Another off grid charging question

[Dmurphy48]

I want some folks to check my math on a solar set up I have. The main question is how much of my 100 ah leisure battery will be used when charging my 700 wh Levo battery. I am using the standard 4a Levo charger hooked to a 700w pure sine wave inverter which is then hooked to my 100 ah battery. Converting my Levo battery to ah it is about 20 ah. I know there are losses in the system but it would seem I could easily charge the Levo battery twice before 50% safety threshold of my leisure is hit. I have read other statements and recently watched one of EMBN videos where they said you could barely charge a 500 wh battery with a 100 ah leisure battery. Thoughts?

 

[Al Boneta]

@levity you want to chime in on this?

 

[levity]

Hi Al ?
Yes @Dmurphy48 a 100Ah Li-ion battery operating at 12V should do it, but not twice.

Assuming that the solar set up is 12V the 100Ah battery is theoretically capable of providing up to 1200Wh. (Watts = Amps x Volts)
To fully charge the Levo's 700Wh will require ~800+W due to losses in the inverter and charger.
Assuming his leisure battery is Li-ion which can safely discharge ~80% that makes ~960W available.
That should be more than enough to recharge even a fully discharged 700Wh battery.

We use a portable Li-ion battery to recharge our bikes off-grid. The pic below shows our Goal Zero 1400Wh battery which after several years of use can still deliver ~1100Wh (enough to fully recharge two Levo SL bikes and their Range Extenders). We keep the Yeti charged from two 100Ah Li-ion batteries in our camper van and keep those topped up with two 100W solar chargers on the van roof (at least when the sun is shining).

 

[Al Boneta]

Hi Al ?
Yes @Dmurphy48 a 100Ah Li-ion battery operating at 12V should do it, but not twice.

Assuming that the solar set up is 12V the 100Ah battery is theoretically capable of providing up to 1200Wh. (Watts = Amps x Volts)
To fully charge the Levo's 700Wh will require ~800+W due to losses in the inverter and charger.
Assuming his leisure battery is Li-ion which can safely discharge ~80% that makes ~960W available.
That should be more than enough to recharge even a fully discharged 700Wh battery.

We use a portable Li-ion battery to recharge our bikes off-grid. The pic below shows our Goal Zero 1400Wh battery which after several years of use can still deliver ~1100Wh (enough to fully recharge two Levo SL bikes and their Range Extenders). We keep the Yeti charged from two 100Ah Li-ion batteries in our camper van and keep those topped up with two 100W solar chargers on the van roof (at least when the sun is shining).

View attachment 37969

Thanks @levity see you at the shop at 10

 

[wepn]

Hi Al ?
Yes @Dmurphy48 a 100Ah Li-ion battery operating at 12V should do it, but not twice.

Assuming that the solar set up is 12V the 100Ah battery is theoretically capable of providing up to 1200Wh. (Watts = Amps x Volts)
To fully charge the Levo's 700Wh will require ~800+W due to losses in the inverter and charger.
Assuming his leisure battery is Li-ion which can safely discharge ~80% that makes ~960W available.
That should be more than enough to recharge even a fully discharged 700Wh battery.

We use a portable Li-ion battery to recharge our bikes off-grid. The pic below shows our Goal Zero 1400Wh battery which after several years of use can still deliver ~1100Wh (enough to fully recharge two Levo SL bikes and their Range Extenders). We keep the Yeti charged from two 100Ah Li-ion batteries in our camper van and keep those topped up with two 100W solar chargers on the van roof (at least when the sun is shining).

View attachment 37969

as in awesome.

 

[thebarber]

I want some folks to check my math on a solar set up I have. The main question is how much of my 100 ah leisure battery will be used when charging my 700 wh Levo battery. I am using the standard 4a Levo charger hooked to a 700w pure sine wave inverter which is then hooked to my 100 ah battery. Converting my Levo battery to ah it is about 20 ah. I know there are losses in the system but it would seem I could easily charge the Levo battery twice before 50% safety threshold of my leisure is hit. I have read other statements and recently watched one of EMBN videos where they said you could barely charge a 500 wh battery with a 100 ah leisure battery. Thoughts?

I went for a Dc-Dc charger with solar input aswell.
I've got a 270w panel which does keep my 2 130ah batteries topped up but just ticking the van over boosts the batteries by 50ah so charges in no time at all.
Here's the charger...

ABSO DMT1250 12v 50amp BATTERY to BATTERY CHARGER + SOLAR MPPT

Top quality off grid 50amp battery to battery DC/DC charger with solar mppt for up to 500 watt systems offering a top the best battery maintaining system for your vehicle. Suitable for all vehicles plus modern Euro 5 & Euro 6 smart charging systems Recommended for any 12v vehicle

www.simplysplitcharge.co.uk

 

[thebarber]

This might help you with calculations....

Solar Calculator

www.bimblesolar.com

 

[OldGoatMTB]

Assuming his leisure battery is Li-ion...

I would not assume this at all. A great many people are still using lead acid batteries which should only be discharged about half. Also, assume a 15% loss in the inverter.

 

[Dmurphy48]

Yep, it is a lead acid battery. Should have been more clear. With that said I will appreciate some clarity on why levity used watt hours on my leisure battery to figure out how much of it would be used vs amp hours? My theory based on nothing but guesswork was that I am using a 4a charger for the Levo battery and it takes about 5 hours to charge the Levo battery so I use about 20 amp hours of a 100 amp hour battery. This somewhat matches that the Levo battery is about 20 amp hours (700 wh/36v=19.4 amp hours). Since I can use about 50% capacity of my battery that means I have 50 amp hours to play with. Obviously these two calculations don’t match and it does seem wrong that I would be able to charge my Levo battery twice but I would like to better understand why these two ways of figuring out the same problem are so different. Thank you

 

[steve_sordy]

Power is measured in watts
Energy is measured in watt-hours [so many watts delivered over one hour (or twice as many watts in half the time)]
One Watt = 1amp at 1volt
One Watt-hour = one Watt delivered for one hour.
So a 100Amp hour battery at 12 volts can deliver (potentially) 100 x 12 Watts of power for one hour. ie 1200 Watt-hours. More likely it will deliver 10Amps at 12 Volt for ten hours.

Take into account the various energy losses, efficiencies etc and you get what levity said.

 

[Dmurphy48]

Maybe this explains it better for me. I was thinking 4a for 5 hours is 20ah of battery use but I guess that is wrong. The specialized charger is 4a at 42v (not sure why this is 42v when the battery is 36v but I will leave that to a different discussion) so 168W. Now if I run that for 5 hours to get a full charge I am at 840 watt hours which with inefficiency and inverter loss correlates better to what is being said (probably closer to 1000 watt hour). So with lead acid batteries and keeping to 50% safety margin I probably want two 100 ah 12v batteries connected in series as that would provide 2400 wh and I probably need 1000 watt hours to cover a full charge safely.

 

[bluewater87]

I have a 1350VA/810W pure sine wave ups (APC BR1350MS).
My trek rail battery is the bosch 625wh.
The bosch battery charger specs are i/p:[email protected], o/p:36V@4A (i am in north america).

Can i use this UPS to charge my bosch battery, and if so, how many times will it charge the bosch 625wh battery before the UPS battery dies?
Can i charge two e bike batteries simultaneously?

TIA

 

[Jeffrey]

I have a 1350VA/810W pure sine wave ups (APC BR1350MS).
My trek rail battery is the bosch 625wh.
The bosch battery charger specs are i/p:[email protected], o/p:36V@4A (i am in north america).

Can i use this UPS to charge my bosch battery, and if so, how many times will it charge the bosch 625wh battery before the UPS battery dies?
Can i charge two e bike batteries simultaneously?

TIA

I'm sorry, you cannot use this UPS to fully charge ebike batteries. It's too small

By looking at the APC website you can see it has an internal battery of 168Wh. Considering the transformation losses (UPS battery -> ebike battery), you can charge one 625Wh battery only to ~20%.

 

[OldGoatMTB]

I have a 1350VA/810W pure sine wave ups (APC BR1350MS).
My trek rail battery is the bosch 625wh.
The bosch battery charger specs are i/p:[email protected], o/p:36V@4A (i am in north america).

Can i use this UPS to charge my bosch battery, and if so, how many times will it charge the bosch 625wh battery before the UPS battery dies?
Can i charge two e bike batteries simultaneously?

TIA

It's hard to say exactly as their is power loss in converting from battery power to AC, but I think you could safely charge 2 batteries at once. Quick done-in-my-head math says you may or may not get 2 full charges, but not much more. This is assuming you have a lithium battery. If it's lead-acid then you only want to discharge the battery 50%, so only 1 charge to be safe and not destroy your ups battery. I assume it has a safety circuit to prevent it from killing itself, though.

OOPS! I didn't see the earlier response and was assuming the 1350VA (whatever "VA" is) to mean 1350 watt-hours. Can basically just disregard everything I said above.

 

[Jeffrey]

OOPS! I didn't see the earlier response and was assuming the 1350VA (whatever "VA" is) to mean 1350 watt-hours. Can basically just disregard everything I said above.

Haha, I made exactly the same mistake before checking the APC website

 

[Nickolp1974]

i used 127ah charging my 504wh shimano batteries 3 times, i have 2x 180ah batteries in my camper. No solar yet but thats coming in a month or so.