Mopar Muscle Association UK

I know some of you guys know your onions when it comes to electronics. From time to time I need a source of 12V DC power to test or operate something on the car. Case in point is the convertible top motor which I’ve recently been finishing. In the past I’ve just used a car battery, but over the years they wear out and I’m not using it frequently. I had an old one which finally gave up the ghost.

I thought about using a mains powered 12V DC supply, and looked at converting an old PC Power supply (plenty of how-to’s on the net) which worked but did not supply the current I need. I reckon about 30-40 amps is necessary if it would work safely on my convertible top, or full beam headlamps etc (30 should be OK but may be better to have a safety factor?)

Anyway, I came across these on the web – they are popular for LED strip lights etc. Can get 30 amps for a decent price, 40 is a bit more. On the surface it looks like the ideal solution, but wanted to check with someone knowledgeable in case I’m missing something (surge protections, inrush currents etc).

Does this seem like a plan or have I missed something?

Will the Challenger need a new Battery?

If so, get one, use that for testing and keep it conditioned correctly.

That's what I had been doing that led to this question, I'm looking for an alternative and thought this looks like a solution - I can't see an issue but that doesn't mean there isn't one!

The only one I can see is cost.

As long as it supplies a smooth supply without peaks or spikes at the required ampereage I think it will be ok, but I would just use a battery really - that is what I did when I did my Challenger wiring (but no power top)

Thanks Pete - like I said I tried the battery route twice and here I am looking again, hence this post. This is a lot cheaper than a battery, and it should last forever, is small, light, transportable etc. But regardless it's OK for anyone to go that route, I just want to find out if this route will work.

I imagine it will be a smooth supply, but that's exactly what I'm hoping to find out in this post.

if its electric motors you need correct voltage and be able to supply the amps it wants, which is massively dependent on speed of rotation and the torque it needs to produce. power supply might trip out.... your fan or wiper motor can suck 30+ amps at 12-14 Volts for few milliseconds before it settles down to something like 7amps when turning at speed.

car electrics are horrible, and the DC is more like the crenellated battlements of a castle so your power supply is potentially Luxury.
provided it can get over the start pulse ,i would think the gearing and hence torque necessary would be limited to using a current befitting of a 1970s car i.e less than 30 amps and potentially by quite a long way .

should work.....

but if it doesn't

Run two in parallel

OR


Lithium based battery tech can be stored for months/years at a time at storage voltage of 3.7 V top em up to 3.7 and leave
charge to 4.2 and use straight away they will fall to 3.7 V and stay there for 80% of the useful time then fall to 3 .?? time to charge. 3.7 for storage 4.2 for use



so i will recommend 3 or 4 of the batteries that i have put a link to below, strapped together with bus bars in serial config or double up and do 4 serial 2 parallel for more amp hours.

3.7 (4.2) volt lithium ion battery designed to power a detroit electric "super car" when used in bulk

nominally 3.7 volt, fully charged at 4.2 but charge em up to 4 or 4.1 and they can last years

3 or 4 in series gives you any where between 14 and 16.8 volts which is fine car stuff should survive a little over voltage 14.2 is what car stuff expects when the alternator is ON at full chat.

its a 20 amp hour battery with a maximum discharge SPIKE of 10C or 10 times capacity i,e 200 amps and the can sustain 5C or 100 amps continuous for 12 minutes

i have 10 of them. as i'm building a dangerous push scooter, of a type that isn't banned at santa pod, because my less dangerous 20 cc petrol engines one is banned,
and i also have the burnt finger to prove it...

https://www.ebay.co.uk/itm/72v-20ah-diy ... SwbFFe1BzL

speak to jimbob, phone number usually in one of the pictures on his listings, he doesn't like paying e-bay, you can pay pal but cash in hand works as well..
expect to pay £11-£12.00 each and £10 of copper bus bars (5).
you will need 4 x12 mm long m4 button cap + spring washers to bolt on bus bars. use the extra one cut in half for + and - connection.

he uses these to power his barge.... hes an electric vehicle designer of the itinerant kind

build battery pack, m6 stud at top through cases, cable ties at bottom

THEN ZaP STUFF

use a lipo charger for 4 serial cells or invest in a laboratory power supply to charge at 3 amps and about 16 volts

I can recommend a Gophert supply for charging LIPO and lithium ion batteries, provided you know what you are doing, its way better than the standard black box chargers.

I have
GOPHERT NPS-1602 0-60V 0-3A 110V/220V 180W Switching Digital Adjustable DC Power Supply very precise clean power supply)
and i use it to charge my 42 volt 10s set of these batteries

they stay in balance so no need for BMS

or you can get some from his mate in Manchester, at £12.30 each

just type EIG cells in eBay

made in Korea not china, and Koreans do not seem to lie about battery spec

as long as you don't discharge them down to less than 3 volts each regularly (12 volt for the pack) the pack will last a very very long time

please charge outside.........! burning lithium makes a right old mess of you and your belongings

also handy when camping or for powering led Christmas lights


Dave

40 amp hours 4 serial pairs
80 amp hours 4 serial quads

with a C of 80, 10 C is 800 amps.... peak....its a bit much you could spot weld with it

Thanks Dave, I thought you might chip in, very helpful and as usual a bonus to think about!
Since this is mainly about a cheap/durable alternative to a battery, the one I posted is £18 delivered for 30A, still a fair bit less than the Lithium battery option.

The circuit breaker in the Dodge is 30A for the convertible top, and 20A for headlights. So I imagine that a PSU of 30A should be enough, though could get a 40A version for another few quid (eg )

The spec on the amazon link says:

Product Features:
Auto on/off cooling fan
High efficiency
Low temperature
LED indicator for power on
Over Load and Short Circuit Protection
Over Voltage Protection

Output:
DC Voltage: 12V
Rated Current: 30A
Current Range: 0-30A
Rated Power: 360W
Ripple & Noise (maximun): 150mV
Voltage Adjustable Range: 10-13.2V
Voltage Tolerance: +/- 2.0%
Line Regulation: +/- 0.5%
Load Regulation: +/- 0.5%
Setup, Rise, Hold Up Time: 200ms, 50ms, 20ms at full load

Input:
Voltage Range: 90-132V AC / 180-264V AC by Switch 248-370V DC
Frequency Range: 47-63Hz
Efficiency: 74%
AC Current: 6.5A/115V 4A/230V
Inrush Current: 25A/115V 50A/230V
Leakage Current: <3.5mA/240VAC

So only real question is whether the circuit breaker has a 'slow blow' which doesn't care about a few ms of 40? 50? 100? Amps but the Power supply would care, and would either blow up or cut out and not work for this purpose - don't know if those specs shed any light on that?

i think it would be rare for it Not to be slow. if the supply is destined for a device that has a fan or a device that contains any kind of inductor it has to cater for a surge...

Thanks all, I ordered a 40A supply for about £25, it arrived and I wired it up and it works perfectly, runs the convertible top motor (actually quicker than my battery ever did) without blowing anything up, so I'm all set
Smaller, cheaper, less (=no) maintenance and much longer life than battery so for my purposes, job done.

Result!!!

excellent

i'm gonna get me one of them

saves dicking about with an old battery charger when fixing electric bits



Dave