Okay, so I'm having hip replacement in a few months and bought a mobility scooter from an estate sale recently and the old lead acid batteries are kaputt... specs are 5 x 12v, 500W motor:

https://ebikepros.com/e-bikes/mobil...ooter-scooter-for-disabled-comfort-black.html

Very similar model to the Daymak Roadstar and several Emmo models, you see them every day here in Southern Ontario...

But when you look at replacing the batteries, it's hard to get a straight answer. I went to two reputable e-bike shops here and they were oddly mum, trying to sell crappy lead acid replacements at 5 x $90...

Looking at five of these bad boys in series, which would cost around $900:
https://www.amazon.ca/gp/product/B08VD88Q9K/

I know that charging could be a hassle (periodic "rebalancing", etc.), along with a new charger, but this is the best way to go, right?

 

Welcome to AAC!
I would go to Sayal and buy replacement lead acid batteries.
Learn how to take care of the batteries and you should get 3-5 years life out of them.

 

Also, I've spoken to several battery manufacturers and they don't recommend 5 in series, is this a potential hazard???

Here are some pics:

 

Welcome to AAC!
I would go to Sayal and buy replacement lead acid batteries.
Learn how to take care of the batteries and you should get 3-5 years life out of them.

Really, really wanna go lithium if I can keep the cost around $1000...

 

The three middle batteries were overcharged. They got hot and the cases got deformed under the internal high pressure.

 

Okay thanks, but you're kinda proving my point here... why on God's green earth would anyone wanna go back to lead acid with long charge times, finnicky charging, cold temperature concerns and about three times the weight?!?!? There are thousands of these types of scooters on the road and virtually no one offering a viable 60V LiFePO4 battery swap/solution!!!

 

Not that simple.
You basically need to re-engineer the charging system to suit the new battery chemistry.
That's why nobody wants to touch this- a liability nightmare.

 

Not that simple.
You basically need to re-engineer the charging system to suit the new battery chemistry.
That's why nobody wants to touch this- a liability nightmare.

DING DING DING! The bike shops/sellers/mechanics don't want to touch it, yet the LiFePo battery guys are like "go nuts, buy my batteries, they will work waaaaay better!!!"

Does anyone have some tips on how to do this safely and properly?

 

Sealed lead acid battery (SLAB) is proven technology with a solid track record. They are very robust and can take a lot of abuse.
I use them on my ebike, lawn mover, UPS, emergency lighting, back up power, etc.

 

The internet says you're best off using a charger that will charge each of the five LiFePO4 batteries separately. The cheap way to do that would be to add a 6 pole charging connector and 5 suitable charging bricks.
https://www.ebay.com/itm/265737468323

 

Lead acid batteries will tolerate overcharging due to imbalance to a certain point. In series configuration this is common practice after balancing electrolyte gravity and is known as an "equalization charge".

Lithium cells will absolutely NOT tolerate overcharging. Hence you will need to add a battery management system to keep all of the batteries balanced so none of them will overcharge. Failing that, you'll kill the cells as shown above.

You will also get less performance compared to lead acid. Lead-acid cells are nominally 2V, with 6 cells in series for 12V. Lithium cells are nominally 3.7V, with 3 cells in series for an average voltage of 11.1V. Lithium cells also have a wider operating voltage range, meaning they will drop well below that nominal value as they approach full discharge (3-3.5V/cell) and well above it at full charge (4.1-4.2V).

---

Biggest things that kill lead-acid batteries:
- Discharging them beyond 50% DOD
- Modern battery chargers with excessively high voltage settings repeatedly/continuously boiling off the electrolyte.

If you want to make lead-acid last, get deep-cycle wet cells that you can service. Maintain the electrolyte levels and keep the electrolyte gravities balanced, charge them at a gentle voltage and do not discharge them beyond 50%. Desulfate and equalize once in a while.