Maxwell Technology Ultracapacitor and ESM Ultra

[Hillbilly Heaven]

I came across Maxwell Technology while looking at a different project. At first I past it off as another one of those Audio capacitor banks Mobile Audiophiles use for their amplifiers.

Well it is but it isn't. They offer capacitor type banks and engine starting modules. My power system is designed around 3 batteries since I have the room. Two under the hood. One for starting and running loads, the second is for winching and recovery also backup to the first for starting. The third battery in the rear is for Inverter and Fridge use. All 3 are identical Group 31 batteries. They ultracapacitors and modules are not cheap but when compared over the lifetime as cost per month vs a battery the Maxwell's cost less.

When time comes for replacement I might consider upgrading to Maxwell's and do a comparison. My thought is to replace the two batteries under the hood with ESM 31/1800. These have separate terminals for starter load and running load. Recharge time is very quick when running a 150-200 amp alternator. The 2nd ESM could be setup for the winch and jumper cable to the start terminal and auxiliary loads to run terminal. The first ESM could be setup for engine start and run loads. The third battery in the back could be replaced with the 16 volt 500 Farad BMOD0500. No changes would be required to make use of these. Hopefully by the time I will need them the price will come down. They are about $500-600 each. An Odyssey Group 31 battery cost about $300-400.

Just thought someone else may have an opinion or experience using something like these.

ESM31/1800 Engine Start Module
http://www.maxwell.com/products/esm/esm-ultra-31-1800

BMOD0500 Ultracapacitor 16 Volt 500 Farad module
http://www.maxwell.com/products/ultracapacitors/16v-large-modules

 

[rkfoote]

Ultra Capacitors are fantastic for high load / fast cycling. However the capacity is very very low. For example, the ultra-31-1800 states 1800 amps @ 3 seconds. If my math is correct that is about 18Wh. A 100Ah lead acid is around 1200Wh. It's kinda like the difference between a 5 gallon bucket of water vs a garden hose hooked up to a tanker. The 5 gallon bucket will get you wetter faster, but the garden hose will run all day.

 

[Hillbilly Heaven]

True that is why it is listed as engine start battery. Great at quick high current demand and recharge but not for use like a typical deep cycle battery. I don't think any of my battery usage would qualify as deep cycle even with the inverter.

 

[rruff]

When time comes for replacement I might consider upgrading to Maxwell's and do a comparison. My thought is to replace the two batteries under the hood with ESM 31/1800. These have separate terminals for starter load and running load. Recharge time is very quick when running a 150-200 amp alternator. The 2nd ESM could be setup for the winch and jumper cable to the start terminal and auxiliary loads to run terminal. The first ESM could be setup for engine start and run loads. The third battery in the back could be replaced with the 16 volt 500 Farad BMOD0500. No changes would be required to make use of these. Hopefully by the time I will need them the price will come down. They are about $500-600 each. An Odyssey Group 31 battery cost about $300-400.

Why not just buy 3 (or maybe 2 is enough?) deep cycle batteries hooked together, and have them do everything? The capacitor only works for starting, and the other batteries can easily handle that job.

 

[rkfoote]

Ultra Cap is great for starting, but that's about it. Leave your headlights on for 15 minutes and it will be completely flat. Winching would be downright scary. Per warn's website: https://www.warn.com/truck/winches/XD9000i.jsp you can draw up to 500 amps. The cap would be empty within seconds and you'd be relying 100% on your alternator.

 

[Hillbilly Heaven]

Yes it would take a modification of habits used with typical batteries. Winching even with both ESM (almost called them batteries) connected together may take some doing. It could get aggravating having to pause for 15-30 minutes or more, depending on alternator size, for ESMs to recover. It will take more thinking before making the jump but I have at least hopefully two more years of life left on the batteries I have now. By then there maybe more and different options.

 

[dwh]

Winches have a duty cycle and cool off period. If you're pulling hard enough to draw 500a, you'd need to let the winch cool off anyway.

Or, rig snatch blocks. More likely, both.

 

[Hillbilly Heaven]

I didn't think to check the datasheet to see if it listed self discharge rate. If it acts like a capacitor and is isolated self discharge rate should be zero or very close to it.

 

[Rando]

Capacitors aren't really going to work for this application - the 500F module you linked to only has an energy capacity of about 1Ah @12V. Secondly the voltage on a capacitor drops linearly with energy. So if you use half your energy you are left with half the voltage.

 

[Hillbilly Heaven]

Maybe I should be clearer about the use of the 500 farad module. Currently have a 3rd group 31 battery mounted in the rear. It is used mostly for powering fridge and comms gear. I plan on adding an inverter, probably something around 1750 watts. Use of inverter would be short term usage mainly coffee pot or induction cook surface for quick cup of coffee and a little breakfast so I don't have to fire up the stove.

Thought is to give up the 3rd battery and replace it with the 500 Farad module mounted in rear and connected to 2nd battery or 2nd ESM. This would average the load seen on the system.

Just dawned on me that the best way to incorporate all this is a hybrid type system. ESM 31/1800 for engine start and vehicle running loads. An AGM type Group 31 battery also mounted under the hood combined with the 500 Farad mounted in the back. This would eliminate the need for the isolator needed for third battery, would still need circuit protection at each end between battery and capacitor.

 

[rkfoote]

All things being equal, just pretend that the capacitor _is_ a battery. (just a battery with some different characteristics).

*** DISCLAIMER, all the numbers below are estimates. We're really talking about orders of magnitude, so be kind with my estimates ***

If I understand your current setup, you have 3x type 31 batteries (with various isolation methods in place). This gives you ~300ah of total capacity (~150ah if you're careful not to run below 50% for charging and longevity of the batteries).
Per ARB's website, a 50 quart fridge draws ~ 1.35a per hour @ 12v, so you can run a fridge for 222 hours (9 days) before going flat.
A 1000 watt coffee maker would run around 3.5 hours before flat.
A 110 watt headlights (55w * 2) would run for ~33 hours

If you replace all 3 batteries with ultra caps, you'll end up with ~ (2ah * 2 (1000f) + 1ah (500f)), or 5ah in total.
ARB 50 quart fridge draws ~ 1.35a per hour @ 12v, so you can run a fridge for 3.7 hours before going flat.
A 1000 watt coffee maker would run around 3.6 minutes before flat.
A 110 watt headlights (55w * 2) would run for ~32 minutes

In these scenarios there is no advantage for ultra caps. All of your loads are relatively small loads that you want to draw for long periods of time. Even replacing 1 battery (starter) with the ultra cap drops your usable capacity by 1/3. You'd be better off buying a high quality isolator in my opinion.