I need to replace a fifutec sealed lead-acid rechargeable battery [12v -2.8ah]

Easy to fit and easy to buy.

Hoveround MPV5 Wheelchair Batteries (Replacement)

Battery Sharks https://www.batterysharks.com > mpv5_b12-35_x2

The Hoveround MPV5 wheelchair requires 2 batteries - SP12-35 NB (12 V 35 AH). Please note that you need to use all existing cables and hardware from your ...
US$110.98 · ‎In stock

12V 35Ah SLA Battery Replacement for Hoveround MPV5

Walmart https://www.walmart.com > 12V-35Ah-SLA-Battery-R...

Product details · ML35-12 SLA is a 12V 35AH Sealed Lead Acid (SLA) rechargeable maintenance free battery, Pack of 2 - UL Certified · Dimensions: 7.76 inches x ...
Assembled Product Dimensions (L x W x H): 7....
Assembled Product Weight: 48 lb "); background-repeat: repeat-x; display: inline-block; overflow: hidden; position: relative; background-size: 14px 11.4px; height: 11.4px; width: 68px;">"); background-repeat: repeat-x; display: block; background-size: 14px 11.4px; height: 11.4px; width: 62px;"> Rating: 4.3 · ‎6 reviews · ‎US$149.99 · ‎In stock

Replacement Batteries for All Hoveround Power ...

ezmobilitybattery.com https://www.ezmobilitybattery.com > hoveround-whee...

Hoveround · Hoveround MPV4 Power Wheelchair Replacement Battery (2 Batteries) · Hoveround MPV5 Power Wheelchair Replacement Battery (2 Batteries) · Hoveround ...

Hoveround MPV5 12V 35Ah Battery (2 Pack)

Raion Group https://www.raiongroup.com > hoveround-mpv5-12v-...

This Raion Power RG12350FP mobility scooter battery pack is a direct OEM replacement for your existing Hoveround MPV5 batteries (12V 35Ah).
US$119.95 · ‎In stock

Vector Battery - Vector VEC199 Replacement Battery (batteryinternational.com)

You might check the compatibility of the following:

12 Volt 1.3 amp hour (12v 1.3ah) Rechargable Sealed Lead Acid SLA Battery - Walmart.com

take it along as a sample to any battery shop and they will have a battery to suit

This battery should work -
12 Volt 7 Amp Sealed Lead Acid Battery

It is a 12 volt , 7 ah battery rated at 20 hr. Here is what the 20 hr actually mean -
What does 20 HR mean?

Open it up and find out what kind of batteries are in it.
12V 18Ah Sealed Lead Acid AGM (Absorbed Glass Mat)
AKA Gel Cell
Dimensions not listed.
Don't be surprised if the replacements cost more than the device.
The user manual says that the unit is not designed to have the battery replaced.
http://allpowersupply.com/Productlib/manual-PKC0BK.pdf

12V 18Ah Sealed Lead Acid AGM Google Search

Just hook these up to a car battery charger. If you need to buy one you can get these at Walmart, Target, CARQUEST, Sears, Napa and many other places similar.

Specifications for MGE Pulsar Extreme 1500 C 2U Rack Battery kit
Voltage 12V (Per Cell) Capacity 6Ah (24W) Weight 8Kg Dimensions 151mm x 94mm x 51mm (Per Cell) Lifespan 3 - 5 years Type Sealed Lead acid battery rechargeable highly efficient, leak proof and maintenance free
I think there are four batteries in the pack.

There are many companies on the Internet that offer Sealed Lead Acid Batteries, which may be less expensive than replacing the light. I would suggest identifying the particular battery your light has and then check what's available on the Internet to make a decision on whether it is cheaper to replace the battery or the light.

http://www.batterywholesale.com/battery-store/SLA-batteries
http://www.batterymart.com/c-sealed-lead-acid-batteries.html
http://www.atbatt.com/sealed-lead-acid-batteries.asp
http://www.zbattery.com/Batteries/Sealed-Lead-Acid
http://www.planetbattery.com/product.asp?id=10

After opening the unit up, this info I found out about the rechargeable battery.
*GS Rechargeable Lead-acid Battery (Portalac) PE12V7A (12v 7Ah) - sealed lead battery*

I hope that info help you, or someone, if you got a 12v 7AMP tip positive DC wall adapter, that thearadacly(sp?) will charge the battery, but I'm doing guess work since I don't know much about the AMP in voltage stuff.

I tried my best.

You can order it from Black and Decker, Vector sold all their product lines to them in 2006 and they carry the replacement battery cheaper than anywhere else I found.
http://www.dewaltservicenet.com/Products/ProductDetails.aspx?pid=69262&tid=16032