sla battery pack

[mygrumpy]

hi all.i want to make a battery pack using 6 12v 15amp sla batteries,which will give me 36v 45amps,will i need a Thermister,if so where do i wire it on the pack, also where do i wire the fuse,what size wire.will a 36v 1.8 amps charger charge this pack alright,thanks for ay help given. john

 

[safe]

I've got a bike with three 12 Volt 38 Ah batteries wired in series making a total of 36 Volts. The batteries alone weigh 86 lbs and the bike was designed from the ground up to handle the stress that this much weight causes. I've got thick 24" wheels with 3" tires. All I use is a fuse and nothing else. SLA is extremely durable and safe to use, but it weighs a lot.

Are you welding a frame from scratch or are you using a motorcycle frame as a base? A regular bicycle frame will NOT handle the weight safely...

 

[fechter]

If you want to make a 36v pack from six 12v batteries, the best way is to wire pairs of batteries in parallel, then put the three pairs in series. If each battery is 15Ah, the pack will be 30Ah (not 45).

Your 1.8A charger will work, but take a long time for a full charge.
Three separate 12v chargers (one for each pair) will keep the pack balanced better.

SLA batteries do not usually use a thermistor.

You do need a fuse, and it's best to put that directly to one of the battery terminals. I doesn't really matter which one. The fuse could go in the middle of the pack too. The fuse size depends on the maximum controller current.

 

[safe]

I use a car battery charger (that has the three phase recharge routines) that puts out 10 amps and is perfect for deep cycle batteries. It was cheap, but you have to wire your machine so that it can swap back and forth between serial and parallel. If you can figure it out the car battery charger approach is cheaper...