I owe a big post about Andrei’s powerchair controls, Olga’s trip to Moldova, and all the work that went into that project! But as a quick note, I’ll just say we got the improved gear to Andrei!
Olga spent several days in his small town in the north western corner of Moldova, setting up the controls and testing various options for joystick, seating, and positioning. Andrei is now set up with a chin controlled joystick for the chair and I believe also for gaming.
Olga’s mom, and her mom’s boyfriend, also came along since they were in Moldova too. They were able to help out with some improvements to the ramp in and out of the house, and just to hang out, make friends, and make the celebration even nicer.
I want to tell this story in photos!
Olga leaving from San Francisco airport. Not shown: enormous rolling suitcase full of wheelchair modification stuff!
The very sturdy, custom built powerchairs at the airport in Istanbul! They don’t bother with manual chairs, I think, and have these absolute beasts of powerchairs. You can put bags on the back ledge or even stand on it. Olga was impressed I think.
Andrei in the chair, the first time they got the new chin control joystick working. You can read a lot into his smile.
Andrei and his dog Bobby hitting the open road. Honestly it still gives me chills because I think of the times I have had weeks or longer in bed or at home. Going out for the first time after that, the world seems so big and loud and vibrant, the colors amazing. everything is moving, the sky feels huge and I always have huge feelings about it. It can’t be taken for granted!!! I am glad the world is now at Andrei’s feet.
Olga, Maria (Andrei’s mom), Margarita (Olga’s mom) and Slava. Olga’s mom was in Moldova in the capital, visiting her boyfriend and they drove up to Andrei’s village to help out. The families became friends over the few days they were together working on the chair, and on some small modifications to the house!
A recent shot of Andrei in high visibility jacket, out with his dog riding in a specially rigged up backpack. I like the bright yellow!
Thank you everyone who contributed — We had so many donors giving what they could to make this happen! And especially, thanks to Levan, Bruce, and Rose from Easy Does It Services for all the hours of work they put in, Olga for all of her coordination, repair, testing, and the trip itself — with help, advice, and gear contributed as well from Vince from ILRCSF and Morgan, John, and Ash from the CIL.
Andrei is working on getting his Romanian citizenship confirmed and also — if you check our “Team” page — he is now working for GOAT as a consultant! He is a good sys admin/ IT person (which we need – I have no time!!) and so nice to hang out with (virtually, on telegram) and I’m also enjoying his posts on this blog — we’re all looking forward to more collaboration!
Minimalist infographic comparing traditional lead-acid wheelchair batteries with modern LiFePO4 lithium battery technology for power wheelchairs.
Choosing the right battery fundamentally changes the experience of using a power wheelchair. As the grassroots assistive tech community pushes for the Right to Repair and hardware independence, the shift from traditional lead-acid to custom lithium builds has become a topic of great interest. Most power wheelchairs operate on 24V systems, typically using two 12V batteries connected in series.
Why I Started Researching LiFePO4 Batteries
Last August I bought a used Permobil F5. The original lead-acid batteries were in very poor condition — they could barely move the chair for a few meters inside the house. Around the same time, several people I know had already switched to lithium. One of them had been running LiFePO4 for over four years, while another had installed it just a few months earlier. Both kept telling me the same thing: with a proper lithium setup, you can often charge the battery only once a week, or even once every two weeks, if you mostly use the chair indoors.
This information really motivated me. I started researching whether it was possible to install a LiFePO4 battery in a Permobil F5. It turned out that quite a few people had already done this conversion successfully. I even spoke on a forum with someone from the United Kingdom who had built his own lithium pack for the same model. He described the dramatically increased range he now gets on a single charge. He also powers his non-invasive ventilator directly from the same battery. In his build he used eight EVE 160Ah cells — this specific size was chosen because the battery compartment in the Permobil F5 has very limited height, so larger cells simply wouldn’t fit.
Most LiFePO4 users I’ve spoken with feel the same way — they believe lithium is the future. They all say that the downsides are more than offset by the freedom it provides. Being able to travel 25–35 miles on a single charge without having to charge the chair every day, and without constantly worrying about damaging the battery, makes a real difference in everyday life.
To better understand why lithium makes such a big difference compared to traditional batteries, let’s first look at the main battery types used in power wheelchairs today.
Common Battery Sizes and Typical Range in Power Wheelchairs
Most power wheelchairs use two 12V batteries connected in series to create a 24V system. Batteries come in several standard physical sizes (called “group sizes”). The most common ones are:
U1 (Group 22NF): Usually 30–55 Ah. Common in lighter and more portable wheelchairs.
Group 24: Typically 60–85 Ah. One of the most widely used sizes for standard adult power wheelchairs.
Group 27: Often 80–110 Ah. Used in heavier-duty and bariatric chairs.
Group 34: Less common, but found in some larger models.
Important note on usable capacity: With traditional AGM and GEL batteries, it is generally not recommended to discharge them below 50% if you want to maintain a reasonable lifespan. This means that from a 74Ah AGM or GEL battery you can realistically use only about 35–37Ah. LiFePO4 batteries can safely deliver 80–100% of their rated capacity, so a 74Ah LiFePO4 pack can provide roughly 60–74Ah of usable energy.
Real-world range depends on the user’s weight, terrain, speed, temperature, and driving style. As a general guideline:
Good quality AGM or GEL batteries usually deliver 10–18 miles (16–29 km) of range.
Well-built custom LiFePO4 packs typically achieve 18–32 miles (29–51 km) in real conditions, with some users reaching 35–40 miles under ideal circumstances.
Visual comparison of AGM, GEL, and OEM batteries commonly used in power wheelchairs and mobility devices.
Comparing the Main Battery Types
AGM (Absorbent Glass Mat) Batteries
This is the most common type. The electrolyte is absorbed in fiberglass mats. Popular examples include MK Battery in U1 and Group 24 sizes.
Pros: Good burst power, relatively low cost, provides natural ballast for stability. Cons: Significant voltage sag when discharging, short lifespan (1–1.5 years), sensitive to deep discharge.
GEL Batteries
Similar to AGM but with the electrolyte in silica gel. Often positioned as a premium lead-acid option (examples: MK Battery GEL, Sonnenschein).
Pros: Better cycle life than AGM, slightly more tolerant to deep discharge. Cons: Very sensitive to charging voltage, poor cold weather performance, higher price.
OEM (Factory Branded) Batteries
Batteries sold by wheelchair manufacturers (Permobil, Pride Mobility, Invacare etc.). In most cases these are rebranded AGM or GEL batteries.
Pros: Perfect physical fit, usually maintains warranty. Cons: Significantly more expensive (“brand tax”), sometimes include software locks (DRM).
LiFePO4 prismatic cells commonly used in custom lithium battery builds for power wheelchairs and mobility systems.
The Lithium Upgrade (LiFePO4)
Lithium Iron Phosphate (LiFePO4 or LFP) is one of the safest and most practical lithium battery chemistries available today. Unlike conventional lithium-ion batteries (such as NMC or NCA), LiFePO4 uses iron phosphate as the cathode material. This makes it significantly more thermally stable and much less prone to thermal runaway (fire or explosion) even if the battery is damaged, overcharged, or short-circuited.
Because of its safety characteristics and long cycle life, LiFePO4 has become the preferred chemistry for custom power wheelchair builds and is increasingly being offered as a factory option by some manufacturers (for example, Ottobock on the Juvo series and Pride Mobility on the Jazzy EVO 613Li).
What is a BMS?
BMS stands for Battery Management System. It is the electronic “brain” of a lithium battery. It constantly monitors voltage, temperature and current, protects the battery from overcharging, deep discharging, overheating and short circuits, and balances the individual cells so they work evenly. A good BMS is essential — without it a lithium battery can be damaged or become unsafe.
How a LiFePO4 battery is built
A typical 24V LiFePO4 battery for a power wheelchair consists of 8 prismatic cells connected in series (each cell has a nominal voltage of 3.2V). High-quality cells from manufacturers such as EVE or CATL are most commonly used. These cells are connected to a BMS, thick power cables, appropriate fuses or circuit breakers, and are securely mounted in the battery compartment.
Pros:
Comparable upfront cost with much better long-term economics: A quality LiFePO4 build with a good BMS usually costs about the same as a pair of premium GEL batteries, but lasts significantly longer (often 5–10 years).
Radical weight reduction: A well-built 24V LiFePO4 pack typically weighs 25–35 lbs (12–16 kg) instead of ~100 lbs (45 kg) for a lead-acid pair.
Flat power curve: The wheelchair maintains strong and consistent performance even at lower states of charge — there is almost no voltage sag.
Much higher usable capacity: You can safely use 80–100% of the rated capacity, compared to only ~50% with AGM/GEL batteries.
Cons:
Requires proper assembly: Needs correct calculations, heavy-gauge wiring, quality circuit breakers (100A+), proper fusing and good insulation.
Dedicated charger required: Standard lead-acid chargers will damage the BMS and cells. A lithium-specific charger is mandatory.
No gradual warning: Because there is almost no voltage sag, you get very little advance notice before the BMS cuts power.
Air travel restrictions: Lithium batteries are subject to strict IATA and airline regulations. Many carriers require advance notice, battery removal or special packaging.
The Problem with Off-the-Shelf Lithium Batteries
Buying cheap ready-made 12V LiFePO4 batteries (sold for RVs or solar, such as generic “100Ah RV batteries”) is a common mistake. Most budget batteries have weak BMS boards (often limited to 30–50A continuous discharge). Power wheelchair motors create very high current spikes on startup. A weak BMS interprets these spikes as a short circuit and instantly cuts power — leaving you stranded.
Commercially available batteries with sufficiently strong BMS boards are very expensive and often too large for standard wheelchair trays. For most users, a properly engineered custom build remains the only practical solution.
Important Safety and Usage Notes for LiFePO4 Builds
Check your current draw: Before choosing a BMS, determine the continuous and peak current consumption of your wheelchair’s motor controller. Many controllers can briefly pull 80–150A or more during acceleration and hill climbing. Select a BMS and circuit breakers with adequate headroom.
Discharge limit: Never discharge below 20–25% remaining capacity. Always keep a safety buffer — the BMS will cut power abruptly with no gradual slowdown.
Quality BMS: Use a BMS with over-current, short-circuit, temperature and cell-balancing protection.
Fusing: Always install appropriate circuit breakers or fuses (100A+ class recommended).
Secure mounting: The battery must be firmly fixed — wheelchairs experience significant vibration.
Professional help if needed: Improper assembly can damage the motor controller or create a fire hazard. If you lack experience with high-current DC systems, work with a knowledgeable technician.
The Hidden Trap of Losing Weight: Center of Gravity and Traction
One of the biggest advantages of a custom LiFePO4 build is the dramatic weight reduction. However, removing 60–80 lbs (27–36 kg) from the base changes the wheelchair’s physics:
Loss of traction: Drive wheels need downward pressure. Without the original ballast the chair can spin its wheels on smooth ramps or wet surfaces.
Higher center of gravity: This increases the risk of tipping, especially during quick acceleration or on slopes. Many users add bolt-on counterweights or adjust seat positioning to restore stability.
Conclusion: Making the Right Choice
Switching batteries is not just a component swap — it changes how your wheelchair feels and behaves.
If you want maximum simplicity and minimum hassle, high-quality AGM batteries (such as MK Battery) or premium GEL options remain the most straightforward traditional choice.
However, if you want to eliminate voltage sag, significantly reduce weight, increase range, and are willing to invest time or professional help into a proper build, a well-engineered custom LiFePO4 pack using quality cells (EVE, CATL, etc.) is usually the best long-term investment. The key is to approach the project responsibly — never compromise on BMS quality, always use proper fusing, respect the new physical dynamics of a lighter chair, and leave a safety buffer on every charge.
This article is for informational purposes only. Modifying batteries may affect warranty, safety certifications, and medical device compliance. Always consult with your wheelchair provider or a qualified technician before making any changes.
Great news! GOAT was awarded a Community Impact Grant from Ability Central! We are using this grant to expand our wheelchair maintenance workshops. Our April, May, and June Tune-Up Tuesdays are funded by the Ability Central grant!
At our workshops, around 10-15 people per event get a free inspection, a small portable toolkit to attach to their chair or carry in a backpack, and a worksheet to take with them with information about the chair. We look up service manuals so that wheelchair users can better understand how to prevent, troubleshoot, or fix small problems, and how to figure out what’s needed for more complex repairs.
The Independent Living Center SF and other Bay Area organizations, like the CIL and Easy Does it Services, collaborate with us as well as volunteers from the DCC staff and Streets Forward.
We believe that understanding maintenance helps keep people mobile, empowered, and engaged in their communities. We depend on our gear to get us around the house, out of the house, just to live our lives and have control over what we do. When our devices break, the path isn’t clear at all, and it isn’t easy even for people who bought their devices new and have insurance or warranty coverage. For people with secondhand, donated, or older equipment, the problem is even worse. What happens to everyone, I find, is that we end up in “loaner” or donated chairs, or an old half broken one we’ve had for years. That can mean pain or injury, and usually means serious limitations on what we can do. Life is on hold when we can’t get around!
Added to that problem, repair people with experience are rare. It’s as if there were no small bike shops, bike collectives, car repair shops, and you always had to go to “the dealer” for your fix. We’re hoping to change that, and bring some of our wheelchair user “customers” and our volunteers together in a way that leads people to develop a better and more robust ecosystem for repair and reuse! At our back, in California, we have right to repair legislation – including the Powerchair Repair Act from 2025 – defending our abilities to maintain and repair the tech that we own.
With Ability Central’s generous grant, we’ve bought supplies for many more free toolkits! We’re also able to contract time when needed to fabricate (often via 3D printing) small parts for modifications and enhancements.
Here’s our kit assembly volunteers, this weekend in my garden!
It was amazing to bring this crew (which overlaps with our Tune Up and Archiving volunteers) together again. This version of the kits has a really good adjustable wrench, a flat multi-wrench for holding bolts/ nuts along with the main wrench, a double headed screwdriver, cleaning cloth, small bottle of tri-flow lubricant, a mini sewing kit, and useful fasteners like velcro straps, gaffer tape, and heavy duty cable ties. It’s meant not only for routine maintenance and creative modifications, but for emergency repair — you never know when a cable tie and some tape is going to save you on the street!
In late April, we ran an extra Tune Up event at a Mutual Aid swap meet event in Berkeley that was focused around donations of medical equipment. Here, you can see Olga taking apart a rollator on the sidewalk at the Mutual Aid event, to give it some tender loving care. We removed enough hair from the wheels to create a whole new pet and we fixed the brakes so that they work again.
The rollator’s owner was scream-laughing with horror at how much hair came out of just one wheel axle! I wish I had a photo of her clapping with excitement at how the rollator didn’t just escape down hill when she set the (newly fixed) brakes. But it is burned into my brain as a lovely memory!
Here’s some nice pictures by Aaron from Streets Forward, of one of our previous Tune-Up events at the Disability Cultural Center. It took a whole group of us to figure out what was going on with this manual chair’s quick release wheel!
Our experience so far with these community events is that we can’t solve every problem on the spot. But what we’re doing is beyond sharing tools and manuals. We are demonstrating the process of troubleshooting and diagnosis. We don’t take the machine away from its owner and work on it in a back room out of sight. It’s something we approach together and so the chair owners learn that no matter what your experience, you don’t know everything from the start, you have to kind of experiment, try different things, come up with a hypothesis and test it. What’s causing that grinding noise ? We can test some things and find out. It is an approach that rejects authority and hierarchy, a rejection of the ways that secrecy hoards power. Instead, we share knowledge and hands on empowerment, even when, or especially when, we don’t know all the answers!
That open, experimental, hacker’s attitude is part of the energy we put into our disabled community! And it’s a critical part of disability culture — we have to take control of what we can, improvise, and work together in a world of uncertainty.
From my records, we “fix” about a third to a half of the devices people bring to our events. Another good chunk of the issues that crop up need follow up and referral. For those cases Vincent and Angello from ILRCSF have been able to help people effectively! That can mean help calling their device vendor, manufacturer, or working with them to get insurance to cover replacement parts. We also work with other Bay Area orgs who generously share their expertise and spare parts, and who handle follow up with people who come from other towns to our San Francisco events.
There are a small handful of folks who need us to really hustle and do extra to be on their side, and I’m proud to say that along with the orgs I’ve mentioned, GOAT has helped three young people who had nowhere else to turn, to get refurbished, donated powerchairs. This is close to my heart because years ago, I was in that situation, without any support, upset and terrified at the loss of mobility I was experiencing, and because of another wheelchair user who gave me their old chair, it was just life-changing, and helped me figure out how to get to a more stable situation. It is good to give some of that back into the world.
For the next couple of months — We will be planning extra events at locations in the East Bay for May, June, and July, and we are expanding our collaborations to work with MELP on the Peninsula!
Here’s more ways to find out about our wonderful grant sponsor, Ability Central:
