I guess you’re using Bob's Vehicle Equipment mod? It would be great if that mod added its equipment grids to all modded locomotives that don’t have one yet, but alas, it doesn’t.
I added support for the three tiers of locomotive grids from that mod, but I don’t use any of Bob’s mods. It would be nice if you could test it for me: Download the experimental version from [link expired] and replace BatteryElectricTrain_1.1.3.zip in Factorio’s mod folder with it. Afterwards, you should have a mod setting to choose which grid to use for battery-electric locomotives.
Please tell me if it works as you expect it to or if there are any bugs.
Also, do you think the setting is pointless because everyone will set it to tier 3 anyway? I only added it because I don’t know what’s the point of the different tiers. If you think it’s pointless, I can remove the setting and just use tier 3 all the time.
If everything works, I’ll release it as version 1.1.4 and you won’t have to worry about losing your equipment grids after an update.