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Charging power tool battery with SCC?

SomebodyInGNV

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Jun 3, 2020
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I have a Black & Decker 12V cordless drill. By the battery voltage you can tell it's old, but it works well and the batteries are good. I have the original slow OEM charger which has a power brick. I want to hack it to use solar power for charging. I have another fast charger that plugs directly into the wall, so hacking the old one is no loss.

The output of the brick is 14.5V. Is the load output of my SCC sufficient to charge the drill batteries? It would be the only thing I connect to the load terminal on the SCC and it's not essential that it's working all the time. I'm just looking for a way to keep the battery topped off without shore power and hoping to not have to resort to using the inverter.
 
The wall brick is going in the trash. It's the input to the charger base and has two conductors. Output is 14.5VDC at 200ma.

I plan to cut off the brick, determine the polarity of the conductors, and connect them accordingly to the load terminals on the SCC. Beyond that, I have no plans to use the load terminals.

Is that what you're asking?
 
Okay, so you already have the SCC connected to PV and its own battery. You want to use the load terminals to provide the power for the charger plug, which will plug into the charger base and charge the drill battery from the SCC load ports.

Load port = SCC battery voltage, so it depends if the charger base will accept voltage lower than 14.5V.

Load ports have a current rating, so it's important to not exceed that.

This all depends on where the smarts are. If the smarts are in the battery or the charger base, and they're fine with 12.X to 14.XV input you should be good. If the smarts are in the brick, then you're out of luck.
 
I think the brick is dumb. It's nothing more than the cheapest old-style wall brick. The charger base has a light to indicate if it's charging or charged, so I assume whatever smarts exist (not much) must be there. I'll open it tomorrow.

The brick output is only 200ma so the charger base can't be much of a drain on the SCC.
 
You want to use the load terminals to provide the power for the charger plug, which will plug into the charger base and charge the drill battery from the SCC load ports. ..
To clarify a bit, the brick is hard-wired to the charger base. The brick is the kind you'd find powering the base of a cordless phone extension. (Remember landlines?) The wires between it and the base are tiny, like 20 or 22 gauge.
 
It may be dumb, but it may be the smarts. Something has to limit voltage and current. A power supply that delivers 14.5V @ 0.2A may be exactly what is needed to fully charge the battery. If the base is nothing more than an adapter to get 14.5V the battery, and the base nor battery has a DC-DC conversion to boost < 14.5V to 14.5V, you're throwing away what you need.

You're not going to get exactly 14.5V and 0.2A out of the load ports of the SCC.

You need to figure out what the battery needs to charge it, and supply it. The 14.5V, 0.2A transformer may be exactly what the battery needs to charge.

What's the output of the transformer on the fast charger?

You would likely be better served by obtaining a DC-DC converter that accepts 12-16V input with adjustable output. Dig around on Amazon and eBay, and you'll find gobs. Of course, there's a conversion penalty, but it might not be as bad as the 14.5V/0.2A brick.
 
My goal is to not spend money. I can always plug the smart fast charger into my inverter.

I'll look inside the cases of both to compare how they work.
 
Just like when you programmed your charge controller for your battery parameters, you need to do the same for this battery. The only known is the 14.5V and 0.2A, and that really sounds like the smarts in the system.

What is the fast charger's output?
 
The fast charger will charge all B&D batteries between 9.6V-24V. It has 2.3A output. I don't know what's inside it but the power cord is just a standard 120V polarized plug w/o ground.

This is the entirety of the circuits on the slow charger.16116719175363569556415769768849.jpg
This is the brick. I'm just going to cut off the wires at the brick, connect them to the load terminal and see what happens. I can set the SCC to shut off the load below 14.4V.
16116721359194164248488033180330.jpg 16116722595713076450721748405644.jpg
 
You are making an essentially unlimited amount of current available to the battery with no upper limit on voltage if your charge controller drives higher. You will also only charge drill battery when your SCC battery is in bulk/absorption mode.

I would test on batteries you are okay with destroying.
 
You are making an essentially unlimited amount of current available to the battery with no upper limit on voltage if your charge controller drives higher. You will also only charge drill battery when your SCC battery is in bulk/absorption mode.

I would test on batteries you are okay with destroying.
Yeah, probably not a good idea. The inverter it is. I'll just get a very small one dedicated to this purpose.
 
The DC-DC converter option above might be cheaper and more efficient:


$11.99

Wide range input voltage, adjustable output voltage and current. Likely less efficiency losses compared to an inverter.

14.5*.2 = 29W... brick inefficiencies and inverter inefficiencies at such a low power might be huge.
 
The DC-DC converter option above might be cheaper and more efficient:


$11.99

Wide range input voltage, adjustable output voltage and current. Likely less efficiency losses compared to an inverter.

14.5*.2 = 29W... brick inefficiencies and inverter inefficiencies at such a low power might be huge.
Thanks. I see that it can be set for a constant current, but is the output voltage constant for a device like that, where input voltage is variable?

Edit: this one comes in a nice little box for only $2 more. I interpret what I read in the details to mean that the input voltage must be higher than the output. (Duh. It's a buck converter.) I can set the SCC load output to shut off below 15V, so the converter will always get V > 14.5, which is what I'd set the output to.
 
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I think we're missing some important details:

What battery is connected to the SCC?
Can that battery sustain 15V safely?

To reiterate, the SCC load ports ARE the battery it's charging, i.e., if you have a 12V battery connected to it, and it's charging at 13.6V, the load ports will be 13.6V.
 
It's an SOK 12V 100A LFP connected to an Epever Triron 4210n. (Actually, 2 in parallel.) From Min, Boost is set to 14.6, Limit is 14.6, cut-off is 14.7.

If the load output will never exceed 14.6, I'll set it to cut off at 14.4. That way it will always get at least 14.5 but not more than 14.6, correct? It doesn't matter if the drill battery charges only minimally, and intermittently. That's how it's used, and it should be well charged in between uses.
 
Okay. So, no way the SOK can tolerate 15V. Yes you can set that narrow of a range, but the current is still unregulated.

I would still install the DC-DC I linked. It apparently has some flexibility on the input:

1611691674800.png

This would allow you to regulate the output current and permit charging through a wider range of input voltages. 13.5V and above?
 
Sounds like the old battery is either Ni-Cad or Ni-MH.

Both are totally incompatible with typical SCC and lead-acid or lithium charge methods.

Old charger probably also outputs actually more than 14.5v unloaded and on waveform peaks.

I hate charging Ni-cad/NiMH chemistry based batteries as SOC and charge termination are pretty much guesswork based on how hot the cells get during charge. On the other hand they are really tolerant for abuse compared to lithium.
 
Assuming these are Ni-xx batteies the cheapest way is to use small DC-DC converter from ebay/alibaba/whatever.

Set the charging voltage to 17 volts and 0.1C charge rate, charge until battery is lukewarm or max 12 hours.
If you want faster charging charge at 1C until battery is warm or max 80 minutes.

If you want more automatic process you can buy something like Turnigy accucell-6 that charges pretty much any <20v battery
 
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