LiFePO4 battery packs for Bafang mid-mount?

[Jdege]

I'm planning on retiring to a sailboat.

I've been musing about putting together a folding bike with electric assist, for transportation around whatever town I'm moored at.

I haven't settled in details, yet, but front-the now would be the Montague Paratrooper or Navigator, with a Bafang 750W mid-mount motor. (I could go with the M-E1, but I want something I build myself so I have something I can repair myself.)

The problem with the designs I've seen is that they use Li-Ion battery packs, and sailors don't trust Lithium other than Lithium Iron Phosphate. LiFePO4 isn't quite as energy dense as the alternatives, but it allows for more charge cycles and it can't spontaneously combust.

Having your car spontaneously catch fire is a problem. Standing on the side of the road watching it burn is unpleasant. But if your boat catches fire you don't have the option of getting out to watch it burn.

There's no reason I can see why a Bafang wouldn't work with a properly-sized LiFePO4 battery pack. Volts are volts, amps are amps. But I've not seen any 48V LiFePO4 packs suitable for mounting to a bike frame.

Are there any?

[AZguy]

People have used them and a bafang mid you can adjust low-voltage cutoff will support them just fine

Very few folks use them for the reasons you mention, they are much heavier and larger for the same energy

I'd think the best arrangement would be 16s (16 groups of cells in series) for a maximum voltage of 58.4V and since they are often sold as 12V lead-acid replacements in a 4s configuration 4 of those in series should also work well

There was a fellow that went for them recently on a front hub trike where it had a lot of space and weight wasn't a concern - I think he was more interested in lower cost than anything however... My recollection is he did the 4x 12V lead-acid replacements - it was pretty large and heavy though, much more so than the conventional electric bike batteries so a lot will come down to the amount of energy (range) you are going to comfortable with and whether you can source what's appropriate once you've determined that...

[Jdege]

I'm wondering if using Li-Ion is such a risk.

I mean, yes I can see the worry about a house bank on a boat catching fire, but a portable battery? Can't you just throw it overboard?

[AZguy]

Hard to say

Risk management is generally a "personal" thing - everyone has their own sensitivites

A decent electric bike battery from a reputable manufacturer wouldn't stop me on a boat but that's my own thing... I'd still be very sensitive to them - boat fires on open water is not a happy thing at all...

[Jdege]

Hard to say

Risk management is generally a "personal" thing - everyone has their own sensitivites

A decent electric bike battery from a reputable manufacturer wouldn't stop me on a boat but that's my own thing... I'd still be very sensitive to them - boat fires on open water is not a happy thing at all...

I'm going to have a number of small Li-Ion batteries on the boat, phones, tablets, laptops, etc., regardless.

And I'm going to have large banks for house and propulsion.

If a phone catches fire I can toss it.

The propulsion batteries will be solidly mounted below decks and weigh two hundred pounds each. I'm not going to be able to toss them.

The bike will be larger even then the laptop battery, but it's still something I can toss, so Li-Ion should be acceptable.

The one precaution I might take is to remove the battery from the bike, when I'm packing the bike away into an inaccessible corner for a long passage, and keep the battery someplace I can keep an eye on it.

[AZguy]

I have far more batteries than bikes and so most aren't on bikes and unless I'm riding the bike within a day or two it's not likely to be kept with a battery mounted

OTOH I know folks that likely have never removed their battery from the bike - everybody's different!

[stts]

I just order a bbs02 48volt kit. And i think I will do the LifePo4 setup. It all bolts together. All meaning only 16 1.5 pound batteries. So bad cells can be unbolted and replaced. They were $11 per 25Ah cell. They went up to $17 per cell. A youtuber ran a pack like that for 38 miles with very little peddling. They are twice as big but much safer. People cant get them to burn from faulty charging. It will fit on a rear bike rack. Ill make a custom rack with angle alluminum thats way more sturdy. And I will steel band heavy steel pieces to the battery so I can lock it to the rack. They say you have to band it together anyway to help keep the cells from swelling. I have banding tools at work. Then I can get giant heat shrink that fits the giant battery. Thats what the youtuber did on his LifePo4 build. Seems like a great idea if you want insurance from your stuff catching fire. I just wish the prices didn't jump up. This stuff is supposed to be getting cheaper every week. The Bafang equipment is switching to propriatary canbuss that will prevent making your own batteries. I suspect the BBS line will be discontinued as soon as they can sell out their stock.