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Poor performance - Off grid All-in-one

PatD

New Member
Joined
Oct 8, 2021
Messages
18
Location
West Kootenay, British Columbia
I have an off grid system That is not performing well at all.
Battery seems to charge but takes a significant time to replenish.
I have limited the load on the inverter to a single refrigerator with no other loads.
MPP unit seems to draw a significant amount of power in no/small load situations (ie. just to power MPP unit cooling fans.)
I configured the solar panels in 2 parallel strings of 2 to accommodate the MPP max VOC and to try and address possibility of shading.
I do have a small 30AMP 2400W generator to provide supplemental battery charging through the MPP All-in-1.

I do want to run either a DC fridge or a small AC fridge as the central reason for solar. Lights and Starlink are only other power draws.

Thoughts I have had.
Replace MPP All-in-1 with an efficient MPPT controller (Victron or similar) and separate inverter-charger.
Add more battery storage (maybe rackmount?). Not sure my home built cell system is performing.
Add additional solar panels (ie. purchase 2 more of same panels and make 2 P strings of 3S panels to keep Voc under 150V. I do have to contend with trees as the location is lakeside but with tall trees at shoreline which limits my direct sunlight to 11AM- sunset.

I am sure throwing money at this would help but want to take technically sound steps forward. Not sure where to start to understand why or where to start when focusing on a remedy. Any help would be gratefully received.

Config.
West Kootenay, British Columbia
Current Solar Power System MPP Solar LV3KVA-24V (110Vac 2400w 24V Solar Power inverter 80a MPPT solar charger 60a battery charger, Max PVoc 145V)
16 LiFePO4 (Bosan-NEW) cells is 8S2P config. (8 serial groups of 2 cells in parrallel) 8S BMS - Overkill with Bluetooth
4 - 435W Solar panels in 2S2P config (Quantum Q.PEAK DUO L-G8 425) Voc At Normal Operating Condition 46.29V
 
OP, are you complaining of charge time duration, battery capacity, etc.....? What is your main complaint?

Do you have any data on collected kwh's or do you see whats going into or out of the batts?

Can you see your charge controllers solar power or charge current live?
johnny5.jpeg
 
16 LiFePO4 (Bosan-NEW) cells is 8S2P
What the Ah? Or total capacity of the battery?

I have similar set up (24v 3KVA Inverter (MPP clone) + 4x 400w panels) and those days, my 3 kWh battery is full before 11am on a sunny day.
Still, each morning the idle consumption of the inverter had drain a part of my battery.
 
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A different inverter, that is slightly more efficient, won't help much.
A couple of more panels and maybe some additional storage seems cheaper and more cost efficient to me.
 
I have an off grid system That is not performing well at all.
Battery seems to charge but takes a significant time to replenish.
I have limited the load on the inverter to a single refrigerator with no other loads.
MPP unit seems to draw a significant amount of power in no/small load situations (ie. just to power MPP unit cooling fans.)
I configured the solar panels in 2 parallel strings of 2 to accommodate the MPP max VOC and to try and address possibility of shading.
I do have a small 30AMP 2400W generator to provide supplemental battery charging through the MPP All-in-1.

I do want to run either a DC fridge or a small AC fridge as the central reason for solar. Lights and Starlink are only other power draws.

Thoughts I have had.
Replace MPP All-in-1 with an efficient MPPT controller (Victron or similar) and separate inverter-charger.
Add more battery storage (maybe rackmount?). Not sure my home built cell system is performing.
Add additional solar panels (ie. purchase 2 more of same panels and make 2 P strings of 3S panels to keep Voc under 150V. I do have to contend with trees as the location is lakeside but with tall trees at shoreline which limits my direct sunlight to 11AM- sunset.

I am sure throwing money at this would help but want to take technically sound steps forward. Not sure where to start to understand why or where to start when focusing on a remedy. Any help would be gratefully received.

Config.
West Kootenay, British Columbia
Current Solar Power System MPP Solar LV3KVA-24V (110Vac 2400w 24V Solar Power inverter 80a MPPT solar charger 60a battery charger, Max PVoc 145V)

Probably 50W to 100W at idle to run inverter?

16 LiFePO4 (Bosan-NEW) cells is 8S2P config. (8 serial groups of 2 cells in parrallel) 8S BMS - Overkill with Bluetooth

280Ah cells? If so 13.4Kwh of which 12 Kwh are usable.

4 - 435W Solar panels in 2S2P config (Quantum Q.PEAK DUO L-G8 425) Voc At Normal Operating Condition 46.29V
8.7KWh after 5 hours of full output. Any output outside the 5 hour window is just a bonus in most cases.

75W for inverter x 24 hours=1.8Kwh 8.7-1.8= 6.9Kwh left

If you run the battery down to 10% SOC, that will take 2 days to recharge your battery. If you run down to 55% SOC, it takes a full day's production. This is with no loads on the system while it is charging.

Your problem is not enough PV. Combined with the shading, you won't have much yield. The MPP is capable of 1900W of charging power. However your panels are mismatched to the MPPT, 3S would probably put your over on VOC on a cold day.

My suggestion is to add another SCC with it's own set of PV. You can add as many SCC's as you want to charge the battery, it won't affect the other SCC's.
 
Going by location you're going to need a LOT more panels. The weather up there sucks. If you can't get more panels on the AIO, and that voltage is right there on the raggedy edge, then as mentioned you can throw more panels on another SCC and strap it to the same battery bank to help the AIO catch up.
 
OP, are you complaining of charge time duration, battery capacity, etc.....? What is your main complaint?

Do you have any data on collected kwh's or do you see whats going into or out of the batts?

Can you see your charge controllers solar power or charge current live?
View attachment 145728
Probably 50W to 100W at idle to run inverter?



280Ah cells? If so 13.4Kwh of which 12 Kwh are usable.


8.7KWh after 5 hours of full output. Any output outside the 5 hour window is just a bonus in most cases.

75W for inverter x 24 hours=1.8Kwh 8.7-1.8= 6.9Kwh left

If you run the battery down to 10% SOC, that will take 2 days to recharge your battery. If you run down to 55% SOC, it takes a full day's production. This is with no loads on the system while it is charging.

Your problem is not enough PV. Combined with the shading, you won't have much yield. The MPP is capable of 1900W of charging power. However your panels are mismatched to the MPPT, 3S would probably put your over on VOC on a cold day.

My suggestion is to add another SCC with it's own set of PV. You can add as many SCC's as you want to charge the battery, it won't affect the other SCC's.
You are correct, the Bosan cells are 280 Ah capacity. I was curious to know if re configuring my cells into 2 - 12V batteries in series would be a better config that the config I used?
Your calculations of recharge time is accurate based on my experience. - 90% 2 days and 1 day at 55%. We have used the genny to reduce these times.
It is a very remote location and my goal is to have a system that can reliably provide power for a couple days and be able to recharge in a day (if I can afford the upgrades).

You mentioned the miss-match of panels to SCC. The BMS is set to not charge below 35 degrees. (low temp cutoff).

If I was to add a separate SCC with panels should I use the same solar panel models or would you recommend a different panel capacity? I have also noodled with the idea of replacing the MPP with a SCC-Inverter that would be better suited for my needs. Any recommendation for the SCC and panels would be welcome!
 
Going by location you're going to need a LOT more panels. The weather up there sucks. If you can't get more panels on the AIO, and that voltage is right there on the raggedy edge, then as mentioned you can throw more panels on another SCC and strap it to the same battery bank to help the AIO catch up.
Thanks for this, The consensus seems to be a second separate SCC with more panels. Should I stay with the Qcell panel models and match a SCC to the additional ones? Any specific recommendations would be welcomed.
 
Bosan cells are 280 Ah capacity... my goal ... be able to recharge in a day
Ok! With 14 kWh battery pack you will need to double your PV array (let say 8x 435W panel) to have your battery charged inside one sunny day.
 
I was curious to know if re configuring my cells into 2 - 12V batteries in series would be a better config that the config I used?
Just remember that the two separate 12v batts in series would need to have a separate balancer on top of the BMSs to keep the packs equal. You would be better off with a 24v pack and ONE BMS. People run unsynced batts in series but there can be problems.
 
I would actually recommend two 8s batteries with their own BMS, in parallel. The system will be better balanced and you will have redundancy. If one fails, you can run without it until repaired.
 
You are correct, the Bosan cells are 280 Ah capacity. I was curious to know if re configuring my cells into 2 - 12V batteries in series would be a better config that the config I used?

Keyword- Watts. It doesn't matter if batteries are in series or as one 24V pack.
Your calculations of recharge time is accurate based on my experience. - 90% 2 days and 1 day at 55%. We have used the genny to reduce these times.
It is a very remote location and my goal is to have a system that can reliably provide power for a couple days and be able to recharge in a day (if I can afford the upgrades).

You mentioned the miss-match of panels to SCC. The BMS is set to not charge below 35 degrees. (low temp cutoff).

Nothing to do with low temp cutoff. Your panels don't maximize the available capability of the PV. You can't use a 3S2P configuration without going over VOC on a cold day. With different panels where you could use 3S combined with parallel strings to maximize PV input close to the rating of the SCC, you might be OK without adding another SCC.


If I was to add a separate SCC with panels should I use the same solar panel models or would you recommend a different panel capacity?

Look for higher VOC rating SCC's, then find panels that when combined in series will hit close to the rated VOC of the charge controller. Most SCC's are limited on amperage (but you can parallel strings with smaller wattage panels) and the key to taking full capacity of a SCC is by panels in series close to the VOC rating.


You have to run the numbers thru a calculator for max VOC like the Midnite calculator, and compare to the VOC of the SCC. Then determine if you are close to the max wattage rating of the SCC. This is the most efficient use of panels and the SCC. Less voltage drop, less power loss and less equipment needed if done correctly.

I have also noodled with the idea of replacing the MPP with a SCC-Inverter that would be better suited for my needs. Any recommendation for the SCC and panels would be welcome!
Keep the current AIO inverter, use the SCC in it and just add a separate SCC with some more panels. Less expense and you have greater capability and yield.
 
To summarize, the replies I have received (thanks everyone for the thoughts and questions!)
-Keep AIO.
-Add a separate SCC with matched additional panels to optimize the max Voc of the SCC to improve charge efficiency / reduce charge time of existing battery.
-I did not hear that I should necessarily add more of the same solar panels, but it would be OK if the SCC was appropriately matched.
-If I was to alter the battery cells to create 2 - 24V in parallel, I should make sure each would have an 8s BMS.
-Future: increase battery storage.

Along these lines a thought I had was to purchase a higher Voc capacity MPPT SCC such as Midnite Classic 200SL (other?) that would allow me to string the existing 4 Qcell's together in Series? and purchase a more compatible set of panels for the AIO? Would this be a reasonable approach?
 
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To summarize, the replies I have received (thanks everyone for the thoughts and questions!)
-Keep AIO.
-Add a separate SCC with matched additional panels to optimize the max Voc of the SCC to improve charge efficiency / reduce charge time of existing battery.
-I did not hear that I should necessarily add more of the same solar panels, but it would be OK if the SCC was appropriately matched.

Only thing that matters is the output voltage. You can add 10 panels in series at 400VOC PV input and it won't matter.

-If I was to alter the battery cells to create 2 - 24V in parallel, I should make sure each would have an 8s BMS.

Yes, my preference is to run batteries in parallel and not cells in parallel. One BMS cuts off due to high or low voltage, the second BMS will allow some operation. Doesn't apply to overload though.

-Future: increase battery storage.

Along these lines a thought I had was to purchase a higher Voc capacity MPPT SCC such as Midnite Classic 200SL (other?) that would allow me to string the existing 4 Qcell's together in Series? and purchase a more compatible set of panels for the AIO? Would this be a reasonable approach?
Either way will work. It depends on what you can get for panels. Some might be less than ideal to fit a certain SCC but if the price is right, why not?

I like SCC's in the 400V operating range simply because the larger panels seem to run around 50VOC. 8S gives around 400V and stays under a 500V VOC limit when it gets cold out. Take a panel around 500W with 50VOC. 8S gives 4000W of PV at 400V, 10 amps.
 
Sounds like the cheapest would be to just drop the trees and let the panels do their thing ?

Then buy more equipment.
 
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