Permobil M3 Corpus Battery Replacement Kit — Two 12V 75Ah Batteries

This kit replaces both batteries in the Permobil M3 Corpus and C400 VS Jr power wheelchairs: two matched 12V 75Ah high-rate sealed lead-acid batteries, backed by a one-year replacement warranty. They charge on standard 24V wheelchair chargers, including the charger your Permobil came with — no adapters, no reprogramming.

An M3 Corpus is a heavy chair doing real work: power seating, standing drivers, all-day duty. Its batteries fade the same way every wheelchair battery does — range shrinks first. The full day of errands becomes a half day, then a trip to the mailbox starts feeling like a gamble. That fade is cycle wear, and once one battery in the pair weakens, it holds the other back. A fresh matched pair restores the range the chair had when it was new.

Build features:

What this kit fits

Built as the replacement battery set for the Permobil M3 Corpus and the Permobil C400 VS Jr. At 10.2 × 6.61 × 8.43 inches per battery, it matches the original case size and drops into the battery compartment without modification. Running an F3, C300, or another Permobil model? Call 1-877-775-4381 and we’ll confirm the right kit before you order.

Why you replace both — and when you shouldn’t buy batteries at all

The M3 Corpus runs its two 12V batteries in series as one 24V system. Pair one new battery with one worn battery and the weak one sets the limit: the pair charges unevenly, the new battery works harder than it should, and you’re back shopping for batteries months early. That’s why this kit ships only as a matched pair.

And if your symptoms don’t sound like gradual range fade, hold off. A chair that dies suddenly, won’t take a charge at all, or lost power overnight may need a charger or a loose-connection check, not new batteries. Chargers fail more often than people expect. Call us and describe what the chair is doing — we’d rather tell you it’s your charger than sell you batteries you didn’t need.

About this kit

Each battery is 12V and 75Ah, sealed lead-acid with high-rate discharge plates and threaded-insert terminals, so the chair’s existing cables bolt straight on. Sealed, non-spillable construction means no watering, no acid handling, and no maintenance beyond charging — safe to run indoors and in vehicle lifts.

Each battery measures 10.2 × 6.61 × 8.43 inches including terminals and weighs 49.2 lbs, 98.4 lbs for the pair. This is a two-person lift, and it’s the reason we suggest lining up help or your local mobility shop before the boxes arrive.

With nightly charging and daily use, plan on 12 to 18 months of service before range starts to fade again. Lighter use stretches that further; the care habits below are what get you to the long end of the range.

How to install it

Plan on 30 to 45 minutes with a wrench and a second set of hands for the lifting.

1. Power the chair off and unplug the charger before opening the battery compartment.
2. Photograph the cable routing, then disconnect and lift out the old batteries — each one is about 49 lbs, so lift with your legs or use a helper.
3. Set the new batteries in place, match red to positive and black to negative, and snug the terminal bolts into the threaded inserts with a wrench. Loose terminals run hot; overtightening strips the insert.
4. Close the compartment and give the pair a full overnight charge before the first ride. Most auto parts stores take the old batteries for recycling at no charge.

How to make it last

Two habits drive wheelchair battery life: charge every night, even after a short day, and don’t run the pair to empty before plugging in. Store and charge the chair somewhere between 50 and 80°F when you can, and if it sits unused, top up the charge every two weeks so the batteries don’t drain flat in storage. When replacement time comes around again, replace both together.

Frequently asked questions

Not sure this is the right kit for your chair? Call 1-877-775-4381 with your Permobil model and we’ll confirm the fit before you order — we’d rather check twice than ship you 98 pounds of the wrong batteries.