Alan K

Acquiring knowledge and learning is usually a good start. 😉

As for not buying crap ever, this would put stores like Wollie’s World and many online outfits that are middle men for junk from China out of business, which isn’t necessarily a bad thing. 😉

Doc_Wui

Many of the chinese import ebikes do use commonly available batteries, even if most have moved to designs that integrate batteries in the frame.

In the DIY world, you're going to be choosing what kind of a battery wart to mount on the downtube, as you'll be using a regular bike frame. I think most of the Hailong cases have flimsy mounts, coming standard with only two holes to hold an 8-10 lb battery on water bottle screw holes. The older Dolphin is rarely used these days, but is more rugged design. A conscientious builder will augment the battery with extra attach points, and almost never mount it upside down like what is often seen with full suspension bikes.

2old

This is a Blackburn rack that has two straps to secure the battery, and used off road on the FS bike. I placed a piece of Styrofoam between the battery and the cage in order to insulate it from shock. All of the batteries on my DIY bikes have XT-90 battery and XT-60 charger connectors. Pretty simple solution.

ScottCommutes

To be "safe" in the traditional sense, treat these batteries like the gasoline they replace. Everyone knows not to store a gallon of gasoline (even in a proper can) in their bedroom.

polyrhythmia

I do mount my battery upside down underneath on my T50 Cruzbike, but I also made a support so that the mount is not carrying the load. Having the battery rack mounted made handling squirrelly.

VegasTriker

It is funny reading ScottCommutes comment. I received a call from my brother two days ago letting me know that he had a house fire but both he and his wife were OK. His wife owns a Jeep with starting problems so she carries on of those jump-start contraptions. It must have a pretty substantial Li-ion battery. She was charging it in a spare bedroom when it started to burn. From what he told me it produced a lot of noxious smoke and soot. He unplugged it and covered it with a fire resistant blanket while the fire department was on their way. I would never have charged anything with a substantial Li-ion battery inside the house or garage.

2old

VT, excellent point; I charge my battery in the middle of my yard on stone blocks (even though I'm not really worried about them).

tds101 

I hope you have those stone blocks insured. You know, just in case...

mpetry912 

the extreme low end bikes may only have a very rudimentary battery management system.

one good rule of thumb is to keep an eye (or finger) on the temperature of both the battery and the charger.

and pull the plug if either get too warm

another is to not charge the battery to 100% - pull the plug at 80% or so.

I have a Specialized Vado 5 with a 600w battery and have had zero issues with battery temps

/markp

2old

tds, ha ha; while maybe somewhat fire resistant, they were priced very reasonably (plus my daughter's fiancee installed them.

dayco

This is what I've gleaned...

A more expensive name-brand battery/charger UL-tested is the safest choice. The battery and charger must be compatible and have internal fuses. There must be a battery maintenance system (BMS) that controls/checks the charging and temperature. You should begin charging the battery when it's cool and is down to 20% capacity and should end the charge at about 80% capacity for 5 to 10 charging cycles. The BMS will have a low voltage/high voltage cutoff. After 5-10 charging cycles the battery should be charged to 100% to allow the BMS to balance/equalize the cell rows. If the voltage/current between the cell rows can not be equalized the BMS should disconnect the battery from use.

A properly featured BMS should control the maximum charge and the rate of charge. It should also sense battery temperature. (I may also want to do an occasional touch-test) It is recommended to unplug or use an independent wall timer to disconnect the charger and battery after a fixed period of charging time. Charge only in a fire resistant location while monitoring. Avoid charging in hot or cold temperature extremes.

I will make my selection from batteries and/or sellers that yield this information. Buying or doing anything less will mean a greater battery/charger fire risk.

Doc_Wui

All of those Hailongs that have a space in the cradle to hold a controller only have two locking tabs to lock the battery down. They shouldn't be used upside down with half the weight of the battery unsupported. You want to use the type on the bottom, that has lock tabs along the full length.

2old

I've never needed to install a battery upside down, but wouldn't hesitate to if necessary since I always secure the battery with one or two "toe straps" or Velcro straps in addition to the normal installation system. This prevents any extra movement of the battery.

polyrhythmia

I have the bottom style mount, though there are only three M5 screws to mount it under the T50 Cruzbike. I still don't trust the mount by itself. The support is made from aluminum. As far as storing battery over winter, I would think that it's better to be in a cool place, but not close to freezing.

2old

As warm (within reason) as possible. Also, don't charge if the battery is below 50 degrees F.

tds101 

I see...

polyrhythmia

Upgraded the Bafang display so now I know what the battery is really doing as far as charge. Most frustrating are the really tiny screws and nuts. Then I should be able to gauge the charge by the voltage shown by the charger, 50 volts being about 50% charged, for a 48 volt system.

Doc_Wui

Those jump starters are not that big, They contain pouch cells. I bought three of them from Walmart on clearance for around $25 each in 2015. Ran them in series to power my 36V bike. Cheap power back in those days. I was always afraid of them, so I would charge them outside on the driveway. One day, it rained and the water ruined them. Better off without them.

tds101 

I had one of those battery boosters almost set my house on fire a few years ago. That's why I use a capacitor-based battery booster for my car. It works amazingly well.

jon c. 

I charge 40v tool batteries indoors without a second thought. Are these batteries safer or am I just insufficiently cautious?

2old

IMO, those tool batteries, as well as batteries from big bicycle OEM's (Trek, Specialized, Giant, etc) can be charged inside safely. A problem with them may have occurred, but I've never heard of one.

CrimsonEclipse

The tool batteries aren't as energy dense and less likely to cascade fail.
They still happen, but simply won't make the news

tds101 

I work for the MTA in NYC, and we charge those types of batteries all the time completely without incident. It's these other, unregulated ones that are the issue. I don't know if I've really ever seen these catch fire TBH. The car jumpers, they overheat. Mine was actually producing smoke.

2old

I worked in a friend's large machine shop for a few years and tool batteries which weren't being used were charged inside the shop constantly. Probably there were at least 10 batteries on the chargers and they stayed there day and night until needed. The BMS (battery management system) regulated the voltage.

Duragrouch

In one of my past lives, my work involved EOD (bomb disposal) robots. Came time to modernize and upgrade the power densities, the lead-acid batteries were replaced with Nickle Metal Hydride; Lithium Ion batteries had long been on the market and offered even greater power density, but there was hesitancy to make a potential bomb from a bomb-disposal robot.

I do not yet own an electric bike, but am happy for the Li-Ion cells, their high power density, their range. But given the size of those batteries, I would never charge them on the bike, I would obtain a STEEL (not aluminum) charging box that could totally contain any fire, explosion, and excessive heat, and always charge the battery in the box, with the box sitting on something fireproof, like bricks or a concrete floor. A bit more hassle, but a lot more safe. It would be nice if the battery were internal to the bike if the bike itself could contain a fire, but a frame from aluminum or carbon-reinforced-plastic, no. This is why Boeing had to replace the box holding lithium emergency batteries on the 787, from aluminum, to steel or titanium (I forget which), because aluminum did not adequately contain two separate fires.

My phone and keyboard use lithium batteries. Despite their much smaller size, I never leave anything on a charger unattended.