WFCO WF-9855 Charger Not Going Into Bulk Charge Mode - Replacement Options In Keystone Toy Hauler?

Published 02/23/2026

Question:

My WFCO WF-9855 won’t go into bulk mode. Would replacing it with the WF38FR fix that for my Keystone toy hauler? thanks

asked by: Josh

Expert Reply:

Hey Josh - if your older WF-9855 isn’t entering bulk mode and you’ve already ruled out wiring issues and battery problems, replacing it with the newer # WF38FR (WF-9855-AD-CB) is definitely a solid move.

I mentioned solar because even a small amount of solar input can keep the batteries “topped up” just enough that the converter never sees them as low. Bulk mode (the high-amperage charge mode) only kicks in when the converter detects a sufficiently discharged battery. If the batteries never drop low enough, you won’t see that 14.4V boost.

The newer # WF38FR uses WFCO’s Auto-Detect charging logic and will boost to 14.4V for lead-acid or 14.6V for lithium during Charge Mode. It’s still rated at 55 amps, just like your original unit, so in most cases you won’t need to change wiring as long as your battery cables are in good condition and properly sized.

Before replacing it, I’d recommend disconnecting solar and testing again to confirm it truly won’t enter bulk mode. That way you know you’re not chasing a charging-profile issue caused by outside factors.

What battery type are you running right now?

expert reply by: Andrew N