Battery Charging Strategy

Eclectic

1 kW
Joined
Aug 6, 2012
Messages
308
Location
Southern California (San Gabriel Valley)
Since watching “The Video”, I have been using what I call “Just-In-Time” (JIT) charging. I have 20Ah of 12s Turnigy hardcases. I normally keep the battery at storage voltage (3.8??). Just before I go to ride (on the weekends) I try to figure how long I will ride. Since both of my chargers are ~300w (Thunder 1220 & HLG 320) I try to charge for about 210% of the amount of time I figure I will be riding. That usually gets me back home with the battery at storage voltage again. This means I am always charging to a different voltage (4.15 is the max though) and it is difficult to keep good charging records. It does leave me with enough charge to ride a couple of miles during the week if I need to run to the market etc. In my mind, it helps me keep my battery healthy for a longer time (differing opinions are welcome).

The downside is, I have to drag out the bike (I always charge on the driveway) and put it on the charger for an hour or two before I can ride anywhere significant.

My current dilemma is, once the time changes, I will be commuting to work again (part of my commute is just too dangerous ride in the dark). Last commute season I would charge from 8-10:30pm and then put the bike in the garage (under a welder’s blanket) ~11pm (leaving the battery @ 4.15VDC for 8 hours). I am trying to come up with a strategy for charging my battery that is not as bad as leaving it at full charge all night but not hosing my whole morning.

My 2 questions would be:
1. Does my current strategy make sense?
2. Any ideas on how to have a fully charged battery in the morning without leaving it charged all night?
 
I've ended up doing exactly your strategy for the last year or so and it works out well. I've certainly had many more cycles out of my cheap hardcases than most. Now about 600 cycles of about 80% DOD

I charge with an Adaptto controller with an 1800w power supply, so I only need about 18 minutes to get the 500wh I require for my one way journey. I have another identical PSU located at work with a dedicated outlet. I was only really comfortable pushing my hardcases to ~2.2c. New battery is much larger and assembled from 18650's, I'm going to experiment with running both PSU's in parallel and charging at 3.5kw :twisted:

Key is to get a powerful charger. It's no fun dealing with a two hour charge.
 
Are you using a BMS? I can assure you, properly installed and vetted, it allows for more liberty in regard to "where" to charge. Personally, BMS/PCM recently saved a nice new pile of bricks when I'd left the controller ON while out of town. Cut-off well before damage to any cell.

I use these things practically everyday - you got about $330 worth of bricks and barring any LV/HV damage, they'll give you a good year or two, probably more whether you "baby" them much or not. I almost always do 20C hardcase quick charge up to around 4V/cell immediately following use which leaves me with only a few minutes 7A charge to top off, if needed for my next use/ride. Give tires and everything a good walk-around-look-see while it tops-off.

I only concentrate that everything's 3.8'ish if left "long-term". In fact, the reason I left my pack connected recently is because the last ride, 'left the cells about 3.85V/cell so instead of the usual "unplug/plug-in-charger". I merely "forgot" and left the controller powered-up. Thank you BMS...

If you play with battery packs as many of us do, you owe it to yourself to scavenge/construct a simple and effective "resistive load". Old toaster oven, space heater elements work great. If for no other reason than to drain off excess charge should you forget, plans change and/or you fail to "guess" right about next use before heading out of town for extended periods of time, etc.

A "test load" can also help realize benefits of IR testing and capacity measurements.
 
Never store or charge your RC lithium cobalt packs in a place you wouldn't build a fire. That welding blanket won't save your house burning down. A bms won't help if you have a cell with contaminants in it in your pack.

You could compromise on the charging time by charging to 4v the night before, then bring them to 4.2 in the am a bit quicker.

At some point, you have to choose practical lifestyle vs battery lifespan. For a daily commute, you should get a safer chemistry to store in your garage, then you could charge in the garage, using a timer to start the charge in the middle of the night.
 
BMS RC Lipo - don't knock it until you try it...
 
Edited my reply, that was picking a fight. Sorry.

But lipo is like nukes, don't trust em. Handle them careful.
 
Always much love & respect, my friend. Feel free to delete and clean-up any/all of this.

Totally valid - they're "nukes" in careless hands and un-informed hands. BMS is merely an extra layer of protection/convenience, not intended as a replacement for "mental BMS" requirement, imho.
 
Your batteries need a BMS. If it does not have a BMS then you cant leave them charge while you sleep or they could overcharge and start a fire.
 
I'm in agreement with both Ykick and Dogman here. You shouldn't be trusting Lipo for a commuter, you need a better, safer battery. A welding blanket will do nothing except direct most of the fire out to the side first. Have you seen my video of a single cell burning? Here, if you're curious: https://www.youtube.com/watch?v=NzUla1udKuA

But if you just have to use lipo this way, then using a BMS is highly advisable. It will not let you charge it unattended, but it will make it safer than it was.

Charging it as Dogman said would work: half at night before you crash out, the other half in the morning before you leave. It would be "better" for the cells than sitting at full charge. But if it was me, I'd just charge to full and leave it, accepting the reduced life in exchange for more sleep in the mornings. And when the battery dies, you can get something safer that could be charged over night.
 
I personally charge to 4.0 V lately for battery life and safety margin. I just have to carry enough battery to do that.

If any string of my 24S goes down to 0.0v while charging to 96V (though unlikely as they are 15Ah blocks), the other 23S can easily manage the overage (96V over 23 cells = 4.17 V). Even if 2 go out, I'm at 22S for 96V so that's only 4.3 V. And although you don't want to charge to 4.3 V, you're not to the fireworks stage yet as cells normally get to 5.0 V before the magic happens.

Using a Satiator, I charge overnight at, a very low, 60W. Over 8 hours that is ~480Wh, which is slightly less than I use on my commute. In the morning, if I decide I'm going to ride really far, I'll charge it to 100V.

Mostly the same at work, but I charge at 150W or so and towards the afternoon. I mitigate the charge risks by using low termination voltage, low charge wattage, cell-level alarms, and regular pack inspection including cell-level checks.


OP: To your point #1, your charge regimen seems well though out and seems to work for you.

To point #2, If you charge in a safe place and use a calculated low wattage charge to 4.0V overnight, you could then do a quick top to 4.2V in the morning as suggested by Dogman
 
I think it's not so much a bms issue, as it is trusting the cheap ass cells in RC lithium cobalt packs. With or without bms, I would never recommend charging them in a garage while you sleep.

This pain in the ass factor, is the main thing making cheap RC packs so unsuitable for a daily commute. You need a chemistry less likely to flame IMO.

You need a pack from EM3ev, allcell, etc. Which btw, are bms equipped.
 
I charge my LiFePO4 standard hardcase with the smart charger that came with the bike, but i put it on a cheapo wall timer so when it starts chargeing about 5 hours before I go to work so it doesnt sit there all night at full charge. Ive been using it for 2 years now and have 600-700 recharges on it and it is still getting at least 20 miles a charge.
 
With a bms equipped and somewhat safer chemistry pack such as your lifepo4, using a timer to start the charge in the middle of the night is quite convenient. The (metal?) case your battery is in should help improve safety if your battery should short internally, vs a flammable battery bag.

But if you had lithium cobalt RC packs, you'd never want to risk putting them on a timer to charge while you sleep. Unless they were out side, or in some kind of truly fireproof location. I charge my RC packs in a fireplace, but still would never consider sleeping while they charge.
 
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