Lipo bulk charging

[mchlpeel]

Hi,

Is it possible to construct a lipo battery pack that has only one

Charging point that automatically balances etc.

Basically I want a lipo pack that is as simple to charge as a lifepo4 pack

How would I do this

 

[Ypedal]

use a BMS

 

[mchlpeel]

Would a bms mean that I would never have to do separate balance charging?

Where can I purchase a bms?

 

[dnmun]

the balancing chargers have a BMS built into the charger. so that will balance it but if you use a BMS on the battery then it will balance it while bulk charging without having to plug in the JST plugs, and protect against shorts on the output.

agnius found a source for BMSs that are cheap and well made from Bestechpower.com

 

[mchlpeel]

Ok thanks for the info

 

[motomech]

Hi,

Is it possible to construct a lipo battery pack that has only one

Charging point that automatically balances etc.

Basically I want a lipo pack that is as simple to charge as a lifepo4 pack

How would I do this

I have been doing exactly that for small Lipo packs (12S/2P or less) for several years with an inexpensive balance charger;

http://www.hobbypartz.com/75p-1220-charger.html

 

[mchlpeel]

I think I prefer the idea of installing a bms into the battery

To create a fire and forget solution.

 

[amberwolf]

I think I prefer the idea of installing a bms into the battery

To create a fire and forget solution.

As opposed to "forget and get fire" solution? :lol:

 

[Syonyk]

Yes - as has been stated, if you build a battery pack with a BMS, then charging becomes much simpler as you have the balancing device as part of the pack. You feed the pack a bulk voltage of (whatever is proper for the pack) and the BMS handles leveling between the cells so they are all balanced at the end of a charge.

If you're building a lipo pack with a BMS, you should also ensure the BMS you pick has LVC - low voltage cutout. This will turn off the output if a single cell of the pack drops below the specified voltage, and will hopefully prevent you from deeply discharging a degraded cell.

 

[mchlpeel]

Great thanks for the info

Just need to figure out how to construct a pack and how to integrate a bms

 

[amberwolf]

See the sticky topics here:
http://www.endless-sphere.com/forums/viewforum.php?f=14

 

[dnmun]

i do it by taking the HK lipoly packs apart to get them out of the shrink wrap before it can damage thme and then assemble them into a regular battery.

i use hard board end plates and put them in compression and then tie zip ties around them until i cana install them in the battery box where they are held in compression by the battery box.

 

[mchlpeel]

I have to say the above is not a great advert for a DIY battery pack


HOW MANY WIRES?!

 

[MadRhino]

RC lipo is not a proper chemistry for those who want to charge "plug and forget". They are the kind that you want to watch and never forget. The good side is that they don't need balancing and can be charged very fast, then you are never tempted to leave them charging alone. Some Lico cells can be charged 10C, that is 6 minutes bulk charging when you have enough current. I have some battery packs here that have seen 600 cycles and never been balanced, always charged 5C and up, often well above 4.15v.

Fitting a BMS to RC lipo is not making them safe to plug and forget. It does save them from the idiots for some time, but idiocy will always find its way to prove that Darwin was right.

 

[Syonyk]

^^ That's also a very valid point. The way to have a Lipo pack as safe to charge as a LiFePO4 pack is to buy a properly sized LiFePO4 pack.

 

[mchlpeel]

Valid points.

Unfortunately I am looking for a charge and forget system mostly because im lasy and dont have the time to give LIPO the care and attention it obviously needs.

Until there is a safe method I will stick to another chemistry.

Im currently looking at a 22.1AH 25R samsung pack from EM3ev which is 8C rated which will provide more than enough fun.

Its just sooo expensive compared to LIPO.

 

[Syonyk]

What exactly are you trying to do?

And, yes, safer chemistries are generally less energy dense, which means you need more battery, and typically pay more for it.

On the other hand, they generally aren't known for bursting into highly energetic flames. That's generally a plus, and I'm quite happy to pay more for high quality cells that aren't fire prone.

A good pack, properly maintained, should last a very long time. I'm hoping for around a decade of use on my LiFePO4 pack, and then it'll probably go into a kid's bike or something down the road.

 

[mchlpeel]

What exactly are you trying to do?

And, yes, safer chemistries are generally less energy dense, which means you need more battery, and typically pay more for it.

On the other hand, they generally aren't known for bursting into highly energetic flames. That's generally a plus, and I'm quite happy to pay more for high quality cells that aren't fire prone.

A good pack, properly maintained, should last a very long time. I'm hoping for around a decade of use on my LiFePO4 pack, and then it'll probably go into a kid's bike or something down the road.

Agreed.

Im looking to power an 18 fet controller at 60Amp Max

to run a 1500W Leaf Motor

 

[Syonyk]

You don't need 60A to run a motor at 1500W... why are you using a 24v pack for this? 60A is hard to come by for large battery packs, and if you want it, you'll need a lot of capacity to get the current. There aren't terribly many BMS boards that like 60A either.

Run 36v or 48v and your amperage requirements go down a good bit. I'm pushing a "36v" (about 39v nominal) at 35A and have plenty of power for all my riding - it's around 1350W, depending on how I do the math.

I'm not going to argue that a good pack is expensive, but a high quality pack will last a long time, and won't burn your house/apartment/etc down if it has a bad day.

 

[mchlpeel]

I intend to run that motor at

50v 60A

This motor is pretty resilient and can take this sort of power

 

[MadRhino]

I intend to run that motor at

50v 60A

This motor is pretty resilient and can take this sort of power

50v 60A batt, let's say over 100A phase (could be set as high as 140 A phase)... That is at least 5 000 W, yet I believe that motor can take more.

RC Lipo's are not cheap, they are just a more aggressive chemistry that doesn't last as long. At the end, you pay more for RC Lipo. They are good when you need a lot of power, at the cost of strict care and monitoring. I consider RC lipo can be safe for some, and very dangerous for others. This is about how one can be reliable to apply proper safety measures at ALL time.