why, but it was lower than the rest. I think the cell got stale. I didn't have the RC I expected. Shook up the battery, and charged it up. Seems to work fine. I did however, bring them into a battery shop and had them go through it, including a 75A draw down test. The batteries performed for over 120 mins. So they are still good.

    As to the charging rates, with the sun in Princeton, I get upwards to 8-9 A at peak. Not quite the 5%, but close.

    The cabin is occasional use, mostly long weekends. The past 2 weeks, was our normal 'long' trip. Also, we do try to spend ~5 around Xmas/New Years. Worst time for solar, and I know it.

    That's why I asked about the chargers. I wouldn't expect 40A out of my big charger, but was expecting well more than the 5A I was getting, especially with the battery drawn down to 12V.

    The MorningStar Prostar PWM 15A controller I do have does:

    1. Bulk recharging with 100% of available solar energy.
    2. PWM constant-voltage regulation to prevent heating and excessive battery gassing.
    Pulse charging to restore full battery capacity.
    3. Float: After battery is fully recharged, ProStar reduces to a float or trickle charge. The
    transition depends on battery history. A load that exceeds available solar output will
    return ProStar to the PWM mode.
    4. Equalize: A boost charge that depends on elapsed time and battery history. Flooded
    cells receive a vigorous equalization, sealed batteries a smaller boost to bring
    uneven cells into balance and extend the battery life. Gel cells are not equalized.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Charging batteries with a gen

    Here's the thing: if you had about 288 Watts of panel on that Prostar 15 you could give your batteries about 6% charge rate most days. That would be full current through Bulk to 14.4 Volts (low if these are Trojans) at Absorb, hold Absorb there for a couple of hours, and the Float at 13.8 Volts 'til the sun gets too low.

    Automotive battery charger tries to push current to raise Voltage up to about 14.2. Sort of lacking in regulation, much less the sophisticated programming of a charge controller. The Iota chargers http://www.solar-electric.com/bach1.html are better than standard automotive chargers, but in my opinion still less than perfect. If the batteries don't get a good high-current charge from time-to-time they will sulphate. 120 minutes is nothing to a deep cycle; that is an automotive battery test. These things are meant to deliver current over 20 hours, not two. I still think they're chronically under-charged.

    Autostart gens can be cantankerous. Chances are your existing one isn't adaptable to this (needs electric start, auto choke just to begin with). Then you need a Voltage controlled switch or more sophisticated controller/inverter to operate the start function. On the whole the money would probably be better spent on more panel. You may not be able to get an exact match to the panel you have, but if you know the specs on it (Voc, Vmp, Imp, Isc) you might be able to come close. Otherwise a couple of Kyocera 135's would get you much nearer to a decent charge rate.
  • 4ptbuck
    4ptbuck Registered Users Posts: 12
    Re: Charging batteries with a gen

    Good discussion so far.

    Thing is that in the Summer months, the system works perfectly fine. It the occasional extended use, or winter months that causes me a small heartache.

    I think I should get the autostart genny off my mind. I only menitioned it, cause my neighbor has one, connected to a Xantrax system, and 8 L16s i think. It was the cats azz...

    Purchasing another panel, and a new charge conroller is not a financial option.
    I fully expect my batteries to last quite a while longer. I haven't run into issues in the past.

    I'll put up with running the genny for an hour every now and then. BUT shouldn't the current draw be much higher, especially with the batteries run down?
    That's the part the really mystifies me. I did have the charger plugged into houshold 120AC, and did see the Amp needle move up higher (I didn't put the clamp on at the time), while topping up a low car battery.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Charging batteries with a gen

    You can check the AC output of the generator with a DVM and be sure it's up to snuff. If a battery charger doesn't get full Voltage in it won't put full Voltage out, and sometimes gens do fall a bit short of 120. For most things this doesn't matter: 110 Volts to 125 Volts and they work. Battery chargers that don't have an "absolute" reference can be fooled. But mostly they only put out what current is drawn by the battery, and there's an upper limit to how much Voltage they'll push to bring the battery up.

    With a solar panel & controller you've basically got up to the Vmp of the panel minus losses to work from. The automotive battery charger ... ? You don't know. It all depends on how it's built. I've seen some pretty poor circuitry inside some of them. Ever notice how sometimes a car battery won't draw from a charger at all, even though it's dead? Then turn the lights on and the charger comes up to 3 Amps or so, you shut the lights off and the charging will continue. These things are less-than-perfect chargers! Take some Voltage readings while charging and see what it operates at. Won't be perfect, but it will give you some idea.

    Yes, panels are pricey. Especially here in Bring Cash, Canada. :p
    Maybe you can swing an Iota so that gen charging more closely approximates the right profile for the deep cycle.
  • 4ptbuck
    4ptbuck Registered Users Posts: 12
    Re: Charging batteries with a gen

    I'll do that next time i am up at the cabin.
  • 2manytoyz
    2manytoyz Solar Expert Posts: 373 ✭✭✭
    Re: Charging batteries with a gen

    I have found that having a number of different chargers, all attempting to charge a battery, sometimes have different charge settings. That is, when charger 1 brings the battery voltage up to 'x', charger 2 might kick out of bulk mode, and contribute next to nothing. If you put a heavy load on the battery while charging with multiple chargers, you'll likely find they'll all contribute to the charge at that point. JMHO.

    Too small of a charger can do as much damage as a trickle charger. In the first case, the battery sulphates. In the second, the battery solution stratifies, separating the acid from the water, and the plates then sit partially in one, and partcially in the other. In both cases, the battery dies an early death. I experienced the second one first hand. In less than a year, I killed a battery.

    I agree with the other comments. I believe your batteries are probably toast. The voltage comes up quickly on charge, fooling some chargers, but there's little capacity left.

    While buying another panel, and charge controller might sound like an expensive solution, having to replace the batteries every couple of years adds up too.

    FWIW, my golf cart batteries sit in a hot FL garage (mid 90s this time of year), which should shorten their life, but they get exercised daily, and properly charged. Tad over 4.5 years, still going strong.
  • 4ptbuck
    4ptbuck Registered Users Posts: 12
    Re: Charging batteries with a gen

    I am not buying into the batteries are toast theory.

    The batteries put out 150 AH, before hitting the critical value (which I don't know). For a 220AH battery that's not bad.

    I did have a voltmeter on the charger as it was charging. I recall a volate of about 12.5V. So I don't believe my batteries are tricking my charger.

    On the small 10A, I do know that as it approaches the Voltage setpoint, at about 14V, it will start to pulse. It never got there.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Charging batteries with a gen

    Something you might want to read through, the deep cycle battery FAQ's: http://www.windsun.com/Batteries/Battery_FAQ.htm

    12.5 Volts, btw, is well shy of the 14.4 Volts that a deep cycle FLA should be charged at. It also needs to be held at that Voltage for an hour or more in order to truly recharge the battery.

    What 2manytoyz is referring to is the situation where the chargers work against each other because of different Voltage set points. The solar controller is trying for 14.4 Volts. To the automotive chargers that is more than "fully charged" so they will not put out full current. You can even see this with inverter/chargers and solar controllers attached to the same batteries but with different programmed values.

    You could try the big charger on its own, with the Prostar disconnected, and see if it pushes more than 5 Amps on the 40 Amp setting.
  • TheBackRoads
    TheBackRoads Solar Expert Posts: 274 ✭✭
    Re: Charging batteries with a gen

    Going back to the OP... I'm curious as to the genny your using... And maybe the professionals can correct me but, i don't think you can run a standard generator at slower than full speed and get the correct HZ/ power output? Wouldn't that mess with how a charger works?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Charging batteries with a gen
    Going back to the OP... I'm curious as to the genny your using... And maybe the professionals can correct me but, i don't think you can run a standard generator at slower than full speed and get the correct HZ/ power output? Wouldn't that mess with how a charger works?

    I'm not sure what he means by "I bumped the idle up to run the generator fast" because all the Champion generators available around here are fixed-RPM units that spin 3600; there is no "idle" on them. Perhaps they make an inverter-generator available in the US?

    With a fixed-RPM unit changing the engine speed will alter the Hz output, but a small variation one way or another will not have a significant effect on a battery charger's performance. It is normal for line Voltage to fluctuate a few Hz, usually not more than 3.
  • 4ptbuck
    4ptbuck Registered Users Posts: 12
    Re: Charging batteries with a gen

    In my original post I did say I have a Coleman 3000 generator.
    It is a Coleman Maxa Powermate 3000 genertaor.
    It has an carb, with an idle set screw. With this set screw, I can bump up the rpms of the genny.

    It is not a Champion.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Charging batteries with a gen

    Mia Culpa!
    I meant to type "Coleman" but put "Champion" instead because I was looking at those for someone else at the same time.

    The end result is the same: they're a fixed-RPM generator and technically do not "idle" although you do have some adjustment on the run speed. I have one of their 5 kW units and I expect the 3 kW is much the same.

    The resulting variation in Voltage will have more effect on a charger than the change in frequency.
  • 4ptbuck
    4ptbuck Registered Users Posts: 12
    Re: Charging batteries with a gen

    Well for sure mine steps up it's run speed as load is applied.
    ie if I plug in my skill saw, it'll be at idle when the trigger is NOT pressed.
    Once the trigger is pulled, the engine speed ramps up.
  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: Charging batteries with a gen
    4ptbuck wrote: »
    Well for sure mine steps up it's run speed as load is applied.
    ie if I plug in my skill saw, it'll be at idle when the trigger is NOT pressed.
    Once the trigger is pulled, the engine speed ramps up.
    Are you sure about that? I'm not calling you out or anything, but an engine when it is under load can be a lot louder than when it is unloaded, even if it is spinning at the same RPM.
  • 4ptbuck
    4ptbuck Registered Users Posts: 12
    Re: Charging batteries with a gen

    Well, I am not 100% certain, that when it's under load that the RPM spins up.

    I am certain however that the throttle linkage does move, and it does sound like it does spin up. It sounds exactly like a motor at low speed idle, going to high speed rev.

    Just like if I either push the throttle linkage with my finger, or with the idle screw.

    There is a govenor linkage though that is adjustable. I never have figured out of to adjust that properly. Perhaps it isn't mean to spin up, and just work harder
  • 4ptbuck
    4ptbuck Registered Users Posts: 12
    Re: Charging batteries with a gen

    well I did some internet reading, and I think perhaps my genny is suppose to be a constant RPM machine.

    How do I set the govenor for 3600rpm which should give me 60Hz?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Charging batteries with a gen

    No, the engine RPM's remain relatively the same (there's always some fluctuation). What's happening is the governor is opening the throttle more in order to maintain that speed against the increased electrical load. You are hearing the motor load up, not an actual change in speed. Mine does this too. If you were to vary the RPM's you will get a change in both Voltage and frequency. If that change is outside the acceptable parameters of 120 (or 240) VAC 60 Hz it will show up as problems with whatever you're trying to run off it.
  • 4ptbuck
    4ptbuck Registered Users Posts: 12
    Re: Charging batteries with a gen

    ^ yup, I agree.
    I have played with the idle setting in the past. I have also played with the govenor spring.

    So how would I adjust the no load idle speed back to 3600, and the govenor to maintain that?
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Charging batteries with a gen

    When you push / pull on the linkage you are changing the engine speed, but that is not how the Generator is designed to work. On a fixed speed generator it will have a no load voltage of around 125V / 62 hz + / - . As the load is applied the governor will pick up the power on the generator. The no load output should have enough no load overage in it to eliminate a sag in the output below 120 / 60 hz output.

    It's tricky to get everything on a generator with manual control governor in perfect correlation to each other. If it's too sensitive, it will hunt. Not sensitive enough, it will sag below the acceptable output. There plenty of information on the internet on how to do it.

    A more expensive generator will have a AVR ( Automatic Voltage Regulator ) to help the governor maintain a stable speed and output. Inverted output generator as the Honda and others are the latest and greatest.
  • 4ptbuck
    4ptbuck Registered Users Posts: 12
    Re: Charging batteries with a gen

    I know for my genny, it has an idle adjustmet screw, that should set the no load speed.

    Also it has a govenor spring that has a bunch of notches on an arm that set it.

    I just am not sure how to measure Hz. I can measure Voltage with my DMM.
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Charging batteries with a gen
    4ptbuck wrote: »
    I know for my genny, it has an idle adjustmet screw, that should set the no load speed.

    Also it has a govenor spring that has a bunch of notches on an arm that set it.

    I just am not sure how to measure Hz. I can measure Voltage with my DMM.
    You should be able to if it will read Hz., some do, some don't. Just stick the leads in the output socket.
  • 4ptbuck
    4ptbuck Registered Users Posts: 12
    Re: Charging batteries with a gen

    my DMM doesn't read Hz.

    That's the challenge.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Charging batteries with a gen

    There are some smaller industrial genset that will idle back if there is no AC load to save power.... Once a load is placed on the genset, it will throttle up to full RPM.

    Only "inverter/generators" can run at variable RPM and hold stable 50/60Hz output... However they usually have a high speed throttle override switch to allow them to run at rated RPM so they have better starting surge current (starting an A/C compressor, etc.). If in "eco" mode, they may not start some high starting current loads.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Charging batteries with a gen
    4ptbuck wrote: »
    my DMM doesn't read Hz.

    That's the challenge.
    Then do it by voltage and you have to assume the Hz. will follow. I'd set it at about 125 V with no load. Then check the output with a load, it all depends on what the load is.

    I go down to a marine place that repairs / rebuilds generators and they have a 55 gallon drum full of water with 20 heating elements. They can turn them on and off in any combination they want for a load. I guess if you know what you're doing it's easy.