Topping up batteries from normal 15A wall outlet

[jar349]

I have 2 EG4 48v 100 AH rackmount batteries (LiFePo4) in parallel that will be charged by a growatt inverter getting its power from solar panels. After a string of cloudy days, the batteries can run low and I'd like to be able to charge them using something I can plug into a normal outlet in my home.

Since it is also made by EG4, I was considering this: https://www.signaturesolar.com/products/48v-5a-120v-battery-charger-by-eg4

But what is unclear to me is how I would hook it up to my battery bank correctly given that I'll be using the rack from signature solar that has a bus bar in it.

 

[houseofancients]

why not let your growatt do the charging ?

 

[sunshine_eggo]

I have 2 EG4 48v 100 AH rackmount batteries (LiFePo4) in parallel that will be charged by a growatt inverter getting its power from solar panels. After a string of cloudy days, the batteries can run low and I'd like to be able to charge them using something I can plug into a normal outlet in my home.

Since it is also made by EG4, I was considering this: https://www.signaturesolar.com/products/48v-5a-120v-battery-charger-by-eg4

But what is unclear to me is how I would hook it up to my battery bank correctly given that I'll be using the rack from signature solar that has a bus bar in it.

If you have a Growatt inverter/charger (most are), then you simply need to connect the AC-in of the unit to the 15A outlet. Consult your manual.

It is important that you not exceed the 15A outlet limit, and if you're using loads, you will have to consider loads+charging as it will pull from Grid to power loads when charging regardless of priority. You also need to consider anything else pulling power from that circuit in your house.

There is a setting to limit AC charging. It's battery current, not outlet current. Setting 13 is the cut-off voltage for AC charging. Let's say it's 58V. 15A * 120V = 1800W. 1800W/58V = 31A, so you will need to limit your AC charging to 31A or less (recommend 25A for some margin).

Also, if battery voltage is above the value in setting 12, the AC charger will not charge. You will need to raise setting 12 above the battery voltage to force charging.

Lastly, the Growatt charger is a simple on/off charger. ON at setting 12, OFF at setting 13. No absorption or float phases.

 

[jar349]

I thought that the consensus on this forum was that the Growatt 5000 ES is safe so long as you don't use the AC input? That's why I was trying to avoid using the AC in on the growatt.

Do you disagree?

 

[sunshine_eggo]

I thought that the consensus on this forum was that the Growatt 5000 ES is safe so long as you don't use the AC input? That's why I was trying to avoid using the AC in on the growatt.

Do you disagree?

Sorry. I didn't realize it was EU spec. Never mind. Yeah, you'll need a suitable 120VAC 16S LFP charger.

 

[jar349]

it's my own fault for not saying which model I had up front.

Most 120VAC battery chargers under 15A have alligator clips to be placed onto the battery terminals. In my case, should I clip those to the position and negative bus bars in my rack?

How to correctly hook up alligator clips to an in-rack busbar is probably my real question.

 

[houseofancients]

I thought that the consensus on this forum was that the Growatt 5000 ES is safe so long as you don't use the AC input? That's why I was trying to avoid using the AC in on the growatt.

Do you disagree?

is it the ES model or US model ?

if it is the ES model, please ignore my statement

 

[sunshine_eggo]

it's my own fault for not saying which model I had up front.

Most 120VAC battery chargers under 15A have alligator clips to be placed onto the battery terminals. In my case, should I clip those to the position and negative bus bars in my rack?

How to correctly hook up alligator clips to an in-rack busbar is probably my real question.

Alligator clips are a poor connection, and you'll get voltage drop. This will cause the peak voltage to be hit sooner and the current to taper faster resulting in a longer charge time, but you will get fully charged.

You may need to fabricate "charge leads" that come off the inverter main lugs, so you can clamp onto them. Those recessed terminals are tricky.

 

[jar349]

is it the ES model or US model ?

if it is the ES model, please ignore my statement

hahaha, this is the problem, right? It's the "US model" that is labelled as ES. I purchased it directly from SignatureSolar.

 

[jar349]

Alligator clips are a poor connection, and you'll get voltage drop.

Agreed, but that seems to be what chargers under 15A have, right? Do you know of any such 120VAC charger that doesn't have an alligator clip but something I could wire onto my battery bus bar?

 

[houseofancients]

hahaha, this is the problem, right? It's the "US model" that is labelled as ES. I purchased it directly from SignatureSolar.

than you should have the US model, which shoukd be able to connect to the grid.

i would make 100% sure though by calling signature solar and confirm with your serial, just to be in the clear.

it would save you buying extra chargers, cable and bring simplicity

 

[sunshine_eggo]

than you should have the US model, which shoukd be able to connect to the grid.

i would make 100% sure though by calling signature solar and confirm with your serial, just to be in the clear.

it would save you buying extra chargers, cable and bring simplicity

You've probably missed the boat on this one. SignatureSolar has been offering a EU spec inverter running at 240VAC/60Hz single phase coupled with an auto transformer to provide 120/240VAC split phase. There have been some threads on it in the last few months.

This is also how many Victron systems get installed in the U.S. - Get their bigger higher power units that are 230VAC/50Hz and run them at 240VAC/60Hz coupled with a Victron autotransformer for 120/240VAC split phase.

 

[jar349]

You've probably missed the boat on this one. SignatureSolar has been offering a EU spec inverter running at 240VAC/60Hz single phase coupled with an auto transformer to provide 120/240VAC split phase. There have been some threads on it in the last few months.

This is also how many Victron systems get installed in the U.S. - Get their bigger higher power units that are 230VAC/50Hz and run them at 240VAC/60Hz coupled with a Victron autotransformer for 120/240VAC split phase.

Yeah, I have the transformer too.

 

[offgriddave]

I have the EG4 "25A" charger it only makes 16A so I got another one from them and so I'm getting 32A
I run my generator every other day and it just works fine with alligator clip.

note you linked to the 5A version (the specs in the picture are wrong) so you are only going to get 48v * 5a = 250w. It will take 40 hours to charge your batteries.

the other one is 16A and will take 10200w / 800w = 12 hours to charge your batteries.

 

[jar349]

I have the EG4 "25A" charger it only makes 16A

Interesting. I have just a normal wall outlet available. It's got normal 12/2 going to a 20A circuit breaker. Nothing large is on that circuit. I wonder if it's a sneaky or stupid idea to attempt to make the "25A" work on that.... ?

 

[offgriddave]

its 16A rated at the charging output voltage (51v or "48v" but it goes to 57 I think). so 16*51=816 watts
pulling 800w out of your 120v outlet would only be 6.8 amps. if you have a 20A circuit breaker you could do a bunch of them

I am using two chargers so they are pulling 1600w

these chargers aren't "95%" efficient or whatever. That's also not true, however, I haven't checked but I bet they are 80 or 70%. Maybe not even that, why is there a huge heat sink? Anyway add 20-30% on top of what they are putting out to get the true amount but you aren't even near 2400w of the 20a breaker

I run my generator for two hours with two chargers every other day and its great!

 

[jar349]

its 16A rated at the charging output voltage (51v or "48v" but it goes to 57 I think). so 16*51=816 watts
pulling 800w out of your 120v outlet would only be 6.8 amps. if you have a 20A circuit breaker you could do a bunch of them

I am using two chargers so they are pulling 1600w

these chargers aren't "95%" efficient or whatever. That's also not true, however, I haven't checked but I bet they are 80 or 70%. Maybe not even that, why is there a huge heat sink? Anyway add 20-30% on top of what they are putting out to get the true amount but you aren't even near 2400w of the 20a breaker

I run my generator for two hours with two chargers every other day and its great!

Do you have your batteries in the rack? Would you be able to post a picture of how you hook the charger up to the batteries? Alligator clips onto the bus bars or something?

 

[offgriddave]

Do you have your batteries in the rack? Would you be able to post a picture of how you hook the charger up to the batteries? Alligator clips onto the bus bars or something?

no its just sitting on a shelf

there's .... alligator clips connected to the battery. the red alligator clip goes to red post(?) and the second charger red alligator clip goes to the other red post. Unsurprisingly, there's two black ones. They go to the other two posts... No picture needed but they do not look like alligators.

 

[jar349]

Yeah, the one-battery hookup is pretty obvious :D Alligators always look happy to me with their mouth open.

 

[Daddy Tanuki]

its 16A rated at the charging output voltage (51v or "48v" but it goes to 57 I think). so 16*51=816 watts
pulling 800w out of your 120v outlet would only be 6.8 amps. if you have a 20A circuit breaker you could do a bunch of them

I am using two chargers so they are pulling 1600w

these chargers aren't "95%" efficient or whatever. That's also not true, however, I haven't checked but I bet they are 80 or 70%. Maybe not even that, why is there a huge heat sink? Anyway add 20-30% on top of what they are putting out to get the true amount but you aren't even near 2400w of the 20a breaker

I run my generator for two hours with two chargers every other day and its great!

Dave, how long have you been using these, https://www.signaturesolar.com/products/48v-25a-120v-battery-charger-by-eg4
and how would you rate them value wise as a product?

I have been looking for a 48 volt charger that I could hard wire to my genset for cloudy/rainy weeks. My genset is 3-phase so whatever I end up with i wanted to get three of and wiring one to each phase to keep the genset's output balanced somewhat. from what the specs read on these things that should give me a range of 15-75 amps charging which for me means I could let the batteries run down to 20% and then charge them to 90%+ 6 hours of genset time.

currently I get about 3 days with zero solar input on my batteries depending on wife's whims. I am using a gasoline generator running split phase to put power to my inverter to charge but it takes forever if using any appreciable power in the house as we can only charge at about 30 amps while also powering the house. I would really rather get rid of the gasoline genset anyway as storing fuel for it is one more point on the checklist of maintenance in the good solar months. (the diesel genset powers my shop equipment so it is a daily use item, and besides that it take a long time for diesel fuel to go bad.

cheers