Southport LiFePO4 dealer

[MalcolmB]

Hi Greg
Do you know if they're definitely lithium iron phosphate cells? Don't mean to keep harping on, it's just that with a weight of 5 kg they have an energy density of 120 Wh/kg (based on 3V per cell), which would be exceptional for LFP.

[GregsGarage]

Yes they are LFP. The fully charged voltage is 3.65 volts, so 4*3.65=14.6 volts (nominal voltage 3.2). This is almost exactly the final voltage of of AGM/Gell cell batteries. The thundersky fully charged voltage is much higher at 4.25v and my controller can only handle 90 volts so I would either have to use fewer cells or not charge them fully for my vehicle.

We will have to wait and see what these are actually like when we get them. I am getting 24x 100ah cells at around 3.5kg each (I think, don't have the specs in front of me).

Greg

[MalcolmB]

Yes they are LFP

Excellent! It's good to hear I'm wrong...for once

Really looking forward to hearing more about these when they arrive. Could you point me to the correct spec sheets or send me a copy when you've got a chance?

[retepsnikrep]

I've done it as well and ordered 50x40ah cells from David for my PHEV Insight project. I shall be using Cedric's controllers modified to suit the lower voltages of lfp cells or I shall do my own thing.

Anyway cell controllers will feed PIC based monitor and display system which will display pack V, current in/out, capacity and core pack temp on a simple two line lcd screen. Off board 3.5A charger should be nice and gentle when charging, 50A regen from Insight might warm them up a bit but we shall see!

I shall adjust the final number of installed cells to suit V sag etc so I bought a few extras, I'm hoping I will only need 45-48.

Off on hols now for two week's hope to have some good cell news on my return.

[GregsGarage]

I take it that the group buy didn't work out.

For my BMS I have ordered 2x 36v BMS boards from ebay seller Ping Battery (look for duct tape packs on this forum). His cells are the same chemistry and voltage of these cells. The boards will have to be modified as they are designed for e-bikes but should have all the necessary voltage sensing and balancing circuits in them. At the moment they seem to be stuck in customs, hope to have them next week

I will post pics when I get them.

Greg

[retepsnikrep]

I have had word from David that mine and Tim's cells are now enroute on the slow boat from China

Keen now to get them in my sticky mitts

[GregsGarage]

On Monday night I collected my 24x 100ah cells from David. Last night fitted them into my Fiat 126 after fully charging them. At the moment I am using 6x Ring RSC16 Smart Chargers. Although these are designed to charge all types of lead acid, including sealed and gel cell batteries, they provide constant current of up to 16 amps until 14.5 volts and then supply constant voltage until the current drops to 2 amps. At this point they switch to float mode.

I have had problems in the past of these chargers dying in float mode and sent several back. Got a refund but no explanation of why they failed, so I switch them off as soon as they get to the float stage.

The hipower cells specify 3.85 volts for the cutoff which works out perfectly as 14.5/4=3.63volts. So I am not quite getting a full charge but near enough without a BMS.
I watch the individual cell voltages with a volt meter and connect a 12v 5w bulb across any that are getting higher than the others. Max voltage I saw during charging was 3.75 volts. After driving home and back to work (22 miles total), letting the car rest for an hour I checked cell voltages, all exactly 3.33 volts.
The e-meter showed 44ah removed from the batteries, so I think this is excellent!

I have connected a Paktrackr to my pack so I have a read out of every 4 cells, basically the Paktrakr sees 6x 12volt batteries. It was reading battery 3 slightly lower voltage under load and the battery interconnects were getting slightly warm. I don't think much of the supplied interconnects or the slot head aluminum screws supplied. They need to go in the bucket and be replaced with something better, might start a new thread regarding this problem.

Thanks to David for supplying the cells and keeping me updated with their progress.

[retepsnikrep]

Pictures!!! Please!!!!!!!!

[GregsGarage]

O.K. Peter since you asked so nicely here is a not very good picture.



I was short some interconnects so used the ones I had lying around. You can see my chargers connected. I charge with all of them until they get to the constant current phase then for the constant voltage phase just one charger at a time in turn. You can see the test light I am using across the cell with the highest voltage, crude balancing and time consuming, must get the BMS sorted!

The eagle eyed amongst you will notice that I appear to only have 5 black charger connections, the 6th is connected to the load side of the e-meter shunt so that it can count the current going back in.

Greg

[retepsnikrep]

I don't think much of the supplied interconnects or the slot head aluminum screws supplied. They need to go in the bucket and be replaced with something better, might start a new thread regarding this problem.

Greg

What current have you been pulling?

What Voltage sag have you seen so far?

Peter