iStim EV-805 Rechargeable 4-Channel TENS/EMS Unit—24 Programs, 24 Pads

The iStim EV-805 is a rechargeable, four-channel electrotherapy device combining TENS sensory stimulation and EMS muscle stimulation in one portable system.

Four independently adjustable output channels allow up to four electrode pairs—or eight electrodes—to be connected during one session. This provides more placement flexibility than a standard two-channel unit when broader coverage, bilateral placement, or multiple treatment regions are needed.

The EV-805 includes:

• Five adjustable TENS modes
• Three adjustable EMS modes
• 12 preset TENS programs
• 12 preset EMS programs
• Four independently adjustable channel intensities
• Two treatment timers
• Adjustable pulse rate and pulse width
• Adjustable EMS ramp, contraction, and relaxation times
• Rechargeable lithium-battery power
• Backlit LCD display
• Four lead-wire sets
• Twenty-four reusable electrode pads in the current iStim retail package
• USB charging equipment

The current rechargeable EV-805 is included in FDA clearance K202317 for lithium-battery-powered, over-the-counter TENS/EMS devices.

• Rechargeable TENS and EMS combination stimulator
• Four isolated output channels
• Up to eight electrodes in a four-channel setup
• Independent 100-step intensity adjustment for each channel
• Five TENS modes: Burst, Normal, Modulation, SD1, and SD2
• Three EMS modes: Constant, Synchronous, and Alternate
• Twenty-four total presets
• Twelve TENS presets and twelve EMS presets
• Pulse rate adjustable from 2–150 Hz
• Pulse width adjustable from 50–300 microseconds
• EMS ramp adjustable from 1–8 seconds
• EMS contraction time adjustable from 2–90 seconds
• EMS relaxation time adjustable from 0–90 seconds
• Two timers for separate channel groups
• Treatment time adjustable from 1–60 minutes or continuous
• Backlit LCD screen
• Rechargeable lithium-battery system
• USB charger included
• The current package lists 24 electrode pads
• FDA 510(k) cleared for over-the-counter use
• A one-year warranty

The EV-805 instructions document its four channels, adjustable parameters, two timers, modes, presets, output specifications, rechargeable package, and USB charging equipment.

An asymmetrical rectangular monophasic waveform and the output ranges shown above. Use the instructions packaged with the current rechargeable unit as the final authority if specifications or accessories are revised.

Each channel controls one lead wire connected to a pair of electrodes.

Four channels can be useful when the treatment plan calls for:

• Broader back or extremity coverage
• Right-and-left symmetrical placement
• Multiple muscles
• Two separate treatment regions
• Additional placement flexibility without repeatedly moving pads

Four channels do not automatically mean stronger treatment. Each channel’s intensity should be adjusted according to pad location, skin response, comfort, and the intended TENS or EMS goal.

Although TENS and EMS both use surface electrodes, they are intended to create different responses.

The EV-805 operates in either TENS mode or EMS mode. It is not intended to deliver TENS and EMS simultaneously during the same program. The user selects one modality at a time.

For a more detailed explanation, read TENS vs. NMES: Key Differences, Uses, Benefits, and Safety.

The Normal and Modulation modes allow pulse rate and pulse width to be customized. Burst mode uses grouped pulses, while SD1 and SD2 automatically vary the stimulation pattern.

Read What the Five TENS Modes Are Used For for additional mode guidance.

EMS programs are intended to produce a controlled muscle contraction. The correct intensity is therefore normally higher than sensory-level TENS, but the contraction should remain tolerable and should not feel sharp, burning, or painful.

The published instructions state:

• On time must be long enough to include ramp-up and ramp-down.
• In Alternate mode, off time should be equal to or greater than on time.
• Rest time helps control muscle fatigue.
• Each channel group should be programmed according to the target muscle and treatment goal.

The EV-805 includes 24 preset programs in addition to its manually adjustable modes.

The TENS presets use different combinations of:

• Normal stimulation
• Burst stimulation
• Modulation
• Fixed pulse rates
• Mixed frequencies
• Frequency sweeps
• Different pulse widths

The EMS presets vary:

• Pulse rate
• Pulse width
• Ramp time
• Contraction time
• Relaxation time

The EMS presets use synchronous mode in the published program table, with progressively different work-and-rest timing.

Preset numbers should not be marketed as diagnosis-specific treatment prescriptions unless the current manufacturer manual expressly assigns them to a condition or body part.

The EV-805 provides two timers:

This permits the two channel groups to operate for different durations. Treatment time can be adjusted from 1–60 minutes, with continuous operation available where permitted by the selected mode.

For example, a trained user may set the following:

• Channels 1–2 for one treatment time
• Channels 3–4 for a separate treatment time

The treatment modality remains TENS or EMS across the device; the timers do not allow one channel group to run TENS while the other runs EMS.

Each channel has its own increase and decrease controls. The published manual describes 100 linear adjustment steps per channel.

This is useful because

• Skin sensitivity differs between body areas.
• One electrode pair may be closer to a superficial nerve.
• Larger pads may feel different from smaller pads.
• Right and left sides may have different tolerances.
• EMS motor points may require different intensities.

Do not assume all four channels should display the same intensity.

The EV-805 is the lithium-battery rechargeable version cleared under FDA K202317.

The EV-805 is rechargeable, but it is not wireless. Four lead wires connect the device to the electrode pads.

Do not use the device while it is connected to a charger unless the current included instructions explicitly permit operation during charging.

1. Charge the device

Charge the unit using the supplied charging equipment before initial use.

2. Keep every channel at zero

Confirm that all four output intensities are at zero before connecting lead wires or applying pads.

3. Connect the lead wires

Insert the required lead wires into Channels 1–4.

Only connect the number of channels needed for the planned setup.

4. Connect the electrodes

Attach two electrodes to each active lead wire.

5. Prepare the skin

Apply pads only to clean, dry, intact skin. Remove lotion, oil, perspiration, and dirt.

6. Position the electrodes

For TENS, place electrodes around or near the intended treatment area as directed.

For EMS, place electrodes over the target muscle and appropriate motor point region so the desired muscle contracts.

7. Select TENS or EMS

Choose the modality that matches the goal:

• TENS for sensory-level stimulation
• EMS for contraction-based muscle stimulation

8. Select a mode or preset

Choose an adjustable mode or one of the P1–P24 presets.

9. Set the timers

Set the CH1–CH2 timer and CH3–CH4 timer as needed.

10. Increase each channel separately

Raise intensity one channel at a time until the desired comfortable TENS sensation or controlled EMS contraction is reached.

11. Monitor the session

Stop or reduce stimulation for:

• Sharp or burning sensation
• Pain
• Unwanted muscle movement
• Rapid fatigue
• Worsening symptoms
• Skin irritation
• Dizziness or another unusual reaction

12. Reduce all channels before removing pads

Return all four intensity levels to zero and turn the unit off before disconnecting or repositioning electrodes.

TENS commonly feels like

• Tingling
• Buzzing
• Tapping
• Rhythmic pulsing
• A changing sensation in Modulation, SD1, or SD2 modes

The intensity should be strong and clearly noticeable but comfortable. Typical sensory-level TENS should not create a forceful muscle contraction.

EMS begins as tingling and increases until the target muscle contracts.

A normal work-rest cycle may feel like

1. The stimulation gradually increases.
2. The muscle tightens.
3. The contraction remains active.
4. The output gradually decreases.
5. The muscle rests.
6. The cycle repeats.

The contraction should be visible or palpable, controlled, and tolerable.

Choose the EV-804 when portability and two-channel simplicity are enough. Choose the EV-805 when four-channel coverage and separate timer groups justify the larger device.

Choose the EV-805 when TENS and EMS meet the treatment need and rechargeable power is preferred.

Choose the DS5402 when four channels are required together with interferential current and Russian stimulation.

The lithium-battery EV-805 is cleared under K202317 for over-the-counter use.

The cleared TENS indication is temporary relief of pain associated with sore and aching muscles in the following:

• The low back
• The arms
• The legs

The cleared wording associates this discomfort with strain from exercise or normal household and work activities.

The cleared EMS indication is stimulation of healthy muscles to improve or facilitate muscle performance.

The product page should not state or imply that the EV-805:

• Cures chronic pain
• Treats arthritis itself
• Repairs injured tissue
• Reverses nerve damage
• Prevents blood clots
• Treats medical muscle disease
• Replaces physical therapy
• Produces permanent pain relief
• Delivers TENS and EMS simultaneously

Do not use this device with a cardiac pacemaker, implanted defibrillator, or another implanted electronic device.

Do not place electrodes:

• On the head or face
• Over the eyes or mouth
• On the front or sides of the neck
• Over the carotid sinus
• Across the chest
• From the front to the back of the torso
• Over broken, inflamed, infected, or irritated skin
• Over known or suspected cancerous lesions
• In a position prohibited by the current manual

Obtain medical guidance before use when there is

• Pregnancy
• Suspected heart disease
• Epilepsy
• Recent surgery
• Impaired sensation
• A tendency toward internal bleeding
• Undiagnosed or changing pain
• Another significant medical concern

Do not use the EV-805 while driving, operating machinery, swimming, bathing, or performing an activity in which an involuntary contraction could create injury.

Replace pads when they:

• No longer adhere
• Curl at the edges
• Become dry or dirty
• Produce sharp stimulation
• Have damaged backing
• Develop an intermittent connection
• Have been used by another person

The EV-805 Rechargeable 4-Channel TENS/EMS Unit is best suited to buyers who need the following:

• More coverage than a two-channel stimulator
• Both TENS and EMS
• Four independent intensity controls
• Twenty-four preset programs
• Manual pulse-rate and pulse-width adjustment
• EMS ramp and work-rest programming
• Two channel-group timers
• Rechargeable lithium-battery power
• A large starter electrode package