how to wire to run batts in serial then charge parallel

[mntjohnson]

My 3 12v batts hook up in serial to run bike, but I would like to also have parallel hookup to charge with 1 small 12v charger I can carry aboard to all batts (so 1 wire goes to all positive and 1 wire goes to all negatives of batts). But I think you can't have connection between positive poles of batts if you want serial hookup, right? Has someone clever thought of easy way to switch from parallel to serial hookups?

If this fails and this shows my lack of knowledge how do 36v chargers work? I guess the 36v chargers simply hook up to the 2 ends of 3 batts hooked in serial and somehow by using 36v then each 12v battery is charged at 12 volts?

TOM JOHNSON

 

[dumbass]

Tom,

First off you don't say what kind of batteries your dealing with. If they are lead or lifepo4 without a BMS then I can tell you a simple fool proof way of doing what you want. I guess you could do it with switches but it would require a lot of switches and you could make a mistake. I run 24v packs and made Anderson plugs to convert from serial to parellel for charging. It would be a simular setup to do this for 36v. While riding the pack is pluged into the bike where it is automaticly setup for serial connection (36v). When charging the pack is pluged into a second plug on the charger that keeps the batteries as parellel and charges them. I was charging up to 8 12v Sla and/or lifepo4 batteries at the same time with 1 charger. The big advantage is once you make the plug (correctly) you can't make a mistake. It will alway be wired correctly for serial to the bike and always be wirred correctly for parellel charging. All you do is unplug from the bike and plug into the charger and vise wersa. No more work or brain thought then pluging in your charger. The only draw back is making the Anderson connector plugs but you only have to do that once.

Bob

 

[TheKraftyRhino]

I did something like this when I first got into Ebikes. I used a project box from RadioShack (The place that don't sell radios) and some 3 way household switches. Drilled a hole in the flip arms and connected them together by passing a coat hanger threw them all so they all flipped @ the same time. In the end it worked but that unit now sits in the junk pile as it was easy to buy the proper size charger all be it a cheap one off ebay for $15

 

[torker]

36 and 48 Volt chargers are really cheap. My 48 v was only 22 dollars I think. Once you go above 48v it gets kind of expensive though.