40 Amp Power Supply to Charge LiFePO4 ?

[nut17]

Thanks Terry. Apologies for not acknowledging your reply sooner. Have been on the road with limited data and have priorities now that I have taken over as Admin here http://www.nzmotorhome.co.nz/NZMotorhomeForum/index.php
That 50 Amp Projecta does look pretty good and my battery pack has kept pretty much perfectly in balance up to 14v, so leaving it to get on with it without intervention would be a pretty safe option. At three month intervals I do a manual balance up to 3.65v / cell - using a couple of coil ballast resistors connected across the cells that start to spike. This process only takes around 30 minutes to complete with my 50 amp charger and 600AH LiFePO4 battery bank.

Smart Marine can supply one for NZ$749.00 freight free so I will probably do the deal with them.

Cheers
Chris

[nut17]

The Projecta charger arrived this morning, so should get some time to get it installed and up and running today. A smart looking unit with a nice neat wall mountable remote control.

Cheers
Chris

[nut17]

I did a temporary install and hooked the new charger up this morning. Battery was at 588 AH remaining and sitting on 13.3 volts. I plugged the new charger in and set it to "Gel". It took 15 minutes to take the battery to 600 AH (100%) at 14.1 volts, then drop back to float at 13.6 volts. I have all four pairs of cells almost exactly balanced at 3.4 volts. As this charger will seldom be used when on shore power and really only be used when on the road with the Jeep powering it it will spend a minimal time in float mode. My solar float is set to 13.3 volts and seldom putting in more than a couple of amps. Finally getting close to a "set and forget" situation with checking cell balance about once every 3 months.

Still not very efficient. Drawing 80 Amps at the inverter and putting 46Amps into the battery. The Jeep does have a 260Amp alternator and feeds a constant 80 Amps at 14 volts so not really an issue.

Cheers
Chris

[T1 Terry]

I did a temporary install and hooked the new charger up this morning. Battery was at 588 AH remaining and sitting on 13.3 volts. I plugged the new charger in and set it to "Gel". It took 15 minutes to take the battery to 600 AH (100%) at 14.1 volts, then drop back to float at 13.6 volts. I have all four pairs of cells almost exactly balanced at 3.4 volts. As this charger will seldom be used when on shore power and really only be used when on the road with the Jeep powering it it will spend a minimal time in float mode. My solar float is set to 13.3 volts and seldom putting in more than a couple of amps. Finally getting close to a "set and forget" situation with checking cell balance about once every 3 months.

Still not very efficient. Drawing 80 Amps at the inverter and putting 46Amps into the battery. The Jeep does have a 260Amp alternator and feeds a constant 80 Amps at 14 volts so not really an issue.

Cheers
Chris

This is scary but in this case Peter OldTrack is correct, you need to compare the watts in against the watts out to calculate the efficiency. So the 80 amps on the input multiplied by the actual voltage at the input side of the inverter divided by the amps out multiplied by the actual voltage on the output side of the charger, my guess would be around 15% efficiency loss, not close to the 50% the amps in v amps out suggests.

T1 Terry