Help! Any portable batteries that could supply more than 5 amps of power for charging lipos
- Thread starter Ryan O.
- Start date
Pop down to the local walmart and pick up a 200cca lawn tractor battery. That battery's capable of sending out something stupid in a dead short scenario(Something like 400 amps on a warm day 
), yet it doesn't weigh too much, isn't too big, and is the right input voltage for most hobby chargers.
), yet it doesn't weigh too much, isn't too big, and is the right input voltage for most hobby chargers.
Lead acid batteries are ill suited to this application, they are designed for short bursts of high current (ie starting an engine) and then a nice slow recharge. They don't like being drained and recharged, you need deep cycle batteries for this (on a large scale, like solar). Lipos are also good for this, any decent size Lipo can put out 5 amps for the entirety of it's capacity.
To select a proper Lipo you need to know what you want out of it. "A decent amount of battery packs" is terribly vague That could mean 35 1s 150mAh packs or 35 10000mAh 6S packs. It's all about energy. Volts x amp hours is watt hours. Calculate what you need (ie a 2200 mAh 3s would be 2.2 x 11.1V = 24.42Wh) Then find out the max voltage your charger can accept as input to determine the cell count you want. Say your charger can accept 24V - the biggest you could go with is 5S - 21V fully charged. 6S is 25.2, which would kill your charger eventually. Say you want to recharge 6 of the 2200 3S packs above, that's 146.52 Wh. To get the capacity you need at 5S, divide 146.52 by the 5S voltage of 21 = 6.977 amp hours, or 6977mAh. Then it's just a matter of shopping for the battery you need. Less expensive, low C rated lipos are perfect for this.
Math. It's always math
To select a proper Lipo you need to know what you want out of it. "A decent amount of battery packs" is terribly vague
That could mean 35 1s 150mAh packs or 35 10000mAh 6S packs. It's all about energy. Volts x amp hours is watt hours. Calculate what you need (ie a 2200 mAh 3s would be 2.2 x 11.1V = 24.42Wh) Then find out the max voltage your charger can accept as input to determine the cell count you want. Say your charger can accept 24V - the biggest you could go with is 5S - 21V fully charged. 6S is 25.2, which would kill your charger eventually. Say you want to recharge 6 of the 2200 3S packs above, that's 146.52 Wh. To get the capacity you need at 5S, divide 146.52 by the 5S voltage of 21 = 6.977 amp hours, or 6977mAh. Then it's just a matter of shopping for the battery you need. Less expensive, low C rated lipos are perfect for this.Math. It's always math
Lead acid batteries also don't really care too much about being run down to damn near 0 volts. They'll come back from that just fine. You run a lipo down that low and it's a ticking time bomb. And while you do have a point about the typical car battery(It must be said that even these specialized cranking batteries will come back from stone dead a few times before they're hooped), lawn-and-garden batteries tend to be more of a general purpose type that can handle being discharged and recharged over and over again. It happens to them anyway when the lawn tractor spends four months in a back corner of the garage unused, after all.Lead acid batteries are ill suited to this application, they are designed for short bursts of high current (ie starting an engine) and then a nice slow recharge. They don't like being drained and recharged, you need deep cycle batteries for this (on a large scale, like solar). Lipos are also good for this, any decent size Lipo can put out 5 amps for the entirety of it's capacity.
To select a proper Lipo you need to know what you want out of it. "A decent amount of battery packs" is terribly vague
Math. It's always math
A lawn tractor battery of ~200CCA will do what OP needs with no problem whatsoever, and with no risk if OP forgets to disconnect the charger(As they seldom, if ever, have an LVC built in).
It's also worth noting that the DC input of most chargers is designed with the idea that you'll slap a couple of alligator clamps across the terminals of your car's battery while you're out in the field. Put 25+ volts in there and most will let the magic smoke out. Certainly is the case with my charger. It can do up to 6s batteries but the input jack is only rated for a max of 18 volts. If I put a 6s battery on the input side it'd fry it in an instant. Thing's got a buck/boost circuit in there that takes the input and knocks it up to 26 volts or so if it needs to charge a 6s lipo.
Here's a good thread where a couple forum members (including myself) have built charging boxes using deep cycle sealed lead acid batteries.
https://forum.flitetest.com/index.php?threads/dry-box-to-charging-box.19482
I don't use mine that often for local flying, but it's useful for taking to events.
https://forum.flitetest.com/index.php?threads/dry-box-to-charging-box.19482
I don't use mine that often for local flying, but it's useful for taking to events.
