Better Battery Life?

[slightly]

I use my phone for constant track recording and as such it drains from 100% to 10% in about 4-5 hours. Should I recharge my iPhone when it has exhausted each time or would I be better off running it with a trickle charge continuously from an external battery? Are there any benefits either way?

[Wilkyboy]

I did a fairly broad-brush write-up a while ago for audaxers here: http://www.16inchwheels.uk/2016/04/11/p ... ong-rides/. It's long overdue a rewrite to be more informed on what the numbers actually mean, and to include more empirical evidence.

However, the interesting points for you are those around the charging of batteries, the graph, and the conclusion, which is this:

• If power is unconstrained (e.g. a dynamo), just keep everything topped up all the time.
• If power is limited (e.g. a battery), then the most efficient way to charge one battery from another is to charge in one go to about 80% then let it drop to about 20% and charge it back to 80%.
• The most inefficient way to charge a battery is to take it to 100% — that final 10% uses a massive amount of the cache-battery's power to get from 90% to 100% and isn't worth it.

Depending which iPhone you have, having to recharge every 4-5 hours will result in you needing in the order of 8-15,000mAh of typical USB batteries for the weekend, I'd've thought.

For comparison, I'll be using a Garmin 1000 for track-recording duties, and that gives me about 8-10 hours between charges when the map's on the screen, so I'm taking about 8,000mAh, although I think I only need about 5,000mAh.

[slightly]

Great info - many thanks.

So could I reasonably expect to get 5 x 20% to 80% charges over a weekend out of a 10000mAh battery do you think?

[Wilkyboy]

Great info - many thanks.

So could I reasonably expect to get 5 x 20% to 80% charges over a weekend out of a 10000mAh battery do you think?

If you started with both fully charged then I think so, but if you're using a plus-size phone then it will be very close, because of the mahoosive battery (compared to something more svelte like a 5s or SE).

[whitestone]

Slightly OT.

For those who use a dynamo and converter to run lights or charge batteries is it advisable to disconnect the converter if you aren't actually running anything from it? I'm sure I've seen posts where people have burnt out the circuitry. If you leave it connected is it OK to have a fully charged battery on the other end?

Not ready your article yet Wilkyboy so if you've covered this in there then apologies.

[Wilkyboy]

Slightly OT.

For those who use a dynamo and converter to run lights or charge batteries is it advisable to disconnect the converter if you aren't actually running anything from it? I'm sure I've seen posts where people have burnt out the circuitry. If you leave it connected is it OK to have a fully charged battery on the other end?

Not ready your article yet Wilkyboy so if you've covered this in there then apologies.

I didn't cover that specific topic. It's an interesting one. As I understand it, any power generated that's not consumed is converted to heat. If you have a converter that is part of the headlamp unit (e.g. a Busch+Müller Luxos IQ2 U) then the top plate is a metal heat exchanger; if you have an Igaro then its outer casing is bare aluminium and they do say to mount it in the airflow to dissipate heat.

HOWEVER, generally the converters stop drawing power when there's nothing to supply it to, at which point this is largely moot: the generator spins open-circuit and it will be fine. So once your battery is charged, so long as the battery itself has charge-protection circuitry (most do — I've never come across one without), then the battery stop charging, the converter will stop converting, and the system will go open-circuit on the charging side and you'll be fine.

There's one additional point: charging a cache battery while using it to charge something else: very few batteries allow this, for both technical and safety reasons. Basically it's hard to do unless the battery has two halves inside — it charges one while using the other to charge with. And when it comes time to swap between the two halves, the circuitry has to compensate for potential difference between the two, so it doesn't pop your attached devices. It's sold as "pass-thru charging". I don't bother; instead I carry multiple smaller batteries and charge one while using the other — there is a tiny weight penalty, but greater obviousness and therefore easier to manage when tired (three days into LEL on 6 hours' sleep, for example).

Finally, my article was written for using a dynamo wheel on the road, audax mainly. For that I found it's not better than 60-70% full output over time/distance. For off-road in Wales I would've thought it would be half that or worse, given the very slow speeds most of the time (I speak only for myself).

[whitestone]

Cheers. Just finished reading the article.

So leaving the circuit as: Generator => converter => battery should be fine (it's a decent quality branded battery rather than a market stall knock off).

FWIW, my general strategy is to have things on their most efficient setting, so phone in "Airplane mode", etc., and recharge at night or when I'm not using the devices, usually at a cafe. This is with batteries as the source. I got through last year's HT550 with this, five days.

The notes about charging Li-on batteries are interesting as my method of just leaving them plugged in overnight is inefficient. Ideally you'd have some circuitry to detect the fall-off in current being drawn so you could stop the recharging at that point. More simplistically I suppose you'd have to know the length of each charging period for your device or batteries (I've a Garmin Oregon with Duracell rechargeables) and just charge for that sort of time.

[Wilkyboy]

Since writing the article — and discovering the huge inefficiency of the saturation-charge phase — I have become a lot less fastidious about aiming for 100% charge in my devices, unless I'm charging direct from dynamo and don't have anything else to use the power for. 80-90% is good enough. Unfortunately it is just a case of charging for a bit and checking the charge level on that which you're charging. I've switched to café charging with my Garmin on very long rides, or waiting for the 20% low-battery warning then plugging it in at the next stop and leaving it plugged in until it's ~80% charged and then pulling the lead out while riding.

I've found charging the phone to be the hardest, because it's in my back pocket so I'm not able to keep an eye on where it's at while charging. On multiday rides, I now switch it to airplane mode and if it dies then I'm not bothered — I'll charge it when I get the chance, nobody can contact me anyway.

For me, only the Garmin needs to be constantly available, and then only really because I like to collect the data for later analysis — I'm happy to navigate with maps and routesheets clipped to my stem, or onto the bar bag, although GPS is definitely easier at night.

[whitestone]

A bit of Googling - Duracell's own charger only charges NiMH batteries to 90%, presumably there's some battery state being sensed to stop charging at this point.

The manual for the Garmin Oregon states you should plug in the external power source and "charge the battery completely". The battery icon changes at this point from an animated charging one to a static icon so it's possible that it also stops at around 90%. I'm not sure how low the battery gets before the Oregon says "enough is enough" and shuts down. I've an inline USB multi-meter so I might check with that if I'm bored at some point.

I've read elsewhere that the charger in the Oregon isn't ideal as it charges the batteries in series rather than managing them in parallel as a dedicated charger does.

For this weekend's WRT, two spare sets of charged AAs will be more than enough.

Note: in my previous post I said I was using Li-On batteries, they are actually NiMH.

[Wilkyboy]

Note: in my previous post I said I was using Li-On batteries, they are actually NiMH.

Yep, the technology for charging NiMH compared to the more common Li-ion batteries buried in devices is different. I have no specific knowledge or experience with regard to that, nor of any switching/protection circuitry wrt NiMH.

[Wilkyboy]

Following my three-day jaunt on WRT, I have a data point that may (or may not) be interesting.

I rode around using a Garmin 1000, which was fully charged before I left. I had it on map-view most of the time. I took an IKEA (!) 5Ah (5000) cache battery (plus a 3200 "spare", in case I had got my numbers wrong). I waited for the Garmin to show me the low-battery warning at 20% and then plugged it in to charge at the next suitable stop, charge to whenever I'd noticed it had got to over 80% and unplugged it again. In about 26 — actually 25.5 — hours' riding (I'll have to check that) the IKEA brick was flat and the Garmin still had 75% left (which is about 6-7 hours' riding time).

If the weather had been cold instead of sweltering like it was then I think I'd've needed to use a small charge from the 3200 other battery too.

Therefore, on my next WRT jaunt, I'd take 2x 3200Ah batteries, to give a little buffer, and adjust for forecast temperature from there. The difference in weight would be +44g to go from the IKEA to 2x 3200s, but actually 42g lighter than I took for the weekend.

This is in line with what I expected — for internal Li-ion batteries.

[whitestone]

I went with my two sets of spare AA rechargeables. I started with a "fully charged" set in the Oregon but these ran out after about 7 hours on the first day so I don't think the unit or the batteries were reporting the correct charge. I replaced that set for the last half hour of day one. That set lasted all of Sunday, roughly 13hrs from setting off to stopping to bivy, and 8hrs on Monday. That set is still reporting some charge. Didn't use the third set.

My usage is to have the device on mapping but for the screen to switch off after 30 seconds of no user input so depended on where we were and how lost, I mean temporarily misplaced, we were.