Getting this SLAB to use in high power applications and projects - general SLAB questions

Thread Starter

-live wire-

Joined Dec 22, 2017
901
There are certain things that I would like to do, but due to not having a powerful power supply, cannot. My projects are often very limited by the power supplies I have lying around. You don't really find anything above 100 or 200 watts. I cannot really invest a huge amount of money and get a LBPS that serves my needs. And if I want something to be portable, I can maybe use a power bank for charging a phone, or some standard batteries, but nothing more powerful. And the capacity is often pretty low too.

So to be able to make more power hungry projects portable, and have access to very large amounts of power, getting a medium sized SLAB (sealed lead acid battery) seems worthwhile. The voltage may not be the most precise, and it would need to be recharged a lot. But typically you can get at least a few 10s of amps and 100s of watts out of it. I found this one on ebay that is 12V 18AH and can, allegedly, supply 10KW. I am highly skeptical of this, as that would be almost 1 kA! But maybe it is the peak power, pulsed for a small fraction of the second. Maybe there is a datasheet or something that states the actual continuous discharge.
https://www.ebay.com/itm/Mighty-Max-12V-18AH-SLA-Replacement-Battery-for-Powerland-10000-WATT-Generator/192081877461?hash=item2cb8f8d9d5:g:xzcAAOSwjDZYga3K

So do people think I could continuously discharge it at 100-200 amps? I would be happy with around 70-100 amps max for discharge. But I want a decent headroom (maxheadroom lol) so that I do not shorten the lifespan and have other issues. If people think there is no way I could actually continuously and safely discharge it at those currents, then some suggestions for other batteries would be great. I want at least 10 AH and 12V, and it should be under $40.

And once I have a decent SLAB, I still need a way to charge it. I looked around and the chargers are insanely expensive (a 10A one is almost $100)! So a DIY approach would probably be more effective. I do not want it to take more than a few hours to charge it from almost completely depleted to almost 100%. Less time is obviously ideal. I have heard some stuff on what is needed to charge it properly but do not know too much. I have just heard that you need a voltage higher than the nominal voltage and constant current for certain parts is ideal. I am considering getting this CC/CV buck converter and this SMPS. Then I can figure out the ideal voltages and currents later.
https://www.ebay.com/itm/24V-DC-15A-350W-Regulated-Switching-Power-Supply-Transformer-24-Volt/263703622296?hash=item3d65f5f298:g:xFQAAOSwrjZbA2xn
https://www.amazon.com/Aideepen-Constant-Current-Adjustable-Converter/dp/B0747QDRW9/ref=sr_1_1?ie=UTF8&qid=1527348156&sr=8-1&keywords=constant+current+constant+voltage+buck+converter
Would that work to charge them quickly and properly? And what does everyone recommend for voltages and currents here? I want optimal lifetime.

Also I try to avoid mains whenever possible. But given that almost all the power supplies require you to wire the mains yourself, I guess I will have to. But where would I get a mains cord for it, and what is the best way to avoid shorts and exposed wires here? Is heatshrink or something else required to ensure safety? Those screw terminals, especially with how close together they are, are making me nervous. I understand electrical safety and take all the necessary precautions, but do not really have any experience wiring mains.

I also need to have short circuit and over-discharge protection. I plan to be careful, but accidents do happen. And I am not going to be constantly measuring the voltage. So for overcurrent protection a fuse probably makes the most sense, as opposed to some sort of high current switch and shunt/hall. I want a fuse that can handle a few seconds of a little bit over the maximum current, or high inrush currents, but will blow if it is over by a little for more than a few seconds or by a lot for more than a fraction of a second. Or if there is some other resettable commercial option that is economical that would be nice. But I have heard that fuses are notorious for allowing overcurrent close to the max for many minutes. So what ratings do I look for in a fuse? What products do people suggest here?

For overdischarge, I plan to have a mosfet that turns an active buzzer with resistor on when the voltage is low enough. It should only consume a few 10s of mAs, and alert me to disconnect and start charging it. I will make sure to not leave it unattended. Is this a terrible idea, or will it be good enough for my purposes?

Then once I have all the equipment there is still the issue of the high current wiring. From what I have heard, screw terminals and think metal bars are commonly used for those types of connections, as opposed to soldering. Welding is more common if it needs to be permanent (like in a welding power supply). I do not really have the stuff to weld so I guess I will have to use other connectors. If someone could recommend some sort of pack that includes a lot of terminals and stuff, that would be great. Flexible welding wire seems like the best option here but I do not really know where to get it. Suggestions there would also be great.
 

Hymie

Joined Mar 30, 2018
741
There are certain things that I would like to do, but due to not having a powerful power supply, cannot. My projects are often very limited by the power supplies I have lying around. You don't really find anything above 100 or 200 watts. I cannot really invest a huge amount of money and get a LBPS that serves my needs. And if I want something to be portable, I can maybe use a power bank for charging a phone, or some standard batteries, but nothing more powerful. And the capacity is often pretty low too.

So to be able to make more power hungry projects portable, and have access to very large amounts of power, getting a medium sized SLAB (sealed lead acid battery) seems worthwhile. The voltage may not be the most precise, and it would need to be recharged a lot. But typically you can get at least a few 10s of amps and 100s of watts out of it. I found this one on ebay that is 12V 18AH and can, allegedly, supply 10KW. I am highly skeptical of this, as that would be almost 1 kA! But maybe it is the peak power, pulsed for a small fraction of the second. Maybe there is a datasheet or something that states the actual continuous discharge.
https://www.ebay.com/itm/Mighty-Max-12V-18AH-SLA-Replacement-Battery-for-Powerland-10000-WATT-Generator/192081877461?hash=item2cb8f8d9d5:g:xzcAAOSwjDZYga3K

So do people think I could continuously discharge it at 100-200 amps? I would be happy with around 70-100 amps max for discharge. But I want a decent headroom (maxheadroom lol) so that I do not shorten the lifespan and have other issues. If people think there is no way I could actually continuously and safely discharge it at those currents, then some suggestions for other batteries would be great. I want at least 10 AH and 12V, and it should be under $40.

And once I have a decent SLAB, I still need a way to charge it. I looked around and the chargers are insanely expensive (a 10A one is almost $100)! So a DIY approach would probably be more effective. I do not want it to take more than a few hours to charge it from almost completely depleted to almost 100%. Less time is obviously ideal. I have heard some stuff on what is needed to charge it properly but do not know too much. I have just heard that you need a voltage higher than the nominal voltage and constant current for certain parts is ideal. I am considering getting this CC/CV buck converter and this SMPS. Then I can figure out the ideal voltages and currents later.
https://www.ebay.com/itm/24V-DC-15A-350W-Regulated-Switching-Power-Supply-Transformer-24-Volt/263703622296?hash=item3d65f5f298:g:xFQAAOSwrjZbA2xn
https://www.amazon.com/Aideepen-Constant-Current-Adjustable-Converter/dp/B0747QDRW9/ref=sr_1_1?ie=UTF8&qid=1527348156&sr=8-1&keywords=constant+current+constant+voltage+buck+converter
Would that work to charge them quickly and properly? And what does everyone recommend for voltages and currents here? I want optimal lifetime.

Also I try to avoid mains whenever possible. But given that almost all the power supplies require you to wire the mains yourself, I guess I will have to. But where would I get a mains cord for it, and what is the best way to avoid shorts and exposed wires here? Is heatshrink or something else required to ensure safety? Those screw terminals, especially with how close together they are, are making me nervous. I understand electrical safety and take all the necessary precautions, but do not really have any experience wiring mains.

I also need to have short circuit and over-discharge protection. I plan to be careful, but accidents do happen. And I am not going to be constantly measuring the voltage. So for overcurrent protection a fuse probably makes the most sense, as opposed to some sort of high current switch and shunt/hall. I want a fuse that can handle a few seconds of a little bit over the maximum current, or high inrush currents, but will blow if it is over by a little for more than a few seconds or by a lot for more than a fraction of a second. Or if there is some other resettable commercial option that is economical that would be nice. But I have heard that fuses are notorious for allowing overcurrent close to the max for many minutes. So what ratings do I look for in a fuse? What products do people suggest here?

For overdischarge, I plan to have a mosfet that turns an active buzzer with resistor on when the voltage is low enough. It should only consume a few 10s of mAs, and alert me to disconnect and start charging it. I will make sure to not leave it unattended. Is this a terrible idea, or will it be good enough for my purposes?

Then once I have all the equipment there is still the issue of the high current wiring. From what I have heard, screw terminals and think metal bars are commonly used for those types of connections, as opposed to soldering. Welding is more common if it needs to be permanent (like in a welding power supply). I do not really have the stuff to weld so I guess I will have to use other connectors. If someone could recommend some sort of pack that includes a lot of terminals and stuff, that would be great. Flexible welding wire seems like the best option here but I do not really know where to get it. Suggestions there would also be great.
Assuming no losses, I calculate that the battery could deliver 10,000W for 1 minute 20 seconds.
To achieve this the battery drain current would be in excess of 800A.
I think it highly unlikely that an 18AH battery could withstand a continuous drain current much over 40A.
 

Thread Starter

-live wire-

Joined Dec 22, 2017
901
I thought SLABs had high c ratings and were the cheapest available ($/WH). But would a lithium battery be more cost effective in the long run and have higher discharge rates? If it will last me a really long time I would be willing to maybe pay $100-200, but cost is a major factor here.
 

Hymie

Joined Mar 30, 2018
741
I reckon if you buy these two items from ebay sellers – you can make yourself a 600W variable DC power supply for £35.

https://www.ebay.co.uk/itm/Single-phase-DC-48V-12-5A-Switching-Power-Supply-for-Stepping-Motor-Driver/323249619977?hash=item4b432dc409:g:~VEAAOSwskha8~U1

https://www.ebay.co.uk/itm/1200W-20A-DC-Converter-Boost-Step-up-Power-Supply-Module-8-60V-TO-12-83V-M0/302720084586?ssPageName=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649

Based on the spec for the output module you could draw 20A at up to 30Vdc, de-rating the current to a maximum 600W [up to an 80Vdc output at 7.5A].

[I am making the assumption that the output module can output a voltage less than the input voltage – best check with the seller]
 

Thread Starter

-live wire-

Joined Dec 22, 2017
901
I reckon if you buy these two items from ebay sellers – you can make yourself a 600W variable DC power supply for £35.

https://www.ebay.co.uk/itm/Single-phase-DC-48V-12-5A-Switching-Power-Supply-for-Stepping-Motor-Driver/323249619977?hash=item4b432dc409:g:~VEAAOSwskha8~U1

https://www.ebay.co.uk/itm/1200W-20A-DC-Converter-Boost-Step-up-Power-Supply-Module-8-60V-TO-12-83V-M0/302720084586?ssPageName=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649

Based on the spec for the output module you could draw 20A at up to 30Vdc, de-rating the current to a maximum 600W [up to an 80Vdc output at 7.5A].

[I am making the assumption that the output module can output a voltage less than the input voltage – best check with the seller]
It probably cannot be lower, or it would be advertised as buck/boost. And it has no CC option. But good thought. And the goal is really a very large amount of power that is portable, for power hungry things. Good regulation is not too important.

I have looked around, and apparently lithium batteries are much better in the long run, for $$$, WH, and watts. I will probably try and make a 5p 4s 18650 pack with these 15C 2AH ones. That would be 14.4V nominal and 150A max, 10AH. But I need a good BMS, and it should be under $40. I could not really find one. Suggestions would be great.
https://liionwholesale.com/collections/batteries/products/sony-18650-vtc4-battery-genuine-tested-30a-2100mah-flat-top-wholesale?variant=1038136780
 

Reloadron

Joined Jan 15, 2015
4,905
Based on what you seem to want I would think about increasing the budget and buy a decent motorcycle battery or a car battery and be done with it. Then I would just get a battery maintainer and let that maintain the battery. While I have never needed 200 Amps of 12 VDC a decent SLA battery with a high cold cranking amp rating will deliver it. I used a Plane Jane Amazon battery maintainer I would just move to several 12 volt 10 AH batteries and another I leave one on my bike over the winters, starting my bike occasionally in the garage (with the door open). Works fine and keeps the battery topped off.

Ron
 

Thread Starter

-live wire-

Joined Dec 22, 2017
901
Based on what you seem to want I would think about increasing the budget and buy a decent motorcycle battery or a car battery and be done with it. Then I would just get a battery maintainer and let that maintain the battery. While I have never needed 200 Amps of 12 VDC a decent SLA battery with a high cold cranking amp rating will deliver it. I used a Plane Jane Amazon battery maintainer I would just move to several 12 volt 10 AH batteries and another I leave one on my bike over the winters, starting my bike occasionally in the garage (with the door open). Works fine and keeps the battery topped off.

Ron
So I found this promising 12V 7.5AH 14C SLAB. A lifetime of 200 cycles seems good enough for the price. I will probably get two or three because higher voltages means greater efficiencies.
http://www.batteryspace.com/sealedleadacidbattery12v75ah20hrsforupsseascooterande-bikes.aspx
The size and weight also look acceptable. Overall, the electrical and physical characteristics make it look like a good deal.

However, I have heard about electrolyte leaks, lead and lead dust spilling out, and other issues. I would obviously be careful when charging and discharging it, but it may have to deal with some physical trauma. I know SLA is safer than other LABs, but I do not want a significant risk of exposure to those chemicals. I have pets and there would be young children nearby. So if I take proper precautions, is there still a significant risk? Are less reliable sellers likely to sell SLABs that are not really too sealed? And once it starts to fail due to age, will there be an increased likelihood of these safety issues?
 

DECELL

Joined Apr 23, 2018
96
You say certain things... very coyly that's a worry...

All that lead that will have to be disposed of responsibly one day.
SLAB and Lions are full of corrosive electrolytes. Sealed or not a short can rupture the casing- or worse.
I've seen plenty of overheated UPS batteries crack open. Leak proof my A! (as us old geezers say)
Remember, high currents won't shock you but arc flash from high current faults can turn you, your pets and loved-ones to toast.
A poor connection or over current is all it takes. Plasma man.

I have used copper refrigeration tubing inside heat shrink for high current LV wiring- you can even water cool it in case your EM weapon is prone to jamming!


https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=DC-12V-24V-48V-400W-720W-Universal-Regulated-Switching-Power-Supply-LED-CCTV-&_sacat=0
bloody bargain!
 

Thread Starter

-live wire-

Joined Dec 22, 2017
901
You say certain things... very coyly that's a worry...

All that lead that will have to be disposed of responsibly one day.
SLAB and Lions are full of corrosive electrolytes. Sealed or not a short can rupture the casing- or worse.
I've seen plenty of overheated UPS batteries crack open. Leak proof my A! (as us old geezers say)
Remember, high currents won't shock you but arc flash from high current faults can turn you, your pets and loved-ones to toast.
A poor connection or over current is all it takes. Plasma man.

I have used copper refrigeration tubing inside heat shrink for high current LV wiring- you can even water cool it in case your EM weapon is prone to jamming!


https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=DC-12V-24V-48V-400W-720W-Universal-Regulated-Switching-Power-Supply-LED-CCTV-&_sacat=0
bloody bargain!
So essentially if I don't short or abuse it it is very unlikely for that stuff to happen? And for overcurrent protection with two batteries, do I need one fuse/CB for each battery? Would it be very unsafe and reckless to use just one? I will probably connect them in series, but may rearrange them for other things (where 12V and a higher AH is needed). I would not try to draw more than 100A from them in either configuration. I am leaning towards this circuit breaker and will probably get it, unless there are other things I should take into consideration.

Once I get that all worked out there is still the issue of charging and preventing over-discharge. For charging, I have heard you need to be careful to not exceed the maximum charging current and voltage. A CC/CV power supply seems like the best way to do this. And there would be many other applications I can think of for this. So I am thinking of using this power supply with this DC-DC CC/CV buck converter to make a decent power supply.
https://www.ebay.com/itm/360W-10A-AC110V-240V-to-DC36V-Switching-Power-Supply-Transformer-f-LED-Strip/272515375503?hash=item3f732ea18f:g:kHkAAOSwZQRYcz-j

For over-discharge voltmeters and circuit to buzz loudly when there is undervoltage may be an option. But at almost 100A, that is not a lot of time to react. So I think something else is better suited here. I could possible use a relay like this and make my own hall circuit with under-voltage protection. Or I could maybe put that in series with the CB and add a simple mosfet undervoltage detection circuit. The thing is it would draw a rather high current (.8A) and add more resistance. Maybe another type of relay or power mosfet is better for that.

I could use suggestions here on cost effective and reliable ways to protect against overcurrent and over-discharge. Maybe a certain board or something that includes all these functionalities?
 
Last edited:

Reloadron

Joined Jan 15, 2015
4,905
SLA (Sealed Lead Acid) batteries are perfectly safe both to be around and work around. That assumes good work habits and practices are followed and a quality product is used. Look at automotive, you are surrounded by SLA batteries. I can't recall the last time I added distilled water to a car battery but considering I am 68 I would guess maybe my early 20s. Every time I start my or my wife's trucks I place likely a 200 amp load on a SLA. Any battery including a small AA battery can be dangerous and all batteries contain chemicals which if ingested will cause animal and human alike a very bad day. I use SLA batteries in my UPS units and over the last 15 years have never had one leak or fail. I also have two dogs and the presence of SLA batteries has never been an issue. They likely have a higher risk of lead exposure from eating the paint off of a product from China. When I need to replace a SLA I go to the Battery Store (Batteries Plus) and buy a new one leaving the old one for disposal.

When a battery is used correctly and within its rated limits it really presents little danger to man or beast. While I can't fathom your high current needs just make sure you apply using a battery within the battery limits.

Ron
 

Thread Starter

-live wire-

Joined Dec 22, 2017
901
SLA (Sealed Lead Acid) batteries are perfectly safe both to be around and work around. That assumes good work habits and practices are followed and a quality product is used. Look at automotive, you are surrounded by SLA batteries. I can't recall the last time I added distilled water to a car battery but considering I am 68 I would guess maybe my early 20s. Every time I start my or my wife's trucks I place likely a 200 amp load on a SLA. Any battery including a small AA battery can be dangerous and all batteries contain chemicals which if ingested will cause animal and human alike a very bad day. I use SLA batteries in my UPS units and over the last 15 years have never had one leak or fail. I also have two dogs and the presence of SLA batteries has never been an issue. They likely have a higher risk of lead exposure from eating the paint off of a product from China. When I need to replace a SLA I go to the Battery Store (Batteries Plus) and buy a new one leaving the old one for disposal.

When a battery is used correctly and within its rated limits it really presents little danger to man or beast. While I can't fathom your high current needs just make sure you apply using a battery within the battery limits.

Ron
So do you think a battery like that can really supply that much current continuously (for a few minutes), or when the say "105A max" do they mean pulsed? I just want to make sure I am not misinterpreting it, as that seems almost too good to be true. I looked at the higher capacity ones, which were much more expensive, and they had similar current ratings but only for a few seconds. And what do you recommend for the over-discharge protection? Is a solid state solution or EM better here from a cost and reliability standpoint?
 

Reloadron

Joined Jan 15, 2015
4,905
Theoretically an 8 AH battery can supply 8 Amps for 1 Hour and 480 Amps for 1 min but I do not see that happening. Battery data sheets tend to overate battery capabilities and battery data on batteries in mass off the boat from China really take overrating to a new high. The only way to really know a batteries true capability is to test it for an intended application which will likely destroy the battery but you can assume others from the same lot should give similar performance.

If we look at the AH (Amp Hour) rating of a SLA battery and call it C a charge or discharge rate of 1C is a pretty common rule less any manufacturer data sheet. When a 12 volt SLA battery voltage drops down to right about 10.5 volts discharging the battery below that will likely damage the battery. So we toss a known load on the battery and monitor current and voltage. When the voltage drops to about 10.5 volts that's it. SLA batteries also get hot real fast when under a heavy load.

The battery you linked to reflects:
Max.Charging Current 2.1A
Max.Discharging Current 105A max

I doubt it will do that but really have no idea. The only way to actually know would be to load it and see what happens. Last time I was involved with battery testing was for some thermal batteries and those suckers went in an explosion proof cylinder and we monitored them using a video feed. I haven't a clue if the linked battery would deliver 105 Amps for a little under 5 min or not. That's really asking quite a bit of the battery.

Ron
 

Thread Starter

-live wire-

Joined Dec 22, 2017
901
I actually got an estimate for shipping and it was $30! So I guess I will have to look somewhere else for suitable batteries. Are there any websites that you have found to be particularly reliable and with many good deals? I looked at many different ones and NONE of them state the maximum discharge. That's one of the most important things when choosing a battery!
 
Last edited:

Reloadron

Joined Jan 15, 2015
4,905
I use Amazon as my wife has Amazon Prime. The very few times there was a problem they took care of it immediately. The prices are good and with an Amazon Prime account the shipping is paid. Locally another source I use is Batteries Plus Bulbs, A knowledgeable staff should be able to tell you anything you want to know about their batteries. You are going to have a rough time finding maximum discharge rates on the smaller SLA batteries. Larger flavors like motorcycle some will list the CCA (Cold Cranking Amps). While I don't know of a direct conversion between CCA and max discharge load the CCA will give you an idea of what the battery will deliver in short duration.

Ron
 

Thread Starter

-live wire-

Joined Dec 22, 2017
901
So looking around most SLABs are rated 3-4c continous and 15-30c <5 seconds. So that other one being 15c continous is very suspicious. Getting one that can really handle the current is very important, for many reasons. So unfortunately I may have to spend more. This 2-pack seems like a good deal. It has many reviews and they are universally positive. And the extra capacity will be very nice for certain projects. https://www.amazon.com/UPG-UB12350-Group-Battery-Universal/dp/B007Q2CUD0/ref=mp_s_a_1_3?ie=UTF8&qid=1528033871&sr=8-3&pi=AC_SX236_SY340_QL65&keywords=12v+35ah+battery&dpPl=1&dpID=41VjKN7R-JL&ref=plSrch
It looks like this is the data sheet for it. I assume if it is the same part # then the specifications must be the same.
https://www.mrsolar.com/content/pdf/Universal/UB12350.pdf
 
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