Wednesday 25 December 2013

Lithium Batteries - Top Balance and Install


All 17 of the HiPower 100 amp-hour 'short' lithium iron phosphate cells arrived by UPS in good condition.  They were packaged in pairs in cardboard boxes padded with foam inside and secured by straps outside.  Each battery has a sticker with the serial number. 




A separate capacity and internal resistance certificate was provided (paper left of the cell above).   For best overall battery pack performance the values should be tightly clustered (+/- 5%).  A scatter plot of the capacity versus resistance is shown below.  All cells are shown to be greater than the 100 amp-hour rating.  The lowest capacity was 101.5 amp-hours and the highest 107.7 amp-hours.  The internal resistance varied from a low of 0.20 to a  high of 0.32 u-ohm.



Here are the batteries hooked in parallel so they can balance with each other and get their initial charge from a Cell Pro Powerlab 8. 




While the batteries were being charged, I removed the four dead Trojan T-1275 deep cycle lead acid batteries from the golf cart.  Here is a picture of the thick wall plastic battery box.  Note that the bottom has ridges and curves which does not conform to the smaller footprint of the lithium pack.



I created a template of the cart battery box and custom cut a plywood deck. 



Sixteen of the cells fit nicely in two rows.  They are secured by custom fitting some wood around the base.  Three-quarter inch diameter vinyl tubing was cut and split to fit over the bus bars and terminals to help prevent accidental contact.



A 48-volt 600 amp Blue Sea Systems battery disconnect switch was installed under the seat.  The switch provides a way to ensure no parasitic current drain and provide a safety cutoff during maintenance. 



An inexpensive +/-1% Amico 200 amp-75 mV shunt was installed in the negative lead to provide a way to measure current flow.  A more accurate (+/- 0.25%) shunt will be ordered after testing the actual amp draw in operation.



Next steps are to install the JLD-404 meter.  This will require un-switched (continuous) power out of the Sure Power 48V to 12V DC-DC converter (model 41020C00).  Unfortunately the un-switched pin #4 was not being used and did not contain a lead wire.  Had to order a new Deutsch DT style 6-pin connector.

I had also ordered an EX-RAY speedometer / odometer for an E-Z-GO Golf Cart, but did not specify the RXV.  When it arrived the mounting plate did not fit the steering column.  Called EV-Drives.com and ordered a replacement.  Got a return authorization and will send back the one I have for a refund.

Next first test drive and battery pack re-charge.

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