OK forget relying on panels. Recommendations for a battery charger???

downtown NYCdowntown NYC Registered Users Posts: 11
So new direction. I was going to purchase a Magnum charger/ inverter. Looked at manual and hard wiring isn't for me in my apt. My new plan is to continue with the little sun/ wind I get, but to heavily rely upon a great battery bank charger that will not over/ under charge my batteries. What charger would you recommend? I have a Shumocker that claims to properly charge and maintain, but I have had off gassing in sealed AGM's with this charger. This is not good. Very dangerous with kids running around.

Thanks,

Andrew

Comments

  • BB.BB. Super Moderators, Administrators Posts: 29,489 admin
    Re: OK forget relying on panels. Recommendations for a battery charger???

    A big part of this should really start with your expected loads... Watts peak, Watt*Hours per day, etc. Then you design a battery bank+charger that will support your loads.

    In general, I like to stay with small loads (smaller inverter) and a good sized battery bank that can support those loads over several days. Once you know the battery bank capacity, you can then look at chargers (or inverter chargers) that will support those loads.

    In general, the main stream solar RE inverter-chargers are larger units--And for emergency power, smaller/high efficiency AC inverters are usually a better bet. There are few smaller inverter-charger units out there.

    Magnum inverter-chargers, in my humble opinion, are usually on the large size vs practical emergency power units for an apartment.

    From a mfg. point of view, when making an off grid power system, large inverters are cheap and (relatively) light weight/small size. They pair these with a small AGM battery (keep weight and costs down).

    Makes for, what sounds to be, a very capable off grid emergency power system.

    When in reality, the battery bank is so small that it is almost useless, and the AC inverter is wasting large amounts of power when recharging a cell phone+laptop+some LED lighting.

    For example, for $525 you can get:

    http://www.amazon.com/Xantrex-802-1500-XPower-Portable-Powerpack/dp/B00005RHQQ
    Xantrex 802-1500 XPower 1,500 Watt Portable Powerpack
    • Supplies up to 1,500 watt household electricity
    • 1,500 watt inverter and 51Ah AGM battery
    • AC and DC plug included
    • Portable, wheeled design
    • Excellent alternative to generators
    • 15.8 x 11.9 x 14.8 inches ; 60 pounds
    • 12 volt based battery+inverter
    • ~200 cycle battery life
    The XPower Powerpack can be used to produce power for numerous applications. For power emergencies it can run essential appliances like refrigerators, cordless/mobile phones, radios, fireplace fans, table lamps, or microwaves. For work sites, you can power your drills, belt sanders, circular saws, hedge trimmers, leaf blowers, vacuums, computers, large monitors, fax machines, and inkjet printers. For plain old fun, you can use the power source to run blenders, video games, TV and VCRs, satellite equipment, coffee makers, portable coolers and more.

    Sounds wonderful--Does it not? I could replace my $1,000 Honda eu2000i genset and 10 gallons of gasoline (~1,600 watt peak) with clean/quiet power.

    Weight and size wise--Power Pack and Genset are similar. Price, the Power Pack is 1/2 the cost. And would work well in an apartment.

    Power--both ~1,500 Watts of output power. What is not to like?

    Well, first thing to look at is the battery. It is a 51 AH AGM battery. About the size of battery found in a smaller car (50-80 AH typical). How much power could that supply. What could this portable power pack do vs a genset.

    At 1,500 Watts the portable power pack can (1,500 watt is roughly the power draw of a medium sized microwave oven):
    • 1,500 Watts * 1/0.85 inverter eff * 1/12 volt battery = 156 Amps draw on the battery
    • 51 AH battery * 1/156 Amp draw * 60 min/hour = 20 minutes run time (in real life, even less) to battery dead

    The genset with 10 gallons of gasoline:
    • Honda eu2000i will supply ~1,600 watts on 1.1 gallons of gasoline for 4 hours
    • 10 gallons / 1.1 gallons per 4 hours = 36 hours of run time (1.5 days of power)
    • Over 100x longer than the portable power pack
    What about running your refrigerator. Typical refrigerator takes around 120 Watts, and if you plug the refrigerator in right after the power failure, the refrigerator will run about 50% of the time.

    Power pack:
    • 51 AH * 12 volts * 0.85 AC inverter eff * 1/(120 Watts * 0.50 duty cycle) = 8.7 hours of run time to battery dead (best case estimate)
    Small Genset:
    • Honda will run ~9+ hours on 1.1 gallons of fuel at 1/4 rated power (400 watts)
    • 9 hours * 10 gallons * 1/1.1 gallons (per 9 hours at 400 watts) = 82 hours of run time (plus ~340 Watts of "free power" for other loads)
    You just leave your refrigerator shut (and move some ice from the freezer), and you can go ~24 hours without power. The Power Pack supplies virtually zero useful power for the refrigerator during an outage. The genset with 10 gallons of gasoline can keep the home running OK for 3.4 days (or ~2x longer if you only run the genset 12 hours during afternoons/evenings to keep fridge cool and the place lighted+some computer games+light cooking, etc.).

    So--Forget what you see with "emergency power stations"--They are designed by marketing and not really designed to meet the needs of a family for emergency power. While, technically, the device can run a microwave OR refrigerator OR other stuff--It can only supply this amount of power for a hand full of minutes to a couple of hours. If that is all you need--Then great--However, if you where expecting something else, define what your expectations are.

    A genset is never going to be safe for use inside an apartment. And a portable power pack type system is never going to be able to supply much more than a very limited amount of power to charge a cell phone, run a few lights, etc. for any length of time.

    You need to decide what your minimum power needs will be, and size the battery bank first. Then pick the devices that will support your battery bank (AC charging) and power needs (AC inverter, DC devices, etc.).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • downtown NYCdowntown NYC Registered Users Posts: 11
    Re: OK forget relying on panels. Recommendations for a battery charger???

    Alright a little more about what I already have. 400 watts solar, battery bank 1 1150amp hour, battery bank 2 900 amp hour. Little sun. Little wind. Thus recommendation for really good charger. All batteries are AGM sealed. I just want a really good battery charger without having to run BX cable. I'm not an electrician.

    Andrew
  • BB.BB. Super Moderators, Administrators Posts: 29,489 admin
    Re: OK forget relying on panels. Recommendations for a battery charger???

    OK... As I remember, those are 12 volt battery banks.

    Roughly, 5% to 13% rate of charge works good for solar. And you can go as high as 20-25% in some cases (thermal monitoring of battery bank, etc.).

    With flooded cell batteries, we would suggest 10%+ rate of charge for a daily cycling off grid system. For a standby system, and especially one running AGM batteries, a 5% minimum rate of charge could work OK. So, lets look at the numbers:

    1,150 AH for Bank 1
    900 AH for Bank 2

    Lets start with Bank 1:
    • 1,150 AH * 5% rate of charge = 57.5 Amp minimum rate of charge
    • 1,150 AH * 10% rate of charge = 115 Amp nominal rate of charge
    Some industrial type battery chargers from Iota:
    Xantrex has made some very nice chargers in the past. Their new product is the TC2 series--Largest is a TC2-60 amp @ 12 volts
    Now has a paralleling feature for 120 Amps from two parallel supplies.
    AMP UP-TO 120A GLOBALLY!
    Now with PARALLEL STACKING FEATURE*


    This NEW feature allows two chargers to work together to combine the output current, achieving up to 120A for large battery banks.

    *Applies to the new generation TRUECharge2 models - 20A (part #804-1220-02), 40A (part #804-1240-02) & 60A (part #804-1260-02). Please ensure you order TRUECharge2 Remote Panel part #808-8040-01 for parallel stacking.
    You can also parallel other supplies--But they will not "synchronize" their charging cycles. Not a big problem, but it can be distracting if you watch your supplies/battery bank closely.

    The Iota is the standard for "dumb supplies". You can adjust their output voltage (10 turn pot for most/all?? models). "IQ4" module makes the charger a bit smarter. Or you can use an external switch to change between Charge vs Float output charging voltage.

    The Xantrex has had very good reviews in the past. The new model has been very difficult to get for a long time (plus was late to market). Highly automated and some program-ability/adjustments from the front panel. I like that it has a Power Factor Corrected intput--Which allows you to use a smaller AC circuit (or genset) than non-PFC battery chargers (basically, it is more efficient AC input). However, it is not cheap.

    Then there are inverter-chargers. These can be very nice integrated units with lots of program-ability. A nice high end unit would be the Outback series (true sine wave):

    Outback Power VFX2812 2800 Watt Sine Wave Inverter


    And you would want a "Mate" of some sort to program it (you can program the AC input to not draw more than 12 amps from a 15 amp @ 120 VAC outlet). Not cheap, but a very nice high end and capable inverter-charger.

    Magnum also is a popular system. Here is their 12 volt inverter charger:

    Magnum MS2012 2000 Watt Sine Wave inverter w/charger

    I believe you also need a remote (they have two types, a normal and extended programming versions).

    Again, I would suggest the smallest AC inverter you can get away with. Large inverters can draw a fair amount of power just "turned on" with no loads (25 Watts) for the small Magnums.

    You can also put on a small 12 VDC input TSW 300 Watt AC charger that uses ~6 Watts when on, and much less on standby/remote on-off function:

    MorningStar 300 Watt TSW 12 volt AC inverter

    Not saying that these are your only, or even best choices... Just to give you an idea what is out there.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • downtown NYCdowntown NYC Registered Users Posts: 11
    Re: OK forget relying on panels. Recommendations for a battery charger???

    Thank you.

    New question. I don't understand. Does a 48 volt setup- IE Panels/ Battery bank(s) charge faster- IE, require less amp hours to recharge then does a 12 volt setup? Another moderator in an earlier post- my understanding, suggested so? I feel so ignorant on this subject.

    Andrew
  • BB.BB. Super Moderators, Administrators Posts: 29,489 admin
    Re: OK forget relying on panels. Recommendations for a battery charger???

    Power = Voltage * Current

    So--We are really working with power (Watts) when paper designing systems. 1,200 Watts at 12 volts, 24 volts, 48 volts, 120 volts, etc... is all still 1,200 Watts.

    However, what becomes interesting is the current:

    Current = Power / Voltage

    1,200 watts / 12 volts = 100 amps
    1,200 watts / 24 volts = 50 amps
    1,200 watts / 48 volts = 25 amps
    1,200 watts / 120 volts - 10 amps
    etc.

    So when "we" are choosing between a 12/24/48 volt system, we are looking at "power" (smaller inverters tend to be available at lower battery voltages) and "current"--Higher power requires more current and copper wiring at much more than ~100 amps becomes problematic (need very heavy copper cable, and very short wire runs to keep voltage drop low).

    For example, a 12 volt battery bank, it works out your AC inverters/DC loads can tolerate around a 0.5 volt drop.

    For a 48 volt battery bank, your inverter can withstand around a 2 volt drop.

    So, a 48 volt will have 1/4 the current and 4x the voltage drop--That is a huge difference in the amount of copper needed for your DC wiring (and you can send the DC power further distances).

    If you have the number of cells/batteries, you can wire up (for example, round numbers) a 1,200 AH @ 12 volt battery bank or a 600 AH @ 24 volt battery bank or a 300 AH @ 48 volt battery bank--All of these battery configurations store the same amount of power (remember power = V*I, if you have 4x the voltage, you "need" 1/4 the current for the same power.

    So, 10% rate of charge:
    1,200 AH * 10% rate of charge = 120 amps
    120 amps * 14.2 volts charging = 1,704 Watts
    300 AH * 10% rate of charge = 30 amps
    30 amps * 56.8 volts charging = 1,704 Watts

    So--The amount of "energy" needed to charge these banks is identical. In one case you would need "O" gauge wire for the 12 volt system and "10 or 8" awg wire for the 48 volt system. Random pricing has 10 AWG is around $0.26 per foot; and "1/O" AWG is around $3 per foot.

    That is why we like to work with Watts and Watt*Hours rather than Amps or Amp*Hours. We really do not need to work with voltage and current during paper design until you have your loads and basic sizing worked out. Then we can start looking at the specific hardware to meet your needs.

    In general, for a 12 volt DC battery system, I would suggest around 1,200 to 2,000 Watts of AC power as the maximum sized inverter. And 2x that for 24 VDC system, etc.

    Otherwise the copper cables (and fuses/switch gear, etc.) get really expensive when you start sizing for >100 amp load current. There are other design rules we suggest too (battery AH and voltage, series vs parallel, etc.) that are also important touch points during the design process.

    Try not to get too far ahead... A 1,200 AH @ 12 volt battery bank costs about the same as a 300 AH @ 48 volt battery bank (excluding wiring costs). Looking at your power needs (how much loads, and how much charging wattage you have available, etc.) will set the "size" of your system. We can then go through selection of the equipment that may support those needs.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • downtown NYCdowntown NYC Registered Users Posts: 11
    Re: OK forget relying on panels. Recommendations for a battery charger???

    OK next set of question, and thank you BTW:)

    1. If I use 2 150 watt 24 volt panels and mix them with several other 100 watt 24 volt panels, will that max me out at 100 watts since that is the lessor of the two. I read that somewhere?

    2. OK- in laymen terms, I have the two battery banks sitting idle. I assume that I should be hooking up an inverter and using them everyday. This along with recharging. Can I recharge while using the inverter? Should I unhook the inverter while charging? Also I have two BLS battery life savers. Should these be hooked up and running while charging?

    Thank you again,

    Andrew
  • BB.BB. Super Moderators, Administrators Posts: 29,489 admin
    Re: OK forget relying on panels. Recommendations for a battery charger???

    It is a bit more complicated mixing panels. We need to know the Imp and Vmp (operating current and voltage at maximum power)l, how many of each panel(s) do you have, and what battery bank voltage and charge controller (mppt/pwm) type you want to connect.

    In general, you want to parallel panels with Vmp no more than 10% apart. And connect in series panels that are no more than 10% apart for Imp.

    And "24 volt panels" -- There are true "24 Volt panels" for charging 24 Volt battery banks that have Vmp in the range of 35-38 Volts.

    And there are "24 volt panels" made for grid tied inverters that have Vmp around 30 Volts. These panels should not be mixed with Vmp~35-38 volt panels (in parallel) and cannot charge a 24 volt battery bank properly (Vmp is not high enough to charge when temperature, wiring&controller voltage drop, and battery charging requirements are all taken into account).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 29,489 admin
    Re: OK forget relying on panels. Recommendations for a battery charger???

    Your second question... The battery bank (if flooded cell) should be either under float charging (~13.8 volts or so) 100% of the time, or recharge for 8-24 hours once a month.

    If you let the batteries set for many weeks/months without charging, they will self discharge and die.

    AGM type batteries can go ~3-6 months between recharging.

    You can recharge when the inverter is running. It will not hurt anything. With some inverters and charging conditions, it is possible for the battery charger+battery voltage to exceed the operating input voltage for the AC inverter.

    For example, many inverter will shut down at ~15.0 volts input. But if you are equalizing the battery bank, you may be pushing 15.0+ volts to the battery. And if you are in a cold region where the batteries are below freezing, the normal charging absorb charging voltage can exceed 15.0 volts.

    When charging a battery bank with solar power, and you have constant daytime AC inverter loads, you need to take the inverter loads into account as this subtracts from the battery bank's charging current. We usually like to recommend around 5% to 13% rate of charge. If the inverter is taking too much current during the day (average loads), the battery bank may not be properly recharged and you will need to add solar panels to both charge the battery bank AND run the inverter daytime loads.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nyarelathodepnyarelathodep Solar Expert Posts: 99 ✭✭
    Re: OK forget relying on panels. Recommendations for a battery charger???

    Hi Bill,
    I'm at the point where I'm thinking it prudent to add a charger to my system, and thinking about grabbing a truecharge2 24v, 20a unit. Would this be the most appropriate roc for my 225ah bank? Also, what wiring and other equipment am i going to need to factor into the mix?

    System is:
    (4) 6v 225ah trojan re (24v)
    Samlex sa 600w inverter
    Classic 150
    Ms baby dc breaker box: 50a breaker (inverter), 60a breaker (cc), and a shunt with the WBjr.
    All wiring (excepting the battery interconnects) is 6awg.
    Yamaha ef200is, briggs 5550w

    Any advice on what i need and how to safely wire a charger in would be greatly appreciated.
  • BB.BB. Super Moderators, Administrators Posts: 29,489 admin
    Re: OK forget relying on panels. Recommendations for a battery charger???

    With the Yamaha you presently have--You could also look at the 30 amp charger. Your genset should be able to support it very nicely. Get the remote battery temperature sensor option.

    If you do not plan on many "deep discharge/fast recharging" cycles (in the 50% to 80% range)--The 20 amp unit would be fine too--Just longer generator run time (and perhaps a less expensive charger).

    The TC-1's had good reviews--Have not read any for the TC-2 version--But should be a very nice charger.

    -Bill

    You also need a fuse/breaker at the + battery bus to the TC 2 charger too... How long is the wiring? I would suggest that 0.1 to 0.2 volt maximum drop @ 20/30 amps for the cabling for fast/accurate charging voltage to the battery bank.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nyarelathodepnyarelathodep Solar Expert Posts: 99 ✭✭
    Re: OK forget relying on panels. Recommendations for a battery charger???

    The wiring would be less than 10 feet from gen to unit. The wiring from charger to bank is maybe five feet, at longest. With our present set up, we use an avg of 8% battery discharge daily, and the 500w of panel can give us back up to 15% on a nice winter day. But where i am in maine, nice sunny winter days are sparse. I'm thinking the charger over another two panels as a priority upgrade, though both are planned. Just occurs to me thata charger first gives me more battery conservation control.

    Aside from a fuse, is an ac transfer switch needed? Or could i just flip the pv and inverter breakers, then flip the charger breaker on for the same effect? Is 6 awg fine for a 20a charger? And lastly, should i run the charger neg through the shunt?
  • BB.BB. Super Moderators, Administrators Posts: 29,489 admin
    Re: OK forget relying on panels. Recommendations for a battery charger???
    The wiring would be less than 10 feet from gen to unit.

    Should not be a big issue... Use standard 14 or even 12 AWG residential wiring for 120 VAC.
    The wiring from charger to bank is maybe five feet, at longest.

    If you choose the 30 amp chargers, 5 foot one way run, and a generic voltage drop calculator: 0.12 volt drop
    With our present set up, we use an avg of 8% battery discharge daily, and the 500w of panel can give us back up to 15% on a nice winter day. But where i am in Maine, nice sunny winter days are sparse. I'm thinking the charger over another two panels as a priority upgrade, though both are planned. Just occurs to me that a charger first gives me more battery conservation control.

    The 30 amp of the larger charger is probably only "useful" if you will be charging under 80% state of charge--Once you get above 80%, the absorb voltage will be hit and the current will start to self limit.

    Either would be fine for your needs... A larger charger (and deeper cycled battery bank) would be more fuel efficient. A smaller charger will work fine with your 220 AH battery bank and Yamaha 2000 genset too.

    If you have lots of dark days--There is a practice of cycling the battery bank between 50% and 80% state of charge for a week at a time, and on the 7th day, recharge back over 90% state of charge.

    The theory, as I understand it, as long as the battery bank is being cycled daily through the 50% to 80% range, it will not sulfate vs just sitting for days at <75% state of charge. If I recall correctly, a poster here was told by a Rolls tech support guy that only needed to go >90% SOC once a month (that may be pushing it).

    The battery bank will be much more charge/fuel efficient when charging with a genset in the 50-80% SOC range... And very inefficient >90% SOC.

    It is your choice if you want to run 50-80% SOC (plus Sunday >90% SOC), or just run 75% to 90%+ daily state of charge. Fuel is a cost, as are batteries. Saving fuel may cost battery cycle life. I would look at what works best for your life (basically how much time/energy tending the genset + battery bank every day vs just a couple times a week type thing). Both are working for you--Don't make your life miserable.
    Aside from a fuse, is an ac transfer switch needed? Or could i just flip the pv and inverter breakers, then flip the charger breaker on for the same effect? Is 6 awg fine for a 20a charger?

    You do not need an AC transfer switch--It would be a bit more efficient if you can switch your AC inverter loads to the AC genset when the generator is running (assuming loads+charging current is less than ~80% of genset's rated output--Non-commercial gensets generally do not like running >80% rated output for many hours at a time). If you run without an AC transfer switch, your AC loads would have 85% efficient charge controller and 85% inverter eff or ~72% overall AC efficiency going through the charger+inverter with the AC genset running.

    However, if your AC loads are not great during recharging, and/or you don't want to hassle of switching AC power (possibly rebooting the DVR/Sat Receiver/etc.), worrying if your charge+AC loads are too much for the genset--Then don't worry about it. Everything will work fine.

    6 AWG would be fine for a 20 or even 30 amp DC charger output cable.
    And lastly, should i run the charger neg through the shunt?

    Depends on what you want to measure... If you want to monitor battery state of charge/current, then Battery Bus Negative=>shunt=>negative bus (all electrical connections) would be the way to go.

    If you put the charger return directly to the battery (bypassing the shunt), the Battery Monitor will be "blind" to the contributions of your AC battery charger to the overall State of Charge/Battery Performance.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nyarelathodepnyarelathodep Solar Expert Posts: 99 ✭✭
    Re: OK forget relying on panels. Recommendations for a battery charger???

    Oh wow, that's probably the most valuable piece of info you could have tendered about keeping the bank between 50-80% soc, bill. I had no idea... Probably a sign of solar newbieness, but I've been getting antsy seeing the soc below 75%, heh. With that info, i might not need to pull the trigger on anything quite yet, though when I do, it clearly makes more sense to go with the 30a unit.
    So, is it common practice then to flip the pv breakers off when your at 80-90%, or i guess the 150 must have done kind of charging parameter option to maintain the 50-80% soc schema?
  • BB.BB. Super Moderators, Administrators Posts: 29,489 admin
    Re: OK forget relying on panels. Recommendations for a battery charger???

    It is an option to run at 50-80% state of charge for a week... Some people do that around here, but it is not very common--That is likely why you have not run across this as an option before.

    And I am not even recommending that you do this... You need good deep cycle batteries (marine batteries probably would not work). And different vendors have their own ideas of what an optimal cycle is (and solar RE ain't it :roll: :cry:).

    Do some reading (perhaps contact your battery vendor) and see if this is a good plan for you. What brand/model of batteries do you have?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nyarelathodepnyarelathodep Solar Expert Posts: 99 ✭✭
    Re: OK forget relying on panels. Recommendations for a battery charger???

    My bank is 4 of the 6v Trojan t105re batteries.
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