Cytronex tips

[Pedalo]

A Cytronex trek 7.3fx is on its way to me! Yee-ha

I've had a quick trawl for tips on bike / battery usage and have found the following.

i) Charge the battery immediately before use for best results.
ii) Don't charge the battery immediately after use while it's still warm.
iii) Don't overcharge (doesn't the charger prevent this?)
iv) Don't let the battery drain completeley (contradicts a thread where it was suggested to deliberately drain the battery once in a while. What gives?)
v) For best efficiency, always pedal to at least 5mph before switching on the motor.
vi) In general use the low setting for 5-11mph and the high for anything over.
vii) Always unplug the battery when the bike's not in use.
viii) Enjoy the fresh air!

Anything I've missed?
I do have a couple of questions:
a) If I'm going downhill (>15mph) is it best to switch the motor off? (i.e. is it still consuming power when the bike is running faster than 15mph?)
b) How much does switching the lights on affect range? Do people leave them on by default for max visibility?

 

[Fecn]

i) Charge the battery immediately before use for best results.

Many people know that NiMH batteries loose their charge very quickly. Around 30% self-discharge per month is typical. However, not a lot of people know that the first 10% of the charge is lost as the pack cools down after it's finished charging. If you want the maximum from your battery, put it on the bike whilst it's still hot off the charger.

ii) Don't charge the battery immediately after use while it's still warm.

NiMH cells are actually a very tiny little hydrogen fuel cell, with the Hydrogen stored in a metal chemical matrix (I can't remember the exact one). When NiMH cells are fully charged, any excess charge energy is converted to heat and so the cells get hot. Most NiMH chargers use a temperature cutoff to prevent overcharging, but if the cells are warm from discharge in the first place, then they will reach the cutoff temperature much more quickly and terminate the charge earlier.

iii) Don't overcharge (doesn't the charger prevent this?)

Any fast NiMH charger will have an auto cutoff facility, as otherwise the cells would soon explode. NiMH 12-hour chargers are a different matter as they rely on the cell's ability to convert any extra charge into heat. If you're charging faster than you can get rid of the heat then you need a cutoff. As the Cytronex does 90-minute charges, I'd be totally amazed if it didn't have a cutoff - Someone would surely have exploded their batteries by now.

iv) Don't let the battery drain completeley (contradicts a thread where it was suggested to deliberately drain the battery once in a while. What gives?)

NiMH cells are not damaged by being drained to zero volts - However, they are damaged by being taken to negative voltages. If you have a single cell on it's own, then it's fine to totally drain it. If you have a series of cells arranged into a battery pack, then you should never drain it. When in a pack configuration, there will always be one cell which runs out of charge before the rest. When this happens and the weak cell hits zero volts, then it will still have all the other cells in the battery pack trying to force their current through it - This will reverse charge the cell and take it to a negative voltage which will result in premature battery death.

vii) Always unplug the battery when the bike's not in use.

Depending on the motor controller and switches in use, the bike's electronics may consume a very small current even when switched off. Over the course of a few weeks/month, they may significantly drain the battery.... but as they're NiMH batteries, you're going to loose 30% charge per month anyway... so I'd be inclined to ignore that bit about unplugging when not in use. The difference will be marginal at best. - Maybe it's a safety thing like my wife unplugging the telly every night?

 

[flecc]

NiMH cells are actually a very tiny little hydrogen fuel cell, with the Hydrogen stored in a metal chemical matrix (I can't remember the exact one).

Early NiMh cells did use an exotic metals mix but they were inclined to fail within 100 charges. Some of the cheap shorter lived later types still use something similar, a mix of titanium and/or vanadium, zirconium or nickel, modified with chromium, cobalt, iron, and/or manganese.

The better cells which we use on e-bikes partly use rare earths for their anodes instead, typically a mixture of lanthanum, cerium, neodymium, praseodymium, nickel, cobalt, manganese, and/or aluminum. The electrolyte used to provide the ions is a solution of potassium hydroxide.

NiMH cells are not damaged by being drained to zero volts - However, they are damaged by being taken to negative voltages. If you have a single cell on it's own, then it's fine to totally drain it. If you have a series of cells arranged into a battery pack, then you should never drain it. When in a pack configuration, there will always be one cell which runs out of charge before the rest. When this happens and the weak cell hits zero volts, then it will still have all the other cells in the battery pack trying to force their current through it - This will reverse charge the cell and take it to a negative voltage which will result in premature battery death.

Controllers typically cut the supply to the bike when the voltage drops to about 1.1 volts per cell equivalence to limit any possibility of any cells being taken down to zero. Some authorities insist cells should never be taken below about 0.7 volts to protect the hydride from becoming unusable, but whether this is connected with the change from metals to rare earths I don't know.
.

 

[Barnowl]

Yes the fast charger cuts off when the batterys charged - Full charge is about 90 mins.

Yes the adviice from Cytronex is to unplug after usage. I think it's a good habit I nearly had an accident myself when I accidently knocked the on button.

The drain thing that seems like conflicting advice is recommended by Cytronex to be done every 1000 miles or so. There's a Mark/Cytronex post on this.
I normally charge mine before it runs out and don't push the battery for any more if the motor starts spluttering before I get home. It takes a fair bit of draining anyway.
It's all really easy to judge battery usage. Just reset the trip on the speedo to 0 every time you put the battery back after recharge and recharge it after about 12 - 20 miles.

 

[barrycoll]

could someone very kindly answer ('again') all the questions posed about NiMh batteries but Pedalo, into answers for lithium batteries...
all these answers are about the website somewhere, but my brain goes into meltdown looking for them...I need to be re-charged even more often than my batteries!

 

[flecc]

could someone very kindly answer ('again') all the questions posed about NiMh batteries but Pedalo, into answers for lithium batteries...
all these answers are about the website somewhere, but my brain goes into meltdown looking for them...I need to be re-charged even more often than my batteries!

Everything the same except that lithium batteries last longest if the charge is only partially used on each occasion. Therefore charge after each run, unless the run is very short of course, rather than using the battery to empty always. There's no need to occasionally run a lithium battery down to empty except in the case of batteries with integral meters which do drift out over time if the battery is never emptied.

A technical difference is that the charge cutoff is controlled by a lithium battery's internal electronics (BMS), not by the charger as happens with NiMh, hence different charger types are necessary.
.

 

[Fecn]

Lithium batteries don't have the same high self-discharge as NiMH, so there's not quite so much advantage in using them hot off the charger. There will a teensy bit more power straight off the charger as the BMS won't have had the chance to fully balance the cell voltage levels. Most BMS systems simply burn off some of the cell voltage as heat until all the cells are at the same voltage level. A month after charging, a lithium batt will still have around 97% of it's charge stored.

Lithium batteries should never be allowed to become completely discharged as they become chemically and irreversably damaged - However - it's the job of the BMS to cut off the power from the battery before that can ever happen. BMS systems themselves will drawer a small current from the battery however, which means it's important to top-up Lithium batteries every few months. Some BMS systems (such as the panasonic ones) will go into a standby mode after a couple of weeks to prevent the battery going flat when it's in storage.

Overcharging is a non-issue on Lithium batts due to BMS and charger technology without which, overcharging would rapidly result in explosions. NiMH cells can be charged at a variety of different voltage levels (from 1.3 to 1.7 volts per cell) and still achieve full charge. Because of this, it is very difficult to work out the charge level in any cell until they start to burn off extra charge as heat. Lithium cells on the other hand are charged using a constant voltage charger which will take the cells to a preset level (4.2V for lithium cells) which indicates the cell is fully charged. The big gotcha for charging Lithium comes when the cells are arranged into a battery pack - When a lithium cell is fully charged, it will stop the charge flowing into other cells within the pack - It's the job of the BMS to skim off a little bit of voltage from each of the cells until they all have the same voltage level as the weakest cell. This allows all the cells to eventually achieve the same charge level.

Here's an example of how simple BMS/charger systems for LiFEPO4 pack works.
The charger itself is a constant voltage charger putting out 33.17 volts
The pack is a 9-series pack consisting of 3.2 volt cells
The simple BMS on this pack has two functions.
1. If the voltage on any cell gets higher than 3.60 volts, start to burn off power at 100mA per cell
2. If the voltage on any cell gets higher than 4.00 volts then temporarily disconnect the charger - At 3.80 volts, reconnect it.

When the pack is fully discharged, it has a pack voltage of around 24 volts. Individual cells will range from 2.5 to 3.0 volts at this stage.
As the charger starts to pump power into the pack, all the cell voltages start to rise.
When the cells start to hit 3.60 volts, the little red lights on the BMS start to appear.
After a while longer, one of the cells will hit 4.00 volts, and then the light on the charger goes green and it sits there waiting. Slowly.. over the course of a few minutes... that 4.00 volts will be pulled down by the BMS to 3.80v, and then the charger will kick in again.
Eventually all the cells will reach 3.60 volts and all the lights on the BMS are lit - This is time to unplug the charger for ping packs.
About 30-60 mins after the charger has been unpluged, the BMS will have burned off enough power from each cell so that they all hit 3.60V
Charging is complete - All cells are nicely balanced at 3.59 volts - Total pack voltage for fully charged is 32.4V for my pack.

Sorry if nobody cares about any of that except me - I've been in battery geek mode this week as I was rebuilding the Ping pack and doing comparative tests versus my NiMH and LiPoly packs.

 

[uk_steve]

Thank you Fecn

thats good info above

 

[jerrysimon]

A Cytronex trek 7.3fx is on its way to me! Yee-ha

Welcome to the Cytronex owners club

I have had my a S/H (ebay purchased £750, 1600 miles on the clock) Trek 7300 a couple a weeks now and used it all last week to cycle to work. It such a great bike and meets my requirement for a short pretty flat commute to work everyday.

I assume being a Trek you got it second hand ?

Curious to know how old it is and how much you paid if that's not too personal ?

Regards

Jerry

 

[HarryB]

Welcome to the Cytronex owners club

I have had my a S/H (ebay purchased £750, 1600 miles on the clock) Trek 7300 a couple a weeks now and used it all last week to cycle to work. It such a great bike and meets my requirement for a short pretty flat commute to work everyday.

I assume being a Trek you got it second hand ?

Curious to know how old it is and how much you paid if that's not tpp personal ?

Regards

Jerry

Just a guess http://www.pedelecs.co.uk/forum/classifieds/4764-cytronex-trex-7-3-fx.html

 

[jerrysimon]

Ah

I just came back from business and am catching up with threads so had not seen that.

Looks like a great deal!

Jerry

 

[Pedalo]

Just a guess http://www.pedelecs.co.uk/forum/classifieds/4764-cytronex-trex-7-3-fx.html

Could be.

I rode it for the first time (8 miles home from work) this evening. It was absolutely p***ing down but it didn't matter - the bike wasn't troubled by the rain at all and both it and myself got a good soaking. I am amazed at the level of assistance it gives on hills. One hill on my trip is pretty steep and I was very impressed that it really did just feel like I was riding on the flat.

I'll do a full review after I've put a few miles on it but right now I'm delighted with it!

One question - the front wheel had to be removed for transport. I have a rubber cap that looks like it should go over the nut where the wire comes out of the motor but it doesn't seem to fit. I suspect another component might have gone missing but if anyone can describe or show me a photo of how it's supposed to fit that would be great.

 

[jerrysimon]

One question - the front wheel had to be removed for transport. I have a rubber cap that looks like it should go over the nut where the wire comes out of the motor but it doesn't seem to fit. I suspect another component might have gone missing but if anyone can describe or show me a photo of how it's supposed to fit that would be great.

Take a look through this slide show posted some while back when "Aldby" purchased one of the first Trek 7.3 FXs.

It shows some pictures of the front wheel wire entry and rubber caps I think your talking about. There is one on both sides one with a hole in it to allow the exit wire to come out of.

Aldby's Photostream

Hope that is useful.

PS Just read the next post. I agree its not a great fit but mine is not bad.

Regards

Jerry

 

[HarryB]

Could be.


One question - the front wheel had to be removed for transport. I have a rubber cap that looks like it should go over the nut where the wire comes out of the motor but it doesn't seem to fit.

if it is a rubber cap with a hole in it for a wire then it does fit on the nut - I agree that it is not a great fit and mine always looks like it is going to pop off. I am surprised it came off as the plug should stop this.

 

[Pedalo]

Yes that's the piece I'm talking about. There's no way it will stay on mine. There is a slit between the two holes (probably broken?) Superglue should fix it but I'll just leave it off for now until I get some.

There's not a cap at all round the other side.

 

[HarryB]

No it shouldn't have a slit so looks like it is broken. It is quite a hard rubber or plastic so not sure if superglue will fix it. I don't think it will stay on if it is broken and you cannot get a new one on as the plug will get in the way. On my last Tongxin I used self amalgamating tape to protect the cable - doesn't look as good but it will work.

 

[Barnowl]

Yes that's the piece I'm talking about. There's no way it will stay on mine. There is a slit between the two holes (probably broken?) Superglue should fix it but I'll just leave it off for now until I get some.

There's not a cap at all round the other side.

I lost mine. Emailed Cytronex and Mark sent me a new one straight away. It's a small thing but it looks better with the plugs on.

 

[Pedalo]

I lost mine. Emailed Cytronex and Mark sent me a new one straight away. It's a small thing but it looks better with the plugs on.

Did you have to remove the connector to get the wire through the hole?

 

[HarryB]

Did you have to remove the connector to get the wire through the hole?

Could have been the other side he was talking about - looks difficult to get the plug through the hole or take it off.

 

[Barnowl]

Yes sorry - it was the other side which you said was missing.