How trick "smart" charger that's not so smart?

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chris falk
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How trick "smart" charger that's not so smart?

Often when I return from even a big ride with my SLA batteries exhausted, when I plug in the so called smart charger that came with the scooter, it shows the batteries as fully charged. I figured out that I could trick it into going into the charge mode if I lifted the rear end of the scooter and gave it full throttle with the charger plugged in. I guess this put enough of a load on the battery pack to drop the voltage down to where the charger realizes that it needs to go into charge mode. I'm switching out to a 48 volt controller with 60 volts of batteries running through it that I planned on charging with my current 36 volt charger on three of them and a 24 volt charger on the remaining two (since I can't find a 60 volt charger). The problem being that I won't be able to use this trick since I'll have the battery bank split into two pieces neither of which can run the scooter. Is there a simple way that I can load the parts of the battery bank and get the charger to work? I'll start another thread about possible other ways to charge a battery bank of this size.

reikiman
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Re: How trick "smart" charger that's not so smart?

This sounds like a stupid charger. Get Soneils.

- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
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Tireiron55
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Re: How trick "smart" charger that's not so smart?

Did you use a toggle switch when charge them? I'm thinking about paralleling my battery pack and I'm wondering if I need toggle switches. I already have the same set up you do. Using a 36v and 24v charger. I'm afraid that I'll blow the chargers if I don't use a switch.

I bent my wheel, broke my trans, and blew my motor. Now I cry a lot.

reikiman
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Re: How trick "smart" charger that's not so smart?

Huh? Switch? Uh? I've been doing this kinda thing for years w/o problem. Not just on this bike but also my EVT 4000. What kind of switch are you thinking of?

- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
- Electrified Electra To

boyelectric
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Re: How trick "smart" charger that's not so smart?

Do you mean a switch to isolate a 24v cell and a 36v from each other while charging up?

chris falk
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Re: How trick "smart" charger that's not so smart?

Yes boyelectric, Tireiron55 and I thought there might be a need for switch or some other way to split the battery bank into a 36v portion to be charged by the 36v charger and a 24v portion to be charged by the 24v charger with no connection between the two during charging. Rekimann, are you saying that I can leave batteries 1 thru 5 connected in series and I can connect the leads from the 36v charger to the positive terminal of battery 1 and the negative terminal of battery 3 while also connecting the leads of the 24v charger to the positive terminal of battery 4 and the negative terminal of battery 5 and I won't damage either of the chargers or the batteries?

I'd welcome this news, but I don't want to risk blowing out a charger or starting a fire because I didn't fully understand the ramifications of what I was doing. For example, I thought it seemed reasonable to split the leads of a 12v charger and charge multiple batteries in parallel, but now I'm reading that may well work, but it could also cause serious overcharging of some of the batteries. I don't want to make a similar mistake in my thinking here.

Experts, chime in please.

Tireiron55
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Re: How trick "smart" charger that's not so smart?

I didn't know it was bad to use one 12v charger. I've got a nice 12v charger with 2, 10, and 50 amp settings. It probably wouldn't be a great idea to use it. I thought maybe if I paralleled to all 5 batteries, I could use the 50amp setting. That would charge fast.

I bent my wheel, broke my trans, and blew my motor. Now I cry a lot.

sparc5
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Re: How trick "smart" charger that's not so smart?

That would work, just make sure the batteries aren't wired in series but in parallel when you do it.

XM-3000...
-DC-DC converter replaced with a Dell D220P-01 power supply.
-72V mod
-Expensive bank charger until I come up with something better... Still trying.
-

chris falk
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Re: How trick "smart" charger that's not so smart?

I didn't know it was bad to use one 12v charger. I've got a nice 12v charger with 2, 10, and 50 amp settings. It probably wouldn't be a great idea to use it. I thought maybe if I paralleled to all 5 batteries, I could use the 50amp setting. That would charge fast.

If I remember correctly, I think that one of the problems that was mentioned was that as the various batteries in the pack reach full charge and start to drop offline, your charger is still putting out the full 50 amps through fewer and fewer bateries. Thus the last batteries to reach full charge are being subjected to a lot more charging amps than they ought to be. Of course, I suppose you could avoid this by setting the charger down to an amp setting that wouldn't be too much for a single battery, but then your charging rate would be insanely slow since it would start out as having this low amperage split among five batteries. Sound right or am I missing something basic? I've only been reading the forum for the last two months, so I'm hear to learn.

Tireiron55
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Re: How trick "smart" charger that's not so smart?

Charging 5 batteries at 50amps total is 10amp a piece in parallel. That's a little high. But I didn't know that one could take more than 10amp at a time.

I bent my wheel, broke my trans, and blew my motor. Now I cry a lot.

sparc5
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Re: How trick "smart" charger that's not so smart?

The overcharging problem is a problem with string charges, not with batteries in parallel. Batteries in parallel self equalize. Voltage on higher batteries will cause current to flow into the batteries with lower voltages. At no time should you have an overvolt condition. If you had a bad cell in one battery, it's another story. Say you lost 1 cell in a battery due to a short, that would give you a 10V battery in a bank of 12V. I can't tell you what happens in this case, but I'm sure it's not good. :-)

Batteries in series have a serious overcharging problem because your weakest battery becomes charged the first, but it doesn't raise the volts enough on the string to tell the charger to quit, so gets overcharged until the charger quits. Inversely if you had a very good battery in a string of weaker batteries, the charger would quit before the strong battery is fully charged.

XM-3000...
-DC-DC converter replaced with a Dell D220P-01 power supply.
-72V mod
-Expensive bank charger until I come up with something better... Still trying.
-

chris falk
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Re: How trick "smart" charger that's not so smart?

Thanks for correcting me, sparc5. I've been reading a lot of the back posts trying to learn the basics and I got confused. I think maybe what I had actually read about parallel charging was the situation you brought brought up with a battery in the pack that goes bad and loses a cell and that this would cause all of the current to go to this battery which in turn could cause it to overheat and possibly even burst.

If the above could happen with parallel charging and if the problems you point out could happen with series charging, I guess there's no safe, effective option but to put on some fancy diagnostics to monitor the charging or buy a 12v charger for each battery or a bank charger. Unfortunately, none of these seems very cheap. Is there another option that I'm not aware of?

Can you answer the question about what amps a charger that's going to charge a 12v 10ah battery should be rated at in order to effectively charge the battery in a manner that doesn't shorten the battery's life.

sparc5
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Re: How trick "smart" charger that's not so smart?

The rule of thumb says 1/4 the AHr rating. You really need to look at the manufacturers specs because each battery has a different personality, gell type lead acid being the most fussy flooded lead acid being the least. http://www.smartgauge.co.uk/sga_faq.html#never has some good info. Someone above recommended 1/5th the AHr rating, if you do that you're really in the safe zone for any type. There is also temperature considerations for setting the volts right.

I suppose you could use a fuse (DC rated a little above your max charging rate) between each each battery to prevent the dumping of current into a broken battery cheaply.

Or you could wait about 3 months, and I'll have a computerized charger that is great for charging up to 6 batteries at once and give you lots of data, and programing options.

XM-3000...
-DC-DC converter replaced with a Dell D220P-01 power supply.
-72V mod
-Expensive bank charger until I come up with something better... Still trying.
-

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