Body battery always at 75 or lower in the morning

Low heart rate workouts

On the diet side: Limit or eliminate caffeine and alcohol before bed (4 or more hours give or take). Eating healthy/better portions at dinner time helps, a huge bowl of pasta before bedtime will have your body working hard as you sleep (and even during the day for that matter) therefore increasing heart rate and stress which reduces "recharge". 

No strenuous activities too close to bed time either. Getting in better shape will help this as well, as Fronius mentioned about low heart rate workouts. Some days will unavoidably be worse than others, but every now and then on a relaxed day when you do things right you should be able to get that up. 

Also, just as important as the number when you wake up is the total recharge during sleep. If you were at 5 when you slept, and woke up at 75, that is actually very good. If you were at 50 when you slept and woke up at 75, that is not good at all.

I find the greatest determinant of a good BB reading is low stress overnight. You can have a long sleep and a decent score, but if your stress level doesn't drop low enough, you'll have a hard time topping 90. BTW, how much Deep Sleep are you getting?

I agree on everything. I’ll add one more tip that works pretty much 100% of the times for me: lower the temperature while sleeping.

Every night I wake a little on the cold side my stress is lower than those mornings you feel a little sweating. There’s a ton of literature about sleeping on a cold(ish) environment.

My body battery is currently at 5?! and is generally below 50

Monday to Friday about max. 80. 7.5÷8h of sleep. At weekend without beer and going not too late to bed I get always 100. Beer is killer to me, even one beer brutally affect my sleep. Noticeably even without watches. Four beers give me 25 percent body battery in the morning and that's exactly how I feel...

Also late protein drink before going to sleep affect my sleep a lot. Higher HR, waking up. Same for every other food, obviously.

Intense movies or TV shows right before bed can raise my heart rate to over 120 and the stress continues throughout the night, leaving me with a low body battery.  

I found that having beers earlier helps because it allows your body time to process it before sleeping. 4 beers with the last one 3-4 hours before sleep will be much different than 4 beers with the last one an hour or so before you sleep. I have been able to get up to between 70-80 when doing so but it is not always possible.

somwhere around v 19.20 Garmin changed the algorithm, so it is not so easy anymore to get 100. Previously I got 100 even with short sleep, and now even 8h of sleep doesn't get you from 5 to 100 during one night.