I have a 2-amp, 4-amp, and a 5-amp charger for my Super73S1 eBike. Through meticulous data collecting an analysis I’ve made very interesting correlations between expected charge time versus actual charge time.
2 Amp Charging
This is a standard charger that comes with most eBikes and is available from Super73 for $80. If I rode my ebike with its 48V 14.5Ah battery until it ran out of power, it would take about 7 1/2 hours to charge back to full. From all my data logging I found that my 2 Amp charger actually does it in less time being anywhere from 10-15% quicker! But before I start painting a picture let’s go over the stats on the rest of my chargers
5 Amp Charging
This is the fast charger that came with my Super73 eBike, but is also available from their website for $150. Although this charger can charge over twice as fast as the standard charger, in practice it was definitely less efficient. To charge my 14.5Ah battery completely it should theoretically take a bit shy of 3 hours. In practice I found that this was not the case. On average the fast charger would take 35-50% longer to charge than it should which was very surprising; charging my battery from 50% should only take 1 hour and thirty minutes and on average took an additional 30-45 minutes! We’ll get into this more later.
4 Amp Charging
I found a 4 Amp charger for my eBike at a VERY economical price. I bought a $40 charger from Amazon and then chopped the proprietary plug for Super73 eBikes and soldered it to the charger. Although I haven’t had this charger long, I’ve used it enough to measure its efficiency. Doing the math my 14.5Ah battery charging at 4-amps an hour should take about 3 hours and 40 minutes. On average this one charges and balances the battery 5-10% faster!
Head to Head
For this example we’ll assume the battery is charging from 50% (7.25Ah) and compare the estimated charge times to the actual.
(estimated charge time :: actual charge time)
Standard Charger (2A)
3 Hours 38 Minutes :: 3 hours
Fast Charger (5A)
1 Hours 27 Minutes :: 2 Hours 10 Minutes
Aftermarket Fast Charger (4A)
1 Hour 49 Minutes :: 1 Hour 27 Minutes
In Short, the slow charger isn’t REALLY that much slower compared to the fast charger (at least in my case)
What does this all mean?
Absolutely nothing! I’ve always been in the practice of only using a “fast” charger on group rides where charging is available. All other times I will use my 2 Amp charger. Charging at a high rate causes the battery to heat up and anytime the battery experiences heat for long periods of time you’re hurting the battery, but it definitely shortens the lifespan of the battery albeit by a small amount.
I believe is my battery pack were larger or newer, the 5-amp charger would become end being the most efficient. I’ve now switched to taking my 4-amp charger with me everywhere because it’s quicker, more efficient and because I can plug it in to 110V and 220V outlets (more on that soon).
Things to consider
The rate at which you can charge really depends on a two things: your Battery Management System and how thick your charging wires are.
Your BMS plays a big role in your bike. It balances the individual cells that make up the pack, it prevents over-charging your battery, prevents the individual cells from getting too low, so on an so forth. Another thing the BMS does it determines how fast the battery pack can charge.
In order to charge at 5 Amps, the BMS must be spec’d to allow it. If you tried to charge a battery pack equipped with 2-amp limit on the BMS with a 5-amp charger, the BMS would either shutoff to prevent damage to the battery pack, or in the case of a really cheap BMS, the BMS itself would burn out. In order to charge a battery pack with a 5-amp charger, the BMS on the battery would need to specify a charge rate of 5 Amps or greater. Most Battery Management Systems in PEV battery packs can handle up to 10 Amps unless otherwise stated on the battery pack. Check for specs on your BMS or check with the PEV manufacturer to be sure.
Other than the BMS charging specs, the wiring for the battery pack’s charge port need to be the correct gauge. Most battery manufacturers plan over-head when making battery packs in that they’ll use a wire that is thicker than it needs to be (i.e. BMS can charge at 10 Amps, charging wires can handle 15, charger charges at 2 Amps). I assume this is done to take into account inferior chargers or even unstable electricity in your house. If the charge wires inside the battery pack are too thin it’s likely they would heat up, melt, and potentially brick the BMS.
This chart goes over what gauge wire is correct for different charge rates:
In short, if you want to be able to charge faster, make sure your BMS can handle a faster charge rate , and make sure the charge wires in the battery pack can keep up! I prefer to use 12 gauge wire for the charging cables in my battery packs. That gives me a good margin of safety no matter how fast I charge my bike or how dirty the power from the wall is or how crappy or potentially broken my charger is.
Chargers I’m a big fan of are the smart chargers offered by Luna Cycles as well as the Grin Technologies Cycle Satiator. I’ll go into more depth about these chargers as I use them more, but a great feature these chargers offer over other smart chargers is their ability to adjust the charge rate as well as how much they’ll charge your battery. Undercharging your battery is a whole topic of it’s own with it’s own pros and cons, Look forward to future posts about these chargers.