New Project. Smart Aux Battery

twizylover schrieb:
To be honest, you are the first person in the world that said that about Twizy...

I have 11,x kWh. That is really OK for me

If you talk to a Twizy owner with a 13 year old 55% battery, he will surely tell you an other story

Interessantes Projekt... Viel Erfolg damit

Aber, als mein 12v "Lader" defekt war, war nicht nur das laden ein Problem.
Alle 12v Verbraucher waren beeinflusst, Licht dunkler, Scheibenwischer langsam...
Ja fahren war möglich aber nur mehr wirklich sicher außer bei Sonnenschein.

Und der fix war simple, mit etwas, Elektronik wissen. Wie lang das hält weiss ich zwar nicht aber mal schauen.

Hallo zusammen, ich kann mich endlich schon mit meinem Ladegerät rühmen, welches noch der einzige Prototyp ist, aber schon die Hälfte der Funktionen ist
Mit ihm startet und fährt der twizy ohne Probleme und lädt und lädt auch eine 12V Batterie, der maximale dcdc Strom liegt bei ca. 30-35A
Bisher wurde nur die n-Version hergestelltBisher wurde nur eine Version auf 4kw Und geplant sind 8kv und ein Typ2-Anschluss
Ja, in der Tat bleibt es mir, alle möglichen Fehler, die bei der Drehung verursacht werden können, zu verarbeiten und das Ladegerät auf diese Fehler zu reagieren, und ich bin noch auf der Suche nach einem Airbagmodul, in dem der Unfall aufgezeichnet wird

Update November 5th, 2025;

After some research and your comments, we decided to divide design into two models:

- Standard. Around 30 - 50Ah (final LFP cell selection comes soon to set the final capacity). More than 3x OEM capacity. Around 1kg less than OEM Battery.
- High capacity. Doubles Standard model capacity, doubles the price, doubles the weight.

So, we are focus only in the standard versión -the weight finally wins, assuming a 300% increase capacity from oem is more than enough-, keepin in mind the High Capacity version, but only for design purposes.

Thanks in advance for your support. Cheers.

P.S.: There is a new cool feature, the anti-thief solution can be used to power off 12V mains from the battery too, like a "Remote 12V battery disconnection", with no tools no front bumper removal... etc.

twizylover schrieb:
P.S.: There is a new cool feature, the anti-thief solution can be used to power off 12V mains from the battery too, like a Remote 12V battery disconnection", with no tools no front bumper removal... etc.

THAT is a really cool Idea. Not only for anti theft also for longer storing the Twizy.

A bit lighter then the original but 3x more capacity sounds quite good.

I am planning to build in a wireless Charger for my phone, and have a carplay monitor. If I could attach both to the mentioned USB ports - that would be not a bad idea. I was already thinking of using a LiPo battery to support those those devices (was also planning on charging that via 230Volt somehow), but could not think of a good place to store it.

Plus the additional features …

So I am in.

Update November 10th, 2025;

Battery cells selected!!

Finally, after a lot of headaches and compatibility tests, we have choosen the EVE C40 the cell of our project.

For us has the best ratio of price | size | capacity | cycles for this project.

With this cell of 20Ah and 4000 cycles LiFePO4 you can select 3 configurations:

A - Base config, Four cells and all the digital features. Nearly the double of the stock battery capacity 20Ah with 2.5 kg less aprox in weight than oem battery.
B - Standard config. Eight cells. 40Ah with 1.2 kg less aprox than oem.
C - High Capacity config. Twelve cells. 60ah. with 400g more aprox than oem.

Note: Final weights with the first prototypes. Only for reference for now.

We are focus on model A, and the users will can upgrade in the future to eight or twelve cells. Up to you. With the base model you have the case and electronics for all the models.

Cells we discarded:

- EVE C30. Apparently very good on our initial tests, but only 2000 cycles.
- EVE LF22K, Runner up. No option for high capacity version.
- Lishen LP27148134. Very low availability. Selled a grade B versión with 2000?? cycles instead 6000 original cycles. No option for high capacity version.
- Other cilindrical stardard size cells, because increasing price, weight and bms complexity for the same capacity with bigger cells.

Any idea about the estimate pricing for model A?

Snorre schrieb: Any idea about the estimate pricing for model A?

Today its very soon for price estimation, but our target its about 100 - 150€ for the Model A. With more than 4000 cycles its 10x more lifespan than oem and any AGM battery. Anyway, the final price will be available soon, molds of the case, electronics, man hours... but we'll try to get the lower price possible for you, our super target price will be 100€.. will see in the near future how close we can reach.

Hello twizylover and welcome to the forum.
I have been following your project with great interest and am eager to see the first results.
Even though you have already written a few posts, perhaps you would like to introduce yourself/yourselfs briefly under Wer und Wo , as described in our forum rules ? This helps us all to get a little closer together and understand each other better, thank you very much!

Hallo twizylover und herzlich willkommen im Forum.
Ich verfolge schon ganz fasziniert euer Projekt und bin gespannt auf die ersten Ergebnisse. Auch wenn du schon einige Beiträge verfasst hast, vielleicht magst du dich/euch bitte trotzdem unter Wer und Wo kurz vorstellen, wie in unseren Forenregeln beschrieben? Das hilft uns allen ein bisschen näher zusammenzurücken und den anderen besser zu verstehen, vielen Dank!

twizylover schrieb:

Snorre schrieb: Any idea about the estimate pricing for model A?

Today its very soon for price estimation, but our target its about 100 - 150€ for the Model A. With more than 4000 cycles its 10x more lifespan than oem and any AGM battery. Anyway, the final price will be available soon, molds of the case, electronics, man hours... but we'll try to get the lower price possible for you, our super target price will be 100€.. will see in the near future how close we can reach.

Hey twizylover.

Your posts sound a bit like a Kickstarter blog

For me replacing the AUX battery really does not make sense to me.
The lead acid is a KISS (keep it stupid simple) system that really does not need replacement, does it?
Its cheep robust and as a recycling system already established.

As I understand it, the battery also stabilizes the 12V circuit in the twizy and so takes some load off the DC/DC.

I actually tried to replace the Lead acid one , which just ended with failure of the BMS (being stuck at the place I was then) in the LiPo battery and my money back.
But even if you have the best BMS in you Lithium cells you do not know have the charger will wear after a year or so.
And this part is the more expensive one to replace.

Also ,please keep in mind that by the forum rules commercial offers or even offering project results for money have to be approved by the moderator staff.
So please refrain from starting any order list for now.

Großstadtfahrer schrieb:
Hey twizylover.

Your posts sound a bit like a Kickstarter blog

For me replacing the AUX battery really does not make sense to me.
The lead acid is a KISS (keep it stupid simple) system that really does not need replacement, does it?
Its cheep robust and as a recycling system already established.

As I understand it, the battery also stabilizes the 12V circuit in the twizy and so takes some load off the DC/DC.

I actually tried to replace the Lead acid one , which just ended with failure of the BMS (being stuck at the place I was then) in the LiPo battery and my money back.
But even if you have the best BMS in you Lithium cells you do not know have the charger will wear after a year or so.
And this part is the more expensive one to replace.

Also ,please keep in mind that by the forum rules commercial offers or even offering project results for money have to be approved by the moderator staff.
So please refrain from starting any order list for now.

First of all, no worries about order list in the forum without been approved. We are not planning any order list at the moment, anyway we are only trying to get to life this device, as my posts try to explain, we are at the beginning of this project, in the design and test stage. And we hope that our findings will be useful for other people on this forum. Probably we publish all work open source,.. is very soon to talk about that, the BMS for example, its giving us a lot of work because we don't want to use MCUs like esp32 on primary tasks or hobby/maker electronics like arduino, that is not automotive ready, like ASIL-C/D or AEC-Q100, perhaps for that reason you stuck... Anyway, when we arrive there (if we can), will talk about.

More in consideration about our project:

1. Case, if we share the 3D model anyone could mmm, print it, or even make your own mods on the case model. Connectors and o-rings will be OEM or stardard.
2. Cells. you can buy on your own the cells.
3. BMS and other electronics. Perhaps for this item will be the an order list.
4. Firmware. We will try open source.
5. Tools, tapes, glues, and all the other needed items are worldwide available.

Secondly, you are talking about DC/DC load for rectification of signal. That's not correct in our use case.

And last, I'm sorry if my posts don't suit your taste or if they sound like a Kickstarter blog.

Thanks in advance for your support.

I can give you a proven fully discrete BMS HW solution, scalable from 1S up to 16S. No special chip. Also got some previous work on a 16S BMS for the twizy with Bluetooth chip, work was discontinued because Rhozkov did release his BMS. Get in touch if I can help.

Großstadtfahrer schrieb:
But even if you have the best BMS in you Lithium cells you do not know have the charger will wear after a year or so.
And this part is the more expensive one to replace.

Important note here, in our design the new aux battery don't use the DC-DC part of the "elipshit" 2000w charger. It charges when you plug your twizy to the AC charger, with his own high availability rectifier. The Elips charger has a lot of flaws and design SPF errors that obviusly we want to avoid. For that reason our solution has no wear at all on the original charger. And remember, with 40Ah you don't need to worry about 12V circuit anymore on this vehicle even with a lot of 12V gadgets..

We know that twizy oem charger is one of the biggest SPFs, because if the charger doesn't work, you can forget about your twizy, no replacement parts... etc, only preventive maintenance -lacquing circuit board... etc- is only available for those who still have his charger in perfect condition today. If we are able to carry out this project, our next goal will be able to charge to the maximum in AC mode with high quality rectifiers of automotive quality -22kW AC in three-phase or 7.3kW in single-phase mode-. , So if your oem charger dead you always could have a replacement a few times better than original french design.

Thanks.in advance for your support.

@twizylover
I am trying to understand your project. My thoughts on it.

The Twizy has two energy storage devices. The drive battery 11000Wh (new cells) and the auxiliary battery AGM with 12V x 14ah = 168Wh. So 98.5% of the energy is distributed in the drive battery and 1.5% in the auxiliary battery.

Now you want to increase the size of the auxiliary battery,for example, 12V x 40Ah = 480Wh. This would allow the Twizy to carry approx. 300Wh more energy. With the Twizy's consumption of 11,000Wh/100km, that is 110Wh per km.
The additional range would therefore theoretically be a maximum of approx. 2-3 km.
Is it worth it?

It is true that the AGM battery wears out quickly. However, there are replacements available, e.g. sodium batteries (from Hakadi), which are resistant to low temperatures, have a high cycle count and are inexpensive at 40€.
Is the conversion you are considering worth it?

—————-

ich versuche euer projekt zu verstehen.
Meine Gedanken dazu.

Der Twizy hat zwei Energiespeicher. Die Fahrbatterie 11000Wh (neue Zellen) und die Hilfs batterie AGM mit 12V x 14ah = 168Wh.
Die Energie ist also verteilt zu 98,5% im Fahrakku und 1,5 % im Hilfsakku.
Nun möchtet Ihr die Hilfsbatterie vergrößern
Auf z.B 12V x 40Ah = 480Wh. Damit kann der Twizy ca 300Wh mehr Energie mitnehmen.

Bei einem Verbrauch des Twizy von 11000Wh/100km sind das 110Wh pro Km.
Die zusätzliche Reichweite wäre damit theoretisch maximal ca. 2-3 Km.
Lohnt sich das ?

Die AGM Batterie verschleißt schnell das ist richtig. Dafür gibt es aber Ersatz z.B Sodium Akku ( von Hakadi ) der ist Tiefsttemperaturbeständig und hat hohe Zyklenzahl und ist billig 40,-€
Lohnt sich der Umbau den Ihr euch überlegt ?