I can seem to equip anything else except included batteries!
is this by design? if so can we have an option to equip other items to?

As in the below screenshot, the in-game hover info panel "Accepted equipment:" already shows all possible choices that can be installed. Unlisted ones (e.g., energy shields, personal roboports) cannot be put into the grid.

Let me refer to my FAQ:

Q: What are the changes to the early armours?
A: The two vanilla early armours (light armor and heavy armor) do not have any equipment grid. This mod add a small grid to them, so you can put in the primary batteries.

Q: Why I cannot put in energy shield (or other equipment) to heavy armor?
A: The newly-added small grid are supposed for the primary batteries only, not a substitute of advanced armours. Think of this as merely pockets of an armour vest, rather than an integral system of an advanced powered armour.
You still need to upgrade to at least a modular armour, to utilize the benefits of the whole equipment system.

So yes, it is intentional that the early armours cannot use things like energy shields or exoskeletons.
Otherwise it is too cheaty for an armour vest to have full function of a hi-tech powered armour. Keep it mind that light armor and heavy armor are much cheaper in ingredients and much earlier in tech tree, than the first proper modular armor!

thx for the explanation! :)

Can you permit to add the vanilla Night vision unit to the basic armors? This would explain the presence of the grid when Rechargeable weapons mod is not installed.
Or can you disable the grid, if Rechargeable weapons mod is not installed?

This mod has option "Enable grid to early armours". You can set it to whatever you like.

My fault, thank you
BTW, I found out a funny feature, that "Induction charging" mod recharges the batteries %) I have reported it

Thank you.
Haha, I guess the other mod authors will wonder why someone will LIMIT the charging ability like this.

Well, it seems that "Induction charging" mod is no longer maintained. Could you add some workaround for the IC mod into your mod? I expect that won't be easy, though.
I tried to replace IC with some other mod. But, suddenly, it turned out that IC is the only mod that acceptably allows charging armor from the power network. Other mods either crash or cause lag spikes. Also, IC is a fairly popular mod, so its adaptation won't be a useless job.

"Induction charging" (IC) is not an ordinary mod, but a mod relying HEAVILY on scripting in control.lua and all its library script in lua folder.
Whatever "adaptation" could ONLY be done by updating its control.lua and library in its lua folder, not any code from external mod can change that (at least I do not know how to do cross-mod scripting, something I never heard).

Too bad if IC mod author is no longer active. Because there are only three choices actually:
1. An update to IC its author.
2. Someone fork from IC, then modify whatever. (IC is using MIT license, everyone can do that in theory.)
3. Someone take over IC, then release as a new IC mod. (Fairly common for abandoned but popular old mods.)

You may need to wait as solution 1. Or you can ask someone else as solution 2 or 3.
But that would NOT be me. I can & will do light scripting (like my "Schall Gun Pod") at max.
Mods with heavy scripting are very time-consuming and hard to maintain. I do not have any time nor patience in doing that.

Okay, we've alreay found out, that I am stupid. I still cannot manage to put a Night vision unit into early armor.

I have "Enable grid to early armours" enabled (in addition to Equipment grids mod). I tried both modes. I see the grid. But it says only batteries and induction coils can be placed into those grids. What am I doing wrong?

My previous comment was to be meant: you can disable those grids with "Enable grid to early armours" option.

I don't want to allow Night vision equipment to be usable to early armours. Otherwise, I would expect other players start to ask why Night vision is exclusively allowed, but not shield (or any other type of equipment)...

Eh.. okay.. I guess there's no use of this mod for me yet =(
BTW, the Induction charging mod crashes when trying to replace a battery. You might want to add incompatibility marker to your mod info.json.

Sorry, this mod is not intended for early use of modular equipment.

Ok, I will add incompatible marker next update.
The crash is probably due to IC mod relying on script to keep track of internal number of equipment. This means IC mod may crash with any other mods that insert/remove equipment.