Vanagon EuroVan
Previous messageNext messagePrevious in topicNext in topicPrevious by same authorNext by same authorPrevious page (January 2012, week 4)Back to main VANAGON pageJoin or leave VANAGON (or change settings)ReplyPost a new messageSearchProportional fontNon-proportional font
Date:         Sat, 28 Jan 2012 08:56:37 -0500
Reply-To:     Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject:      Re: Poor man battery testing
Comments: To: Scott Daniel - Turbovans <scottdaniel@turbovans.com>
In-Reply-To:  <018c01ccdda1$160bd890$0200a8c0@PROSPERITY>
Content-Type: text/plain; charset="US-ASCII"

The main advantage of the inverter method is the automatic shut off at 10.5 volts. Makes for some repeatability and you do not have to watch.

Dennis

-----Original Message----- From: Scott Daniel - Turbovans [mailto:scottdaniel@turbovans.com] Sent: Saturday, January 28, 2012 4:30 AM To: Dennis Haynes; vanagon@GERRY.VANAGON.COM Subject: Re: Poor man battery testing

how about just power the high beam headlights with the battery ... using that for a load ? ----- Original Message ----- From: "Dennis Haynes" <d23haynes57@HOTMAIL.COM> To: <vanagon@GERRY.VANAGON.COM> Sent: Friday, January 27, 2012 6:42 AM Subject: Poor man battery testing

Deep Cycle battery capacity load testing. Theory: Deep cycle batteries need to be tested differently than the normal tests used for starting batteries. The major consideration is that a deep cycle battery needs to be able to deliver power for a longer period of time whereas a starting battery is called upon to deliver a very large amount of power for a short period of time. Deep cycle batteries are rated in total Amp/hours over some period of time, usually 5,6, or 20 hours. This is critical to understand as the effect is not linear. Also it is important to note that a longer, lower current draw will actually bring the battery to lower state of charge as the cut off voltage is approached. There are many variables to battery performance and test results but we will want to do is come up with some repeatable procedure. Ultimately you will want to try this

on a new battery after 10-20 cycles to get a baseline. Then at some periodic interval you test again to determine the health of the battery. The Tools: The basic tools will be to get a 12 volt to 120 volt inverter. One with metering would be real nice but a basic 400 watt unit will do the job. The inverter will be used to supply a load and the feature we want is that it will shut off when the battery reaches 100% discharge (10.5 volts). Next we want an old style electric clock. We can set the clock to 12:00 when

starting the test and when the inverter shuts off we will be able to see how

long the battery lasted. Next we will need a load. Regular light bulbs can provide us with a known load. The watts to be determined by the battery capacity we wish to test.

The method: We need to know the battery rated capacity and decide the test method we want to use. The 5 hour test provides very good test results. Note that a battery is not considered failed if it can deliver 80% or more of its rated capacity. As such if the battery is still going at 4 hours at a

full load we may choose to stop the test to avoid needlessly wearing it. So let say we have a battery rated 100 A/H for 5 hours, we want a load of 100/5=20 A/h load. 20 A/H X 12 V is a 240 watt load. So 240 watts of light bulbs will in theory give us the load we need. Now we need to keep in mind that the battery rating is based on Amps. As the battery voltage goes down current needs to increase if we are to maintain the same power. Real load banks compensate buy increasing the load as the voltage drop to maintain a constant current draw. The inverter may also do that to some extent. Add the

inverter looses and other variables and we need to use a slightly lower load. For our test purpose for this size battery lets use2-100 watt bulbs for a 200 watt load. Again, after you do this once you will have a base line

so just use the same equipment for the next test so you get a trend. For the test you want to start with the battery fully charged. If inclined take specific gravity readings of all the cells. If some cells are low try on equalization charge to bring them up. On large motive power batteries we

sometime do long term constant current charges to get the acid out of the plates and if needed we also do acid adjustments to get the cells back. Anyway after the battery is fully charged we want to let it sit to dissipate

that surface charge and be at room temperature. So we will connect the inverter, clock, and light bulbs. Be sure to have the

bulbs in real sockets, lamps, a drop light etc. broken glass and glowing energized filaments do not make for a good day. With the clock set to 12:00 turn the inverter on with the load. Now let's see how long it keeps the lights on. You may want to take voltage readings before starting the test, (open circuit), when the load is turned on, and then every hour. This will also give you a lot of information.

Dennis =


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.