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TOPIC: Do you really need a special rectifier/regulator for Lithium Batteries?

Do you really need a special rectifier/regulator for Lithium Batteries? 08 May 2019 06:23 #803500

  • dpivas7
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I bought a Shorai lithium battery because I'm sick of the lead acid battery giving me issues, but I didn't do a ton of research beforehand.

I figured there would be no problem by just hooking the wires to the battery terminals, but I found some threads on here that *recommend* that you get a mosfet rectifier/regulator from Oregonmotorcycles, Rick's moto, or Spark Moto.

However, the Shorai battery that I got (LFX model with 210 cold cranking Amps) said: the battery "requires a charging system output of 13.1 Volts or higher at idle, and must not exceed 15.2 volts at maximum output."

From what I've read, the stock rectifier maintains a voltage of 14.5V. Why would I need a rectifier/regulator that outputs a reduced voltage if the stock part is right in the middle of the range the battery likes to be at? I think I'm missing something here.
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Do you really need a special rectifier/regulator for Lithium Batteries? 08 May 2019 09:23 #803517

  • GUTS
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I've been using Shorai batteries for about 5 years in my Z1A, Z1B, and my 1976 LTD and I have only had one problem and I don't think it was a battery/electrical miss-match. I had a voltage regulator go bad and fry the battery once on the Z1A while I was riding but I replaced it and haven't had any problems since. I think the regulator was bad when I put the battery in(I didn't check it until the battery fried).

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Do you really need a special rectifier/regulator for Lithium Batteries? 08 May 2019 13:45 #803527

  • old_kaw
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I have read that some folks buy the battery, then the "special" charger, then convert to the SH-775 regulator / rectifier and really sink some money into this setup. Personally, I don't think the stock system should hit more than 14.5 volts as long as it is functioning properly.. Check the voltage on the brown "sense" wire at the regulator if your bike has such an animal. I found my sense voltage to be operating ~2 volts low after i replaced my stator. After I replaced my stator, I installed a ice-cube relay to feed B+ voltage directly to my stock regulator, to stop the overcharging. I thought my battery was bad, but it turned out to be a shorted stator, and low sense voltage causing it to overcharge..



I still have the same gel-cell battery in it 2 years later.

1981 Kawasaki Kz1000K1
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Do you really need a special rectifier/regulator for Lithium Batteries? 09 May 2019 10:51 #803602

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Man, I wish my electronics looked as neat as that....

But I purchased a LiFePo (Lithium IRON) battery, not a Lithium-ION one. I've read some places that you don't need to update the regulator/rectifier for these, but I don't know why.

Is this true?
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Do you really need a special rectifier/regulator for Lithium Batteries? 09 May 2019 11:58 #803603

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It's a good question. Regardless of the type of regulator, they are all *voltage* regulators and simply try to maintain the system voltage and/or battery voltage at a specific average voltage. So as long as it is controlled by an accurate circuit, it shouldn't matter if it is mosfet, SCR, shunt or series-pass. The end goal is the same... a constant voltage.

From my understanding of lithium batteries, which is very limited, they don't like just getting a steady voltage applied. After they are fully charged they need the current to be lowered (which would be done by lowering the applied voltage). I don't think there is any voltage regulator for a bike that will do that.

A lead-acid battery is a brute and can handle a lot of abuse, so a simple voltage regulator is ok. The stator output is in pulses, so the regulation on commonly available regulators are imprecise. And the regulators don't really need to be very precise since most of that precision gets lost in the harness etc.

On old bikes, like most (but not all) KZ's, the most common cause of high voltage to the battery is bad wiring and contacts. When the switches and connectors and fuse holders get dirty, they drop voltage. This voltage drop causes the regulator to incorrectly assume the battery voltage is low, so the regulator increases the output to the battery. Thus the battery ends up up with too much voltage applied to it. This can happen with a perfectly good regulator. I would think this should be the main concern when using lithium batteries... making sure the regulator is getting an accurate battery voltage reading. This happens through the brown wire on KZ regulators that have a dedicated sense line. If I was to install a lithium battery, I personally would devise a system to ensure the regulator was getting direct battery voltage to regulate from.

Perhaps the caution is to get a regulator which uses its own output wire to the battery as the voltage sensing line. That way, the rest of the bike's wiring becomes irrelevant to the regulator. As mentioned, on KZ's the voltage sensing line on the regulator is the brown wire. If you get a 5 wire regulator (3-yellow, 1-red/white, 1-black) the sensing is done directly from the battery through the red/white wire.

Interestingly, Kawasaki, for a short time, had regulators that used the output wire as the sense line, then after a couple years they went back to having the dedicated sense line (brown wire). I should clarify... the brown wire on the main harness provides power to many things, but on the regulator it is used to sense the system voltage and assumes the battery voltage is the same or near the system voltage.

I think Kawasaki went back to the sense line (brown wire) regulators because back in the days of refillable batteries, they could handle a bit of over-voltage and the user would just have to top off the water periodically. It would also explain why the old mechanical regulators specify a pretty wide range of acceptable voltage including 15v. And by using the sense line, the regulator could compensate for those voltage drops and make sure the lights were bright and the ignition fired reliably, even if it meant the battery would need extra maintenance.... which may be hazardous on a lithium battery.
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Do you really need a special rectifier/regulator for Lithium Batteries? 10 May 2019 06:19 #803633

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So - basically - the LiFePo or Li-ion batteries are not really designed for the way the stator works on old bikes?

A guy I work with has installed a Li-ion battery in his Lotus Exige, which he's had for at least a decade, but hasn't had any problems with the battery. He is no expert in batteries or circuits, but he mentioned that someone once told him that it wasn't just the overcharging that can make the batteries fail, but also - like you mentioned - the pulses.

He didn't know, and I sure as hell don't know, what about the pulsing is the contributing factor to a failing Lithium battery. I wonder if it is the frequency, the voltage variance between discrete pulses, a combination of both, or something else entirely.
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Do you really need a special rectifier/regulator for Lithium Batteries? 10 May 2019 07:09 #803637

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dpivas7 wrote: So - basically - the LiFePo or Li-ion batteries are not really designed for the way the stator works on old bikes?



Lithium-ion... probably not. They don't even allow you to put those into the checked baggage on an airplane anymore. You have to carry them on so if they catch fire they can be put out. So maybe they are just hazardous period, not just when being charged.

I think LiFe-po claims to be fine for vehicles. Is your buddy sure he has a Li-ion battery and not a LiFe-po? The aftermath photos of Lithium battery fires in vehicles are pretty gruesome. That's the main reason I haven't tried them.

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Do you really need a special rectifier/regulator for Lithium Batteries? 10 May 2019 07:44 #803638

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dpivas7 wrote: So - basically - the LiFePo or Li-ion batteries are not really designed for the way the stator works on old bikes?

A guy I work with has installed a Li-ion battery in his Lotus Exige, which he's had for at least a decade, but hasn't had any problems with the battery. He is no expert in batteries or circuits, but he mentioned that someone once told him that it wasn't just the overcharging that can make the batteries fail, but also - like you mentioned - the pulses.

He didn't know, and I sure as hell don't know, what about the pulsing is the contributing factor to a failing Lithium battery. I wonder if it is the frequency, the voltage variance between discrete pulses, a combination of both, or something else entirely.


The pulses are no different than from an automotive alternator. Automotive alternators are also 3 phase and there are 6 rectifier diodes in an automotive alternator for the 3 phases. A single phase rectifier is called a full wave bridge. The same as in a motorcycle rectifier and almost every power supply known to man. TV's computers, etc. They also use filter capacitors to smooth out the ripple and make it suitable for solid state electronics. The battery should act as a filter capacitor that will smooth out the ripple in the AC voltage produced.




The main limiting factor would be the voltage exceeding the proper levels. The battery itself should be smoothing out any ripple. Like my friend stated, make sure the brown sense wire is at B+ voltage to prevent overcharging. (I hope you got that out of his post) This is the reason I pulled fused B+ from the start solenoid B+ post, and used the brown wire to trigger it. I don't have a schematic on the circuit, but those relays are used on a lot of mods, some use it to supply higher voltage to the ignition coils, some use them for lighting, I used it to keep from frying my stator again / stop overcharging.
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Do you really need a special rectifier/regulator for Lithium Batteries? 10 May 2019 07:48 #803639

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dpivas7 wrote: ... He didn't know, and I sure as hell don't know, what about the pulsing is the contributing factor to a failing Lithium battery. I wonder if it is the frequency, the voltage variance between discrete pulses, a combination of both, or something else entirely.


The system voltage, because it is pulsing DC, is actually a combination of a DC component and an AC component. The regulator is trying to control the average voltage, which is only the DC component, and the DC voltmeter is only reading the DC component The AC component is being neglected.

The AC component accounts for the ripple on the voltage signal, which can be significant.

If you have two voltages that read exactly the same on a DC voltmeter, but one is pure DC and the other has an AC component, and they are both connected to identical loads, the voltage with the AC component will deliver more power .

In our case, without doing the math, (which i'm willing to do later), I would assume the AC component only contributes the equivalent of 1 volt or less (maybe much less). But if it is 1 volt, then I guess it would be in the danger zone for lithium batteries.

But my speculation on lithium fires on vehicles is still with regulator failures (rather than design) or with wiring failures which cause the regulator to compensate with higher voltage.

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Do you really need a special rectifier/regulator for Lithium Batteries? 10 May 2019 08:11 #803640

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Also, a bad battery won't do much filtering, since it places no load on the ripple.

You can tell a totally bad battery by how many amps it places on a charger . If the load is small, the battery is either fully charged or totally gone.

You can also see how much ripple is on a circuit by switching your meter to AC while checking voltage. Lots of AC ripple = no ripple filtering. You could add a large filter cap, but is not necessary with a good battery.

That said, your buddy might have had a bad alternator diode's , loose connection, low sense voltage, etc.. the list is endless.. A lot of people are clueless to this info, including MOST dealer and small shop tech's. It does behoove you to make sure things are functioning properly no matter what battery you use.

I replaced this NAPA battery after only 1 year, when in hindsight, it was probably the stator and low sense voltage / erratic charging making the battery seem bad. I was overlooking the stator tests, and just ass-u-me the charging system was working properly since I had 13.5 volts @ ~ 2-3K rpm.

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Do you really need a special rectifier/regulator for Lithium Batteries? 12 May 2019 21:10 #803758

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Quality lithium batteries should have a battery management system circuit that would have some protection on the input.
Consider modern MOSFET reg/recs like the Shindegnen, these have fast switching and tend to put spikes into the loom.
A lead acid battery irons out much of this noise, but a lithium equivalent would probably require some sort of filtering, like a ferrite or a tranzorb.
Old style shunt reg/rec designs would probably be somewhat less noisy, especially transistor types.
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Do you really need a special rectifier/regulator for Lithium Batteries? 12 May 2019 22:30 #803761

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I came across the same problem when putting a lithium in my KZ. In normal operation the battery voltage was 14-14.5V - a little high for my liking, but OK. But when you turned the headlights on it would reach up to 15.5V at higher revs - just too much. Even when I cleaned the contacts it was still too high with the headlights on.

After cleaning all contacts and adding relays to the headlights, it's pretty stable now.
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Do you really need a special rectifier/regulator for Lithium Batteries? 13 May 2019 07:10 #803781

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Irish Yobbo wrote: I came across the same problem when putting a lithium in my KZ. In normal operation the battery voltage was 14-14.5V - a little high for my liking, but OK. But when you turned the headlights on it would reach up to 15.5V at higher revs - just too much. Even when I cleaned the contacts it was still too high with the headlights on.

After cleaning all contacts and adding relays to the headlights, it's pretty stable now.


I went through the same overcharging when I found my brown wire voltage low. (regulator sense voltage) I went through all of the bullet connectors, soldered all of the connections at my fuse block (it did need attention) and even my ignition switch looking for the high resistance. Even after spending a day going over my wiring harness, I did not find the problem.

I also managed to break a plastic tab off of my ignition switch when I disassembled it to clean the contacts. :-(



The cure is not to feed more power to the headlight, but to bring the sense voltage to proper levels. I added an ice-cube relay to bring the brown wire voltage to the proper levels. It has worked great ever since. Voltage levels are dead on. It starts and runs great every time since.

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Do you really need a special rectifier/regulator for Lithium Batteries? 13 May 2019 14:39 #803824

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old_kaw wrote: The cure is not to feed more power to the headlight, but to bring the sense voltage to proper levels.


Well really, that's what I was doing by adding relays to the headlights. The regulator sense wire runs off the accessories circuit, so with the headlights on the voltage would drop on that circuit, which would raise the charging voltage. By taking the load off the accessories circuit there was no voltage drop, so it wouldn't overcharge.
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Do you really need a special rectifier/regulator for Lithium Batteries? 13 May 2019 21:28 #803843

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Irish Yobbo wrote:

old_kaw wrote: The cure is not to feed more power to the headlight, but to bring the sense voltage to proper levels.


Well really, that's what I was doing by adding relays to the headlights. The regulator sense wire runs off the accessories circuit, so with the headlights on the voltage would drop on that circuit, which would raise the charging voltage. By taking the load off the accessories circuit there was no voltage drop, so it wouldn't overcharge.


I agree. By unloading the circuit the voltage should / would come up. I traced 3 accessory circuits through the ignition switch and my main concern was the charging system. There are indeed other switched accessories, and more voltage will certainly benefit them too, but since I have never experienced any problems with them. I used the brown sense wire to trigger the relay and fed it straight to the regulator.
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Do you really need a special rectifier/regulator for Lithium Batteries? 14 May 2019 08:32 #803860

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In my opinion, it would be better to unload the circuit than to use the relay for a direct path from the battery to the regulator.

The relay introduces another set of contacts and relays do fail. If the relay fails when used as the only path for the regulator sense line, everything is going to start to smoke. Also, vibration has been known to make the relay contacts chatter in some mounting applications. That will wreak havoc with the sense line and would be very hard to diagnose because it will look exactly like a failing regulator.

I think a third option would be to use the relay as a direct line, but also give it a fail-safe bypass so if the relay fails, the regulator will still get a feed from the brown line albeit through a diode. All it really entails is adding a single 1 amp diode (1N4001 etc.). The voltage will still run high if the relay fails open. The diode will add a .7v drop to the original drop on the sense line, but at least the regulator output shouldn't be 20 to 25v, which is the risk without the diode.

But again, I should point out to others reading this, on a stock electrical system these are still short-cut solutions masking the real problem of contacts or wiring age. The solutions work and as long as you know you don't have significant drop elsewhere it's fine. It's definitely easier than re-wiring the whole bike.

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Do you really need a special rectifier/regulator for Lithium Batteries? 14 May 2019 11:18 #803867

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Or does it stop charging if the switched wire voltage is removed? I have not tried this. I'll take my meter to the shed and can check this out easy enough later today.

I don't know if my voltage will come up if I unload the circuit, My headlight is always on and does not shut off. Frankly, this is working well and I am getting full B+ readings at the brown regulator wire. If it ain't broke, why "fix" it? :-)

The chances of the relay failing is not as high as my starter or battery failing at a gas station. A 1n4001 diode has the usual diode voltage drop across the semiconductor junction of .7v, which would make the sense voltage even lower than it was before adding the relay. Either way it gets smoked. The way I found this problem in the first place was because I smelled wiring starting to burn after I replaced my stator. I was getting ready to put my helmet on and smelled something, I pulled the side cover and felt the soft and warm wiring.

EDIT: I just hooked my digital meter to the battery then pulled the 10 amp fuse to my relay, and the battery voltage spiked immediately to 16-18 volts with no voltage on the brown wire. It probably would have gone higher while frying everything and shorting the stator in the process. In conclusion to my testing, the relay shunt diode would be good insurance. I have some and will go add one now. :-)



One of the most attractive things I find about the SH775 is the 5 wire design. The brown wire is not used to sense battery voltage. (BTW, my r/r is still the original OEM part)
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Do you really need a special rectifier/regulator for Lithium Batteries? 14 May 2019 13:39 #803872

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I just added in a 1N4002 diode between terminals 85 and 87 on the relay.


This was the cleanest way to add one, without cutting wires.


I did see some interesting results. With the fuse pulled, battery voltages ran close to 16 volts @~ 3-4K rpm. But, nowhere near the excessive levels I witnessed with the sense voltage nonexistent. I'm sure it would have gone higher given longer duration / higher RPM's, but I am not feeling quite that frisky today. This is feeding the brown wire voltage through the 1N4002 diode with the 10 amp fuse pulled. Essentially this is the sense voltage less another .7 volt because of the diode. (good thing I am in between projects)


These are the voltages I see pretty consistently with my relay "band aid" in circuit furnishing full battery voltage to the regulator.


Voltage does hold pretty steady and RPM doesn't seem to make much difference on output levels, but then again, there is a lot of difference between sustained highway revs, and standing in my shed.
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Do you really need a special rectifier/regulator for Lithium Batteries? 14 May 2019 14:39 #803876

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Great info guys, this is what these forums are really for.
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Do you really need a special rectifier/regulator for Lithium Batteries? 14 May 2019 15:08 #803878

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Thanks for confirming the sense line operation and the diode patch. :) That's pretty impressive just a few hours later to have real-world results.

Yes, the diode will add another .7v drop (maybe less since that circuit uses very little current), but it's better than a total drop to zero volts, so it may buy you some time and/or some miles to make it back home. (And of course the diode doesn't hurt anything. It is inactive when the relay is functioning properly.)

A voltmeter would be a good early warning system to have... or even just a warning LED. I have a few simple projects you can build to make warning lights. I tried to keep them to the bare minimum parts.
s3.amazonaws.com/gpzweb/VoltMonitor/GPZ1LEDvoltMonitor.html
s3.amazonaws.com/gpzweb/VoltMonitor/GPZ3LEDvoltMonitor.html

Just to confirm your wiring:
Pin 86 is ground.
Pin 85 is switched 12v (originally brown wire).
Pin 30 is connected to the battery with a 10 amp fuse.
Pin 87 is to the brown wire of the regulator.
The diode is to 85 and 87
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