LifePO4 batteries for use with Midnite Classic 150?

[createthis]

I am not sure what is behind Midnite's recommendations, so I can't really comment on that. But part of the problem may be that the most common DIY use of Li batteries is the electric vehicle market and the second most common is for mobile power for boats, etc. Both of these have different use characteristics and different criteria for evaluation than the stationary PV market. As a result the charging and battery management needs will be different too.

For EVs, top balancing and using a BMS to cut off current for the whole string when one battery reaches its low voltage limit gives you the maximum total energy per charge for a single use, and therefore the best performance and range. For RE you should never need to discharge the battery below 20%, nor will you design to to charge above 80%.
And you are (hopefully) going to avoid multiple C discharges.

RE = Residential?

You're saying EV designs for max power output and residential designs for max longevity? That's weird though. If you cut off the bottom 20% and the top 20%, you're cutting off 40%. That's only 10% better than AGM's 50% DOD. I thought LFP usually could handle 80% DOD. Since this is a portable system, I have to wonder if I should design it more like an EV system. Maybe the additional cost of the BMS makes sense from a weight savings/power capacity perspective.

[inetdog]

It's strange that Midnite would recommend top balancing with a BMS while this forum recommends bottom balancing with no BMS. I understand the logic, I'm just not sure why Midnite is misinformed. It makes me think that not many people are running LFP. I know LFP is big in the boat scene though.

I am not sure what is behind Midnite's recommendations, so I can't really comment on that. But part of the problem may be that the most common DIY use of Li batteries is the electric vehicle market and the second most common is for mobile power for boats, etc. Both of these have different use characteristics and different criteria for evaluation than the stationary PV market. As a result the charging and battery management needs will be different too.

For EVs, top balancing and using a BMS to cut off current for the whole string when one battery reaches its low voltage limit gives you the maximum total energy per charge for a single use, and therefore the best performance and range. For RE you should never need to discharge the battery below 20%, nor will you design to to charge above 80%.
And you are (hopefully) going to avoid multiple C discharges.

[createthis]

Absolutely right, but please read everything first and do not cut corners on monitoring!
You can accumulate knowledge without doing, but you will not get all the benefits that come from experience.

You avoid mistakes through experience and you acquire experience by making mistakes. Just try to limit the consequences of those mistakes.er

Sigh. I'm here, aren't I? Research is my middle name.

[createthis]

If the BMS is designed to cut off charging at a reasonable maximum voltage, then you should not need to cut off the Classic.
More importantly, for maximum life of a typical Lithium battery you should not routinely charge and hold it at above about 80% SOC.
If you set the output voltages of the Classic to that voltage level AND turn off temperature compensation, you should be OK and not get near the overcharge point.
Sunking and others can tell you why most internal BMS systems are NOT appropriate for batteries in PV service and you are better off without them. Search the old posts for very good discussions. (Google search adding site:solarpaneltalk.com to your search string.

It's strange that Midnite would recommend top balancing with a BMS while this forum recommends bottom balancing with no BMS. I understand the logic, I'm just not sure why Midnite is misinformed. It makes me think that not many people are running LFP. I know LFP is big in the boat scene though.

[inetdog]

...
I'm not aware of any way to gain experience with LFP solar without actually doing LFP solar.

Absolutely right, but please read everything first and do not cut corners on monitoring!
You can accumulate knowledge without doing, but you will not get all the benefits that come from experience.

You avoid mistakes through experience and you acquire experience by making mistakes. Just try to limit the consequences of those mistakes.

[createthis]

Unless you have a lot of experience with LFP batteries, do not even try LFP. In addition to a good BMS you also need other equipment you do not have just to balance the batteries and maintain them properly. It takes a lot of know how and just one mistake will destroy LFP.

Thanks for the warning. I know it's a risk, but I'm not aware of any way to gain experience with LFP solar without actually doing LFP solar.

[Sunking]

Unless you have a lot of experience with LFP batteries, do not even try LFP. In addition to a good BMS you also need other equipment you do not have just to balance the batteries and maintain them properly. It takes a lot of know how and just one mistake will destroy LFP.

[inetdog]

If the BMS is designed to cut off charging at a reasonable maximum voltage, then you should not need to cut off the Classic.
More importantly, for maximum life of a typical Lithium battery you should not routinely charge and hold it at above about 80% SOC.
If you set the output voltages of the Classic to that voltage level AND turn off temperature compensation, you should be OK and not get near the overcharge point.
Sunking and others can tell you why most internal BMS systems are NOT appropriate for batteries in PV service and you are better off without them. Search the old posts for very good discussions. (Google search adding site:solarpaneltalk.com to your search string.

[createthis]

I own a midnite classic 150 and I'm interested in replacing the small test agm battery in my diy portable solar generator with a more useful 100ah lifepo4 battery.

I exchanged emails with the folks at midnite solar and they recommend using a LifePO4 battery with a BMS so the midnite classic can be shut off via AUX2 when the battery is fully charged.

This seems to mean I can't/shouldn't use batteries like the StarkPower UltraEnergy series: http://store.starkpower.com/12V-100A...tery_p_24.html because their BMS is internal and doesn't have any outputs.

I see a few other options, but I thought I'd ask around here. Is anyone here running LifePO4 with a Midnite Classic? Which battery are you using and how do you have it set up?

Thanks!