Total loss ignition system and Lithium Battery

Fast Eddie said:

If you’re running a sidecar outfit then why not use the JH mag that fits on the points housing?
The only downside to these is their vulnerability to a low side and limiting the ground clearance… neither of which is an issue with an outfit.

Click to expand...

The points area on the back of the timing side or the commando points housing? We are running an Atlas in the pre 62 class so I'd have to remove the tacho drive to fit it on the cam end and some machining to mount it in that location.

Connie73 said:

The points area on the back of the timing side or the commando points housing? We are running an Atlas in the pre 62 class so I'd have to remove the tacho drive to fit it on the cam end and some machining to mount it in that location.

Click to expand...

You could just use Commando timing cover rather than butcher the Atlas one.

But there’s no need, if you have an Atlas with the cases and timing cover components to drive an ign system at the back of the cylinder block then why not use a mag ??

A (good) mag is super reliable, needs no charging, no DNFs due to flat batteries, etc !

Connie73 said:

Measured the current draw with the Ign on and it was 3a. Note this was just rotating the engine by hand. Might be close to the limit for the 4ah battery when running?
I ordered a cheap lithium battery and charger to have a trial with so will see how it tests on the bench and the track. day.

Click to expand...

Rotating by hand tells you close to the max required. When the points are closed to one side, and you have a 1.6 ohm coil and a ballast resistor:

I=E/R: Current=Voltage/Resistance so 12.6v/3.2ohms=3.94amps. However, the points are no closed at all times and when not, there is 0amps flowing. Then you have to take into account two cylinders. And, on top of that, resistance is a static thing, but coils of wire have reluctance which can be thought of as is similar to resistance while stationary but different when charging/discharging.

The most accurate way to tell is an analog ammeter between the battery and ignition system. An analog meter will smooth out the fluctuations.

If the draw says around 3amps while running, then a 3ah lead/acid or AGM battery should supply all you need for one hour. A 3ah equivelent Lithium, quite a bit longer. To give you an example using batteries I know from Shorai:

LFX09 113mm L, 58mm W, 89mm H Will start a cNw e-start equipped Combat several times out of the box and never charged
LFX14 113mm L, 58mm W, 89mm H Will start a cNw e-start equipped Combat MANY times out of the box and never charged (size not a typo)
LFX21 148mm L, 82mm W, 140mm H Will start a cNw e-start equipped Combat a ridiculous number of times out of the box and never charged

The biggest Lead/Acid or AGM you can fit might start it 3-4 times before being weak.

It is important that you choose LiFePO4 which is often just called Lithium Iron. If simply called Lithium or Lithium Ion don't use it! It is also important that they be meant for motorsports.

You may have said it and I missed it: What are the dimensions of the battery your are using?

If charged with a proper charger, the voltage will be higher than a Lead/Acid. Although counterintuitive when thinking in resistance rather than reluctance, the required current is actually smaller - basically, coils use what they need when running.

Keep in mind that @Fast Eddie asked Shorai and they said no. I'm not sure if that was specific to the LFX range or how long ago. Personally, I would use them because I have experience and trust with the LFX series but that said, I would use a Shorai or NOCO charger between races and I would check the battery voltage before and after races. I probably would have two batteries and swap them between races to be absolutely sure to be not running close to the edge.

Lately, I've tried NOCO LiFePO4 which are more readily available and cost less. So far, I'm happy with them as well but I have no built up a trust level.

I dug out the email trail on this to clarify. It wasn’t actually Shorai that I spoke to, it was a U.K. distributor., they were not very specific about their reasoning to be honest, they seemed mainly influenced by the warranty topic and I’d now say that their option should not be taken as the final answer on the subject.

This was their answer:

To be honest I would not recommend running it on a total loss system - from our experience it's not a good idea - and Shorai themselves specifically say that batteries used on a total loss system are not covered under warranty.

Click to expand...

I asked them if they recommend any other lithium battery for this application (they sell other brands) but they never replied !

If you have not been talked into using a magneto yet, TGA uses Antigravity batteries in their race bikes. They also sell them. You could talk to Andy Molnar at TGA and find out what he thinks about using LifePo4 batteries in race bikes. He's not real chatty though. If you click on TGA in the first sentence it goes to the battery description on the TGA website.

I have the two Antigravity batteries I mentioned in post #18. I wouldn't use anything else because I have space limitations, don't like adding weight to a motorcycle, and they work. Unfortunately, I have no clue what they would do without an alternator. Molnar should know.

Yes, Andy says those batteries he sells are ideal for total loss systems. It is what they use on their own such systems (Ducati).

BUT he also pointed out that you must always stick to the 'rules' of use of them, particularly not to leave discharged, use proper charger, etc.

A couple of times when I was young, I took my bike to race meetings after paying the entry fees and other charges - only to have the magneto fail. I fixed the problem by fitting a rotating magnet Lucas magneto which had an external capacitor, which could be easily changed. The Boyer system is much better, but batteries are a nuisance.

Lithium batteries are great for reducing weight and holding voltage under load, but here are a few things to watch for:
Charging System: Your bike’s charging system might not be compatible with lithium. Check if you need a different regulator/rectifier.
Cold Weather: Lithium batteries don’t perform as well in cold temperatures, so starting might be harder if it's cold out.
Battery Management: Get a lithium battery with a built-in Battery Management System (BMS) for safety and longevity.
If your charging system is compatible and you ride in warm weather, a lithium battery could work well for you!

I had similar concerns with my setup, and what really helped me was switching to cr123a batteries wired in series for a compact, lightweight power source. They’re small but pack enough juice for short rides without lights, especially if you're just testing or tuning. I mounted them inside a dummy oil tank to keep things clean and hidden. Worked surprisingly well considering their size.

marshg246 said:

So, a 4ah battery ought to get you two races if fully charged and in good shape but I would give it some charge between races to be sure. A small Lithium would do better. BTW, in Lithium batteries, they specify AH so you can compare, but it's nothing like lead/acid or AGM if you read the fine print. A Lithium about the same size as the battery you are using has much more actual capacity.

Any tiny resistance in any component in the circuit will essentially "steal" power and depending on where you measure the voltage can make testing very confusing.

I attempt to explain that here: https://gregmarsh.com/MC/ViewPDF.aspx?key=uvd

Click to expand...

In terms of comparitive battery ratings only ( not physical size) , it's sort of other way around, unfortunately. An 18 ah lithium battery has the equivalent energy capacity to a 6 ah lead acid. The 18 ah rating is a pbeq rating taken from its ability to flow a high current for a short time. This ability is very useful for electric start applications, but for dead loss ignition use one needs to look at the smaller Lithium battery rating, which can be difficult to find. In general, just divide the lithium battery Pbeq rating by 3. A Shorai LFX18 battery has a pbeq rating of 18ah and a stored power rating of about 6 ah. This means it can, for a short period of time, crank over an estart as easily as an 18 ah lead acid battery but can only run a sustained load as long as a 6ah lead acid battery.
Regarding physical size, the two battery types are pretty close in stored power capacity ( not pbeq, which is fast discharge capacity) to space occupied. The YTZ lead acid series holds a slight advantage here vs Lithium.
For example, a Shorai LFX 18 occupies about 62 cubic inches and holds about 6 ah of stored power. A Yuasa YTZ7 occupies about 57 cubic inches and also holds 6 ah of stored power.
The lithium battery does have the weight advantage though. The LFX 18 is 1.05 kgs and the YTZ7 is 1.78 kgs.

Glen