n00b on the loose - no idea what I'm doing really!

Started with the whole eBike thing at the start of the year I was commuting 4 miles into work everyday with a big hill at the end that was just a bit much, public transport is expensive and driving means an hour in traffic. eBike turns out to be best value ever as I now make it into work in 20 minutes in any weather and it's the best part of my day. I've been stabbing in the dark to get to where I am now though and in general I think I've been pretty lucky, this is what I'm using

Conhismotor 36v front hub motor with conhismotor standard controller

Conhismotor 36V 15AH LiPo4 battery with BMS in a plastic hardcase

All fitted to a GT Avalanche 3.0 with hydraulic discs and a Topeak MTX pannier rack on the back.

A few questions to the gods of electric bikes if anyone can spare me a few minutes:

What's the best way to know how many miles you've got left in the battery? Last weekend I went out for a great ride across Ikley moore and the battery died 11 miles from home, with a big hill between me and home. Wasn't expecting it as I'd previously managed 26 miles before the pack died and I was no where near that. Ideally I'd like something like you get on car trip computers where it tells you at your current rate of fuel / battery consumption you have X amount of miles left until you're f*cked. Does such a wonderful device exist?

Apart from pedaling more / pumping the tires up, are there any good ways to squeeze more miles out of the pack?

Would a 40AH 36V pack be a dumb idea? ( Thinking a long trip )

I've got a 750W 36V rear wheel motor on the way with a disc brake, am I going to need to do some hacking to get my standard callipers to fit properly?

Can you get front / rear lights that tap into the 36V battery rather than burning through AA's?

Just for fun, could I (easily) run the 500W front and 750W rear motor simultaneously from the same 15AH pack? I took the bike to a downhill course a few weeks ago and got a massive buzz out of scrambling up a steep hill.

Thanks in advance!

Pic attached

Cycle Analyst from http://ebikes.ca, Watts Up, or Turnigy Watt Meter would be your best easy-to-get choices of "fuel gauge" for the bike, unless you like to DIY stuff, in which case there's a good one in a thread here on ES you could build and program.

I highly recommend the CA over the WU or TWM (having all three to compare here), as it also has the spedometer and thus can calculate things like Wh/mile for you, whcih will help you keep an eye on efficiency of the bike under various conditions, and let you gauge better how long your pack will last.

I don't know of a "trip computer" quite like what you want, unfortunately. I'm sure one could be fairly easily made if you wanted to write up the software for it--in fact you could use the Cycle Analyst as the primary data source, along with it's logging-to-serial-port function to get that data into a PIC or similar MCU to then work out the rest of the data to display on another screen.

At least with the CA, you can gather data about what kind of conditions cause you to use up how much power, and then estimate your range under those types of conditions. Then you can figure out if you'll have enough power without recharging for any specific trip (allowing for other issues like headwinds, etc.).

nonlineartom said:

Apart from pedaling more / pumping the tires up, are there any good ways to squeeze more miles out of the pack?

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Going slower, or using a semi-recumbent or recumbent, for better aero at faster speeds.

Would a 40AH 36V pack be a dumb idea? ( Thinking a long trip )

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No, but it'll be large-ish, and heavy depending on chemistry and how it's built (casing and whatnot). You'd probably want to have half of it on each side, low down in panniers at the back.

I've got a 750W 36V rear wheel motor on the way with a disc brake, am I going to need to do some hacking to get my standard callipers to fit properly?

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Possibly, as it depends on the width of the calipers especially on the inside where it faces the motor cover. Won't know till you get it installed.

Can you get front / rear lights that tap into the 36V battery rather than burning through AA's?

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Yes; or you can get DC-DC converters that change your pack voltage to whatever your lights need.

Just for fun, could I (easily) run the 500W front and 750W rear motor simultaneously from the same 15AH pack? I took the bike to a downhill course a few weeks ago and got a massive buzz out of scrambling up a steep hill.

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Sure, if both controllers and motors are meant for the same voltage and same speed at that voltage. Otherwise one of them (the one meant for lower volts) will end up taking most of the load, as it'll try to spin faster than the other.

HobbyKing HK-010 Power analyzer works for me.
http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=10786

The CA is worth every penny. Quite possible you took off on that trip less charged than you think. Even a 5 buck voltmeter could have clued you in to that, but not always, givine lifepo4's flat discharge curve. But a CA or any voltmeter at least gives you pack voltage at the start, and if it's 5v lower than normal, you get that chance to go WTF?

The CA gives watthours per/ mile, allowing you to see that this particular ride is taking more than usual, as well as AH used that can clue you in before it's too late, that it's time to slow way down and pedal more.

With the direct plug in controllers, the CA can also limit amps, which can help you with stretching range. Easy to blow your watts with a throttle, and no meter.

No, your battery will not run two motors. Pull 40 amps out of it, and it will die. Or at least keep cutting out when the bms trips.

Thanks for all the help. I thought I might have problems running two motors as it would pull too much from the battery. I've got a 30amp fuse in line from the battery and I've blown it once going up a hill. I just looked up prices and the CA is £150 in the UK and the Watts Up is £30. Is the CA really worth the price hike? Will I be able to avoid the "oh shit" moments using just the Watts Up or similar in line device? I do like the idea of being able to limit to power supply with the CA so I can save power, also makes it more "legal" as I'm guessing I can force it to draw less than 200W which is the legal limit here. I think you were right about battery not being fulled charged, as I said I've had problems with a loose wire in the BMS, when it comes loose the charger goes to a green light so that's probably what happend. Does anyone know where I can get a DC-DC converter in the UK for powering some LED lights and if possible a 5V 500mah power supply too, for charging USB stuff, I've been out for rides and my phones battery die because the GPS chip eats power. At the moment I'm using my phone for working out distance travelled and average speed to roughly predict range.

Another quick question if I may... best throttle control? the cheap plastic twist throttle I have is a little loose and getting abused, it also goes from slowest speed to full speed with about 5 degrees rotation, is there a more weather proof / durable thumb throttle solution readily available which I can use with my controller?

Thanks!

The CA seems really nice if you want/need all the features. However, if all you really need is a volt/watt meter. For $18.99 you can't beat the Hobbyking HK-010 Power Analyser. I just got one and it works great. In Watt mode it gives real time usage of watts, amps, battery voltage and amp hours used. You can see how many watts/amps you're drawing at different throttle settings. You can see how voltage sags. You can see if you have a full charge by looking at the battery voltage. Battery voltage will also tell you about how much usable power you have left. Or you can look at the AH used. In other modes you can balance packs with its built in balancer. You can even measure your charger and see how many watts/amps its charging at and the AH charged. And the screen stays in the mode you choose. Something I see many complain about some of the other watt meters. So if you don't want to spend $150 for a CA, then this is a great alternative for 1/8 the price.

Looks like I'll get one of those then! Thanks for that, really helpful, I'm a bit confused about these LiPo batteries, I'm used to NiMh and NiCad packs of olden days, what do you mean by "balancing" does that replace my BMS?

Also, is the meter you recommend pretty weather proof I.E can it be mounted on the handlebars or on the top tube permanently and deal with the British weather?

Thanks in advance.

Distance trips is where the CA really shines. No matter where I am on my trip I can make it home as long as I have something in my batteries. I have dialed the amps down to 5 amps before and crawled home.... I am that lazy sometimes. But, with a CA you will have total control of your bike and battery and you can know how to maximize your watt hours for the ride....
If your controller can take it you can volt up the controller dial down the amps on your ca and it can take you as fast and as far as the battery/bike will allow. 8) 8) 8) 8)
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1. Get a Cycle Analyst. Beware there are different versions. Some of them can plug into your controller, others are "stand-alone".

2. Start the bike off by pedaling- then introduce the throttle. If you nail the throttle from a dead start it will use a lot of energy. Full throttle cruising uses less power than full-throttle launching- a lot less.

3. You mentioned tyres- try a semi-slick compound- single-wall Maxxis Hookworms are an expensive {$40 a tire} option but they are puncture resistant and improve handling and have lower rolling resistance than a standard knobbly tire.

Any watt meter is better than no watt meter. But the CA is truly a great tool. One of the other nice features is it can take up to 100 v, if you are going there, and can be had in even higher volt versions for those going that far.

The CA may be the most convenient to use of all the wattmeters out there too. But if funds are tight, just get a cheaper one designed for general use.

nonlineartom said:

Is the CA really worth the price hike?

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If you need or want it's other features, like the interactiveness with throttle/etc (if you set it up), then yes. If all you want is an Ah counter / voltmeter, then the WU would do just fine, or any of the other alternatives.

Does anyone know where I can get a DC-DC converter in the UK for powering some LED lights and if possible a 5V 500mah power supply too, for charging USB stuff, I've been out for rides and my phones battery die because the GPS chip eats power.

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You may well be able to use your wall charger with the AC prongs hooked to the bike battery pack output to charge the phone/etc with, though slower than it would from the wall. Depends on the charger, as many will run from very low voltages DC or AC and some will not. As long as you have a spare one (just in case) you could try this and see if it works.

The DC-DC you need depends on the voltage and current your lights take. Right now you mentioned they run on AA batteries, right? Assuming that's two AA, then probably 3V, and not a lot of current (100mA or so at most, I'd guess, less if it has decent battery lifetime). So you might look for celphone chargers or similar at thrift stores, that have about 3V to 3.3V max output (you'd ahve to measure this before hooking to the LEDs so you don't smoke them, as sometimes it's a lot mroe than rated output without the original load). As long as the celphone charger wll runn on your pack's output, it's a really cheap DC-DC. Otherwise you could check with Lyen here on ES, as he sells a DC-DC that is probably adjustable to your LED sets' voltage. Lots of tehm on Ebay, too, but that could be a crapshoot.

is there a more weather proof / durable thumb throttle solution readily available which I can use with my controller?

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That is a problem many have. Best easy/cheap recommendation is to put the throttle itself in your battery bag, and run a cable to it from an old shifter instead. There's a recent thread showing this, I think it's the "show us your handlebars" thread.