Solar + alternator + LiFePO4 setup for car camping with e-bike

[zombieexpo]

Hey all,

Would love to get your thoughts on a solar and battery setup for camping with an e-bike and small fridge.

At most I will ride the e-bike once per day. I'll use the stock 110v e-bike charger, which draws 2.5A and completes a full charge in 2.5 hours.

We drive a lot so I'd like to tie into the vehicle's alternator for charging. I'm thinking of doing:

• 400W rooftop solar
• 150AH LiFePO4 battery
• Victron 100 | 20 solar charge controller
• Victron 24 | 24 DC/DC charger
• 600W pure sine wave inverter

If my math is right, the LiFePO4 could safely charge my e-bike 3+ times without solar input. With solar, the panels should replenish an e-bike charge in a few hours.

What do yall think, have I over or under-designed this?

 

[Dave in AZ]

Why 24 24 charger? Is your car and alternator system 24v? Is your proposed battery and system 24v?

You need to specify the voltages of both, it's the most importand design info after all...

150Ah at 24v is twice as much power as 12v, so it makes a huge difference.

Additionally, that bike page doesn't list the battery voltage, size, or charger specifications. Most ebikes are 48v, and can be more efficiently charged off a dc-dc booster. Then you wouldn't even need the inverter.

The dometic fridge, probably 35W average is safe, due to on off cycle, so 840 Watt-hrs per day.

Ebike, it doesn't list battery size, but I'm guessing 800 Watt-hrs is safe. So you need 1600 Watt-hrs or so. A 12.8v 150Ah battery is 1900 Watt-hrs, which would be good.

If for some reason your alternator is 24v, first, where the heck is that? But if both battery are 24v, then it all looks good, except you only need 1600 Watt-hrs, a 100Ah 24v battery is like 2500 usable Watt-hrs, plenty. Also, a 600W inverter works, but is pretty wimpy. More than you need if just charging ebike with 110v. But if you want to run an electric kettle that doesn't totally suck time, you need 1000W. I don't know prices, but I wouldn't waste $ on 600W inverter, I'd go 1000W or 1500W for truck camping. Power needs always creep upwards! But yeah, if trying to save $ and all you really do is charge bike, 600W inverter works. Also uses less wasted power.

 

[zombieexpo]

Why 24 24 charger? Is your car and alternator system 24v? Is your proposed battery and system 24v?

You need to specify the voltages of both, it's the most importand design info after all...

150Ah at 24v is twice as much power as 12v, so it makes a huge difference.

Additionally, that bike page doesn't list the battery voltage, size, or charger specifications. Most ebikes are 48v, and can be more efficiently charged off a dc-dc booster. Then you wouldn't even need the inverter.

The dometic fridge, probably 35W average is safe, due to on off cycle, so 840 Watt-hrs per day.

Ebike, it doesn't list battery size, but I'm guessing 800 Watt-hrs is safe. So you need 1600 Watt-hrs or so. A 12.8v 150Ah battery is 1900 Watt-hrs, which would be good.

If for some reason your alternator is 24v, first, where the heck is that? But if both battery are 24v, then it all looks good, except you only need 1600 Watt-hrs, a 100Ah 24v battery is like 2500 usable Watt-hrs, plenty. Also, a 600W inverter works, but is pretty wimpy. More than you need if just charging ebike with 110v. But if you want to run an electric kettle that doesn't totally suck time, you need 1000W. I don't know prices, but I wouldn't waste $ on 600W inverter, I'd go 1000W or 1500W for truck camping. Power needs always creep upwards! But yeah, if trying to save $ and all you really do is charge bike, 600W inverter works. Also uses less wasted power.

Whoops! You're right, here's the 12/12 dc charger.

Regarding the bike, I know technically it would be more efficient to charge with DC. However, I'm hesitant to stray from the bike manufacturer's provided AC charger, as that's designed to keep the bike battery healthy.

So that's why I listed the bike charger specs (110v, 2.5A, 2.5hr) rather than listing the dc bike battery specs.

Good call on the inverter too. Here's a 1000W inverter that has good reviews.

Thanks for the advice - hugely appreciated!

 

[zombieexpo]

Whoops! You're right, here's the 12/12 dc charger.

Regarding the bike, I know technically it would be more efficient to charge with DC. However, I'm hesitant to stray from the bike manufacturer's provided AC charger, as that's designed to keep the bike battery healthy.

So that's why I listed the bike charger specs (110v, 2.5A, 2.5hr) rather than listing the dc bike battery specs.

Good call on the inverter too. Here's a 1000W inverter that has good reviews.

Thanks for the advice - hugely appreciated!

Hey Dave, I got some more info for ya

The bike battery is listed at 17.5Ah @ 40V, so if my math is right that's 58Ah @ 12V.

The fridge is 8.2A at 12V, so assuming 1/3 up-time for 24 hours, that's 65Ah @ 12V.

So do I simply add up those amp hours 58+65=123Ah?

If that's correct, sounds like I should be looking at a 200Ah battery.

 

[Dave in AZ]

Hey Dave, I got some more info for ya

The bike battery is listed at 17.5Ah @ 40V, so if my math is right that's 58Ah @ 12V.

The fridge is 8.2A at 12V, so assuming 1/3 up-time for 24 hours, that's 65Ah @ 12V.

So do I simply add up those amp hours 58+65=123Ah?

If that's correct, sounds like I should be looking at a 200Ah battery.

Ah is a terrible unit, if you're gonna convert then do it to Watt-hrs, which is universal no matter the voltage. So...
17.5 Ah @40V is 700 Watt-hrs.

Fridge. 8.2A @ 12V is 98.4 Watts.
In 24 hrs, that is 2362 Watt-hrs, and if you assume 1/3 actual run time it is 780 Watt-hrs.

Add them together, 1480 Watt-hrs. That's what you need for 24 hrs and 1 bike charge.
A 100 Ah battery is 12.8v, 1280 Watt-hrs.
So yeah, a 150Ah would work, but a 200Ah with 2560 Watt-hrs would be better.

Also gives you some slop.
You're going to want to run more stuff...
LED lights, 50W for 6 hours 300 Wh
Phone charge, x2, 30 Wh
Diesel heater 10 hrs, 250 Wh.
Maxxair vent fan, 10 hrs, 100-300 Wh
2 cups coffee, elec kettle, 90-130 Wh
Heating blanket, 5 hrs, 250Wh
Tablet, 4 hrs, 250Wh

Batteries are very cheap and small, 100Ah for $200 now. Might as well.

400W solar is a good recharge rate. And a dcdc charger from alternator, 25 to 30A, is say 350 to 420W. Between those, plenty of charging for your system. You can do separate devices as you spec, or get combo solar controller and dcdc charger. But your victron plan is really the #1 best if you can afford. Separate devices gives better reliability and ease and cost of replacing if needed.

Basically, it's a very solid car camping plan. if you got a 200Ah 12.8v battery, the victron 12 12 30 charger, and a 1000W inverter/charger, you'd be set. The inverter charger lets you run power either way, you can plug into AC in garage and it will recharge batteries, or it will take battery and output 120v. Smaller and better bang for the buck than getting a separate charger, I think. Victron has one, expensive. But the best stuff, and they all talk together. I might get this kisae one instead if saving a bit

BIC122080 – Kisae Technology Inc

An alternative would be a power station. A great one for your needs for truck camping is the Oupes Mega2.

 

[zombieexpo]

Ah is a terrible unit, if you're gonna convert then do it to Watt-hrs, which is universal no matter the voltage. So...
17.5 Ah @40V is 700 Watt-hrs.

Fridge. 8.2A @ 12V is 98.4 Watts.
In 24 hrs, that is 2362 Watt-hrs, and if you assume 1/3 actual run time it is 780 Watt-hrs.

Add them together, 1480 Watt-hrs. That's what you need for 24 hrs and 1 bike charge.
A 100 Ah battery is 12.8v, 1280 Watt-hrs.
So yeah, a 150Ah would work, but a 200Ah with 2560 Watt-hrs would be better.

Also gives you some slop.
You're going to want to run more stuff...
LED lights, 50W for 6 hours 300 Wh
Phone charge, x2, 30 Wh
Diesel heater 10 hrs, 250 Wh.
Maxxair vent fan, 10 hrs, 100-300 Wh
2 cups coffee, elec kettle, 90-130 Wh
Heating blanket, 5 hrs, 250Wh
Tablet, 4 hrs, 250Wh

Batteries are very cheap and small, 100Ah for $200 now. Might as well.

400W solar is a good recharge rate. And a dcdc charger from alternator, 25 to 30A, is say 350 to 420W. Between those, plenty of charging for your system. You can do separate devices as you spec, or get combo solar controller and dcdc charger. But your victron plan is really the #1 best if you can afford. Separate devices gives better reliability and ease and cost of replacing if needed.

Basically, it's a very solid car camping plan. if you got a 200Ah 12.8v battery, the victron 12 12 30 charger, and a 1000W inverter/charger, you'd be set. The inverter charger lets you run power either way, you can plug into AC in garage and it will recharge batteries, or it will take battery and output 120v. Smaller and better bang for the buck than getting a separate charger, I think. Victron has one, expensive. But the best stuff, and they all talk together. I might get this kisae one instead if saving a bit

BIC122080 – Kisae Technology Inc

An alternative would be a power station. A great one for your needs for truck camping is the Oupes Mega2.

That all checks out with me. Wh is a lot cleaner for this, thanks for converting. I guess the automotive batteries speak in Ah because they assume 12v everywhere.

The Oupes power bank looks great. Obviously the self-contained power bank design has big advantages. My question with those is can they be charged from alternator?

I know GZ used to sell a car charging kit, but it was $450 and seems discontinued.

 

[Dave in AZ]

That all checks out with me. Wh is a lot cleaner for this, thanks for converting. I guess the automotive batteries speak in Ah because they assume 12v everywhere.

The Oupes power bank looks great. Obviously the self-contained power bank design has big advantages. My question with those is can they be charged from alternator?

I know GZ used to sell a car charging kit, but it was $450 and seems discontinued.

They can all take a 12v dc input, but usually limited to 100-120W. Sometimes they use a car cigarette port which is just 10A max, so 120W.

it depends on the power station how else they might charge. If you have an inverter on truck already, you can use that to plug in either the station if it will accept that usually mod sine wave power, or a power supply then the station. Here is a thread here I made for that, and 2 videos I made showing how I skip using a dc to dc charger in my Tacoma, by using the existing bed inverter.

Using Tacoma Truckbed inverter to supply a power station, despite Modified Sine Wave AC power

Truckbed Inverter use to supply a Power Station, and video. Applicable to Tune M1, OVRLND, and other canopy or wedge campers for an easy power recharge option. Was msging with someone today about 3rd gen Tacoma, power stations, and how to use the truckbed inverter to supply one. I know...

forum.expeditionportal.com

Some power stations have a solar input that will take 12V, you can feed alternator power in there by using a dc to dc converter to give a nice steady power. Cheaper than a dc dc charger as you don't need a smart charging circuit, the power station already has one.