Supercapacitor Battery Replacement

[Nautilus]

Standby drain leaves the supercaps dead after short time. Nippon 700F caps, if left alone and not connected to anything, drop from 14.8 V to 9.45 V in just 48 hours. They still drain even if connected to a battery, but very slowly, in weeks or even more. And this disregarding the consumers on the car: alarm, locks, ECU memory, gasoline pump, radiator fans which still run 5 to 10 minutes after engine shutoff and draw at least 16-17 amps.

So supercaps are not efficient if left alone, only if connected in parallel to a small, lightweight auxiliary battery.

Motorcycle batteries fit together with supercaps in the box and they're small and light enough.

Tested the system leaving the car untouched for 38 hours in dry freezing weather. It cranked to start at -5°C, no problem. There was some freezing on the gas lines, so it took 5-6 seconds of cranking. Instead of 1 second as usual when the car is daily driven.

Battery can supply in theory about 175 CCAs, so it may give (one) start by itself if a connection breaks.

The supercaps charge and discharge instantly, as they don't rely on a chemical reaction, so they smooth out voltage. As the small milifarad caps in the Raizin voltage stabilizers do, but on a grander scale. This gives the smoother idle and stable voltage.

I had an array of solar panels over the trunk lid, lighted by the Sun through the rear window, which I've fitted to power up a system of fans to cool the interior on hot days. Added a wire and a cigarette lighter plug, to connect them into the car's electric system in cold weather and keep the battery/supercap hybrid topped up. They are rated to about 634mA in open air and ideal conditions, but in less than good position and under the green anti-UV window they give only about 65% of their nominal amps. That is, a bit over 400 mA, which is pretty close to what a battery trickle charger does.

[teoman]

Redpoint,

would you have pictures of your 3400F setup? Especially the balancing circuit.

Also what would you recommend for an R1200GS?

[Enki]

Originally Posted by Nautilus

Standby drain leaves the supercaps dead after short time. Nippon 700F caps, if left alone and not connected to anything, drop from 14.8 V to 9.45 V in just 48 hours.

That seems pretty high to me; if I remember to, I'll go check my deathbox voltages tomorrow, but after a few charge/leakdown cycles they pretty much stopped draining themselves a bunch. Is your balancing circuit just a set of resistors and diodes? That might be a cause right there; I have nothing on mine right now.

[redpoint5]

Originally Posted by serialk11r

It is approximately 10Ah for 150 bucks, which is a great deal.

That price looks normal to me. I bought 4x 20 Ah prismatic cells for $140. It's in my Prius right now, with no balance circuit.


http://www.batteryspace.com/lifepo4-...assed-dgr.aspx

Batteryspace has the "lead-acid" replacement batteries with balance circuitry for a similar price.

http://www.batteryspace.com/Li-Ion-B...Batteries.aspx

Originally Posted by Nautilus

Standby drain leaves the supercaps dead after short time. Nippon 700F caps, if left alone and not connected to anything, drop from 14.8 V to 9.45 V in just 48 hours. They still drain even if connected to a battery, but very slowly, in weeks or even more. And this disregarding the consumers on the car: alarm, locks, ECU memory, gasoline pump, radiator fans which still run 5 to 10 minutes after engine shutoff and draw at least 16-17 amps.

So supercaps are not efficient if left alone, only if connected in parallel to a small, lightweight auxiliary battery.

Motorcycle batteries fit together with supercaps in the box and they're small and light enough.

There is a defect if you are experiencing that much capacity loss, either in the caps themselves, or in the balance circuitry employed. Even with constant light emitted from a crude LED and diode balance circuit, my caps go for months with just a volt or 2 of loss. Without the balance circuitry, they can go much longer.

The real issue, as you pointed out, is parasitic drain from the vehicles electronics. This should be measured before designing a battery replacement. Motorcycles are the perfect application because they are most sensitive to weight, and tend to have low parasitic draw. Combining with a small LiFePO4 battery will give the standby capacity needed.

Originally Posted by teoman

Redpoint,

would you have pictures of your 3400F setup? Especially the balancing circuit.

Also what would you recommend for an R1200GS?

I'll snap some photos later, but there isn't much to see. The 5 caps are just held together by aluminum bus bars and nuts in series. Then I put them in a styrofoam box I crudely built. No balance circuitry. I think I've got 4 awg leads.

I'm running 6x 400 farad caps alone on my CBR600, and it starts every time. You have very little time to waste in starting the bike once you turn the ignition on, and only 1 shot to start. I have no problem with this in daily use, but if the bike sits for more than 3 days, I have to put it on the trickle charger or else it won't start on the 4th day. I'm willing to put up with these limitations since bump starting is always an option if the caps ever did fail to start the bike.

The practical solution I would run on your bike is a 4.2 Ah LiFePO4 battery, perhaps in parallel with a 350 F capacitor bank. It would be good to know what the parasitic drain on your bike is, or perhaps what the capacity of the OEM battery is, but this should be adequate.

https://hobbyking.com/en_us/zippy-fl...epo4-pack.html

This is what I would build:

https://www.youtube.com/watch?v=8miq6sDy0wA

[Nautilus]

Originally Posted by redpoint5

There is a defect if you are experiencing that much capacity loss, either in the caps themselves, or in the balance circuitry employed. Even with constant light emitted from a crude LED and diode balance circuit, my caps go for months with just a volt or 2 of loss. Without the balance circuitry, they can go much longer.

The real issue, as you pointed out, is parasitic drain from the vehicles electronics. This should be measured before designing a battery replacement. Motorcycles are the perfect application because they are most sensitive to weight, and tend to have low parasitic draw. Combining with a small LiFePO4 battery will give the standby capacity needed.

This is very much possible. Balance circuits are factory made, they employ a small IC with a power transistor and resistors. Alternator makes 14.2 volts engine hot, 14.4 volts engine warm, 14.6 volts engine cold. The maximum experienced were 14.8 volts, in freezing temps, just after engine start. This is measured at the OBDII port, not battery terminals.

Nippon supercaps are rated to 2.5 volts each normally (15V in series) and 2.7 volts maximum possible (16.2V). Fully assembled with the circuits, they are within a maximum 0.24V difference. Strongest at ~2.44V, weakest at ~2.20V. Circuit boards are designed to not allow a cap go above 2.5V. So the circuits may be dropped altogether to save energy.

Lithium batteries are barely usable at freezing temps. Even high tech Varley Lithium are rated by factory for no less than -10°C (14°F).

So the battery has to be a lead-acid for robustness. The cheap 10Ah AGM I've used had no issues in -5°C to -6°C. But gave up at -11°C. It drained to zero and could not hold a charge. Tried to jump start the car, supercaps charged a little and cranked for about 3 seconds. Battery still dead. Tried again to jump start, left the engine to run until the coolant reached normal running temps, stopped, voltage dropped at once to 9.2V and then slowly to zero. Most likely the battery, which had been for many months in the shop and had no manufacture date sticker, had been sulfated. And much too diluted electrolyte froze.

So the next step is a new, properly made and charged AGM from a reputable brand, no more than 4 kg in weight.

[ECONORAM]

Originally Posted by redpoint5

I found that my 2.5W solar battery maintainer is totally inappropriate for maintaining the charge of my 350F (58F series) capacitors. With overcast sky, the panel put out 40mA of charge, and in direct sun late in the evening (6pm) I managed 140mA. It could probably peak at 200mA in direct noon sun. When I checked on the state of charge, my bank of 6 series 350F capacitors were charged to 16.02v and rising. The balance LEDs were beaming brightly trying to dissipate the extra charge, but were being over-run by the solar panel.

I was about to ask if a solar charging panel would work instead of another battery. Would you need a voltage regulator in the circuit for sunny days?

Originally Posted by Nautilus

Lithium batteries are barely usable at freezing temps. Even high tech Varley Lithium are rated by factory for no less than -10°C (14°F).

Didn't know that. Good to know as I'm considering pulling out my Diehard to stick a super-cap pack in it's place.

Originally Posted by Nautilus

Having found out Laserhacker's experiment back in 2014, I've tried to replicate it myself. The foremost purpose was weight balance in the car - as the battery, originally 60Ah and over 15kg / 33lbs, is at the extreme front end, outside the wheelbase, and any sizable weight reduction here decreases the polar moment on inertia and therefore the understeering.

Glad you mentioned this. My wife's car has the battery sitting in front of the front wheel, at least it's mounted low. My truck's is forward of the front wheel, but about 4 feet off the ground.

[redpoint5]

Originally Posted by Nautilus

This is very much possible. Balance circuits are factory made, they employ a small IC with a power transistor and resistors. ...So the circuits may be dropped altogether to save energy.

Lithium batteries are barely usable at freezing temps. Even high tech Varley Lithium are rated by factory for no less than -10°C (14°F).

The cheap 10Ah AGM I've used had no issues in -5°C to -6°C. But gave up at -11°C.

My guess is that either your balance circuit or a defective cap is placing too much parasitic draw on your battery, which then damaged it (your AGM might have a short). You shouldn't be losing so much voltage in such a quick amount of time on a supercap pack when it isn't connected to the vehicle. Like I said, my supercap can go months and only loose 1 volt, and that's with an LED balance circuit. Correct this problem first, or damage might result on the replacement battery.

I have a LiFePO4 pack in my Prius as an experiment. The allowable charge rate is very low when it's below freezing. Fortunately the battery is located inside of the passenger cabin, and I park inside a garage that never goes below freezing. Relocating a small lithium battery inside the passenger compartment might be a viable solution. Another solution is to place a current limiting resistor in series with the lithium battery to limit the charge rate to something safe when below freezing. The super caps would do almost 100% of the work of starting the engine, and the lithium battery would maintain voltage when the vehicle is parked.

Originally Posted by ECONORAM

I was about to ask if a solar charging panel would work instead of another battery. Would you need a voltage regulator in the circuit for sunny days?

Yes, and that was my plan for the truck, which has an extremely low parasitic draw (7mA). It's absolutely critical to have a working balance circuit on the supercaps because the solar panel doesn't limit output voltage when the caps reach their rated capacity. Capacitors by themselves have no way to bleed off excess charge, and instead just self-destruct. LiFePO4 is similar, and must have some means of bleeding excess charge if connected to a solar panel.

NiCad, NiMh, and lead-acid all have the ability to bleed off excessive trickle charge, and should be fine with an appropriately sized solar panel.

Combining a small lead acid battery with supercaps is a good way to limit voltage to the supercaps since the battery can waste excess charge if you want to also use a solar panel.

[Nautilus]

Supercap / battery hybrid did not drop voltage before. Even when left parked for 38 hours in -5°C weather, still held ~12.5 volts and gave a start. It died suddenly when outside temps dropped to -11°C, no warning.

Only the supercap array lost voltage, when charged and left with no battery attached.

Can't the supercaps run with no balancer at all, as long as alternator voltage doesn't climb over 14.7 volts overall?

[gumby79]

How well would a suppercap setup handle the 200A grid heater that runs for 1-2.5min at -20°f,and then start. My brand new groop31 is unable to accomplish this.

[Enki]

Not very well. Cap banks can supply a lot of instant amperage but the voltage drops off quickly at high loads. Think about it like this: Each cap in my 500 farad cap bank (huge; they are 2.7v 3000 farad caps) holds about the same overall energy as a AA battery.

If you need to power something for a long time, you need chemistry. If you want to hit something with a lot of power for a very short time, you need capacitance.