3 1000Ah 3.2 volt batteries in series internally

[ClinicalScientist]

Hello guys. Looking for some advice before I make an explosive mistake. I picked up these older Winston 1000Ah 3.2 volt cells for $200. Seemed like a good deal. My intention was to wire them in series to make 24 volts with the assumption that each terminal pair was a separate confined cell. Turns out that’s not quite the case. There are separate cathodes and anodes, but upon disassembly I found they share electrolyte fluid for all “cells” in each battery. Can I make a 8s3p battery out of these?

 

[stok]

nope, its one cell with 9 sets of terminals to increase the amperage that can be drawn from the cell.

 

[meetyg]

Maybe you can still make use of them, with DC-DC boost converter.

For example, if you series the 3 cells, you will get a nominal voltage of 9.6v.

Then you can connect one (or more, in parallel) of these step up converters to get to 12v or 24v.

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I also have 2 of these, one is 1200w and the other 1800w. I use them here and there but haven't had the chance or need to stress test them.

I think you can safely output 20A from each one.

 

[ClinicalScientist]

nope, its one cell with 9 sets of terminals to increase the amperage that can be drawn from the cell.

Thank you for the reply. That’s what my gut told me. I did a very cautious “in series” check (with a fused line) and got my expected voltage, so I thought maybe it’s ok, but I better check to see if anyone has done this before. Thanks again! I’ll try a different route.

 

[ClinicalScientist]

Maybe you can still make use of them, with DC-DC boost converter.

For example, if you series the 3 cells, you will get a nominal voltage of 9.6v.

Then you can connect one (or more, in parallel) of these step up converters to get to 12v or 24v.

20.23US $ 26% OFF|1800w 40a Dc-dc Dc Constant Voltage Constant Current Boost Converter Boosts 10-60v By Fan For 12-90v Boost Power Module - Voltage Regulators/stabilizers - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

I also have 2 of these, one is 1200w and the other 1800w. I use them here and there but haven't had the chance or need to stress test them.

I think you can safely output 20A from each one.

Thanks for the input! I briefly researched running some dc to dc boost converters in parallel and got discouraged by the Amazon price, but I could wait a couple of weeks for some from AliExpress. I’ll need a lower input than 10 volts. I found these:

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If I did run this setup I would have to solve another two problems that I can think of:

1) 10.95 volts out of my SCC to charge these batteries would max out my amps and be lower watts than I could get from a 24 volts setup. Could a solution be to parallel some step down converters?

2) these cheap pieces from AliExpress have no back feed protection. I’ve heard inverters have some that would fry these. Could a solution be running a capacitor between these and the inverter?

Thanks again! I’m glad someone else has seen these batteries. I may have some for sale if I can’t figure out what to do with them. Lol

 

[No Idea]

Could you build a 4th bank of different old 3.2v cells? For $200 for 3 already you are looking for a cheap and chearful way to use them so all the rules about matching cells doesnt matter if you just use them too far either side of nominal 12.8 voltage. Not much point spending unless you can capacity test the Winston cells first then pick more old batteries to get close to them. At least you can get a high amp charger on them if you can get to 12.8v.

 

[ClinicalScientist]

Could you build a 4th bank of different old 3.2v cells? For $200 for 3 already you are looking for a cheap and chearful way to use them so all the rules about matching cells doesnt matter if you just use them too far either side of nominal 12.8 voltage. Not much point spending unless you can capacity test the Winston cells first then pick more old batteries to get close to them. At least you can get a high amp charger on them if you can get to 12.8v.

That’s a great point. I should find a way to capacity tests these before I put too much effort into building a system around them.

 

[meetyg]

Thanks for the input! I briefly researched running some dc to dc boost converters in parallel and got discouraged by the Amazon price, but I could wait a couple of weeks for some from AliExpress. I’ll need a lower input than 10 volts. I found these:

US $2.15 4％ Off | DC 400W 15A Step-up Boost Converter Constant Current Power Supply LED Driver 8.5-50V to 10-60V Voltage Charger Step Up Module

2.04US $ 5% OFF|DC 400W 15A Step up Boost Converter Constant Current Power Supply LED Driver 8.5 50V to 10 60V Voltage Charger Step Up Module|Replacement Parts & Accessories| - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

a.aliexpress.com

If I did run this setup I would have to solve another two problems that I can think of:

1) 10.95 volts out of my SCC to charge these batteries would max out my amps and be lower watts than I could get from a 24 volts setup. Could a solution be to parallel some step down converters?

2) these cheap pieces from AliExpress have no back feed protection. I’ve heard inverters have some that would fry these. Could a solution be running a capacitor between these and the inverter?

Thanks again! I’m glad someone else has seen these batteries. I may have some for sale if I can’t figure out what to do with them. Lol

First, you should take the stated output of these cheap DC-DC converters with a grain if salt: Although they state 15A or 400w, that's maximum and will shorten their lifespan considerably. You should over-spec them according to your load needs. To be safe and run then fairly cool, I would take their rated output and treat it as if it were half of that.

As for inverters backfeeding, I'm not sure what you mean exactly. Inverters already have capacitors in them. This means that when connecting the inverter, you should use a pre-charge resistor, to avoid inrush current (which can possibly fry these cheap DC-DC converters).
If you are afraid of backfeed somehow, the solution would be using a diode between inverter and the DC-DC converter. There are some high power "ideal" diodes (with only a few mV voltage drop as opposed to 0.6v on standard diodes). Search for "ideal diode" on Ali and you will find them. Again you need to take their rated output amperage and size it to your needs using the 50% rule as above.

 

[ClinicalScientist]

First, you should take the stated output of these cheap DC-DC converters with a grain if salt: Although they state 15A or 400w, that's maximum and will shorten their lifespan considerably. You should over-spec them according to your load needs. To be safe and run then fairly cool, I would take their rated output and treat it as if it were half of that.

As for inverters backfeeding, I'm not sure what you mean exactly. Inverters already have capacitors in them. This means that when connecting the inverter, you should use a pre-charge resistor, to avoid inrush current (which can possibly fry these cheap DC-DC converters).
If you are afraid of backfeed somehow, the solution would be using a diode between inverter and the DC-DC converter. There are some high power "ideal" diodes (with only a few mV voltage drop as opposed to 0.6v on standard diodes). Search for "ideal diode" on Ali and you will find them. Again you need to take their rated output amperage and size it to your needs using the 50% rule as above.

Thank you for the input. I was planning to overspec by 20%, but I’ll keep it at 50% to be on the safe side. They’re not very expensive anyway. Might as well.

Yes, sorry. I was getting some facts mixed up. I was thinking about a diode to protect from backfeeding. Is that necessary?