popotla
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- Jun 5, 2018
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Please could someone recommend a specific DC to DC converter with which to run my HP laptop from a 12 volt socket rather than via an inverter? I'm interested in quality and reliability rather than price.
I found the following somewhere and thought it worth passing on. The circumstances described here fit my own situation pretty well.
Subject: RE: Can you power/charge a laptop via 12 volt socket?
I await guidance from any qualified or knowledgeable people as to whether this simpler route will save valuable leisure battery reserves if we are using the laptop for 3 or 4 hours a night, and not on mains hookup.
...the answer is that using the DC to DC convertor will almost definitely save you battery power (over the option of using an inverter and the laptop power supply). Whether the amount is valuable or not, however, depends very much on the nature of the equipment you are using, and the amount of time it is used for.
Some generalities may help to illustrate:
A general purpose inverter, such as is regularly utilised by motorcaravanners, is unlikely to exhibit an efficiency of greater than 80% (and then only at close to rated output). Hence, every 80W you take out, you have to put 100W in.
If you then add your normal (240v) laptop lead, then this typically might exhibit 85% efficiency.
So, if you have a laptop with a (not uncommon) nominal 70W requirement, the 70W at the laptop will require 70/0.8*0.85 W from the source (roughly 103W). (This assumes, of course, that the device is running all the time at its nominal consumption)
If instead you use a decent DC to DC switched mode supply, you may be lucky enough to get up to roughly 95% efficiency (especially if it is specifically sized for the demand), but for illustration, lets assume 90%. Hence, the nominal 70W requirement would require 70/0.90 W from the source (under 78W).
The difference in demand in this case would be 25W, leading to 100Wh for 4 hours a night of watching. At a nominal 12.7V from a fully charged battery, this would be 100/12.7, or a saving of something under 8Ah per night.
E&OE
Many thanks Robinhood.
That's just the sort of answer I was really trying to establish.
We go away for quite extended periods in the MH (maybe 4 to 8 weeks away per trip), throughout the year...including winter months when even in Spain/Portugal it can be very cloudy/raining a lot.....and we are often parked up for maybe a week or so at a time, thus not running the engine, but reliant on just solar panels to replenish our daily/nightly use of 12 volt usage.
So, given that order of leisure battery power saving, I do think that getting one of those DC-to-DC ciggie lighter socket adaptors for about 15 quid is the way to go for us.
Then our existing inverter can continue to be used for other short-burst mains power when needed (electric razer etc), and would remain available as backup for the laptop TV watching if the DC adaptor packed up.
I found the following somewhere and thought it worth passing on. The circumstances described here fit my own situation pretty well.
Subject: RE: Can you power/charge a laptop via 12 volt socket?
I await guidance from any qualified or knowledgeable people as to whether this simpler route will save valuable leisure battery reserves if we are using the laptop for 3 or 4 hours a night, and not on mains hookup.
...the answer is that using the DC to DC convertor will almost definitely save you battery power (over the option of using an inverter and the laptop power supply). Whether the amount is valuable or not, however, depends very much on the nature of the equipment you are using, and the amount of time it is used for.
Some generalities may help to illustrate:
A general purpose inverter, such as is regularly utilised by motorcaravanners, is unlikely to exhibit an efficiency of greater than 80% (and then only at close to rated output). Hence, every 80W you take out, you have to put 100W in.
If you then add your normal (240v) laptop lead, then this typically might exhibit 85% efficiency.
So, if you have a laptop with a (not uncommon) nominal 70W requirement, the 70W at the laptop will require 70/0.8*0.85 W from the source (roughly 103W). (This assumes, of course, that the device is running all the time at its nominal consumption)
If instead you use a decent DC to DC switched mode supply, you may be lucky enough to get up to roughly 95% efficiency (especially if it is specifically sized for the demand), but for illustration, lets assume 90%. Hence, the nominal 70W requirement would require 70/0.90 W from the source (under 78W).
The difference in demand in this case would be 25W, leading to 100Wh for 4 hours a night of watching. At a nominal 12.7V from a fully charged battery, this would be 100/12.7, or a saving of something under 8Ah per night.
E&OE
Many thanks Robinhood.
That's just the sort of answer I was really trying to establish.
We go away for quite extended periods in the MH (maybe 4 to 8 weeks away per trip), throughout the year...including winter months when even in Spain/Portugal it can be very cloudy/raining a lot.....and we are often parked up for maybe a week or so at a time, thus not running the engine, but reliant on just solar panels to replenish our daily/nightly use of 12 volt usage.
So, given that order of leisure battery power saving, I do think that getting one of those DC-to-DC ciggie lighter socket adaptors for about 15 quid is the way to go for us.
Then our existing inverter can continue to be used for other short-burst mains power when needed (electric razer etc), and would remain available as backup for the laptop TV watching if the DC adaptor packed up.
