High charge rate options with Xantrex? (xanbus)

Audiomaker
Audiomaker Solar Expert Posts: 100 ✭✭
in Off Grid Solar & Battery Systems #1
Ok folks, maybe you could help me with this?

I just moved from a Xantrex RS3000 to a Xantrex xw6048.

Both of these systems are "Xanbus" enabled and a lot of you know that this means they have nifty little control panels to tweak the system with...

The control panel for the XW6048 is pretty similar to the smaller RS3000 and both have this similarity...

In the charger configuration, you are allowed to set both the ah rating of your bank, and the percentage of rate.

But here's the thing... when I had my RS3000 I just assumed that "100%" was the appropriate setting for the rate (I was running 300ah @ 12v grp 31's).

That was charging that bank at about 60a bulk. I didn't give it much thought.

Now with the XW6048 I have the same options (but now I have a 200ah @ 48v bank ready to destroy).

I should mention that I'm running 100% on generator power at this time.

Initially I thought this charge rate percentage adjustment was to allow for less load on the source, and I used it as such.
At the first charge of this 48v bank, the 6048 put such a load on my 7kw genny that it scared the crap out of me. I immediately set the charge rate down to 50% (which pulls about 3500w at the start of bulk).

So where am I going with this? Well, at 50% charge rate entered, and a 200ah bank entered, the charger is still starting with a good 50adc to the batt's, but most of my reading has led me to believe that C/8 or so are maximums (i.e...13% to 20%).

So why would a Xantrex be putting 50a to a bank when it's set at half rate? Is the BTS supposed to compensate if I put the charge percentage at 100% (upwards of 80+amps).

Is there some math I missed where this is ok, or is there some other type of battery where it's ok to put 60-100amps into a 200ah bank?

You see, I would presume Xantrex knows what it's doing...at least in these higher end inverter/chargers, and I also presumed that the charger does some adaptation when you enter 200ah as the bank capacity?

For now, I have it set at 50% rate (again, about 50a at bulk, or C4ish). That let's me go into bulk and use the microwave at the same time as far as the generator is concerned, but my understanding is that this is still a high charge rate. Why would 50% end up being a high charge rate when the inverter knows the size of my bank?

There ya go, I guess I've rephrased that in as many ways as possible.

Ideas?

Sean
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
    Re: High charge rate options with Xantrex? (xanbus)

    Attachment not found.Are you using the ComBox or the SCP to control/program the inverter ? Combox with web interface to computer is easier.

    So you have to get out your XW6048 manual, and read up (in the appendix) about these settings:
    Battery Size

    AC2 breaker size (generator input)
    Max battery charge rate (in % of bank size)

    Generator Support
    Generator Support amps
    Generator support +
    I am assuming your XW6048 is configured for 240VAC output (and 240VAC gen input @ AC2)

    First thing to set, is AC2 breaker size. If you don't use a breaker in your transfer panel, what is the breaker size on the genset ? Use the smaller breaker as the size to input. This limits the XW to only use 80% of that size. Keeps you from overloading the genset, or tripping a breaker.

    Set your battery bank (in amps) size. This is used somehow, to calculate % of charged, IF you set your charge voltage set-points right.

    Max charge rate of a 200ah bank, should be maybe 20A, maybe bulk it at 40A to save fuel, but you have to watch out for BBQ your battery plates at high rates

    Enable Gen Support & Gen support +, That lets you run un-balanced loads off the genset while you are charging batteries. If loads get too high, the charger gets throttled back, and if a huge load kicks on, the inverter kicks in to assist it. (we assume it's just a short term load, like a blow dryer) as soon as loads ease up, the charger comes back on-line.

    So watch the reading in the appendix, some of the settings are split over the 2 AC phases/breakers and some are not, sneaky bastards wrote the manual, and they left out the decoder ring.
    If you have the Combox, you can slowly dial up the loading and watch the display of what everything is doing, and get it really nailed solid.

    What I have set for my small 3Kw genset at 1400' elevation: (derated to about 2500w load, 48V 800ah battery)

    Battery Bank Capacity 1000 A (1,000A makes for easy, direct conversion to charging amps,
    mistakes are limited to AC2 & Generator Support amps limits)
    Maximum Charge Rate 5-35 A

    AC2 Breaker Size 19.5 A (each breaker is only @ 120V so both will add, this setting = a limit of 4680w, derated to 3744w)

    Generator Support Enable Enabled
    Generator Support amps 13.1 A (each breaker is only @ 120V so both will add, this setting = a limit derated to 2515w)
    Generator Support PLUS Enabled

    Combox & remote PC enable getting the 13.1 settings vs whole #'s via SCP.
    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 ,

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  • Audiomaker
    Audiomaker Solar Expert Posts: 100 ✭✭
    #3
    Re: High charge rate options with Xantrex? (xanbus)

    Thanks Mike,

    I don't have a ComBox yet (I just discovered their existence). I do of course have an SCP.

    My genny can handle the load, that's not an issue so much as this line you wrote:

    "Max charge rate of a 200ah bank, should be maybe 20A, maybe bulk it at 40A to save fuel, but you have to watch out for BBQ your battery plates at high rates"

    I have the bank capacity set on the SCP for what it is...200ah (at 48v of course).

    The nature of the XW6048 is that it is designed to...charge batteries, but if I had left the "Charging Rate" setting at 100%, it would try to push close to 80a into my bank even though the system is set at 200ah.
    The default setting on the XW6048 is 100%, so I figured that anything less was a derating (i.e...be extra nice to your batt's, or lower your load on the solar/genset).

    It makes me wonder why the 6048 would allow you to put 80a into a 200ah bank under any conditions, let alone have it be the default setting.
    Not having looked at their charge profile, I thought at first that maybe it was acceptable to blast the bank in bulk like this until the BTS told it to throttle back, but even with my BTS hooked up and working, the 6048 still puts out 60amps right even into absorption using 75% charge rate. I have to dial the charge rate all the way back to 50% to get 50a during bulk (and some time into absorption).

    To get to 20a, I'd probably have to set the charge rate to 25% or less.

    Looking at these numbers, and being as the XW6048 is a 100a charger, I could almost speculate that setting the bank capacity has no influence on the charge rate.
    Maybe the charge rate setting is simply tied to the max charge capacity of the 6048?
    I mean, it's pretty darned close. Set it at 75%...get 60+amps. Set it at 50%....get 50amps.

    What I *thought* happened was that setting the charge rate yielded a percentage of the correct rate for the bank.
    (200ah bank should be charged at 20a, so a 50% rate setting would yield half of that, or 10a ... etc).

    If not, and the charge rate is not tied to the bank capacity, but instead to the overall charger capacity, then that might explain why I fried a bank with my RS3000 (which had the same scheme).


    On the other hand, maybe it's ok to blast a 200ah bank with 80+amps (I haven't set the charge rate back to 100% since the first try, so I can't confirm that number, but it was a serious load on the generator).
    I mean, I have charged some 100ah automotive batteries before using 60, or even 100 amp consumer chargers (to get the car started, not as an off grid solution).

    The Xantrex however is not a jumpstarter, or an automotive car charger. It is designed by people who know the correct charge rates for off grid banks, and I just can't figure out why it would put so many amps towards a bank as the default?

    I think I'm going to set it back to 100% (at 200ah) and see if it blasts 100a into the bank and draws 4800w+ from my generator....just for a minute to see if it will.
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  • Audiomaker
    Audiomaker Solar Expert Posts: 100 ✭✭
    #4
    Re: High charge rate options with Xantrex? (xanbus)

    UPDATE:

    Yeah, I did it this morning. I set the max charge rate back to 100% and double checked that the capacity was set at 200ah.

    Guess what? 98.5a charge rate and over 6kw load on the generator.

    Looks like setting the battery capacity has little to do with the charge rate. No wonder I toasted that last bank :(

    I must confess that up until this week, I had put little attention into the safe recharge rate of my batteries. I assumed the Xantrex (RS3000) was more *automatic* than it is, and that default settings would be reasonably within margin until I fine tuned the system.

    I would have never noticed. Both the RS3000 and XW6048 are 100a chargers. The difference being that one is 100a @ 12v, and the other @ 48v. The wattage difference being significant to my generator...which is what prompted me to immediately address things by setting the max charge rate down.

    This should be a big warning right up top in the Xantrex manual. That the idea of setting your capacity and going with the systems defaults is ok.... Wrong.

    The Xantrex manual falls on it's face here for not warning the user and the system falls on it's face for not having a lower number be the default value (like 10%).

    I'm going to start warning Xantrex users about this (at least those with the Xanbus systems where we think setting the Ah capacity is also setting the nominal charge rate for the system).

    Ugh
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #5
    Re: High charge rate options with Xantrex? (xanbus)

    Yea--Software can highly automate stuff and make it more confusing too--Because it is unclear at times what "Things" they have automated and what they have not.

    Another possible one is, as I recall on the older XW inverter-chargers, the battery volt meter displays temperature corrected voltage, not the actual battery voltage--So a very cold bank will have actual battery voltage over what the XW displays (and lower voltage for a hot battery bank).

    But some of the voltage settings (like equalization) are not temperature corrected (as I recall).

    Trust but verify.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Audiomaker
    Audiomaker Solar Expert Posts: 100 ✭✭
    #6
    Re: High charge rate options with Xantrex? (xanbus)
    BB. wrote: »
    Trust but verify.

    -Bill

    No doubt on that one.

    What really threw me off was that the system shows the Max Charge Rate as a percentage.

    Dumba$$ me thinking this is a percentage of a calculated charge profile, not of the maximum capacity of the charger.

    Had they written that setting as straight amps, I would have caught on (Max Charge Rate = 50a ...etc).

    On the RS, I let it go... I figured Xantrex must have it right. It seemed high, but who was I to argue? A month later my bank is smoked.

    I guess the bright side is that now having moved to the 6048, that the high load it put on my genny @ 100% caused alarm and I set it down right away.

    Live and learn. It was only a few hundred bucks worth of batt's.
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