Overvolting a currie from 24v to 36v

[moondog]

Nice !

 

[libranskeptic]

A variant on this is a perhaps common scenario, where one has a boring, tired and lame 36v battery looking for a home. What better than use it as an upgrade for an even lamer battery on a 24v bike.

Not sure how, but i gather its simple and efficient, lower the 36v battery output to ~24v +20%, ride a while & monitor heat etc., gradually crank up a bit more if comfortable.

Me included. My target 24v bike is a 200-250 watt model, set to 200, so clearly there is a lot of spare meat there, and makers have to be conservative, to suit all conditions, not just yours. The midwest is not the outback e.g.


i.e. you dont know what you dont know, so make safe assumptions, such as, surely 20% more is a no brainer. After that, slowly slowly.

10 amps 24v = 240w, 28v=280, 32v=320w

pick one you feel safe with and probably within motor/controller manufacturers tolerance ranges, having checked temperatures of components during daily use as u work your way up. Cool, you get to upgrade once a month .

 

[DrkAngel]

OEM 24V 10Ah SLA supplied restricted range and deteriorated rapidly.
Tried 6Ah then 12Ah NiCd with moderate improvement.

Tried 36V SLA then finally converted to 36V 20.8Ah Li-ion ... from recycled laptop cells!

Purchased a newer eZip that didn't support 10s 36V Li-ion so built 7s 25.9V 31.2Ah Li-ion that ran nicely on everything ... gave me a couple extra mph and tripled range!

Moved up to recycling LiP0 25.9V 25.92Ah

Found some good 18650 Li-ion cells and built 33.3V 31.2Ah pack that works with most of my eBikes

Yes I did upgrade some eBikes with a 24V - 36V+ cheap controller
And
With my "standard" LiPo 25.9V pack I was able to rig the multi-position switch so that in
position 1 it ran from 7s 25.9V pack,
position 2 runs 7s 25.9V pack in series with 3s 11.1V pack for an effective 10s 37V pack.
...
My TURBO switch.
"Legal" 20mph motor only "switched" to 25mph+ (near 30mph ... with substantial pedal assist)
(Changed freewheel from 20T to 16T to provide motor only 20mph from 25.9V)

 

[Albert Nieves]

View attachment 72550 View attachment 72551 View attachment 72550 These are my two controllers for my two ezip Currie bike, I seen a video on some guy name Sean putting four turnigy lipos on it and working. I tried it with four new lipos 5.0 in parallel and series but doesn't work. Does anyone knows why or have any info that can help me. I want to know if the stock controller & throttle works with 36v? HELP PLEASE

 

[NKN]

Success...

Ok,
Just hooked up my variable power supply to the bike, and was able to run it up to 36/38 volts without any problem. See attached photos. All I did was connect the supply to the terminals , lift the rear tire and throttle it up. The meter in the picture is showing no amps as I couldn't operate both the camera and experiment at the same time.

The initial throttle pegged the amp meter, then backed down and showed a steady 2.5a load at full throttle. Oh course, not much load with it freewheeling, but I am now confident that the Ping 36v LifePo4 will work.

Jeff

You need to test under load, and if precisely metering voltage input to controller, you need to set it at ~43V, not 36V. This is because a lithium battery (of any type) rated at 36V actually runs in a range of voltage from just over 42V when fully charged, down to ~30V when "fully" discharged. This is inherent to how stored direct current outflow functions regardless of battery type.

There are a few differences to consider by battery type, such as C-rate, which is how quickly a battery can discharge (deliver power). Lithium batteries such as RC LiPo have C-rates allowing enormous release of power, and they get really hot. They're fun to watch burn, very dangerous, hard to extinguish. Next in C-rate comes the LiCo/Mn (also nickel, usually) which have a fairly fast discharge rate, but less than the volatile RC LiPo. These are your 18650 cylindrical batteries and equivalent. C-rate is high enough to more than deliver what you need. These batts also get hot, but don't as easily ignite like the RC's do. Finally, the (prismatic or cylindrical) LiFePO4 have the slowest C-rate, which is still much faster than ANY SLA or NiCad or NMH batteries can deliver. LiFePO4 are almost impossible to ignite, even when crushed (but don't try it).

My point about C-rate. If you're very quickly delivering ~43V into a controller rated for 24V (which actually means ~33V estimated max for rating purposes, since that's what a 24V battery delivers when fully charged), you're over-volting by ~30% to the controller, then it's over-volting however much additionally to the battery -- about the same 30% assuming the controller doesn't have circuitry to monitor, regulate, and step-down limit voltage output to motor. You're gonna heat up your controller, then you're gonna (maybe) heat up your motor, depending on the wattage the motor can truly handle (ratings mean nothing with these Currie motors, I've found).

So you'll probably get it to work, and you'll feel the speed difference with the substantial additional voltage, PLUS, the fact you won't be slowed down by the choke-point of SLA batteries' C-rate: that's why your bike slows down after sustained throttle, but seems to recover after a "rest" period. That's your SLA bank running out of discharge capacity because it can only put out high wattage for short times.

36V nominal LiFePO4 batteries worked just fine for me in a similar Currie of similar vintage. I got rid of that clunky rack and badly shaped drop-in packs that lose contact at every bump. I used a regular rack and panniers for a pair of 15Ah 36V batteries, then wired up a switchbox (to the top tube) allowing me to run either battery, or both in parallel. (If in parallel, one must start with near-equal voltage in both batts, and the output was more than enough to do damage if I would have stayed on the throttle constantly, but it delivered a ton of wattage and gave impressive top speeds. (This was using the existing "24V" controller and motor. Motor casing could get pretty hot, approx 130F to the touch, but it had cooling fins and a breeze on it, and I never saw degradation.)

So, in my experience, yes, you can do this, and I'll bet that you blow your controller before your motor goes. At that point, either replace the controller with a 36V version, or pull off the motor and controller and whatever else, then put in a 36V front wheel hub motor that'll have its own proprietary throttle and PAS sensor and whatever else. The bikes are built like tanks (just like the motors), and not overly heavy sans SLA batts, making them decent to keep and play around with.

Have fun. But do test at ~43V, and do it under full throttle load going UP-hill (get that wattage waaaay UP), and make sure it still works. Preferably do it with a fast C-rate (high-wattage) source -- if you don't have a 36V lithium source to do it with, then rig up 6 fully-charged 12V SLA batts into dual banks (3S) that you will run in parallel (2P). That will give you enough power to know for sure. Oh, and let off the throttle frequently... (LOL)

 

[darwin]

I know this for a fact, charge 24v batts at 36v and you'll fry an electric highboy. Don't ask how I know this, cuzz I'll lie about it.

 

[NKN]

I know this for a fact, charge 24v batts at 36v and you'll fry an electric highboy. Don't ask how I know this, cuzz I'll lie about it.

LOL! Won't ask. Yes, that's true I'm sure.

In my post I just assumed the poster would use a 36V charger for 36V batteries he wanted to use to supply a 24V Currie controller and 24V Currie motor. Bottom line: It works, and won't blow your motor, nor your controller, nor your electric highboy -- -- so long as you back off the throttle regularly.

Interestingly enough, after hard use for a couple years on my 36V conversion, I gave my over-volted Franken-bike (was the Veneto step-thru model as I recall) to an elderly neighbor and he was still riding it in 2020, so he got about 6-7 more years out of it. One of the batts was dead, but he said he still got a ton of range from the one remaining LiFePO4 15Ah 36V pack.

So it can work just fine. Oh, and the reason I said the controller most likely to conk-out is because if it's trapped in that heat-box atop the gargantuan rack it can't cool sufficiently despite its little fins. After removing that rack I moved my controller to behind the seat-tube and heat-shrank all the wiring for neatness points. Then the controller got plenty of breeze, which is likely why it lasted.

Everybody else I knew who did this ended up blowing out their controller -- an easy enough problem to solve since it was the same controller used for about an 8-year span, and you could go to Craig's List and find beat-up eZip Trailz models sans batteries for around $100 and strip 'em for parts. Controllers from such bikes were rarely bad. Motors rarely bad also.

Sorry about your highboy.

 

[wheelbender6]

Look at posts from DarkAngel on endless-sphere. He does all kinds of mods with Curries.