AGM Charging profile

[martin007]

If the batteries were old, after a long time at 0.00 it would start to rise again...
Don't worry.

[Burgerman]

Yes if it really isnt needed. But you must be sure its 101% charged.

Also, one of the reasons I use bench power supplies at 40A and 50A for charging is that it allows me to do regular boosts during the day as I check mail or watch TV or eat. This lowers the average depth of discharge even if you are very active. This extends service life from a typical 9 to 10 months (in my case) to 3 or 4 years. Makes a massive difference. Lead batteries like to be full. Hate to be deeply discharged...

So a quick half hour at 50A sticks 25Ah back in. So good to go out again in the evening to the pub! And does so while helping the battery.

[wes4dbt]

I know the IP65 is only 8amp but even 8amps isn't used much. On a normal day, when I first plug in the chair it may go to 8amps in Bulk mode for a few seconds then to absorption. The amps starts start dropping fairly quickly down to @ 2amps.

Yesterday I hardly used my power chair, maybe .5 miles. Plugged it in at night and was on the charger for 9hrs (absorption is set for 8hrs), when I checked it, it was on float drawing .4ams.

[Burgerman]

I dont know how you use so little! I can use 25Ah and lose a bunch of lights just indoors cleaning etc. I can easily eat 40Ah in a day and thats as much as a set of 74Ah lead bricks gives you before a chair suddenly loses lots of lights and stops...

Maybe you should charge a full 8h CV and then float etc for as long as possible once a week, and just do a short 3 or 4 hour CV the rest of the time. That will still keep sulfation down.
Are you light?
What do you do all day?

Rear drive chairs like mine do use more when turning in place, or driving along a cambered road edge for e.g, a lot more. And adding a heavy weight user can double this Ah consumption. Its not really flat surface and straight line stuff that eats batteries. Its hard instant programming, heavy users, lots of left/right turning etc. And carpets, fat low pressure tyres and hills...

My chair hasnt left the house/driveway today. Too cold/windy... But its been at 25A for well over an hour already putting back around 28Ah so far. I have been pretty busy though with carpets and leaf blower etc.

[wes4dbt]

I'm not light @ 160lbs. I got mainly tile floors, some carpet but it's like indoor/outdoor with no padding. I made my house pretty easy to roll in because I used a manual chair indoors until recently.

I don't know how far I go on a daily basis. I'm curious now, I'll have to check. My guess is maybe 1 or 2 miles a day.

[martin007]

With 25 ah (and 160 lb) you won't get very far.

[Burgerman]

Use a phone GPS app. Its not really distance that eats batteries though. Its load. Turning, ramps, hills, road camber etc.

Heres an 88 mile GPS track from expresso in new york! With a sore bum.

Damn I cant find it.

And I think snaker in vietnam beat him.

[martin007]

Driving at a lower speed than the maximum allows you to travel more distance...

[wes4dbt]

Use a phone GPS app. Its not really distance that eats batteries though. Its load. Turning, ramps, hills, road camber etc.

Heres an 88 mile GPS track from expresso in new york! With a sore bum.

Damn I cant find it.

And I think snaker in vietnam beat him.

I do a lot of turning because my kitchen is narrow and I do a lot of cooking. But it's tile so not to much load. Also, one of the reasons I went with this chair is it has 5" casters, very maneuverable, turns easily. I got a Permobil M3 that I don't use except for emergencies or to go to the dentist. It has big fat 7" (more like 8") casters, sucks for inside the house. This chair is much lighter than the Permobil so that probably helps. I weigh the same in either chair. lol

[Burgerman]

The very fact that it is centre drive means it takes far less current to turn in place compared to a front or rear drive chair. They can in fact get away with a lower power controller system too. But personally its way too many wheels taking out peoples feet behind you in a busy pub or trying to damage my spine on the way there...

Quite hard to do since I broke it already and paralysed for 25 years. But it sets off muscle tension/spasm too.

[wes4dbt]

This is off topic but it seems like a simple question and doesn't really need its own thread.

What AWG size wire is required for a 24v, 8amp charger?

[Burgerman]

I dont really do awg but work in sqmm.

Thats super easy. 10sqmm is good for 100A. 8sqmm for 80A and so 1sqmm is good for 10A. But these are maximums. If you take more they get hotter. OK on silicone wires. So if you want less energy wasted and less voltage drom then double the cross section. Bigger never hurts. I would use 1.5sqmm cable.

[LROBBINS]

AWG 16 is 1.3 mm^2

[Burgerman]

Is adequate, next size up better!

[Burgerman]

Do you have an adjustable power supply?
Set to 14.4V and set 500mA (1/2 A) leave connected till current drops to practically nothing. Not more than say 12 hours. Then if looking good set to 13.6V and leave for a couple of days set to max of 250mA.

[wes4dbt]

AWG 16 is 1.3 mm^2

Just to be clear, your saying 16AWG is safe to use on a 8amp charger?

The reason I sound confused is because I tried looking this info up first but got mixed results.

One chart I looked at listed 16 awg rating at,

22amp for "Maximum amps for chassis wiring"

and

3.7amp for "maximum for power transmission"

Quite different numbers.

[wes4dbt]

Do you have an adjustable power supply?
Set to 14.4V and set 500mA (1/2 A) leave connected till current drops to practically nothing. Not more than say 12 hours. Then if looking good set to 13.6V and leave for a couple of days set to max of 250mA.

Not sure what question your answering.

But I can't set the amps, just the voltage.

[Burgerman]

That was a reply to someone else. My mind is a mess and slightly delerious and confused with bladder infection!

The amount of current a cable can take depends on many things. If it is permanant and can burn a house down then it needs to stay at ow temperature so that the insulation doesent deteriorate over time. And that is cheap insulation, and worse its normally twin or twin and earth which gives it more insulation. Also its frequently bundled together and insulating PVC and bundles of cable all get hotter. Theres also the fact that the thinner the cable the greater the voltage drop. So that also means that long cable lengths need to be thicker.

Then theres the types of cable. Some are low tempertature PVC and some that can carry much much higher current are silicone such as used by model planes etc. They can get 4 or 5 times as hot and funcion fine as silicone doesent melt. And the lenghts are small so voltage drop is no problem.

There IS no "correct" figure.

So in the case of an 8A DC charger with a wire in free air, where it cools well (not in a wall, floor etc) in a short lengh then a 1mm cable will get just detectably warm. And be safe. So I would use 1.5sqmm as its slight overkill, physically stronger and electrically has a little overhead. And less voltage drop.

[wes4dbt]

From the conversion charts I've seen. 16awg = 1.5mm2

The reason I'm sort of stuck on 16awg is that seems to be the largest gauge premade XLR with cable I can find. I was surprise that just about all you can find is audio cables. In the past I've just cut the XLR cable off a couple of old chargers I had. But I'm out of old chargers. lol

I do realize you can make your own but I would prefer to find a premade if possible.

[Burgerman]

I doubt you will. They are primarily audio cables.

[wes4dbt]

Is there any reason why I can't use a 16awg audio cable?

[Burgerman]

Well it depends. If its a microphone cable it will be a screened cable without room or need for a 16g cable. So not sure if its described properly. If so then probably.

Soldering a cable is super easy though and cheaper too.

If you care about longevity use genuine Neutrik https://www.neutrik.co.uk/product/nc3mxx
Good for 16A max. So no burning or overheating melting socket (hello permobil!)

[thetascott]

Found this. Never bought from them... https://www.powerstream.com/xlr-cable.htm . Just need to cut off the ring terminals.

[Burgerman]

Yes.
It spends time at this elevated voltage charging considerably faster than it does at float voltage. Thats why its use in cyclic operation or you would never get it done in 2 days.

But while at this voltage several things happen.
1. It creates oxygen and hydrogen, more at a high CV and less at a lower one. This is recombined back into water as long as current is low. But it produces some heat.
2. It causes excess positive plate corrosion...

So the perfect CV stage would be at the manufacturers mid CV voltage range corrected for temp. And it should end when on a typical chair sized battery current falls to 1000thC or a bit more if not super healthy so 500thC. Remember to include the chairs OFF current draw. Usually very low at under 15mA. In the event the battery wont drop this low after 8 hours @ CV stage it should terminate CV.
On a certain battery or type, and they do vary some, then charge should end and go to float when the battery current fails to fall by 0.1A over a 1 hour period.
Some batteries that are a little sulphated or that have never been charged "fully" (properly) can actually begin to rise again. If so stop.

If an AGM battery reaches 8 hours CV after a typical days use and or terminates at or close to 1000th to 500thC i actally is full. At this point the fastest cyclic charge proper charge has been achieved. If its nearly full anyway, then do a shorter CV and it will get to say 500thC faster anyway.

If you use one of the multitude of mobility chargers god only knows what it will do. I have many. They all baffle me. But one thing they never do is a full charge. They will turn off CV (which can seemingly be all kinds of unstable voltages) about 4 hours too soon. Probably because they are terrified of getting one that runs away, smells terrible and melts the casing. That can happen with batteries long past sell by date... And then they rely on a too high float level of 13.8V to finish the charge. It will, but that takes a long time.

[wes4dbt]

Yes.
It spends time at this elevated voltage charging considerably faster than it does at float voltage. Thats why its use in cyclic operation or you would never get it done in 2 days.

But while at this voltage several things happen.
1. It creates oxygen and hydrogen, more at a high CV and less at a lower one. This is recombined back into water as long as current is low. But it produces some heat.
2. It causes excess positive plate corrosion...

So the perfect CV stage would be at the manufacturers mid CV voltage range corrected for temp. And it should end when on a typical chair sized battery current falls to 1000thC or a bit more if not super healthy so 500thC. Remember to include the chairs OFF current draw. Usually very low at under 15mA. In the event the battery wont drop this low after 8 hours @ CV stage it should terminate CV.
On a certain battery or type, and they do vary some, then charge should end and go to float when the battery current fails to fall by 0.1A over a 1 hour period.
Some batteries that are a little sulphated or that have never been charged "fully" (properly) can actually begin to rise again. If so stop.

If an AGM battery reaches 8 hours CV after a typical days use and or terminates at or close to 1000th to 500thC i actally is full. At this point the fastest cyclic charge proper charge has been achieved. If its nearly full anyway, then do a shorter CV and it will get to say 500thC faster anyway.

If you use one of the multitude of mobility chargers god only knows what it will do. I have many. They all baffle me. But one thing they never do is a full charge. They will turn off CV (which can seemingly be all kinds of unstable voltages) about 4 hours too soon. Probably because they are terrified of getting one that runs away, smells terrible and melts the casing. That can happen with batteries long past sell by date... And then they rely on a too high float level of 13.8V to finish the charge. It will, but that takes a long time.

You answering a different post or did I miss something?

[wes4dbt]

Found this. Never bought from them... https://www.powerstream.com/xlr-cable.htm . Just need to cut off the ring terminals.

Thanks very much, this seems to be exactly what I've been looking for. Don't know how you found it, I ran out of phrases to Google. lol

[Burgerman]

Yes I am! Brain still very confused!

Bladder infection is going away!

Now all I need t do is repost it when I can find where it was supposed to be.

[Dan]

Found this. Never bought from them... https://www.powerstream.com/xlr-cable.htm . Just need to cut off the ring terminals.

Thanks very much, this seems to be exactly what I've been looking for. Don't know how you found it, I ran out of phrases to Google. lol

Hes another one on aliexpress that looks okish
https://www.aliexpress.com/item/1005005080969756.html

[Burgerman]

If you care about longevity use genuine Neutrik https://www.neutrik.co.uk/product/nc3mxx
Good for 16A max. So no burning or overheating melting socket (hello permobil!)

Try to get qualiy original connector. Permobil already managed to wreck lots of CJSM2 joysticks by shipping chargers with cheaper pattern connectors. It wasnt pretty. Had to do a recall.

[wes4dbt]

Hes another one on aliexpress that looks okish

That's an amazing price but I couldn't find the cord length or wire gauge.