Igaro S1 Pro

Igaro describes its S1 Pro as 'The world's best dynamo hub USB charger', and it's certainly a great bit of kit, offering very dependable USB charging that'll be attractive to anyone going on long or multi-day adventures.

We've tested a few USB charging solutions on road.cc, including Igaro's D1 back in 2017, and the D2 in 2019. Most work in a similar way: a dynamo sends power to the unit, and when that power is sufficient, a USB port turns on to charge things. That's not quite how the S1 Pro works, though.

Buy now: Igaro S1 Pro for £233.33 from Igaro

The key to the S1 Pro is that it packs in two super-capacitors in its cylindrical body, which it uses as short-term power storage. The S1 is specifically profiled for the SON28 dyno hub (although it works fine with other hubs), so it knows how much power is available at a given speed and uses two tuning circuits to extract as much as possible, which goes into the super-capacitors.

When the S1 Pro decides there's enough stored energy for a stable charge based on the power the device attached wants to draw, it turns on the main USB port. That intermediate step means that the level of charge supplied isn't directly related to the power the dynamo is supplying, and the resulting charge is a lot more stable.

If you like stats then Igaro has this page which shows its own benchmarking against other dyno-power solutions.

The S1 Pro's capacitors and electronics are all housed in a long alloy tube, which has a hole to access the two USB-C ports and five blue LED lights to tell you various things.

It comes with two mounts that allow you to put it out front on your bar. If you find you struggle for space on your audax/touring setup then this might be a boon as you can hang lights or cameras off it, like I have in the pics. If you have an aero-section bar or an integrated cockpit then you'll be out of luck, mount-wise, but it'll also work in a bar bag or frame bag. You won't be able to see the lights then, obviously. If you use aero bars then I found it pretty easy to accommodate both, but it'll depend on how much of a round section your bars have.

When you mount it, you'll want to face the LEDs slightly away from you so you can't see them directly, unless you want to be really annoyed with them when it gets dark. Maybe the next version could include an ambient light sensor to dim them right down for the night bits. Or you could do what I did and just stick some mostly opaque tape over them...

Charging

When you start riding, the S1 Pro goes through a series of startup checks and then begins to fill up the capacitors. There are three LEDs on the body that show the level of charge. When the first LED is lit, the first USB port will power up. If the current draw is low (say, a small GPS) and more power is going in than getting sent out then the port will remain active while the capacitors charge up. If the current draw is higher than the charging current then the power in the capacitors will deplete; when they are empty, the S1 Pro will turn the USB port off, and charge until all three LEDs are lit.

Up to 1.5A charging per socket is supported, depending on what you're charging and what leads you're using. You can mount the S1 Pro either way round, but with the USB port LEDs on the left, as shown above, the right-hand USB light shows the status of the main port, and how much charge it's able to supply, by going from off, through three levels of flashing, to steady. Although, oddly, as you're looking down at the S1 Pro on your bar, the first port is actually the left-hand one, not the right-hand one. That took me a while to work out!

If you're charging something – like a phone – that can pull a high current for charging then you'll find that the S1 Pro only charges intermittently at most speeds, turning itself on and then off again to charge up. This is by design: the unit is supplying a more stable, higher charge current some of the time, rather than a lower, fluctuating current all of the time. One of the reasons for this is that some devices lock into lower-power charge modes when offered a low charging current, and don't revert once the power available is higher, so you waste energy.

The higher-power-for-shorter-bursts sometimes feels like you're missing out when you're actually riding, but the approach means you get maximum value from your dynamo, and it works with a broader range of devices: neither the D1 nor the D2 chargers would play very nicely with my phone during testing, whereas the S1 Pro charges my Pixel 6 with no trouble at all.

I found that my micro-USB battery bank (charging on USBv2 at 500mA) would charge constantly from about 10-12km/h, but I didn't ever really get a constant charge to my phone or my USB-C battery bank, which are both capable of USB-CC (1.5A) charging and higher, and that's a lot of power for a dynohub to supply. It's worth noting that with a SON 28 dynamo (which the S1 Pro is optimised for) you'd be getting about 30% more power than from my less powerful SON Delux, so you'd get less stopping and starting.

If you're chugging up a hill then there will be fairly long gaps between the charging periods; I found that charging my phone on slower hills I'd get a couple of minutes of charging and then a wait of six to eight minutes while the capacitors filled back up again. My own slightly Heath-Robinson setup to measure the power confirmed that the charge current is really stable, with very little fluctuation.

There are two USB-C ports on the S1 Pro. The other works as a sort of energy dump to make sure you're not losing anything that you've generated. As the super-capacitors reach full capacity, the second port turns on and charges whatever is attached, until the unit has freed up enough space to begin storing charge again.

Igaro says that it's a good idea to connect a battery bank to this port to soak up the spare charge. If you're charging something that draws a low current then on a long descent at a reasonable speed, both ports will be on.

Waterproofing

The S1 Pro might not look waterproof, with the big hole in the casing and the electronics visible inside, but it is, very. All the circuitry is fully coated to be completely waterproof, and the design of the unit means that the charge ports are well hidden from rain, recessed into the bottom of the unit. The ports are waterproof too, but it doesn't do to get anything carrying a current wet: galvanic corrosion between the port and the lead can ruin the contacts.

For that reason the design allows the leads to be fixed in place and then sealed with a silicone sealant to fully waterproof the electrical contacts, which is worth doing if you're depending on the S1 Pro on a long ride as your primary source of power. That'll mean that the leads are always in the unit, and you'll need to protect the other end from moisture too. I used the S1 Pro in the rain, unsealed, with no ill effects during testing.

Power in the bank

Igaro says that the S1 Pro is dependable enough that it does away with the need for a battery bank. In theory that's probably true, but it'll depend on how you like to do things. On a long ride I have a GPS and a phone that predominantly need charging, and there are lights and sometimes a camera too. Rather than faffing around with leads the whole time, I've tended in the past to dump the power into a 5,000mAh battery. That'll charge my phone once over, or do my GPS about three times.

The benefit for me of having the charge in the battery is that when I stop I can decide what needs charging and prioritise that, and the battery outputs at a higher power than the dynamo does; on a half hour stop I can get about 25% of charge in my phone. In an emergency where something you need is about to die you can always plug it in directly, and you can start with a full battery bank and plug the S1 Pro into your phone, say, until something else needs topping up from the battery, and then charge the battery back up.

Do whatever works for you, basically. I think I tend to err towards the battery because many previous chargers I've tried haven't really worked with devices (especially phones) all that well; here it's not an issue, so in time my behaviour might change.

Rate of charge

In terms of rate of charge, I've been averaging about 12% of charge per hour into my phone (Pixel 6 Pro, 5,000mAh battery) in the course of a normal ride, which is normally fairly hilly and about 20-22km/h riding average. You can maximise charge by turning your phone off, or putting it in flight mode, but I generally don't tend to bother. Things got charged noticeably quicker when I was busting along the flat for hours on a 400km audax in Suffolk and Norfolk where I managed nearly 27km/h for the first 300km. If only I lived somewhere flat...

I don't tend to use dynamo lights because I'm a lightweight and most of my long-distance riding only really involves one overnight stint; battery lights these days are more than capable of that and I prefer having the extra power available for descents. On top of that, I mostly use the excellent Ravemen LR1600, which will run from an external power source in low-power mode, so it's kind of a dynamo light if you ever need it to be.

If you are running a dynamo lighting system, the S1 Pro runs a check each time you start riding from a stop, to check for the lights, and if they're present then it'll prioritise lighting and only run USB charging if you're moving fast enough that there's extra capacity.

Each time you stop, the S1 Pro will remain on for four minutes, to provide a standlight for your dynamo lights; this is so it complies with the German StVZO regulations. It'll also keep charging devices during this time, although I found that the capacitors were generally depleted well before the timeout.

Enough power?

So it's a very capable unit that supplies usable power and is well designed. Could you use it as your only source of power on a long adventure? Well, it depends. If I was doing longish days of audax-speed riding – say, 10-12 hours in the saddle at 20-22km/h average moving speed – then from my testing I'd say that would be enough to fully recharge my battery, or my phone, which easily lasts longer than a day on one charge. Then there's the GPS, and maybe lights or a camera too.

If you're going faster and longer on an ultradistance event then that's proportionally more power you can generate and store, from both the extra speed and the duration, so you'd likely be fine if you're not also filming a long documentary of it, and you're using dynamo lights after dark. If you're bikepacking, say, and doing shorter durations or slower speeds then you might not be banking enough to keep everything running for multiple days.

> How to go bikepacking: A beginner’s guide to getting started

With all that said, the real answer to the question is: you're probably more likely to achieve it with this than with anything else right now. Igaro's comparison page that I mentioned earlier has to be taken at face value, in the sense that it's Igaro's testing that makes its thing look good, but I'd say that of all the charging devices I've had personal experience of – which is a decent handful – the S1 Pro feels like it's doing the best job of getting power from the dynohub into your things thus far.

I'm never that excited by the rate of charge that you get from a dynamo – it always seems a bit glacial, especially now when phones charge at around 20W from a wall socket and only take a couple of hours from empty to full. But I like what Igaro has done with the circuitry in the S1 Pro to maximise the available charge, and I also think the form factor works well and adds useful bar space on a distance setup.

Value & conclusion

In terms of value it's an expensive unit, and about £100 more than Igaro's latest version of the D2, which is still a great option if you're just going to dump power into, say, a battery that's less picky about charge currents. You can pay more: the steerer-mounted Cinq USB unit is £300. Given the build quality and the performance, I think the price is reasonable.

Do you need one? Well, it's a fairly niche product. Personally, I don't. I'm unlikely to take on anything bigger than a 600km audax and for that kind of distance my bigger 10,000mAh battery will keep everything charged just fine. But if you're planning a long tour or an ultradistance event and you want reliable power to keep things topped up then the S1 Pro is a high quality bit of kit that'll do that job as well or better than anything else out there right now.

Verdict

Really well-realised dynamo USB charger that adds a bit of bar real estate too