Battery charging from 48v DC

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RobSmith
Posts: 37
Joined: Sun Jul 25, 2010 9:32 pm

Battery charging from 48v DC

Postby RobSmith » Fri Aug 13, 2010 8:16 am

Hi All,

I am wanting to convert our little garden tractor to battery power. See my wanted ad for a motor / controller.
I am not sure what voltage the tractor may end up as it depends on the motor and controller I manage to get.
My other issue is we would eventually and hopefully be off grid and running a huge 48v battery bank.
Are there good chargers available with 48v input?
I am not sure If I should just decide on the house, car, tractor all being 48v or can that cause other issues I am not yet aware of?
My other option is to get a 240v ac input charger but then that would be powered through an inverter from 48v dc so several conversion steps would be needed and probably very inefficient.

Any guidance?

Rob

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Jeremy
Posts: 472
Joined: Thu Jul 31, 2008 6:35 pm
Location: Salisbury

Re: Battery charging from 48v DC

Postby Jeremy » Fri Aug 13, 2010 11:57 am

If you will already have a 48V house battery charging system, that has a safe voltage limit, then I'd suggest you don't need a charger at all, but could just couple the tractor batteries up in parallel with the house batteries.

There is a risk that the initial charge current may be a little high, depending on how much power you have available from your wind/solar/generator system, but that could easily be managed by using a switchable ballast for the initial charge. Once the battery voltage starts to come close to the float voltage you could switch out the ballast (if you found one was needed) and leave the tractor pack connected to the house battery.

If you didn't want to risk using the tractor battery capacity as part of the house battery system then you could fit a split charge relay easily enough, or even an ideal diode. An acquaintance has made up a few ideal diodes for me, they are a very neat way of getting a near zero forward voltage drop isolating diode for charging paralleled batteries.

Jeremy

RobSmith
Posts: 37
Joined: Sun Jul 25, 2010 9:32 pm

Re: Battery charging from 48v DC

Postby RobSmith » Fri Aug 13, 2010 6:34 pm

Jeremy wrote:If you will already have a 48V house battery charging system, that has a safe voltage limit, then I'd suggest you don't need a charger at all, but could just couple the tractor batteries up in parallel with the house batteries.

There is a risk that the initial charge current may be a little high, depending on how much power you have available from your wind/solar/generator system, but that could easily be managed by using a switchable ballast for the initial charge. Once the battery voltage starts to come close to the float voltage you could switch out the ballast (if you found one was needed) and leave the tractor pack connected to the house battery.

If you didn't want to risk using the tractor battery capacity as part of the house battery system then you could fit a split charge relay easily enough, or even an ideal diode. An acquaintance has made up a few ideal diodes for me, they are a very neat way of getting a near zero forward voltage drop isolating diode for charging paralleled batteries.

Jeremy


Hi Jeremy,
I suppose I could use the tractor battery in parrallel with the house so it makes sense to go for 48v throughout all the things we have.
I could even put a light bulb in between the forklift batteries and the much smaller tractor batteries. That would limit the current and then do nothing once the voltages had equalised.

48v it is then.

Next question where do you find a big 48v traction motor and controller for an electric car/van?

Rob


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