Paralleling four small SLAs with four larger ones worth it?

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Old_Scoot
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Paralleling four small SLAs with four larger ones worth it?

I work at a large manufacturing plant and we have a dozen or so of those portable electrical defibrillator devices at our location. We change the batteries every year just to be safe. I have been given permission to take these 'spent' batteries home for reuse. They are 2.0 amp hour, 12v SLAs about the size of a largish laptop battery. Most (all?) have never been used and have been kept topped up by the (presumably smart) chargers in the defibrillator packs. I'm guessing they are still in pretty decent condition.

So my question is, would it worth connecting four of these in series for 48v and then placing them in parallel with my four 9ah SLAs in my X-500 scooter? Simple math would say this will give me about 20% more range. Or are these so small as to be not worth the effort and extra weight?

If I do use them, would it be better to have two independent circuits with a switch or just simply put the new pack in parallel with the existing one? If I do the latter, will I have any problems charging the whole mess at once with the stock 1.5ah charger? Thanks in advance for your advice.

Tim

x-500 scooter

x-500 scooter

x-500 scooter

x-500 scooter

x-500 scooter

x-500 scooter

x-500 scooter

sparc5
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Re: Paralleling four small SLAs with four larger ones worth it?

If its free, absoutely worth it. The only thing is they are probably not deep cycle. So get as many as you can so you only have to have a small depth of discharge.

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Old_Scoot
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Re: Paralleling four small SLAs with four larger ones worth it?

Yeah, they are free. I can't find much info on them, but yeah, I would agree that they are probably not a deep-cycle design given the intended application. So do think it is better running them separately then or connected in parallel with the larger bank? Won't the 1.5ah stock charger cook these things in short order?

Ken68
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Re: Paralleling four small SLAs with four larger ones worth it?

Here is a link to the same battery.

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2142

I bought 8 of them from a local store for $1.99 each. Wired up all 8 batteries up in a 4S2P for 48V at 4.6AH battery pack. Charged them up and they add a little range to the E-Bike. I keep them under my seat. But they do add an extra 14lbs to the weight of the E-Bike.

Ken Finch

Thanks,
Ken Finch

Old_Scoot
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Re: Paralleling four small SLAs with four larger ones worth it?

Yeah, the terminal arrangement is a bit different, but other than that it is about the same. How are you charging yours?

Ken68
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Re: Paralleling four small SLAs with four larger ones worth it?

I charge my pack using my Luyuan 48V 3A Smart Charger and it is working out fine.

Ken Finch

Thanks,
Ken Finch

reikiman
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Re: Paralleling four small SLAs with four larger ones worth it?

I suggest paralleling batteries rather than packs.

What I mean is to parallel at the 12v level rather than constructing a pack of 48v and paralleling that with the existing 48v pack.

This is called a "buddy-pair" arrangement. The reasoning is each battery in the "pair" helps each other to maintain pack voltage.

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Old_Scoot
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Re: Paralleling four small SLAs with four larger ones worth it?

Interesting idea. Thanks for the input. Does make wiring a bit more complex since I am looking at mounting these in an external pack.

The problem I am dealing with right now is the attaching wires to the terminals. They aren't standard lugs, just pads like the on your cell phone battery (only larger). My 15 soldering iron definitely won't cut it. Maybe one of those pencil type butane torches.

Ken68
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Re: Paralleling four small SLAs with four larger ones worth it?

Do not use a butane torch. The high temperature of the flame will damage the battery casing and the high heat generated on the tab will travel down to the lead frame inside the battery and melt the lead thus destroying the battery cell that tab is connected to. I used a Weller 35watt pencil iron to solder my 18 gauge wiring to the tabs on each of the batteries.

Ken Finch

Thanks,
Ken Finch

Old_Scoot
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Re: Paralleling four small SLAs with four larger ones worth it?

Are you really just trading lower heat for longer time? Mightn't getting in and out quickly with a torch pump fewer BTUs into the battery at the end of the job. These tabs lay down flush with the battery casing which seems to really wick away the heat.

Ken68
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Re: Paralleling four small SLAs with four larger ones worth it?

Well I was warning out of personal experiance. I used a butane torch myself and ended up scorching the battery case from the flame flowing out and around the tab. And after I soldered the 18 gauge wire to the tabs the battery was no longer putting out 12v but was putting out 8.5v. This was a brand new freshly charged battery that was outputting 13.8v before I had soldered the tabs. I unsoldered the battery, recharged it. During the recharge my Canadian Tire 1.5A Smart charger then began flashing its fault LED stating that there was a battery fault and then the charger shut down the charging process. I went and bought a replacement battery and soldered it up with my trusty 35watt Weller Pencil Iron and the completed pack was then functioning fine after that as a secondary battery.

Thanks,
Ken Finch

Old_Scoot
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Re: Paralleling four small SLAs with four larger ones worth it?

Well that is good enough for me. Thanks for the tip.

Ken68
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Re: Paralleling four small SLAs with four larger ones worth it?

Your welcome.

Thanks,
Ken Finch

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