Charging Bosch E-Bike Power Packs from E21 Solar

[Catchlight]

When camping without 30W AC service, would it work to use the power from our 2014 model Escape 21's stock solar panel, dual 6V batteries, and inverter to charge our e-bike batteries between rides?

On AC at home, the usual charging time is two to three hours per battery.

Here are the battery specs:
Bosch Li-Ion 500Wh and 625Wh
36V / 13.4Ah
0275007906/915
Stock Bosch charger.

We only want to do this if it is efficient, safe, and advisable. Thanks in advance for your techniques and experience with recharging identical or similar batteries.

[Brian B-P]

It will certainly work, but it can (if you use the bike enough) take a lot of energy, and you might not have that much surplus.

By just plugging the stock Bosch charger into an outlet in the trailer, you'll be using the trailer's inverter to make 12 V DC into 120 V AC, then the charger to make 120 V AC into 36 V DC. If there's a charger specifically suited to these batteries which run from 12 V DC, it would likely be more efficient (less energy wasted) than the two-step approach; I have no idea if that is readily available, but for these bikes I think it's called a "travel charger".

[alanmalk]

Originally Posted by Catchlight

...
We only want to do this if it is efficient, safe, and advisable. Thanks in advance for your techniques and experience with recharging identical or similar batteries.
...

Safe? Quite likely, with the slim possibility of a ground loop, which should be evident in the first 10 seconds, look for smoke or blown fuses.

Efficient? No, for reasons outlined above. Double conversion from 12VDC to 110 VAC to 36 VDC will waste perhaps 15 to 30% of the total energy.

Advisable? Well, there are 2 approaches to this question.
1. Do the maths. Make assumptions about the energy produced and energy needed. For example, your stock solar, fixed position on the roof. Are you camped at 10,000 ft on the equator (where solar panels are measured) say, at Mt. Kilimanjaro, or are you camped at sea level in BC? Are you using other power like the furnace (a medium sized power hog)? Is it mid-summer or mid-fall? How discharged are the bike batteries. How much power is lost in the inverter, in the charger? Etc, etc. These assumptions get tedious and could be totally wrong at my end.

2. Try it out in a campground with power, just don't plug in. If it works, then great. If you have a dead battery at 3 AM when it is 5C and the furnace stops, then just plug in and make some mental notes.

All that said, I strongly suspect that if you ride and recharge every day, you won't have enough solar to replace what's used. Consider a portable panel you can point directly at the sun and double your input. Now you have some reserve if your fixed panel is in the shade, or if its cloudy, or you have a desire to ride into the sunset.

[Perry Butler]

Do you have a 110 inverter in your Tundra? We have/had a 400 watt inverter in our 2015 and 2019 Ford F150's. We charge our 500 watt Bosch batteries and/or 21 ah Shark batteries in the truck when driving down the road. Two batteries at the same time is the most we've charged at once, but we don't have to worry about discharging our trailer batteries.

If we didn't have an inverter in the truck I'd install one in your Tundar and know you're not draining your camper batteries.

Terry routinely gets about 100 miles on her 500 watt Bosch battery and I get around 80 miles on a charge, so we need to charge perhaps twice a week. We mostly hike when traveling with the camper, but in three months in Arizona last winter we rode slightly over 400 miles.

Enjoy,

Perry

[fudge_brownie]

I have tried and used for one year the above described method: solar to battery, battery 12 volt to inverter 120 volt, 120 volt back to 12 volt via the brick. It works but as described it is inefficent. I am using a 310 watt solar panel and dual 6 volt AGM batteries. It is a challenge for it to keep the dual six batteries charged for this process.

This past year I discovered another method. The issue is most of the buck chargers out on the market are 48 volt. Most eBike batteries are lithium and require a 54.6 volt charge. Finding the correct combination was very difficult. The model I am using was ordered from China. A friend found them and ordered two with expeditied shipping. With two weeks delivery they cost $80 each. Half the cost was shipping.

These still take a great deal of battery power and lots of solar. This device will draw about 15 amps when charging my largest battery pack. Now alot of variables come into play, how much charge the battery started with is the biggest. I found a battery with 1/4 remaining takes about 3 hours to charge. This does eliminate the inverter and the wasted energy. However, I found in previous tests this is only about 3 amps more draw.

It eliminates an inverter and it saves some battery. I will require a sunny day and at least six hours of sun for the charge and then full replenishment of the house batteries.

[Eggscape]

Originally Posted by Perryb67

Do you have a 110 inverter in your Tundra? We have/had a 400 watt inverter in our 2015 and 2019 Ford F150's. We charge our 500 watt Bosch batteries and/or 21 ah Shark batteries in the truck when driving down the road. Two batteries at the same time is the most we've charged at once, but we don't have to worry about discharging our trailer batteries.

If we didn't have an inverter in the truck I'd install one in your Tundar and know you're not draining your camper batteries.

Terry routinely gets about 100 miles on her 500 watt Bosch battery and I get around 80 miles on a charge, so we need to charge perhaps twice a week. We mostly hike when traveling with the camper, but in three months in Arizona last winter we rode slightly over 400 miles.

Enjoy,

Perry

Since we don’t stay long in one spot, this is what we do in our F-150.

[Catchlight]

Eggscape, that's a useful feature that Ford includes. Unfortunately, nine-year-old Toyota trucks don't have it.
Thanks, everyone, for your suggestions about this. I'm going for an e-bike ride today with a friend who has an E 5.0TA and just got a Honda generator. Maybe that's the answer for charging e-bike batteries when AC isn't available.

[John in Santa Cruz]

Originally Posted by Catchlight

Eggscape, that's a useful feature that Ford includes. Unfortunately, nine-year-old Toyota trucks don't have it.
Thanks, everyone, for your suggestions about this. I'm going for an e-bike ride today with a friend who has an E 5.0TA and just got a Honda generator. Maybe that's the answer for charging e-bike batteries when AC isn't available.

actually, my 2008 Tacoma TRD had a AC inverter. which I think I used *once*.

I carry a '400W' inverter (that I wouldn't trust with more than sustained 200 watts) and plug it into my E21's batteries via a powerpole, and use this for either the '48V' 1A charger for my wife's ebike, or the 52V 2A charger for mine (those are the battery nominal voltages, NOT the charger voltages). The 160W rooftop solar keeps the RV batts happy