Vanagon EuroVan
Previous messageNext messagePrevious in topicNext in topicPrevious by same authorNext by same authorPrevious page (July 2011, week 5)Back to main VANAGON pageJoin or leave VANAGON (or change settings)ReplyPost a new messageSearchProportional fontNon-proportional font
Date:         Sat, 30 Jul 2011 07:30:38 -0400
Reply-To:     Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject:      Re: Inverter/Aux Battery question
Comments: To: Daniel Rotblatt <d.rotblatt@VERIZON.NET>
In-Reply-To:  <329EF91D-F64F-4727-B250-CBE38C633CCF@verizon.net>
Content-Type: text/plain; charset="US-ASCII"

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


Back to: Top of message | Previous page | Main VANAGON page

Please note - During the past 17 years of operation, several gigabytes of Vanagon mail messages have been archived. Searching the entire collection will take up to five minutes to complete. Please be patient!


Return to the archives @ gerry.vanagon.com


The vanagon mailing list archives are copyright (c) 1994-2011, and may not be reproduced without the express written permission of the list administrators. Posting messages to this mailing list grants a license to the mailing list administrators to reproduce the message in a compilation, either printed or electronic. All compilations will be not-for-profit, with any excess proceeds going to the Vanagon mailing list.

Any profits from list compilations go exclusively towards the management and operation of the Vanagon mailing list and vanagon mailing list web site.