Monitoring lithium batteries

[Johny London]

I didn't expect it to do the whole damn lot! But it could be another piece in the puzzle, what with an arduino alternator regulator, setting the correct voltages on all the charging sources AND adding ov/uv protections. The problem with the later seems to me to be not so much finding a device that can monitor for ov/uv and send a signal, but getting a big enough relay.

 

How does this cheapo meter differ from / compare to a Victron one? Say a BMV 712?

Edited December 19, 2018 by Johny London

[nicknorman]

4 hours ago, Johny London said:

How does this cheapo meter differ from / compare to a Victron one? Say a BMV 712?

LED vs LCD (so it will use more current doing nothing). Case quality, electronics build quality, cleverness (no mention of CEF for instance, although of course for Lithium CEF is close to 100%) or tail current /how it resets to 100% (although again maybe less relevant for Lithiums)

 

With these sort of things it is pot luck. Maybe it will be fine. Maybe it will blow up in which case good luck with a warranty replacement! Maybe it will blow up again and so after you have wasted £50 for 2 you will end up buying a BMV (buy cheap buy twice etc). On the other hand, it may turn out to be fine. Your call!

[peterboat]

On 12/12/2018 at 17:17, Mike the Boilerman said:

And here is what’s under the lid of my box. 

 

Rather weird once you look properly...

 

 

Looks ok mike should do the job nicely for many many years

[Dr Bob]

9 hours ago, nicknorman said:

LED vs LCD (so it will use more current doing nothing). Case quality, electronics build quality, cleverness (no mention of CEF for instance, although of course for Lithium CEF is close to 100%) or tail current /how it resets to 100% (although again maybe less relevant for Lithiums)

 

With these sort of things it is pot luck. Maybe it will be fine. Maybe it will blow up in which case good luck with a warranty replacement! Maybe it will blow up again and so after you have wasted £50 for 2 you will end up buying a BMV (buy cheap buy twice etc). On the other hand, it may turn out to be fine. Your call!

Spot on.

The BMV will be fit and forget. I paid the money to forget about it. I am in the process of wiring up the BMV so that I can monitor it remotely. Straightforward to do with the BMV. More faffing with a cheap one. I'm too old for faffing.

[Detling]

The bmv needs programming correctly so it shows real amp hours and not corrected for peukert also it will need programming to the correct CEF of 99.9% so amp hours in are real amp hours. The cheapo doesn't have these unnecessary bits in it., (unnecessary for lithium) so is plug and play, but it won't show if you overcharge. It counts down from when you tell it the batteries are full and counts back up until 0 then it stops counting up.

[nicknorman]

7 minutes ago, Detling said:

The bmv needs programming correctly so it shows real amp hours and not corrected for peukert also it will need programming to the correct CEF of 99.9% so amp hours in are real amp hours. The cheapo doesn't have these unnecessary bits in it., (unnecessary for lithium) so is plug and play, but it won't show if you overcharge. It counts down from when you tell it the batteries are full and counts back up until 0 then it stops counting up.

A BMV doesn’t correct AH for peukert since that would be a nonsense. It does correct incoming AH for CEF but since the later ones auto-calculate CEF it probably doesn’t need setting, unless you are proposing to rarely or never reach 100% SoC, in which case best to set it to 100% to start with (if you can?).

[cuthound]

6 minutes ago, Detling said:

The bmv needs programming correctly so it shows real amp hours and not corrected for peukert also it will need programming to the correct CEF of 99.9% so amp hours in are real amp hours. The cheapo doesn't have these unnecessary bits in it., (unnecessary for lithium) so is plug and play, but it won't show if you overcharge. It counts down from when you tell it the batteries are full and counts back up until 0 then it stops counting up.

 

Lithium Ion batteries have a charging efficiency of 99% according to The Battery University https://batteryuniversity.com/learn/article/comparing_the_battery_with_other_power_sources, so using this monitor will encourage users to "fail safe" by undercharging. Fortunately this will not damage Li-ons, as it would lead acids.

[nicknorman]

8 minutes ago, cuthound said:

 

Lithium Ion batteries have a charging efficiency of 99% according to The Battery University https://batteryuniversity.com/learn/article/comparing_the_battery_with_other_power_sources, so using this monitor will encourage users to "fail safe" by undercharging. Fortunately this will not damage Li-ons, as it would lead acids.

Browsing, came upon this, mildly interesting.

 

https://elithion.com/pdf/ElithionBatteryPower10.pdf

[cuthound]

9 minutes ago, nicknorman said:

Browsing, came upon this, mildly interesting.

 

https://elithion.com/pdf/ElithionBatteryPower10.pdf

 

As you say interesting. However if charging efficiency is 100% as Elithion claim, then why do the batteries get warm as they charge?

 

It's a pity there are no explanations to their assertions.

[peterboat]

12 minutes ago, nicknorman said:

Browsing, came upon this, mildly interesting.

 

https://elithion.com/pdf/ElithionBatteryPower10.pdf

Glad I have LifePo4s that fire thing sounded scary!! I have a video somewhere of a Tesla pack that caught fire and it had a BMS but no thermal management which is a big no no

[nicknorman]

1 hour ago, cuthound said:

 

As you say interesting. However if charging efficiency is 100% as Elithion claim, then why do the batteries get warm as they charge?

 

It's a pity there are no explanations to their assertions.

Hmmm, didn’t you have a career in electrical stuff? CEF is the efficiency of charge. Charge is of course the integral of current. It does not have dimensions of power or energy (and hence not of heat).

Simplistically the number of electrons taken out compared to the number needed to be put back in. 

 

With Lithium, electrons don’t leak out anywhere. You take out x electrons, you need to put the same number back again. With a lead acid battery you need to put more back in because some of them get used up turning water into hydrogen and oxygen which is lost. There is no electrolysis of the electrolyte with Lithiums (hopefully), hence nowhere for any additional electrons to go.

 

The battery gets warm because the power efficiency is less than 100%. But that is not the same thing as charge efficiency. Different dimensions. Same charge in and out, less voltage out than voltage in. This is mentioned in the doc I linked to.

Edited December 20, 2018 by nicknorman

[Detling]

2 hours ago, nicknorman said:

A BMV doesn’t correct AH for peukert since that would be a nonsense. It does correct incoming AH for CEF but since the later ones auto-calculate CEF it probably doesn’t need setting, unless you are proposing to rarely or never reach 100% SoC, in which case best to set it to 100% to start with (if you can?).

please tell me what parameter 5 does then 

from my manual

05 "Peukert exponent it is recommended to keep this value at 1.25 for lead acid batteries and 1.05 for Li-ion batteries. A value of 1.00 disables the Peukert compensation."

 

 

[nicknorman]

36 minutes ago, Detling said:

please tell me what parameter 5 does then 

from my manual

05 "Peukert exponent it is recommended to keep this value at 1.25 for lead acid batteries and 1.05 for Li-ion batteries. A value of 1.00 disables the Peukert compensation."

 

 

Peukert exponent relates to when a battery reaches “flat” as defined by reaching a specified low voltage, typically 10.5v for a 12v lead acid. If current is drained faster, the battery reaches 10.5v having discharged fewer AH than it would have done if discharged slower. Primarily because the chemical reaction slows down and can’t keep up with discharge demand as the battery SoC falls low. Hard-to-reach chemicals deep in the plates can’t react fast enough.

 

However no AH have been lost - electrons don’t evaporate into the ether (quantum uncertainty excepted!). So eg a 400AH battery discharged at 200A for 1hr requires exactly the same amount of recharging as a battery discharged at 20A for 10 hrs - 200AH worth plus a bit for CEF (the same bit in each case). In both cases the same total AH can be extracted provided the fast discharging battery is allowed to rest and then discharged more slowly, so that the hard to reach chemicals can be given time to react

 

But if you want to know when a battery will reach “flat” - defined by the limiting low voltage - at the present discharge rate, you need to take into account Peukert. So yes Peukert is in the likes of BMV and Mastervolt AH counting gauges but it is only used in the “time to run to flat” display. It is not and shouldn’t be, taken into account for displaying AH in and out and SoC. Only CEF is relevant to that.

[Detling]

13 hours ago, nicknorman said:

Peukert exponent relates to when a battery reaches “flat” as defined by reaching a specified low voltage, typically 10.5v for a 12v lead acid. If current is drained faster, the battery reaches 10.5v having discharged fewer AH than it would have done if discharged slower. Primarily because the chemical reaction slows down and can’t keep up with discharge demand as the battery SoC falls low. Hard-to-reach chemicals deep in the plates can’t react fast enough.

 

However no AH have been lost - electrons don’t evaporate into the ether (quantum uncertainty excepted!). So eg a 400AH battery discharged at 200A for 1hr requires exactly the same amount of recharging as a battery discharged at 20A for 10 hrs - 200AH worth plus a bit for CEF (the same bit in each case). In both cases the same total AH can be extracted provided the fast discharging battery is allowed to rest and then discharged more slowly, so that the hard to reach chemicals can be given time to react

 

But if you want to know when a battery will reach “flat” - defined by the limiting low voltage - at the present discharge rate, you need to take into account Peukert. So yes Peukert is in the likes of BMV and Mastervolt AH counting gauges but it is only used in the “time to run to flat” display. It is not and shouldn’t be, taken into account for displaying AH in and out and SoC. Only CEF is relevant to that.

Thank you, I now understand another 1% of the mysteries of lead acid batteries, only 90% left but I doubt I will live that long.

[Iain_S]

18 hours ago, Detling said:

please tell me what parameter 5 does then 

from my manual

05 "Peukert exponent it is recommended to keep this value at 1.25 for lead acid batteries and 1.05 for Li-ion batteries. A value of 1.00 disables the Peukert compensation."

 

 

Not familiar with the BMV, but on our  Merlin Powergauge Lite, the "Peukert" parameter seems to be a measure of Charge Efficiency and nothing to do with Peukert, as I understand it.

[Cogito44]

Hello,
I think that the project that I realized will interest the world on this forum.

I designed the adapter VV250 which makes it possible to communicate a U-BMS Valence with a CCGX or Venus GX of Victron.
See the PDF and the video on my site:

http://cogito44.free.fr

YouTube

 

This adapter interprets and modifies the information circulating on the CAN network, so that it is understandable by Victron systems.
The advantage of using the information from the BMS of each battery is, a better accuracy, an individual measurement of each cell, more sensors and additional information especially at the level of defects.
This guarantees better safety and longer life for the batteries and for the devices that are connected.
In addition it is no longer mandatory to use a BMV, because all the information is in the BMS.

 

The system can be adapted according to the facilities of each.
Do not hesitate if you have questions.

 

 

FR :

Bonjour,

Je pense que le projet que j’ai réalisé va intéresser du monde sur ce forum.

J’ai conçu l’adaptateur VV250 qui permet de faire communiquer un U-BMS Valence avec un CCGX ou Venus GX de Victron.

Voir le PDF et la vidéo sur mon site :

http://cogito44.free.fr

YouTube

 

Cet adaptateur interprète et modifie les informations circulant sur le réseau CAN, pour qu’il soit compréhensible par les systèmes Victron.

L’avantage d’utiliser les informations provenant des BMS de chaque batterie sont, une meilleure précision, une mesure individuelle de chaque cellule, plus de capteurs et des informations supplémentaires surtout au niveau des défauts.

Ce qui garantit une meilleure sécurité et durée de vie pour les batteries et pour les appareils qui sont branchés.

De plus il n’est plus obligatoire d’utiliser un BMV, car toutes les infos sont dans le BMS.

 

Le système peut être adapté en fonction des installations de chacun.

Ne pas hésiter si vous avez des questions.

VV250 Cogito44.pdf

[frahkn]

Welcome to the forum.

 

I speak/read no French whatsoever but that did not prevent both parts of your post being equally intelligible to me.

Edited January 27, 2019 by frahkn

[Dr Bob]

52 minutes ago, frahkn said:

Welcome to the forum.

 

I speak/read no French whatsoever but that did not prevent both parts of your post being equally intelligible to me.

I think Cogito44 has a solution to the problem of Valance batteries communication with the victron venus gx box and BMS. This was discussed on a number of forums last year where Peterboat and others were asking questions about software/firmware and getting no response from Valance UK (or USA). It will not be much use to those on here who are looking for DIY systems (ie me!) and I think Peter has found a way round the communication issue by only charging to 13.8V (correct me if I am wrong Peter). Good to follow your posts on the EV vehicle forums last year!

I note that Cogito44 also posted today to the forums where the issue was discussed middle of last year with his solution.