Some amount of fear drives us all - all you have to do is handle it like a battery and keep in mind that it discharges a lot faster. There are a tremendous amount of caution and details in the thread over in the 6.0L forum.

12.7v today, it just keeps working.

 

I'm glad it's working out for you.

My concerns are more do with the capacitors explosively failing because they aren't evenly sharing the load. Preventing that takes some extra circuitry which I didn't see in your design.

Cheers!

 

The great debate, balancing or not.

So far, the bank does not require balancing circuit across the ultracapacitors. They balance across themselves as they charge and discharge, it is one of things I'm monitoring. From what I have observed so far, there is a slight voltage difference between individual ultra-capacitors on the initial charge due to manufacturing tolerances - that needs to be known. Once the bank is charged to say 14.2v, I measure again across individual after the bank has bounced back, say 20 minutes and an hour. There is plenty of head room between 14.2v and maximum. To date, three months in, the voltage differences between the individuals has never changed. Though now they are in the battery box it takes a few minutes to measure, I'm close to just letting it be.

A balancing circuit would add resistance and would balance to the lowest voltage in the series of connections - so far I see no need for that level of accuracy.

The manufacture of the ultra-capacitors also builds a Engine Starting Module out of these capacitors, they have six in series for 900 CCA or 2x of 6 in series for total 1800 CCA - no balancing in their offering, they do throttle the charging and they do isolate so that the bank can be charged higher than other batteries in the vehicle.

So far, the buffering offered by the drivers side battery is playing well with the ultra-capacitor. The govern of the alternator is no different now than in a two battery implementation - meaning the risk of run away alternator remains the same, no influence by the ultracapacitor bank.

So far, it looks like the quality of the manufacturing of the ultracapacitors has reached a point of negating the need for balancing in this implementation - so far there is no need to balance, obviously debatable topic.

It is a really fun experiment and I do not recommend for individuals unless they are willing to understand how a bolt of lightning works.

This is a great link towards the debate of balance vs. no balance;

https://www.tecategroup.com/ultracap...acitor-FAQ.php

 

I wouldn't use a resistor ladder in this scenario either even though it actually doesn't change the effective resistance of the capacitor bank. The active circuit in that link does give some hints of what's required though.

The capacitors will almost always balance nicely in a steady state and you won't be able to measure the differences between the cells. It's when they are charging or discharging that you will see the biggest differences but that's really hard to measure. Those difference will combine with the inductive voltage spikes to potentially exceed the voltage rating of the capacitors and damage them. A worst case scenario would be losing 1 capacitor which then takes out the whole bank. These effects are even more pronounced over a wide temperature range like we see in our trucks.

I can't comment on the engine starter module using super capacitors because I've never seen one. But the cheap lithium battery based ones they sell are a joke.

In the end it's your truck and it sounds like you've put some thought into it. I just wanted to point out to you and other reading this thread that it can be more complicated than it seems and to not repeat the mistakes I have made. I want to read about trucks pulling houses up mountains, not sitting on the side of the road!

Cheers!

 

I completely agree and welcome your comments. This adventure has been a tremendous learning experience and I'm not a EE, all I'm doing is trying to leverage what has been proven without without short circuiting my heart.

Even opening the box upon arrival, I was wearing rubber gloves and had my voltage meter at the ready - sure enough they came to me with a partial charge.

Even discharged it took all of my nerve to get close to the ultracapacitors with a wrench in my hand to tighten up the nuts. After that was the initial charge... Once I laid everything out and thought it through it was no problem, the ultracapacitor bank lived in a plastic bucket for many weeks until I had time to test on my old truck, then finally migrate everything into the 1U battery box.

By this time I was brave enough to treat it like a battery, obviously the discharge could be as fast as lightning so there is always that in the back of the mind.

Do you have any reference on a suitable balancing board?

I'm not about to build them myself, open to trying them though so far things see to remain in balance due to the headroom across the bank and the significant connections.

 

Yeah, it's the capacitor's low internal resistance that allows them to discharge and charge very quickly but it can also cause problems. For example, the worst case would be initially charging the capacitors from empty in the truck because it would briefly max out the charging system and the remaining battery by acting like a dead short. And as you know already, discharging them can weld metal.

Like you've found already the capacitor bank voltage will almost always be the same as the battery. That's because they will equalize with each other. If the capacitor voltage is higher than the battery it will charge the battery and vice versa. Even pulling a heavy load from them (like starting a truck) will keep them pretty close with each other. The capacitors will briefly provide a short burst of current until they are depleted (probably less than a second) and then the battery will take over providing most of the power as everything equalizes again. Since the capacitors can only store a small amount of energy compared the the battery the overall electrical system behaves like it has 1 "good" battery and 1 "bad".

I haven't used ultra capacitors at the currents that you will need here so I'm not sure if anything is readily available for stabilizing the voltages. You could add fusible links to your box though similar to what Ford does already. Circuit breakers would be too slow and big fuses are expensive.

Please keep in mind that I'm quite conservative with stuff like this because I'm an EE that used to design automotive and industrial (earth moving equipment, cranes, etc) electronics. I've had my share of hard lessons with batteries and capacitors which is why I thought I would comment on this thread.

Cheers!

 

Again thanks for your comments - All good. The initial charge of the ultra-capacitor bank was conducted on my bench with a 5amp charger of exactly those reasons - no way would I subject the truck computers and sensors to such a voltage variance. So the bank and the battery were basically at the same 13.5v as I installed into the truck.

Now as the truck alternator is managing the charging, the ultra-capacitor comes up to 14.2v within a minute of start and an at rest voltage is 12.5v to 12.7v after 60 minutes of the motor being turned off.

Trying for a KISS solution. I have an isolator on my bench but I can't see any reason to increase the number of components at this time, additionally my #1 objective is to leave the OEM cabling exactly as designed and an isolator would require that I bolt it together differently at the passenger battery terminal. BUT, an isolator would give me 14.2v dedicated to the starter though again, no need identified.

 

Yes agreed, BUT not so "bad".

In my testing on the 6.0L motor with a 6.4L starter(consumes more amps) I found that starting the motor only drew down the ultracapacitor bank by about 1.0v - so not dramatic.


Actual Results:

First Start from 13.7v super fast start resulting in 12.69v
Second Start from 12.69v super fast start resulting in 11.98v
Third Start from 11.98v was almost like normal speed resulting in 11.09v
Forth Start from 11.o9v was sluggish resulting in 9.53v, testing concluded here

Conditions:
32'F outside, motor temperature of 90'F from being plugged in all night, Starter from 6.4L, 2/0 dedicated cabling to starter

 

Questions:

My BMW X5 has a dedicated charging circuit for the monstrous AGM battery, so the battery is registered with the computer and the computer commands the charge rate. The charge circuit is separate from the starting circuit and things can get really confused if you connect any type of jump/charge cables directly to the battery - any external jump/charge has to flow through the BMW charge circuit to be recognized by the computer.

I'm operating under the base assumption that my Ford truck is not as sophisticated as my BMW - that the alternator is managing the the release of charge based on voltage only, not as a result of a circuit that is testing the condition of the individual batteries, not as a result of a circuit that is testing the condition of the combined in parallel batteries. There is a feed from the computer to the alternator that is on/off but that is all I am aware of...

Is my base assumption incorrect? I think I'm fine but I'm happy to learn otherwise.

 

I was using "good" and "bad" in terms of a lead acid battery. I would consider a battery "bad" if it only started the truck twice before dropping below 12V. I forget the exact numbers but I think healthy batteries hover between 12.3 to 12.8V? That's what I meant by the battery storing more energy than the capacitors

So in your test was everything in the truck powered by the battery EXCEPT for the starter? Did you try the same test with a known good battery?

 

Yes, most North American vehicles rely on the battery to self regulate their charge current. The regulator in the alternator just adjusts the output voltage based on temperature (or at least it should). If you draw more than the alternator can provide then the output voltage will go down.

Cheers!

 

Ok cool - thanks for the clarifications on "bad".

Yes - My testing was conducted with the ultracapacitor bank connected directly to the starter with 2/0 cabling of 6 feet - the starter was isolated with no other connection so no charging. The truck/motor/computers itself was powered by the normal truck batteries but not connected to the starter.

Unfortunately I did not conduct a similar test with a battery - I was relying on some results produced by another member who bought clamp on meters and was testing for improving the cabling on the 6.0L. Very good results that showed the starter amp draw across temperature conditions - I used that as baseline for understanding what we might be able to accomplish with the ultra-capacitor bank.

As soon as we determined that 6 caps in series could provide enough amps to turn the motor over, it became a quest to understand HOW MANY TIMES it could turn the motor over. Consensus settled on three times which was an acceptable amount of starts to proceed with placing the ultra-capacitor into the truck. Winter up here so it was cold as can be outside at that time.

 

Agreed - Thanks.

This is one of the reasons why I left the drivers side battery in place, it provides that buffering so that the circuit looks and behaves like an actual battery for the most part. Based upon the research I conducted, it looks like the ultra-capacitor will play well with a battery in the circuit and the battery can help to compensate for any loss over time - though you might tell me that the battery actually loses more voltage over time than the ultra-capacitor which is fine either way!!

Right now I drive the truck every weekend for all weekend trips, then on Wednesday I drive it to work - so good frequency and my at rest voltage is always 12.7v after resting for an hour.

The next real test is to let it sit for two weeks and then test the voltage, unfortunately that is not going to happen because I use the truck too much. Over winter I did leave the ultra-capacitor bank outside in a bucket(covered) so it had full expose to cold. During that month the voltage dropped like 0.5v, nothing in the greater scheme of things so I'm not worried.

I continue to learn!!

 

Tried a video, kind of lame but I'll replace it once I have a sunny day.

 

Received my second bank of Maxwell UltraCapacitors earlier today. Initiated the the initial charge on the bench and found one Capacitor that clearly did not accept energy as quickly as the rest. Thought on this for a while as I reviewed configurations for the truck.

I am in the process of replacing the aluminum connections with copper from an excellent source, thicker and better conductivity.

The last design approach was to place two ultracapacitors in parallel with each other so they balance each other, then connect that pair into series with the next pair. Great solution. My truck is not battery free as one battery needs to be in place for charge resistance, though it will be another week before I can finish replacing the aluminum connectors with copper, they will ship on Monday - once received I'll make another video of the battery free 6.4L.