Jump to content

DIY Lithium/LifePo4 battery build


Gerlach

Recommended Posts

4 minutes ago, Bain Viljoen said:

What is the advantage of this bms if i may ask?

Let me spit out my usual BMS talk... šŸ™‚

I consider a BMS as somewhat of a layered thing, there are things it MUST do, things that it really SHOULD do, and then there are the nice to haves.

A BMS MUST prevent overvoltage or undervoltage conditions on individual cells. A BMS SHOULD balance cells in some manner, and I think all but the very cheapest will do this.

Then comes the nice to haves: A BMS might also track the SOC of the pack, and it might have a communication interface so it can communicate this with another component in the system. In an inverter system this is useful, because a home owner might want to use the top 50% of the battery for "self consumption" and reserve the bottom 50% for an outage... but then you need to know where 50% is.

Finally, the BMS could request charge voltages and charge current limits from the inverter/charger. Some BMSes will (as an example) lower the charge current as the battery approaches full so that the passive balancers don't have to bleed off so much energy. Others might lower the charge voltage to accommodate a low cell (plus a small offset to facilitate balancing).

People sometimes think that a Victron system can't work with these "other" batteries because the BMS comms is either not there or not supported. That's not necessarily true. As long as the BMS does the basics of protecting the battery, it will work just fine. You need to make other plans to track the SOC (eg install a BMV-7xx), and you need to set the charge curve and voltages/current correctly, but for the most part it will work just fine... minus the nice features.

Link to comment
Share on other sites

3 minutes ago, plonkster said:

A BMS MUST prevent overvoltage or undervoltage conditions on individual cells. A BMS SHOULD balance cells in some manner, and I think all but the very cheapest will do this.

So I assume the BMS of the battery in question does this?

4 minutes ago, plonkster said:

Then comes the nice to haves: A BMS might also track the SOC of the pack, and it might have a communication interface so it can communicate this with another component in the system. In an inverter system this is useful, because a home owner might want to use the top 50% of the battery for "self consumption" and reserve the bottom 50% for an outage... but then you need to know where 50% is.

So with aĀ BMV-7xx we get this nice to have?

5 minutes ago, plonkster said:

You need to make other plans to track the SOC (eg install a BMV-7xx), and you need to set the charge curve and voltages/current correctly, but for the most part it will work just fine... minus the nice features.

Right so this battery is not plug and play. Although once the correct charge settings have been entered it will look after itself?

Link to comment
Share on other sites

1 minute ago, deapsquatter said:

So I assume the BMS of the battery in question does this?

Yes.

2 minutes ago, deapsquatter said:

Right so this battery is not plug and play. Although once the correct charge settings have been entered it will look after itself?

You will need to alter the charge voltages as i think a lot of batteries use 15 cells, i use 16.

Other then that it's plug and play

Link to comment
Share on other sites

On 2020/01/13 at 9:07 AM, Bain Viljoen said:

That is the recommended charge yes, But they are guaranteed to last at least 2000 cycles to the 80 percent capacity degradation meaning that you will get 2000 cycles if you do not surpass the Max parameters.Ā It is for this reason that I can give a guarantee on my built packs.They are sealed up and i know they have the necessary protection. The Built in BMS for these units allow a C of 0.66 on these cells. If a customer were to report a degradation in capacity not consistent with the guarantee i would replace it.Ā 

Hope this helps and gives some sort of assurity.Ā 

Bain what is the warranty on your built packs ?Ā  I sent an email to you but not sure if you received it. I usedĀ [email protected]

Link to comment
Share on other sites

Ā 

3 minutes ago, GreenMan said:

Bain what is the warranty on your built packs ?Ā  I sent an email to you but not sure if you received it. I usedĀ [email protected]

I checked my spam folder now, see you sent it yesterday already,Ā  apologies.

As i try to cater for the guys that cant afford these expensive batteries i give a 2 year warranty but it can be extended to 5 year, of course this would incur an increase in the price.

Link to comment
Share on other sites

1 hour ago, deapsquatter said:

So with aĀ BMV-7xx we get this nice to have?

Yes, but it is extra hardware šŸ™‚

BMSes that incorporate SOC tracking have more information available to them, they have per-cell voltages, they can do smart tricks like locking the SOC to 98% until balancing is done, and so on. Other than the smart tricks, the SOC tracking in most BMSes is the same as is done by a Victron BMV: It counts amp hours in and out. The accuracy depends on what kind of sensor it uses. Batteries that use a hall sensor are typically less accurate (at low power values) than those that use a shunt.

As an example, consider the Pylontech UP2500.

Selection_426.thumb.png.1a10fdee58c6f5958c675aa3deb17f15.png

It is a 24V battery with no CAN-bus comms and no SOC tracking. As you can see above, this battery is advertised for backup use. In backup use, you don't care about the SOC so much. You don't stop discharging at a preset SOC... you run it until the grid comes back or the battery is dead (aka BMS disconnect it).

This battery is often advertised as "for Axpert only". Why? Does it have some special electrons that don't work with the others? šŸ™‚

The reason is simple. It has a console port, so you can use it with that setup. It does not have a CAN-bus port, so it does not integrate with a Victron system. Set your voltage correctly and slap a BMV on ... and it will work just fine though!

Link to comment
Share on other sites

9 minutes ago, plonkster said:
2 hours ago, deapsquatter said:

So with aĀ BMV-7xx we get this nice to have?

Yes, but it is extra hardware šŸ™‚

Well, @deapsquatter is talking about a Victron ESS (which stands for Energy Storage System) and one can expect the BMV 7XX to be part of that already.

I don't know if deapsquatter already has this Victron stuff but when he doesn't he should nalso have a look at the Voltronic range of inverters. They work well with the BMV as well via ICC software and are way cheaper.

Link to comment
Share on other sites

1 hour ago, RikH said:

is talking about a Victron ESS (which stands for Energy Storage System) and one can expect the BMV 7XX to be part of that already.

Hehehe yeah I know ESS very very well šŸ™‚

You won't necessarily have a BMV just because its an ESS system. The Multi has its own SOC tracking, and in an AC-tied system (where PV comes in on the AC side and the Multi does all the battery charging) you will use that instead of adding a BMV. Even in systems with DC-tied PV, the solar charger's power is communicated to the Multi so its SOC tracking still works. So you can skip the BMV and rely on only the Multi to do SOC, but in my experience it is not as accurate as using the BMV.

The upside to the "intelligent BMS" (the one that does SOC and has CAN-bus comms) is that you get accurate SOC information without having to install a BMV, and it often represents a financial saving too.

Link to comment
Share on other sites

56 minutes ago, PJJ said:

As well as anybody could that can approve pull requests to :Ā victronenergy /venus :P

I actually don't have access to the master branches on that one (the OS is maintained by another guy), but the ESS components (systemcalc is the main one, but also hub4control, dbus-fronius, dbus-cgwacs for the energy meters.... it is a big system with lots of moving parts šŸ™‚ ).

Link to comment
Share on other sites

1 hour ago, plonkster said:

but the ESS components (systemcalc is the main one, but also hub4control, dbus-fronius, dbus-cgwacs for the energy meters.... it is a big system with lots of moving parts šŸ™‚ ).

I can imagine.

The products that you maintain can also be considered "mission critical" so you can't allow anyone to just commit something to any branch willy nilly (Or so I assume :PĀ )

Link to comment
Share on other sites

  • 2 weeks later...
11 hours ago, JJS said:

@Gerlach I see SAPO finally dit their part :DĀ 

At @JJSĀ Jip!!! they took there time!!!! Will import next time with Scottshipping to get it faster. Did all my crimping Friday night and got the battery connected SaturdayĀ toĀ the Inverter and MPPT. Did some a bit of maths and programming of the units and settings, start charging and doing adjustment till i found the sweet spot for charging from the mppt.Ā Ā By yesterdayĀ morning IĀ got most of the stuff sorted on the BMS and batteries was full charge.

The screen works lekker with some nice info with the setup but the blue toothĀ partĀ Ā is the best. I can sit any place in my house and check what happening and adjust the settings on the battery and check all the cells as it charge and working. Had my first test last night, batteries took over from where MPPT can't supply anymore and this morning at 5 pm it was at 66% at 78.126AH,Ā Ā and it was on 119.1AHĀ Ā when it took over from the mppt. My wife was using her hair dryer and we used the microwave and 2 Led tv's where running and my network system and cctv system and leds lights and fridge and laptop standing on till this morning.Ā 

Planning to build another second setup. Will post photos later of this setup.Ā 

Edited by Gerlach
Link to comment
Share on other sites

7 hours ago, Hennie65 said:

Hi @Gerlach, was it not difficult to get the bluetooth working on the BMS? Have read that it can be a struggle without the correct app or apk. Did you use yourĀ balancer and which one did you get?

@hennie65. Nope was super easy actually. I did a bit google'ing and found the APK app and downloaded it. I'm still waiting for my balancers to arrive because the post take forever but the BMS got it's own setup built in that impressed me. It's got Auto Balance when no charging going in, then it's got Cell Difference Balance that kicks in when charging under 10 amps, this kicks in to when one cell hits the 3.6v charge limit that you can set toĀ in the app. You can do a lot of adjustments in the app. it's got a Charge MOS and Discharge MOS, so when it hits max volts it switch of the charge part but keep the Discharge part open. It's got it's own coulomb meter.Ā 

There still a lot of adjustmentĀ  i need to and get the rite spot for volts and charging and stuff.

Will post some photos now. I still need to transfer the setup in it's cabinet.Ā 

Edited by Gerlach
Link to comment
Share on other sites

You will see one some of the screen shots shows capacity 60AH , then i founded the lifepo4 setting on the BMS and all the settings was adjusted correctly and batteries was fully charge at 119.1AH / 100% SOC.Ā 

FB_IMG_1580212894968.jpg

FB_IMG_1580212898313.jpg

FB_IMG_1580212902688.jpg

FB_IMG_1580212906184.jpg

FB_IMG_1580212910161.jpg

FB_IMG_1580212939945.jpg

FB_IMG_1580212933921.jpg

FB_IMG_1580212948166.jpg

FB_IMG_1580212958415.jpg

FB_IMG_1580213014838.jpg

Link to comment
Share on other sites

44 minutes ago, Gerlach said:

Charge MOS and Discharge MOS

That can get really interesting. Let me tell you a story of how that can get out of hand. Imagine a low-frequency inverter with some kind of PWM control loop to control the charge current. If there is a slight increase in the grid voltage, this causes an equivalent increase in voltage on the secondary side of the transformer, which will usually be compensated for by the control loop, but that takes time.

Now imagine the BMS opens the charge FET so that the battery cannot charge anymore. Now the only weight holding things down on the DC side is the capacitors on the bus, and unless you have a really fast control loop, you may end up with a DC voltage that spikes up really easily.

Ā 

Link to comment
Share on other sites

9 minutes ago, plonkster said:

Now imagine the BMS opens the charge FET so that the battery cannot charge anymore. Now the only weight holding things down on the DC side is the capacitors on the bus, and unless you have a really fast control loop, you may end up with a DC voltage that spikes up really easily.

Big PPPPFFFFFF and smoke!!! ;)Ā heheheheĀ 

Link to comment
Share on other sites

19 minutes ago, Gerlach said:

Big PPPPFFFFFF and smoke!!! ;)Ā heheheheĀ 

Naaah. But a voltage that spikes up to 65V and things switching off, absolutely. Customer wants to know why the inverter/charger caused the battery to disconnect, and the answer is: The voltage spike isn't the cause of the disconnect. It is the result of it!

Link to comment
Share on other sites

On 2020/01/27 at 7:41 AM, Gerlach said:

At @JJSĀ Jip!!! they took there time!!!! Will import next time with Scottshipping to get it faster. Did all my crimping Friday night and got the battery connected SaturdayĀ toĀ the Inverter and MPPT. Did some a bit of maths and programming of the units and settings, start charging and doing adjustment till i found the sweet spot for charging from the mppt.Ā Ā By yesterdayĀ morning IĀ got most of the stuff sorted on the BMS and batteries was full charge.

The screen works lekker with some nice info with the setup but the blue toothĀ partĀ Ā is the best. I can sit any place in my house and check what happening and adjust the settings on the battery and check all the cells as it charge and working. Had my first test last night, batteries took over from where MPPT can't supply anymore and this morning at 5 pm it was at 66% at 78.126AH,Ā Ā and it was on 119.1AHĀ Ā when it took over from the mppt. My wife was using her hair dryer and we used the microwave and 2 Led tv's where running and my network system and cctv system and leds lights and fridge and laptop standing on till this morning.Ā 

Planning to build another second setup. Will post photos later of this setup.Ā 

Question for you, might be dof so bare with me :D

If you build another battery you need another BMS ?Ā  If so how do the BMS's connect with each other ?

Does one use a relay for higher amps like in this video from Will to power the inverter ?

Ā 

Link to comment
Share on other sites

14 hours ago, GVC said:

Unfortunately I only thought to take a photo after I had stripped out the BMS. The one I bought from @Bain Viljoen was the only 15S he had in stock and if I am not mistaken it is the most basic one he sells. It works great though. I am planning to add some LED lights later on just for peace of mind to show that it is on...lolIMG_20200119_104227.thumb.jpg.43ca95245d6f5a3a46b17d34b52a8920.jpg

GVC you only have 15S pack configuration and not 16S ?

Link to comment
Share on other sites

So over the weekend I got my Lifepo4 setup up and running properly and moved the batteries to it's enclosure. Still some stuff to do around the unit like running the DC cables in black sleeve and crimp shorter cables from the battery to the breaker and used the old longer cable for the 2nd unit i want to build. So far the Lifepo4's perform really good and still tweaking my settings and stuff.Ā 

83639488_10158045273027265_3899251046823755776_o.jpg

83897535_10158045272877265_3478380265116532736_o.jpg

84449505_10158045273162265_4853937223487193088_o.jpg

83777906_10158045272727265_1054641584743645184_o.jpg

84345300_10158045272777265_5337786777102974976_o.jpg

84267044_10158051031392265_1369168254647402496_o.jpg

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Ɨ
Ɨ
  • Create New...