12 V Battery dragging off

Hello everybody,

Here’s my question, How does the service battery recharges? In a petrol car the 12V is used for the starting motor to turn the inertia wheel while igniting for the first time, then after the alternator recharges the 12V while the engine is running.
My thinking is a similar way, the 12V battery is used to run the SCR to connect the power battery, while the power battery 57V is running it recharges the 12 V, on it on while the batteries last. Am I thinking it the right way?

This is my issue, I connected a fancy equalizer, this equalizer drags a little bit of current while it’s turned off to keep the memory going . This little bit of current drags my 12 V . Since this happens once every 36 hrs I think if I turn on the key switch daily it will recharge the 12V while the key is on.

My solution, I’m thinking to install in parallel a huge audio capaitor to store the energy while the key swith is off, however from what I’ve seen 6 farads is not enough, neither 21 farads, I’m looking for bigger capacitor however I’m hesitating, maybe my way of thinking is not so right, can you both give me your comments?


How old is your Twizy? The early charges only charged the 12V batter while the main battery was being charged or when the ignition was on (as you said).
The MKII charger keeps the 12V battery topped up from the traction battery every few minutes.

I replaced my 12V battery with one of these last year. (brought it from china direct online)

It can still go flat after extended periods of no use , mines a 2012 Twizy , but i keep a small smart charger attached to keep everything topped up.


Osbrook My twizy is from 2015,

M1n1s, i calculated some interesting numbers I believe your capacitor module is connected in parallel (in order to handle 12.5 VDC) meaning you have a huge capacitor of 3000F, your bank can store 234 Kilojoules, the 14 AH Twizy OEM Battery handling the same voltage can store 630 Kilojoules, from this I can infer 3 banks can replace the battery withou loosing capacity, I am seriously thinking on buying 3 banks to have a long life Energy source. Can you advice how it performs, while I attended the college the expected behavior from RC (resistance+capacitor) circuit would have a decreasing voltage curve, the load is an important thing to consider , if your load is low you can go on it on for many hours, have you counted the time your module lasts when the key switch is off?
On another subject, I considered a Kwhunter suggestion to install kill swith for the battery not to drain off. it’s not the most fancy way to solve it, however it works.

Saludos and Keep healthy

I did consider fitting more banks of capacitors but space up front is a consideration.

With the capacitor battery fitted I haven’t noticed any different to a standard battery , however with the Twizy electrics connected the battery will go flat in a month so I keep my trickle charger fitted all the time, a battery isolator switch would be an idea to stop the discharge.

The advantage of the capacitor battery is weight , price and no acid in the case of a front impact crash, also the capacitor won’t age like a normal battery needing replacement every few years.

Kill switch and bigger battery…2 options: you have to modify the battery support or use a long additional battery in the object compartment under the passager seat…you won’t have troubles with the charging sistem…it will only take longer to get to 100%…you can also install a voltage display in the glove compartment…that way every time you turn on the key you can see the state of the battery/batteries