How to start generator to charge batteries when battery bank depletes 50%

reckless1

Hello i have the following system setup:
Xantrex XW6048 Inverter
Two Outback Flex 60 charge controllers
Xantrex xw system control panel
Twenty Four 250 watt solar panels
16 Rolls Surette S600 (450AH) batteries

System is setup as follows:
Solar charges the batteries and supplies loads (through inverter) during the day when the sun is out
Charge controller uses a relay to activte contactor which disconnects loads from the battery when batteries reach 50%, inverter switches to AC pass through. When battery voltage reaches 57.6VDC the reconnect set point trips relay and the inverter switches from AC Pass through to Inverting and then continues to get power from the batteries.

My question is as follows:
Is there a way to have the system start my generac 13kw generator if the low voltage disconnect triggers sometime during the night when there is no sun out to recharge the batteries using the generator instead of having it switch back to the grid ($$$). I want to do this so that there is a better chance of my batteries being fully charged when the sun does come up yet not take power from the utility grid...

Sincerely,

Robin

reckless1

Re: How to start generator to charge batteries when battery bank depletes 50%

Please also note that currently if the LVD is active and the system is getting power from the grid and there is a utility failure (grid failure) the generator automatically starts until either the grid comes back online or the batteries come back up to 57.6VDC at which point the inveter goes from AC pass through to inverting and then the generator will switch off

Photowhit

Re: How to start generator to charge batteries when battery bank depletes 50%

If you have 3 sources of power, Grid, Solar and Generator, Likely the Grid is your cheapest source so I don't understand the problem with "...using the generator instead of having it switch back to the grid ($$$). "

Others will come in and let you know about the Optional XW Automatic Generator Start module.

reckless1

Re: How to start generator to charge batteries when battery bank depletes 50%

Hello Photowit and thanks for your reply, i forgot to mention that i live in kingston jamaica, and our grid costs us $0.42 usd per KWH and that rate has being steadily increasing as our dollar devalues.. thats why i would prefer to have the generator charge the batteries if it depletes during the night (would be great to be able to have the generator start and charge the batteries back up to a point and then have the solar continue during the day so that i get my full absorb time of five hours)..

robin

Cariboocoot

Re: How to start generator to charge batteries when battery bank depletes 50%

How cheap is your generator fuel?

Around here even the inverter-gens would be hard-pressed to be $0.42 per kW hour electric because the bloody gasoline is so expensive.

Says the man who has been running the gen every day for the past couple of weeks due to rain.

Automatic generator start requires a generator that can be used that way too: electric start and automatic choke. This usually means a larger, more expensive generator. Otherwise the connection, although device specific, is quite straightforward. There is the "two wire" method which sends a message of ON or OFF to the gen controls; this requires a generator that has such input or a separate control unit to interpret the signal and act on. Then there's the "three wire" method which closes one switch for 'ignition on' (and opens it to shut the gen down) and another that activates the starter momentarily, disconnecting when input from the gen is detected (running signal).

Personally I am not a big fan of automatic gen start as it is simply more things that can go wrong. Checking to be sure you've got fuel in the tank and oil in the crank before tugging the rope is much simpler and more reliable. But sometimes AGS is necessary (e.g. critical loads left unattended).

reckless1

Re: How to start generator to charge batteries when battery bank depletes 50%

morning Cariboocoot,
thanks for the response, i have a generac 13kw generator which uses propane and it is connected to a large 600lb cylinder which automaticaly starts when there is no power (this generator and fuel source can run the entire house for five days non stop). i suspect that there may be a AGS already available for this unit. what i need to know is how do i setup the system to do this. I have a XW6048 hybrid inverter which has two sources AC1 and AC2, AC1 normally connected to the grid and AC2 can be connected to the generator.
My reason for anting to do this is because we are now in our hurricane season and we are getting a lot of rain and overcast skies so my batteries are not getting a chance to charge completely everyday and almost everyday the LVD switches it back to the grid. So i am hoping that there is a way to have the inverter start the generator and start charging the batteries if the LVD activates during the night and then switch off during the day when the sun comes up, this way i stand a better chance of getting my five hours of absorption time..

sincerely,

Robin

Cariboocoot

Re: How to start generator to charge batteries when battery bank depletes 50%

Okay Robin,

If your generator normally starts on its own when the grid goes down then there should be no issue: generator input takes the place of grid power and thus should feed AC1 on your XW.

Unless the XW's AC1 input has been excluded from the circuits powered by the generator in an outage. This may have been done due to differences in power specs between the grid power and the generator's output. The way around that is to wire the XW's AC2 input to a circuit that is live when the gen starts; that way it can be programmed with parameters that meet the gen's output.

The differences will be in Voltage and frequency range. Grid power, for example, may be 240 VAC +/- 5% and frequency 60 Hz +/- 1 Hz. The generator may need wider tolerance for acceptance such as 240 VAC +/- 10% and frequency 60 Hz +/- 3 Hz. I'm not saying that is the case here, just that it would be why the XW might have been 'left off' circuits powered by the gen during an outage.

Now as for having the inverter start the gen for low battery Voltage (instead of using the gen as prime power source during an outage) this should be possible as the gen already does have AGS based on grid loss. I can see a few different ways of doing it, including some re-wiring of the AC side to make the gen detect the XW's output as grid and then have the LVD disconnect that so the gen thinks the grid is gone and starts.

Exactly how it should be done I can't say as it would be necessary to study the existing wiring first, and that is a lot of wiring. How good are you at diagnosing circuits?

BB.

Re: How to start generator to charge batteries when battery bank depletes 50%

Robin,

By the way, how much have you run the 13kWatt genset on the ~100-120 gallon tank? And does the generator draw liquid or gaseous propane)?

A 13kWatt genset will probably draw ~2-3 gallons per hour and if drawing vapor (roughly 50 hours of run time), could "freeze" the tank pretty easily in cold weather.

For example, if this page is anywhere near accurate, you would need a ~420 lb cylinder to run a 13kW genset around +30F (25% minimum full tank) to keep up with the vaporization rate (vapor draw).

I always come back to questioning the size of a genset--13kWatt is not small... My home, I could probably get away with a 1,600 Watt genset to run a refrigerator, lighting, and a bit of gas central heat in an emergency (no A/C or heating loads, natural gas for cooking/heating--your needs may be different).

And, if you are going off gird solar anyway, get an AC inverter with "Generator Support"--That allows you to use a generator sized to optimally charge/run average loads, and the AC inverter will use the battery bank to supply surge current requirements that exceed your generator's capacity.

Generators are, typically, most fuel efficient when operated at 50% or greater of their rated power... When operated at least than 50% of rated power, there fuel flow stays pretty close to 50% of rated power fuel flow (i.e., operating a generator at 25% of rated load will use about the same amount of fuel as a generator running at 50% of rated load, or ~2x more fuel per kWH generated).

-Bill

Cariboocoot

Re: How to start generator to charge batteries when battery bank depletes 50%

Bill;

If I'm reading his posts correctly it sounds like fuel consumption is the issue he's trying to solve. It seems the gen is auto-starting for any outage and the XW is being powered by that through AC2 hence the batteries aren't really doing anything. I think he wants to make the inverter the primary back-up power instead of the gen, and only have the gen fire when the batteries get low. This would save a lot of fuel compared to running a 13kW gen all the time!

BB.

Re: How to start generator to charge batteries when battery bank depletes 50%

I forgot that he is in Jamaica--So, +30F/0C days are probably not an issue.

I will still argue that the genset may be over-sized for his needs (assuming he is not running A/C).

And that I do agree with you that, over all, the genset probably costs more to run than even at $0.42 per kWH grid power--Especially when all of the losses (running generator at less than 1/2 power, using to charge a battery bank, then from battery to inverter to loads, etc.) is taken into account.

-Bill

reckless1

Re: How to start generator to charge batteries when battery bank depletes 50%

Thanks for all the responses gents,
i have taken all what has been said about the cost effectiveness of using the generator to charge the batteries conpared to using the utility, i guess i hate the utility company so much that i would rather turn on the generator than take power from them to charge the batteries.. i guess if i decided to do this i could shut the inverter down to simulate a power failure which would turn on the generator and then the batteries would recharge wthout a load which would be a lot quicker than charging them under load..

thanks again for all the responses..

robin

AuricTech

Re: How to start generator to charge batteries when battery bank depletes 50%

How often does your system use the generator?

If it's a daily thing (or nearly so), could you set up your generator on a timer to run from a couple of hours before sunrise to an hour or so after sunrise? If so, you could use your generator for early-morning loads and bulk charging (thus getting to at least 50% generator capacity for its limited runtime), then use your PV system for daytime loads, absorption charging and (ideally) float.

reckless1

Re: How to start generator to charge batteries when battery bank depletes 50%

Hello Gents,

i got the system setup to start the generator and now i have another question, Can the xantrex xw-6048 be setup with grid on AC1 and generator on AC2 so that when there is a low voltage disconnect the xantrex switches the house load to AC1 (GRID) and then the generator starts and the xantrex charges the batteries from AC2 this way the batteries would recharge without a load..

sincerely,

Robin

Cariboocoot

Re: How to start generator to charge batteries when battery bank depletes 50%

reckless1 wrote: »

Hello Gents,

i got the system setup to start the generator and now i have another question, Can the xantrex xw-6048 be setup with grid on AC1 and generator on AC2 so that when there is a low voltage disconnect the xantrex switches the house load to AC1 (GRID) and then the generator starts and the xantrex charges the batteries from AC2 this way the batteries would recharge without a load..

sincerely,

Robin

Er, why?
If grid is on AC1 loads on the XW's AC OUT are powered by the grid and the batteries will be charged by the grid. There would be no LVD active then.
The idea is that if AC1 goes inactive (power outage) the XW will power loads on AC OUT from the batteries, and if the solar can't keep the batteries charge the gen starts and powers loads/charges through AC2.

CDN_VT

Re: How to start generator to charge batteries when battery bank depletes 50%

Mr Robin
The generac 13kw generator has it also got the external Safety switch-over panel & breakers ? then you might need the XW to sync in the phase rather than Aux 1 leading the phase sync. As with propane freezing etc , Kingston Jamaica , if that happens on a 600# PIG , than strap a case of red beer onto it . The generac is not a syncing system , it's a throw switch for one supply to the gen set. Phase syncing is very important here, or smoke will be let out & blown away . As with the auto start of the propane screaming 3600rpm gen set , this can be done through a relay from the your system and cuts the feed of AC to the genset control board ,there are two ac wires that feed the genset & the other two #14 AWG wires control the safety switch over ( KLUNK , we have light ) . not the main AC out wires.

VT

reckless1

Re: How to start generator to charge batteries when battery bank depletes 50%

Hello Cariboocoot,
thanks for your reply they way that i am setup is i have two outback charge controllers and both have aux relays, CC1 uses the AUX relay LVD to switch a contactor which disconnects the loads from the xantrex\batteries (AC pass through) and allows the Grid to feed the loads on AC1(in case generator does not start) CC2 uses the AUX relay to start the generator when the LVD threshold (set to come on before LVD on CC1) and feed the loads/charger on AC2. I wanted to know if the threshold for CC2 is reached and then generator starts if the xantrax can see the voltage on AC2 and switch the loads to AC1 yet allow the genset to charge the batteries from AC2 (no load on batteries while charging)..

robin

Cariboocoot

Re: How to start generator to charge batteries when battery bank depletes 50%

reckless1 wrote: »

Hello Cariboocoot,
thanks for your reply they way that i am setup is i have two outback charge controllers and both have aux relays, CC1 uses the AUX relay LVD to switch a contactor which disconnects the loads from the xantrex\batteries (AC pass through) and allows the Grid to feed the loads on AC1(in case generator does not start) CC2 uses the AUX relay to start the generator when the LVD threshold (set to come on before LVD on CC1) and feed the loads/charger on AC2. I wanted to know if the threshold for CC2 is reached and then generator starts if the xantrax can see the voltage on AC2 and switch the loads to AC1 yet allow the genset to charge the batteries from AC2 (no load on batteries while charging)..

robin

I take it you are trying to power loads without the grid even though the grid is present? This leads me to ask "why?" again as grid power is almost always cheaper than solar.

If CC2 sees low Voltage and activates the generator that should apply power to the XW's AC2 input and power the loads on AC OUT while charging batteries.

If CC1 sees low Voltage it would switch in the grid to AC1 which will power the loads on AC OUT and charge the batteries.

Batteries never have a load on them while charging via the built-in charger: it operates either as an inverter or as a charger but not both at once.

The biggest problem with such a system (aside from redundancy) is programming the controllers so that the gen is started first and the grid switched in only if the gen fails and Voltage continues to drop. Then there is the issue of making sure the reconnect Voltages allow sufficient charging before switching back to inverter power (otherwise some fairly quick cycling could occur).

Incidentally you could also have a circuit to detect the generator's failure to start and switch the grid on to AC2 instead of using CC1 on AC1, but as the system is already overly complex I'd advise against it.

reckless1

Re: How to start generator to charge batteries when battery bank depletes 50%

Thanks Caribooboot,

i am finally getting a good understanding of how this inverter works, i was previously thinking that the batteries where being charged under load (you have now clarified this), so what i will do is leave the genset on AC2 (priority) and the AC1 (grid), when the LVD comes on at 50% DOD then the AUX relay will come on and start the genset. When AC2 sees power it will switch to the generator as the source for charging the batteries (i will also use contactors at this point to divert the house loads back to the grid so that i can get the maximum charging from the genset instead of having it charge the batteries and supply the load) once the battery voltage reaches 57.6 volts the system will switch off the genset and reconnect the house loads and then continue running from battery (usually at this point the sun would be back up and will continue charging the batteries but will have the rest of the day for absorption and fully charge. People ask why i am doing this as the generator is more expensive to run to charge the batteries than the grid, this is true however here in jamaica the cost to replace batteries is very expensive (very high duties) and i prefer making sure that i get my battery bank fully charged everyday and not deplete more than 50% DOD. My genset does not come on very often unless we have a couple of days of overcast skies (and it will only run for about 3-4 hours) and at the end of the day i DETEST the monopoly that the power company has... Thanks again for your advise..

sincerely,

Robin

reckless1

Re: How to start generator to charge batteries when battery bank depletes 50%

In case i did not mention before i have a 6000 watts of solar panels for charging the system and 900ah of battery storage...

ZoNiE

Re: How to start generator to charge batteries when battery bank depletes 50%

Hi Reckless,

It seems to me that if you hate to pay the utility, and don't mind spending more on fuel, and you have a battery bank anyway, why grid tie? I'd disconnect the grid and only use it as a backup to the genset, if it failed, or was undergoing overhaul, etc. Wire your system so that LVP fires up the genset, and totally ignore the grid unless you need it, and then manually switch it in...

You may find that it is more cost effective to add more storage capacity and disconnect completely, thus saving the usual minimum monthly fee just to be connected, and it's associated taxes. Add another Pig and double your fuel capacity so when one goes empty, you have some time before the truck comes out to refuel.

My 2 cents.

snazzy

Re: How to start generator to charge batteries when battery bank depletes 50%

Hi Robin, Atkinson Electronics makes a great automatic generator control module. You can contact them and inquirey what you'd need for your system. I have a Outback inverter and a three wire start generator. Robert at Atkinson's designed what I needed and gave me instruction how to hook it up. Worked perfect! Good Luck, Snaz

Robert Kendell
Circuit Board Division Manager/
Customer Service Engineer
Atkinson Electronics Inc
14 West Vine Street
Salt Lake City, Ut. 84107
1-800-261-3602 ext 7911

reckless1

Re: How to start generator to charge batteries when battery bank depletes 50%

Thanks all for the info... much appreciated..

reckless1

Re: How to start generator to charge batteries when battery bank depletes 50%

Good morning all,
i have had my system setup so that when the battery depletes 50% the load disconnects and goes back to the grid and at the same time the generator (13kw)starts and supplies power to AC2 (priority) which charges the battery (not powering any loads). I was hoping that i could get up to 70amps dc charging the batteries (at this charge rate AC2 legs show about 38-40amps being pulled from the generator which has a 55 amp breaker), however i have noticed that the inverter will start charging and then all of a sudden stop charging then a minute later start charging again, unless i reduce it below 50charging amps does it stabilize however i have seen it stabilize at 60 amps.. so there really does not seem to be any rhyme or reason for this.. WHAT would cause the inverter to stop charging and then wait for a couple of seconds and restart..

sincerely,

Robin

Cariboocoot

Re: How to start generator to charge batteries when battery bank depletes 50%

It's a Xantrex XW: they do this. Particularly at high charge rates. It has to do with handling the heat generated at higher currents. There can be a lot of heat at full power, and if it is sustained something will fry.

BB.

Re: How to start generator to charge batteries when battery bank depletes 50%

If the XW is programmed for a 55 amp breaker, then it would probably draw:

• 55 amps * 0.8 NEC derating of electrical circuits+breakers = 44 Amps max continuous draw

So--that is pretty close to what I would expect.

Also, remember that these are usually "constant power" chargers... When the battery is running at lower voltage charging, you will get more current:

• 44 amps * 240 VAC * 0.9 efficiency (guess) = 10,560 Watts of charging power
• 10,560 Watts / 52 volts charging (low SOC battery) = 203 Amps DC Charging
• 10,560 Watts / 59 volts charging (high SOC battery) = 179 Amps DC Charging

But--I must be misunderstanding you.... That is way too much power/current for any standard inverter/charger. You would looking for 70 amps DC charging? And had ~40 amps on the AC side? Is this a 120 or 240 VAC input inverter/charger?

-Bill

Cariboocoot

Re: How to start generator to charge batteries when battery bank depletes 50%

BB. wrote: »

I
But--I must be misunderstanding you.... That is way too much power/current for any standard inverter/charger. You would looking for 70 amps DC charging? And had ~40 amps on the AC side? Is this a 120 or 240 VAC input inverter/charger?

-Bill

Bill; XW input is 240 VAC. 6kW output for loads leaves about 3600 Watts or 75 Amps DC for charging, inverter power, and losses. Without the output maxed there would be no problem. However these things do crank back charging based on how hot they get and even drop it.

reckless1

Re: How to start generator to charge batteries when battery bank depletes 50%

Thanks guys i will leave it alone and let it do its thing....

robin