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Old 10-22-2019, 03:23 PM   #1 (permalink)
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Location: Germantown, WI
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CM400E - '81 Honda CM400E
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Swarthy - '14 Mitsubishi Mirage DE
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A better alternator delete

I think alternator deletes are a really great mod. They give you a sizable gain for just one modification. I've had them on just about all my daily drivers for the last decade. However, they just are not usually cheap. First off you need a deep cycle battery. If your starting battery is fine, its hard to swallow $80 for a new battery. If its dead, its not too big of a deal. Then, you need a charger for this battery. Let’s say this charger costs you $50 (I'm pretty sure mine cost more). Now you're up to $130 for a single modification. Next, you need to actually do the mod which can range from inserting a switch in some wiring to coming up with a small electrical circuit like I've had to do on my Mirage. Lets say this costs another $10 for a total of $140 for an alternator delete. Yay, you get a nice bump in MPG, but that $140 can get you a lot of gas too, right? What if there were another way?

You've probably already seen my post on battery hookup. If you haven't, I highly suggest it because it seems like a great place to get some lightly used lithium batteries. They're keeping these things out of landfills and getting us DIYers a great source for lithium batteries. With the prices they have I've been thinking more and more about what I can do to improve mpg via battery use without spending a small fortune.

My idea for today is a portable lithium battery pack that essentially doubles as an alternator delete. What I'm talking about is a smallish lithium ion battery pack that is 15V+. This pack has a voltage regulator on it that sends the 15V+ to your car's 12V battery via a PWM signal. The power out of the portable pack will keep the car's system voltage just above the voltage set by the alternator, thus disabling it. This is the same idea I used on my Mirage to disable the alternator and it works great. When the lithium pack is depleted, your car goes back to using the lead acid starting battery as normal.

I'm pretty sure we've talked about this before... kind of. A lot of you apartment dwellers don't have access to outdoor charging. This portable pack solves that problem. Take it in at night and you can charge it in the warmth of your building. This also solves the problem of some lithium cells not being able to be charged at freezing temperatures. When you go out to the car in the morning, simply plug the pack into your cigarette lighter (or other plug of your choice) and you're ready to go.

Another benefit of this is that your car's system voltage is actually where it is supposed to be, not at 12.X volts. This means no more dim headlights at night, or slow wipers. Also, no hacking car wiring. This thing literally can plug right in, and come right out.

On top of all that I also think this is doable for less than the 'old' way of doing an alternator delete. Here is my guestimates for cost:

lithium pack - $30 (from battery hookup)
5S bms - $13 (price from amazon)
5S charger $17 (price from amazon)
voltage regulator - $15 (DIY circuit? rough guess)

Total: $75

So, roughly half the price. If you use a cigarette lighter plug you can literally use this thing on any car you jump into.

Current project: A better alternator delete
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