Every decision involves a trade off of "perfection" vs "it works well enough" or at least "better than before".
The cars with regenerative capability sometimes capture this energy not from the braking, but from the inertia of the engine, alternator, and other items on the drive belt.
When there is heavy demand on the engine, some of them will turn off things like the alternator and air conditioner compressor to free engine power for moving the car better.
At normal constant speeds, they will operate things reasonably normally.
When the brake is pressed, some of them use the rotation inertia of the engine belt drive components to push a large amount of power into the battery pack (by working the alternator very hard).
If a car is sitting still for a long time (weeks) the starting battery can self discharge enough to ruin it.
All of these things are very hard on a battery, and the more often they happen, the worse the effect. Sometimes it is so hard on the battery, that 2 or 3 batteries are used and assigned different functions. I have helped a customer with a project that had 3 batteries from the original car company and we added 4 more for auxiliary functions. The pressure on car manufacturing companies is very intense, so they are forced to reach deeply into the engineering bag of tricks to obtain even small fuel efficiency gains.
In a perfect world, a battery is full charged perfectly, used in a moderate manner, and then recharged fully and not subject in any way to abuse.
In the real world, modern cars abuse batteries much worse than this so it is a matter of being "not as bad as it could be" rather than "perfection."
Small solar panels ~ 5-10 watts can be quite effective at helping to deal with natural battery self discharge challenges. (example power film). If combined with a small solar charge controller, even better. Usually 5-10 watts of solar is not a problem even without a solar charge controller, as the vehicle electronics have some parasitic losses. The times that we are going through now with much less driving of our cars is a good example of a need to do "something" to keep the car batteries from going bad just from sitting there.
1000 watts is in the same range as making coffee, so not a super large amount of power, but more than many are used to paying for. ($300-400)
cTek is a perfectly good product offering. If you live in an area where the temperatures go both fairly hot and fairly cold, it is worth to verify that the charger has a way to deal with this temperature range.
Batteries are an electrochemical device. The charging process is a chemical reaction, and the charging "energy" comes from both "Temperature" and "voltage". If the temperature is low, then the voltage must increase in order to (perfectly) charge. The more ideal chargers have this temperature compensation built into them. If not, then you just accept that what you are doing is better than doing nothing at all - which is still better than it could be.
