Lithium-ion 12v Battery Replacement

[redpoint5]

I made a very crude spreadsheet that calculates all this. It's on the tab titled "Cap Calculator".

https://docs.google.com/spreadsheets...it?usp=sharing

From experience, 6 series connected 350F caps can easily start my TSX. 400F should easily start your lower rated starter.

[Ecky]

Thanks. In your spreadsheet, I noted the following:

Typical car starting draw 570 A/s = 0.158 Ah

BCAP400, Usable Ah = 0.093

If I'm reading this correctly, the caps do not contain enough energy to start the car once?

[redpoint5]

It's been a while since I looked at this, and my guess is someone has changed something, because my values were never negative when I ran my scenarios.

Ah is a poor way to measure power draw anyhow, because voltage is never constant. I need to come up with a better formula that factors in the fact that voltage decreases over time, which decreases delivered power. All that matters is that the quantity of energy needed to start the engine is met by the quantity of energy contained in the capacitor bank. I should probably be calculating this stuff in Joules.

[teoman]

0.158Ah assuming it lasts a second.

But the energy us d to create the momentum of the engine is not lost.

[Ecky]

Originally Posted by teoman

0.158Ah assuming it lasts a second.

But the energy us d to create the momentum of the engine is not lost.

I've looked at graphs of starter motors, current peaks as high as 5-700 amps momentarily while the motor struggles from stall.

Anyway proof will be in whether it works.

[RedDevil]

The current through the starter motor will initially be high, but drops off almost immediately when the motor spins.
Starter Motors and Circuits (Automobile)

For a light vehicle engine, a typical cranking current is around 150 A, which may increase to the order of 500 A to provide the initial stalled torque.

[hayden55]

Not to high jack but Red point how do you like the PiP? Somebody hit my car again and it may be time to get another Prius. With your kill a watt how many watts/mi do you get around town? I typically stay under 45 mph and don't use any HVAC. I'm really looking into building an extension for the pack on one and seeing if I can get all my city miles electric. Whats the fastest it will charge at? Looking at using a 240v 60a circuit for the charger.

[redpoint5]

Originally Posted by hayden55

Not to high jack but Red point how do you like the PiP? Somebody hit my car again and it may be time to get another Prius. With your kill a watt how many watts/mi do you get around town? I typically stay under 45 mph and don't use any HVAC. I'm really looking into building an extension for the pack on one and seeing if I can get all my city miles electric. Whats the fastest it will charge at? Looking at using a 240v 60a circuit for the charger.

I love my Prius, but I think there are better options out there. It has something like a 3.0 kWh usable battery, which equates to about 12 miles of range. That's not enough to do most trips on all EV. I'm at 30% EV miles, and 70% hybrid.

The Ford Energi models get a little over 20 miles per charge, and the C-Max is fantastic. Better in every way except slightly lower MPG. I'm a huge fan of the Fusion if you're ok with a sedan.

The Prius charges at 2,880 watts on 240 with an appropriate EVSE. The OEM EVSE only uses 120v unless you modify it (1,440 watts). That's a 1.5 hr charge on 240v and about a 2.5hr charge on 120v.

In the worst of winter conditions I might only get 10 miles of range, and in the summer 16.

[Ecky]

Looks like my 12v lead acid battery has had a very timely demise - this morning it was 15 degrees, and my car wouldn't start using the starter. Rolled it down a hill and dropped the clutch to get to work, but I need this up and going soon.

These look promising to run in parallel with the caps:

https://www.batteryspace.com/li-ion-...lead-acid.aspx

There's a 20ah pack for $130, and one with an LED balancing circuit for $190. Thoughts?

[redpoint5]

Originally Posted by Ecky

Looks like my 12v lead acid battery has had a very timely demise - this morning it was 15 degrees, and my car wouldn't start using the starter. Rolled it down a hill and dropped the clutch to get to work, but I need this up and going soon.

These look promising to run in parallel with the caps:

https://www.batteryspace.com/li-ion-...lead-acid.aspx

There's a 20ah pack for $130, and one with an LED balancing circuit for $190. Thoughts?

I've got 2 of those batteries, and wired in balance leads, but don't have active balancing. I can throw the battery on my balance charger if I ever need to, and I have a cheap voltage reader that I can connect to get a quick read on the individual cell voltages.

One battery has been in my Prius for 2 years, and the other I keep around for experiments or in my jetski during the summer.

It could probably crank a 4-cylinder engine by itself, and I start my 2-stroke jetski with it.

The problem is that the battery is not supposed to be charged when below freezing. I think it can be charged at extremely slow rates below freezing, but how would one regulate that?

It drops below freezing in the Portland area, but my Prius lives in a garage, and the battery compartment is in the cabin. I don't think the battery ever actually sees freezing temperatures, so I feel confident it will last a long time. That said, I'm not so sure it would hold up to underhood temperatures; especially when well below freezing.

There's usually a code for 10% off if you search online, which basically covers shipping.