Replacing lead acid batteries in an electric bike battery pack.

Hi folks.

Several years ago I replaced the batteries in my ex's bike, when I dismantled what I assumed to be the battery pack in it's original state it contained six 6v (16ah if I recall correctly) batteries, I bought identical batteries & wired them into the box exactly as it had been before & unsurprisingly it worked perfectly.
The bike is now mine and as I said that was several years ago, the bike has seen a lot of use since & the pack has been discharged & recharged sometimes several times a week ever since, the bike is now lacking power, hills it used to climb with ease are now becoming a struggle & the bike is generally not as fast as it use to be so I have been looking around for another set of batteries planning to replace them once again.
When I started looking around the web for suitable replacements for my model of bike every site I found with deals for a battery set lists not six 6v but three 12v, dimension wise they are not a problem as the three batteries will fit quite nicely into the box but I have to admit I was a little surprised.
I will be honest I'm not as well versed on things like electric bikes as I would like to be & frankly the whole thing is a bit of a mystery to me, ask me for a table a workbench a garden swing or a shed & I'm your man, I can rebuild computers & set up networks without a problem and there are plenty of other things that I'm very good at but with this stuff I need advice.
My question is simply this, is there any advantage or disadvantage for that matter to using three 12v 15Ah rather than six 6v 16ah batteries.
I would prefer answers in plain simple layman's terms rather than lots of technical jargon, if it helps the bike is a Thompson Euro Classic with a 36v lead acid battery pack and rear hub motor, admittedly a bit of a dinosaur in electric bike terms but it still gets me around well enough I'd just like to get a bit more power out of it.

Thanks in advance for any help.

Picture of Replacing lead acid batteries in an electric bike battery pack.

It depens what the bike actually runs on.
But with 36V it does not matter if you 6V or 12V batteries to get 36V.
And using 3 instead of 6 batteries is better anyway.

Nostalgic Guy (author)  Downunder35m1 year ago

Thanks for the feedback, I've been looking around again this evening & all the packs I have so far found are quite similar give or take an Ah so I think I'll just pick a good brand & price and give it a try, I did suspect that three would be more efficient than six but as I said I'm not really that good with these things, it's just a shame I cant halve the weight too, in total the battery pack will come in at around 27lb by comparison to a more modern bike my sons 36v lithium battery weighs 4lb, of course on the up side mine will cost about a third of his to replace.

Of course you can use a 36V Lithium battery instead but as you pointed out they are expensive and also require that you change to charger suited for them.
Can quickly go into the hundreds of dollars...
When you do get your batteries make sure they are fully sealed and rated for any installation position including upside down.
This way you don't have to bother with leaking batteries ;)