Yep, just another newbie!

suecque
suecque Registered Users Posts: 4
in Solar Beginners Corner #1
Need some help from you pros, to sooth my savage beast.
We have 4 trojan t145 260 ah batteries in our motorhome.
They are wired as follows:
2 are in parallel then wired in series with the other 2 that are in parallel.
I hope i'm making sense :)
We currently have an old 1980s amorph 10w panel running to a 30amp
harbor freight tools charge controller and then to the opposite poles on one set of batteries only.
We are looking at upgrading to 2, 100 watt monocrys panels.
We watch about 3 hours of tv in the evening, none during the day and are currently located in a wide open space
in Laughlin NV.
We use the back up generator for running the microwave, if we need to plug in a portable heater, the vaccuum, or to charge the engine batteries.
Can anyone please tell me so I can tell him, if those 2, 100w panels are overkill, or if they will be able to recharge our coach bats sufficiently.
Please be kind. I'm trying to lower my husband's blood pressure by educating myself so I can share what I learn with him.
Thank you.
p.s. I understand there are a lot of variables so ask away!
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Comments

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #2
    Re: Yep, just another newbie!

    welcome and i like the little swing you put to your user name. for those that don't see it it is suzie q.
    i am assuming those are 6v batteries and a 2x2 arrangement will make that 12v at 520ah. we generally like to recommend a charge rate to the batteries of about 5%-13% and about 10% is pretty much what i believe trojan recommends for your batteries. 10% of 520ah is 52a. if using a pwm type charge controller the pv voltage doesn't really add to the valued power for charging and if the pv voltage is say 18v then this is 18v x 52a = 936w needed. the controller you have would also be insufficient unless you wish to operate at closer to the 5% charge rate of 26a and that is 468w in pv. if you need another controller then do get an mppt as it will maximize the power you can get out of the pvs and pv voltages become less restrictive being you'd now be able to use the 60 cell pvs out there that are cheaper to buy. the bad news is the mppt cc will cost considerably more. there will be other small losses involved too like wire resistive losses, charging losses, and cc operating losses. those 2 pvs you proposed would be closer to being good for float charging so you are far from overcharging these batteries.

    if you are using a generator to bring these up then what battery charger is hooked up to the batteries and at what current rating? how about the generator size in kw?
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  • suecque
    suecque Registered Users Posts: 4
    #3
    Re: Yep, just another newbie!

    Niel, Thank you so much for responding. Unfortunately while reading out loud all the wonderful information I'm finding here,
    "he who controls the remote", fell asleep. I do know that they are 6v batteries, that the old panel on a good day tested directly off the dangling wires,
    read 18. something volts, so he went and bought the charge controller hoping to not destroy the batteries he's worked so hard to maintain.
    He woke up and said he thinks the generator is running into an inverter which has a built in charger for the house batteries.
    Not much help until I can take a look at it tomorrow and see for myself.
    Personally, I would like enough storage capacity to not have to listen to or smell the diesel generator,
    and to be able to sufficiently recharge what we drained with the tv and satellite receiver the night before.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #4
    Re: Yep, just another newbie!

    well i can tell you the little pv he has isn't really doing much of anything. if the batteries are 12v then you'd be running a 520ah 24v battery bank, which isn't impossible, but would double the needed pvs to deliver a proper charge. odds are they are 6v each and if you look at an individual battery it will have 3 covered holes with caps making it 3 cells at 2v per cell or 6v. i just looked up the batteries for you to be sure and they are 6v batteries.

    can you tell us what the inverter make and model is? you can ask him later what the kw rating is on the generator.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: Yep, just another newbie!

    Some observations from the frozen North. :D

    First, I hope those batteries are connected as two parallel strings of two in series not one string of two parallel then two more parallel.
    Second, the charge controller should be connected with the negative on one string and the positive on the other.

    As Niel said, you've got 520 Amp hours @ 12 Volts. The 10 Watt panel is nothing to that; it won't even produce 1 Amp. The 18 Volts from the dangling wires would be Voc, which is irrelevant.

    What you need to fully charge them is more like 800 Watts of panel and a 60 Amp MPPT charge controller. That much panel probably isn't going to fit on the roof.
    Two 100 Watt panels will put out about 11 Amps maximum, which is a meager 2% charge rate: enough to keep the batteries up but not enough to charge them up.

    What I'd do is re-assess the load requirements and see if you actually need all that battery. With the right battery/panel combination you may not have to run that generator so often. The usual formula for an RV is the right amount of battery + as much panel as can be fit to reduce the need to run the gen for recharging.
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  • suecque
    suecque Registered Users Posts: 4
    #6
    Re: Yep, just another newbie!
    Cariboocoot wrote: »
    Some observations from the frozen North. :D

    First, I hope those batteries are connected as two parallel strings of two in series not one string of two parallel then two more parallel.
    Second, the charge controller should be connected with the negative on one string and the positive on the other.


    Yep they are 2 6 volts batteries in parallel, in series with 2 more parallel sets.
    I found out that he only has the charge controller attached to one set of the 6s not across to the other set. His reasoning is that he didn't
    think the little panel would charge all 4 of them. He is eyeing our neighbor's set up with much envy.
    That guy has 8-6v batteries with 2 huge pvs on the roof and a 750 wt wind turbine mounted on the rear. I still heard his gen running this a.m. though.
    Hubby is rooting around outside to find the charger and gen info. Thanks much for all the help!
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
    Re: Yep, just another newbie!

    Wind turbine on a motorhome? Heh. Probably thinks it charges for free while driving down the highway. :p
    Unless that's up a 50' mast it's just dead weight. That's why he was running the gen this morning.

    The little panel won't charge all four of them. Or even two, for that matter. However, since they are connected electrically it will try to.

    Anyhow, this image shows how they should be wired.
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  • suecque
    suecque Registered Users Posts: 4
    #8
    Re: Yep, just another newbie!

    It is on a mast about 15' tall mounted to a tray on the reciver hitch. He sets it up when he's parked and with the wind down here lately it has sounded like a helicopter taking off. Found the specs on our gen and charger/inverter.
    It's a Cummins/Onan diesel 8kw going into a 55amp converter with a built in charger. There is also a small 300 watt inverter that he turns on when we want to watch tv without the generator running. It powers some outlets on the dash as well which we plug our dvd player into. We turn that off when he fires up the gen.
    Last night we started out with 12.7 at the panel on the dash, watched tv for about 1.5 hours, fired the gen up when it reached 12.1. Used the toaster oven for an hour and watched tv for about 3. Gonna go buy a kill-o-watt to see exactly what each item is actually drawing.
    Thanks again and again for your patience and assistance. I really hate the generator running all evening while he sleeps in front of the tv ;)
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #9
    Re: Yep, just another newbie!
    suecque wrote: »
    I really hate the generator running all evening while he sleeps in front of the tv ;)

    Are you sure it is the genny making all that noise?:blush:
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #10
    Re: Yep, just another newbie!

    Many times, once you have hit all of the "conservation of energy check boxes"--The generators become ridiculously over sized for the installation (unless you are running A/C and other heavy loads).

    For example, if you can use an alternative like a Honda eu2000i (1,600 watt)--You might be able to run in the 4-9+ hours per gallon of fuel range--Have you figured out your fuel usage with the 8kW genset? (I also like the idea of installing a Watt*Hour meter of some sort on the generator output--basically figure out the kWH per gallon of gasoline you are using. 3-6kWH per gallon is "doing good", with efficient diesel setups, you can probably get upwards of 7+ kWH per gallon of diesel--But with "inefficient setups", you can probably fall down to 1kWH per gallon pretty easily).

    Diesel is certainly fuel efficient--and if you have diesel vehicle engine, carrying gasoline may be more of an issue.... But if this is 55 amps charging on a 12 volt battery bank:

    55 amps * 14.5 volts charging = 797.5 watts into the battery bank (there are other losses too--but start with the basics)

    You are using ~1/8th of the generator's capacity during pure battery charging. Diesel typically do not like running with light loads (wet stack, carbon build up, glazing of cylinder walls, etc.). With most diesels and other gensets, you should be aiming most of your runtime in the 50% or heavier loading... The little inverter gensets can do pretty well down to ~25% loading (i.e., 400 watts on a 1,600 watt inverter/generator will go around 9+ hours on 1 gallon of fuel or around 3kWH per gallon).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #11
    Re: Yep, just another newbie!

    I was going to say anyone who can sleep with an 8kW diesel gen running nearby is probably suffering from narcolepsy. :p
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #12
    Re: Yep, just another newbie!

    that is good if it is charging at about a 55a rate for that battery bank. if you have the goal of eliminating the generator or lowering the runtime needed then whatever you add will go towards that goal to whatever degree. technically, the wattage may get replaced in theory by 2 100w pvs for the loads you use, but it would pose an insufficient charge rate to the batteries. this would mean that every so many days (maybe a week even) i would then opt to run the generator to charge the batteries up with rather than relying on the smallish 200w pv array. as i said, upping to about a 5% rate would probably suffice for most times and it would still be advisable to run the genny maybe once every month or 2 to insure it gets a proper charge. can you go 3 140w pvs like,
    http://www.solar-electric.com/kykd140wa12v1.html
    as this would get you pretty close to the 5% area of charge? not sure if you prefer monocrystalline or not as these are multicrystalline. you could even go with 4 of those pvs as you have a 30a cc.

    while you are at it can you ask your other half what gauge wires he used in wiring the battery bank together and if he used identical wire legths to help keep equality in the batteries when they charge/discharge?
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