The Peak Jump Start

[svetz]

Time for a discharge test of my 400Wh test pack! Yep, it’s housed in that old Peak Jump Start. It was dead in the garage collecting dust… but 20 new 32700 cells in a 4s5p configuration replaced the old 18 Ah (216 Wh) LA battery and has brought it to life again. It sure is lighter with Lithium. Haven't used it to jump cars (not sure my soldering would hold up), primarily it's to run the inverter to power stuff away from the house.

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20 cells x 3.2v x 6.5 Ah = 416Wh, although at 90% that’s ~374Wh. At the time I purchased the LiitoKala cells, the price was $176/kWh. Before @robaroni I'd only heard bad things about them, but on paper they looked good so I figured what the heck. Basically, this just was a learning experience, that I got something useful out of it is a plus. Been learning a lot from Will's site, so not sure what I'll do next.

Using the Jump Start was an afterthought (originally I was going to scavenge it for parts), as you can see it already had a DC switch, LED gauge, LED lights, USB port, a handy case, and handy alligator clips. But after I took it apart I saw I could just re-purpose it rather than scavenging it for parts.

It’s been resting for about 2 weeks, on disassembly the cells were slightly discharged but perfectly balanced.

With the back taken off, you can see the “lift-out” basket the original lead-acid battery came in, the 32x70mm cells fit the height with enough room to run the cables, BMS on top. Ah shoot, I meant to use the label maker to put on a label on that big red wire that said “wire” for @eddie1261! Next time buddy!



~200W load and go... and wait and wait and wait... Getting down to the end… and got 362Wh before the inverter cut out (the inverter cuts out before the BMS, it’s ancient).

So, draining at .5C it doesn’t get very warm, this is about 1/3 the way through; I can see it’s firing on all cylinders…

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Warms up more near the end but still not very hot… side view


Next up recharging! Takes forever as I'm using the original junk charger that was in it. It was slow before, and now the battery capacity is twice the size. Turned out the AC adapter had the right voltage, so I just snipped it off the Peak's circuit board and soldered it to the BMS.

Other similar projects & Tips

• Budget Models with Amazing Future Power; some DIY required
• Bob's Duracell Powerpack 600 Jump Starter

 

[Supervstech]

I have a ton of these... and I have tried building 18650s into a pack, annoying to fit into the case... I started rebuilding an old black and decker unit, but noticed all the cables are copper clad aluminum... dang. Also, the inverters in them aren’t pure sine wave... awww shoot. Still they make a neat case, and the connections work for portability.

 

[svetz]

I used the 32700's (32x70mm) without cell holders; they fit perfectly for me. I believe the18650s are 18mm by 65mm; so the height should work, but sounds like 9p might be tight.

You know, I never did anything with the existing wires other then to move them to the BMS... so I don't know if they're CCA or not! They didn't get hot, but I was only running at .5C.

 

[Supervstech]

Yup.
I have some of the 1200amp packs that use 22ah sla... there is more room in them. It is handy having a portable air compressor on the job site. The tiny 550watt inverter is useless though.

 

[Supervstech]

I’m also rebuilding the 24v battery for my mower with 18650’s in 3 cell holders tied together into a grid I’m up to 38Ah in the space of 20Ah sla... SOOOO much lighter a battery. But I am having trouble wiring it all up... mostly because this heatwave the southeast is having is sapping all my time and energy...

 

[svetz]

The tiny 550watt inverter is useless though.

What? None of your tables wobble?

 

[Supervstech]

What? None of your tables wobble?

Not THAT much...

 

[Will Prowse]

Holy cow this is awesome!!!

 

[svetz]

It's been sitting on a shelf since October, pulled it out today to check the charge... 13.29V ... so that's 3.32 V/cell (3.2 is nominal). According to my notes it was charged to 13.5 V (or 13.45 depending on how you squint at it) or 3.375V / cell. The range is 3.5 to 2.5V, so self discharge was 0.055V, which is about 1.1%/month.

Wow! That's a really small power drop for 5 months, eat that Lead acid (they have a self-discharge of ~4% per week)! It's on the charger now drawing 10.1 W. I'm measuring the total watts pumped in as voltage calculations aren't always that accurate, but if it's wildly different I'll post the actual results.

 

[svetz]

After reading Cass's post their solar generator was self-consuming 30 watts I tried to test the Peak Jump Start by leaving it on for 14.5 hours.

The display switched off after a few seconds after turning it on, but the 12 volt regulated cigarette lighter and USB stayed hot and one LED to indicate it was on. I recharged it with the kilowatt meter, but it didn't take enough power to move the meter off 0.00 kWh. Whew!

 

[svetz]

Been using it off and on since October and it's been working well. It's never run out of power but I typically recharge it after use and haven't used it for anything huge. I've been thinking about building another bigger one so I can use one while the other charges...but next time I'm using the prismatics and busbars, no way I'm ever soldering cells again.

 

[svetz]

I've been doing it wrong!

So, I've been storing my peak jump start at full charge, using it as needed, and then recharging it and putting it back on the shelf.

But... from this:

For a lithium battery the structure of the positive terminal becomes unstable when depleted of electrons for long periods of time. The instability of the positive terminal can lead to permanent capacity loss. For this reason, a lithium battery should be stored near 50% SOC.

So, I'm a ? LiFePO4 owner! So, what should I store it at?

Battleborn recommends Bulk/absorb = 14.2 – 14.6 V, Float = 13.6 V or lower. That sort of follows the V drop-off, but I don't think they're thinking long term storage:

I'm thinking a compromise. During Hurricane season I'll store it at 95%. Off season I'll drop it to 50%. Even when I need to use it for the odd thing 50% will probably give me enough power and if it's a big job I'll hopefully remember to charge it up the night before.

 

[Bob142]

I've been doing it wrong!

So, I've been storing my peak jump start at full charge, using it as needed, and then recharging it and putting it back on the shelf.

But... from this:

So, I'm a ? LiFePO4 owner! So, what should I store it at?

Battleborn recommends Bulk/absorb = 14.2 – 14.6 V, Float = 13.6 V or lower. That sort of follows the V drop-off, but I don't think they're thinking long term storage:

I'm thinking a compromise. During Hurricane season I'll store it at 95%. Off season I'll drop it to 50%. Even when I need to use it for the odd thing 50% will probably give me enough power and if it's a big job I'll hopefully remember to charge it up the night before.

I've been thinking about this a lot as well. LFP as standby is an interesting challenge. With my AGMs, I want to keep them topped off but need to be very careful about depth of discharge. With my new LFP systems I want to keep them stored at something significantly less than full to not suffer long term damage but I want enough juice in there if we get caught with a power outage event on short notice.

My current compromise solution is to make sure my grid/mains charger capability can charge my standby LFPs to 100% in 2 hours or less. That determines my "storage" SoC. We usually have enough warning for severe thunderstorms, microbursts, and macrobursts that 2 hours works fine. For hurricanes, severe snowstorms, ice storms and the like I'll have much more warning.

With my crate and yeti systems that puts me at about 80%. Where I have a problem is with the 8 new 280Ah cells I got recently. All I hear in my head is "you're gonna need a bigger boat". I'll need to significantly up my grid/mains charger game for those.

 

[svetz]

So, for the last 9 months, I've used the peak on and off and it's always delivered. What I haven't done is charge it, because hey... don't want the SoC too high right (see post #12)? I pull it out, abuse it, toss it back in it's little corner.

After reading @Supervstech's adventures, even though I'm still over a month away from the start of hurricane season, I figured I'd push the "voltage test" button. YIKES! 55% (12.05V, the scale is for lead acid, 10.5 to 13V, the SoC for LFP is ~10%) ... a Good thing it's not lithium-ion.

So, it's now sitting in its little corner plugged in. I'll do a capacity test in October, it would be nice to see how it's holding up after two years.

 

[Supervstech]

Adventures? What adventures? Ya mean my foray into tinkering with broken solar generators?
I just bought two more... another brand 250W unit, and an 1800 W unit... I’m waiting on the 1800W one to arrive at the pickup point... it’s a bit heavy for the driver...

 

[svetz]

Adventures? What adventures? Ya mean my foray into tinkering with broken solar generators?
I just bought two more... another brand 250W unit, and an 1800 W unit... I’m waiting on the 1800W one to arrive at the pickup point... it’s a bit heavy for the driver...

Hah! Way to go!

 

[svetz]

So, time for the hurricane preparedness test.

Two years ago, when I put this together, the theoretical capacity was 374Wh and in practice saw 362Wh.
Since then it hasn't been on any regular schedule and as you can see from above, slightly mistreated.

Before starting the test I let it charge until the BMS cut out, didn't take long as I'd fully recharged it just a couple of weeks ago.
The test discharged at ~8.2 amps powering an inverter powering a fan, so a fairly low discharge rate. The inverter cut out at 11.2V and the meter read 356.3 Wh, so a 1.6% loss over two years. Not bad!

 

[Bob142]

Looking good! How many hurricanes have hit since you built it? (Wondering if it's like when I put down grass seed and fertilizer and expect the rain that never comes... )

 

[svetz]

...How many hurricanes have hit since you built it? ...

Zero hits, one near miss.

 

[Supervstech]

I have 10 or so of these lying around...
so handy!