Power Bank
Posted: Thu Jul 13, 2017 1:19 pm
Just saw this and thought what a handy pocket sized backup it is!
http://www.ebay.co.uk/itm/Silverline-42 ... 3025612710
http://www.ebay.co.uk/itm/Silverline-42 ... 3025612710
The complete information source for Lotus Elan sportscars.
https://lotuselan.net/forums/
elanfan1 wrote:Further how does a power pack rated at 6000 milliamphours possibly produce enough power for a car emergency start - the advert is claiming 400ah output - where does this come from? Is it magic? My kids have similarly rated back up chargers for their phones which buy them a few more hours of phone usage I fail to understand this stuff.
Is this all puff or is there some truth in it? Apologies in advance.
elanfan1 wrote:Further how does a power pack rated at 6000 milliamphours possibly produce enough power for a car emergency start - the advert is claiming 400ah output - where does this come from? Is it magic? My kids have similarly rated back up chargers for their phones which buy them a few more hours of phone usage I fail to understand this stuff.
Is this all puff or is there some truth in it? Apologies in advance.
mbell wrote:They can be very dangerous.
denicholls2 wrote:mbell wrote:They can be very dangerous.
Yes. While this might be OK for plugging in and adding to a battery that has discharged by, for example, leaving the lights on, it is scary in the use posters are referring to of a hot jump.
Lithium Ion batteries have a very high discharge rate, which permits them to deliver a lot of current all at once provided the conductors to deliver it are present (hence the 400 amp rating). But they are notoriously intolerant of charge rates outside of their design parameters (anyone ever heard of flaming Galaxy phones or hoverboards?) While the quality of the batteries is a big contributor in these events, physics does not like to be denied.
A hot jump isn't problematic on the starting side of the process, but disconnection needs to be immediate. The current flowing back to the battery when the engine starts is almost certainly going to be way above design parameters and a prime opportunity for a battery explosion. I wouldn't want to melt an Elan that way.
Yes, you could implement a protection circuit to prevent reverse flow.
ericbushby wrote:Phil and Steve,
A 400 amphour battery will give 400 amps for 1 hour, or 1 amp for 400 hours.
The maximum current available depends on its internal construction.
This is a 6 amphour battery so it will give 400amps for 6/400 - 0.015 hours or 54 seconds as suggested by nmaudit above.
If we allow for 50 percent losses due to small cables, internal resistance in the battery etcetera we now get 27 seconds.
My car takes 160 amps to start it so it will last for 67.5 seconds, whlch, if there is no problem except a flat battery should be enough to start it.
I hope this explains it and please notice that I have not said this is a good idea.
I think some small jump leads to re-charge you car battery for a few minutes from your new friends car is more likely to work and you are not carrying a high energy lithium battery.
Eric in Burnley
1967 S3SE DHC