Below are three different charging methods for a scooter.
Fig. 1 shows the conventional method where the batteries are charged in series
with a single charger.

Fig. 2 shows a series charging method using two 12V chargers. Are there any issue you foresee with this method?

Fig. 3 shows an ideal charging method with two 12V chargers each charging a
single battery. A switch would be used to allow this configuration.

I guess my question is, would you think there would be any issue with the chargers and the motor controller if left directly connected, 110V disconnected of course. In other words I'd like to use the two 12V chargers
as on-board devices just as the single 24V charger is now.

Your expert thoughts and recommendations are appreciated!

 

Didn't think this inquiry would be so Taboo!

 

i try to shy away from charging batteries in series due to inbalances. due to age/use internal cells in batteries may "wear out" and the batteries could charge at different rates. when i need to i always charge them in parallel. so i think your best bet is to use option 3 and charge them independantly

 

i try to shy away from charging batteries in series due to inbalances. due to age/use internal cells in batteries may "wear out" and the batteries could charge at different rates. when i need to i always charge them in parallel. so i think your best bet is to use option 3 and charge them independantly

Well, your thoughts are mine verbatim. My question really is do you think there there would be and adverse issues with the motor controller?

Thanks

 

well if is connected exactly how you show in fig 3 with each battery independant of the other, the charger would be in parallel with the battery so i dont see any problem there. but try to see if you can find the specs on the controller and possibly a schematic to be sure

 

Good luck on getting schematics to your controller. They'll be proprietary. The maker of the scooter is only going to recommend one charging method for the batteries; the way they had it configured when it left the factory.

If you charge the batteries in series, and the state of charge of the batteries are different, or one of the batteries has less AH capacity due to age or other reasons, you'll wind up overcharging one of the batteries.

If you charge each battery with separate chargers, but the batteries remain connected in series, the controller won't see any difference between that configuration and series charging.

 

Good luck on getting schematics to your controller. They'll be proprietary. The maker of the scooter is only going to recommend one charging method for the batteries; the way they had it configured when it left the factory.

Indeed, I know better even to try.

If you charge the batteries in series, and the state of charge of the batteries are different, or one of the batteries has less AH capacity due to age or other reasons, you'll wind up overcharging one of the batteries.

Yes, I know this too, which is really the reason for the thread.

If you charge each battery with separate chargers, but the batteries remain connected in series, the controller won't see any difference between that configuration and series charging.

I take it this is referring to figure 2.

Figure 3, on the other hand, the configuration I am most interested in is a disconnect of the series configuration with the switch I drew in the drawing.

There are 4 wires from the controller for battery connection, two for one battery and two for the other one. But once inside the controller I came to realize that there really were only three wires. the third wire was essentially a wire from the + of one battery to the - of the other battery. This wire I am confident will not cause any issue.

Now the assumptions come into play. I am assuming that you can not charge the battery while the power key is in the on position. I probably can verify this assumption in no time. If this is the case then applying voltage via the chargers is like a shortcut to the batteries...bypassing the controller. If the key switch is on, I might make another assumption....that any voltage from a charger is NOT connected to the controller, but the batteries are.

I think this may be the way I could diagnose the potential for using a dual single charge schema.

what do you think? Do I have faulty logic here?

 

Now the assumptions come into play. I am assuming that you can not charge the battery while the power key is in the on position. I probably can verify this assumption in no time. If this is the case then applying voltage via the chargers is like a shortcut to the batteries...bypassing the controller. If the key switch is on, I might make another assumption....that any voltage from a charger is NOT connected to the controller, but the batteries are.

Well, while the scooter is off (Power Key Removed) plugging in the charger lights two LED's, a red LED for power indication and a yellow LED for charging indication. The Yellow turns green when the batteries are charged.

Now my assumption was that if the Power Key was inserted and on, the charger LED indicators would not be lit as the charger would be disconnected from the controller circuit. Such is not the case. Seems that it would make sense to have this feature, wouldn't want to drive away with the scooter plugged into the wall. There is still the option of adding a relay to disengage the charging connection to the motor controller, thus isolating both the series connection and the controller/charger connections.

Now that I think more about it, it is also possible that plugging power to the charger would always present me with at least the red power LED. The Yellow charging LED may also com on but never go green with the scooter power key on. Another test... Yeeks!

Test Results:
The charger LED indicators said that the batteries were charged. RED/Green.
With the charger power disconnected I turned on the scooter...scooter moves.
With the scooter power key on I plugged in the charger power and the Red/Green LED's were displayed.
Scooter did not move. So it is obvious that the charger is connected to the batteries at all times, but yet the controller knows that the charger power is on and does not allow the scooter to function.

 

I have recently witnessed two ebikes with totally destroyed and swollen 12V 12AH batteries as a result of overcharging. Each ebike is powered by a 48V battery pack of four batteries in series. So now I have eight bloated batteries. I don't know what kind of hazard would have resulted if the batteries were left on charge unattended.
The batteries are charged in series. I do not know how to resolve this problem except to open the battery pack and charge each battery individually.

 

I have recently witnessed two ebikes with totally destroyed and swollen 12V 12AH batteries as a result of overcharging. Each ebike is powered by a 48V battery pack of four batteries in series. So now I have eight bloated batteries. I don't know what kind of hazard would have resulted if the batteries were left on charge unattended.
The batteries are charged in series. I do not know how to resolve this problem except to open the battery pack and charge each battery individually.

Exactly my thoughts for opening this thread. Other than cost, I'd like to understand the manufacturer's reasoning for designing Mobility scooters and e-bikes. With respect to mobility scooter's they do build in a host of safety features, but in the end avoid dealing with the battery issue. In both our cases, we are stuck disassembling half the scooter/bike even to check the battery condition, let alone charging the batteries safely. And with me and this mobility scooter, taking the chair off, taking the cover off, disconnecting the batteries and connecting the charger is more work that causes more pain and fatigue.

I believe that if I can rig the power key on my scooter to trigger a relay that
1) disconnects the series configuration and
2) Disconnects the controller from the batteries I can then proceed to plug the
charger power to the scooter and charge the scooter safely.

Ideas are greatly appreciated!

 

Well, this latest experiment seals my commitment to switching to single battery chargeing methods.

I took a bit of a ride today on my scooter, with my dog in the lead looking like an anorexic reindeer pulling me forwards. A couple of kids yelled out, "how does that run?" Being a wise-ass I yelled back, "My dog is pulling me!"

"Yeah right!," I get back from one of them.

At the end of the ride I usually plug in the charger and head indoors.
This time I did a bit of measurements.

_________Start V___After 40min___After 1hr
Bat. (A)__12.98V____14.86V______14.98V
Bat. (B)__13.03V____14.72V______14.70V
Tot._____26.10V____29.68V______29.68V

The charger will charge at 3A during the Bulk charge phase till the total voltage gets to
xx.xxV (I don't know...didn't wait to find out....I unplugged the charger as, in my opinion, both batteries were higher that their bulk voltage specifications. Not only that, but Bat. A was loosing charge and Bat. B was still gaining, thus the difference between them was increasing and both were being overcharged.
After a couple of unplugs and plugins the charger settled in its second charge state of x.xA at 13.xxV. If this isn't sufficient evidence and cause to switch to the single battery charging method, then I wouldn't know where to go for quality Battery charging. I have been allowing the charger to charge my two batteries in the above fashion for a few months now and they would certainly have dies a quick death if I hadn't done this test.
Bat. B had 2.497V/cell. Not good!

 

At the local Vietnam War Museum, we have a truck known informally as a "5-ton":

The gentleman on the left is "Big Al", the gent on the right is Rusty.

Anyway, this vehicle has four very large 6TMF 12v batteries wired in series-parallel. These batteries are about twice the size of a typical car battery.

One of the batteries developed a shorted cell, and I told the members to leave that pair of batteries disconnected until a replacement could be afforded for the bad battery.

I was not listened to, and someone kept reconnecting the "bad" side.

This resulted in the one GOOD battery in series with the shorted cell being severely overcharged when the vehicle was running, and when the vehicle was off, the two GOOD batteries in parallel with the "bad" pair were discharged to the point where sulfation was taking place.

Instead of having to purchase just one battery, they had to purchase an entire set. At $150 per battery, that was a considerable expense.

 

Here's what overcharged looks like:

Now I have eight of these.
One of these days I'm going to build me an individual battery charger so this doesn't happen again.

 

Here's what overcharged looks like:

Now I have eight of these.
One of these days I'm going to build me an individual battery charger so this doesn't happen again.

Ouch! I don't even want to look at the picture without safety armor on!


This morning, after a night of "disconected-ness" from chargers I used individual chargers made by the same manufacturer of the batteries and specific for use with said batteries. They immediately began in bulk charge mode. I expected them to switch to maintenance mode fairly quickly, but they did not, so I connected the multi-meter to one of the batteries. The terminal voltage was 14.52V and rising. It was reaching 14.7xV and had not switched to maintenance mode. I asked Why is this happening as the mfg. spec reads 14.6V.

Then, perhaps, an LED went on in my head and the ambient temperature came into play. But I'm not sure if either charger has temperature compensation.

But if the did, would that explain a bulk charge voltage as high as 14.98V at 50 F?
I took readings every 15 minutes till the float was stable.

I believe this graph is for Lead Acid and not AGM, which is what my batteries are. In this case I would expect hope to stay closer to the lower side of each range.
But again I don't think my charger is temperature compensated. there is no ambient temperature sensor on the charger or no sensor on the battery clips. How would it know temperature otherwise? Or does the charger sense the current(I) rate and know that it is not fully charged? Based on the chart and the ambient temperature the day I was monitoring, the bulk charge voltage was really not wrong, but almost dead on. Then why would one batteries voltage be climbing and the other decreasing??? Would like to understand these questions.


A New Test: Separate 12V Battery chargers designed for the batteries.

Perhaps tomorrow I will run the same test with the batteries inside at 68 Deg F.

 

Another question:

In the above charge example I charged the two batteries with two separate chargers but left the batteries in their series configuration, thus the positive terminal of one charger was tied to the negative terminal of the other charger. The individual batteries did act and respond as if being charged individually, so does the it matter that they were still in a series config and that the charger were interwoven as well??

 

This morning, after a night of "disconected-ness" from chargers I used individual chargers made by the same manufacturer of the batteries and specific for use with said batteries. They immediately began in bulk charge mode. I expected them to switch to maintenance mode fairly quickly, but they did not, so I connected the multi-meter to one of the batteries. The terminal voltage was 14.52V and rising. It was reaching 14.7xV and had not switched to maintenance mode. I asked Why is this happening as the mfg. spec reads 14.6V.

Then, perhaps, an LED went on in my head and the ambient temperature came into play. But I'm not sure if either charger has temperature compensation.

But if the did, would that explain a bulk charge voltage as high as 14.98V at 50 F?

Yes, it would indeed explain the higher bulk charge.

I took readings every 15 minutes till the float was stable.

I believe this graph is for Lead Acid and not AGM, which is what my batteries are. In this case I would expect hope to stay closer to the lower side of each range.

Not really, you want the middle of the range.

But again I don't think my charger is temperature compensated. there is no ambient temperature sensor on the charger or no sensor on the battery clips. How would it know temperature otherwise? Or does the charger sense the current(I) rate and know that it is not fully charged?

You have not posted the manufacturer and model # of the charger, nor a link to the manual, so how would we know?

Based on the chart and the ambient temperature the day I was monitoring, the bulk charge voltage was really not wrong, but almost dead on. Then why would one batteries voltage be climbing and the other decreasing??? Would like to understand these questions.

I would say that from the plots below, either battery [A] is on its' way out, or it had been charged more than battery before you started the charge cycle. I believe the former is more likely.

Try exercising the battery; draining it to 12v using a dummy load (car headlamp is a good one), and recharging it repeatedly. Some people say to drain them deeply; I don't like to do that as it's pretty hard on them.

A New Test: Separate 12V Battery chargers designed for the batteries.

Perhaps tomorrow I will run the same test with the batteries inside at 68 Deg F.[/QUOTE]

Let the battery temperature stabilize for a couple of days. Batteries have a lot of mass, and can take a considerable amount of time to reach the temperature of their surroundings.

Read the temperature of the battery positive terminal to get a good idea of the actual internal temp.

If the charger is going by the ambient temperature rather than the positive terminal temp, it could be off considerably.

 

Another question:

In the above charge example I charged the two batteries with two separate chargers but left the batteries in their series configuration, thus the positive terminal of one charger was tied to the negative terminal of the other charger. The individual batteries did act and respond as if being charged individually, so does the it matter that they were still in a series config and that the charger were interwoven as well??

No, it doesn't.

 

One important thing with AGM type batteries, since there is no liquid in them watch the battery temperature. When they start to get hot they out gas through their vents and loose electrolyte. After loosing enough they will soon short internally and die.

 

The batteries(PS-12400 NB4):
http://www.power-sonic.com/images/powersonic/sla_batteries/ps_psg_series/12volt/PS-12400_11_Feb_21.pdf

The Charger(PSC-124000A-C):
http://www.power-sonic.com/images/p...ructions_for_AC-Series_chargers_11_Jan_12.pdf

The Charger is not temperature compensated. In other words charging them at 50 Deg F is fine, but charging them at 85 Deg F to 14.9V is not so good.



And, honestly, Given the potential differences in the individual chargers, this alone could account for the data plot differences.
And, of course, each battery's slight difference. The batteries have been kept side-by-side and have been charged at the same time either with the scooter's on-board 24V charger or the two separate Powersonic chargers. What caused the initial data differences Bat. (A) 14.7x and decreasing and Bat. (B) 14.98V and increasing is unknown, but they were both just exercised with a short scooter ride. Given their very short life, I would expect neither battery to have much for sulfation. They were kept at or near float charge and probably never saw less than 12.6V during operation. As you can see by the battery voltages before charging, they were both at or near 13.0V after a scooter ride. Even so they do get a good workout going up a hill near my home.