Headway questions, Can I charge lifepo4 with no bms?

[electricridefl]

I need to buy new batteries for my 72v 20amp ebike. I used 9ah sla , they lasted a year. I bought 2 36v 10ah ping batteries. They lasted a year with the bms. I then ran them for 2 more years with no bms. I bought abunch of 7.2v nimh rc sub c cells and have been running 2 batteries with 72s for several months now. A single charging mistake can sure ruin a lot of cells. I am unable to charge these things properly without constant monitoring. I could buy some a123 packs or 12v batteries from ebay seller that would cost $600 for only 4.6ah 24s battery. I am looking at the 10ah headways on ebay for under $600 for 24s. I read on this forum that some balance their cells only once a week. Also, there are several types of lifepo4 12v starting batteries with no bms. I plan to charge with 36v sla charger, and also would like to charge with 36v 20a golf cart charger. Has anyone run this type of battery new with no bms? I could charge each 4 cells with 12v charger. I would still be willing to run no bms even if it shortened my battery life to 2/3 or so. Do I risk killing cells quickly this way? I would like to hear from anyone who runs these type cells with no bms. If I ran a 13s and charged with cv up to 44.5v, would the battery get charged. If I maintained a lower overall voltage, would this be better for the cell, or would they not get charged fully? I have run sla batteries with a charger that tops out at 13.6 v, and the battery charged fine, and I think it was actually better for the life of the battery. Don't the lifepo4s tolerate just a tiny bit of overcharge (for balancing). Surely I would not ruin the lifepo4 quickly? Can the headway cells burst? I constantly overcharged my pings more so to the end of their life. They did all swell up. And they heated up. I puncturd all the cells with a needle, and then drove them some more. No lvc or bms. The ping battery kept going. Thanks for any input, unless you tell me not to do it.
Also, will the headways short out if touched together? If I do use these, I will need to connect the cells in groups of 2 legnthwise, with the right nuts to better fit my application. I would also be willing to purchase ready-made packs of 2 36v batteries that would fit in 12" x 4" x 4", or better 11" x 3.5" x 4.5". I looked in items for sale, but didn't find any current listings for battery packs.

 

[nebriancent]

myself i would not charge a headway cell w/o a bms and or w/ a sla charger at all

first off if you are looking at spending 600-1k on a battery and not want to spend another 50-100 on a bms and less then 100 on a charger that will give you the plug in and walk away feature then all the power to you

a bms will constantly keep you battery balanced to not only extend its life but to help make sure you dont overcharge and destroy your new battery

next using a sla charger on a lithium battery can be dangerous and reckless especially w/o a active bms as the output is... lets say less then stable

but in closing if you want to babysit your batteries every time they charge waiting by w/ voltmeter in one hand and the charger plug in the other and at least once a week have to charge up the low cell groups w/ a stand alone 3.7v charger
then yes it can be done

but that being said the charger alone can speed up charge times dramatically as most sla chargers only put out a rated 2 amps(more like 1.5 from what ive found) making a 10 ah bat charge time 5hrs at best from 0% soc

 

[nebriancent]

btw if i was going to take the money i spent on a new battery and hold a match to it by using no bms and a sla charger

i would give my bats at least some protection by setting up a latching relay to kill the charger at a preset voltage

and then i would babysit them for the first few charges and at least once a week bring them all into balance by hand(wouldn't be fun)

best of luck in whatever you decide to do

 

[999zip999]

i think headway have problems getting balance out of the box sometimes. With a bms new. Where do you live ?

 

[The Mighty Volt]

You can charge anything you want with balance taps, a meanwell, a cell-log and a cheapo balancer. No need for a BMS, most of which are junk in the first place, the obvious exception being the generally well received Fechter-Goodrum variety.

You don't even need a balancer. You can use a PSU to balance your strings or individual cells via the taps.

The very notion that a Chinese-made PCB is better than the above mentioned tools is farcical. Use your eyes and basic tools to bulk-charge the cells or the strings, then start to balance them all off.

In short, you can charge LiFePo4 without a BMS. Yes.

 

[nebriancent]

all i meant by using a bms would be preferred by most is the set and forget of a bms

for a user that has overcharged at least one pack multiple times by what i am guessing is from not watching the charging/state of balance in the first place a bms may be the answer

your can charge any battery w/o a proper charger or a bms if you pay attention to whats going on so yes you can go without a bms but its not for everyone

 

[nebriancent]

and btw i meant no disrespect to others that chose to balance their cells manually

 

[dogman dan]

The same stuff we do with lipo should work fine. Bulk charging is an option as said above. So is using lipo chargers, by making strings of your headways in whatever number your charger, or multiple chargers can balance at one time. Lipo chargers have settings for everything, lifepo4, nicad, etc. Even if you go the bulk charge method, having an RC lipo charger is a good idea. Ideal for charging one cell at a time when you want to do manual balancing. Nice sure shut off at the voltage you want. No overcharging because you got distracted while watching small chargers work. You could bulk charge most of the time, but then still charge and balance shorter strings easy with an RC charger.

Don't use the sla charger with no bms, that only worked because you had a bms.

And if goes without saying you'll need a good way to monitor pack voltage, wattmeters or CA's are a great starting point. And with balance wire plugs accesible, you can always carry a cellog 8 to check the individual cell voltage at any time.

 

[999zip999]

Plus buy one extra cell for luck.

 

[electricridefl]

Thanks for the replies. As far as I understand , the charging profile for lifepo4, which is a battery much different than lipo, right?, sla vs. lifepo4 is the same type of charge, except the end I suppose. Anyway, is the F&G bms available for sale? I have some chinese bms for 72v. It ain't worth a ....My 72s nimh 86v batteries are still hanging in there with several bad cells in each battery. I am moving, and then my round trip commute will be 20 miles, from 6 miles presently. I charge 2 86v batteries and use one on the way to work, and the other home. I'm not fond of using cardboard covered batteries in the rain either. I would have to carry 8 chargers, extension cords, powerstrips, timer back and forth with me. The size of the chargers is bigger than the batteries. then I could run my same battery type, and buy a new battery for $180 for the 3.8ah cells. Maybe my nimh will last if I remain careful to not get them too hot. Ideally, I'd prefer to run more lifepo4 cells to where I can flirt with the 100v mark, like I'm doing now. Anyway, I wonder if anybody in this forum has 72-99v battery systems for sale, that is, custom build a couple of high voltage packs 4ah or so. My other option is to buy a car and commute with that. I should keep my eye on this forum for ideas...I really enjoy riding my bike. One of the best things you can do to stay healthy into old age is to keep your legs moving. I sure would love to have passenger capability for shuttling the elem and middle school kids to and fro. That would really be convienent. I've decided not to do the lifepo4 sans bms for now. Maybe another couple of 10ah 36v ping batteries. They did better than any battery I ever had.

 

[999zip999]

A higher ah rating helps battery life and gives the battery some headroom. So as not to kill it early.

 

[hillzofvalp]

there is nothing wrong with getting a balancing charger like a 1420i and charging up to 95-100% SOC, just might sacrifice 0-3% useable capacity.

 

[parabellum]

I constantly overcharged my pings more so to the end of their life. They did all swell up. And they heated up. I puncturd all the cells with a needle, and then drove them some more. No lvc or bms. The ping battery kept going.

Everyone is a way to go if you don't overcharge, over discharge or puncture lithium batteries. BMS and dedicated charger just make those tasks easier (everything but puncturing).