MR2 SpyderChat banner

41 - 60 of 67 Posts

·
Registered
Joined
·
44 Posts
I started the post because I am out of space in the engine bay. I need room for my intercooler, heat exchanger(s) and pump. I am not really looking at it from a weight reduction standpoint. Completing the intercooler alone is worth WAY more from a performance standpoint than a few pounds removing a battery will provide. I expect to bump the boost up substantially with the chilled intake charge. Given that I'm in Colorado a large capacity battery for cranking in well below sub zero temperatures is absolutely required. I just need to figure out where to put it.
Optima yellow top in the frunk will more than suffice. make sure you use at minimum 2 gauge wire for the relocation. I recommend using welding cable.
 

·
Registered
Joined
·
1,659 Posts
I've said multiple times the anti gravity is less than 4lbs. 3.79 to be exact, to replace the group 51, same exact battery in my race car. Not only does it weigh less but physically smaller. But hey, if you are happy with your setup more power to you. I also only own fun cars, My daily driver is a BMW 135i Msport 😁
If it's only 3.79lbs, it's a motorcycle sized battery, not a 51R replacement: Group-51R Lithium Car Battery – Antigravity Batteries
That's totally fine if it's driven frequently, kept on a charger, or unplugged. I prefer more capacity :)
 

·
Registered
Joined
·
151 Posts
I have a LiFe battery of 800 gramms in the stock battery tray. Had in our rakkley car for 2 years, now in the MR2 for 2 and it starts on -0 C. mornings.
 

·
Registered
Joined
·
44 Posts
If it's only 3.79lbs, it's a motorcycle sized battery, not a 51R replacement: Group-51R Lithium Car Battery – Antigravity Batteries
That's totally fine if it's driven frequently, kept on a charger, or unplugged. I prefer more capacity :)
Yes it is considered a motorcycle sized battery, More room for activities, but it is very powerful. I haven't fully tested how long I can go before needing to use the automatic restart function of it, but like I said I have went 11 days without starting the car and didnt need to use the automatic restart.

This is the one.. amazon has it for less than 300 free shipping

 

·
Registered
Joined
·
638 Posts
I started the post because I am out of space in the engine bay. I need room for my intercooler, heat exchanger(s) and pump. I am not really looking at it from a weight reduction standpoint. Completing the intercooler alone is worth WAY more from a performance standpoint than a few pounds removing a battery will provide. I expect to bump the boost up substantially with the chilled intake charge. Given that I'm in Colorado a large capacity battery for cranking in well below sub zero temperatures is absolutely required. I just need to figure out where to put it.
From following your builds projects I know you're running out of space to cram things otherwise my smart ass would have said to relocate to the rear subframe i totally understand going for a smaller battery to save space in the new location, but you def need those CCA for Colorado.
 

·
Registered
Joined
·
1,004 Posts
Discussion Starter #48
From following your builds projects I know you're running out of space to cram things otherwise my smart ass would have said to relocate to the rear subframe i totally understand going for a smaller battery to save space in the new location, but you def need those CCA for Colorado.
Yeah, it would cook on the rear cross brace. It gets quite warm back there when not moving. I worry about the meth tank even with the heat shield in place and it's all the way over behind the passenger rear tire.
 

·
Registered
Joined
·
1,659 Posts
Okay FYI, I got my hall effect ammeter today and went and tried it on our old Honda Pilot (3.5L). Temperature was 60F, so it's easy cranking. My s***ty multimeter doesn't respond very quickly but I saw it read 233A at the highest (quickly dropped down below 100 though). The car was drawing 9A with the engine off. The true peak might be more like 300.

I would expect a 2ZZ to show 130A at the same temperature, maybe more like 200A on a cold Colorado day (last time I went to Vail, it was like 10F? I felt pretty cold lol), though on a cold day the battery would be putting out less voltage under load. I think 200 CCA is enough for a 1/2ZZ or K20.
 

·
Registered
Joined
·
1,004 Posts
Discussion Starter #50
The locked rotor current doesn't really tell the story. I think your steady state current is more real. Still 100A is quite a bit. That's over 1HP even when the battery sags to 10V. I'm a little surprised it takes that much amperage to turn over such a small engine but I guess the high compression contributes quite a bit. Thanks for the numbers. I can now run my voltage drop calculation for the cable run to the frunk.
 

·
Registered
Joined
·
1,659 Posts
Steady state with the fuel injectors disabled would be lower yet, because as the speed increases, the motor current drops very quickly because the momentum of the engine helps with the compression cycles. I would surprised if steady state were more than 50A on a 4 cylinder.

I still think peak current is most important to look at since the starter efficiency is lowest when it's spinning slow and the current is high. You want to have plentiful amperage=torque to break static friction and get the engine moving as fast as possible.
 

·
Registered
Joined
·
1,096 Posts
Hopefully you never reach steady state current when trying to start your engine. If the engine doesn't start right away and you do get to steady state, don't keep trying to start the engine without taking a break in between cycles or you can damage the insulation on the starter windings.

Since the starter is series wound, its torque is proportional to the squared armature current. So, a lower battery voltage means significantly less starting torque will be available to turn the engine over.

That is why CCA's, or a very low cold temperature internal battery resistance is important.
 

·
Registered
Joined
·
1,822 Posts
... as the speed increases, the motor current drops very quickly because the momentum of the engine helps with the compression cycles...
As speed increases, the motor current drops because the motor produces a voltage that bucks the battery.
 

·
Registered
Joined
·
1,659 Posts
As speed increases, the motor current drops because the motor produces a voltage that bucks the battery.
Yes I'm aware of back emf. The peak cranking torque requirement is largely due to compression, and that is smoothed over considerably once the engine is spinning, so the cranking current peaks go down faster than (x-a)^2+b (series winding).
 

·
Registered
Joined
·
1,004 Posts
Discussion Starter #56
Did you ground up front?
I too would like to know this. I pulled the positive cable all the way to the frunk but I was going to use chassis for the ground and negative side breaker.
 

·
Registered
Joined
·
1,096 Posts
... and negative side breaker.
I would definitely place the breaker on the positive side protect the battery and cable. If you are going to use the chassis as the primary ground, I would add another engine block to body ground strap or put a new physically larger ground strap in its place.
 

·
Registered
Joined
·
55 Posts
I haven't had any issues running either a home made A123 lithium or Factory produced LifeP04 batteries in the six or seven years I have been using them in daily driving from 14 degrees to 99 degrees. I do use two batteries for the 14 degree mornings :) Otherwise it is a very slow start.
I haven't had any issues running either a home made A123 lithium or Factory produced LifeP04 batteries in the six or seven years I have been using them in daily driving from 14 degrees to 99 degrees. I do use two batteries for the 14 degree mornings :) Otherwise it is a very slow start.
Hi there kind of new here , what lithium battery would you recommend? Sounds like you have been running that set up for awhile and know what works and doesn’t I am a weekend warrior looking to save weight free up engine space but still use heat and air and not cook anything any help always appreciated !
 

·
Registered
Joined
·
1,302 Posts
Yeah, it would cook on the rear cross brace. It gets quite warm back there when not moving. I worry about the meth tank even with the heat shield in place and it's all the way over behind the passenger rear tire.
If you can get by with a motorcycle-sized Li-ion battery, there is plenty of room in front of the pass-side taillight. I built a simple bracket there to hold the battery. Doesn't require much heavy gauge cable, and for a 4-lb battery, the effect on handling is nil.
 

·
Registered
Joined
·
55 Posts
If you can get by with a motorcycle-sized Li-ion battery, there is plenty of room in front of the pass-side taillight. I built a simple bracket there to hold the battery. Doesn't require much heavy gauge cable, and for a 4-lb battery, the effect on handling is nil.
If you can get by with a motorcycle-sized Li-ion battery, there is plenty of room in front of the pass-side taillight. I built a simple bracket there to hold the battery. Doesn't require much heavy gauge cable, and for a 4-lb battery, the effect on handling is nil.
Thanks are you currently running one I’m just fair weather driving want to run ac and accessories that’s it
 
41 - 60 of 67 Posts
Top