Non-Lithuim Battery for a 77 KZ750B twin - Reg/Rec issue

Mine came with a lithium battery.
My dad has several 70's era hondas, and kawasaki and has shorai batteries in them. He never changed or upgraded the regulator rectifier for YEARS. Hasnt had any problems.
I was considering putting in a shorai on my 77 KZ750 Twin for weight savings, but I dont want any compatibility issues in re the reg/rec.

whats a good replacement agm or lead battery for a 77 KZ750B?

I know you're diagnosing issues with your bike, but using a lithium battery shouldn't cause any problems with your bike unless the battery itself is failing. All decent 12V lithium batteries have their own BMS that make the battery behave like an equivalent lead acid battery. The only real difference you should see is that the lithium will have a larger CCA rating but a lower capacity, neither of which will make any difference once the bike is running. Lithium batteries do tend to have a slightly higher resting voltage, which can cause problems with some electronics like oxford heated grips which are designed to turn off once the bike isn't running (with the higher resting voltage, they don't turn off because they think the bike is still running).

I have used a lithium battery in a few bikes, including a KZ250 and a KZ750 i4 without issue.

Chances are your battery is fine, so if you are getting a new battery to diagnose a problem, I'd suggest getting a cheap sealed battery, I don't know of any good reason to go for a battery that leaks in this day and age. I've been using an SSB RB9-B battery for 5 years in my KZ750 i4 and can't fault it (not sure that particular model will fit in a 750 twin).

wrote:

I don't know of any good reason to go for a battery that leaks in this day and age. 

I agree with this 100%.  I have had too many bikes with corroded battery boxes and swingarms.  All my vehicles have AGM batteries in them.

Do you happen to have a Batteries Plus near you?  If so I'd so see if they have an AGM battery in the right size.  They may not have the very best batteries, but they are fine.  And there are really only a few different battery manufacturers, and those manufacturers put lots of difference labels on the same battery (NAPA, Walmart, Sears, Auto Zone, etc), so it's hard to know if there are any real differences other than the sticker.

I would just find a battery that is sealed and is easy to buy.

Does this one look right?  It came up when I put in a '77 KZ750.
www.batteriesplus.com/productdetails/bat.../1977/cyla14ahlbsxta

I don't think its quite as simple as regulating voltage through a lithium specific regulator, or BMS, to work with a lithium battery correctly. Single phase charging systems (which the KZ750 twin uses) are supposedly not compatible with lithium batteries because of the large AC ripple and relatively low frequency they produce. 3 phase charging systems can have the same large voltage ripple but because they operate at higher frequency than single phase it doesn't matter as much.  KZ750-i4 uses 3 phase so it does not have this problem, not sure about the KZ250.

That being said you obviously were using a lithium battery for some time with single phase. Whatever frequency the twin operates at might be good enough to work with a lithium battery, However, I would suspect it probably will have a shortened life and there is a increased risk of "thermal runaway" - AKA fire under your ass you cannot put out. If you want to be sure what you're working with some multi-meters have frequency counters for AC systems.


earthxbatteries.com/engine-charging-syst...e-lithium-batteries/

"The ideal DC profile for charging a LiFePO4 battery is a AC ripple with a frequency > 5kHz and a AC ripple voltage magnitude < 10% (<1.5V). But in the real world,  frequency > 500Hz and AC ripple voltage magnitude <1.5V is acceptable."

"Are Vintage Single Phase (or Magneto type) Charging Systems Acceptable for Charging a Lithium Battery? The quick answer is no, and here is why. Take for example, the Rotax 503 engine (Provision 4; with 4 main mounting bolts on the gearbox) designed with points ignition and pull-starting. It uses a single coil (named magneto for permanent magnet construction) within the stator for auxiliary lighting power and battery charging. Since it is a single coil, it will produce one AC waveform per revolution of the engine (see Figure 6 below for an installation example of this type coil)The Rotax engine also has a regulator-rectifier has shown in Figure 7 below (part 866-080).The regulated/ rectifier voltage output of this particular Rotax system is shown in Figure 8 below. Note, the DC output has a low frequency (two pulses per engine revolution, 33Hz at 2000RPM) and high amplitude ripple (full charging output 14.5V).To compensate for the poor charging voltage Rotax recommended a large 16Ah lead acid battery to act as a buffer, and in some cases a capacitor to smooth the DC voltage. This DC charging voltage while not ideal for a large lead acid battery was acceptable.This type charging voltage is not acceptable for a lithium battery for its large AC ripple at low frequency (< 5kHz and >1.4V) will damage the cells due to heating and plating (see the above section for lithium battery charging requirements)."

I spoke to both Shorai tech dept and Rick's Motorsports which makes aftermarket lithium battery compatible updated reg/recs.

1. Shorai said their batteries are not recommended in old bikes (esp my KZ 750 Twin) due to the original reg/rec potentially overcharging the battery, or something like that. He said, for me to have had it in the bike in the inappropriate configuration for 2 years, without a fire, is a bit of luck, and that some ppl have experienced battery fires because they didnt update the reg/rec

2. Rick's Motorsport said the same thing about the absolute NEED to update the reg/reg to a lithium compatible one when running a lithium battery. Some ppl are lucky and run them for years without a problem. On the other hand, some have had their bikes burn to the ground.

So, instead of spending $160 on a shorai batttery and another $140 on a lithium compatible reg/rec, Im spending $68 on an electrosport reg/rec and $100 on a AGM battery from Autozone. In my view I've saved $140. I dont need a $300 battery set up in a 77 KZ750 whose worth in very good condition is $1500

Make perfect sense, I am only using lithium in my 1000 because of real estate constraints (much smaller battery) and I have the correct RR and it's a three phase charging system

I got this "el cheapo," as my mom would say, battery. Im sure it will be fine. Anything to ease my mind about running the set up I am currently running which could lead to the lith battery exploding

Ive learned that many AGM batteries are the same, just branded differently:

www.batterymart.com/p-ytx14ahl-bs-agm-ma...ce-free-battery.html