How many amps do you need to crank over the (flat) battery
Discussion
If the flat battery is still connected, remember that your power pack will be trying to charge the flat battery as well as turn the engine over. That's pretty tough for even the biggest battery to do let along the little batteries that are in most of these portable power packs. If at all possible, get it connected up to a running vehicle and let the flat battery charge up for ten minutes before you try to start it. That way the flat battery may be contributing a few amps rather than being an extra load.
By the way, 400 Amps should be ample but it would take some pretty hefty leads and a big battery to provide it - I reckon 250 Amps is more realistic for the ordinary cheap portable power packs.
By the way, 400 Amps should be ample but it would take some pretty hefty leads and a big battery to provide it - I reckon 250 Amps is more realistic for the ordinary cheap portable power packs.
When my battery died I tried quite a decent portable power pack and it was useless! Also tried jumping from a 1.0ltr corsa and that proved fruitless as well! Now have a new VX battery and its been brill, even being left unused for weeks in this cold weather.
And remember the cheapest place for a battery is yr local VX dealer, even if they plead stupidity and say they dont stock them... they do trust me but some dont list them properly or effectively.
And remember the cheapest place for a battery is yr local VX dealer, even if they plead stupidity and say they dont stock them... they do trust me but some dont list them properly or effectively.
The weakest link is often the connections. If you've a hundreth of an ohm at each contact point - there are 4 (one at each end of each jump lead) and you attempt to draw 250A then the resistance will drop 250 x 0.01 x 4 = 10V: not much left to drive the starter motor!
As said above an externally connected battery will be charging the installed flat battery as soon as the connection is made. So possibly a significant portion of charge may deplete the external pack.
Steve
As said above an externally connected battery will be charging the installed flat battery as soon as the connection is made. So possibly a significant portion of charge may deplete the external pack.
Steve
The power pack presumably is another 12V 6 cell lead acid battery. The flat battery will still have an open circuit terminal voltage of approaching 12V so will not actually drain the power pack very much.
The poor performance will be mostly due to the small capacity of the power pack. Presumably just a 7Ah NP7 size used in UPS etc - a tenth of the Ro's. Unless the power pack has exotic low internal resistance (expensive)special cells then it is just fundamentally useless. Yet another product people dumly buy because UK law allows wild unsubstantiated claims to be made (like cosmetics etc).
I have a 14V 150A switched mode psu I use for jumping though not had to use it on the Monaro. It works but of course it is an industrial product £1000 + when new. I bought it surplus for £40.
The poor performance will be mostly due to the small capacity of the power pack. Presumably just a 7Ah NP7 size used in UPS etc - a tenth of the Ro's. Unless the power pack has exotic low internal resistance (expensive)special cells then it is just fundamentally useless. Yet another product people dumly buy because UK law allows wild unsubstantiated claims to be made (like cosmetics etc).
I have a 14V 150A switched mode psu I use for jumping though not had to use it on the Monaro. It works but of course it is an industrial product £1000 + when new. I bought it surplus for £40.
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