How To: Alternator delete
 

http://www.metrompg.com/posts/photos/alternator.gif

I have recently found out that the battery in my Metro doesn't have a ton of life left in it. Being an ecomodder, I instantly think this is a great time to do an alternator delete mod. So, I figured I'd go through the steps of figuring out how to actually do an alternator delete for anyone who doesn't know already.

http://www.tercelreference.com/downloads/prius024.jpg

Step one is to figure out how much power your car uses so you can size your battery correctly. This is probably the trickiest part to do. The best way to do this is to measure your electrical power consumption with an ammeter. However, for those who don't have an ammeter, Darin posted a great thread on electrical loads a while back which I'm quoting below. Its a pretty comprehensive list, and your car likely doesn't have all these goodies. The Metro sure doesn't. However, you do want to calculate a worst case scenario to size your battery so you know you have enough power no matter what. If you compromise on battery capacity, you'll have to keep that in mind as you drive daily.



For my specific case, I know the exact electrical loads thanks to Darin and others on this forum. Here is an exact list of electrical loads for the Metro.

So, for my example lets add them up to get a worst case. My worst case scenario is a winter commute of ~15 miles per day. This equates to roughly 30 minutes of driving. Obviously the engine must be running for some of this, and the engine pulls roughly 140W or 10A. Since its winter, I want heat, so my fan will be on some of the time. I'll use fan setting 3/4 for 140W or 10A. Its also dark out, so my lights will be on which uses 240W or 20A. The total for these loads is 40A.

This means I'm using 40A for 30 minutes. Battery capacity is rated in amp hours (Ah). So, if I use 40 amps for a half hour, I've used 20 Ah. This would be just enough power to get me to work and back under a typical bad weather scenario. However, I do take the occasional trip that is longer than 15 minutes, and what if I want to run some errands after work? Well, we need more capacity.

In my case, I don't use the Metro for long hauls. But, I go to occasional lunch meeting and what not. So, I would like to aim for 1-1.5 hours of run time. Using the above calculation, for 1.5 hours of run time at 40A, I need 60Ah of battery capacity.

So, I need 60Ah of usable battery capacity. If I go with lead acid (which I probably will), the rule of thumb for optimum battery life is to not exceed 50% depth of discharge (DOD). This means don't discharge the battery beyond half of its capacity. Now, for 60Ah of usable capacity, I need a 120Ah battery. This is what I should be aiming for. Quite a far cry from the 20Ah I initially calculated.

If you wanted to get fancy and go with lithium, their rule of thumb for DOD is 70-80%. This means you'll only need a 80-90Ah battery.

Sizing the battery in this manner will ensure that you have enough power to get around without the alternator without worrying about it, and it will also ensure that your battery will live a long happy life without you abusing it.

So, that is step one.

A 120Ah battery is fairly large, so we'll see what I can actually fit into the engine bay of the Metro. I may compromise and drop down to a smaller battery and just use the alternator for those longer trips, then turn it off on the way home.

Since you are going through all this trouble, why not mount the battery else where for better weight distribution or inside for better regulation of operating temperatures?

Its a Metro, not a race car. :) The weight distribution is fine for daily driving. Having it inside the cabin would be nice, but not worth the hassle of running wire, mounting, etc.

Im pretty sure a 120 amp, group 27 deep cycle battery in the trunk would really balance out the 3 cylinder under the hood. :snail: 2 group 24s, etc arent light either.

Obviously a 120aH lead acid battery is the cheapest way to go, but ideally, a DC-DC converter should be used to maintain constant accessory voltage as the pack starts sagging.
I would do a 48V pack & charger (lithium, of course :D) with a DC-DC convertor down to 13.5V.

Is it possible for you to chuck the alternator belt, or does it drive other accessories? The nice thing about my Civic is that it has three belts, one for each accessory that I could potentially delete.

I'd go LiFePO4 to get deeper depth of discharge and longer life, along with weight savings.

The voltage should remain higher during discharge than a lead-acid battery.

I run a similar setup with a dc to dc converter in my honda. I wouldnt delete the starter battery as there are times the converter cuts out or rolls back output.

Then you got the ROI. In my case I had all the parts, it was just a matter of wiring it all up. :thumbup:

Thanks for the suggestions guys. I may have to go with something like that. I tried a couple batteries in the Metro this morning and it is looking like I have a height clearance problem.


Here is the stock battery.
http://ecomodder.com/forum/attachmen...1&d=1414869368



Here is the stock battery next to a group 31 battery, what I'd ideally like to put into the Metro. Slight size difference. The thing you can't see in the picture is that the group 31 is over an inch taller.
http://ecomodder.com/forum/attachmen...1&d=1414869368



Here is the group 31 battery in the Metro. Looks almost comical IMO.
http://ecomodder.com/forum/attachmen...1&d=1414869368



However, this is what happens when you try to close the hood. So, the group 31 battery definitely will not fit under the hood. Bummer.
http://ecomodder.com/forum/attachmen...1&d=1414869477



Now, here is a group 24 battery I had kicking around. I managed to get it under the hood and the hood even closed. However, its really only on the tray a little of half way, so I'd have to modify the battery tray to hold it properly.
http://ecomodder.com/forum/attachmen...1&d=1414869496



So, I'm looking at a few different options at this point:

First off is seeing what kind of capacity I can get in a group 24 lead acid battery. If its 80-90 I might just settle for it as it'll be the easiest thing. Modify the battery mount and be done.

The next option I have is going with a smaller battery up front, and sticking a group 24, 27 or 31 in the back somewhere and using a DC-DC converter or something as Mechman stated. I like this option as it runs a more normal voltage while driving. But, honestly I didn't have any issues running without that on my Paseo when I had an alternator delete. I'd also need to find a DC-DC converter capable of pumping out around 40A which isn't a tiny amount of power.

The third option would be go size a ~100Ah lithium pack as redpoint5 stated. This would be the most expensive option, but it should theoretically last quite a while. I'd need lithium cells and a lithium charger at the least, possibly a BMS.

this isnt a cheap idea, and the work mounting may not be alot easier than making a trunk mount, but would a group 31 AGM battery fit on its side?

Ive used an electric wheelchair for 9 years and with deep cycle lead acid batteries they take 10-12 cycles before they build up capacity with use. Ironically they start to charge faster and hold the charge longer once they break in. :thumbup:

Those are nice wheels on the prius to the right. Is it yours?

http://ecomodder.com/forum/attachmen...1&d=1414869477

The first time that I remember changing a car battery, I had my little brother carry it into the store. The employee said "Hey! Watch it! He is going to get battery acid on him!"

I had him set down the battery, took him into the bathroom, and washed him off.

His clothing suddenly had holes.

AGM batteries are dry. No water. Nothing to leak out. They can be used on their side just fine.

Yeah, I think it would probably fit on its side.

Yep, the Prius is mine. My wife drives it typically. The wheels are just the stock wheels on any 2nd gen Prius. They have the trim rings removed because I modded them for pizza pans (which didn't end up working).

What I'm currently thinking is that I have four LiFePo4 A123 amp20 (20Ah) pouch cells. I've always wanted to use them on a car because they are ridiculously light weight. I'm thinking of using those up front and fitting another lead battery somewhere else. I just have no idea where yet. I'll have to come up with some way of monitoring both batteries. Still not set on the idea, but its a possibility.

I just emailed a local guy trying to get rid of some old Thundersky 200Ah cells with ~100 cycles on them. Yeah, they're massive overkill for an alt delete, but if he is willing to let them go cheap, I can make it work.

Still looking into options.

Dropping in a group 24 would still be by far the easiest thing to do and would suit most of my needs.

Modify your hood to look like you have a turbo. :D

http://www.siberi-inn.ca/pix/Talon(r6959)s.jpg

Battery chargers are cheap.

Hobbyking

Mostly for my own reference, these are the lead acid cells I'm looking into:

group 24, 80Ah, $72
group 27, 105Ah, $75


Ironically, the little 26R OE replacement costs even more than either of the deep cycle batteries above:

26R starting battery, $89


So, its actually cheaper to go with either of the batteries that'll allow me to do an alternator delete... Works for me. :D

Lol, a Metro with a hood bump... I'd laugh at that. :)

Actually, I was thinking that you could modify your hood like Aerohead did trying to make the front more aerodynamic. I know that he did not see an improvement, but you could fit all kinds of batteries in there if you raised the roof! :)

That is a strange love note for your wife!

Haha, nice catch. :)

I'm contemplating 4 of these. $200 only buys 40Ah of LiFePO4, but at least I can go to 80% depth of discharge safely.

What depth of discharge would you be willing to go to on your deep cycle battery?

I'm leaning toward just getting the 80Ah group 24 battery. It'll give me my ~1hr of run time without abuse which is still more than I need for nearly all my driving. Mostly I want that because it'll drop right in, and I have a nice 5A onboard charger for it already.

The other options are all superior function wise, but cost a fair amount more and will require additional modification.

I'd be willing to go with over 50% dod with lead, but not often at all.

Do not use a LiFePO4 battery up north unless you plan on removing it from the vehicle when its cold out.
I have LiFePO4 cold issues and I am in new mexico.

Issues being what?

We have a bunch of guys running around in LiFePo4 EVs here, no issues.

I have cold cranking power loss anytime they get much below freezing and the fact that charging them when the battery its self is at temperatures of 5'F and below can permanent damage to them in the form of lost capacity.
If you are talking about using a LiFePO4 battery of at least 80 amp hours to start a 3 cylinder engine then it might not ever be a problem. I don't believe I have read anything saying cold discharging permanently hurts them.
When it gets much below freezing my 67 amp hour LiFePO4 battery has difficulty starting my diesel, but that's 395 cubic inch, 22:1 compression V8 with a gear reduction starter.
But the way power output from these batteries drops off when cold I wouldn't be surprised if it could get cold enough in WI to where an 80 amp hour battery couldn't start a metro.

Do these electric vehicles have temperature regulated batteries?

I doubt they do. But I could be wrong. I also don't know if the owners baby them, or they're kept in a warm garage, etc.

One more reason to stick with lead.

Oh, I thought I had read that the leaf used actively pumped liquid to cool the batteries during summer. Then figured it was reasonable that the pump coolant could also be warmed for winter time use.
But I have learned, just because that is how I would do it does not mean the OEMs will do it.

I have read that LiFEpo4 is safe to discharge down to about 0 F, but should not be charged at any significant rate if below 32 F.

The way I see it, LiFePO4 will work in my alt delete because I garage my car, where it would be safe to charge. Also, on a longer trip where I need to turn the alternator on to charge the battery, heat from the engine would keep temps above freezing.

Aerodynamic cars, properly-geared manual transmissions, smooth wheels, smooth bellies, auto-stop, what else would we do differently? :)

That a boy. :thumbup: 2 group 24s in the rear where the spare tire ought to be will make it take corners like no ones business. :eek:

Thanks for posting this. I'm thinking about doing this in my Camry. I can remove the belt and run belt free! Which I think will get me some decent gains! Is it ok to charge a deep cycle battery using the alternator? Like say going on a trip longer than the battery can last? Also I was thinking about getting a low wattage solar panel to stick in the dash of my car to trickle charge it while the car is parked say at work or home.

Yeah, the deep cycle will be fine being charged by the alternator. If I have a trip too long I'll be using the alternator. As I progress with this thread, I'll be installing a switch to turn the alternator on and off. I haven't determined exactly how I'm doing that quite yet, but that is one of the next steps.

A solar panel has generally been considered a poor way to charge the battery though, they just don't put out enough power to be worth the cost. It is a very cool idea though.

A solar panel has generally been considered a poor way to charge the battery though, they just don't put out enough power to be worth the cost. It is a very cool idea though.[/QUOTE]

Even sitting in sun for 8+ hrs

Yep, even with it sitting in the sun for 8hrs a day. As I mention in my first post a lot, we have to think about worst case scenario. Worst case is a cloudy week. Unless you have a massive battery, its not going to last a week for you, let alone a week in winter when there is nowhere near 8 hours of sun per day. Then, you add in the other little factors like the windows have UV protection and/or tinting which reduce the panel output. And solar panel output isn't optimal unless the panel is tilted perpendicular to the sun (ie sitting on a dash). The little things start adding up, and the size of the panel you need keeps going up, and you still need a charger for that week where there is absolutely no sun.

A few guys have done it, and I agree its a very cool idea. But IMO there are a lot of other mods that are a lot more beneficial and reduce my commuting cost a lot more. Thus its an idea I'd consider, but its way down on my list to the point I'll probably never get to it.

Thanks! I'm excited to do this modification and see how much mpg gain I see.

A 5 watt panel in direct sunlight for 8hrs will produce 40 watts of energy assuming no charging losses. My car requires a minimum of 163 watts to run, so 8hrs of charging will get me 15 minutes of run time if I run absolutely no accessories.

Thanks :)

If I do run beltless will I still need to unhook the alternator? Will my scangauage still read?

Your car will still run if you have a bad alternator until the battery dies, so as long as your battery lasts, your car should run fine.

I would still disconnect the wires to the alternator if you run beltless, but I'm unsure how your particular car controls things.

On my car, a small current is supplied to the alternator to activate the field windings. Even if I remove the belt on my alternator, it will still draw some amount of power in an attempt to activate the alternator. My car uses 4 wires to the alternator to control and monitor charging. A large 5th wire is the actual positive output lead that goes to the battery and powers the car.