I would just turn on lights until I got to around 20 amps. You can get 100 watt 12 volt bulbs at West < https://www.westmarine.com/buy/ancor--standard-screw-base-bulbs--P009_276_006_521?recordNum=3>. 2 or 3 of those would do. For a temporary setup, a standard cheap halogen car headlight is usually about 55 watts on low and 60/65 on high. Two of those running high and low beam would work. You do not have to be exactly at 20 amps, 15 or 25 will do. What you do need to do is set a timer to go down and turn them off at the 50% point and you need to be able to measure the amps to get this right. This is NOT going to be exact, but it should roughly tell you if you are near the stock capacity. Here is something to watch: I bought a new gel in January and it seemed to go dead very fast. I returned it and the shop tested it with good results. Back to the boat and it sucked again. ?????? The temp sensor circuit on my charger had died and it was getting summer charge settings. I got a new battery charger that could properly sense battery temps and the battery was fine once it was charged appropriately for cold weather.
Joe Coquina From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Ron Ricci via CnC-List Sent: Tuesday, February 07, 2017 11:55 To: cnc-list@cnc-list.com Cc: Ron Ricci <rvri...@gmail.com> Subject: Re: Stus-List Battery test Dave, If you used a resistor, you’d need 0.6 ohms at least 240 watts. Probably not practical. You could put a load on your batteries by turning on most of your lights, cabin fans and other loads. Ron From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of David Knecht via CnC-List Sent: Tuesday, February 7, 2017 11:32 AM To: CnC CnC discussion list Cc: David Knecht Subject: Re: Stus-List Battery test I have been following this discussion and would like to do this for my batteries. Can you suggest what would be an easy/appropriate ~20A load generating device? Dave Aries 1990 C&C 34+ New London, CT [cid:image001.png@01D28138.02844420] On Feb 7, 2017, at 10:15 AM, Della Barba, Joe via CnC-List <cnc-list@cnc-list.com<mailto:cnc-list@cnc-list.com>> wrote: Easy cheap way. If you have accurate volt and amp meters, a 20 amp (or near enough) load applied for enough time to drain the batteries 50%*. You should see 12.2 for wet cells and 12.3 or so for gel/agm. Light loads like 1-5 amps and heavy loads like 50-100 amps both will be inaccurate because of Peukert’s law. This law deals with the fact that a 100 AH battery can supply 100 amps for 1 hour or 1 amp for 100 hours in theory, but in practice 1 amp will last longer than 100 hours and 100 amps won’t make the full hour. 20 amps is a good value for these tests. * (AH capacity of batteries/load in amps) /2 = time in hours for 50% discharge
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