Lithium vs Lead Acid

[the_terrible_triplett]

I'm cannot argue the semantics nor debate the technicalities.

How they DEMONSTATED what happens at LOW RPM's, it matters not that their is no BMS, for you don't set the charge amps on the BMS.

The titbits that kicked me in the face:
- Low alternator speeds, the needed cooling is lacking.
- When a BMS disconnects the battery from the charging source, this can damage the alternator if not done properly.


BMS disconnecting:
Now I do have some experience ito having had to deal with bad to severe DC Ripples (5kva inverter actually switches off when very bad), when a BMS "disconnects" due to excessive cell imbalances.

The imbalances tend to become very prominent when the bank is nearing full charge.

Now remember, to get a banks cells balanced can take up to +- a week, sometimes longer, because generally only 30mA is used to balance cells, depending on the BMS. And +- a week is on a daily used bank.

If you have a App to see the individual cells, how the volts go up and down, how the BMS balances them, it is quite a sight to see.

So if the BMS has no interface to the charge source, that the charge source can know to "slow down" the charge amps, it can become a shiite storm I tell you, when that BMS disconnects due to excessive cell imbalances.

And that shiite storm, it hits you when you least expect it.

Charging a lithium bank without any interface between BMS and charge source, is a challenge.

My 2 cents.
But hey, each to their own.


EDIT: You never want to see this ... example of what is possible between BMS and system.

[cainslie]

Charging a lithium bank without any interface between BMS and charge source, is a challenge.

If you're dropping R10k on a battery, it only makes sense to spend that little bit more on a charger or DCDC that will look after that battery for you.

[the_terrible_triplett]

If you're dropping R10k on a battery, it only makes sense to spend that little bit more on a charger or DCDC that will look after that battery for you.

Amen ... and protect your alternator at the same time.

[stormjp]

I'm cannot argue the semantics nor debate the technicalities.

How they DEMONSTATED what happens at LOW RPM's, it matters not that their is no BMS, for you don't set the charge amps on the BMS.

The titbits that kicked me in the face:
- Low alternator speeds, the needed cooling is lacking.
- When a BMS disconnects the battery from the charging source, this can damage the alternator if not done properly.


BMS disconnecting:
Now I do have some experience ito having had to deal with bad to severe DC Ripples (5kva inverter actually switches off when very bad), when a BMS "disconnects" due to excessive cell imbalances.

The imbalances tend to become very prominent when the bank is nearing full charge.

Now remember, to get a banks cells balanced can take up to +- a week, sometimes longer, because generally only 30mA is used to balance cells, depending on the BMS. And +- a week is on a daily used bank.

If you have a App to see the individual cells, how the volts go up and down, how the BMS balances them, it is quite a sight to see.

So if the BMS has no interface to the charge source, that the charge source can know to "slow down" the charge amps, it can become a shiite storm I tell you, when that BMS disconnects due to excessive cell imbalances.

And that shiite storm, it hits you when you least expect it.

Charging a lithium bank without any interface between BMS and charge source, is a challenge.

My 2 cents.
But hey, each to their own.


EDIT: You never want to see this ... example of what is possible between BMS and system.

So what are you trying to get to? To advocate people to stay away from Lifepo4?

You can google problems with anything, whether it be a battery, a house roof, or a car and you'll find people having problems.

Again, trying to push 90Amps through probably 10mm2 cable directly to a battery without BMS from your alternator is looking for trouble.

Anyway, each to their own.

[the_terrible_triplett]

So what are you trying to get to? To advocate people to stay away from Lifepo4?

I'm saying, just like with lead acid batteries, roofs, cars, understand the tech involved, that you can get value for YOUR money.

Nothing more. Nothing less.

[the_terrible_triplett]

Again, trying to push 90Amps through probably 10mm2 cable directly to a battery without BMS from your alternator is looking for trouble.

The above is ONE example, and same goes for lead acid AND lithium, ANY DC current for that matter.

And we all know that to protect any DC cable, you install the correct fuse for the size cable used.
The max DC amps determines the cable length and size.
The cable size dictates the max fuse required, to protect the cable.

As I said, a BMS will disconnect for various reasons, to protect the lithium cells/bank. And ONE of the built in protections is when the cells, as the bank gets fully charged, gets out of sync like one (1) lowest cell is 3.452v and one (1) highest cell is 3.61v as an EXAMPLE. The BMS will protect the bank/cells.

So depending on the BMS built in protections/software, if a cell voltage gets above the BMS's protections parameters, and the BMS cannot balance the cell/s fast enough, then that BMS will disconnect from the charge source to protect the cell/bank, until it can rectify the problem.

It can be for but a few seconds, but in that time, that second or two, when it disconnects, it is a cluster f..k on the DC bus, the caps ... the alternator, for where will that, your example, 90amps go when the BMS disconnects?

Have learnt the hard way:
Nearly costed me a 5kva Victron Multiplus II, because of cell imbalances, causing repeated DC Ripples.
Personally saw a 250/100 MPPT get damaged BECAUSE the BMS disconnected, due to cell imbalances.
BOTH the above happening when the bank is at 95% or higher.

The cost of the BMS/alternator are pocket change compared to the above two item costs.

[stormjp]

The above is ONE example, and same goes for lead acid AND lithium, ANY DC current for that matter.

And we all know that to protect any DC cable, you install the correct fuse for the size cable used.
The max DC amps determines the cable length and size.
The cable size dictates the max fuse required, to protect the cable.

As I said, a BMS will disconnect for various reasons, to protect the lithium cells/bank. And ONE of the built in protections is when the cells, as the bank gets fully charged, gets out of sync like one (1) lowest cell is 3.452v and one (1) highest cell is 3.61v as an EXAMPLE. The BMS will protect the bank/cells.

So depending on the BMS built in protections/software, if a cell voltage gets above the BMS's protections parameters, and the BMS cannot balance the cell/s fast enough, then that BMS will disconnect from the charge source to protect the cell/bank, until it can rectify the problem.

It can be for but a few seconds, but in that time, that second or two, when it disconnects, it is a cluster f..k on the DC bus, the caps ... the alternator, for where will that, your example, 90amps go when the BMS disconnects?

Have learnt the hard way:
Nearly costed me a 5kva Victron Multiplus II, because of cell imbalances, causing repeated DC Ripples.
Personally saw a 250/100 MPPT get damaged BECAUSE the BMS disconnected, due to cell imbalances.
BOTH the above happening when the bank is at 95% or higher.

The cost of the BMS/alternator are pocket change compared to the above two item costs.

Probably not a good idea to try build an inverter to run a house into your car either.

[the_terrible_triplett]

Probably not a good idea to try build an inverter to run a house into your car either.

- the sky is the limit ...

https://www.victronenergy.com/blog/2...sla-ambulance/

[the_terrible_triplett]

Probably not a good idea to try build an inverter to run a house into your car either.

Titbit to add:
With the DC Ripple issue on the inverter, the 250/100 having gotten damaged, the data showed, in both cases, that it was a fully charged bank and <250w AC loads powered at the time of the dramas.

For the Newbies:
In Pic 1, the cell in red, at 3.590v, when it hits 3.600v the BMS alarm goes off, when it goes to 3.61v or more, BMS disconnects aka shiite hits the fan.
In my case, that sell was the original problem, nearly costing me a inverter. Daly BMS I had could never balance the 16x150ah bank.
New Bluetooth enable BMS, 5 days and "The Bulb" and the bank was sorted.
"The Bulb", was on a suggestion from a good friend, I manually helped it on with that 12v car light bulb connected connected onto cell 1, adding more resistance, giving the BMS a chance to balance.

I only found that problem after I upgraded to the new Bluetooth enabled BMS, Daly I had did not have that ability.

Pic 2 is now how it looks most of the time ... a beautifully balanced bank ... 0.01v difference sometimes.

And "The Bulb" ... to sort them pesky cells.

[JLK]

Hi JLK

I Installed a DC-DC charger in my battery box, fed from a cable running directly from the vehicle battery and to date it has functioned flawlessly. Everything has been fused properly, as im scared of overheat/shorts!

Ok , looks like the WRND DC charger is LiFePO4 battery compactable. Their charger float stage at 13.7 V, which is a sort mean for the various batteries types. According Google LiFePo4 don't need to be float charge, or preferable float charge at less than 13.6V. However seems 13.8 V is also acceptable, some say, so if you charger float charge at 13.8V, it should not be train smash, as the volts at the battery will be slightly les than 13.8 due to volt drop in the cable. But disconnect such charger if the battery is not used, I would think.

I bought a 'drop in replacement' 100Ah 12.8V lifepo4 battery in the mean time. Looks like it has built in BMS that caters for overcharging etc. Will anyway test it with my power panels and see what's cooking.

[Lightweight]

Titbit to add:
With the DC Ripple issue on the inverter, the 250/100 having gotten damaged, the data showed, in both cases, that it was a fully charged bank and <250w AC loads powered at the time of the dramas.

For the Newbies:
In Pic 1, the cell in red, at 3.590v, when it hits 3.600v the BMS alarm goes off, when it goes to 3.61v or more, BMS disconnects aka shiite hits the fan.
In my case, that sell was the original problem, nearly costing me a inverter. Daly BMS I had could never balance the 16x150ah bank.
New Bluetooth enable BMS, 5 days and "The Bulb" and the bank was sorted.
"The Bulb", was on a suggestion from a good friend, I manually helped it on with that 12v car light bulb connected connected onto cell 1, adding more resistance, giving the BMS a chance to balance.

I only found that problem after I upgraded to the new Bluetooth enabled BMS, Daly I had did not have that ability.

Pic 2 is now how it looks most of the time ... a beautifully balanced bank ... 0.01v difference sometimes.

And "The Bulb" ... to sort them pesky cells.

Yikes! This is scary! Do you have any comments on post #190 - the WRND dc- dc charger/MPPT regulator all in 1 unit? The unit in combination with a standard Daly bms ? Plus a fuse to the LifePO4 battery? Would it protect against the disaster you described earlier?

[the_terrible_triplett]

Yikes! This is scary! Do you have any comments on post #190 - the WRND dc- dc charger/MPPT regulator all in 1 unit? The unit in combination with a standard Daly bms ? Plus a fuse to the LifePO4 battery? Would it protect against the disaster you described earlier?

It is to be noted that my post was for DIY'ers, one was on a bank with brand new cells - where the problem surfaced 1st, the other 2nd Life cells, where I learned about bottom and top balancing.

I don't think it will easily happen with brand name lithium banks.

Post #190
I only use Victron, because even with their built in default settings, I could not use them at all. Over time I had to find the sweet spot for my 2 banks, and they differ subtly.

If one is into DIY lithium banks, what I've learn the last few months, I'm 100% for:
1) MPPT/Inverter that can be programmed to the n'th degree to handle any quirks one finds.
2) BMS must interface with the main system unless it is a brand name approved to work with ones equipment that does not interface.
3) You must be able to see each cell voltages on your phone when BMS is interface.

Nice to have, a BMS that can:
Handle 24v or a 48v bank, even a 36v or 72v bank if that is a need.
Handle sells other than just LifePo4, just in case one changes ones mind later.


EDIT: The core problem I found with DIY banks, if a cell gets too far out of whack, the BMS will disconnect ... as it is supposed to ... and that is bad mojo for the rest of the equipment.
It is the same as when you disconnect a battery bank from a running system.

EDIT2: All my cells are now between 0.004-0.015v difference at 100% SOC.

[VVTi]

For the Newbies:
Daly BMS I had could never balance the 16x150ah bank.
New Bluetooth enable BMS, 5 days and "The Bulb" and the bank was sorted.

Hi TTT, what is the brand of this fancy BMS of yours and where did you buy it?

[the_terrible_triplett]

Hi TTT, what is the brand of this fancy BMS of yours and where did you buy it?

These: https://www.lithiumbatterypcb.com/pr...bluetooth-bms/
Found a supplier for them for SA.

Have 2 of the "big" ones, 200amp, that can go onto 24v and 48v banks and a 12v 120a one for the 12v bank.
Latest model I ordered has the Bluetooth and a separate UART module, the access via the Venus AND my phone.
Connected to the Victron setup, using a full blown Venus and a Rpi Venus (Venus software, free, on a Rpi) for the smaller systems.

The Software I use to integrate the above BMS'es with my Victron kits ... thank YOU Louis! : https://energytalk.co.za/t/diy-seria...-victron-gx/80

EDIT: Can also add a CANbus port to the BMS ... first one I ordered that with, till I did not need it thanks to Louis.

[the_terrible_triplett]

Route I'm going: Get the right BMS for the right price ... then worry about the cells.

See, assuming you can program the shiite out of the BMS, MPPT and inverter, you have absolutely no limits.

If you have access to the settings to adjust as needed, THAT is worth every cent spent over time.

[VVTi]

These: https://www.lithiumbatterypcb.com/pr...bluetooth-bms/
Found a supplier for them for SA.

Have 2 of the "big" ones, 200amp, that can go onto 24v and 48v banks and a 12v 120a one for the 12v bank.
Latest model I ordered has the Bluetooth and a separate UART module, the access via the Venus AND my phone.

Connected to the Victron setup, using a full blown Venus and a Rpi Venus (Venus software, free, on a Rpi) for the smaller systems.

The Software I use to integrate the above BMS'es with my Victron kits ... thank YOU Louis! : https://energytalk.co.za/t/diy-seria...-victron-gx/80

Impressive! What's the name of the the local supplier?

[the_terrible_triplett]

Impressive! What's the name of the the local supplier?

I'm learning about importing them, as I went direct to the manufacturer.
If one has patience, as it takes about 15-25 days to ship to SA.
If I see there is a market, I will make a plan for more, aka the local importer.

[Lightweight]

It is to be noted that my post was for DIY'ers, one was on a bank with brand new cells - where the problem surfaced 1st, the other 2nd Life cells, where I learned about bottom and top balancing.

I don't think it will easily happen with brand name lithium banks.

Post #190
I only use Victron, because even with their built in default settings, I could not use them at all. Over time I had to find the sweet spot for my 2 banks, and they differ subtly.

If one is into DIY lithium banks, what I've learn the last few months, I'm 100% for:
1) MPPT/Inverter that can be programmed to the n'th degree to handle any quirks one finds.
2) BMS must interface with the main system unless it is a brand name approved to work with ones equipment that does not interface.
3) You must be able to see each cell voltages on your phone when BMS is interface.

Nice to have, a BMS that can:
Handle 24v or a 48v bank, even a 36v or 72v bank if that is a need.
Handle sells other than just LifePo4, just in case one changes ones mind later.


EDIT: The core problem I found with DIY banks, if a cell gets too far out of whack, the BMS will disconnect ... as it is supposed to ... and that is bad mojo for the rest of the equipment.
It is the same as when you disconnect a battery bank from a running system.

EDIT2: All my cells are now between 0.004-0.015v difference at 100% SOC.

Thanks TTT
I suppose my setup is a hybrid in that it is 4 x 3.2V Lithtech 272AH LIFEPO4 prismatic cells in series with a standard Daly bms with 30A inline fuses at the bank and at the MPPT/DCDC unit. Have the opportunity to manually check voltage if/when required. Your expertise is greatly appreciated and warnings heeded.

[the_terrible_triplett]

Thanks TTT
... a standard Daly bms with 30A inline fuses at the bank and at the MPPT/DCDC unit. Have the opportunity to manually check voltage if/when required. Your expertise is greatly appreciated and warnings heeded.

Only a pleasure.

I share so that others, if they ever see a similar issue, can pick up on the problem faster than I / we did.

Long read ...

More Info:
The BMS supplier kept on saying that I'm the only Victron person out of all his Victron customers, that had this problem. It must be something I did/do.
Victron, who knows DC Ripples 9/10 times equates to too small cabling, too long cabling, bad crimps, too small a bank, loose connection, faulty inverter etc. A lot of documentation on that.

I suspected that the battery side volts went above 60v, the BMS's max, forcing it to shut down.
It was also suggested that a cell/s could get out of whack.
What clouded these issues, even though I bought a better Multimeter, I could NEVER "catch" a cell out of whack by the time I could check as it happens too "quick" to check 16 cells voltages to find a cell/s, gets even worse under immense stress when the inverter warns or worse, switches off.

I DID see volts at 60v on the data though, not higher, as the BMS switched off, so no data.
In the process I learnt that on the battery side of a 48v system, that you can see +60v when big loads come off/on, and BMS must handle that/protect the cells against that.
As I said, the BMS I had back then, max 60v protection.
New ones are 75v, the other 80v.

So all of that went round and round.

I even went from 5m return length 50mm2 cable down to 2m return length 50mm2 cable ending up with 4m return length 70mm2 cable.
Lugs where checked and double checked, the 70mm2 had hydraulically crimped lugs.
So that removed that as an potential cause.

THEN:
The first DAY the 1st new BMS went in, O Boy, what a fright!!!
These BMS's warns you with a loud persistent beep that a cell just skidded out of whack, BEFORE it starts protecting, AND you can adjust those settings.

So, if you keep your phone on when the bank charges back up, you can actually see the cell/s creeping out of whack, then it "shoots" up to above 3.6v.
Because one can now see each cell, now one can "assist" the balancing algorithm by adding "The Bulb V2" across a sell, to increase resistance on that cell, dropping the volts quite "fast".

And that is what I did with the 16 x 150ah new cells. Got them quite neat over a day or two.
Then I added Louis software, which helped a LOT as it throttles the charge current the higher the SOC goes. THAT made keeping all 16 cells, a breeze, the BMS interfacing with the system.


O, that reminds me:
Most BMS's balance at +-30mA, so it can take week/s to balance a new DIY bank, unless the cell supplier has done the balancing properly for one, per cell.
These new BMS's, one is 170mA, the other one is 260mA balancing current.
And if you actively get involved, you can balance an entire bank within a day or two, or 1-2 charge cycles.

Having software interfacing with the BMS, that is the cherry on the cake on a daily cycles bank. I take my banks down to 30% SOC, 70% DOD, every day.

Conclusion:
DIY banks are a ton of fun ... wish I knew what I know now, when I got the first bank, having nearly "lost" a 5kva Victron MPII, having seen a Victron 250/100 MPPT get damaged, and everyone knows what a 5kva MPII and a 250/100 MPPT costs.

Now I have learnt about bottom balancing, top balancing ... it really was fun I tell you! No jokes.
8 x 100ah cells, balanced them in batches of 4, 12v system, then all 8 on a 24v system ... awesome experience.

And I also want to say, Thank you Victron! ... having replaced that MPPT under warranty, even with the warning: Sort the issue out ...
That MPPT blown bank was replaced with a Revov bank ... the supplier refunded instantly, Cudo's to them for that!

Pictures:
The one is the BMS I had, same one was used with the 250/100 MPPT, and "The Bulb V2" ... thanks to @Gerlach for that idea!

[Die SwartKat]

TTT I have been following your progress and tons of fun with the BMS for the past few months, and though my entire Victron system was DIY.............................. I think I'll stick to lithiums with built in BMS's when the time comes and I can actually afford it.

But hats off to you for persisting during these "fun" times and even more so for sharing your school fees here with us.