[redpoint5]

See this thread for updates on my battery replacement project.

I worked on my truck yesterday and found that the parasitic drain was 45mA, not 20mA like I had thought. The backlit thermometer that was wired directly to the battery was responsible for 39mA of that!

After removing the thermometer, the truck had a parasitic drain of only 5.89mA. This drain is likely entirely due to the aftermarket radio since the truck doesn't have any power features. I removed the faceplate of the radio to see if drain further reduced, which it did by a measly 0.3mA. Interestingly, I noticed periodic spikes to 11mA after removing the faceplate, and found this was due to an anti-theft LED that blinks with the faceplate removed.

Using 3000F capacitors, I could let the truck sit for 4 days before needing a boost. Combined with my 4.2Ah LiFePO4 pack, I could go for 3 weeks. If I were to use your 10Ah batteries instead, I could let the truck sit for almost 2 months!

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.

A 1W panel like this is probably more appropriate. At 85mA peak output, it would likely not over-run the balance LEDs on the capacitor bank.

Originally Posted by Enki

Does the Hobbyking pack have an integrated charge/balancing controller? If not, and if the $18 cells remain relatively balanced, a set of four of those with a bank of 650s would probably be downright amazing.

My mistake on the price of the Hobbyking pack. It's $40, but shipping was $27! It doesn't have integrated balancing, but it does have balance leads, and I purchased a balance charger for $27 and a quick connect voltmeter for $2 that gives the voltage of each cell.

The 8.4 Ah pack has a burst discharge rating of 336A!

Originally Posted by serialk11r

Enki have you considered pairing the motorcycle battery with a small cap bank?

That would be likely be unnecessary. I'm running just a set of 6x 400F capacitors on my motorcycle, but could easily replace them with just a 4.2Ah LiFePO4 battery. My bike only takes 70A to start, which is easily supplied by only a LiFePO4 battery. Besides, the battery compartment in motorcycles is extremely small. I couldn't fit both a capacitor bank and a small battery in my bike.

My recommendation for all motorcyclists is to run a single 4.2Ah LiFePO4 battery. My bike has a parasitic drain of 1.25mA, which means that a 4.2Ah battery has enough reserve to sit for over 100 days without being charged, and still start the bike with no damage to the battery. That means it could sit all winter without any maintenance and would still be in top shape in the spring.

At $40 for the LiFePO4 battery, nobody should be buying a lead-acid battery for their bike.

My own plan is to go for a Deka ETX12 battery next time around (so a little less than half the capacity of stock), lead acid since I feel like there's no reason to put that big of an investment in at this point, and 6 400F ish capacitors. If it can start a V8 it can surely start my wimpy 1.8L 4 banger. The smaller capacitors will also bleed less current which will help.

Have you measured the parasitic drain on your car? The Deka ETX12 only has 10Ah, of which probably only 4Ah is usable before you cause damage to it. It also weighs 12 lbs and costs a minimum of $40. I'd go LiFePO4 instead because it's much lighter, costs the same, and you can use most of the capacity without causing damage. It should last longer too.