Re: (ET) 48 volts (was Curtis controller mod)

["David Roden" <etpost drmm net>]

I know of someone who boosted his ET's battery to 48v back in the late 
1990s 
or early 2000s.  I seem to recall that he built his own armature 
controller 
and ran at full field (48v).

He did NOT, however, apply 48v to the mower motors or other attachments.  
He 
used a separate PWM controller to bring the voltage for the mower motors 
and 
other attachments down to the original 36v. 

This guy is a pretty canny EE and I I assume he knew what he was doing in 
not using 48v for the attachments.  So I think that would be an issue for 
you.

Other thoughs:  

First, I've also seen plenty of 36v lithium batteries on offer.  So you 
could avoid the potential problem of overdriving the mower and other 
attachments by getting a 36v battery instead.

Second, some of those cheap Ebay lithium batteries are outright garbage, 
made with factory reject cells and/or cells recycled from old laptop 
batteries.  Be careful.  Do some research on e-bike forums such as Endless 
Sphere, where they know the good batteries from the junk.

FWIW, I have three lithium iron phosphate batteries made by Ping, two 24v 
and one 36v.  Mine are 10ah, but they're available up to 30ah and up to 
72v.

They're working very well for me and holding up nicely.  They come with a 
fairly sophisticated BMS (battery management system) and a cheapish but 
functional charger.  I can recommend them for any use where you don't 
routinely and consistently exceed 2C (that is, for a 10ah battery, 20 
amps). 


They are not cheap, and the shipping from China adds significantly to the 
price.  (Unlike some of the Ebay sellers they don't use slow boat 
shipping.) 
But after using them for some years now, I think they were worth the cost. 
 

As long as you balance the tractor front to rear, I don't see why the 
reduced weight would be a problem.  You might have less ground friction, 
but 
you're also moving less mass.


David Roden - Akron, Ohio, USA

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