Quote:
Originally Posted by redpoint5
Ecomodding is a legitimate hobby, and as long as it brings joy, I see no need to rationalize the time and expense that goes into a project. I'm experimenting with supercaps and LiFePO4 batteries knowing full well that I'll never recoup the cost.
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Aha, yes, I understand that LiFePO4 batteries are more efficient and don't particularly suffer if operated at lower states of charge.
From what I understand, lead acid batteries really suffer a lot if not recharged to 100% between cycles, but perhaps this charge acceptance inefficiency at near full charge means that I would be better off not allowing one battery to actually recharge another while driving. With that in mind, designing a system so that in normal use BOTH batteries are being discharged might therefore be more efficient. So if using a DC/DC converter it would be better to use a relatively low-power one. Or else just use a simple parallel connection with no converter.
(But wait, ...if efficiency falls as charge nears 100%, that is also when the actual charge RATE reduces right down, so the absolute energy loss is perhaps not that great.)
At the moment I'm thinking of a no-compromise system which also won't be expensive:
1. For normal local driving I use my existing two good quality deep-cycle-capable AGM batteries in simple parallel arrangement.
2. For longer journies I drop in an additional 90Ah AGM 'leisure' battery (a free warranty replacement for the cheap one I wore out with three months of daily deep cycling) I plug that into the installed 12A DC/DC converter to take the strain off the other two batteries.
I won't worry too much about how long the drop-in cheap leisure battery will last as it will only be used once a month or so. This arrangment means that if there is no means of plugging the car in to charge at my overnight location (like city on-street parking for example) I can either keep the DC/DC converter running overnight to put as much as possible back into the other two batteries, or else carry the leisure battery indoors and use a portable charger to recharge it overnight. (Or both: I can leave the converter running a few hours on arrival, and then at night carry the leisure battery indoors to be recharged.)
This will also mean I am maximising mpg on local drives as well as on long dirves as I won't be carrying that extra 25kg unless it is being used.
Quote:
Originally Posted by redpoint5
For lead acid batteries, efficiency and longevity are at odds.[/B]
For this reason, I have become interested in exploring alternatives to lead acid batteries.
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Yes, I can see that. I'll be interested to know how you get on with the LiFePO4/supercapacitor arrangement. That has to be the future. I was thinking of locating all batteries in the rear and just having a parallel-connected supercapacitor array in the engine bay for engine starting.
Actually I think the future is also to have solar cells built into the paint layer of vehicle body panels and/or the use of photovoltaic glass. That would happen at manufacture of course. Most vehicles are being driven less than 5% of the time and spend all day soaking up solar rays. Again, batteries which are efficient and long-lasting at partial states of charge would be needed in order to take full advantage of solar cells.