Battery pack - lead to lithium

[Night Train]

I am working with a friend's EV. It is a warehouse type road legal truck running a 48V pack consisting of eight 175Ah 6V lead batteries.

The current range is 3-4 miles at 15mph stop start use after an over night charge followed by another 3-4 miles after a 2 hour lunchtime charge. The pack is sometimes so low that the truck needs pushing back to base part way through the range.

I took some voltage readings one day to see what was happening.

The readings were taken (A) prior to setting out in the morning with an 8 hour charge, (B) on return after 3.8 miles, (C) after a 2 hour lunchtime charge, (D) on return after 3.8 miles at the end of the day.

A-----B-----C-----D
6.6v 6.2v 6.6v 6.3v *

6.8v 6.5v 6.7v 6.4v

6.7v 5.6v 6.7v 5.7v

6.6v 5.7v 6.6v 6.3v

6.7v 6.4v 6.7v 6.5v *

6.7v 5.6v 6.7v 6.4v

6.6v 6.3v 6.7v 6.2v *

6.7v 6.5v 6.8v 6.4v

* Batteries replaced last August 2011. Rest of the pack new in Jan 2011

The thought is to either replace the whole pack with lead or with lithium.

In theory the 175Ah lead could be replaced with 110Ah of lithium for the same usable capacity. However, given the lead pack is used down to empty would that mean that a much bigger lithium pack is needed? Thoughts please?

Are there any UK lithium stockists where I can get an estmate of cost for the pack?
I guess I would also need to add BMS and charger to the cost too?

Cheers.

[retepsnikrep]

Are the current batteries really getting a good full equalising gassing charge? Assuming they are wet cells of course.
They look out of balance for a start. I would have thought that power and weight of lead would give more than 3-4 miles at such low speeds Does the vehicle weight a huge amount?

I bought my Hipower lithium cells from the below he was/is? an importer dealer for them. Pleasant chap.

David Cowperthwaite
213 Fylde Road
Marshside
Southport
Merseyside PR99YB
Tele No 01704 220961
Mobile 07876693767

[Night Train]

I doubt the batteries are getting anything other then the 20A output charger plugging in each night. How would I set it to equalize?

The truck weighs about 650kg and is then collecting a payload that gets to maybe 500-700kg. As it does collections it gets heavier as the pack gets weaker.

I sat in the back with an ammeter held on the pack cable while it went for a short drive unladen. It showed about 50A running with a peak of about 100A, or just over, moving off.
It does constant stop start pretty much door to door so I am guessing it spends more time at 100+A moving off then it does cruising at 50A.

Thanks for the battery supplier contact.

[GregsGarage]

I have also used David, great supplier. Regarding pack size I would probably aim for something closer to 150-200ah capacity. The cells won't be worked as hard and will last longer and the extra range wouldn't hurt either.

[Night Train]

OK, things have moved on a bit. They have got funding to replace the lead acid pack like for one up to 205Ah to buy some time. The vehicle is more worn out then earlier thought and so I have this year to find a suitable replacement.

It will need to be narrow and with a long, low loading bed and the ability to tow a trialer.

Any suggestions for manufacturers/suppliers?
Epower is too big and has too many non essential luxuries bumping up the cost.
Mega is too small.
Both are too wide and have high load beds.
Bradshaw isn't really suited for road speed and mileage, being a warehouse truck.

I suppose a tractor trailer might work but adds to unladen weight.