Batteries in a series and parallel question

Pokey4207

10 µW
Joined
Dec 10, 2017
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5
I have 4 12 volt sla batteries however two of them are 9ah and the other two are 10ah. What I want to know is should I connect the two 9ah batteries in a series and the two 10ah batteries in a series and then parallel the two so I have a 24 volt 19ah battery or any other way anyone can suggest?
 
That's the best way to do it, though I gotta say that with SLA you're really only getting about half of whatever rating they have, at best, when used at higher currents (like on EVs of any kind).

So by parallelling the two sets, you'll probably get about the actual amount that one set contains.
 
So are you saying with 2 12 volt 10ah batteries I basically have a 24 volt 5ah pack and by adding the 2 batteries it's only roughly a 10ah 24 volt setup?
 
That's right. Discount half the rated capacity of SLA batteries if you want them to last for more than a handful of charges.

Those batteries suck. Trust all of us who've been there and done that.
 
I'm just kinda stuck with what I have at the moment I'm definitely going to upgrade away from sla batteries I just need to be able to travel more than the 3 miles I was getting out of the two batteries I was using. I have noticed that as far as sla batteries are concerned if that is all you can afford or already have then 12 ah batteries seem to be a better fit as far as range
 
My first e-bike used two 12Ah SLA batteries with a 400W rated can motor, and it was very limited in its capabilities. On my second e-bike, I used three 17Ah to 22Ah SLA batteries with a 1000W rated hub motor. It was better, but very heavy, and still not a great performer.

I think I'd have enjoyed those bikes much better for much longer if there had been frame mounted lithium bottle batteries available at the time. As it was, I set e-bikes aside for many years once I moved to a place with less daunting hills.
 
You need to bite the bullet and spend good money on a good battery. Lithium Ion is light years better then Lead Acid for our hobby. I am a frugal guy myself, but I dont mind spending more money where it counts.
 
If you are running now on 24v, then stick with that, and make up the 19 ah 24v battery.

Series first, or parallel first won't matter, so long as the wiring is easy for you. i'd be inclined to make two 24v batteries by series first, then run a wire from each to the controller, with a Y connection ( paralell) just before you connect to the controller. Carry one battery on one side pannier, the other on the other side.

With that big a battery, 19 ah, you should be able to discharge a bit more than half, say about 12 ah. The larger a lead battery gets, the less it suffers from that use only 50% effect. You still want to stop at about 75% though, to get a year out of the batteries.

Better than run each battery separate, at 9-10 ah, they are suffering like a dog. Next spring, get your lithium. 10 ah big enough for lithium, but 15-20 ah better!
 
I'm definitely not going to be using sla batteries much longer it's really only out of necessity currently and I now know what type of planning I need as I move towards building myself a bike that fits my needs because the current market doesn't offer any bikes off the shelf so to speak (at anywhere near affordable anyways) that fits my personal need.
 
Nobody offers anything that fits mine either, hence the SB Cruiser trike (and CrazyBike2 before it). There's a bunch of members here that have done completely custom stuff, and lots of members that have customized "regular" bike setups to better suit their needs.

So lots of examples to look at to help you decide what to do.

What I'd recommend first is to define your needs, and go to this thread
https://endless-sphere.com/forums/viewtopic.php?f=3&t=66302
and then copy the first post's questions, paste those into a reply here, along with your answers. Plus any other info you think would be relevant. That will help us help you figure out what you can get to do what you need on the best budget with the best reliability.
 
When I worked the chat at E-Bikekit, the first questions I asked people was what were their needs.

Speed, distance, hills, and the total weight they need to carry. Themselves, and any cargo.

Like AW, my needs were not easily filled by commercial bikes then, but lately they could be. I need to carry some stuff, but not as much as AW. Right now, a new longtail with a mid drive would do it for me, but I'd still want more range than 400-800 watthours can take me. But when I built my longtail, none were built to carry as much battery as I wanted. This one could carry 2000 wh without even using the panniers.
Finished cargo mixte..jpg
 
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