My battery analyzer is based on this cheap chinese coulometer:

https://www.ebay.com/itm/DC8-80V-50A...-/252470874308

I use small car light bulb (10-20W) as a load.

I connect the thing between charger and batter or load and battery. That way I can measure capacity both ways. It is also super easy to discharge battery to optimum state for winter storage.

I like it so much I seriously thought about putting it my glider panel. If it only would support 2 or 3 batteries.