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8 year old headway cells

Posted: Wed, 02 Mar 2016, 22:05
by offgridQLD
have several 8 year old Headway Gen 1 lifepo4 cells (some of there first cells available from headway) Purchased mid 2008 that have served many applications from powering daily used electric bike at high C discharge rates for several years. To jump starting diesel engines and running small 12v solar charged camping refrigerators for several months at a time. I can't say for sure how many cycles they have on them but it would be in the thousands. Over 1000 cycles just on the ebike.

Some times they had been discharged so heavily they get very warm...hot :? They also have been reconfigured several times and wires soldered directly to the cells. Along with several times being discharged below there designed min voltage...oooops and perhaps the odd over charge in the early experimental days. Over the last few years typically this small pack is stored in the shed near the tin wall on a bench and in high heat in summer. Oh and I forgot to mention the time it was powering a 30A electric outboard trolling motor on a kayak and was submerged in the water for a while after the tie down strap came loose :lol:

As I mentioned they have been abused to put it lightly.

Ok the test.

I charged the 4s 1p 10ah - 12v bank up on a balancing charger terminating the charge at 3.6vpr cell until the charge current dropped to almost nothing with all cells within 10mv of each other after balancing.

Now with the cells 100% full I programmed a discharge cycle at 2A rate 0.2C (the same as 4200w load on a 400ah 48v house bank)

The charger will monitor the capacity down to 8v or 2v pr cell. I will report back with the outcome.

Cells hot off the charge at 3.6v 100% full
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Cells under 2A load for discharge capacity test, fluke MM for min/max reference on the weakest cell.
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Under load 1/2 way though the discharge 5500mah
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I actually set it at 1.9A as you can see on the display in the previous photos and confirmed with the clamp meter in the pic below. I had already pressed start befor remember to set it at 2A. so 1.9A was the last time I used it. Anyhow it's a 0.19C discharge rate. In stationary storage comparison (offgrid home) terms. It's the equivalent of a 76A load on a 400ah 16 cell (53v) bank works out to 4000w load over the full DOD!
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final results.........drum roll
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9670mah for a full depth of discharge The cells where rated at 10AH nominal new so they have lost 3.3%.

Kurt

8 year old headway cells

Posted: Thu, 03 Mar 2016, 00:35
by Rusdy
Did I say wow? Anyway, WOW!!

I hope the newer manufactured cells haven't had any cost cutting regime.

I have panasonic cells (I assume NMC) for the last 2.5 years. Though not as abused as yours (definitely not as old!!), it has experienced hot summer in Perth (and stored in the hot shed to make it worse, full charged!!). Only 700 cycles so far (70% DoD in average). We'll see...

8 year old headway cells

Posted: Thu, 03 Mar 2016, 03:40
by offgridQLD
Yes they don't have the snap that they had brand new. As in they have more voltage sag under high loads than years ago. But still ok just higher internal resistance.

defiantly still very useful serviceable cells.

If anything I would say the Chinese cells have got better. These cells were some of Headways first. They actual came insulated in cheap cardboard. Like the old AA and D alkaline cells of the 80's. I took that off and put heat shrink on them.

If you have a good brand name cell like Panasonic or most cells from Japan or a modern Chinese cell and treat them well I would expect very good service life.

Kurt

8 year old headway cells

Posted: Thu, 03 Mar 2016, 14:52
by Johny
Wow - great data Kurt. I have a special interest as my car is powered by 384 of the Headway 38120S cells. After 21,500 km (3 years daily) I still can't measure any degradation using OCV after 1-2Hrs discharge rest at about 50 SOC. (I get the same value as I got 3 years ago).

8 year old headway cells

Posted: Thu, 03 Mar 2016, 16:19
by T1 Terry
Certainly a great plug for their durability and gives me another option for my future battery pack. What would the peak C rated load have been when they were in the electric bike?

T1 Terry

8 year old headway cells

Posted: Thu, 03 Mar 2016, 16:45
by offgridQLD
The electric commuter bike had a large 5304 hub motor with a controller set at 50amps. The headway cells where configured as 2p so 20ah at 36v.

2.5c load . Heavy bike, lots of hills and towing a trailer with child on board.

This particular taped up 4 cells once removed from the bike bank has been the go to pack for 12v needs. It's seen some silly loads like 200Amps starting engines. Ran a high output 12v compressor and finishing gun for weeks trimming the exterior of a few homes (my shop air compressor is to heavy to move off location)

It gets a lot of use each summer on my electric kayak 30amp 3c max load but typically 15amp 1.5c. Not uncommon to do 5 or more cycles a day when we are camping near water. Pv charging it at over 1c and discharging it in about 30 min.

I think headway cells are great. They were very inexpensive when I imported about 60 odd cells back then as you were dealing directly with them. Now the name is a bit more established and price reflects that.

Kurt