Replace your car battery with capacitors!

[serialk11r]

While I was messing with my Aston Martin's Ford/Volvo alarm module battery (a sealed unit with an NiMH battery that goes bad), I suddenly remembered that NiMH batteries are lighter and more durable than lead acid and very cheap too. They generally aren't meant for high current but that's where this thread's focus comes in

On Amazon, you can get 20 Tenergy D-cells for 97 before tax (16 pack + 4 pack), and then configure them 10S 2P for 12V and 20Ah. This is a little bit less money than buying 4 unknown brand 20Ah lithium iron phosphate batteries (which have limitations on cold weather usage). Alternatively, you can buy no-name batteries for half that price on Aliexpress, or used batteries out of Prii.

A little bit more expensive than lead acid, but it should last longer.

[redpoint5]

Like lead acid batteries, NiMh can accept a little bit of trickle charging without becoming damaged too, so the charging strategy is more forgiving.

I like the suggestion.

[Ecky]

On the note of NiMH, several people over at InsightCentral have replaced their 12v battery with several of the Insight's NiMH sticks in series. Because hybrid battery NiMH cells/sticks are designed for high current, they make an excellent starter battery.

[redpoint5]

My brother-in-law gave his 2006 CBR600 F4i to me (I have 2 now), and it has only 3,400 miles on it (and he was the 2nd owner). It goes without saying the battery was dead.

I'm not finding a LiFePO4 battery that fits the small compartment that can also provide the cranking power needed to start the bike. I did find some cells rated at 7.2 Ah in a 32700 size. I assume they could withstand the brief spike to 100A to start the bike, I just don't know how I'll keep them balanced.

https://www.amazon.com/Tenberly-LiFe...6391101&sr=8-3

Then there's these supercaps that are rated for 3.8v. That means only 4 in series are needed. Perhaps 4x 220F in series would be a good option for starting the bike? The data sheet says it has 100 mOhm resistance and is only rated for 15 A peak, so perhaps not a good option. 100 mOhm seems high when others are <3

https://www.mouser.com/ProductDetail...jpzEOaSw%3D%3D

[Bicycle Bob]

Does the bike not have a kick starter? If not, a bump start is more fun anyway. You can delete the weight of the starter motor.

[serialk11r]

That's pretty weird, bikes are usually easy to start with a 7Ah battery. You can start most 4 cylinder cars with a 10Ah lead acid battery that's fully charged. Why not buy a 7-10Ah battery and see if it works first?

[redpoint5]

Originally Posted by Bicycle Bob

Does the bike not have a kick starter? If not, a bump start is more fun anyway. You can delete the weight of the starter motor.

It's a 400 lb street bike, so no kick start. In my (original) CBR600, I replaced the battery with 6s 400F capacitors and had no issues except for the 1 time I let a friend ride it, and he drained them by turning the engine off but keeping the headlight on. I was barely able to bump start going down a steep and long hill. Pretty sure you need some remaining voltage to get the bump start method to work.

Originally Posted by serialk11r

That's pretty weird, bikes are usually easy to start with a 7Ah battery. You can start most 4 cylinder cars with a 10Ah lead acid battery that's fully charged. Why not buy a 7-10Ah battery and see if it works first?

I bought a super cheap LiFePO4 battery and attempted to start the bike, but integrated into the BMS is overcurrent protection. It seems all of these cheap batteries contain this circuitry. I was hoping to find something with no circuitry, but no such luck... which is why buying the individual 7.2 Ah cells seems the best option at the moment.

... decided $31 to experiment is not too much. Placed the order, except it says shipping could take from 2-6 weeks. We'll see if the DMV can complete the title and registration on the motorcycle, or if I can build this LiFePO4 pack first. Not sure if I'll need to balance the cells... I've had a 20Ah LiFePO4 in a Prius since 2016 and never balanced it.

... in the meantime I'll get my supercaps going again in the motorcycle.

[serialk11r]

Yea, if you have a cheapo battery giving you problems, ultracapacitors will probably fix the issue. You bought hybrid ultracapacitors which are like halfway between a capacitor and a battery, so yes the internal resistance is higher, but you also have some current available from the battery to help it out, so it may work.

I've heard of quite a number of people complaining about BMS equipped batteries doing weird things to their cars, and my own lithium ion battery is also acting up, so I also bought a small ultracapacitor pack in hopes that it would make all the electrical issues go away. It's so small there's no appreciable self-discharge current, it can only help in starting the motor, and it weighs 100 grams so it can't really hurt.

[serialk11r]

Managed to test my theory today, here is my battery + ultracap setup:

All electrical issues gone! The engine seems to crank a little faster now but tbh it was already cranking very confidently with the lithium titanate battery so it's hard to tell. With lead acid the difference might be more noticeable.

[redpoint5]

Originally Posted by serialk11r

Managed to test my theory today, here is my battery + ultracap setup:

All electrical issues gone! The engine seems to crank a little faster now but tbh it was already cranking very confidently with the lithium titanate battery so it's hard to tell. With lead acid the difference might be more noticeable.

Is that the rear passenger-side area below the floor where the battery is located? Seems similar to where the Prius locates the battery, which makes it extremely easy to put a LiFePO4.

What are the specs on this build?

I'm continuing to use 7 Ah LiFePO4 batteries in the motorcycles, but haven't solved the problem of attaching durable positive and negative leads to them. I've got flimsy tin strips welded to them that are likely to fail with repeated bending.