How to synchronize two inserters?

[Redvii]

I thought this would be much more straight forward, but after looking online and doing some experiments with circuit networks, I can't figure out how to synchronize two smart inserters as strictly as I'd like.

Here's the deal:
-Smart_Inserter_1 is staring at a looped transport belt and trying to feed an Assembly Machine with Batteries.
-Smart_Inserter_2 is positioned in between where all my Batteries are produced and the transport belt that feeds Smart_Inserter_1.

Any time Smart_Inserter_1 takes a number of Batteries off the transport belt loop, I want Smart_Inserter_2 to add that exact number of Batteries back on.
If Smart_Inserter_2 has to wait to receive the Batteries from a slow factory, I want it to remember exactly how many Batteries Smart_Inserter_1 has taken in the meantime.

I figure this problem has been encountered and solved by more experienced players than me - so I'd appreciate any help and can provide mroe details if necessary.

[Redvii]

Here's a picture of the type of factory I'm trying to create.

*The Iron Plates are just stand-ins for the real Blue Science ingredients that would be in circulation.
*The reason for the inserter synchronization is to avoid clogging the transport belt with only one type of item.

[onebit]

You can do it with smart chests and circuit conditions.

Belt -> Smart Inserter A1 -> Smart Chest -> Smart Inserter A2 -> Belt Loop
Belt -> Smart Inserter B1 -> Smart Chest -> Smart Inserter B2 -> Assembler

Wire the smart inserters and smart chests together with red or green wire, both on the same network.

Program the circuit network conditions like this:

• A1: If battery = 0 (pickup 1st battery)
• B1: If Battery = 1 (pickup 2nd battery)
• A2/B2: If battery = 2 (unload batteries)

If there are no batteries in any box A1 will pickup a battery and put it in it's box.

Now that there is a battery in a box, B1 will pickup a battery and put it in it's box.

Now that each box has a battery (2 batteries total), the boxes are unloaded.

Make sure A1/B1 only pick up from belts so they get 1 item. Inserter stack bonuses make it very complicated.

This has a chicken in the egg problem. To start it working you must put a battery in both boxes.

[roy7]

An alternate approach to do what you want is a passive logistical loop. I am on my phone so I can't link you posts, but if you search reddit I posted a number of examples there. Maybe one on forums.

Edit: https://www.reddit.com/r/factorio/comme ... 2_example/

[Porter65]

That was I routinely do also, inserter A adds something at a given speed (a speed high enough to satisfy the assembly machines on the looped belt) and inserter B (or inserters if you have several A) can pull out all that the A's can add. It can be nothing if the assembly are working at full speed, or it can be everything if they are not working. This way, no clog up.