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Help charging with generator

Hambone

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Jun 1, 2020
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I have a 48v 3kw MPP charge controller with 5kw LIFEPO4 bank. I’ve struck out twice with trying to run a generator through MPP to charge batteries and realized I can’t afford the appropriate generator that is compatible with this system. Company says I need a 4500 watt invertor generator. What would be the best DC power source to connect at the batteries and bypass MPP? What charge settings should I use? Is this the right idea? Thanks
 
What conditions have you tried when connecting the generator?

I've heard that the MPP (and likely growatt, I have yet to test mine) are sensitive to frequency variance and wont "lock on" to the generator input.
Have you tried running a restive load while connected to the MPP in an attempt to settle the output of the generator? (like a 800w heater?)

How large a generator are you useing and what do you have the MPP configure to for grid charge current? eg, are you trying to pull to many amps off the generator?

as to your question, I think the best option might be a 48v golf chart charger with the DC run into the SCC side. The golf cart charger isnt going to understand the right charge profile for the LFP batts. But run through the SCC the MPP is still going to shut off the "charge" at the right voltage for the LFP battery bank.

However for the $300 they want for a golf chart charger you might try a smaller inverter generator. You should be able to configure the grid charge current as low as 10amp which would be about 1200w so a 2kw inverter generator may do the trick for you (and be usefull in other applications)

I have a 2kw inverter geny but have yet to test it on my growatt. its on the list to do... I really should try it before the power goes out in an ice storm and I have no sun for 3 days.
 
Are you trying to charge at 120VAC or 240VAC? From another thread I've read, you might need a jumper if only charging at 120VAC. What is actually happening? As you connect the generator, are you measuring voltage at the contacts? Is the inverter noticing that the generator is there but is not accepting the power? Is the inverter oblivious that the generator is there? I believe that there are also configuration settings inside the Mpp startup menu that differenciate between 120V and 240V service.

Another issue is the setting for the charging rate. The default setting for my inverter is 140A. At 50V charging, that works out to be 7000+W. Well, I only have a 6000W generator, and I have to decrease the charging rate to let the unit accept power from my generator.

One more issue might be ramping up. The inverter evaluates the quality of the power (ie: V, Hz, ect), and decides if the generator is QUALIFIED to supply power to it. Too large a starting load can cause the voltage to drop, the frequency to fluctuate, and the inverter decides that the power is not clean, so the inverter won't accept the generator power.

You might be able to convince the inverter to accept the generator's power by starting out at a very low charge setting, say 10amps, then incrementally bump up the charging rate AFTER the inverter has accepted the generator.
 
What kind of generator are we talking about? Is this an actual genset like an Onan 5500?

More info about the "generator" would be helpful. Specs and perhaps a link?
 
What conditions have you tried when connecting the generator?

I've heard that the MPP (and likely growatt, I have yet to test mine) are sensitive to frequency variance and wont "lock on" to the generator input.
Have you tried running a restive load while connected to the MPP in an attempt to settle the output of the generator? (like a 800w heater?)

How large a generator are you useing and what do you have the MPP configure to for grid charge current? eg, are you trying to pull to many amps off the generator?

as to your question, I think the best option might be a 48v golf chart charger with the DC run into the SCC side. The golf cart charger isnt going to understand the right charge profile for the LFP batts. But run through the SCC the MPP is still going to shut off the "charge" at the right voltage for the LFP battery bank.

However for the $300 they want for a golf chart charger you might try a smaller inverter generator. You should be able to configure the grid charge current as low as 10amp which would be about 1200w so a 2kw inverter generator may do the trick for you (and be usefull in other applications)

I have a 2kw inverter geny but have yet to test it on my growatt. its on the list to do... I really should try it before the power goes out in an ice storm and I have no sun for 3 days.
My generator is a small 1800-2200watt AI Power. It’s an inverter that was tested to have a really clean sine wave. MPP responded saying I needed 1.5 times the size of the MPP inverter. Just wondering if I can buy a 10 amp dc power source and dial it up to 56 volts and call it good for emergencies
 
There is a thread on the forums about how to buy a 12v server power supply and modify it increase its output voltage.

Watch the youtube video the OP posted because he has some important info concerning max voltage output and why you cant just crank them really high. (limited by the output cap rated voltage)

IF you go that route you should feed that DC input into the SCC of the MPP and allow the all-in-one to monitor voltage etc. You'll need more than 60v input to the SCC for that to work. (optionally you could run it into the input side of a separate port BMS)
 
My generator is a small 1800-2200watt AI Power. It’s an inverter that was tested to have a really clean sine wave. MPP responded saying I needed 1.5 times the size of the MPP inverter. Just wondering if I can buy a 10 amp dc power source and dial it up to 56 volts and call it good for emergencies
These devices are mostly used for bench testing...but they sometimes come in handy for other stuff...in a pinch. You'd need to make some cables (clamps on one side, bare copper on the other) to reach the power supply and the opposing sides (+/-) of your battery bank...but this would send amps into the mix. This is a "dumb" power supply, so you'd have to keep an eye on charging...unattended, this will fry a battery bank on the top end (possibly start a fire). You'd want a proper battery monitor (percentage) and not charge over 75-85% full. Charging at 18A would be slow for your size of bank but this particular unit would supply about 1000 Watts of constant power.

***Note...this is a crappy solution and should not be considered as a permanent fix***

However, to get you out of a squeeze and buy you some time to do it the right way (bigger gennie/better charge controllers) for less than a few hundred bucks, it'll do. And in the end you'll end up with a useful tool.

 
I use a Samlex EVO 4024 Inverter/Charger which is 24V. It is capable of 100A Charge Rate (default 40A) which is programmable.
The Generator input feed line is 120VAC., I have set it to charge @ 80A which results in 120V/27A draw from the L5:30 output of the generator.
@ 120V/27A pulls 3200W +/-200W as it floats a little. This is CONSTANT DRAW so no good for a small "3000W" Generator.
I run a 7200/9000 Watt Generator which has the L5:30 (120V/30A) which I use but also has a (NEMA L14-30R) that can output 240V/30A.

I'm using a Champion 41552 Generator (not discontinued) and have never had issues with it. In fact I built my home using this genny as a power source for the air compressor, table saw etc and it has seen a LOT of use ~ I mean LOTS ~ and with religious oil changes (synthetic only) no issues.... I've never had issues with Champion products and bang for buck, can't be beat.

IF you are looking for a new Genset then consider getting one that has the ability to be started by a GCSM Module. That will let your Inverter System auto-start & shutdown the generator IF the Inverter/Charger has AGS capability.
AGS = Auto Generator Start signal.
GCSM = Generator Control Start Module.

For one of the best GCSM's see here: GSCM-mini-60Hz (USA & Canada) (atkinsonelectronics.com)
For the Generator Compatible Listings search this PDF: atkinsonelectronics.com/content/product_pdfs/All Hookup Diagrams Merged.pdf
SPECIAL NOTE: If the Generator is NOT in the Atkinson list, there is likely no chance that ANY GCSM from anyone would support it.

Also a note about Generac. The Company is now owned & operated by a Capitol Investment Company. The Bean Counters had at it and quality has TANKED. Most Generator Vendors here (and there are quite a few out here in the remote regions) will NO LONGER SELL Generac ! The quality dropped & service calls are far too frequent.

BTW: Home Standby Generators which are an excellent option (so it would seem) cannot be installed on off-grid setups. Generac, Champion and others immediately VOID Warranties for such installations. I just went through looking to install one which runs on LPG and discovered "before buying" that this was indeed the case, confirmed by the Manufacturers direct support, not just what the vendors said. (two of which did not know this detail)
 
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