DIY cranking or booster battery pack

[MikeT]

Clear as mud, MikeT.

The 8400mAh LifePO4 cells have a 2C charge rating so the cars accessory socket 20A fuse should offer some protection if the BMS fails while testing.

[MikeT]

First tentative in-car LifePO4 charging test occured this evening via the accessory socket with seemingly favourable charge levels observed.

[MikeT]

I think a recap is in order, if only to save myself having to re-read the whole thread to remind myself where I'm at.

1st Experimental Project: I now have a way to charge the car that's lightweight and can be squeezed under the bonnet so I can lock the car up without needing to supervise. The downside is @6A max, it's a slow process (though no slower and far more desirable than having to previously heave the lead-acid out of the car and put it on my mains charger).
This alone was the main driving force of all this as I didn't want to have to buy two new batteries that will inevitably suffer accelerated and premature sulfation in my ownership.

2nd Experimental Project: The option to jump-start from the lithium pack still awaits testing as it's no longer a priority since removing the tracker from the C3 and given the success of the first project. Nonetheless, it's worth adding to my toolbox and will offer further benefits, I feel.

1st Bonus Experimental Project: I can also recharge the lithium pack off the car's alternator though more tests are needed to see if I can completely do away with the need for a dedicated in-car lithium charger.

2nd Bonus Experimental Project: Ony just occured to me the other night while I sat waiting for the windscreen to defrost.
9000 interwebs goes to the first person to guess what I've since ordered?

[white exec]

A hot air blower to flatten the LiFePO₄ battery?

[GiveMeABreak]

One of these?

[MikeT]

Close enough, Chris.
...a slight correction.

A hot air blower to flatten the Li Po's batterys?

One of these?

Mike Blower B.PNG

Mike Blower A.PNG

Tried something like that before, Marc. It was pathetic. All noise and rattles and no sign of any useful heat.
What I've ordered looks more like a PC fan stuck on a heating element. Crude and cheap but hopefully pretty powerful (tempting fate now, aren't I?).

[Gibbo2286]

I just read all through the thread, well most of it.

My answer when I had 30 + cars on the site was a big spare battery on the bench, a cheap solar charger keeping it topped up and a good set of jump leads, never had the embarrassment of a car that wouldn't start when a customer arrived or was due in.

[MikeT]

Aye, the good ol days, eh Gibbo? When I were a lad, I could swing a lorry battery in each hand, push start a lorry if need be.

[MikeT]

SMH!! Here's an amusing anecdote you may enjoy.

To test the in-car charging I rummaged around my spares looking for a pre-wired accessory plug with a hefty fuse and found one attached to a very long length of feeble wire. Couldn't remember what it was attached to, just glad it was rated at 15A and got busy making the appropriate harness for it all.

After testing I noted the plug was excessively hot so decided not use that plug again.

Now here's the funny part. You know that heater I said was pathetic and noisy? Turns out that's where this plug/wire combo came from and that I'd thrown away the wrong bit! If I'd rewired the heater, it would have worked a treat according to this video.

[MikeT]

1st Bonus Experimental Project update: The first test was to get an idea of how many amps the car might be putting out and to see if the BMS could bleed off any excess adequately. Today's test the battery was further discharged first, but again the current was well within limits so looking good so far.

Postie delivered the main part for my 2nd Bonus Experimental Project today (heater) and to be honest, I didn't believe the claimed 300W as there were other vendors only claiming 150W for the same looking unit so immediately put it to the test using their intended power source - 4S 5000mAh Lipos.

Ok, so 4S Lipo's means a starting voltage of 16.8 (nominal is 14.4V) but I wasn't expecting to see it drawing over 500W when switched on!
It quickly settled down to about 450W pulling just under 30A consistently, surpassing my expections I'm very pleased to say.
Next test - battery duration, then have to wait for the next frost for an in-car test.

[Gibbo2286]

I thought Lipos was what the large ladies had to reduce their bulk.

[MikeT]

The apparatus behind the new batteries is presumably the Liposuction.

I thought Lipos was what the large ladies had to reduce their bulk.

We have an FCF comedy duo

[white exec]

'Tis panto season, after all

[Paul-R]

Oh no it isn't!

[MikeT]