Advice, 36V or 48V?

[kazetsukai]

So I just ordered a 14S3P LiFePo4 battery bank, and looking around there aren't a lot of BMS options for 14S LFP, but there are quite a few for 16S LFP banks. I ordered a 36V inverter, but I don't know if changing to a 48V version is an option or not prior to delivery, or if a 36V inverter would work with a 16S LFP bank. I'd have to order more batteries to get a 16S bank anyway, so I'm not really committed to a changeup.

The BMS boards I'm looking at have load leads on the BMS itself, and have potentially higher balance current. I can reuse my two BMSes (SBMS0) for the upper/lower half of the battery bank- the disconnect mechanism would be a Victron Battery Protect (48V/100A) which takes a remote lead from the BMS for low-voltage disconnect. They currently control the remote leads on my MPPT as well.

Thoughts?

Edited March 4, 2021 by kazetsukai

[Sid Genetry Solar]

40 minutes ago, kazetsukai said:

I ordered a 36V inverter, but I don't know if changing to a 48V version is an option or not prior to delivery, or if a 36V inverter would work with a 16S LFP bank.

Absolutely you can switch to a 48v before delivery.  The inverters arrive completely unwired; they have to be set up and configured for the desired system voltage.  You can request a battery voltage change all the way until it's in the box to ship.  Technically, they can be changed in the field--but this voids the warranty (as it's really easy to mess things up when rewiring the transformer!)

For a 16S LFP bank, you definitely want the inverter set up for 48v.  (I personally have a 16S LFP bank...works great with a 48v inverter.)

 

14S LFP...that's 44.8v nominal, 50.4v max, 42v min...on the high side for 36v, but definitely on the low side for 48v.

[kazetsukai]

How would I request the change? Btw, the cells I got:

https://www.alibaba.com/product-detail/4pcs-Lifepo4-3-2V-280Ah-Battery_62517113167.html

44 Cells (two extra), 37kWh. $4700 delivered is somewhere around $0.11/Wh if I did my math right.

Edited March 6, 2021 by kazetsukai

[The Blind Wolf]

12 minutes ago, kazetsukai said:

How would I request the change? Btw, the cells I got:

https://www.alibaba.com/product-detail/4pcs-Lifepo4-3-2V-280Ah-Battery_62517113167.html

44 Cells (two extra), 37kWh. $4700 delivered is somewhere around $0.11/Wh if I did my math right.

Is that the 280A 4cells?  for 344 Bucks?  If that is a real cell and not a fake one I would be getting 16 of them in next week when they pass the 1400 bill.   that would give me 13kwh at 24vfor only $1376, thats dirt cheap for  that would be $106 per KW.  Not bad.

 

Let me know if they are real when you get them. 

[kazetsukai]

2 hours ago, The Blind Wolf said:

Is that the 280A 4cells?  for 344 Bucks?  If that is a real cell and not a fake one I would be getting 16 of them in next week when they pass the 1400 bill.   that would give me 13kwh at 24vfor only $1376, thats dirt cheap for  that would be $106 per KW.  Not bad.

 

Let me know if they are real when you get them. 

I ordered them because of testing done by Off Grid Garage (YouTube):

 

[Sid Genetry Solar]

4 hours ago, kazetsukai said:

How would I request the change?

Probably the best way would be to call Sean during business hours and ask him to adjust your order to 48v.  I don't have access to the order list (at least right now!), so it's not like I can adjust the order.

[Sid Genetry Solar]

5 hours ago, kazetsukai said:

44 Cells (two extra), 37kWh. $4700 delivered is somewhere around $0.11/Wh if I did my math right.

Roughly $127/kwh--really a pretty good price.  I thought I did super well making my pack out of 32650 NOS (new old stock) LFP cells for roughly $120/kwh--so that's a really good price. 

It's always good to run up the cost calculations on other options and see just how they price per KWH...to see how good a certain price really is.

• Simpliphi 3.8kw cells come out at ($2,525 / 3.8) = $664/kWh.  Yeah, ouch.
• DIY with BatteryHookup 6Ah LFP cells works out to roughly $195/kWh.  Not too terrible, though they do require a considerable amount of work to assemble...think 1,000 cells for 19kwh.

[The Blind Wolf]

27 minutes ago, Sid Genetry Solar said:

Roughly $127/kwh--really a pretty good price.  I thought I did super well making my pack out of 32650 NOS (new old stock) LFP cells for roughly $120/kwh--so that's a really good price. 

It's always good to run up the cost calculations on other options and see just how they price per KWH...to see how good a certain price really is.

• Simpliphi 3.8kw cells come out at ($2,525 / 3.8) = $664/kWh.  Yeah, ouch.
• DIY with BatteryHookup 6Ah LFP cells works out to roughly $195/kWh.  Not too terrible, though they do require a considerable amount of work to assemble...think 1,000 cells for 19kwh.

Yeah, three of my batts 12v are made witht he battery hook  up 6ah.  and really, if you don't want to assemble them now they offer a 20 cell modual 4 pack to make a 12v for $320, which isn't bad for a 100ah battery. all you got to do is throw on a bms which amazon is the place to go for your dayly bms,  so for a 48v 100ah setup thats roughly $1500 for4.8kw bank.  just get four cases of those and one 48v 16s bms and your good to go.

 

I just hate the cost when going to a higher voltage.  to me 24v with the 6k GS Inverters is the sweet spot for small to medium house size.  If I had a family, then that would be a different story, since I live by my self I can get by with it.  The highest I've ever seen my watt usage went up to is 15k, and thats with the whole hose heater and the water heater hitting at the same time.  Other then that I hover around 400 watts and with this grow tent setup I got going, its goes up and down with the heaters in the tent from 400 watt to 2000 watts and only for a few mins.

[kazetsukai]

1 hour ago, Sid Genetry Solar said:

It's always good to run up the cost calculations on other options and see just how they price per KWH...to see how good a certain price really is.

I can't understand why people don't see how insanely expensive the "drop-in replacement" 12V LFP batteries are... 

34 minutes ago, The Blind Wolf said:

to me 24v with the 6k GS Inverters is the sweet spot for small to medium house size.  If I had a family, then that would be a different story, since I live by my self I can get by with it.  The highest I've ever seen my watt usage went up to is 15k, and thats with the whole hose heater and the water heater hitting at the same time.  Other then that I hover around 400 watts and with this grow tent setup I got going, its goes up and down with the heaters in the tent from 400 watt to 2000 watts and only for a few mins.

I just checked- sans climate control I'm drawing 421W, 284.5W on the AC side:

(DC side not shown)

400W is impressive, and I live in a bus, not a house.

Highest I've seen my draws... heat pump going, a small space heater and the convection oven, around 4000W-5000W.

[Waterman]

39 minutes ago, kazetsukai said:

I can't understand why people don't see how insanely expensive the "drop-in replacement" 12V LFP batteries are... 

I just checked- sans climate control I'm drawing 421W, 284.5W on the AC side:

(DC side not shown)

400W is impressive, and I live in a bus, not a house.

Highest I've seen my draws... heat pump going, a small space heater and the convection oven, around 4000W-5000W.

We draw on average 3kWh an hour during the day and about 2.5kWh an hour at night for an average of 67kWh a day. But then there really isn't much time when the A/C is off. But if I'm doing an hour's worth of welding, that can add 10kWh to the bill right there.

[The Blind Wolf]

4 hours ago, kazetsukai said:

I can't understand why people don't see how insanely expensive the "drop-in replacement" 12V LFP batteries are... 

I just checked- sans climate control I'm drawing 421W, 284.5W on the AC side:

(DC side not shown)

400W is impressive, and I live in a bus, not a house.

Highest I've seen my draws... heat pump going, a small space heater and the convection oven, around 4000W-5000W.

You would be better off to do 24v in that case, less chance of something going bad and losing a battery bank cause of one bad battery.  Just my thoughts. cause I ran a 24 foot box truck with heat pump AC unit and lights and freezer off of 12v useing 4 led batteries off a 6k go power inverter with no issue for hours before having to crank the truck up.  And that was useing a stupid modify sign wave inverter, which is the worse thing for a heat pump or any motor setup.

[kazetsukai]

7 hours ago, The Blind Wolf said:

You would be better off to do 24v in that case, less chance of something going bad and losing a battery bank cause of one bad battery.  Just my thoughts. cause I ran a 24 foot box truck with heat pump AC unit and lights and freezer off of 12v useing 4 led batteries off a 6k go power inverter with no issue for hours before having to crank the truck up.  And that was useing a stupid modify sign wave inverter, which is the worse thing for a heat pump or any motor setup.

Could you clarify- in what case? I'm running a 48V system. I used to run 24V until I did my first solar upgrade (700W -> 3000W of panels). My 150/100A Victron can only handle around 2400W of PV when running 24V, whereas with 48V it can handle 4800W of PV. Now that I'm adding another 3000W of panels to the roof for 6000W total, I can't really escape needing a second controller.

My current batteries (Teslas) have inherent redundancy- they're each an array of 18650s in 6S74P configuration, any one cell going bad would require something rather extreme. My new bank is going to be either 14S3P or 16S3P, with a pair of spares in case any one cell goes bad.

BTW people, you can edit the quote block to reduce the number of lines, you don't have to repost all of the images/etc that a previous commenter made:

13 hours ago, kazetsukai said:

Highest I've seen my draws... heat pump going, a small space heater and the convection oven, around 4000W-5000W.

 

[Sid Genetry Solar]

23 minutes ago, kazetsukai said:

Could you clarify- in what case? I'm running a 48V system. I used to run 24V until I did my first solar upgrade (700W -> 3000W of panels). My 150/100A Victron can only handle around 2400W of PV when running 24V, whereas with 48V it can handle 4800W of PV. Now that I'm adding another 3000W of panels to the roof for 6000W total, I can't really escape needing a second controller.

I'd say to stay at 48v.  Apart from cost of the MPPTs, system voltage doesn't make an extreme difference in cost--but if it costs twice as much in charge controllers to do 24v vs 48v...well, I went 48v 😉 .

Not to mention thinner wires are cheaper, and the system will be more efficient.  There's a reason the big power transmission lines run in the KV range.

[kazetsukai]

54 minutes ago, Sid Genetry Solar said:

I'd say to stay at 48v.  Apart from cost of the MPPTs, system voltage doesn't make an extreme difference in cost--but if it costs twice as much in charge controllers to do 24v vs 48v...well, I went 48v 😉 .

Not to mention thinner wires are cheaper, and the system will be more efficient.  There's a reason the big power transmission lines run in the KV range.

This sums up why I moved from 24V to 48V. Those Victrons aren't cheap... Many people on skoolie.net running 12V systems see scenarios where they're well over 200A of charge/draw, I think that's insane. I do more with my system than most and my peak draws are still under 100A.

More or less just trying to understand his rationale than anything.

[Sid Genetry Solar]

2 hours ago, kazetsukai said:

More or less just trying to understand his rationale than anything.

Sounds like a lead-acid 12v battery setup.

3 hours ago, kazetsukai said:

My 150/100A Victron can only handle around 2400W of PV when running 24V, whereas with 48V it can handle 4800W of PV. Now that I'm adding another 3000W of panels to the roof for 6000W total, I can't really escape needing a second controller.

Another option you might consider is the Epever Tracer MPPT series.  They're a good bit cheaper--$420 for a 200v input 100A battery output model on eBay right now.  I personally have 2 of them (Tracer 8420ANs to be precise, i.e. 80A, 200v max input), and for the price, I really can't complain.  Definitely no comparison to the (much more expensive) Morningstar Tristar TS-MPPT-60 that I started out with--but I somehow blew one of those out via MODBUS commands.  (Warranty was stellar; they replaced it with very quick shipping.)

The only issue I have had with the Epever Tracers (besides that either a computer cable or their "remote meter" is required for configuration setup--well, same for the Morningstar...), is that the actual voltage regulation is quite slow.  Meaning that if you go from a big load to no load, the battery voltage will surge for 15-30 seconds.  Same on the other direction: putting a huge load on it, the battery voltage will sag for 15-30 seconds.  Obviously, this is a software issue--and probably a band-aid for oscillations or other issues they might have had.  (Definitely not an issue on the Morningstar though--I can go from 20W to 3,300W and back in the blink of an eye.)

But for the price...and the 200v max input...not to mention RS-485 MODBUS (@115kbaud though), as well as MODBUS-controllable relay outputs, etc., there's some potential with the Tracers.  Not to mention that they don't have a cooling fan--they use a huge heatsink on the back.

[kazetsukai]

4 minutes ago, Sid Genetry Solar said:

Another option you might consider is the Epever Tracer MPPT series. 

...

Not to mention that they don't have a cooling fan--they use a huge heatsink on the back.

Victron has my money for the forseeable future, the myriad of connectivity options and presentation is pretty hands-down awesome. I wrote a Java library to talk to VE.Direct devices: https://github.com/kazetsukaimiko/freedriver/tree/master/victron

The voltage surging/sagging issue - that could screw up some more sensitive items.

The Victrons also have big heatsinks/fanless as you likely know, I'd be adverse to any charge controller with a fan.

[The Blind Wolf]

3 hours ago, Sid Genetry Solar said:

I'd say to stay at 48v.  Apart from cost of the MPPTs, system voltage doesn't make an extreme difference in cost--but if it costs twice as much in charge controllers to do 24v vs 48v...well, I went 48v 😉 .

Not to mention thinner wires are cheaper, and the system will be more efficient.  There's a reason the big power transmission lines run in the KV range.

Well, if you already at 48v, then yes its fine, however, to me 48v, would mean have to get more panels and that would mean the wind turbin I got is no longer able to be use cause its o nly rated for 12v or 24v. and I doubt its wise to mix different Ah batterys, for me to be able to pull off 48 v, I got two 200 ah and two 100 ah batteries, doubt i can connect them and get away with a 48v, the 100 ah would charge up before the 200 ah batterys would.

 

And besides, 24v at 6k is only 300 amp at 24 v, which is better then 600 at 12v, cause the wire I got right now was far 12v and its thicker then the wire that comes into the house so I should be able to pull over 600 amp on them for two 24v inverters.  As long as I got enough batteries to push over 600 Amps at 24v I should be good.

 

Sid, you would know, having two 12v batts able to push out 100 amh each would haveing two of them together means it can pull 200 amp at 24v? or still restricted to 1j00 amps?

[The Blind Wolf]

57 minutes ago, Sid Genetry Solar said:

Sounds like a lead-acid 12v battery setup.

Another option you might consider is the Epever Tracer MPPT series.  They're a good bit cheaper--$420 for a 200v input 100A battery output model on eBay right now.  I personally have 2 of them (Tracer 8420ANs to be precise, i.e. 80A, 200v max input), and for the price, I really can't complain.  Definitely no comparison to the (much more expensive) Morningstar Tristar TS-MPPT-60 that I started out with--but I somehow blew one of those out via MODBUS commands.  (Warranty was stellar; they replaced it with very quick shipping.)

The only issue I have had with the Epever Tracers (besides that either a computer cable or their "remote meter" is required for configuration setup--well, same for the Morningstar...), is that the actual voltage regulation is quite slow.  Meaning that if you go from a big load to no load, the battery voltage will surge for 15-30 seconds.  Same on the other direction: putting a huge load on it, the battery voltage will sag for 15-30 seconds.  Obviously, this is a software issue--and probably a band-aid for oscillations or other issues they might have had.  (Definitely not an issue on the Morningstar though--I can go from 20W to 3,300W and back in the blink of an eye.)

But for the price...and the 200v max input...not to mention RS-485 MODBUS (@115kbaud though), as well as MODBUS-controllable relay outputs, etc., there's some potential with the Tracers.  Not to mention that they don't have a cooling fan--they use a huge heatsink on the back.

I have one of thos Epever  40A tracer, and I can't not connect to it with ethernet, or wifi modual, so I can't even program it.  I hate the thing. so switch to Make sky blue and I do have a victron 12/24v/ 15A that I started off with when I got into solar.  I like the sky blue controllers.

[kazetsukai]

16 minutes ago, The Blind Wolf said:

Sid, you would know, having two 12v batts able to push out 100 amh each would haveing two of them together means it can pull 200 amp at 24v? or still restricted to 1j00 amps?

2 Batteries * 12V * 100Ah = 2400Wh. Wh always adds up to the same regardless of the configuration. In Series, that's 24V 100Ah (2400Wh), in parallel that's 12V 200Ah.

In parallel, you can draw the accumulative amperage of the rating of all of the batteries in the group. In Series, you are I believe limited to the amperage of the lowest rated battery in the series- both also limited by cable size. While under some circumstances you can mix different kinds and capacities of battery, it isn't recommended.

16 minutes ago, The Blind Wolf said:

And besides, 24v at 6k is only 300 amp at 24 v, which is better then 600 at 12v, cause the wire I got right now was far 12v and its thicker then the wire that comes into the house so I should be able to pull over 600 amp on them for two 24v inverters.  As long as I got enough batteries to push over 600 Amps at 24v I should be good.

"Only" 300A, wow. I don't know your requirements or average usage but I think 300A is an insanely high draw, and that you are better off looking at a higher voltage system if possible.

If "the wire that comes into the house" is what I think it is, its 240V AC and is never going to see that kind of current.

Edited March 7, 2021 by kazetsukai

[Sid Genetry Solar]

17 minutes ago, The Blind Wolf said:

I have one of thos Epever  40A tracer, and I can't not connect to it with ethernet, or wifi modual, so I can't even program it.

The RJ45 connectors on the Epever Tracers are NOT an Ethernet port.  That's an RS-485 port that must be connected to a compatible RS-485 adapter.  Unfortunately, I have no experience with the Epever Tracer's RS-485 to WiFi adapter.

[The Blind Wolf]

Yeah well, AC wire is different then DC wire, AC runs on the outside of the wire and DC runs on the inside I think  or it could be reverse.  Anyhow, yes 300 A is high, but one GS 6 inverter at 24v would use that, and then drop down since I only hit a high watt for a few mintues it no big deal, I stay on low end of power, the second GS inverter would be only used maybe once a day if that for anything.  During the summer, it would probley never get used unless I run the dryer, and turn on a microwave or air frier..

 

I'll stick with 24v, all my panels I have outside are 100 watt panels.  I have more panels sitting in the house right now waiting to go outisde when it warms up.  Going to order probley another 16 of them and another 60a Make sky bluee controller.

 

You also got to remeber I'm total blind, so I don't even use T.V.s and everything else most folks used during the day, matter, of fact all my lights are led, and they stay off all the time 😛

[The Blind Wolf]

1 minute ago, Sid Genetry Solar said:

The RJ45 connectors on the Epever Tracers are NOT an Ethernet port.  That's an RS-485 port that must be connected to a compatible RS-485 adapter.  Unfortunately, I have no experience with the Epever Tracer's RS-485 to WiFi adapter.

I bought the cable witht he usb on the end that made for it and the wifi adaptor, neither one I could get working. so I gave up on it, I can use it, just can't program it to do anything I want.

[kazetsukai]

7 hours ago, The Blind Wolf said:

I bought the cable witht he usb on the end that made for it and the wifi adaptor, neither one I could get working. so I gave up on it, I can use it, just can't program it to do anything I want.

If I had one I could probably figure it out. What were you hoping to do with it?

 @Sid Genetry Solar do they have any protocol specs for use with the USB or WiFi adapters?

[Sid Genetry Solar]

9 minutes ago, kazetsukai said:

do they have any protocol specs for use with the USB or WiFi adapters?

I did manage to find a MODBUS protocol PDF document of the registers, etc.  Haven't gotten enough other stuff off my plate yet to get to it though.

[TheButcher]

On 3/8/2021 at 3:58 AM, The Blind Wolf said:

I bought the cable witht he usb on the end that made for it and the wifi adaptor, neither one I could get working. so I gave up on it, I can use it, just can't program it to do anything I want.

It sounds a lot like you would benefit from using the optional remote control panel.  It lets you do pretty much every configuration item you can do via the PC software.  Given the rather bare bones options that the MakeSkyBlue units present, you can't even set a time limit nor tail current for end of absorption charge, I'm surprised that you aren't happy with what the epever can do via the less capable configuration with the built in display / buttons.

 

Oh, you are really blind?  That'd kinda rule out the remote control panel then... but how do you go about configuring the MakeSkyBlue if you can't read the LCD?

Edited March 19, 2021 by TheButcher