Using Schauer Lead Acid Charger for 30C Lipoly

[deerfencer]

I just purchased 6 of those 8000mAh Zippy Flightmax packs for my Tidalforce S750X and have wired them in series, then parallel for a 37V 24Ah pack. The individual packs are rated 30C and I seem to recall a few posts on this forum regarding using lead acid chargers for lithium.

http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=16227

Bottom line: I have the following heavy-duty 110V Schauer charger with rated output of 36V at 22A. Would there be a problem using it to charge all three packs at once given that this would split the input to about 7A per 8Ah subpack or is this a bad idea? All charging would be done outside under close monitoring.

http://www.batterygiant.com/Battery-Chargers/Product/MLT22036

Any and all informed opinions welcome. Thanks in advance.

Larry Hayes

P.S. Anyone interested in getting the skinny on these packs for use on a TFX or other high-power e-ride should go to the Tidalforce Owners forum on Google where I've started a thread on them. Just three rides to date but pretty amazing performance with incredibly low sag--can you say .7V @ 1400W?!

http://groups.google.com/group/tidalforce/browse_thread/thread/8c9e33243a194282/92b157794a1bbf50#92b157794a1bbf50

 

[liveforphysics]

Technically, anything that can flow current into the pack can get lipo charged.

However, lead acid chargers don't terminate properly for lithium, and very bad things could happen, like your home burning down. I would strongly advise against it.

 

[auraslip]

LFP, correct me if I'm wrong, but it doesn't terminate properly because of the CV "topping charge" that takes a a few hours at the end of the the charge right? I understand that the biggest issue is individual cells going over their HVC, but if they didn't would this sort of CV trickle charge still damage the cells?

I've been using a 2 amp sla charger(more like 1.5 amps really) for the past month to charge my ping without a BMS. It's been a pain in the ass, but I've worked out a system. I guesstimate how many hours it will take to charge based on AHs used, and I make sure I'm around to unplug the charge as soon as the cell-log HVC alarm goes off.

Overnight charging is a bit more of a pain. Since I'm not there to manually terminate the charge, I do a very conservative guesstimate of how long it will take. Then I use a light timer to switch the charger off a few hours ahead of time. It sucks because I have to charge for an hour or two in the morning still, and even then the pack is in no way completely topped off.

So, you could use a light timer to shut off the charge at 45 minutes or an hour. OR you could do something like I'm working on building and use cell-logs to trigger relays to power down the charger. You could use latching relays to permanently terminate charging at HVC, but the pack won't be topped off or balanced. OR you could use non-latching relays and battery medics. The cell-logs will hold the relays controlling the charger OFF while any cell is over the HVC. The battery medics will discharge cells over HVC. I'm a bit iffy on how the battery medics actually function though, but essentially this is how a standard "bleeding" bms works.

This is what many people here are doing, but instead of using a meanwell power supply you are using a SLA charger.

 

[wesnewell]

If the output voltage of the 36V charger is more than 42V, then you need to monitor it while charging and disconnect it when it reaches 42V. If its charge voltage is 42V or less, then as long as all your cells are in good shape and in pretty good balance, you could plug it in and forget it. When the max charge is reached and the battery voltage equalizes to the same voltage as the charger it stops charging and will maintain that voltage till the charger is removed. I use a 48V sla charger that will charge to 60V (maybe more), but remove it when it reaches 59V. that give me a battery charge of about 58.75V for a 14s pack, which fully charged is 58.8V. One of these days I'll open it up and see if i can adjust the max output voltage down to 58.8V or maybe even a little lower. Just remember that if you need to monitor it and you forget about, the results could be disastrous.

 

[dogman dan]

I wouldn't use that thing and walk away. no reason though, you couldn't do a fast charge to a "safe" voltage, then move em over to something like a lipo balance charger for that last .2 v. But bear in mind, if that charger overcharges some cells, they could catch fire, or just puff and vent, later at an awkward time or place. So it's not just while charging that you have some risk.

My advice remains, if you want to build a pack and bulk charge, put 10 or so cycles on the things using a regular RC balance charger. Then build the pack for bulk charging out of known to be good packs.

 

[deerfencer]

Thanks for the replies. I have no real need for a super-fast charge, so for safety's sake will probably stick with my baby li-on 3A chargers, which will give me a full charge in about 2.5 hours if charge the (3) 8 Ah modules separately (I have 3 chargers). I guess I was just curious as to whether the LA charger COULD be used in a scenario where I needed a quick recharge. Sounds like it could but given the pack is brand new I'd just as soon err on the side of caution for now.

LH

 

[liveforphysics]

LFP, correct me if I'm wrong, but it doesn't terminate properly because of the CV "topping charge" that takes a a few hours at the end of the the charge right? I understand that the biggest issue is individual cells going over their HVC, but if they didn't would this sort of CV trickle charge still damage the cells?

If lead chargers ended in CV (and they dont), and the CV value was correct, and the lead charger was correctly regulated (99% are just a sheetmetal box of feces), then it could work. However, lead needs to maintain in a low current CC stage if you wish to hold it at 100% SOC (and balance the cells). This charge algorithm applied to LiPo just results in fire.

If you wanted to just dump some charge into your pack to quickly bring up the voltage, it would be fine as long as you're there watching it to prevent it from over-charging.

LiPo just wants a power supply. A standard regulated power supply that goes into CC mode when you pull it down below the regulated voltage, and as the battery gets enough charge in it, it just sits on CV forever, never needs to terminate, doesn't need any control or monitoring or algorithms, just a power supply.

 

[deerfencer]

liveforphysics,

CV stands for what?

CC?

Just want to be sure I understand your post.

Thanks for all the info, it's much appreciated.

LH

 

[Beavinator]

I believe CC stands for constant current and CV constant voltage

 

[kauaikit]

Larry...thank you for your postings on the Tidalforce forum. I noticed your first posting on the Zippy 18.5v 8ah batteries & took your lead & ordered two to test. And I've been reading your updated postings too.

I've got four TF ebikes, though all still are running the original NiMH front hubs. So, I thought I'd try them on the 4 EV Global ebikes I have, since they came originally with SLA batteries. Of course the two Zippies weigh in @ a whopping 5lbs, which reduces the weight by 15lbs.

I'm using a cheapy Chinese 44v/1.7amp charger while I babysit the batteries, hooked together, to 42v. And I'm using a lipo battery balancer (Common Sense RC $39.99) from the local RC shop to watch the cells in each individual 18.5v packs (4.2v +/- .05v)). I noted your not going below 36v, but I've read that 30v is the low limit. I've gone down to 33.5v when testing for range. I'd be curious if over or under charging these Zippies is more harmful or limits their long range use.

These zippies really wake up the EV 36v ebikes from 16.5 mph to 20.5mph. They use the heinzmann geared 500watt hubs & you really feel the power with fresh batteries. Very impressive battery upgrade solution for $180 that will work in all the ebikes.

I'm going to buy two (2) of the Zippy 37v/4.5ah for 9ah to use in the EV Global ebikes & then buy two of the Zippy 22.2v/8ah batteries to connect each one in series with the 18.5v (40.7v) & then in parallel for a 8ah brick for the TF bikes. My plan is to over volt each pack, & get 43.5v. It's my understanding that 44v is the limit on the TF ebikes, right? Your thoughts?

Kit
S.CA