MPP LVX 6048 and Battle Born Batteries -- new system set-up issues

[Glencanaan]

I have had a solar electric system for over 20 years, but for the last few years I have been planning for and implementing a much-needed upgrade. I have been working to install an MPP LVX 6048 and Battle Born 12v 100Ah batteries. After purchasing all of this, I am being told of requirements that I wasn't aware of. First it was the minimum voltage from the PV array. I knew there was a max voltage, but didn't know the minimum. I added panels and rewired the array to get it over the 160v I was told was the minimum. With that done successfully, I started installing the rest of the system. I am now being told that the battery back has to be at least 300Ah and 400 recommended. Otherwise, the batteries cannot charge the capacitors in the inverter. With four 12v/100Ah batteries in series, I have the 48 volts I need but only 100Ah.
I have looked and looked and I cannot find anywhere that these requirements are documented, other than the emails from the place I bought the inverter.
Is this correct? If so, I guess I either need to buy a different inverter, add substantially to my investment in batteries, or buy different batteries altogether.
Thoughts and suggestions appreciated.

 

[BentleyJ]

100Ah is a mismatch for a 6048 but it can work if you understand the limitations of the battery and how to derate the system accordingly.
The information you received is correct but not explained well at all.
1) The capacitor issue is very easily solved by using a precharge resistor to limit initial inrush current from the batteries to the capacitors which are at 0 volts to start. A discharged capacitor acts like a short circuit at the moment voltage is applied. As it charges the current drops to zero as they reach the same voltage as the source. There are plenty of forum posts and YT videos about this issue, no need to repeat here.
2) With only 100Ah you will need to limit the loads on the inverter so the BMS doesn't trip on Over Current Protection. Not sure what it is for the Battle Born but lets assume its 1C or 100Amps. That limits the load you can put on the inverter to about 4,300Watts.
3) Likewise the charging current should be set on the inverter so it is limited to about 25A which is 0.25C. This is a standard specification for LFP batteries.
4) Battle Born is probably not the best choice for a 48V system. I would recommend getting another 100Ah battery to at least double the capacity. This would be much more reasonable for the 6048. It is not necessary to use the same brand of battery when paralleling. Any LiFePO4 battery would work and it doesn't even have to be the same capacity. Take a look at EG4, SOK or Orient Power batteries for example. There are several choices either rack mount or wall mount.
5) With more battery capacity the full capability of the inverter can be used.

 

[Glencanaan]

All of this information is in the manual, again I'm going to start a forum titled RTFM ?

I just re-read the manual. On page 5 it talks about battery connection. Nothing about minimum Ah.
On page 7 it talks about PV connection. It talks about maximum but not minimum voltage.
On page 27 are the specifications. Under PV input it lists many maximums, no minimums. Under battery and charger, nothing about minimum amp hours.
Could you please do me the favor of letting me know where in the manual I missed these details?
Thanks

 

[42OhmsPA]

I just re-read the manual. On page 5 it talks about battery connection. Nothing about minimum Ah.
On page 7 it talks about PV connection. It talks about maximum but not minimum voltage.
On page 27 are the specifications. Under PV input it lists many maximums, no minimums. Under battery and charger, nothing about minimum amp hours.
Could you please do me the favor of letting me know where in the manual I missed these details?
Thanks

Page 7 of my TP6048 shows 120v min for mppt, page 5 recommends 200ah battery.

 

[Supervstech]

Really this is all about runtimes, and desired loading.
What capacity will you be using the inverter for?

As stated, a 100Ah will have 5280Wh of capacity, so it won't power the inverter for long at full load, and the demand is going to tax it.
Also 100Ah isn't going to survive long with the standby draw of the inverter alone...

You purchased an inverter capable of 6000W output... simple math shows to power that draw for long needs that Wh battery capacity for each hour of runtime you desire... were you planning to use the inverter for under an hour a day?

Everything I have read about mppt says the pv input needs to be over the battery voltage to charge. 130 seems an odd requirement, but some are setup to 1/2 or 1/3 the pv voltage for charging, so having higher voltage would be needed.

 

[timselectric]

If you do end up replacing the batteries.
Do it right and get 48v batteries. You'll save yourself a bit of headache, down the road. Putting batteries with BMS's in series adds maintenance to an otherwise maintenance free battery bank.

 

[Kornbread]

Don't think you'll have any issue with charging the caps on the inverter, with lead acid batteries. That's generally an issue with Lithium and bms's, especially the LiFePower4, but as previously mentioned, your runtime and output will be severely limited. If your inverter draws 100w at idle, it's going to have eaten through most of the batter power by morning, sans any other load. And yes, it would be best to limit charge current.

Oh, and as far as manuals go ... welcome to Voltronic Power LLC and their severely lacking, almost negligent, manuals.