7.2V 6500mah/10000mah replacement battery stick for Honda Civic and Insight 2003-2005

[Eli]

I left the bottom axis out because it's just the number of excel rows, but yeah, time.

[samwichse]

I'm seeing some high IR numbers in the future... total capacity looks amazing.

Originally Posted by Eli

First impressions:

Good capacity. Impressive, even.



However, the graph gives us some clues of the things to come..

Stay tuned!

[Eli]

I'm too impatient to run a few more cycles and need to get some other things done, and I know you're all waiting in suspense , so I'll spill the beans:

These cells would be awesome in an application that required say, 25A charge and 50A discharges. Maybe. Their capacity is indeed quite respectable.

However, that is where it ends. Their internal resistance is, unfortunately, a deal breaker. I calculate it at about 4.0 milliohms; twice that of a brand new Honda cell, if you could find one, and almost 3x as much as a MaxIMA cell.

Shockingly, the cell was able to sustain a 50A charge from 0% SoC without venting.. once, at least. The cell hit 1.7V after less than 1,000mAh input. The cell was 150F by the time the charge stopped after over 9,500mAh input.

It took another 2500mAh at 1A to top the cell off. Much of the above 9500mAh input was burned off as heat due to the high IR.

In a car, the high internal resistance would be perceived as low capacity. It doesn't matter what the batteries capacity is, the BCM will begin aggressively reducing regen at 192V, or 1.6V per cell. These cells hit that almost immediately. This would trigger an early positive recal and most likely an IMA light. I'm not sure if I believe these are actually in use in a car. If they are, it must be right on the edge of an IMA light.

Looks like Ron was right, but of course we all suspected... "If it's too good to be true, ....".

[2Slow4u]

Thanks for your input Eli, appreciated as always.

I agree with your analysis. The high internal resistance will cause performance, efficiency, temperature, and ultimately cycle life issues.

Can you provide us with a Wh and Wh/kg comparison between the three cells?

How about some charge curves to demonstrate the premature CC-CV issue you mentioned?

[husseycm]

Originally Posted by Eli

I'm too impatient to run a few more cycles and need to get some other things done, and I know you're all waiting in suspense , so I'll spill the beans:

These cells would be awesome in an application that required say, 25A charge and 50A discharges. Maybe. Their capacity is indeed quite respectable.

However, that is where it ends. Their internal resistance is, unfortunately, a deal breaker. I calculate it at about 4.0 milliohms; twice that of a brand new Honda cell, if you could find one, and almost 3x as much as a MaxIMA cell.

Shockingly, the cell was able to sustain a 50A charge from 0% SoC without venting.. once, at least. The cell hit 1.7V after less than 1,000mAh input. The cell was 150F by the time the charge stopped after over 9,500mAh input.

It took another 2500mAh at 1A to top the cell off. Much of the above 9500mAh input was burned off as heat due to the high IR.

In a car, the high internal resistance would be perceived as low capacity. It doesn't matter what the batteries capacity is, the BCM will begin aggressively reducing regen at 192V, or 1.6V per cell. These cells hit that almost immediately. This would trigger an early positive recal and most likely an IMA light. I'm not sure if I believe these are actually in use in a car. If they are, it must be right on the edge of an IMA light.

Looks like Ron was right, but of course we all suspected... "If it's too good to be true, ....".

What numbers did you use to come up with an internal resistance value of 4 m-ohm?

What temp would a honda cell be after a full charge at 50 amps?

[2Slow4u]

He probably used the voltage response from his load testing to calculate the DC resistance, most manufacturers out of asia will provide the AC impedance and use that as the resistance value.

DC resistance is what really matters, since this is a DC system...

V_delta = I*R

[samwichse]

20 of these would make a mighty nice ebike pack, that's for sure. 24v * 50a is 1.2kw (probably around 1kw after sag), enough to really get you cranking up hills... about 3.3kg of weight for that. I wonder if they do custom length sticks... 4 5cell sticks would fit nicely on top of a standard rear wheel rack.

[Eli]

Gotta give the little guy credit. Just got 11,000mAh out of the cell.....

...By bringing the cell down to 0.1V. Average discharge voltage was a scant 0.75V and average discharge current a mere 56A(85A peak). The cell once again reached over 150F, but did not vent.

These would be amazing cells if their internal resistance was 3x lower.

For comparison, a MaxIMA cell will have an average discharge voltage of about 1.075V at an average current of 56A(70A peak) and will reach a rather frigid ~100F, in comparison.

I might play with them a little more, mostly because I really want to make one pop(maybe they left out the safety valve and that's why they can take the abuse?) but I'm pretty much done... Cycle life in these conditions is going to be abysmal at best and I would be surprised if you could get 1,000 miles without a code in the real world.

I've yet to see a bad stock cell over about 5 milliohms of IR, though I admittedly haven't been looking too hard.. so these cells are right on the edge from the start.

That is obviously never going to be allowed to happen in the real world. 1.7V is the maximum my equipment can read; actual cell voltage was closer to 2V which is way, wayyyy too high.



Wow, look at all that capacity! Let's zoom in a little and see what the car would actually be able to use...





Ah crap. I just got a negative recal after an 80A assist burst. X-axis is pretty much seconds, so there's a very generous 1500mAh right there before hitting 1.0V. The car would be pretty unhappy about this.

[MN Driver]

Almost looks like two of these packs put in parallel might be a good way to get a high capacity pack that might survive, if it is treated gently for someone who wanted to connect something like to this MIMA. The welds would need to be strong enough and it might take more testing. Of course with high IR you'd have a short life if you regularly flog your pack or drive all over in the city cycling the assist and regen back and forth all day. Then again maybe the thermal cutback would help but the PTC strips are more needed than ever.

Of course, all outside observer speculation. On an unrelated to Insights but more related to how I'd use them, I think they look great for a lower amperage high voltage ebike setup, electric lawn mower, electric snowblower, or something else where the current is generally lower. Old high IR, high self-discharge Honda sticks work great on my electric mower as long as I recharge prior to mowing each time instead of after.

[samwichse]

This is an interesting idea... a primary + buddy pack with these sticks would give you 20ah * 144v ~ 2.8kw pack... a buddy pack install seems like it would be way easier to do than the lithium mods people have proposed, as the car can keep using all the stock electronics, you just need to strap a spare battery casing full of cells down in the back cargo area and hook up the main leads in parallel. Probably need a cooling fan too.

Add a grid charger and MIMA and you've got a nice 2.8kwh plug in hybrid!

Sam

Originally Posted by MN Driver

Almost looks like two of these packs put in parallel might be a good way to get a high capacity pack that might survive, if it is treated gently for someone who wanted to connect something like to this MIMA. The welds would need to be strong enough and it might take more testing. Of course with high IR you'd have a short life if you regularly flog your pack or drive all over in the city cycling the assist and regen back and forth all day. Then again maybe the thermal cutback would help but the PTC strips are more needed than ever.

Of course, all outside observer speculation. On an unrelated to Insights but more related to how I'd use them, I think they look great for a lower amperage high voltage ebike setup, electric lawn mower, electric snowblower, or something else where the current is generally lower. Old high IR, high self-discharge Honda sticks work great on my electric mower as long as I recharge prior to mowing each time instead of after.