Charging External DIY Battery that charges Solar Generator

Daniel644

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So I had a thought, we all have seen the videos on Youtube of using a DIY battery or any other battery that is within the voltage range of the solar input on the Power Station to "expand" the capacity of the power station without having to buy a power stations over priced battery add-on and that got me wondering, can you use a dedicated Solar Charge Controller to charge the external battery while the external battery is still connected to the Power Station? None of the videos I've seen of people using the solar input on the Power Station as a way to feed in power from an external battery have discussed how to charge the external battery and I thought maybe using a solar charge controller that would allow you to hookup more panels since you are charging a larger external battery could be a way to keep the power station running 24/7 as long as the average power usage is below the charge rate of the solar input on the power station.
 
can you use a dedicated Solar Charge Controller to charge the external battery while the external battery is still connected to the Power Station?

Before I start, I should tell you I have no direct experience with this


But the answer should be YES - so long as the external battery peak voltage is below the max solar input of the power station


For example if you had a power station with a max solar input voltage of 50v , a 48v external battery would not be suitable as they charge at up to 58v max (over the 50v limit)

But if it's limit was 100v then there'd probably be no issues

So very much dependent on your equipment
 
Just to follow up, I have now been doing this for a few weeks, I have a Chinns "48v" 100ah battery that charges my Dabbsson DBS2300 and a PowMr 60 Amp Solar Charge controller (that has never put out more then 1.1 Kw with my current panel configuration running in a 3s2p configuration with 3 panels facing SE and 3 facing SW, using 300 watt panels and having lots of shading issues in the temporary location).
The Dabbsson is rated for 12-60v on the solar input and when charging from the battery pulls 430ish watts, if the charge controller is putting out more then 430 watts the excess beyond that goes into the battery, if the charge controller output drops below that it pulls the excess watts from the external battery.

Also to maximize my solar collection i'll unplug the battery from the Dabbsson in the morning and plug in another solar panel to that input (about to bump it to 2 panels when my parallel connectors arrive in the next day or 2) to effectively increase the number of panels I can temporarily deploy till I build my array.
 
Just to follow up, I have now been doing this for a few weeks, I have a Chinns "48v" 100ah battery that charges my Dabbsson DBS2300 and a PowMr 60 Amp Solar Charge controller (that has never put out more then 1.1 Kw with my current panel configuration running in a 3s2p configuration with 3 panels facing SE and 3 facing SW, using 300 watt panels and having lots of shading issues in the temporary location).
The Dabbsson is rated for 12-60v on the solar input and when charging from the battery pulls 430ish watts, if the charge controller is putting out more then 430 watts the excess beyond that goes into the battery, if the charge controller output drops below that it pulls the excess watts from the external battery.

Also to maximize my solar collection i'll unplug the battery from the Dabbsson in the morning and plug in another solar panel to that input (about to bump it to 2 panels when my parallel connectors arrive in the next day or 2) to effectively increase the number of panels I can temporarily deploy till I build my array.

I'm looking to maybe do something similar for my new Anker Solix F3800, which has a similar 12-60V solar input (1200W max). Can I ask a few questions about your setup and the PowMr charge controller?

1. Is it correct that when using the Chinns 48V battery on the PowMr, the load output side of the PowMr is putting out 48V and not 12V - so basically you're sending roughly 54V x 8A = 432 watts to the Dabbsson?
2. Does the Dabbsson have MPPT on its solar input? Would that cause any charging issues with the output from the Chinns/PowMr?
3. Since the Dabbsson is capable of drawing 600-800W from the DC input, does this cause any issues with the PowMr putting out only 432 watts? It won't overload or trip the PowMr 8A limit? (I'm concerned as my Solix F3800 is capable of drawing 25A at 48V, up to 1200W max, and wouldn't want to damage it or overload anything connected to the solar input.)
4. I saw there is a PowMr POW-M60-PRO and similar POW-M60-MAX, the former is limited the 8A load, the latter product page says 30A load max, but its manual for both say to put an 8A fuse inline. Do you think the 30A load stated on the -MAX version is a typo? I can't otherwise tell a difference between these two.

Thanks!

EDIT: I've done a bit more research to try to answer some of the basic questions above myself. I understand now that the load output side of these MPPT charge controllers is at the same voltage as the battery, i.e. 48V server rack battery = 48V load output. So I guess basically my question is, if the "load" on the charge controller is basically the DC input of a power station e.g. Dabbsson, Anker Solix, Delta Pro, which is basically a MPPT charge controller itself, will the power station try to draw the max amps it can from the charge controller, and possibly overload it? Or will the power station be limited in some way by the charge controller's max load rating?
 
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I'm looking to maybe do something similar for my new Anker Solix F3800, which has a similar 12-60V solar input (1200W max). Can I ask a few questions about your setup and the PowMr charge controller?

1. Is it correct that when using the Chinns 48V battery on the PowMr, the load output side of the PowMr is putting out 48V and not 12V - so basically you're sending roughly 54V x 8A = 432 watts to the Dabbsson?
2. Does the Dabbsson have MPPT on its solar input? Would that cause any charging issues with the output from the Chinns/PowMr?
3. Since the Dabbsson is capable of drawing 600-800W from the DC input, does this cause any issues with the PowMr putting out only 432 watts? It won't overload or trip the PowMr 8A limit? (I'm concerned as my Solix F3800 is capable of drawing 25A at 48V, up to 1200W max, and wouldn't want to damage it or overload anything connected to the solar input.)
4. I saw there is a PowMr POW-M60-PRO and similar POW-M60-MAX, the former is limited the 8A load, the latter product page says 30A load max, but its manual for both say to put an 8A fuse inline. Do you think the 30A load stated on the -MAX version is a typo? I can't otherwise tell a difference between these two.

Thanks!

EDIT: I've done a bit more research to try to answer some of the basic questions above myself. I understand now that the load output side of these MPPT charge controllers is at the same voltage as the battery, i.e. 48V server rack battery = 48V load output. So I guess basically my question is, if the "load" on the charge controller is basically the DC input of a power station e.g. Dabbsson, Anker Solix, Delta Pro, which is basically a MPPT charge controller itself, will the power station try to draw the max amps it can from the charge controller, and possibly overload it? Or will the power station be limited in some way by the charge controller's max load rating?

I'm NOT using the "Load" output on the PowMr SCC, the configuration is the PowMr is connected to the Chins battery and the solar panels are then connected to the PowMr, I then have another set of leads coming directly off the battery and going to the solar input connection on the Dabbsson, in the case of this unit it's designed to be able to charge off a cars cigarette lighter or solar panels using the same port and the way the tech support guy i've been talking to has explained it, basically the port can tell if their is the varying voltage you would get from solar panels or not and if it doesn't detect that then it defaults to "car charging" mode where it limits the current to 8 amps so as to not exceed the capacity of a cigarette lighter port in a car which is whats capping my charge rate.

from what I can see on the Solix F3800 website it's supposed to do 2400 watts of solar so you wouldn't really get any expanded panel capacity doing things this way, but i'm not sure what input connections are on the F3800 the website doesn't have any good pictures or specs on that other then that the solar input in an XT60 connection, could you list all the different input ports and specs on them that you have?
 
I'm NOT using the "Load" output on the PowMr SCC, the configuration is the PowMr is connected to the Chins battery and the solar panels are then connected to the PowMr, I then have another set of leads coming directly off the battery and going to the solar input connection on the Dabbsson, in the case of this unit it's designed to be able to charge off a cars cigarette lighter or solar panels using the same port and the way the tech support guy i've been talking to has explained it, basically the port can tell if their is the varying voltage you would get from solar panels or not and if it doesn't detect that then it defaults to "car charging" mode where it limits the current to 8 amps so as to not exceed the capacity of a cigarette lighter port in a car which is whats capping my charge rate.

from what I can see on the Solix F3800 website it's supposed to do 2400 watts of solar so you wouldn't really get any expanded panel capacity doing things this way, but i'm not sure what input connections are on the F3800 the website doesn't have any good pictures or specs on that other then that the solar input in an XT60 connection, could you list all the different input ports and specs on them that you have?

Thanks so very much for the reply and the clarification. So to backup a bit, yes, despite the impressive 2400W DC input spec, there are a bunch of concurrent limitations on the Solix F3800's DC inputs that may make it very challenging to max out the inputs. I'm looking at ways to overcome them in an easier, more flexible way. The limitations are:
- first, it's 2x XT-60 inputs, 1200W max each one (and no one has verified yet whether they have independent MPPT tracking algorithms or not, so maybe a secondary issue right now).
-60V max voltage - which makes is fairly impossible to put any modern (i.e. built within last 12 years) 200+W panels in series (Voc typically above 32V). You have to wire all of them in parallel, increasing amps and the wire gauge needed.
-25A max amps - So any panels <48 Vmp are never going to hit 1200W because of the 25A limitation, Closest is 48V x 25A in parallel. But if saying using 37 Voc panels, that are actually operating closer to Vmp of say 32W, we only get 32x25 = 800W max
-10A max limit at 10-32V input - so I guess every mfr has something akin to the cig lighter limitation, but at least now I know WHY Anker has the limit. In fact they are rewarding all the Kickstarter supporters a stretch goal of the 12V 10A cig lighter charging cable, which would take a laughably long time to fill the 3840Wh batter. So I guess every mfr has this feature/limitation in a different way. EcoFlow's approach is to require you to use XT-60i instead of XT-60, otherwise it assumes 10A limit. Dabbsson is saying if the DC source does not behave like a solar panel V x I curve, it will assume 8A cig lighter limit. And now I understand why Anker has this 10A limit - but we don't know exactly how they implemented it, whether it's strictly below 32V or algorithmically like the Dabbsson may be doing. But I do have a worry with panels with Voc in the 32-37V range (most 200-300W panels), that Vmp under real conditions might drop below 32V and then we're stuck with a 10A limit or 320W max, just like you're seeing with your Dabbsson.

So my main interest was in using an inexpensive SCC as a primitive buck converter, allows me to wire up 3-4 panels in series at a higher 100-150 Voc and lower 8-12 Isc (which allow drops my wire gauge and line losses over a 40 ft run), dropping it at the battery terminals to 51-55V and higher 20-25A for only the short run to the Solix. Possibly one of three ways:
-SCC battery terminals directly to the Solix F3800 DC input (no 48V battery). The SCC thinks it's charging or floating a 48V battery, but it doesn't actually limit the amp or watt outputs from the solar panels, does it? But will the Solix MPPT tracker get confused and start hunting, or drop into "cig lighter" mode?
-SCC battery terminals to 48V battery, 48V battery terminals to Solix F3800 DC input. I now understand this is what you're doing. But if I understand this, the SCC terminals are still basically directly connected to the Solix F3800 as in the first possibility. But the 48V battery can act as a buffer - if the Solix drops to "cig lighter" mode, or is impeded by the 25A limitation, excess solar can go into the 48V battery. Does the converse work as well? If the Solix likes the 48V and tries to draw 25A, will it first get whateve rsolar output from the SCC, and then any difference will come out of the 48V battery? If so, what happens when the 49V battery is depleted - does a server rack battery have self-protection to keep it from being fully discharged?
-SCC battery terminals to 48V battery, SCC load terminals to Solix F3800. This was my original thought. So isn't the intent of SCC having the load terminals, is that it does prevent the load from continuing to pull from the 48V battery once the 48V battery is depleted? And also has some convenient scheduling algorithms to choose WHEN the Solix F3800 would be able draw down the 48V battery.
But if many SCC's have an 8-10A limit on the load terminals, will the Solix F3800 trip the overload protection if it tries to draw 25A? Or does it just end up pulling the SCC load limit without causing any issues? If that new PowMr actually does have a 30A load limit, would the Solix F3800 be able to draw full 25A from combination of solar + 48V battery from the load terminals?

Do any of the three scenario risk any damage to the SCC, if the Solix F3800 tries to draw 25A, but the panels and/or 48V battery can't supply that much?
 
@wwu123 As a general rule, the amount of amps is determined by the device "pulling" the power, so in your case the Solix F3800, if the Solix can pull up to 25 amps and you connect it to the LOAD on an SCC that has a lower LOAD amp rating you will damage the SCC (this is specifically stated in the manual). You HAVE to use an external battery no matter what because the SCC is powered from the battery (and in the case of the PowMr that can operate at several different voltages, the voltage used is determined by the battery voltage, which also effects the maximum solar input capability of the PowMr), if you tried connecting the SCC directly to the Solix with no battery you won't get voltage out of the INPUT on your Solix (or at least I don't see any voltage when I put a multi meter to the solar input port on my Dabbsson, with nothing connected to the port, I just checked to confirm) so you'll have nothing powering the SCC (and the SCC needs to be connected to battery power before connecting solar panels to it, per the manual), Remember what you are basically doing is using a charger to power a charger with the battery setting the voltage and allowing a steady supply to run into your Solix all night long (depending on the size of the battery), the only way it will function is the way I am setup, of your other 2 methods one will damage the SCC and the other flat out won't work (per the setup manual of the SCC).

As for your undervoltage concern, that depends on your battery, you have to check every safety feature of the BMS in the battery, key ones being UnderVoltage Protection and OverVoltage Protection, these allow the BMS in the battery to control when it cuts discharging and charging so as to not over discharge or over charge the battery cells, so you don't need to concern yourself with the SCC Load as a under voltage cutoff unless your battery lacks under voltage cutoff protection.

As a note, I am experiencing 1 issue on my end with this setup, I discovered it yesterday and confirmed it again today, with everything connected, once the external battery reaches OverVoltage Cutoff and stops charging (with more then enough solar available, like today it was doing around 1.8Kw when the battery hit the cutoff) the wattage the Dabbsson will pull drops signifigantly, instead of charging at 430ish watts (or whatever rate it pulls external battery power to maintain a fully charged internal battery) it drops to like 50-70 watts, this is often below my actual usage so i'll start losing battery percentage in the Dabbsson as it can't keep the unit recharged at this low wattage, I even tried firing up one of my desktops and doing some crypto mining to drain the battery in the Dabbsson just to confirm it wasn't just because the Dabbsson battery was charged up, the only way to get back to the 430ish watts is to wait for the solar panels to stop putting out power then disconnect the XT60 from the battery to the Dabbsson, wait for the relay in the Dabbsson to click (there is an audible click a few seconds after connecting or disconnecting anything, panels or battery, plugged into the XT60 port) and plug it back in, something about when the battery hits that Overvoltage cutoff it puts the SCC voltage to 58v and I guess the Dabbsson doesn't like that voltage (even though it's in spec), your mileage may vary on the Solix if it would act the same, really it's just got me wanting a much bigger battery, I go through a little over half the battery each day in my current use case, so i'm good for about a day and a half without sunshine, but around here when it gets rainy or cloudy it does that for several days straight, so i'd like a battery that can handle several days of load as that would ultimately reduce the frequency of having to disconnect and reconnect the XT60 each day (hell I might put a breaker or switch in the line to make it easier then unplugging).
 
I'm in a similar boat with how I designed my system.
My EcoFlow Delta Mini has a maximum input of 300W.

That's why I chose a battery bank voltage of 36v.
(30v input x the pitifully low 10A max input= 300W)

My current battery system was originally intended only to be a DIY external battery for the EcoFlow, but now it has its own inverter and charge controller lol

Now I am thinking of getting myself a Bluetti AC200Max or similar unit because they have a 900W input limit and I could much better use my battery backup system that way.

My battery bank is about 5kWh.
36v 15.3Ah x10
 
I started with an Ecoflow River 2 Pro and then almost immediately a Delta pro which I used for a couple of months and got all set up via a transfer switch and a couple of 550 W panels then realizing the limitations went to a Sungold 10K48 and 5 rackmount batteries via the same transfer switch/plug powering 6 circuits of my house.
 
@wwu123 As a general rule, the amount of amps is determined by the device "pulling" the power, so in your case the Solix F3800, if the Solix can pull up to 25 amps and you connect it to the LOAD on an SCC that has a lower LOAD amp rating you will damage the SCC (this is specifically stated in the manual). You HAVE to use an external battery no matter what because the SCC is powered from the battery (and in the case of the PowMr that can operate at several different voltages, the voltage used is determined by the battery voltage, which also effects the maximum solar input capability of the PowMr), if you tried connecting the SCC directly to the Solix with no battery you won't get voltage out of the INPUT on your Solix (or at least I don't see any voltage when I put a multi meter to the solar input port on my Dabbsson, with nothing connected to the port, I just checked to confirm) so you'll have nothing powering the SCC (and the SCC needs to be connected to battery power before connecting solar panels to it, per the manual), Remember what you are basically doing is using a charger to power a charger with the battery setting the voltage and allowing a steady supply to run into your Solix all night long (depending on the size of the battery), the only way it will function is the way I am setup, of your other 2 methods one will damage the SCC and the other flat out won't work (per the setup manual of the SCC).

As for your undervoltage concern, that depends on your battery, you have to check every safety feature of the BMS in the battery, key ones being UnderVoltage Protection and OverVoltage Protection, these allow the BMS in the battery to control when it cuts discharging and charging so as to not over discharge or over charge the battery cells, so you don't need to concern yourself with the SCC Load as a under voltage cutoff unless your battery lacks under voltage cutoff protection.

As a note, I am experiencing 1 issue on my end with this setup, I discovered it yesterday and confirmed it again today, with everything connected, once the external battery reaches OverVoltage Cutoff and stops charging (with more then enough solar available, like today it was doing around 1.8Kw when the battery hit the cutoff) the wattage the Dabbsson will pull drops signifigantly, instead of charging at 430ish watts (or whatever rate it pulls external battery power to maintain a fully charged internal battery) it drops to like 50-70 watts, this is often below my actual usage so i'll start losing battery percentage in the Dabbsson as it can't keep the unit recharged at this low wattage, I even tried firing up one of my desktops and doing some crypto mining to drain the battery in the Dabbsson just to confirm it wasn't just because the Dabbsson battery was charged up, the only way to get back to the 430ish watts is to wait for the solar panels to stop putting out power then disconnect the XT60 from the battery to the Dabbsson, wait for the relay in the Dabbsson to click (there is an audible click a few seconds after connecting or disconnecting anything, panels or battery, plugged into the XT60 port) and plug it back in, something about when the battery hits that Overvoltage cutoff it puts the SCC voltage to 58v and I guess the Dabbsson doesn't like that voltage (even though it's in spec), your mileage may vary on the Solix if it would act the same, really it's just got me wanting a much bigger battery, I go through a little over half the battery each day in my current use case, so i'm good for about a day and a half without sunshine, but around here when it gets rainy or cloudy it does that for several days straight, so i'd like a battery that can handle several days of load as that would ultimately reduce the frequency of having to disconnect and reconnect the XT60 each day (hell I might put a breaker or switch in the line to make it easier then unplugging).
Thanks so much for this information - it gives a lot clearer understanding of how the SCC works, and that the behavior of XT-60 inputs in various battery station brands might have unexpected behaviors, even if everything looks within spec.

The Solix F3800 is brand-new, just started shipping a month ago, so among a handful of active owners, no one's yet tried a 48V external battery with SCC yet - will have to do some experimenting. I know folks have tried Chargeverters and SMPS at 60V with at least 25A supply, and the Solix F3800 was fine reaching close to 20A (approaching the 1200W limit), but the 58V with Battery Overvoltage/SCC could maybe still cause some unexpected behaviors.
 
I've been trying to get a 36V battery to work with the two mppt ports on my Delta 2 max with no success as a poor mans cheap extension battery. It may initially show the full 499W solar input which I would expect as limit is 500W per port and specs are 11-60V 15A. But then that quickly ends and the d2m sits there showing zero solar input. So I'm wondering if it's too much for it to handle. Now if I plug in a 12V battery it will happily charge away at 110W input and dropping as voltage of the 12V battery drops. Tomorrow will try a 24V battery config.

Anyway definitely a setback may have to go for a multiplus 2 or something like that.20240208_094452.jpg
20240208_133313.jpg
 
so i'd like a battery that can handle several days of load as that would ultimately reduce the frequency of having to disconnect and reconnect the XT60 each day (hell I might put a breaker or switch in the line to make it easier then unplugging).
I put one of these between my panels and the d2m today so I could disconnect without hot plugging the xt60i connectors. 32A rating combined for both strings so need to be aware but for Delta level stuff with 2*15A inputs. should be fine.20240208_133333.jpg
 
It's a shame that the Delta 2 Max has issues accepting a battery input. 😞

That was actually my next upgrade path after this Delta Mini that I have.
That chugs along no problem with my 36V battery system charging it up at its maximum of 300W.



Let us know if you have any luck getting it figured out.
 
It's a shame that the Delta 2 Max has issues accepting a battery input. 😞

That was actually my next upgrade path after this Delta Mini that I have.
That chugs along no problem with my 36V battery system charging it up at its maximum of 300W.



Let us know if you have any luck getting it figured out.
So I don't see a way around it. If it's having problems at 36V seems inevitable it would also have issues at 48V. Interesting that you don't have any issues with your delta mini and 36V

Thinking about getting a Victron Phoenix 48/1200 inverter and running it off four of the minis in series for 48V, and then using the d2ms AC input. Set the d2m charge rate for 800W or less or so hopefully the 48/1200 doesn't get noisy. Advantage there is I get pass through capability in the d2m. Plus I don't have to manually switch the mppts from solar to external battery, can use the mppt ports for their 1kW input during the day. Downside is an extra DC/AC/DC conversion, and $334 of additional spend on the 48/1200
 
So I don't see a way around it. If it's having problems at 36V seems inevitable it would also have issues at 48V. Interesting that you don't have any issues with your delta mini and 36V

Thinking about getting a Victron Phoenix 48/1200 inverter and running it off four of the minis in series for 48V, and then using the d2ms AC input. Set the d2m charge rate for 800W or less or so hopefully the 48/1200 doesn't get noisy. Advantage there is I get pass through capability in the d2m. Plus I don't have to manually switch the mppts from solar to external battery, can use the mppt ports for their 1kW input during the day. Downside is an extra DC/AC/DC conversion, and $334 of additional spend on the 48/1200
Yeah that's a hell of a project to achieve what you're doing.
 
Ok good news, Delta 2 max working just fine with two xt60i connectors both connected to a 24V battery (two 12V minis in series). 36V was always going to be a problem, and I don't need the 1000W charge rate, 700+ is fine.

Screenshot_20240211_132911.jpg
 
I'm glad it's working for you, I'm still just very curious as to why it seems to be fine with a constant 24V and not 36V or higher.
That's awesome that you got it working though.

I still may consider getting a Delta 2 Max even with that shortcoming.
It's a great unit.
 
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I'm glad it's working for you, I'm still just very curious as to why it seems to be fine with a constant 24V and not 36V or higher.
That's awesome that you got it working though.

I still may consider getting a Delta 2 Max even with that shortcoming.
It's a great unit.
Yup can definitely recommend the d2m, completely replaced my Honda eu2200 gas generator for anything less than 2kWh worth of work.

Seeing how many loads of laundry I can run on it today to figure out washer and dryer (propane) consumption.

20240212_123004.jpg
 
Used 13% for a regular load in washer. Unfortunately dryer was a no go was surging over 2600W at startup and d2m turned off AC due to overload. The washer is inverter driven so a much more gentle load, didn't exceed 500W max during the cycle.
Screenshot_20240212_135153.jpg
 
Used 13% for a regular load in washer. Unfortunately dryer was a no go was surging over 2600W at startup and d2m turned off AC due to overload. The washer is inverter driven so a much more gentle load, didn't exceed 500W max during the cycle.
View attachment 195052
Have you tried turning on that X boost option or whatever it it's called?
Maybe it would lessen how much that surge drew from the unit?


That's pretty sweet that it only comes down 13% too.
Nice to know you can wash some laundry off a power station. Definitely wouldn't be too difficult to set up a drying rack for off-grid or "out of power" situations either.
 
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