using model aeroplane lipos

[MalcolmW]

Why cant I post this in the technical forum?



Ezeebike 36v lipo cost £400 for 10amphr. Expensive, probably because it contains a lot of battery management. I have a regular short trip into town. well defined load of about 1200mahr

I propose using 2off 5cell 5000mahr lipo in series to give me less range but a lot less bucks and wieght. These are 30c batteries 150amp peak! (I fly rc electric planes)

Question: As I draw only 12 amps peak and 10amps steady for 15min can I just balance every few charges?

Question: How many cycles (ha) can I expect? :

Anybody beaten me to it?

 

[stevebills]

I see a lot of peps on endless using rc lipo's

 

[MalcolmW]

Steve,

can you point me at the literature?

Do you have any comment, or experience of using rc lipo's ?

m

 

[stevebills]

join this site and do a search there is loads of info on rc lipo's

Endless-sphere.com • View forum - E-Bike General Discussion

 

[NRG]

I use the 25C lipos on my DIY Peugeot, they work well, give great power and above all are compact and light.

If you are an RC flyer you'll know the inherent issues with these batteries so avoid discharge below 3.2v / cell to give some safety margin and also charge to about 4.1 / cell to extend cycle life.

The current available RC lipos hold balance incredibly well if treated as above and as long as you have some form of LVC warning done on a per cell basis and balance every now and then they should perform well

 

[flecc]

The Technical section is confusingly named, its intended for permanent items. Queries are best posted in this forum as you've done.
.

 

[MalcolmW]

Thats really helpful NRG.
I was very dissapointed when I discovered the real economics of elect bikes.vis battery replacements. Rc batteries provide a way of addressing this problem provided one can get enough recharge cycles. I cant find anything on this for using lipos at such low discharge rates (30c *5=150amps) we are only using 0.5c which is very very low.
for a 3cell lipo 80% of charge is between 11volts and 12volts emf. No point in pushing outside this.

 

[NRG]

Discharge is a bit higher than that but yes well within the capability of RC lipos. Typical 37v bike will have a 15amp current limited controller and sport a 10Ah battery so around 1.5C discharge possibly hitting 2C as the current limiter in the controller is a bit crude.

Somewhere on ES there's info posted on cycle life of around 800 or so charges if they are treated as described above. That's very good especially given the low initial cost, size, weight and ease of replacement if a cell dies.

 

[jbond]

RC Lipo seems fraught with danger to me and to require a considerable amount of home brew. Which is a shame as they also have some clear benefits.

There does seem to be a need for small light battery packs. Something like 36v-5AHr but with sufficient C rating to work with a typical controller-geared motor setup. There's a couple of people on here that have used RC A123 packs for this but it's still not as plug and play as E-Bike batteries. The best and most complete solution I've found so far for this is Cellman (ES for sale section) who could supply a custom A123 (LiFePo) pack in 12s2p with a 30A max BMS and charger. That's going to be simple to use and charge and the only DIY part is going to be organising suitable connectors and mounting it on the bike somewhere.

Custom A123 packs are not especially complicated *if* you know what you are doing in building battery packs. Perhaps if more people asked for this style, new suppliers would spring up.

 

[NRG]

Once you sort out the LVC and charging they are quite easy to live with but I agree they are not plun 'n' play. I bulk charge my pack with modified Meanwell CC/CV power supplies so I don't have to reconfigure the pack, minimising risk.

The only real manual part of charging is connecting up the balance taps to the Battery Medics I use for balancing and HVC.

 

[Deleted member 4366]

I've used lipos in one of my bikes and they worked OK. I paid about £50 for a 36v 5.3aH pack. I then bought another pack to get 10.6aH, but by the time I'd bought all the leads, connectors, chargers, balancers, low voltage alarms and voltage indicators and made a box to put it in, it wasn't much cheaper than a ready-made 10aH lifepo. The main advantage was that it gave the 30 amps that I wanted - too much for a lifepo.

 

[jbond]

I've used lipos in one of my bikes and they worked OK. I paid about £50 for a 36v 5.3aH pack. I then bought another pack to get 10.6aH, but by the time I'd bought all the leads, connectors, chargers, balancers, low voltage alarms and voltage indicators and made a box to put it in, it wasn't much cheaper than a ready-made 10aH lifepo. The main advantage was that it gave the 30 amps that I wanted - too much for a lifepo.

Which is why, I think, people end up looking at A123 and Headway based packs. It would seem that A123 cells packaged with a conventional cheap BMS give you the robustness of LiFePo, the simplicity of a typical Lion E-Bike battery and enough of the high C rating of RC packs to be worthwhile. The downside is that there are very few sources of people who can put that together, weight/volume and cost.

Hobbyking and a couple of others do sell A123 based packs but without the BMS. Part of the problem is that 12s4p is 48 cells to keep in balance.

 

[averhamdave]

I use, and am very familiar with RC Lipos, using them in my RC hobby.

I continually consider them for the bike but am always put off with the thought of having essentially strip the whole battery assembly down for charging and then the hassle of the charging arrangement, which for me would be one battery at a time (and 4 or even 6 to do)

 

[jerrysimon]

I have a regular short trip into town. well defined load of about 1200mahr

I propose using 2off 5cell 5000mahr lipo in series to give me less range but a lot less bucks and wieght. These are 30c batteries 150amp peak! (I fly rc electric planes)

Depending on distance you could use a couple of these A123 DIY packs.

Full details here. Can be discharged at very high rates.

Need inital balancing but after that no BMS needed and can be charged as one pack using a cheap charger. Cost around £60 each plus £10 for charger. You probably already have a balancer being into RC

Regards

Jerry

 

[NRG]

I use, and am very familiar with RC Lipos, using them in my RC hobby.

I continually consider them for the bike but am always put off with the thought of having essentially strip the whole battery assembly down for charging and then the hassle of the charging arrangement, which for me would be one battery at a time (and 4 or even 6 to do)

That's why it's best to bulk charge them using a CC/CV PSU but you need to somehow balance out the cells at the end of charge. I use the HobbyKing battery medics...not an ideal situation but it works and I don't have to reconfigure the pack each time.

 

[MalcolmW]

NGR,
can you decode for me. LVC?
CC/CV constant voltage/ constant current. got that.
HVC?
regards Malcolm

 

[Deleted member 4366]

low voltage control
high voltage control
The batteries mustn't be overcharged or run down too far. The BMS looks after this if you have one, otherwise you have to find alternative methods.

 

[tangent]

I ordered a 24V 10Ah LiNiCoMnO2 battery from BMS Battery for $99. It comes with a BMS and 2A charger. Weight is quoted at 1.7kg. This seems like a good compromise to me between the hassle/danger of RC LIPOs and cost/weight of LiFePO4 batteries. Total cost worked out at about £85 including delivery. No idea whether I will be clobbered with duty etc. though. I will be using it on my Lafree which draws under 10A most of the time. I have had good results with series connected 4.6Ah RC NIMH batteries, but this 10Ah battery is only slightly heavier.

Anyone have any experience of these batteries from BMS?

 

[jbond]

Interesting to see BMSBattery now selling ECityPower LiNiCoMn batteries in cased and duct tape as well as Headway based LiFePo in duct tape. And all with BMS and chargers at keen prices.

The Headway based batteries have high current output, greater life but are nearly double the weight. Some of those LiNiCoMn batteries are seriously cheap.

This one
36V 15Ah Li-Ion Shrink Tube EBike Battery Pack - BMSBATTERY
Looks like a bit of a bargain.

 

[tangent]

Yes, they are cheaper and lighter than LiFePO4 which is why I went for one. I don't mind taking a risk for £85. If it lasts me 3 months I will be happy.

does anyone know why LiFePO4 are more expensive than equivalent capacity LiNiCoMn batteries? I cannot see why they would be more expensive to manufacture.