Sunny Island SI-6048 BMS communication

[1201]

D*mn!

I thought I had a line on 2x Sunny Islands and 2x Midnight Classics for cheap.

The universe is telling you you have enough already

 

[Trukinbear]

Wow! I wish I'd have gone LiFePo4 years ago - I thought I couldn't afford it. I was wrong because now I see that 50,ish % of my power went to heating up battery acid - I don't appear to actually use nearly as much power as I thought. Wow!

 

[Hedges]

LiFePO4 became highly competitive over the past few years.
Several years ago, lead-acid price was more competitive.

For capacity to handle 3 days without sun, the difference in lifespan may be nil (vs. a system cycled 100% every night.)
Murdered forklift batteries negating that. LiFePO4 can be murdered too, but BMS supposed to prevent that. If FLA was invented today it might get similar protection, but dates from where that was a human job.

 

[Trukinbear]

LiFePO4 became highly competitive over the past few years.
Several years ago, lead-acid price was more competitive.

For capacity to handle 3 days without sun, the difference in lifespan may be nil (vs. a system cycled 100% every night.)
Murdered forklift batteries negating that. LiFePO4 can be murdered too, but BMS supposed to prevent that. If FLA was invented today it might get similar protection, but dates from where that was a human job.

Looking back at my records that brand new picked up at the manufacturer forklift battery appears to have eaten over half my power from day one.

 

[Trukinbear]

Putting the batteries in over a couple of months to spread the costs out - I thought I needed 600ah minimum, but what I'm seeing with the first 200Ah makes me believe that all my calculations based on my FLA system are WAY off, and 400Ah might be plenty

 

[Trukinbear]

Cloudy and rainy today. Very overcast. Normally I'd be making only about 50% of the power I need, but I'm actually making about 20% more than I need

 

[kommando]

I went from a 17kwh gel battery to 14kwh LFP, the LFP gives me double the performance of the gel despite the lower number of kwh. Another 15kwh LFP on route.

 

[Hedges]

I understood FLA consumes 1/3 of the power delivered, you get back 2/3. Put another way, what it consumes is 1/2 of what you get back from it.
Only from reading, I've never lived with FLA beyond small size.

I do use AGM, and I'm not logging its performance. Way over-paneled and grid-backup so most of their life spent basking in Float.

You probably have efficient off-grid house. I simply installed excess PV, back when I thought rebates made it a good deal. Was break-even with utility at best over 17 years. Today, PV + LiFePO4 is much cheaper (but if using lead-acid, lower cycle life may make cost same as grid.)

 

[Trukinbear]

I understood FLA consumes 1/3 of the power delivered, you get back 2/3. Put another way, what it consumes is 1/2 of what you get back from it.
Only from reading, I've never lived with FLA beyond small size.

I do use AGM, and I'm not logging its performance. Way over-paneled and grid-backup so most of their life spent basking in Float.

You probably have efficient off-grid house. I simply installed excess PV, back when I thought rebates made it a good deal. Was break-even with utility at best over 17 years. Today, PV + LiFePO4 is much cheaper (but if using lead-acid, lower cycle life may make cost same as grid.)

We're pretty efficient, I designed this place knowing id likely remain off the grid, plus our climate is very mild. That 2200# forklift battery, who knows how many gallons (barrels) of battery acid I had to heat and keep warm. It was in the back of my mind, yes but in more of an anecdotal way, now looking empirically it's simply staggering. My original calculations weren't off, I just didn't adjust for 50% battery efficiency

 

[Hedges]

Only takes energy to heat, not to keep warm. As you discovered when you insulated it. Maybe needed insulated enclosure and thermostatic vent.

Apparently insulation works for LiFePO4, just need a bit of electric heat, so even simpler.
I would consider if starting from scratch, but maybe only top name BMS like REC would be reliable? Even then, issues configuring.
I have strings of AGM for all.

 

[Trukinbear]

Only takes energy to heat, not to keep warm. As you discovered when you insulated it. Maybe needed insulated enclosure and thermostatic vent.

Apparently insulation works for LiFePO4, just need a bit of electric heat, so even simpler.
I would consider if starting from scratch, but maybe only top name BMS like REC would be reliable? Even then, issues configuring.
I have strings of AGM for all.

D*mn!

I thought I had a line on 2x Sunny Islands and 2x Midnight Classics for cheap.

Victory! The (2)BMS, the SI6048, and the Whizbang Jr are showing SOC within 3% of one another

 

[Trukinbear]

Victory! The (2)BMS, the SI6048, and the Whizbang Jr are showing SOC within 3% of one another

Of course, I'll probably have to start over with this every time I add another 200 amp hours of battery, which should be two more times this summer