12v 5a power adapter to recharge the 3s batteries of DIY IH?

[ericromano96]

Guys, I'm noob on this matter, just following u/vapoven's guide to build my first induction heater for M7 and B.

So, there are instructions to user 12.6v 1a power adapter but only have 12v 2a one right now and facing very slow charging. So, can I use 12v 5a power adapter to recharge the 3s batteries and use main line when needed?

 

[Chainfish]

Just speaking in reference to the 18650s, and not aware of any being safe/recommended to charge above 1amp. copied and pasted off Bing-
The safe amperage to charge 18650 batteries depends on their capacity and chemistry. Here are some guidelines:

1. Charging Current: A general rule of thumb is to use a charging current that is no more than 1/2 or 1/4 of the battery’s capacity1. For example:
   • For a 700mAh battery, no more than 350mA charge current.
   • For a 2000mAh battery, no more than 1A charge current.
2. Recommended Charging Current: The recommended charging current for 18650 batteries is around 0.5 times their capacity (0.5C charge rate). For instance, if you have a 2600mAh battery, the safe charging current would be approximately 1.3A2.

Remember to use reputable chargers and follow manufacturer instructions for optimal safety and battery health!

 

[ericromano96]

if you have a 2600mAh battery, the safe charging current would be approximately 1.3A2.

I have 9000mAh in total, then should I try 4 amp to recharge them?

 

[Cheebsy]

According to your circuit diagram your cells are wired in series. This increases the available voltage, but not the capacity. The safest way to improve charge times would be to make them removable to charge in a dedicated charger.

 

[KeroZen]

Check your particular cell model datasheet. Modern chemistries can handle higher charge rates, especially the pouch-type Li-Po cells. But in all cases higher charge current will reduce the cells service life. You'll gain some time at the expense of their life time.

For instance if you were to use the Samsung 25R as per your schematic recommandation, the manufacturer ratings are 1.25A for standard charge current and 4A for the maximum rapid charge. In all cases it should ideally be done under temperature supervision, old cells have more internal resistance and if your cells get too hot during charging it can be bad.

I would stick to 2A max personally. I don't know what your BMS is anyways and you should follow its specifications. Advanced ones can do balance charging etc. But if the BMS is managing the charge current, what will happen if you exceed its rating depend on the circuit configuration and the eventual protection in place and how they are implemented.

Anyway 12V will not be able to charge them fully, you really need 12.6V.

 

[ericromano96]

Thanks for your detailed reply. I'm sharing a bit more as my charging time almost 16 hrs, but yet to be full charged.

For instance if you were to use the Samsung 25R as per your schematic recommandation, the manufacturer ratings are 1.25A for standard charge current and 4A for the maximum rapid charge. In all cases it should ideally be done under temperature supervision, old cells have more internal resistance and if your cells get too hot during charging it can be bad.

Here's my specs for each cell

• Capacity: 2800-3000mah

• Internal resistance: <30mΩ
• Max discharge current: 25A
• Max charging current: 4A

I would stick to 2A max personally. I don't know what your BMS is anyways and you should follow its specifications. Advanced ones can do balance charging etc. But if the BMS is managing the charge current, what will happen if you exceed its rating depend on the circuit configuration and the eventual protection in place and how they are implemented.

I'm using 3s 10A BMS right now.

• Maximum discharge current: 10A
• Overcharge detection voltage: 4.25-4.35V±0.05V
• Over-discharge detection voltage: 2.3-3.0V±0.05V
• Maximum working current: 5A-8A
• Transient current: 9A-10A
• Quiescent current: ＜30uA
• Internal resistance: ＜60mΩ
  

want to replace above one with 3s 25A (or 20A?) BMS -

• Overcharge voltage range: 4.25-4.35v + 0.05v.
• Over discharge voltage range: 2.3-2.7v + 0.05v.
• Operating current: 0 – 25A.
• Operating temperature: -40 – +50℃.
• Instantaneous current: 35 – 40A.
• Storage condition: -40 – +80℃.
• Quiescent current: less than 30uA.
• Balance current: about 40 – 50mA.

So, what if I use 12v 5A as the power source with 3s 25A (or 20A?) BMS, will it improve any thing or things might get worse? I want to use the ZVS induction heater directly from the main power besides the battery power.

Anyway 12V will not be able to charge them fully, you really need 12.6V.

My current power cable supplying 12.8v as checked with voltmeter, is this a problem?

 

[KeroZen]

Without the specs of your induction heater it's hard to give you any answer. But if it works with your battery pack through your existing BMS and if the specs are correct, we can assume the battery is providing less than 10A max at its nominal 12V voltage. The "Maximum working current: 5A-8A" is not very clear, maybe the BMS supports only 10A peaks and 8A continuous output?

Based on these figures, if you want to bypass the battery pack, you would need an AC-DC converter able to supply 10A continuous. Many Chinese ones are completely over-rated and even if they can output their max rating (really rarely the case) they will get pretty hot. To be on the safe side you could use a 15A or 20A power supply.

If you want good quality, get a Mean Well switching PSU, like those meant for LED driving: https://www.meanwell.com/ Most have somewhat adjustable output voltage, so a 12V one could be possibly cranked to 12.6V (but more on that below) If it's just for pass-through power then leave it at 12V. But they are probably way above your budget...

So alternatively for around 20€ you could get one of those Chinese PSUs, just select 12V and 20A: https://www.aliexpress.com/item/1005007045758794.html

With a PSU you should in theory be able to remove the battery completely and hook it directly to your heater and get proper pass-through power.

Now for charging your battery faster, I don't have enough info to safely advice you. It's not clear what's inside your BMS and if it has any real charging IC or if it's merely passing the input current to the cells and just monitoring for an overvoltage condition. The second specs mention a balance current but it's very low so I assume that MAYBE it's the balance discharge current? And then MAYBE that BMS can do balance charging.

If the BMS acts as a proper charger then it will limit the input current to a preset value anyways, so it doesn't matter if your PSU can provide more. It will perform CC-CV charging at the rate it's setup to operate (most can adjust the CC part by modifying a component value, but since it's likely surface mount I assume it's beyond your skills level)

If the BMS is not a real charger, and your schematic kinda makes me think it could be the case, then indeed you should stick to their 12.6V 1A PSU recommendation as written on that schematic and not take any risks.

Anyways all the disclaimers are there for a reason, the dangers are real. If you over-charge your battery it could burn down your house and I don't want to be responsible for that. And even if you remove the battery from the equation, the listed 20A Chinese PSU is hazardous with it's exposed terminals, touching the live input and you'll get AC zapped.

 

[ericromano96]

If the BMS is not a real charger, and your schematic kinda makes me think it could be the case, then indeed you should stick to their 12.6V 1A PSU recommendation as written on that schematic and not take any risks.

Thanks for your detailed answer! I'll stick to the current setup now and do some study on your shared points. Thanks again