That's considerably higher than any of our laptops. So, yeah, the
dedicated off-grid computerer would do well to consider the power
consumption of his gear vis a vis the size of his battery.

--
RJS

On 08/02/2011 03:07 AM, Dennis Haynes wrote:
> My old Toshiba is rated 5 amps at 15 volts out. 1.2 amps going in at 120
> volt.
>
> Dennis
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> Rocket J Squirrel
> Sent: Monday, August 01, 2011 6:48 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Inverter/Aux Battery question
>
> I dunno what kind of antediluvian laptops are out there, but I just looked
> at the three laptop power supplies we have here and none output more than
> 2.1 amps @ 19 volts and that's 40 watts. Input power will be a bit higher --
> but just a bit because these supplies don't really get very warm which
> indicates pretty good efficiency.
>
> And again, I watch the ammeter on my aux battery pretty closely, and I
> rarely see the laptop pull more than a couple amps. 24 watts.
>
> --
> RJS
>
> On 07/31/2011 10:09 AM, Dennis Haynes wrote:
>> Even a single laptop power supply can use 100 watts or more,
>> especially with the laptop on and charging the battery in same.
>> Yes you do have a battery problem but even with that corrected your
>> use and run time with engine off is limited.
>>
>> Dennis
>>
>>
>> -----Original Message-----
>> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On
>> Behalf Of Daniel Rotblatt
>> Sent: Saturday, July 30, 2011 12:16 PM
>> To: vanagon@GERRY.VANAGON.COM
>> Subject: Re: Inverter/Aux Battery question
>>
>> Dennis-
>>
>> I didn't expect to have to use a full 400 watts - basically I just
>> wanted to be able to charge some computers, etc.  I don't imagine more
>> then 150 watts as a sustained load - and even then it's a luxury -
>> i.e. if the kids are bored and noisy and need to watch a video, or
>> something like that.  This issue is with no load on the inverter - just
> doesn't seem right.
>>
>>
>> Dan
>> Los Angeles, CA
>> '85 Westy Weekender
>>
>> On Jul 30, 2011, at 4:30 AM, Dennis Haynes wrote:
>>
>>> This is going to be difficult to explain but there are a number of
>>> things that are going against you.
>>> When sizing a battery for an extended load the battery should be
>>> sized for a minimum of  a 5 to6 hour discharge rate. To get 400 watts
>>> out of a 120 volt inverter you need 400/12 = 33.33 Amp/Hr. Consider
>>> some inefficiency and that fact that under load you will have less
>>> than 12 volts a full 40 A/Ah or more is required. The largest of the
>>> Yellow Top batteries is 55A/Hr. over the 6 hour discharge rate. So
>>> you do not have enough battery and this sustained load will damage it.
>>>
>>> Next problem is using a low cost inverter to charge batteries.
>>> Modified sine wave inverters basically switch and filter DC to make
>>> AC so most appliances can work. Motors due to their inductance do not
>>> care and Most DC power supplies can clean it up enough the only bad
>> effects are usually some hum or
>>> buzz on audio equipment or fuzzy lines on old televisions.   However,
>> cheap
>>> power supplies for charging batteries use the batteries as part of
>>> the filter and the peaks of the waveform pass right through them
>>> basically making the batteries a heater they now have a load in
>>> addition to what they actually need to charge. As such my 2002
>>> Toshiba Laptop and a 400 watt inverter can take down a 60 A/Hr. battery
> in about 2.5 hours.
>>>
>>> So for all those low voltage toys and cell phones get the 12 volt
>>> charger power cord for each device.
>>>
>>> Dennis
>>>
>>>
>>> -----Original Message-----
>>> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On
>>> Behalf Of Daniel Rotblatt
>>> Sent: Friday, July 29, 2011 5:17 PM
>>> To: vanagon@GERRY.VANAGON.COM
>>> Subject: Inverter/Aux Battery question
>>>
>>> Well, I just got back from a trip to Mammoth Lakes (separate post on
>>> that) and got a chance to try out the aux battery and inverter I got.
>>> The problem I had was that with the car off, the inverter didn't get
>>> enough power to work.  When hooked up (and I tried two inverters and
>>> got the same results), the voltage would drop from 12.6 to about 8.x
>>> volts - not enough to run the inverter and it would automatically
>>> shut off.  Thus, the only time I could charge the computers (keeping
>>> the kids happy), etc., was when the car was running.  Is this how it
>>> works?  What is the need for a aux battery, i could have just hooked
>>> up the inverter to the main battery and not used it when the car
>>> wasn't
>> going an saved $175 on the aux battery.
>>>
>>> Hook-up:
>>> -brand new yellow top battery
>>> -Stock attachement to the starting battery (had to replace the relay)
>>> -Inverter hooked directly to the terminals of the yellow top - about
>>> 4' of wire, (I tried just 8 gauge with about 3' of wire, and finally
>>> with 3' of 8 gauge and a few feet of 12 gauge hooked to that with a
>>> cigarette plug since that's what was on the inverter).
>>> -Inverter is a 375 watt Tripp-lite (good reviews on amazon).
>>> -Voltage at the battery (when new) was ~12.7 , with car running it's
>>> ~13.6, with car not running and inverter attached it's ~8.5 -All the
>>> inverters I saw shut off at a little over 10 Volts....
>>>
>>> So...is that what's supposed to happen or is something not right?
>>> I'm planning a trip to New Mexico next week, so it would be nice to
>>> have it working.
>>>
>>>
>>> Dan
>>> Los Angeles, CA
>>> '85 Westy Weekender
>>>
>