When I plug my Garmin Oregon directly into the regulator I’m only getting the power symbol. Now I’ve got rechargeable batteries in the Garmin and the little black button inside is pressed in using some plastic. When I then plug the Garmin into my powerbank the charge symbol appears. It seems that the dynamo isn’t charging my Garmin directly off the regulator. However this same set up charges my phone fine so does the Garmin only charge if there’s a pass-through powerbank inbetween it and the regulator?

Also interested in this. I have a dynamo hub and planning setting up this year. I was planning a permanent charge from dynamo to battery pack then charging garmin as and when from the battery pack.

Garmins can be quite fussy if the external power supply isn’t constant so the usual method is to have some form of buffer battery in between the dynamo and the Garmin.

As above I charge mine via a cache battery

I’m about to start ride-testing a system that has done away with the cache battery. It should be able to charge the batteries of the GPS during the day and leave the dynamo to power the lights during the night sections.

Results in a few weeks time…….

Surely this can be fixed with a regulator* and capacitor circuit?

Should be lighter than a battery, no?

*eg

Edit… My Garmin does charge without the battery but if I stop it bleeps so I prefer to use the battery

I have a device to regulate the dynamo voltage. This is just a question of how the Garmin Oregon handles the power from the regulator without any power bank. If there is a powerbank between the regulator and my Garmin the charge symbol appears, which is good as it means the Garmins batteries are charging. However, without the powerbank I just get the external power symbol. The batteries presumably aren’t charging, are they discharging? I’m basically trying to ascertain if my regulator is functioning correctly. It could just be a characteristic of the Garmin Oregon.

Not sure it’s worth the hassle for GPS. I get 4 long days out of my eTrex20 from Lithium batteries. Carry spares, they weigh nowt and aren’t very costly.
Lights are clearly another matter.

I hear you Ragga, but you could have a regulation circuit that’s just not doing the job well enough, I.E. not enough/fast enough capacitors leading to too much ripple, or, not enough current capacity without a voltage drop.

Put it this way, if the dynamo can actually deliver the current required, I see no reason why we can’t get it working…. If you’d like to try to do it like that, let me know.

Sam

Dynamos produce AC which will need rectifying, smoothing and then regulating. The SON28 hub produces at least 40V at high speed with low load (which a GPS is) so you’ll need some resilience.

I have (for Rob C) a working solution whereby I charge the AA’s directly inside the etrex and do away with the external cache batteries. Works on the bench and charges from about 6mph upwards.

A sensible sized capacitor is not enough storage to power the GPS for more than a seconds.

With a USB cache battery the problem I found was that they charge at 500mA (2.5W) at slow speeds (less than about 13mph) the hub can’t produce 2.5W so what happens is the cache battery is charged in pulses as it trys to charge, the dynamo voltage collapses and the charge ends and repeat.

Andy, how do you charge internal batteries in an Etrex? I have an SP dynamo and using a Sinewave to charge my Etrex and cache battery, I’d be interested to hear how you’ve done this.

With a USB cache battery the problem I found was that they charge at 500mA (2.5W) at slow speeds (less than about 13mph) the hub can’t produce 2.5W so what happens is the cache battery is charged in pulses as it trys to charge, the dynamo voltage collapses and the charge ends and repeat.

Assuming the cache is no more/less efficient being charged and discharged at the same time, if it even works like that? Would you not be better off using a slightly larger cache than GPS, charging the cache all day and plugging the garmin in to charge overnight?

My tuppence though (and I own an 800), I’d rather take a paper map. The garmin more often than not seems an inconvenience, a bit of tech that’s weesled it’s way onto the bike that I didn’t actually need, I think I’ve made more rides miserable trying to push my average upto some nominal number than I’ve gained in satisfaction seeing a little purple line appear on the screen afterwards.

I’m working on a solution where overnight recharges are not possible, the dynamo is the only power source for 20 or so days and the GPS will be powered for 16+ hours / day.

Two sets of rechargeable batteries? One set in use and the other being recharged from the dynamo.

Where are you riding, not questioning it, genuinely interested in what adventure you’re off on for 16 hours a day for 20 days, that’s ~5000miles?

My gut instinct though is still that it’s involving a lot of wires and potential headaches, when a paper map or route card and £10 cycle computer might be simpler with a phone app based map as a backup.

My charger is for robcolliver who plans redoing the Tour Divide. He is travelling as light as possible hence no cache battery, no phone only spot tracker. I’m sure he’ll provide details of his setup.

I charge an etrex by drilling a tiny hole in the back cover and wiring (and sealing) directly to 2 tagged AA NiMh 2600mAh batteries. The (remote from the GPS) charging circuit is a bridge rectifier, over voltage protection and 2 charging circuits. The ‘slow’ charger will trickle charge from about 6mph if the batteries are less than approx half full. The ‘fast’ charger takes over at about 10-12mph.

2750 miles divide 16hrs day@ 8.5mph = 20 days.

You could try one of those USB multimeter things.. there’s loads on ebay/Amazon etc..

Like this
http://www.amazon.co.uk/Universal-Voltmeter-Ammeter-Charging-Precision/dp/B00ZPT6E1A/

(cheaper ones available i believe)

I don’t have a multimeter but I’ll probably get one.

Where’s Scotroutes when you need him? He has an Oregon and a dynamo. I’m using a Sinewave regulator which I believe can handle over 50V so it’s pretty robust. I’ve ridden in excess of 40mph and that would be generating near to if not more than 50v unregulated voltage. The phone’s still charging fine but I’m not certain at this point if it’s charging as quickly as it used to. Maybe there’s less current from the regulator than there used to be but it would be handy if someone with a similar set up conducted a quick experiment on my behalf

Last night I took the gps/dynamo/charger out for a three hour hill session; the battery indicator was showing two bars (out of four) at the start of the session, and before the end (2000′ of climbing on muddy active logging trais)of the ride was showing fully charged again.

I’ll fully discharge the batteries before Sundays 7 hour ride and report back as to how long they take to be full again – this test may not be totally fair as I have to do a road section before the real ride starts and that will allow faster charging because of the faster speeds.

Very pleased to be doing away with the cache battery.

Bump.

Gave the gps/dynamo/revo charging system a really good testing last wee.

I started the ride to the peak district with one bar flashing and the low battery warning on the screen, rode 85 miles during the first day, 130 the next and stopped the charging and switched to powering the revo for the last hours of that day.
I then rode the final 40 miles to Edale with the Revo on and no charging of the gps happening. Perfect so far.

I then did another 3 days of riding trails around the peak district (in all about 26 hours of riding) before the rechargable battery ran out of stored juice inside the gps.

Thanks Andy G for your hard work in making a nav and lighting system that will outlast my ability to sit on the bike and pedal.

Great stuff! I too am making my own circuits for charging from a PD8X hub.

Andy G, about the charging circuit. Did you separate the two charging circuits with a monostable vibrator to switch over at predetermined speeds?
Also, did you add in a MOSFET to switch between having a supply to charge the batteries and running just off battery power. like a pass though circuit? Or did you just charge the NiMh in parallel with the load? I know that’s a non starter with Li-Ion but could be possible with NiMh and NiCad.
I hope to something like this for my GPS.

Just saw this thread.

I have a Kemo 172 (£29.99 from Maplins) between the dynamo and the Oregon. It charges it just fine – until you slow down. Then I get a “loss of external power – continue on battery or power off” warning. Building up speed again works, as long as it’s within 30 seconds. So, junctions usually ok, long climbs mean an extra button press.

The switch on the 172 also acts as a handy dimmer for oncoming traffic at night as it will cut the Revo from 4 to 2 LEDs

I’ve just fitted a Shimano XTdynamo and Busch & Muller lights to my Croix de fer and find it to be fab. The front light has an internal battery which can either power the lights (front and rear) when stationary or is used as a buffer/regulator/battery for when you plug into the supplied USB socket that hangs out of the bar mounted switch. It’s like a mini UPS! Loving it so far but understand that this setup isn’t ideal for a mountain bike.

Well, the system that AndyG built for me for my Tour Divide worked perfectly – I started in Banff with a fully charged etrex, rode for 21 days and quite a lot of nights (including straight through the last night) and it never came off four bars of charge.
The little switch that changes over to the Revo light worked as long as I didn’t knock it with the drink tube on the handlebars.

I rode through some belters of storms, dust and so much washboard that I say this system is fully tested and approved!

So, to recap…. no cache battery, no usb connection and no melting at 40 mph and charging right down at 4.5 mph.

A grat little solution.

Thanks Andy.