EV VRLA for offgrid use

[GeorgeF]

A part of an island in a tropical country has no grid and few small houses need basic lighting (with some leds). Ofcourse there are no true deep cycle batteries available in such area.

In the capital VRLA batteries as per attached pict are avalaible. According to the description such batteries ( 2Hrs rating) are also used in electric bikes.

Estimated daily consumption:
2 x 5w led x 6 hours = 60Wh
3 x 3w led x 2 hours = 18Wh
1 x 5w led x 2 hours = 10Wh
Charge gadgets = 12Wh
Total 100Wh

Battery VRLA 20Ah with 50Wp panel.

Question:
Can anyone estimate if this 20Ah VRLA with daily consumption @ +/- 50% DOD, dc-dc load thus no inverter, will last 3 years ?

[Mike90250]

Only half the battery capacity is usable, or it's cycle lifetime will be greatly reduced, so 12V x 10ah = 120 watt hours usable. So, yes, it will just barely be able to supply that load. You will be discharging to 41% of capacity daily, however that brings it's lifetime to about 600 cycles. The last 100 cycles will be shorter and shorter as the battery fails and looses capacity.
I would plan on a year of good use (365 cycles) and then expect to replace it anytime after that.



DoD_vs_CycleLife.gif

[SunEagle]

On top of the few cycles you get at 50% discharge, that battery is only rated 20Ah at 2 hr. I seriously doubt it will get you 100wh at 50% discharge.

[GeorgeF]

On top of the few cycles you get at 50% discharge, that battery is only rated 20Ah at 2 hr. I seriously doubt it will get you 100wh at 50% discharge.

Thanks for the above replies.

They have also other VRLA products. Unfortunately I can not find info about their life cycles on their websites.

If you only can choose one of their vrla products will you choose one with low or higher internal resistance for a offgrid setup as described above.

http://samotoindonesia.com/en/batteries/12-volt/smt1220-4-34-detail

[GeorgeF]

Examples

[SunEagle]

Examples

The problem with those batteries is that they are designed for EV bikes or other small vehicles that discharge rapidly.

Unfortunately you are looking for a battery with a 20 hour 40Ah rating to safely get your 100wh per day usage.

[GeorgeF]

That's a pitty. Cause with some friends we want to setup a social project (donation) for some houses there, cause they are still using kerosene lamps.

We will evaluate the costs....thanks SunEagle

[SunEagle]

That's a pitty. Cause with some friends we want to setup a social project (donation) for some houses there, cause they are still using kerosene lamps.

We will evaluate the costs....thanks SunEagle

Some simple calculations would be to use the battery voltage x the Ah rating x 25% as a safe daily discharge for FLA type batteries.

Once you have the battery system sized for your daily needs then you can size your solar panel wattage and Charge controller.

[GeorgeF]

The problem with those batteries is that they are designed for EV bikes or other small vehicles that discharge rapidly.

Unfortunately you are looking for a battery with a 20 hour 40Ah rating to safely get your 100wh per day usage.

One more question.
How is it then when riding an E-bike and using such kind of battery? High discharge with short duration like UPS thin plates Telecom batteries ? Or are these EV lead acid "hybrid batteries" like GolfCar with thicker plates ?

[Mike90250]

No idea what kind of battery it is internally.
It has an unusual 2 hour rating for it's 20ah (20hr is usual)

[SunEagle]

One more question.
How is it then when riding an E-bike and using such kind of battery? High discharge with short duration like UPS thin plates Telecom batteries ? Or are these EV lead acid "hybrid batteries" like GolfCar with thicker plates ?

I am wondering if those batteries have Lithium chemistry in them. That would allow them to have a high discharge % which is pretty typical of EV bikes and cars.

While that may allow you to use a smaller battery then a standard FLA type it still may not provide the watt hour needs after a years worth of cycles.

[azdave]

Anyone notice the printed info on the lower right corner. Company claims "smoothly approved" to ISO standards.

http://samotoindonesia.com/en/batteries/smt1220-4-34-detail

fetch (2022×3192) - Google Chrome 10192020 15349 PM.jpg

[Mike90250]

I suspect those batteries are about a robust as they need to be, to resist a pack of matches being dropped (unlit) on them. I have little faith in them.

[GeorgeF]

No idea what kind of battery it is internally.
It has an unusual 2 hour rating for it's 20ah (20hr is usual)

Before printing perhaps they phoned and the secretary of the boss said @ his "private home" 2 hours

2 american researchers did a survey on china's e-bike batteries and according to them they usually perform a C/2 discharge test.

It is indeed unusual to have a 20Ah 2 hrs rating. Most likely typing error.

Another example, attached pict .... not 20Ah but 20Wp

[GeorgeF]

No idea what kind of battery it is internally.
It has an unusual 2 hour rating for it's 20ah (20hr is usual)

2 americans did a research on china's EV-bike-vrla-batteries.