Tuesday, May 17, 2022

How to get the most power out of the MPT-7210A boost charger

In normal solar power systems used to charge batteries, the solar panel voltage is higher than the battery voltage, and a traditional charge controller can then be used. Sometimes, you want to charge a battery that has a higher voltage than your panels, though, such as an ebike battery with a small solar panel. For that you need a boost charge controller or boost converter. Very few are available, and the most common seems to be the MPT-7210A "MPPT" charge controller. It can also be used to turn any DC power supply (even a free cast-off laptop charger) into a battery charger.

MPT-7210 boost charge controller
The MPT-7210 boost charge controller

I say MPPT in quotes because the MPT-7210A does not actually do Maximum Power Point Tracking. But it is still a valuable tool -- it is basically a programmable boost converter that has a setting for the minimum input voltage to use. That way, as it ramps up power and the voltage of your solar panels is pulled down, it does not just keep increasing current and collapse the input voltage to zero like a normal boost converter would do, but instead stops when the voltage is pulled down to your setpoint. See my previous post on DIY power stations for more discussion on how MPPT technology works.

Sunday, April 17, 2022

DIY portable solar generator power station

So that we could improve general preparedness and be more comfortable during power outages, I decided it was time to buy or potentially put together a portable power station like is so popular for camping/outdoors and emergencies these days (such as from Jackery or Goal Zero). They are also awkwardly called "solar generators" because they can be charged with solar panels, even though they are really just batteries with some outputs. I suppose the solar panel is the true generator.

I realized this was actually a perfect opportunity for DIY: commercial systems are quite expensive, and DIY would be achievable since the components are so modular. Can be as simple as battery, inverter, and charger. Let's do it!

Completed solar generator power station in a milk crate
Completed solar generator power station in a milk crate. Battery, charge controller, inverter, charger, 12V outputs, USB ports, and zippered pouches for cables and accessories

Wednesday, May 12, 2021

Fixing a broken solar-powered motion light

I love the solar-powered motion lights I have at my house but recently one started coming on during the daytime, then by night barely had any battery left, so something was definitely not working right.

Success! Battery-powered light now running from a wall USB charger
Success! Battery-powered light now running from a wall USB charger

For fun I decided to open it up with my daughter to explore, and found that to my surprise, the inside was delightfully modular! Ripe for hacking. Maybe other models are similar inside? Let me know in the comments, please. I used the MITAOHOH MT-SL-82-4P which comes in a 4-pack for a shockingly low $20-$25.

(In general, it still blows my mind that any company can put products like this together for so cheap -- LEDs, solar panels, batteries, connectors, screws, wires, motion sensor, circuit board, and injection molded housings for $5 each, shipped to my door. Wild. That means negative externalities, unfortunately.)

Sad, dim solar light on during the daytime where it can't help anyone
Sad, dim solar light on during the daytime where it can't help anyone

Saturday, March 13, 2021

How to Fix Broken Power Button on the Saeco Vienna Plus

I’ve written a lot already about troubleshooting the Saeco Vienna Plus, but I still had a new problem happen to my machine the other day. Somehow the part of the front control panel holding the power button and switch had cracked, allowing the switch to be pushed all the way inside! Initially the switch only pushed in a small amount, so I removed the (no longer operational) button and was pushing the switch with my finger. Then it finally gave way and I was sunk.

Saeco Vienna Plus with cover removed
Saeco Vienna Plus with cover removed

Missing power switch! It recessed into the machine.
Missing power switch! It recessed into the machine.

The Solution

This can be fixed by opening up the machine and hot-gluing the switch in place!

Saturday, February 20, 2021

How to adjust Bowflex C6 and Schwinn IC4 water bottle holder position

The Bowflex C6 and Schwinn IC4 are great bikes to use with Peloton and other apps (see my analysis of using these bikes with apps), but the water bottle cage placement always had me bumping my knees on the top of my bottle. It probably inadvertently was influencing my form, so I wanted them moved!

Stock water bottle holder positions on the Bowflex C6
Stock water bottle holder positions on the Bowflex C6

Here’s a quick fix: For those of you irritated by the placement of the water bottle holders on the Schwinn IC4 / Bowflex C6, you can make a bracket to move them pretty much anywhere you'd like!

Extender brackets installed to move bottle holders
Extender brackets installed to move bottle holders

Saturday, August 22, 2020

Data and details on the Bowflex C6 bike with Peloton app

Early in the 2020 pandemic I realized I probably wouldn’t be going to a gym anytime soon. I already had a treadmill (see my treadmill repair guide), dumbbells, and yoga mats, so we wanted to expand that into spin classes and officially cancel our expensive gym membership. A proper Peloton bike and subscription is pretty pricy, so I wanted to see if I could get most of the premium benefits for a fraction of the cost. Short answer: you can!

The Peloton app can be used with just about any spin bike, not just theirs. And to boot, the monthly cost when you do so drops from $39/mo to $13/mo (super wacky; I guess they assume you aren't locked into their ecosystem and so have competition).

First let's talk about the bike I chose and the setup, then get into the technical details of how it works and how to get the best power data out of it.

Home gym with Bowflex C6
Home gym with Bowflex C6 and iPad Pro (with SelectTech 552 dumbbells!). I cleaned up the power cable with gaffers tape.

So which bike?

You could go cheap (~$330), and it’ll work, but I wanted to mostly replicate the premium experience. A Peloton bike runs $2245 for the base kit with no accessories, but for $950 (hmm, now $999) you can get a Bowflex C6 with all the fixins (or even spend $100 less for the Schwinn IC4 which is the same thing with different accessories [no mat] and graphics. The Bowflex had a shorter lead time when I ordered. Sales rep for the parent company Nautilus confirmed they are mechanically the same.).

Saturday, July 18, 2020

How to Carry a Bike With Another Bike

For years I’ve wanted to tow a bike with another bicycle and had this towing solution tucked away in my garage. Now I finally want to make it available to everyone! What do you do when you have one person and need to move two bikes? Maybe you’re taking a bike to be repaired, or your dirt jumper to the bike park, or picking up your friend at the train station and don’t want to drive there. Or you left your bike at the bar and need to pick it up the next morning. I searched all over and couldn’t find a solution that was compact, easy, and did not involve disassembling the second bike, so I designed my own device to tow one bike behind another.

Updated 4/21/2021

Attached bike ready to tow, thanks to my assistant


Assembled bike towing system ready to ride
Ready to go! And it won't fall over!

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