Re-celling to LiPo
I want to leave what I found for the next person that wants to go to LiPo batteries. At this point I am a big believer in a PCB and the proper charger. I am not the first to go to LiPo on here, but, this is what I have learned for the next guy.
There does exist a real fire concern from LiPo, seriously overcharge them and they will go off, plenty videos of this on YouTube. These concerns are from the R/C community and do relate more to their much faster discharge and charge rates and the fact they are in object that can crash. We charge much slower, use PCB’s that guarantee individual cell charge rates that minimize the risk and will not allow overcharging or the drain of too much energy. With PCB’s they are setup just like li-ion batteries from the manufacturers. The risk is still there though and if you want to go this route you must make sure that another charger cannot inadvertently be hooked up as that is a fire surely. You should also commit to placing the charging station on metal and away by itself. I am also going to start using fiberglass bags designed for LiPo’s by the R/C industry, overkill to be sure, but, it is better to be safe.
Why use them with this concern then? Weight and size, battery weight for the same output is half or less and so is the size. How is that possible? LiPo does not use a hard casing, there is no metal casing just a hard to the touch little rectangle. In a different thread I printed a very small little battery that works great as a battery for the top of a rod. It would have had too much weight to be as effective in NiMh and honestly I see little to no safety difference between li-ion and LiPo
I had the parts for this and we could use it, so, I took picture as I wired it.
A simple re-cell of an old NiCd battery. This is an old Geodimeter radio battery from a long time ago.
It is a glued split half battery that has 10 cells and a small circuit board and integral DINI plug. Our LiPo batteries will fit leaving the circuit board and DINI plug, so, I am leaving them. This battery has been re-celled before as can be seen from the super glue left in the sides and the stains on the circuit board.
Scrape as much off as we can of the super glue residue and generally just clean up the old veteran.
A LiPo battery is 3.7 volts per cell so three of them is 11.1 volts. You can use four, but, you would have to wire in a step down regulator as that would be too much voltage. This is a battery for a radio that has a built in regulator, so, we don’t need to worry about a regulator as the radio will take the power out of the battery to its built in threshold for NiCd of 10.6 volts. This is well above the damage threshold of LiPo of 9.0 volts. The Protection Circuit Board (PCB) shown below will not let it be charged over 12.6 volts (using proper charger) or go under 9.0 volts in use. Please note this example is a simple example because we are not wiring in a regulator. If we did add a regulator we would wire a charging circuit and a powering circuit, so, that the charger had a direct path to the PCB.
Our batteries hit the circuit board with their leads so I have shortened them and tinned them with solder
I cut some leads using some old speaker wire I will never use. Many times you will have severe space limitations and need to use a very high quality wire that is small but can still carry the current. The radio is very light draw so a good time to get rid of the speaker wire.
My extra room is too the right side so I make the leads go that way. We are going to make layers of cells at this point and the negative for this stack is our B- for the array. I can’t heat shrink these end with the leads going in this direction, so, I am taping them with two layers.
Here where it gets weird if you haven’t dealt with LiPo before. Connect the positive of the bottom battery to the negative of the next battery and bring a lead out from this. Depending on your PCB this is either B1 or B2 and only your instructions will tell you. This PCB is different than any other I have seen as B1 is next to B-
Finish the top layer and you have B-, B1, B2 and B+
Tin the terminals on the PCB with solder
Wire to the appropriate terminals. I start with B- and then add B1 (in this case, most of the time B2) and then test for current to make sure I am getting one batteries worth, because, if you don’t it is wired wrong. Then connect the next lead and test and so on.
Then solder leads onto the main PCB out + and -. Try to be consistent, I always use the red wire or the marked wire as positive. At this point the PCB should be dead to current across the out leads, but, don’t push fate and keep them apart.
Solder the leads into the batteries output circuit. The PCB will not come alive in theory until you hook it up to a smart charger and it gets that current. I have done so many of these I have no fear on this setup, but, this may be the time you need to figure out how the connect that smart charger to make sure it is all wired up correctly
Some foam to control rattling
Glue, clamp and connect the smart charger. I 3D printed this attachment for the smart charger and you may just want to cut the smart charger wire and splice it into your system.
A caution on this, you may know what is what but employees do not care as much. I have made very sure that the systems cannot be interchanged so that someone cannot hookup a NiMh charger or something. I can’t stress this enough as that WILL cause a fire. At this point all we have is LiPo. Do you also notice that my test bench ended up with the first print of the charging adapter as i just couldn’t put it in service, LOLParts used in this
PCB http://www.batteryspace.com/PCB-for-11.1V-Li-Ion-Battery-Pack-4.0A-limit—–PCM-L03S04-559.aspx
Batteries https://www.batteryspace.com/polymer-li-ion-cell-3-7v-2000mah-605060-2c-7-4wh-4-0a-rate—ul-listed-un38-3-passed-ndgr.aspx
Charger https://www.batteryspace.com/smartcharger08afor111vli-ionpolymerrechargeablebatterypack–ceullisted.aspxGood parts to know about
Very small regulator 200mA max http://www.getfpv.com/electronics/voltage-regulators/12v-step-up-step-down-voltage-regulator.html
Bigger regulator 2 amp http://www.dpcav.com/xcart/Adjustable-Voltage-Regulator-1-35V-SEPIC-Type.htmlPlease feel free to add
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