Portable jump start pack - recommendations please.

Bad battery connection or failed alternator

I assume it wont crank.

On charge battery voltage should be around 13.5-14V .

Make sure the terminals are screwed down tight as starting current is a couple of hundred amps and it doesn't take much to block that completely

Well the motor home will have a leisure battery built in.

If you really must get something with good reevews from Amazon

What's the no-load voltage? Perhaps it had sat around and didn't have very much charge in it when supplied. Have you tried charging with an external charger?

I have a lithium pack from CPC which is ok, but the problem is that if the battery is feeling very sad (let's say at 8V or below) the lithium pack may discharge into the battery without being able to hold up enough current to also start the car. If the battery is at say 11.5V then it may do.

(before anyone says, I've run lead acid batteries down to zero and then managed to charge them up enough to be usable again. Obviously don't do this as it's very bad for the battery, but eg if you left the lights on you can run it down to nothing and then might need to start the engine to get home)

I don't think this is such a problem with jumping with a lead acid, as there's a lot more energy in there than a lithium pack and you can potentially run the car from the jump pack without the original battery.

Theo

In article snipped-for-privacy@mid.individual.net>, David snipped-for-privacy@btinternet.com scribeth thus

A 2016 batt would be well past it, but check the fan belt or whichever belt drives the alternator to see if its properly tensioned and therefore charging as well as it ought!..

I bought one of these from Amazon about 6 years ago in a flash sale at a large discount. It still works well and has started various cars and diesel vans. The largest car engine was a 6.3l Ferrari FF with a totally sulphated battery. It did struggle with that but eventually started it.

John

Thanks. NOCO seems to be highly rated on various sites.

Cheers

Dave R

It cranks, but the displayed voltage on the voltmeter rapidly drops below

The car is in the garage for other work, and fortunately (?) showed the failure when they tried to move it. So under investigation.

The interesting thing is that this failure was diagnosed as an old battery so there is now a brand new battery in the car, fitted by the garage.

I am wondering if the alternator is not running at full output, but wondering how that would generally manifest. It is delivering 14V.

The battery (as shown via the voltmeter) has less charge now than when it was fitted.

Testing across the battery terminals is difficult because the battery is under the passenger seat and you have to remove the seat to get at it.

Cheers

Dave R

To track down which fuse the parasitic load is on, a set of these multimeter leads can be handy (beware the miniature size fuses).

I got the battery replaced in my previous car when it started showing signs of failure in cold weather. Turns out it still had the OEM battery in from when the car was new. It was 18 years old when replaced!

FWIW, I ordered one last week as it had been on my mid to do for a while, and was finally prompted by a flat battery in the lawn mower! (and I could not be arsed you jump start it from the car).

-- Cheers,

John.

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Probably not relevant here, but when I had a similar problem many years back - I replaced the battery but that didn't solve the problem - I eventually discovered that the earth strap between the engine and the car body had degraded to the point where there was only a tiny number of strands left intact.

That meant the alternator couldn't put any charge into the battery due to the high resistance path. A nice problem to have, on Christmas day, when travelling 200 miles to get home.

Garage diagnosed a faulty crank sensor, which they think could have stopped it cranking over before it could get going. We shall see.

Now on long term charge in the drive with a smart(?) charger. I don't think it chucks out a vast amount of charge, but is very good for maintaining battery condition.

I will have to dig around in the store of motoring related things to see if there is a more powerful charger to get it up near fully charged in a shorter time.

I am still not 100% sure that there isn't another fault hanging around in there somewhere.

How do you diagnose an under performing earth strap apart from by inspection?

Cheers

Dave R

On a VW Polo that was draining its battery unattended, I found something was constantly energising the windscreen wiper motor to move over to the rest position.

To chase that parasitic load, I put a DMM in series with a fully charged battery, and then promptly burnt myself touching the meter leads, such was the high current it was then pulling.

Bought a clamp meter that did DC current (hall sensor) soon after.

Bought a NOCO GBX45 off Amazon. Interesting looking bit of kit. It came mostly charged. It doesn't come with a charger. I haven't read the manual yet, but the picture on the front says 10W USB A out, and 60W USB C in.

It looks as though it needs a USB C charger capable of chucking out 60W if you want to be able to use it twice without waiting a long time for it to charge.

I do have one fast charger, but as it is for a Realme Pro phone I don't think it uses the ususal fast charging protocol.

No manual - need to look on line.

Interesting times ahead, as usual.

Hopefully I can find a fast charger which is compatible with my Samsung Galaxy Tab A8 and the NOCO. NOCO uses Power Delivery 3.0.

Cheers

Dave R

Crank sensors is equivalent to removing the distributor from an old fashioned engine

Definitte crank, no start.

Crank sensor shouldnt flatten battery

Measure voltage between the battery negative and earth with the engine running

It's possible it wants to charge from 20V (60W = 20V @ 3A) which might mean it won't charge at all from a phone charger. Depends whether the internal charging circuit can step up the voltage or just step down.

Theo

Charged OK from whatever is in the 13A + USB A sockets installed 12-13 years ago.

I am currently in a minefield trying to establish which of my many devices are compatible.

I have Anker and uGreen cigar lighter socket chargers which claim to be fast chargers. A bit coy on which variants of signalling they support. Mention compatible cables - but my raft of USB cables don't seem to have that information on them.

Now looking at a Dell Laptop which has a USB C port which accepts charging from a Power Delivery charger, but doesn.t say if the supplied charger supports Power Delivery.

I am hoping that most/all charger support the basic Power Delivery standards and I just need to make sure I have the correct USB cable. Then label it clearly.

Ho hum.

Dave R

I had one completely broken between engine and body. It wasn't in the battery path so there were no easy clues, it just caused the speedometer to swing around wildly and intermittently. It turned out that ignition pulses were crosstalking into the speed pulses. I found that out with the car on axle stands, the wheels turning, the dashboard pulled out and an oscilloscope on the passenger seat. I got some funny looks from passers-by.

Crosstalk? Start looking for earth trouble. It had broken because it had been too short and was under strain. Fortunately, I had a chunk of earth braid from previous car adventures, as well as the two 140W Weller soldering guns necessary to solder the stuff.

Dug out my old (allegedly) 8A charger (old is well pre metrication, AFAIK). It still works, but is only reporting 4A charging.

My dodgy arithmetic suggests that at 4A per hour it is putting in 4 Amp Hours of charge.

That doesn't sound a lot for a large battery that cranks a 3 litre diesel.

Unreliable lookup suggests around 77 Ah capacity for the battery. Call it 80 Ah just to simplify the arithmetic.

Assuming 80% charge it would need 80 - (80X.8) = 16 Ah to fully charge. That doesn't look too bad. Charged from 80% in 4 hours, I think.

However:

seems to offer much more powerful chargers.

There is also a very confusing maximum engine size, where for example a 6A charger shows maximum size 1.6l. The same reported charging rate (such as 6A) also shows as 1.6l, 3l, etc.

So I am wondering if my ancient charger is suitable, or if I need something beefier.

Compared to Screwfix, Amazon is very cheap

Bottom line, is it time to invest in a new charger?

After not needing one for a long, long time (decades) I am suddenly in a world of pain.

Cheers

Dave R

Is your old charger the kind with analogue volt/ammeters?

I have one of those ('Unipart' branded). There are two problems. The first is that it's a pretty crude lump where the charging current is limited by the iron transformer they put in it. If the battery is flat then the current goes up to maximum, but if the battery has some charge it in the current tails off quite rapidly.

The other is that there's no end of charge termination (aside from the current dropping off) so it's possible to overcharge batteries if you leave it on too long.

I switched to a modern charger (Lidl's 'Ultimate Speed' 4A, about £15) and it's much better - I can select a setting for AGM and leave it, eventually it'll complete and end up in float charge. Looks like this (this one's 5A):

Keep the old charger in case you have a battery that goes to zero, at which point the smart chargers won't touch it. The dumb charger gives it just enough charge to get it going. It's very bad for the battery to zero it, but I've recovered from it a few times and got the battery to limp on for a bit longer.

Can't speak for that one, but when I looked at teardown videos a lot of the no-brand Chinesium chargers had poor power supplies - insufficient isolation between the mains and 12V sides.

I went for the Lidl because their stuff tends to be fairly dependable.

Yes.

Theo