DIY cranking or booster battery pack

[MikeT]

Following the C3's recent battery discharge and last winter's concerns over the C5's battery condition I think it's prudent I obtain a portable booster pack before the cold season arrives.

Although the LiPo cells I'm familiar with are a good choice in that respect, I've since learnt that LifePo4 is the chemistry of choice. Not just as jumpstart/booster packs but as direct upgrades for the SLA cranky too. They weigh less, tolerate discharge better, recharge quicker, last longer, etc, etc.

So the plan is to build a pack that meets or exceeds the C5's requirement of 720CCA.
Trouble is, trying to find out which cell offers best capacity, discharge rate, size, shape, weight and cost? I've tried scouring the internet but it's like herding cats.
After that, it should be a doddle

[EDC5]

That's a very interesting project, I'd recommend watching videos by a guy on Youtube who wanted to replace a 12v battery in his electric bike with LiFePO4 batteries.





While It seems a good idea in principle, I'm not sure how tolerant of a noisy DC supply from the alternator these batteries would be.

[white exec]

Have just been reading Wikipedia's entry on these LiFePO4 batteries.
Looks like a significant collection of breakthroughs...
https://en.wikipedia.org/wiki/Lithium_i ... te_battery
...not least the potential for re-charge in less than a minute - faster than you could re-fill and ICE.

Applications and advantages, too, for small-sized batteries (AA-size etc), in circuit simplicity, connection and environmental concerns.

[MikeT]

I like Julian's vids, Ellis, very educational.
The industrial LifePO4 SLA replacements should have built-in BMS/protection-circuitry. Something I'lll look into once (if) I succeed in creating a useable portable booster pack I'm happy with. Prices are beginning to look quite scary though.

Indeed, Chris. Looks like my solar/led systems may be getting LifePO4 upgrades too (even though it's almost two decades-old tech).... just when I thought LiPo was the bees-knees
And I believe China are about to wipe the floor with something even better, achieving EV battery density of 200Wh/Kg?

[GiveMeABreak]

And I believe China are about to wipe the floor with something even better, achieving EV battery density of 200Wh/Kg?

Yes, coal-fired no doubt.

[MikeT]

"It's too late for pessimism"

[myglaren]

That is a truly excellent film - I have two copies of it here.

[EDC5]

I like Julian's vids, Ellis, very educational.
The industrial LifePO4 SLA replacements should have built-in BMS/protection-circuitry. Something I'lll look into once (if) I succeed in creating a useable portable booster pack I'm happy with. Prices are beginning to look quite scary though.

Indeed, Chris. Looks like my solar/led systems may be getting LifePO4 upgrades too (even though it's almost two decades-old tech).... just when I thought LiPo was the bees-knees
And I believe China are about to wipe the floor with something even better, achieving EV battery density of 200Wh/Kg?

I've been following Julian for some years, I owe my hobbying interest in electronics to him almost entirely. Plenty of videos explaining electronics concepts in basic terms along with practical circuits that are easy to copy at home.

I especially liked his series on making a Maximum Power Point Tracking solar panel charge controller. I made my own version and went a bit further by learning how to etch PCB's too.

On topic though, and I'm surprised that the Lead acid is still so prevalent. Even some EV's have a traditional 12v Lead acid which just seems bizarre.

[van ordinaire]

Traditional batteries are (relatively) inexpensive, (increasingly) dependable & readily available all over the world, in a bewildering choice of dimensions, capacity & terminal arrangement - & now there is some suggestion that the much vaunted red and yellow top batteries may not be all they were cracked up to be. However, a lead acid battery in an EV goes beyond irony; that said, I did read the explanation (on this very forum, I believe) for that & it all made perfect sense at the time.

[Paul-R]

A lead acid battery is also far more tolerant of charging and discharging conditions compared to any of the Li-ion family. It needs only the most basic charging circuitry.

[MikeT]

Lead acid has had its day, horribly toxic, weighty, bulky, slow to charge, self-discharging, short-lived, money for old rope.

[white exec]

I'd be pleased to see the backside of 12v lead-acid gel-type batteries for things like UPSs. Seem to have a life of not much more than three years when used in series for a 24v units, and only slightly better for single-battery 12v ones.

Have a couple of UPSs which, when the battery finally died, I just parked a much larger Ah one beside it, decently wired in. Most of these UPS units seem well able to look after the charge requirements of larger (same type) batteries, just taking longer to recharge them.

At least now the call-off current for backing up PCs has plummeted, particularly now monitors are LCD.

[MikeT]

I haven't used a desktop for eons - since getting one of those free energy monitors off SSE - as I was horrified to see the consumption difference of it compared to my 17" laptop. It also made my UPS redundant as we all know the laptop has one built-in.

Anyway, decided to take the C5 out today as it's been sat for a week and as I've now got one of those ciggy lighter voltmeters (because the Citroen-provided battery gauge on the dash is useless in this respect).
Cranking was slow but it started ok and immediately registered 14.2v. I took the long way round to the GP surgery and returned home via the same long route, covering over 20miles in all, running as few electricals as possible (though I did listen to the 3pm news and traffic announcement). After parking up, it showed 12.2v once the surface charge was absorbed.

I suspect the battery's part-sulfated and simply won't take a full charge anymore so I'm going to save my pennies and buy some of those headway cells before the cold weather gets here.

Would anyone else be interested in purchasing these cells, as I'm currently composing an email to enquire about capacity options and if any discounts can be had?

[EDC5]

Have a couple of UPSs which, when the battery finally died, I just parked a much larger Ah one beside it, decently wired in. Most of these UPS units seem well able to look after the charge requirements of larger (same type) batteries, just taking longer to recharge them.

At least now the call-off current for backing up PCs has plummeted, particularly now monitors are LCD.

This is true, I linked 4 88AH deep cycle 'marine' lead acids to a beefy HP UPS. It didn't seem to complain and recalibrated it's runtime accordingly which amazed me.

Would anyone else be interested in purchasing these cells, as I'm currently composing an email to enquire about capacity options and if any discounts can be had?

I'm not sure If I would be interesting in making my own car battery (as I've recently bought a new one), but I'd like a few LiFePO4 cells to play around with if you get a good price.

[MikeT]

Got a reply to my email. Unfortunately, they only offer discounts on large orders (50+) so that's off the table. Also, their 15Ah cells are out of stock until December.
Of the three they do stock, it's the smaller capacity 8Ah cells that provide the highest burst output.

As I need a 4S configuration, ensuring adequate capacity could prove expensive - The battery for my C3 is specified at 600cca and the C5 at 720cca.
But I note in your captured data Ellis, the cranking current (albeit in relatively warm temperatures) only peaked at 270A.

Presently, I can't find any other vendor of these cells that I'd trust, even though they're cheaper elsewhere.