B2B in parallel?

[Tarn2]

I’m about to change to 2x100ah lithium batteries instead of my current LA ones. It’s been suggested that it would be better to add another charger in parallel to the existing Ablemail 12-13-30 I’ve already been using. The plan is 16mm input cable from starter battery (about 2m away) via 50a fuse. Can I connect the Input to Input, OV to OV and Output to Output and then just one of the Outputs to my fuse board before going to my lithiums (currently via 100a midi fuse), or do I need to connect both Outputs together via a connecting block/ busbar , then onto the fuse board? Hope this makes sense and thanks in advance!

 

[Speve]

Your picture is not very clear and probably better if more detail of your system shown to help folk advise you

 

[autorouter]

If the B2B is the Ablemail AMC 12-12-30, then they say in the manual:
"Two or more Battery Chargers can be used in parallel to allow more current flow to the recipient battery."

I think either method will be OK, if the wire from the output to the battery is OK for the extra current, 60 amps in total. That will depend on the wire thickness and length. You can calculate the voltage drop along the wire using a voltage drop calculator like this one.

Voltage Drop Calculator | 12 Volt Planet

Use our Voltage Drop Calculator to select the correct Cable for your campervan, motorhome or boat wiring application. Auto and Marine Electrical Components from 12 Volt Planet - Cable Size Calculator

www.12voltplanet.co.uk

You should keep the voltage drop to below 3%. For 16mm² cable, up to about 2 metres is OK.

If you run sense wires from the B2B to the battery, the B2B will compensate for the voltage drop, boosting the voltage so that the voltage at the battery is correct. You'll need to run sense wires from both B2Bs to the battery.