Here is a link I stumbled onto while looking for Greg's LiFePO4 pack he was talking about. I had previosly found a site where I could buy 2, 3.2v cells and PCM for about 88 bucks. A charger at 4a would run about 25 bucks. This deal here looks very good, I will have to research it a little more, but.... the cells are already made, they have a PCM, plus they include the charger! All wrapped in a nice conatainer that looks like it is weather proof and could be further sealed with resin. ALL FOR $94.99 www.bioennopower.com/products/6v-12...abs-sealed Big difference I see is the former set up would have 20AH and the latter has only 12AH. What do you experts think? is this a good thing or is there better deals or set ups?
My next large-ish LiFe purchase will be the Headway cells. They are good quality and are inexpensive at $19 for each 10Ah cell, or $29 for 15Ah. headway-headquarters.com/headway-cells/ I already have a charger that is LiFe compatible , so YMMV as far as total price.
Well what ship are you putting it in and what sort of gear are you wanting to power with it? Without that info it is pretty hard to determine a good deal from a bad deal.
What site had 2 of the lifepo4 cells and pcb for 88 bucks? I use 4 of the 20ah cells in my Baden. The main reason I didn't use a PCB was the current limit they have built into them. I estimate I pull around 65 to 70 amps with both of my titan pumps running and pumping as well as driving. It may be well under that but most PCB's for 2 cell lifepo4 capped out at 20amps. I bought this (equivalent.. they don't sell mine anymore) http://www.batteryspace.com/LiFePO4-Prismatic-Module-3.2V-20-Ah-10C-Rate-64-wh.aspx The prismatic case is tough and the cost is cheaper than the headway cells (which are unprotected metal.. at least the last time I saw them). I also heard the PCB can limit the rate at which you charge making it take much longer to charge. Once I get a good amp test done on my ship I might be able to find a pcb to use .. .but it will also be another failure point. As far as 12AH for $95 bucks.. too expensive. Its just a plastic case ..... Johnny
www.batteryspace.com/LiFePO4-Prisma...64-wh.aspx x2 www.batteryspace.com/Smart-LED-Bala...rrent.aspx x2 These are what I think we need for the Mutsu and Baden, I am not sure what the constant load is yet.... when using the older SLA batteries we used 2 6v 12AH's in parallel for the baden all day. The Mutsu used same batteries but changed to a new set at noon. The baden is using a single 6v propulsion motor, 1 bilge pump, nothing fancy just the standard silver cased 550's, and firing 4 kips. The Mutsu is using two 6v propulsion motors,1 bilge pump, nothing fancy just the standard silver cased 550's, and 4 kips. Both MWC fastgun
That 20ah cell is fast becoming the cell to use in our ships. The size fits into most medium and larger ships without any issues. I run four cells in a Scharnhorst with plenty of room left over and still had to add 3 pounds of weight to the ship. The LiFE cells are amazing. If you would like to save $16 and wouldn't mind getting four cells, look at www.batteryspace.com/LiFePO4-Prisma...t-PCM.aspx. The plastic case contains four 20ah cells and are easily removed by popping the top off the case and sliding them out. All for $124 ($31 per cell).
Honestly, that's not a lot more than 2 pair of 12AH 6V lead-acids, when you add shipping. Even going to a Battery Mart retail outlet, the classic 12AH 6V was $25 each, marked up so that you don't save any money over ordering online. The salesman was apologetic, but that was the price. I had been planning on the lead-acids for Malaya, but at $124 for 4 of the LiFe cells... How are the cells jumpered together inside the case? Wires or bus bars?
That PCM only balances... you can most likely charge the individual cells faster and save the money for the Pcm cards. Those PCM don't stop over-discharging.. so why bother. I use 1 charger per cell and do the series/parallel hookups in the wire harness. Makes it easier to replace a cell if I need to without having to swap out the entire pack or tear one down. As I charge each cell on their own they are usually all at 3.6 to 3.65 which is fine. They don't stay in balance under discharge anyway to .05 volt does not make a difference. I have had the same set since 2010 and they have never run better.
hopefully not steering the thread too far off topic, but I buy my SLAs from atbatt.com. think I usually pay about 16-18$ for a 6v12ah, and once you pass 75$ on the order its free shipping. Out of CA so no tax for me.
Jeff and I are going to try out the 20AH cells. Both ships will use two cells for the 6v's needed. I may use a PCM for charging, not sure. My biggest concern is how to prevent overcharging as this will damage the batteries. I have no idea what my AH draw is on y motors and guns. SO I need to figure out how to get a meter for this or take a WAG! Anybody have a baseline guess for two 550 motors for drive, 1 550 motor for pump and firing 4 kips at a time for the stern guns...
If you use the 'smart' charger that I do, you wont have to worry about over-charging. In fact I have yet to even see a 'dumb' lithium charger that just charges until you unplug it. I also bought a 4 port computer charger that I like as well but its pricey for 2 cells. Smart 'brick' charger 6 amp rate http://www.batteryspace.com/Smart-Charger-6.0A-for-3.2V-1cells-LiFePO4-Battery-Pack-100-240VAC-CE.aspx If you run 2 cells at a time then I would get two of the brick chargers so you don't have to charge all night. The nice thing is you have lots of extra AH compared to lead acid and you will start using some of it since its available. I estimate you use 3 amps per drive motors maybe 8amps on the pump motor on full load, Kips will be about 1.1 amps per so 4.4 amps if you fire them all at once (approx.) but the Kips probably get .5 seconds per press (estimated) so if you fire all your kips at the same time and have 1 unit guns that is 50 trigger pulls. That means 25 seconds at 4 amps.. basically negligible usage of AH. .. maybe 1.8 AH tops. So if you ran your pump full time @ 8 amps, drove full speed non -stop, and fired all your round within a half hour you would use about 9AH tops. Which is not much but it does mean you could use your batteries for more than one battle. It also means if you only buy 2 cells that it will take more than an hour to recharge the cells using the 6.0 amp MAX RATE brick charger I listed above. 6 amps is the max rate you want to use to charge those cells so if you have 9AH to put back in you will need a minimum of 1.5 hours to recharge.. not enough time between battles... at least where I go. If you only get 2 cells you will also not have a spare and will have to pay the HAZMAT fee plus shipping again for one cell making nearly a $75 for the replacement cell. I wouldn't count much on warranty.... So for my 8 cells I have 6 of the brick chargers listed above and a computer charger with 4 ports. That way if I drive across country... and my computer charger dies.. I can still charge my batteries.. and if any of my 'brick' charger dies.. I have the computer charger to pick up the slack. With my setup this year at nats, the brick chargers took about 1 to 1.5 hours to recharge. Last year over 2 hours to recharge so I know I was using approx. 12AH per battle last year. I didn't have enough brick chargers in 2012 to charge all my cells and fell asleep before the first set of cells had finished.. thankfully they had power at the pond but it took all morning for the second set of cells to charge and nearly had to miss a sortie/battle because of it. I promptly ordered more charges to solve that issue. If you only have 2 cells in your setup, don't take much damage and don't stay on the water more than 30 minutes you might be able to get in 3 battles. Any heavy pumping would ruin that schedule though... Johnny
Oh and I don't use a PCM for over-charge protection .. never had one.. I DO want a PCM to prevent over-discharge but need one that can handle 60+ amps.. haven't found it yet.
