BMW Owners News
Motorcycle Test Kitchen

Motobatt hybrid AGM-lithium battery

Anyone who has owned motorcycles long enough knows that sinking feeling when you’re all set to ride but discover you’re short on electrons. I recently had just such an experience with my R 1250 RS. It had been a bit hard to start during a cold snap last month, but I’d chalked that up to the expectable difficulty any battery might have when temps are extra-low and crankcase oil viscosity is extra-high, especially on a long-stroke, high-compression, large-displacement twin. Turns out it was an omen. A mere two weeks after my last ride, on which there was no hint of trouble, I wheeled my bike out of the garage into the warm-ish sunshine, thumbed the starter, and got a single, brief, “Rwrr.” All done. The dash voltmeter read around 11 volts (V), clearly not enough to achieve the desired effect. This bike has sat dormant longer without my Battery Tender and never had an issue. I’m not proud of such absent-minded neglect; my point is something was definitely wrong.

Everything included with a new Motobatt hybrid battery.

With my riding buddy waiting, I was able to salvage the day with a tiny jumper pack I’ve kept handy, but never had to use before. Barely as large as the alligator clamps that connect it to the battery (and remote positive terminal on my bike), this mighty little device threw plenty of amperage at the big boxer’s starter, kicking it over instantaneously. Although I never needed this augmentation again during the day’s riding, I knew my battery—now probably going on four years old—had become untrustworthy. Time for a replacement.

I researched the options, again weighing the cost/benefit and strength/weakness arguments for sticking with a conventional absorbed glass mat (AGM) lead-acid model like the OEM unit, or switching to a lithium version as I’ve done with all my other bikes since 2018. Lithium batteries typically have a large cold cranking amp (CCA) advantage and are much lighter, smaller, and more expensive than their AGM counterparts; lithium batteries also self-discharge much more slowly, allowing for vastly more owner neglect without punishing consequences. On the other hand, AGM (and old-school unsealed or newer-school gel) lead-acid batteries generally have the upper hand in terms of amp-hours (Ah), even when the lithium counterpart’s manufacturer may claim a similar “lead-acid equivalent” (PbEq) Ah rating. (Such measurements for each battery type involve different parameters and can’t be directly compared.) Superior Ah translates into greater resilience under sustained load (e.g., parasitic drain from electronics when the motor is off, or a net drain when the motor is on due to accessory needs exceeding alternator capacity) and/or sub-optimal charging during operation, as may occur during frequent stopping/restarting and low-speed running in urban traffic. You might think of lithium batteries as explosive sprinters and lead-acid batteries as marathon runners.

Speaking of explosive, you may have heard or read horror stories of lithium batteries bursting into flame. Please understand such accounts usually involve lithium-ion batteries, whereas most lithium powersports batteries are more stable lithium-iron (actually lithium iron sulphate, or LiFePO4); it’s easy to miss this distinction when there’s just a single letter difference. Lithium-iron batteries are far more stable and aren’t normally vulnerable to thermal runaway (catastrophic overheating) during rapid charging, discharging, or short-circuits. Though heavier and possessing less energy density than their Lithium-ion cousins, lithium-iron batteries are cheaper to produce, more tolerant of vibration and high heat, operate consistently through many more charging cycles, and aren’t nearly as toxic or environmentally hazardous. Assume my references to lithium batteries here are all lithium-iron.

The Motobatt hybrid – with spacer in place – compared to the stock BMW battery.

In addition to the headline contrasts between lithium and lead-acid batteries already mentioned, lithium variants can require a “warm-up” period in very cold weather. A motorcyclist may need to turn on their bike’s headlight for 30 seconds before hitting the starter button. This gets some current flowing through the battery and allows it to then perform normally; otherwise, it may seem alarmingly weak. Lithium batteries can also have the disadvantage of requiring a dedicated charger. Although they obviously receive conventional charging via the motorcycle’s electrical system during operation, certain aspects of chargers designed for lead-acid batteries are not ideal for lithium. Without getting into all the details here (Dammit, Jim! I’m a psychologist, not an electrical engineer!), lithium batteries hold a higher resting charge (13.3-13.4V as opposed to 12.6-12.7V), don’t require—and can be damaged by—a float or trickle charge because of their extremely low self-discharge rate, and could suffer serious harm from a desulfation or equalization cycle in the charging process (which may be automatically included in a standard charger’s routine). Also, the algorithm used by a lithium charger to modulate current is optimized for rapid and complete charging of a lithium battery without overstepping strict maximum thresholds; use of a standard charger on a lithium battery is apt to be less efficient, may not result in 100% charge, and/or may extend charging beyond safe limits. Modern lithium batteries typically have built-in circuitry to protect against overcharging and excessive discharging, maintain cell balance, and avoid overheating. This helps prevent the worst outcomes of using a conventional charger on a lithium battery, but doing so may still involve some risk, if only in terms of sub-optimal battery performance. There are chargers that can sense, or be set to accommodate, both battery types, but what I’m about reveal makes all this moot.

Instead of deciding between AGM and lithium, I chose Motobatt’s hybrid in hopes of getting the best of both worlds. (While the name may be unfamiliar, Motobatt is a subsidiary of well-known Yuasa; Motobatt AGM batteries come as OEM equipment in some European brands and have performed well in other motorcycles I’ve owned.) I have not measured and independently confirmed the amperage-related specifications below, but here are the numbers for the Motobatt hybrid model appropriate for my RS and most other modern large BMWs, compared to those for a conventional AGM unit and my old favorite lithium competitor.

Spec Yuasa YTX14-BS Motobatt MHTX16 Antigravity ATX-12 lithium
Cranking amps (CA) 250 438/350 360
Cold cranking amps (CCA) 200 350/280 288
Amp-hours (Ah) 12 8.5 (16 PbEq) 6 (12 PbEq)
Weight (lbs/kilo) 10.1 (4.6) 6 (2.7) 2.7 (1.2)
Dimensions (in/mm) 6×3.5×5.8 (152x127x147) 5.9×3.4×5.1 (150x86x130) 5.9×3.4×5.2 (150x86x132)
Cost (USD) $99* $212 $225
Warranty 1 yr 3 yrs 3 yrs

*This is about half the price of the stock BMW part, which appears to have lower cranking amperage.

Note: Cranking amps are measured at 0 degrees Celsius (32 degrees Fahrenheit); cold cranking amps are typically measured at -18 degrees Celsius (0 degrees Fahrenheit), although the BMW battery’s case shows it as measured at -10 degrees Celsius for some unknown reason. The standard conversion involves dividing CA by 1.25 to get CCA; hence the figures shown start with the CA or CCA value from each manufacturer (only one or the other may be provided), with the remaining value calculated using this formula. Different charts on Motobatt’s website show 350 as CA in one place (and on the battery top) and CCA in another and I was unable to get clarification. I’ve shown the calculations both ways above. Also, I’ve not considered Antigravity’s Re-Start feature in this comparison, though I did cover it in my previous review of this battery (ON issue: 2/21; web post: 1/17/21).

You can see the hybrid falls in between the AGM and lithium batteries on some counts, and may be superior on others. It does not require a bespoke lithium charger, yet it’s touted as charging faster than a lead-acid equivalent. Self-discharge rate supposedly approximates that of a lithium battery, with starting performance stable across all weather conditions. Its life cycle duration is claimed to exceed that of either alternative battery type.

In addition to these factors, here are several other things to consider. The Motobatt hybrid features their M-Flex terminals, which utilize two pairs of copper extensions to locate the connections on either side of the battery, allowing it to replace a longer list of other models and thereby reduce stocking costs and, presumably, retail pricing. If you need the positive and negative in reverse orientation, just use the longer pair of extensions and turn the battery around. Either pair gets screwed onto the same permanent mounts on the ABS case’s short sides. The terminals also allow for vertical or horizontal connections, using a threaded block positioned within the extension in either orientation. (To be fair, the Antigravity battery achieves the same versatility by simply positioning dual-orientation terminals at all four corners.) Like other lithium batteries, the hybrid comes with adhesive-backed foam spacers (two at 15mm, each) to take up the vacant space in a battery box resulting from it being smaller than the OEM part.

After getting excited about buying Motobatt’s hybrid, I was disappointed to find the one I needed out of stock at their US website. Impact Battery in Kentucky had it and shipped it promptly for free.