Charging help....

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I just wanted to get some help/clarification for charging of SLA batteries. My xb600 stock 48V charger has an output voltage of 55.6V. Does that seem rather high? I thought 13.8V per battery was pretty much the max? Also, charging of batteries in series must give odd results if u use a voltmeter on the individual batteries while charging. While charging I get 2 batteries at like 15V and 2 at like 12V give or take a bit. My charger has not been shutting off on its own so I used a 12V charger to individually charge them hoping for better performance, we will see how that works out as I dont want to put the charger on overnight and possibly damage them.

What SHOULD be the output of a 48V, 60V and 12V chargers? Is this ODD voltage reading while charging in series normal?
I am very soon going to be re-wiring all my batteries with the Anderson powerpole setup, modified to an idea i have. I will post pics etc. of this once I do it. I have a 12V Schumacher charger I got at walmart. It has charging at 2A 4A and 6A. I was thinking that if I needed a quick charge I could rewire the Andersons for parallel and charge at 6A. I would normally use the 48V or 60V series chargers for normal charging, but use the 12V parallel for occasional balancing of the batteries.

Any info from very knowledgable people would be great, THX in advance.

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Dave ; Tennessee
XB-600.

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Re: Charging help....

sixpax2k9 wrote:

1. My xb600 stock 48V charger has an output voltage of 55.6V. Does that seem rather high?
2. I thought 13.8V per battery was pretty much the max?
3. Also, charging of batteries in series must give odd results if u use a voltmeter on the individual batteries while charging. While charging I get 2 batteries at like 15V and 2 at like 12V give or take a bit.
4. My charger has not been shutting off on its own so I used a 12V charger to individually charge them hoping for better performance, we will see how that works out as I dont want to put the charger on overnight and possibly damage them.
5. What SHOULD be the output of a 48V, 60V and 12V chargers?
6. Is this ODD voltage reading while charging in series normal?

1. 56.4 volts or a maximum of 14.5 volts per battery.
2. Anything above 15 volts is not advisable for this type of battery.
3. In order for the pack to be balanced, no individual battery should be more than a third of a volt higher or lower than any of the others.
4. That is the best thing to do. Once your pack is back to reporting uniform voltages you can continue using the 48 volt charger.
5. 48v charger: up to 58v
60v charger: up to 72v
12v charger: up to 14.5v
6. No

I'm currently considering installing one of these (with a toggle switch) per battery in the floorboard of my scooter so I can monitor the balance of my pack.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=260427320413

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Re: Charging help....

Modern chargers generally follow three stages:

  1. Constant current, where the voltage rises enough to establish the desired maximum charging current. Voltage will then rise until it gets to the maximum voltage, where
  2. Constant voltage stage, where current will be reduced as battery fills until current reaches 1/10 max value, then
  3. Taper voltage stage where voltage slowly drops until battery only accepts a very small current, then it reports charge complete.

My xb600 stock 48V charger has an output voltage of 55.6V. Does that seem rather high?

The maximum voltage I've seen with the stock Jiangsu Xin Hua "shortage" batteries is 14.6V / battery, or 58.4. With my Vector 2-6-10 charger, they stabilize at a float voltage of 13.4, or 53.6V for the pack.

While charging I get 2 batteries at like 15V and 2 at like 12V give or take a bit.

Sounds like an unbalanced pack. The damage is being done to the ones reading 15V, as they must pass current at their maximum voltage. A floodie would just gas, venting hydrogen and oxygen, but the SLA's theoretically have a limited ability to recombine the gasses back into water. (I've cut SLA's apart, and seen no mechanism for this.) If they must exceed that rate, they will permanently vent the gas, and eventually dry out.

For an unbalanced pack, parallel charging is even more important. I've been happy with my Parallel/series plug system:
http://visforvoltage.org/forum/4690-new-pack-wiring-geometry-quothummerquot
The actual wiring in the XB-600 pack looks like this:
http://i200.photobucket.com/albums/aa122/mf70/XB-600/P6210106.jpg
It doesn't interfere with use of the 48V charger as an "opportunity charger" on long trips.

I dont want to put the charger on overnight and possibly damage them.

If it is a good three-stage charger, it will terminate charge safely. As you have discovered, a 48V "stock" charger CANNOT balance a pack beyond the small amount of equalizing charge a SLA can accommodate. If there is enough difference in capacity, a pack charger will think it should be in constant Current stage even after some batteries have reached their full capacity and are gassing.

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Re: Charging help....

OK heres my update..... The reason I was getting the weird voltage reading while charging was because I was not switching to the true + and - of each battery, just was disregarding the - voltage report. When I used the correct polarity they report correctly. I guess thats cause of the electron flow while charging in series.

I charged all my batteries individually to about 13.9V then set them back into series. What I dont get is that my stock charger shows 55.6V with no load on it. When I put it on the pack it was charging the pack, I checked the pack voltage and it was at about 57.3V and it was still charging. Is there a way to open a charger to check and adjust the different voltage stages that it switches to a float current etc. and reports the pack fully charged and only sends the trickle current to the pack? I ask this because unless I am wrong should a 48V charger be at the cutoff point and switch to trickle current by the time the pack reaches 57V ???? I would really like to not damage the pack, but I dont want to have to worry about monitoring the charger all the time.

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Dave ; Tennessee
XB-600.

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Re: Charging help....

As I said above,"The maximum voltage I've seen with the stock Jiangsu Xin Hua "shortage" batteries is 14.6V / battery, or 58.4." 57 ain't there yet. You were seeing 55.xx with no load. A modern switching charger is very unpredictable under no-load conditions, and there is little you can learn from that measurement. It needs to "see" a battery before it will "make a decision" about what to do.

I don't blame you for being nervous. Because of the extremely poor cooling of the pack, in very hot conditions, normal charging profiles can overheat the batteries, leading to thermal runaway. You are doing the most important thing right now, monitoring voltage. If your charger gives you amp output, you have the other critical piece of info. If you are using the stock charger, the Kill-a-Watt power meter will monitor total current drain, and you will be able to follow the tapering power at the fixed voltage of stage two.

You will soon get a feel for how long it takes to recharge after an average ride.

There are chargers ("Zivan") that allow adjustment of the stages, but they cost as much as we paid for our scoots.

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Re: Charging help....

Since I've recently been on the subject of chargers and batteries on here...regarding my xb600...I'd like to know if this idea of putting a voltage indicator with a toggle switch to read the level of each battery has been installed by anyone? Seems that would be a good thing to have. Anybody done this yet? It seems to me rather than going to all the trouble to do the anderson pole thing for parallel charging you could just keep an eye on the state of each battery after charge, from time to time, and when one went astray then you could just open the pack and charge each battery separate with a 12 volt charger to get things back in balance. This would seem feasible to me if it's not real often the pack was getting way out of balance. Is this feasible in the real world on our xb600s or any of the 48 volt bikes?

Gus

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Gus

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Re: Charging help....

Lee Hart has come up with a simple circuit that lights an "idiot light" if a pack goes out of balance. http://www.evdl.org/pages/battbridge.html I haven't tried installing it; I've been happy with the parallel/serial plug installation. It really isn't hard to set up, and gives a number of advantages, as has been discussed.

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