I got an email last week about replacement costs for a Bosch Battery direct through Magura USA who is the US center for Bosch ebike parts and repairs. I’m not a big fan of the Bosch drive system (you can see why about 1/2 down the post here) but I thought I would do a financial comparison between the Bosch battery system and some of the batteries I’ve used over the past year.
There are a few Bosch drivetrain fatbikes that will be available for sale this year. The Haibike FatSix and Felt Outfitter and Felt LEBOWSKe Fatbikes. It seems like Bosch is poised to take over the lion’s share of the high-end factory middrive ebikes in the US in the years to come. How does the Bosch battery compare with cost/watt hr compared to other batteries I’ve used in the past year? The following chart does not always include shipping costs which can be substantial for Lithium batteries.
Bosch Li-Ion11Ah 36v $956.90/400Wh = $2.39/Wh / ~700 claimed cycles = $.0034 $/Wh/cycles 5.5lbs
LifePo4 Prismatic Pouch Cells 48v 20ah 30Amps cont pack bought on ebay from imotorbattery $490(shipped)/960Wh = $.51 Wh / ~1000 cycles (1500+ claimed) = $.00051 $/Wh/cycles (Included charger) 16.768 lbs
LifePo4 Headway 48v 16S 12ah pack bought from BMS battery with 50Amp cont $381.29(no shipping or charger)/576Wh = $.384Wh /~1500 (2000 claimed) cycles = $.00025 $/Wh/cycles 16.6 lbs (The website claims the battery is 3.38 lbs lighter but it’s a damned lie and they won’t update their specs after repeated requests)
Li-Ion Giant Twist Replacement battery 36v 10Ah Li-Ion NiCoMn from BMS battery (with Bms 15Amp Cont and charger) $189 (no shipping) / 360 Wh = $.52/Wh / ~700 cycles (800 claimed) = $.00075 $/Wh/cycles 5.375 lbs This battery is an upgrade for the Giant Twist and will not work easily on other bikes.
Lipo 8Ah ZippyMax battery 12S 30C 48v 8Ah from Hobbyking (no BMS) $170.94 (no shipping or charger)/384Wh = $0.445 / ~300 cycles (if you don’t abuse them) = $.00148 $/Wh/cycles 5.2lbs
LifePo4 Turnigy 4.5Ah 30C S18P2 54v from Hobbyking(no BMS) $212.94 (no shipping or charger)/243 Wh = $.86/Wg / ~300 cycles (if you don’t abuse them) = $.0029 $/Wh/cycles 5.94 lbs
Looking over these numbers the thing I keep going back to is the old saying around the bike shop. Durability, weight and price. Pick two. The most durable cells I’ve used, the 16S headways are also by far the heaviest. When you break down their cost over time they are the clear cheap winner, but 16lbs for a 12Ah pack is pretty hefty, even for one that can put out 50 Amps continuous. The lightest cells are the Zippy Flightmax, although they are by far the most persnickety of the bunch. If you overcharge them, charge them too fast or over discharge them you won’t get anywhere near 300 cycles out of them. For Lipos or LifePo4 batteries without a BMS you need a Cycle Analyst or a low voltage alarm. That being said the Lifepo4 and Lipos have a nasty tenancy to swell up and die when you pull too high of a C rate off them or keep them stored for a long time fully charged.
The Bosch battery system has a built in controller that will only talk to a Bosch drive system. You will never be able to use their battery on any other ebike or motor. If the battery temp drops under 32 degrees of over 140 degrees F it will automagically shut off to protect the cells.
What do I recommend? I’ve been really happy with the headway cells for 50+ amp draw even though they are very old battery technology and are very, very heavy. They can be recharged faster than 2-3 Amps without damaging the cells and I consistently seem to get 12Ah out of the pack. The pouch cells are the pack I use 90% of the time and have given me more trouble than the Headways. One of the pouches has dropped down in voltage for an unknown reason a couple of months back, you can see the article on repairing it here. It could be a bad mosfet on the BMS leaking voltage or it could be a bad cell, but that pack seems to need to be left on the charger now if I want to get a full charge out of it. Leaving a pack on the charger 24/7 can decrease it’s pack life and generally is not advised. Hobbyking Lipo and Lifepo4 are a pain to deal with and when compared with the other battery technologies and is not that great of a deal. That being said it is the lightest of any battery tech so if weight is more important to you than cost or charge cycles it is an option.
The packs that excite me the most are the triangle packs from em3ev. Although I can’t afford one right now, my ‘dream pack’ is a 29E large triangle pack. I’ll do the calculations here just to compare above.
Em3ev triangle pack INR18650-29E 40 Amps Cont – 24.8Ah – 50v $964 (Charger but no shipping)/1240Wh = $.777/Wh / 700 claimed (possibly doubled if charged to only 80%) = $.00111 $/Wh/cycles 15lbs
The size/form factor/power of the Em3ev Triangle pack seems to me to be the best combination of price and performance. The built-in ability to charge your packs to 80%/90%/100% is a feature that should be integrated into every charger so ebike users can balance pack charging based on their needs to drastically increase their battery life. It’s proven that charging to only 80% can almost double your pack life. Another option is the Cycle Satiator from Grin if you want to charge almost any pack in the world to almost any percentage of capacity. It can be bought for $295 here. Considering the costs of many battery packs it could quickly pay for itself by extending your packs lives.