Rick2021 Posted October 16, 2021 Share Posted October 16, 2021 Well i have a 120vdc 3a charger. I also have a 40vdc 6ah battery. Can I charge the battery with a 30vdc 10a charger first to get the amps up then step up to the 120vdc charger to top off the voltage? Hopefully you folks can let me know it that would work or not. I really don't want to buy a 100vdc 10a bench charger at $600. I'd rather do a step up if possible buy a 30vdc 10a charger for $60. I would appreciate your thoughts Quote Link to comment Share on other sites More sharing options...
Chriull Posted October 16, 2021 Share Posted October 16, 2021 (edited) 1 hour ago, Rick2021 said: I also have a 40vdc 6ah battery. How comes 40V? That's a strange number for a li.ion battery pack. Quote Can I charge the battery with a 30vdc 10a charger first to get the amps up If the 40V battery is discharged to some voltage than 30V one could theoreticly/presumable charge it with a 30V charger. But as no details are known about the pack or charger i'd say no. Edit: like if this 30V charger is for li ion at all? 1 hour ago, Rick2021 said: then step up to the 120vdc charger to top off the voltage No. Never. That will destroy the battery - three times overvoltage. One could have good luck and the battery has some overvoltage protection so it does not go up in flames... 1 hour ago, Rick2021 said: I really don't want to buy a 100vdc 10a bench charger at $600 Why a 100V charger for a 40V battery? Edited October 16, 2021 by Chriull Quote Link to comment Share on other sites More sharing options...
Rick2021 Posted October 16, 2021 Author Share Posted October 16, 2021 27 minutes ago, Chriull said: How comes 40V? That's a strange number for a li.ion battery pack. If the 40V battery is discharged to some voltage than 30V one could theoreticly/presumable charge it with a 30V charger. But as no details are known about the pack or charger i'd say no. Edit: like if this 30V charger is for li ion at all? No. Never. That will destroy the battery - three times overvoltage. One could have good luck and the battery has some overvoltage protection so it does not go up in flames... Why a 100V charger for a 40V battery? 1 hour ago, Rick2021 said: Well i have a 120vdc 3a charger. I also have a 40vdc 6ah battery. Can I charge the battery with a 30vdc 10a charger first to get the amps up then step up to the 120vdc charger to top off the voltage? Hopefully you folks can let me know it that would work or not. I really don't want to buy a 100vdc 10a bench charger at $600. I'd rather do a step up if possible buy a 30vdc 10a charger for $60. I would appreciate your thoughts Well I’m thinking I didn’t make it clear exactly what I’m doing. I have a 120vdc 3a charger and I have a 40vdc 6a battery pack containing lithium ion cells so my problem is I can set the charger for the 40 volts and the highest amps which is 3 but I need 6amps to get the battery fully charged to 40v 6a So I thought maybe I could do a step up in charging. So if I use a 30vdc 10a charger set it to 30volts amps to 6 and charged it at that level. Then step it up by using the higher voltage charger set to 40volts and the amps to the highest which would be 3amp and I’m hoping with the second step I could charge the battery fully to 40v 6a? I don’t know if that would work. The right way is to buy a charger with the adjustable voltage and amps to charge whether it’s a 18v2a, 40v6a or 80v4a. But I don’t have all that kind of money to invest in the proper equipment. And since I’m one foot in the grave who knows how much longer I will live. I’m just a backyard monkey trying to charge tool batteries 1 Quote Link to comment Share on other sites More sharing options...
Chriull Posted October 16, 2021 Share Posted October 16, 2021 18 minutes ago, Rick2021 said: I have a 120vdc 3a charger and I have a 40vdc 6a battery pack containing lithium ion cells so my problem is I can set the charger for the 40 volts and the highest amps which is 3 but I need 6amps to get the battery fully charged to 40v 6a No. Your battery has 6Ah! So if charging with 3A it's just taking twice as long as with 6A. If your battery is allowed to be charged with 6A at all! If your chargers are li ion chargers? The voltage values are very strange for li ion... Quote Link to comment Share on other sites More sharing options...
supercurio Posted October 16, 2021 Share Posted October 16, 2021 Same as @Chriull: a 40V lithium-ion battery is not possible. It's neither a multiple of 4.2V (max voltage for 1 cell) or 3.6V (nominal voltage for 1 cell) Then Ah: Amperes per hour is a unit of capacity, whereas A is a unit for current (speed of charge/discharge) Some clarification is needed: photos maybe? In the meantime, please don't try to plug and charge anything! Some of the operations you are considering would likely result in a battery fire, and might burn up your home. 3 Quote Link to comment Share on other sites More sharing options...
Rick2021 Posted October 16, 2021 Author Share Posted October 16, 2021 Oh so I guess I need to find the charging input for each different battery. Dang I’d be hundred years old by the time I find all the material on the different varieties. Oh I thought If a battery is a 80vdc 4a I can just put it on a charger and set it to 80v 4a and walk away. So your saying if I have this right I need the charging input for that battery and set the charger to that input value. So example if the 80v battery has an input value of 80v and only 2amp that would be the setting. If I put more amps then I could blow up the neighborhood. Right or did I figure wrong again? Do I make any sense? 2 Quote Link to comment Share on other sites More sharing options...
Unventor Posted October 16, 2021 Share Posted October 16, 2021 (edited) @Rick2021 I think you need to find how your battery are designed first. Right now it seems you think of this in the wrong way. Try to have a look at this at some point it is from a Polish reseller, but written in English: https://eunicycles.eu/en/news/wszystko-o-bateriach-li-ion-w-monocyklach-elektrycznych The thing is a Li-ion battery do not have a constant voltage. it has a working range. In the EUC we see some set "standards" of ranges but to make this easy to refer to we only use their top voltage, like 67v or 84v or 100v or 126v These can be rounded of a little. I am not sure what the battery you are using or what you want to build is supposed to do and how much volt it needs. In the article you will see 2 things that limits the charging, and this is important. 1: is the end at charging , not to over charge at a higher rate that the battery chemical can handle. 2: if constructed of multiply cells like most battery are, you need a cell balancing phase. both of these steps are not linear. So this meas if you have a charger at same volt but 2x amp rating then 90% of the time will maybe be able to go at half the time. but the last part take roughly the same time. There is a little more to this so this is looked at it simplified a bit. Also charging at a faster/higher rate wears down the battery faster. this means less charge cycles. Also covered in the link above. There are many things to consider into this. But to me the risk of one cell failing or not being balance is more important to me for 2 things. one I can't as easy see it if it happens sine our battery packs do not have individual cell monitoring. and second this is a high risk of causing a fire in the battery. And that i want to prevent at almost any cost. I hope this helps you.If not sorry for spending 10min of your life. Edited October 16, 2021 by Unventor Batteries are not toys, they can be dangerous if you don't know what you are doing. 1 Quote Link to comment Share on other sites More sharing options...
Popular Post OldFartRides Posted October 16, 2021 Popular Post Share Posted October 16, 2021 Obviously, you came to the right place by accident. Here’s what you need to do: Sell the tools, buy an electric unicycle, start having some fun. Best, 4 Quote Link to comment Share on other sites More sharing options...
supercurio Posted October 16, 2021 Share Posted October 16, 2021 9 hours ago, Rick2021 said: Oh I thought If a battery is a 80vdc 4a I can just put it on a charger and set it to 80v 4a and walk away. So your saying if I have this right I need the charging input for that battery and set the charger to that input value. So example if the 80v battery has an input value of 80v and only 2amp that would be the setting. If I put more amps then I could blow up the neighborhood. Right or did I figure wrong again? Do I make any sense? Still mixing up Ah (capacity) and A (current) here. There's no such thing as "4A battery" (except it you talk about how much current it can deliver safely, but that always depend on cooling, it's something else) 1 Quote Link to comment Share on other sites More sharing options...
Rick2021 Posted October 16, 2021 Author Share Posted October 16, 2021 10 hours ago, OldFartRides said: Obviously, you came to the right place by accident. Here’s what you need to do: Sell the tools, buy an electric unicycle, start having some fun. Best, Can’t disabled I can only dream using 2 legs and 2 arms Quote Link to comment Share on other sites More sharing options...
OldFartRides Posted October 16, 2021 Share Posted October 16, 2021 Sorry man. That’s a bad deal. Quote Link to comment Share on other sites More sharing options...
Unventor Posted October 17, 2021 Share Posted October 17, 2021 1 hour ago, Rick2021 said: Can’t disabled I can only dream using 2 legs and 2 arms This is meant is best possible way, sorry to hear that. On the other hand, arms are not really needed to ride EUCs. Also I have seen stories and videos of a guy riding using one leg only as in missing one leg. And another guy using artificial lower leg (both legs). Sometimes it is mind blowing what "disabled" people can do. I mean some can do things I couldn't even dream of despite the challenges they have. I myself have rheumatic problems and when I started I couldn't stand balancing on either one leg. Now I can and ride too. The videos ai saw back then I were not able to find but they have been posted here so maybe someone recall their title. I can't read what kind of disability you have and to what level. Quote Link to comment Share on other sites More sharing options...
Tawpie Posted October 17, 2021 Share Posted October 17, 2021 18 hours ago, Rick2021 said: If I put more amps then I could blow up the neighborhood Unlikely it'll be quite that bad, but in general if you can spare the time, it's better to charge with lower current (amps). You don't want your charger to supply more current than the battery and its associated wire and connector are designed to handle. I'd set it to something like 1 amp, a full charge will take 6 or so hours and you should be perfectly safe... but pictures of the label on the battery will help us be more definitive. 8 hours ago, supercurio said: I need the charging input for that battery and set the charger to that input value This is the one thing that you absolutely must get correct. You must set the charger's output voltage to match the "fully charged" voltage of the battery pack. If you set your charger's output voltage below the pack's fully charged voltage, the pack either won't charge at all or it will not receive a full charge. Generally not desired, but should not set anything on fire. Setting the charger's output voltage higher than the pack's fully charged voltage can, if things go ever so slightly wrong, cause a fire. It might not start a fire, but the chances of a fire are both not zero and not worth gambling on... if nothing else, it'll ruin your day, your battery and your charger. 2 Quote Link to comment Share on other sites More sharing options...
..... Posted October 17, 2021 Share Posted October 17, 2021 (edited) Please do a little more research before charging the batteries. Your confusion about capacity AMP HOURS and charging current AMPERAGE, are a sign of 'danger! danger!' Your figures of voltage seem to be a little general as well. Theres also the fact that you need know how many of the batteries are in series vs parallel. A pack consist of many individual cells. Depending on their configuration as a set, changes how you charge them. There is also concerns of balancing each cell. I am truly not trying to be a d*ck here. I do that in a more obvious manner. I simply think you could ruin your batteries and or the project you have in mind. Theres also a small chance of fire. Lithum batteries are really finicky, so don't be shocked if it seems like a bunch of excessive bullsh*t. They arent like the old nicad or mimh batteries we abused and loved back in the day. Hopefully the pack has the information about voltage and charging amperage on it. Capacity of Amp Hour is important, but charge rate (amperage) and charge voltage (volts) is what you really need know. With proper charger, it would likely taper down as the batteries got full and would stop itself, regardless of the capacity. End of charge is typically triggered by voltage, rather than the end amount of amps sent. The reason is that a battery doesnt really know how low it is to an exact amount. It knows its volatge, but the AMP HOURS of energy within it, can vary a little for a set voltage. Because of this, chargers wait on voltage to know they are full. SOME have safety in the chargers that enable you to stop the charger after a certain amount of amp hours, regardless if end voltage never hits peak. This safety feature prevents excessive overcharging, should a pack contain cells that wont reach max volatge. However, max amp hour alarms arent failsafe, as a bad single cell in a larger pack can easily ignite long before much amperage flows. Fwiw, my big euc is over 300 amp hours at 100.1V (estimated). This doesnt mean I need charge it at 100.1v 300amps. If i tried, sh*t would blow. Typically i charge it at a meager 3amps 100.1V(end voltage) or so. As a safety measure, my charger starts at a much lower voltage and slowly ramps up to 100.1v as it nears completion. Yeah, stupid confusing! Damn, that was a lot of random info. I hope i got most of that right and didnt confuse you. Anyhow, welcome to the forums! I didnt notice in the rules here, that you need own or even ride an euc, to be a fan/member. Hang out a bit, even if you dont have an euc, you have a point of view and opinion. Maybe you've a good story and joke or two! Edited October 17, 2021 by ShanesPlanet 1 Quote Link to comment Share on other sites More sharing options...
rcgldr Posted October 17, 2021 Share Posted October 17, 2021 (edited) You don't charge a Li-ion 6AH battery pack at 10 amps. Normally you would charge at 1/2 C or 3 amps. The charger also needs to be able to transition into a constant voltage charge once the pack is near charged. 40 volts is probably 42 volts max, or 10 cells, so you would need a 10S (10 cell) charger with balancer if there isn't a balancing circuit board on the device with the battery pack, which can get pretty expensive. Edited October 17, 2021 by rcgldr 1 Quote Link to comment Share on other sites More sharing options...
RagingGrandpa Posted October 20, 2021 Share Posted October 20, 2021 @Rick2021 : you want CC-CV charging. "Constant-current, then constant-voltage" Some intro materials are found below:https://www.grepow.com/blog/what-are-the-3-stages-of-lithium-battery-charging/ (ignore "precharge" because your battery voltage should never be so low to need it)https://www.youtube.com/watch?v=taNI-7x5BoY https://www.youtube.com/watch?v=FaEX_2Ubc7A And, most consumers do not need to understand it. Instead, they meet their needs by purchasing a charger specifically designed for their device. Who makes your 40V battery pack? What is it used for? Some context would help us 1 Quote Link to comment Share on other sites More sharing options...
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