noob: Charging batteries

[scrotty]

I am modding a Razor GF kart to improve battery life and performance.

Out of the box the kart recharges both of its two 12v 7.2Ah SLA batteries via a single port exposed in the kart's casing.

I'd like to upgrade to a 36v system. To do so I will replace the 24v/250W motor with a 36V/500W my1020. I also will change the controller (I'm thinking YK43B) and I'll go with three 12v 18Ah batteries.

But from what I think I've read is that doing so makes charging not so easy anymore; that I cannot use a single charging port to charge all the batteries simultaneously with one charger.

Am I totally missing something? What would you recommend for charging the batteries in such a configuration?

TIA!
Sean

 

[scrotty]

It looks like I _can_ charge three 12v batteries that are connected in series via a single 36v charger - but is not recommended due to the potential differences in resistance between batteries which could mean one gets overcooked while another doesn't get much.

The better alternative seems to be charging each separately (possibly at the same time with separate chargers) while they are not connected to each other.

So to charge a three battery system I'm best disconnecting the leads and charging each individually. Sound right?

 

[OzFab]

Most of that sounds about right but, there are loads of 36V bikes, scooters, cars, etc that charge off a single charger... am I missing something too?

 

[scrotty]

I don't even know anymore! The more I read the more I'm confused. I found batteryuniverstiy.com helpful, though.

I agree with you, Fabroman. I'm coming round to the idea that I _can_ charge all the batteries (connected in series) with a single 36v 2-4A 3-stage (constant, topping, float) charger.

Of course you can find those anywhere from $25 to $250. Does more expensive mean better?

It's never easy!

 

[scrotty]

Well I went ahead and ordered a Veribest 36V 4A 3-stage charger from Amazon. It was USD$96 shipped.

I'm fully expecting someone is now going to reply, "MISTAKE" or "VERIBEST SUX!"

Oh well!

 

[dcastillo]

The better alternative seems to be charging each separately (possibly at the same time with separate chargers) while they are not connected to each other.

So to charge a three battery system I'm best disconnecting the leads and charging each individually. Sound right?

thats what I do... 3 batteries in series to run the cart, then switch them to parallel to charge them...

-D

 

[wesleyb82]

I am not an expert but I have experience with these setups. Variation is possible but if the batteries are in the same condition going in and are drawn from evenly in my experience the variation is minimal. Once in a while I do test them individually and charge them individually with a 12v charger though. But when you buy an electric scooter or gokart with SLA batteries.... they are all setup from the factory with the batteries in series and they are charged in series.

 

[scrotty]

thats what I do... 3 batteries in series to run the cart, then switch them to parallel to charge them...

dcastillo, are you the one who has the super fancy series-to-parallel switcher that uses super expensive components (that you were able to get inexpensively)?

 

[dcastillo]

Yes... they are very expensive 100A plus contacts from hypertronics... but we had a ton of them at work... would have cost me a few hundred bucks on my own...
another option are the anderson powerpole conncters.. stick with the smaller 45A or so versions and double them up using 10AWG for each.. once you move up to the larger higher current ones they get very expensive... that was my setup for a few months till I switched over... had no problem going up to 100A spikes and 40-50A constant...

this is where I got them
http://www.mcmaster.com/#power-poles/=uof23n

 

[ML-TOYS]

Being a powerwheels modifier and former repair center for them i will give my input.
Charging 3 12v batteries in series is fine to do. If you have 3 seperately fully charged batteries installed then run the kart you will be drawing steady enough for it to then be charged at 36v with no problem.
I have done this with 24v 36v 48v all with individual 12v batteries.
I also do the same with 6v batteries with an 18v charger.
The only time its a concern is using different voltage batteries such as modifying from 12v to 18v using a 12+6v then they need seperate charging.

 

[drm]

You can also use three 12v chargers. That's what I do...schumacher 2amp charger/maintainer.