Weak car battery: leaving a lithium booster connected to it all the time?

[Christophe]

It's all in the title: in the event of a car battery that is starting to run out of power, is it possible to leave a battery booster permanently connected (with self-charging so when the car is driving)? That is to say that it will permanently boost the battery rather than changing it preventively...

With the old lead battery boosters, the question did not arise (except that of the current charge via the cables of the booster) but all the current boosters on the market are with internal lithium batteries...

So mixing batteries of different technologies all the time, I'm not sure it's a good idea and the recent boosters are electronically regulated... (standby for example...)

The charging of these new boosters, if it is not possible via the boost cables, is done via 5V USB sockets... so if the first problem is resolved it would be possible to make a USB charging loop via the 12V ...no worries with that.

So, has anyone tried it yet?

ps: there are also battery "booster" kits based on super capacitors...someone has tested this too? Here is one https://www.amazon.fr/Ticfox-ensemble-condensateur-%C3%A9lectrolytique-ultracondensateur/dp/B09J8XHVN4/ When I look at the comments, it is mainly used for solar installations and not on cars...

[phil59]

A low battery eventually fails.

I have already had the trick that a battery with the cables prevents starting because it is in short juice.

The alternator charges the battery, so normally it does not need to be boosted at this time, if it is doing its job.

If the booster stays plugged in at night on a battery at the end of its life, won't it run the risk of also discharging at night to maintain the battery?

[Remundo]

if it is a booster charger which embeds its own battery,

yes it will of course help to start.

But it's a short-term solution.

If the car's main 12V battery fails, it will constantly draw on the booster battery, or even damage it.

Note that sometimes the main batteries are weak because there is a problem with the alternator (voltage delivered too low).

A correct alternator should deliver 14V with the engine running, but no more than 15.

So I would rather recommend checking the alternator and not insisting on end-of-life batteries.

Some of the batteries at the end of their life have a short-circuited element and deliver 10V instead of 12, for example. It is imperative to turn them there.