MPP LV6548 charging

Otisd85

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I have 4 lv6548 inverters, and I'm currently trying to learn how to set up the first 2 in a temporary fashion at my current home, before I take them and my 64 CATL lifepo4 cells to my off grid build site with no internet or cell service.
I have charged and discharged my cells a couple cycles now trying to get my parameters right, but I'm having an issue with charging when my inverters are on.
If the inverters are off, they'll accept AC charge current from my service panel and they do not produce AC. When I turn the inverters on, they stop charging and start producing 120v AC, but I can't get them to charge while producing AC.
My end goal is to be able to run a generator to charge the batteries while the inverters are still powering my house, and that isn't going to work if my inverters have to be off to charge.
Any help would be greatly appreciated.
 

BentleyJ

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You stated "but I can't get them to charge while producing AC". Unless I'm reading your description above wrong, it seems like you are expecting the inverter to draw current from the battery to power loads while simultaneously charging the battery from utility power or a generator. Since the battery is connected by only 1 Pos+ and 1 Neg- cable it is impossible for current to flow in both directions at the same time.
There are 2 ways to accomplish what you need.

1) The generator has to be large enough to power all the loads in your house AND have enough left over to charge the batteries via the internal charge controller in the LV6548. This is sometimes referred to as Pass-Through mode. In the program set up for the inverter you would most likely want item 01 to SBU priority (Solar, Battery, Utility) so the generator will only need to run after the battery voltage drops to the lower set limit. Program Item 16 probably should be set to SNU which is the default.

2) Purchase a separate, 48V charger that is suitable for LFP batteries. Plug it directly into the generator and connect it to the batteries. This will configuration will in fact charge your batteries while the Inverter is running your house.
 

Lt.Dan

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I've had the same question. See this thread:

 

iamrich

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1) The generator has to be large enough to power all the loads in your house AND have enough left over to charge the batteries via the internal charge controller in the LV6548. This is sometimes referred to as Pass-Through mode. In the program set up for the inverter you would most likely want item 01 to SBU priority (Solar, Battery, Utility) so the generator will only need to run after the battery voltage drops to the lower set limit. Program Item 16 probably should be set to SNU which is the default.
Would AC input be the same as a generator input? As long as the AC in is enough to power the house and have some left over, it should also charge the batteries, no?
 

BentleyJ

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Would AC input be the same as a generator input? As long as the AC in is enough to power the house and have some left over, it should also charge the batteri1 es, no?
The LV6548 has 1 AC input for either Utility OR Gen. Yes, if sufficient power is available the Inverter should go into pass thru mode powering the house load and the extra would be used by the Inverter to charge the batteries.
 

iamrich

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I have charged and discharged my cells a couple cycles now trying to get my parameters right, but I'm having an issue with charging when my inverters are on.
If the inverters are off, they'll accept AC charge current from my service panel and they do not produce AC. When I turn the inverters on, they stop charging and start producing 120v AC, but I can't get them to charge while producing AC.
What are your settings for:
#2
#11
#16
 

Otisd85

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You stated "but I can't get them to charge while producing AC". Unless I'm reading your description above wrong, it seems like you are expecting the inverter to draw current from the battery to power loads while simultaneously charging the battery from utility power or a generator. Since the battery is connected by only 1 Pos+ and 1 Neg- cable it is impossible for current to flow in both directions at the same time.
There are 2 ways to accomplish what you need.

1) The generator has to be large enough to power all the loads in your house AND have enough left over to charge the batteries via the internal charge controller in the LV6548. This is sometimes referred to as Pass-Through mode. In the program set up for the inverter you would most likely want item 01 to SBU priority (Solar, Battery, Utility) so the generator will only need to run after the battery voltage drops to the lower set limit. Program Item 16 probably should be set to SNU which is the default.

2) Purchase a separate, 48V charger that is suitable for LFP batteries. Plug it directly into the generator and connect it to the batteries. This will configuration will in fact charge your batteries while the Inverter is running your house.
The LV6548 has 1 AC input for either Utility OR Gen. Yes, if sufficient power is available the Inverter should go into pass thru mode powering the house load and the extra would be used by the Inverter to charge the batteries.
I expect to charger to charge the batteries with the AC input, while the inverter is producing AC output. It seems that if the AC output load is less than what the input is seeing then the excess should go to the charger and then batteries. Then as the load increases it should start to discharge from the battery. As it sets right now, probably because I don't have things configured properly, I cannot get the inverters to charge while they are powered on. When they are off, they charge. When they're on they won't charge, even if there's no load on the output.
 

Otisd85

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I've had the same question. See this thread:

Dosen't seem you resolved the issue, you just bought a external charger?
I have a gas 8500 watt generator I plan on using a 7200w, 240v split phase at 30 amps, until I figure out if I'm going to need a bigger probably diesel generator.
I may end up getting a small charger like on your thread for occasional emergencies, but for my situation, that wouldn't be feasible for long term regular use. I'd need 4 just to get started and that seems unnecessary when my inverters already have charging capabilities.
 

Otisd85

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Would AC input be the same as a generator input? As long as the AC in is enough to power the house and have some left over, it should also charge the batteries, no?
This is my thought, and to add to it, if AC output exceeds AC input, it should draw the balance from the batteries.
 
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BentleyJ

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In reviewing the user manual for the LV6548 I noticed an issue that is not clearly defined. Specifically WHAT condition(s) trigger a battery recharge, so we have to make some logical assumptions. Since menu #01 is set to SBU that enables menu items #12 & #13.
#12 is the voltage setting at which the Inverter will switch back to Utility or Generator (Pass Through or LINE mode) and theoretically start charging the battery.
#13 is the voltage setting at which the Inverter will consider the battery fully charged and switch back to Inverter mode and draw from the batteries.
Try these settings:
01 = SBU
12 = 51V (range is 44v to 51V) Seems like NO battery charging from generator will occur until batt voltage falls to this threshold.
13 = 55V (range is 48v to 62V)
16 = SNU (NOTE: this menu item states that charger source setting is valid ONLY if the Inverter is in LINE, Standby or Fault mode. Otherwise the batteries can ONLY be charged if solar is available) Therefore even with your generator is running, if the battery voltage has not fallen to the value set in #12, charging will not initiate.

Let me know if this works.
 

eabyrd

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Is solar available? The only combination I can use to get the 6548 to charge the batteries is Utility first, combined with SNU in those cases.
 

BentleyJ

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Is solar available? The only combination I can use to get the 6548 to charge the batteries is Utility first, combined with SNU in those cases.
Interesting, I was thinking about what happens with Utility First. Is charging initiated by the Low Voltage Cut Out value or perhaps the charger is always ON when utility is present. Is this the case?
 

eabyrd

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Interesting, I was thinking about what happens with Utility First. Is charging initiated by the Low Voltage Cut Out value or perhaps the charger is always ON when utility is present. Is this the case?
I've only set it that way as an override in conjunction with SNU to force charging from the grid and from solar to the batteries. I've not experimented beyond that.
 

Otisd85

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Is solar available? The only combination I can use to get the 6548 to charge the batteries is Utility first, combined with SNU in those cases.
I do not have solar available yet, but have plans for it. I'm trying to work out some of the bugs at my on grid home with the input hooked to my breaker panel like a normal appliance, before i take this system to my off grid location where I'll set up the solar panels.
 

Otisd85

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In reviewing the user manual for the LV6548 I noticed an issue that is not clearly defined. Specifically WHAT condition(s) trigger a battery recharge, so we have to make some logical assumptions. Since menu #01 is set to SBU that enables menu items #12 & #13.
#12 is the voltage setting at which the Inverter will switch back to Utility or Generator (Pass Through or LINE mode) and theoretically start charging the battery.
#13 is the voltage setting at which the Inverter will consider the battery fully charged and switch back to Inverter mode and draw from the batteries.
Try these settings:
01 = SBU
12 = 51V (range is 44v to 51V) Seems like NO battery charging from generator will occur until batt voltage falls to this threshold.
13 = 55V (range is 48v to 62V)
16 = SNU (NOTE: this menu item states that charger source setting is valid ONLY if the Inverter is in LINE, Standby or Fault mode. Otherwise the batteries can ONLY be charged if solar is available) Therefore even with your generator is running, if the battery voltage has not fallen to the value set in #12, charging will not initiate.

Let me know if this works.
I've changed the settings to what you've suggested, I'll see what it does once my voltages gets that low and let you know.
This isn't really what I'm looking for though, I'd like the input to charge when available regardless of the voltage. If the sun has gone down and I'm at 52 or 53 volts, and I'm starting my generator before bed, I don't want it to run for no reason, I also don't want to get up in the middle of the night if I can help it.
When you plug in your phone before bed, it charges until full, it doesn't matter if it's at 30, 50, 70, or even 99%, it starts charging when you plug it in. It doesn't wait until it's almost dead and start charging at the last minute.

Also, I don't read it at pass through and line mode being the same, but maybe I'm wrong.
 

RCinFLA

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If the inverters are off, they'll accept AC charge current from my service panel and they do not produce AC. When I turn the inverters on, they stop charging and start producing 120v AC, but I can't get them to charge while producing passing through input AC to AC output.
I think that may be clearer way to describe your issue.

I am not 100% sure about this but your problem may be the inverter's second stage PWM chopper (or just inverter as you call it) was off before input AC was applied. When inverter (first and second stage) is providing AC output, then AC input is applied, the PWM sinewave chopper will slew its sinewave creation to synchronize to applied AC input. After this AC synchronization is completed (takes a minute or two) then you will hear the internal connect relays clunk sound indicating the AC input to inverter AC output is running in parallel.

Try having inverter running on batteries, before you apply AC input. See if this solves your problem. The problem may be if the inverter was off before you applied AC input it will pass through AC input to AC output but will not later be allowed to activate inverter PWM chopping to charge battery due to inability to synchronize inverter to AC input.

Another possibility is the inverter is not synchronizing to incoming AC properly. This could be a calibration problem with inverter's phase locking to match inverter phase to incoming AC phase. Inverter synchronization does not actually compare inverter output to AC input phasing. It modifies its PWM sinewave creation digital sequence based on AC input phase before connect relays are closed. There are software delay calibrations so when it does start up inverter it should be in phase with AC input.

Some more technical details:

When you say 'inverter' it is a bit too encompassing when talking about a HF hybrid inverter. What you are calling inverter has two stages. First is battery DC to high voltage DC converter (around 180 to 300 vdc). Second stage is IGBT transistors that PWM chops the HV DC to synthesize AC sinewave.

For HF hybrid inverters, it is tricky to design a bi-directional battery DC to HV DC converter. Many of the Chinese HF hybrid inverters don't even try. They just put a forward one-way battery DC to HV DC converter for normal battery to AC output operation and a reverse HV DC to battery DC buck converter to charge battery.

I believe the LV6548 has a forward only DC to HVDC for normal battery to AC output operation and a separate paralleled HV DC to battery DC reverse buck converter to charge batteries. They cannot both operate at the same time.

When grid AC or generator AC input is applied, it will get passed through to AC output, through the internal connect relays. If battery needs charging it taps into the AC input feed to charge the HV DC filter capacitor, then the buck converter drops HV DC down to battery voltage. The forward DC to HV DC converter must be off during charging. If inverter was producing AC output before AC input applied, it must adjust its inverter AC phasing to match incoming AC phase before connect relay closes with input AC. If inverter is not operating before AC applied the connect relay closes almost immediately, as there is no inverter synchronization required.

There are two ways AC input to HV DC can be done depending on HF inverter manf./model. Simple-stupid way is rectifier diodes in parallel with IGBT output devices just rectify AC input to charge the HV DC capacitor. This method has a poor charging AC input power factor.

Second way to charge HV DC filter capacitor is to have output IGBT devices PWM chop, similar to sinewave creation process, and with PWM filter inductor it charges HV DC filter capacitor. This is more complicated as PWM chopping must be synchronized to incoming AC but provides a good AC input power factor during charging batteries.

HF hybrid inverter block diagram.png
 
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BentleyJ

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I've changed the settings to what you've suggested, I'll see what it does once my voltages gets that low and let you know.
This isn't really what I'm looking for though, I'd like the input to charge when available regardless of the voltage. If the sun has gone down and I'm at 52 or 53 volts, and I'm starting my generator before bed, I don't want it to run for no reason, I also don't want to get up in the middle of the night if I can help it.
When you plug in your phone before bed, it charges until full, it doesn't matter if it's at 30, 50, 70, or even 99%, it starts charging when you plug it in. It doesn't wait until it's almost dead and start charging at the last minute.

Also, I don't read it at pass through and line mode being the same, but maybe I'm wrong.
I completely understand how you would like the charging to work, it makes perfect sense. Unfortunately what we want and what the Inverter is capable of are not always the same. I have a similar issue with a Conext XW+ with regard to the peak load shaving settings not being favorable to convenient operation. Its almost like the engineers who design these Inverters have never actually used them!!

The only other idea I have is to try setting menu 01 to USB, perhaps in this mode when the generator is on it will carry the load and charge the batteries per the settings in 26 & 27. However, its possible that charging will not be triggered unless the LVCO (menu 29 value) is reached. Since the user manual is unclear regarding this issue, all one can do is try it an see what happens.
 

Otisd85

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I'm still working on this problem, I've contacted mpp solar, they want me to send data logs from watchpower after the inverters have been in a while. They haven't said the inverters won't do what I'm asking, but they haven't said they will either.

I have a 8500w split phase 240v generator with a 30a breaker. If I have 2 of the inverters charging at 60a, that should be below my 7200w threshold for the breaker. With charging set at 60a it's still unclear if when in line or bypass mode if it'll be charging at the set amount and overload the generator if anything else comes on, or if it'll take from the charging circuit until it exceeds 7200w before it trips the generators 30a breaker.

Each inverter(x4) will charge at 120a x battery voltage, currently set at 56v, for a total of 26,880 watts. I have 100a panel for the inverters to supply power that'll run the house, so that's another 24kw.
Will a generator >27kw supply the house and charge the batteries when the house load is less than max? Or, do I need a generator that produces 50kw+ so that I can set the chargers at 120a and not worry about the rest of the load from the house overloading the generator?
 
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