Two bottle batteries in parallel

It seems the bigger a battery, the higher its max continuous discharge rate is.

Bottle batteries such as:

http://www.bmsbattery.com/36v/571-bottle-ebike-battery.html

are nice since they can fit within a normal frame relatively easily, but they still have a low max continuous discharge rate, around 10A (and max non-continuous at 20A) according to the seller.

My question is:

1. Is it possible to connect in parallel two bottle batteries, having then a 36V 20Ah?
2. If it is possible, would the max continuous discharge rate be immediately higher? If so, how much approximately?

Thanks.

Yes it is, max current will be doubled!

Pretty much true. Each bms will have a limit, but your draw will split between the two bms's.

So two bottle batteries paralell should be able to provide for a 20 amps controller easily. But just because 40 amps briefly is ok on paper, I would not try to run a 40 amps controller. The batteries will last better if they get half the rated discharge rate continuous, and perhaps 1.5x that rate burst. So maybe a 30 amps controller at the very most.

the current that comes from each pack is the reciprocal of the internal resistance of each pack. if one pack has higher internal resistance than the other it will not lose as much charge so the other pack will have to supply more of the current. it will be equal only when the internal resistance of each pack is identical.

Arbol said:

It seems the bigger a battery, the higher its max continuous discharge rate is.

Bottle batteries such as:

http://www.bmsbattery.com/36v/571-bottle-ebike-battery.html

are nice since they can fit within a normal frame relatively easily, but they still have a low max continuous discharge rate, around 10A (and max non-continuous at 20A) according to the seller.

My question is:

1. Is it possible to connect in parallel two bottle batteries, having then a 36V 20Ah?
2. If it is possible, would the max continuous discharge rate be immediately higher? If so, how much approximately?

Thanks.

Click to expand...

Thats an awesome idea really, those bottle batteries are great for triangle frame fits but are normally lower voltage. Having two would crush that problem.
I blew the fuse (20amp) on my 36volt BMSbattery going up a giant hill on my 12mosfet KU123 controller. I figure the fuses are slow blow because it took me a about 1/3 up the hill before it blew the fuse. I put some 20amp fast blow fuse in and it works OK as long as I don't take off quickly which is where most of the amps are drawn.. on take off. If I flat chat it from 0kph the fuse just blows.

On paper yes close to double but you lose a % and is best not to use to there limit. It's like driving your car with the gas peddle on the floor.

As always, I make many assumptions.

Yeah, it won't be equal unless both batteries are close to identical. Both new, both the same size, same chemistry, and even the wire would have to be the same size and length. One wonky plug, and all the power would start coming from just one battery, and it would then hammer that single battery to death, or pop a fuse, or trip it's bms.

But assuming again that you don't have some kind of problem with the connections, paralleling two packs can work well. Each pack bears half the load, and the end effect is similar to having a larger single battery.

What's the shipping price to the USA for one of these? BMS battery is famous for high shipping charges if I recall from other ES members posts...