Question about specs for DIY build

[Andrewr05]

BMS aren't terribly accurate, especially for low currents < 2A.

Is this why every power station I've owned (Multiple Jackerys, EcoFlows and Bluettis) has been awful at showing small loads?
AC or DC they often wouldn't register anything was even being pulled until like 15w or so, which would require me to plug in multiple other devices just to get it to appear.

 

[sunshine_eggo]

Is this why every power station I've owned (Multiple Jackerys, EcoFlows and Bluettis) has been awful at showing small loads?
AC or DC they often wouldn't register anything was even being pulled until like 15w or so, which would require me to plug in multiple other devices just to get it to appear.

That's a factor, but it's not just that reason. They don't factor in their own self-consumption either. That 15W load is likely consuming an additional 30-40W more in just powering the inverter and other circuitry.

 

[John SK]

BMS aren't terribly accurate, especially for low currents < 2A. You might also have issues with BT signal if it's enclosed in metal.

Is it good enough? Probably. I'm pretty lazy, so if it makes things easier, I'd probably exclude it.

I'm lazy too. This vehicle is terribly challenged in terms of space to build a system, at this point. If I started all over from scratch, I'll re-purpose an entire compartment and build it out of aluminum, etc., but for now, I just want to build off what I have and move forward.

That's a good point about metal interfering with the signal. My compartment is of course metal. Thanks for your help.

 

[John SK]

That's a factor, but it's not just that reason. They don't factor in their own self-consumption either. That 15W load is likely consuming an additional 30-40W more in just powering the inverter and other circuitry.

Really, the only thing I need from the BMS is a "reasonably" accurate SOC in terms of Ah and %. I assume I can extrapolate SOC from voltage under resting condition. Not sure. Ins and outs would be great. I'm going to study SOK's manual to see what the app claims to report. I'll try to keep the Trimetric, but it's a PITA to fit it in. The only thing I'd likely miss if I can the Trimetric, is the wire I ran forward to the starter battery so it gives me an accurate voltage on that.

 

[HighTechLab]

Really, the only thing I need from the BMS is a "reasonably" accurate SOC in terms of Ah and %. I assume I can extrapolate SOC from voltage under resting condition. Not sure. Ins and outs would be great. I'm going to study SOK's manual to see what the app claims to report. I'll try to keep the Trimetric, but it's a PITA to fit it in. The only thing I'd likely miss if I can the Trimetric, is the wire I ran forward to the starter battery so it gives me an accurate voltage on that.

The problem with the SOK app is that to calibrate the SOC is requires a complete discharge until BMS UVP and then full recharge to bms OVP - a very time consuming process. A shunt is a far easier and more accurate solution. Perhaps check out the calibration procedure I wrote at support.sokbattery.com

 

[sunshine_eggo]

Really, the only thing I need from the BMS is a "reasonably" accurate SOC in terms of Ah and %. I assume I can extrapolate SOC from voltage under resting condition. Not sure. Ins and outs would be great. I'm going to study SOK's manual to see what the app claims to report. I'll try to keep the Trimetric, but it's a PITA to fit it in. The only thing I'd likely miss if I can the Trimetric, is the wire I ran forward to the starter battery so it gives me an accurate voltage on that.

My response was specific to "solar generators." It does not apply to your situation.

 

[John SK]

The problem with the SOK app is that to calibrate the SOC is requires a complete discharge until BMS UVP and then full recharge to bms OVP - a very time consuming process. A shunt is a far easier and more accurate solution. Perhaps check out the calibration procedure I wrote at support.sokbattery.com

Thanks so much! How often does the app stub its toe and require recalibration? Generalizing works for me if it's technical.

 

[John SK]

I don't recommend SOK's heated batteries - the non-heated are excellent but the heated ones have to be treated just right to work perfectly - most beginners don't take the time to learn how to use them properly and complain like crazy, so that's why I do not have them listed on our site. The logic for when to turn on the heating pads has been significantly improved, but still not perfect.

If you want a heated battery, I strongly recommend Epoch battery. Their BMSs have been flawless despite my many attempts to find issue. We are a dealer for them and will have them on our site when they arrive next week. They are not however, field servicable.

12V 300Ah Heated & Bluetooth LiFePO4 Battery - Epoch Essentials

Get the 12V 300Ah heated & Bluetooth LiFePO4 battery from Epoch Essentials. Charge in sub-zero conditions, control with iOS and Android apps, and enjoy the benefits of smart battery management. 4,000+ cycles, 11-year warranty.

www.epochbatteries.com

Thanks. I'd already bought a couple from SOK. Field serviceability is important for me since the rig is heading to South America for a couple years. If one craps out, and I may carry no spare parts, I figure I can cobble enough parts out of both batteries to keep one working. Warranties don't mean much in thirld world countries. Can't fly with the lithium, most likely. If I suffer a failure, somebody's trash pile will get about 50 pounds heavier.

If he heater works, I have no issue with learning how to use it. But will it work; who knows. I've been trying to figure out what the continuous and peak discharge rates are for the 12V 206H model. The web site, manual and data sheets, and your site, all report entirely different figures. I guess keeping up with the commodity market for components in China, as things constantly change, isn't easy.

 

[John SK]

Update: I bought (2) 206 AH SOK 12V LiFePO4 batts and will modify my compartment to fit them in. Thanks