hello
The pb acid battery I have now is pretty old and won’t take long until it fails so instead of buying a new Pb-acid with European terminals (cheaper but need adapters) or an imported battery from us I plan to try with a Lithium titanate pack of 5 cells. But these batteries draw much more current when charging them, more than li-ion or lifepo4 so it will cause the alternator to work very hard almost like shorting out the positive output to ground. The plan is to control the charging process based on the reading of the temperature at the diode bridge.
The maximum set voltage for the pack will be ~13.5V. I will leave the regulator in place but the output to the rotor coil will go through a solid state relay (dc) before going to the coil. Basically since the voltage will stay low the regulator will send 100%duty cycle to the relay. Using an arduino board I will control the relay with PWM at 500Hz. the module will also have a field protection diode and overvoltage spike diode. I’ll post updates as I do more on this.

 

What's a European terminal and why?

 

I meant terminals like on this:

 

Interesting process there, good work.

 

Hi, This alternator is the stock one I’ve removed from the car because it failed (loose stud connection). I have replaced the failed diode and soldered it but the other diodes are untouched the crimped original connection is solid, should be ok. On the car I have now an aftermarket alternator.
About the hysteresis, yes, it will be present. The thermistor is mounted on the bridge cooler, the one that has less cooling (the other one touches the case and is cooled by the case) and should pretty fast. I’ll also check the battery hysteresis but it should be less than a pb acid or lifepo4.
The battery pack will be made of 45Ah cells. The stock battery has like 70Ah but now since it’s old it probably has less that that plus the efficiency is lower, can’t do many cycles and should not be let to go lower than 40% so the usable capacity is pretty low.
Regarding the bearings, they looked ok but I’ve replaced the large one. Maybe it’s better to replace the small one as well.

Thank you for the info.




Here is the receiver module board that almost finished at this time. It features a power supply, two voltage dividers (one for voltage reading and the other for injector reading- there will be an eco mode-the car will run on battery unless it is engine braking), resistor in series with the thermistor to read the temperature, and a rotor diode. There is a problem with that diode, I’ve realised it needs a zener diode there in parallel with the field winding not a blocking diode. I thought it was used to prevent reverse currents. Actually it should be included in the stock regulator and it should do it’s job.

 

Lithium battery sounds awesome to save weight

not a fan of the european stuff (ex. I hate the sound of Corsa, which im told is a european sound)

 

here is the custom box for the modules



top center - 5v supply
bottom right solid state relay
top right: basically it’s a conductor with identical cross section area to the field wire and a thermistor glued to it. it should give some info about the current going through based on how much it heats up. for example if it goes above 100C it may mean the current is too high and there could be a risk of damaging the rotor.

 

I’ve installed the 45Ah LTO battery (this is 1.5-3 unlike li-ion or LiFePo4) and a BMS and I’m currently running on the stock alternator (no other module) and at over 90%Soc the battery still draws the maximum available current even at idle, about 110A, maybe higher than the alternator is supposed delivery safely. In the service manual they stated the alternator has a thermal protection circuit so it should limit the current based on that. Basically it heats up within a minute then it stabilises and the current goes down to 50A or lower, I can’t confirm it’s because of thermal protection or because the voltage of the battery rises as it approaches the full SOC. There is the cs144 with versions that go up to 250A but that would only change the speed of charging, it would still run under maximum load, plus the charging cable would definitely need to upgraded. Firs thing I will do is to stick a few small radiators on the alternator over the diode bridge to try to bring the temperature a bit lower. By touch I estimated the temperature around 120C. Then I could design the module I worked on either with lower temperature settings than stock or to limit the current to say 80Amps at idle and 100A at max rpm.

 

Seems like a lot of work. My old lead battery seems to work fine. But I give you credit for doing it. Dan

 

thank you,

IHDB, I think I can confirm what you were saying.
I ran the car for about 15min on the battery only (the PLFS plugged out) and then I reconnected it to charge again to see what happens in a case where the battery SOC is lower. At idle the alternator produced 91A and 105@2000rpm engine speed (I think it’s 2.7 pulley ratio). It needed a few minutes to charge, ~4 minutes. Shortly after I started the engine the alternator heated up. During this time I was monitoring the temperature of the coil pack and diodes and I noticed the stator coils were much hotter. At some point the coils, reached 170C and I stopped the engine. The diodes had 120C and the armature about 95C. After it cooled down I restarted the car and the battery fully charged with the current dropping slowly to only 10A.

So the conclusion is there is a risk of overheating the coils, while the diodes remain ok. The alternator has overheating protection but it must be for the electronics not for the coils. The alternator needs either improved cooling, extra temp/current management or can run normally provided the SOC of the battery is close to full otherwise it will exceed the maximum designed temperature

I’ll start researching for designing a module that outputs a higher voltage to the sense (S)terminal to control the alternator output rather than modifying the alternator (my previous design), it’s seems much more convenient.

 

agreed, especially if you scale all four wheels and realize the benefits of simply relocating the heavy lead acid battery to behind the passenger seat in the storage compartment, or an agm on its side back where the spare tire holder is. thats a lot of added complexity and cost for almost no gain compared to a simple 92-96 alternator upgrade with a relocated battery.

 

I was wondering where is the probe that measures the temperature of your alternator located?


Another very simple way I thought for offsetting the voltage (so that the alternator dials back the duty cycle by itself) is to use a peltier plate that produces voltage when there is heat difference between the faces. The more heat difference the higher the voltage so the higher the alternator gets the higher the voltage offset. Then a potentiometer can be places in parallel to adjust the offset limits.

 

Nice engineering, but aren't you concerned about the possible fire hazard using a lithium battery? That thing sits right in front of your feet...

 

Hi IHBD,

When I measured the temperature of my alternator the stator armature iron core was about 100-110C but the windings were 170 based on the thermal camera reading so if you stick the sensor to the case when it gets to 110C the windings could also reach 170C or higher so it may be that the 110C setpoint is a bit high or it reacts differently than a lower amperage alternator. For example if you expose yours to maximum higher load, the windings would get hot quickly before the heat passes to the iron core.

 

The alternator is designed to deliver 119A maximum output so the wires should be able to deliver that current normally. Otherwise the LTO battery (unlike LiIon or even LiFePo4) has a safe chemistry just like a PB acid so it’s as if you were running with a larger Pb battery. These would be perfect for mild hybrids that because they use small capacity packs they end up doing many cycle per distance than a larger pack. the LTO’s are supposed to live up to 25.000cycles.

 

Nice to see a fellow arduino enthusiast.

BTW, GM alternators 2006 to 2016is are variable voltage and controlled by PWM. They have the 2 pin connector. You can command the alternator to put out any voltage you want. Here's a link to the alternator info. https://ls1tech.com/forums/conversio...hrow-away.html

 

thank you
this one requires some custom brackets I understand. Also I would need to modify the wiring of the car. Otherwise, I think it has better efficiency , cooling and it’s easier and safer to control
But, I’ll try with the stock alternator and make it plug&play.

 

I managed to make the module work, the project is like 95% complete,I only need to don some crimping of a few terminals, wire RFI shielding and some software tune or improvements.
What it does is sending a low voltage to the Sense wire of the alternator or higher voltage up to +16V when it needs to lower the output. There is also a relay and when the batter voltage is above a limit like 14.7V it automatically switches the output to sent the battery voltage directly to the Sense. Anyway this seems redundant because I noticed whenever the voltage to sense is lower than the battery voltage (basically internal reading of the stock regulator) it ignores is which is good. for the next version of this module I can remove this feature to make the module more compact. Also I’ll try to replace the board with an arduino nano and try a remote display and keyboard.
The module takes input from a thermistor on the alternator case and from an injector. It has voltage and temperature set points that can be adjusted and saved into eeprom. Currently there are two voltage setpoints. I’ve chosen 11.5V normal mode and 14V during engine braking. Basically, during engine braking most cars don’t inject fuel (I don’t know about my corvette, I’ll try to find out) so charging the battery while in this phase saves energy and there can be less load or even zero when accelerating although there will be lower voltage to injectors and fuel pump which may end up in fact in less power produced if the computer doesn’t know to compensate for that, idk.
I inly did some testing at idle and it seems to work as desired.
Before installing the module I’ve also added a fuse box and a relay that is energised while the ignition is on. I tried to find the connector for the sense cable at the other end with no success so I ended up cutting the cable is which is not a big deal. I cam organise the cables to look nice.




the case is 3d printed PLA, heat treated to withstand up to 300F. I will mount it below the ECM at 90deg. You can see negative temperature because the sensor is not connected and 4.3V from USB power supply. The other T stands for True meaning the relay is energised, E - Eco mode since no ignition detected, D -Duty cycle, S setpoint 90C and 13.7V.

 

I’ve checked again that alternator and found the dimensions. I think I can install one on my car. Possibly with the same top bracket, mill a bit from the top mount of the Alternator and a longer drive belt. But I think it’s better to do a new stronger bracket and let the alternator as is. Then my module can perform all the functions I need much more reliably. It also has a freewheel system that helps, better cooling as well.
But for now I want to see how the stock one performs. Last time the control parameters were totally unacceptable and was cycling full output to zero each couple of seconds and now the drivebelt started squeaking

 

Lots of cool custom work there. It's inspiring me to convert an atv I have to electric. And lowering weight is great not just if you race you really start to feel it in the braking zone too.