| [GMCnet] Alternators [message #345768] |
Fri, 26 July 2019 18:04  |
glwgmc
Messages: 1014
Registered: June 2004
Karma:
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Senior Member |
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As part of the research I have been doing for a presentation I am giving at GMCWS in October on whether or not to upgrade a GMC to Lithium based batteries and if so, how to do it properly, I have been examining alternatives for our stock alternators. Anything larger than a 100ah LiFePO4 house battery bank could really tax our stock alternators. There are electronic devices that can resolve the issues surrounding the two different voltage regimes in which lead/acid and LiFePO4 batteries function, and even a few designed to lighten the load on the sub 100 amp alternators like those in most of our coaches. Those generally operate by limiting the alternator duty cycle by allowing the alternator to send charge current to the house battery bank for something like 10 to 15 minutes out of every 30 or so minutes the engine is running. The reasoning is that will allow the alternator to cool down sufficiently to prevent over heating the alternator during the relatively short time it takes to recharge lithium house batteries which accept way higher charge current than their lead/acid counterparts - basically everything the alternator can put out. These have no effect on recharging of the starting battery. They also serve as a battery isolator when the engine is turned off.
Given the recent dialog about serial alternator failures I am wondering whether these $200 smart duty cycle control isolators might not also be a good idea for all our GMCs, even the ones with lead/acid house battery banks. Yes, it might lengthen the time required to fully recharge the house batteries if you kept your lead/acid battery bank, but it wouldn’t matter if you were charging lithium batteries which charge in a fraction of the time it takes lead/acid batteries to recharge anyway. Would they cool off the alternators enough to keep even the cheap rebuilt units alive a lot longer?
One question for the whole group. Have any of you found a higher output alternator that will fit the stock mounting supports that can be successfully driven off of our stock one or two pulley V belt drive? Or, have you found a way to add a second alternator without too much fabrication or having to spin the water pump the wrong direction?
Within the last couple of years appropriate lithium battery technology has changed a lot with the addition of sophisticated, on-board battery management at the cell level and automatic cell balancing that makes these a safe and reliable choice for our application. And, prices have come down to the point that it will be hard for many of our GMC owners to resist the many, many benefits of lithium over lead/acid house batteries, but I am still concerned about how to solve the issues surrounding keeping our 40 year old, sub 100 amp first generation alternators alive. So, I am all ears on your suggestions.
PS - I really don’t want to debate lithium vs lead/acid batteries in this thread, so wait until after the presentation to do that. I would like to keep this thread focused just on the alternator question. Thanks.
Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR
glwork@mac.com
http://jerrywork.com
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Jerry & Sharon Work
78 Royale
Kerby, OR
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