New 25 Amp Powerchair Charger

[Burgerman]

JoeC, how did your new 25 Amp charger work out?

My dual 12v isolated one turns up tomorrow. (20 amp total - 10amp x 2 outputs for overnight charge and battery balancing and waterproof so I can spill beer on it)

And I have been looking at cables again! 8 AWG Gauge is 10mm square. They are only good for about 50- amps. How do I know? Because using my bench power supply and just charging batteries down 2 metres on them (2x 1 meter) I lose a full volt. And they het very warm/hot at 40 amps. The 6mm ones as fitted to a stock F55 powerchair start to smoke at 40 amps continuous charge for 3 to 4 mins... And show about a volt and a half loss. I have to turn down the power as they look likely to melt.

So it seems 100 (8 gauge) is too small. I think you were using smaller still 10 gauge if I remember correctly?

We need 48 volt systems. Its getting silly.

With 160 amps on your DX system you should theoretically be melting those stock cables? No wonder they have a short boost time and rapid current foldback on powerchairs is there!

[JoeC]

To be honest, I haven't had a chance to finish the chair wiring for it yet. This weekend I laid down a lot of brick to widen a path into our back yard to get wheelchair access to the large concrete slab behind our house, and then had a nice day out. I found a nice padded lunchbox to carry the charger in, with a carrying strap and zippered pouch for extras. I checked, and all of the wires coiled up fit in the bag fine.

For anybody else using the Iota charger, be advised that it has a couple of mounting tabs sticking out the side, intended for mounting the charger to a chassis or charging station. I had to bend those flat against the housing to make it easier to fit the whole thing in my bag.

It's true that some of my wiring is 10 gauge- what's worse is the 14 gauge going from the controller to the motors. It's true that the wires heat up a little, but the average discharge is quite a bit lower than 160 amps. Considering that she can play hard for at least two hours without draining the battery 100%, I would say that the true average current is only around 25 amps. With regeneration slowing drain on the battery and increasing average current seen by the cables, it may be as high as 30 amps.

I'll be using 8AWG for my 25 amp charger, and two 10AWG paralleled in the new chair wiring.

[Burgerman]

That should work great. I am using shortened 8 gauge (10 square mm) cable on my current powerchairs. 6 Square mm is standard and about 8 feet of it! You really would expect that the manufacturers would use overkill rather than cables that actually smoke under load! But again, why am I not surprised!

Strange you should mention bricks... Been doing that for 4 days!

During, and after (photo just now) back of house. Sick of the mess and now its all w/c freindly. Just about to rotovate and relay the lawn about 12 inches higher and level... Its winter and cold and wet here and I have just come in after many hours of work cleaning up!

[JoeC]

With a factory installed 100 amp P&G module, it's not hard to use a PP1a programmer to make a P222SE to work hard enough to smell hot.

I use wire with silicone insulation whenever I replace heavy wire. I trust it more than the stock PVC insulation not to melt if it becomes warm, and it should be more resistant to cracking or other breakdown over time. I'm just using a car jumper cable for the Iota charger.

[Burgerman]

I get my 10mm and 6mm from ebay. Or search for 8 gauge etc. Surprisingly cheap from some places. I worry about silicon insulation because of fragility on sharp edges. Used to use it on model stuff but had a few "problems" involving much smoke! That stuff is available from model shops online. But if its getting hot then its too small anyway???

[JoeC]

The silicone insulated wire that I use comes from here: http://www.robotmarketplace.com/products/0C-WI8Gr.html

It's not cheap, but the insulation is thick and tough, it's very flexible, and I know that silicone is very resistant to almost all chemicals. I have seen too many car jumper cables that are a few years old and have started to crack and disintegrate, so unless I know the insulation is reputable I prefer this stuff. It also stands up well to soldering- it seems like whenever I do soldering near the ends of large wire, PVC insulation starts to melt and shrink back. The silicone stays where it is, and you can hardly tell if it's hot. I put PVC sleeve over the pairs of silicone to add a second layer of protection against pinches or abrasion.

[JoeC]

I started building the new battery cable last night. It consists of a few inches of stock cabling ending in a DX battery connector and one side, and a 50 amp Anderson Powerpole connector on the other. The main run of wire from the front battery box to the rear battery box is going to be a double run of 8 AWG, equivalent to two 8 mm^2 wires. The rest will probably be doubled 10 AWG- I checked, and the stock was doubled 12 AWG.

Observations- it was HARD to crimp the anderson connectors! It took some work, and I just hope they're tight enough. My crimp tool never had a problem on the DX or 30 amp powerpoles. If they get the a bit warm during use, I'll make the extra effort to check voltage drop under load. Also, my poor soldering iron was not up to the task of soldering 8 AWG. I had to help it out with a butane lighter to get good wicking of the solder. I'll be picking up a 100 watt iron today to finish the cables tonight.

[Burgerman]

I didnt know you could, or were supposed to do that! I always solder them.

And these http://www.wheelchairdriver.com/images- ... minals.gif

The 10 sq mm cables are a perfect fit.

I use a 100 watt iron to tin the wires.
I use a small amount of plumbers flux to help.
I then use a small blowtorch with care And melt some solder into the holes.
Then heat up the connector in a flame and then push the cable in while holding the insulation with a damp cloth.
It results in a neat soldered connection without any melted insulation.

Post some pictures? My 10 sq mm cable is 8mm outside diameter. Fits beutifully in the battery and Anderson connectors. I used to use the 50 amp anderson connectors to run an off board starter on my drag bikes. They take 200 plus amps without a problem.

[JoeC]

I'm not sure if I should post a picture of my crimps, they're probably not up to standards!

According to Anderson, the preferred method of connection is a crimp:

http://www.andersonpower.com/products/use.html

I have a $10 crimp tool, like an oversized pair of pliers. Their crimp tool uses a toggle mechanism that provides a huge mechanical advantage, and they have precision dies specified for each connector. Probably $250 worth of tools to do it as correctly as you would see in a factory made cable.

Their second method is soldering, and your method sounds very good. Since I don't have the ideal crimp tool, your soldering is probably better than what I get from crimping. After I get my high powered iron today I'll solder my crimped connections for extra integrity. After I crimped them I pulled on the contacts very hard without any movement, so I know they are in good contact.

[Burgerman]

I think you may struggle to solder them effectively with a 100 watt iron. I tried and it takes forever, melts outer and leaves an unsure joint where you dont see the solder melt, run and set. A small butane torch is almost instant though. Dead easy and neat. Practice makes perfect! The secret is just enough heat, pre tinned, not too much solder!

Trouble is practice costs connectors! I buy the things in packs of 20 foe £1.70 each inc delivery. Not genuine but some cheaper make. They work and mix with the "real" ones fine.

http://cgi.ebay.co.uk/Anderson-SB-50-Gr ... 2c4ca8e20b

If the link works. He has them in tens too. Combined postage is cheap.

[JoeC]

I just returned from the store, and I had a choice between 60 watts, or one switchable between 150 and 230 watts. Guess which one I bought

[Burgerman]

That might do it. Let me know i might buy one. My 100 watt one is 35 years old! And its bulb is gone.

[JoeC]

I ran out of heat shrink tubing to cover some wire splices in the new battery cable, so I stopped before I got to the Anderson contacts. The 230 watt setting heats up in seconds to a glowing red, and the solder flows quickly and easily into the 8 AWG wire. What a change! I was able to work quickly enough that the PVC insulation on the stock parts looks untouched.

[JoeC]

Thanks for the tip on soldering Anderson connectors- the 230 watt iron is working to wick solder into the joint, but the insulation gets quite hot. If I wasn't holding everything still in a panavise, I wouldn't be able to hold the wire and would likely mess up the PVC insulation.

[JoeC]

We ran the Optima's down below 24 volts for the pair tonight with the new battery cable, and the Iota charger has been working beautifully for the last two hours. It held steady at 24 amps as it went up over 27 volts over the course of an hour or so, I didn't measure it at its peak, and tapered down steadily after that. As will be no surprise to you, nothing got even remotely warm to the touch, and the whole charging experience was very uneventful. I am letting the chair sit on this charger for the next few hours. The fan wasn't overwhelmingly loud, but I wouldn't want to sleep or enjoy a movie while it's on.

[Burgerman]

Yep that charger should work great. It is only tickling them!

Optimas will be at about 90 percent charged after 1.5 to 2 hours. A bit longer with Gels.
And then the last ten percent will take several hours...

You never quite get as "full" charge by fast charging (say 0.5c up) due to slight electrolyte stratification. Worse with Gel.
If you do a "full charge" from discharged with a 10 hour rate (5 or 7 amp) mobility charger and compare it to a fast charge from a 30 amp+ charger or 100 amp from a van there is about 4 or 5 percent difference in actual available capacity. As measured and graphed with this

http://www.wheelchairdriver.com/hyperion.htm

So its still best to use the slow charger if you have the time to waste. Although its not much better. You wont notice a difference without some fancy capacity measuring equipment. A 2 month old battery used daily is already worse than 5 percent down usually.