Is an advertised 100Ah solar lead acid that weights 18Kg (39 pounds) realistic?

[rin67630]

I have bought such a battery and gets the impression that the advertised capacity was badly exaggerated.
Is the ratio Weight/Capacity of such a battery realistic?

 

[snoobler]

Very unrealistic. My 150Ah trojans weight about 85#.

 

[gnubie]

A storage 12V AGM would be around 30kg at 100AH capacity. A 12V 'deep cycle' flooded battery, ie something entirely inappropriate for use as a storage battery, is around 16kg at 100AH capacity.

If these are actually 12V AGM storage batteries at 18kg I'd expect them to be around 60AH.

 

[rin67630]

It is that model: apparently a flooded battery, sold with that alleged characteristics:

• 20% more cycles than a conventional solar battery - deep cycle -
• Over 600 charge / discharge cycles according to DIN
• Higher loading capacity and enormous energy throughput
• Optimized for photovoltaic systems
• Very deep cycle supply battery with reinforced lead cells

I probably got a plain cranking battery and have been fooled by an unserious vendor isn't it?
The vendor has however sold according to eBay more than 2500 batteries and got plenty of positive evaluations...

 

[gnubie]

Charge it up fully, do a discharge test and that will tell you the amp hour rating it really has. It still may not be appropriate as a storage battery but at least you'll know the actual AH rating and can go from there.

The weight doesn't lie though. A 100AH 12V storage battery is around 30kg, AGM, flooded, GEL. Storage batteries have much heavier plates than cranking batteries.

 

[snoobler]

The vendor has however sold according to eBay more than 2500 batteries and got plenty of positive evaluations...

I suspect zero of those people took the time or even had the equipment to actually test the battery to its rated capacity.

It's also possible they aren't using the C20 rating. I have a 122Ah battery from Walmart... 122Ah @ 1A... Pffft.

 

[rin67630]

I suspect zero of those people took the time or even had the equipment to actually test the battery to its rated capacity.

It's also possible they aren't using the C20 rating. I have a 122Ah battery from Walmart... 122Ah @ 1A... Pffft.

I have done that.
Here are the figures over a couple of days. The battery was in operation and daily put at absorption until ten days of really bad weather discharged the battery to 11,5V.
The load was only 500-600 mA, even less than C200.
The subsequent charge was at 1-3A max, without load.

ts	AhBat[26]	voltageAt23:59h
2020-09-25T22:00:01.767Z	0.14​	12.69​
2020-09-26T22:00:01.755Z	-5.86​	12.59​
2020-09-27T22:00:01.513Z	-4.11​	12.47​
2020-09-28T22:00:01.526Z	-8.45​	12.41​
2020-09-29T22:00:00.792Z	-9.56​	12.26​
2020-09-30T22:00:01.818Z	-1.31​	12.07​
2020-10-01T22:00:01.151Z	-7.11​	12.04​
2020-10-02T22:00:01.873Z	-4.15​	11.87​
2020-10-03T22:00:01.443Z	-9.20​	11.77​
Discharge	-49.62​	Ah
2020-10-04T22:00:00.469Z	8.52​	11.74​
2020-10-05T22:00:00.906Z	4.17​	12.04​
2020-10-06T22:00:00.950Z	15.84​	13.06​
2020-10-07T22:00:01.716Z	26.38​	14.08​
Charge	54.91​	Ah

 

[Delmar]

My favorite Harbor Freight 35AH AGM battery weighs 11kg, extrapolated to 100AH = 31KG. Decent heft for a low price.

 

[snoobler]

10.5V is the actual cut-off for an empty 12V, so there's probably more in there, and you didn't get it fully charged at 14.08V. Looks like @gnubie 's guess of 60Ah is pretty close if you assume C20.

 

[rin67630]

10.5V is the actual cut-off for an empty 12V, so there's probably more in there, and you didn't get it fully charged at 14.08V. Looks like @gnubie 's guess of 60Ah is pretty close if you assume C20.

I don't want to change my cut-off at 11,5V since I can't be sure to be able to recharge it timely.
There was probably 10% energy left, but on the other side, I discharged at C/200 only, that surely compensates for more than 10%.
The charge limit it is 14,4V for a short time. 14,08V was the absorption voltage at no-load, for max 10 hours, with enough sun, the mid of September looked like that:

 

[snoobler]

Ah. I remember that chart. Makes more sense why it didn't last longer.

 

[rin67630]

It's also possible they aren't using the C20 rating. I have a 122Ah battery from Walmart... 122Ah @ 1A... Pffft.

I just have read that the DIN standard specify following ratings
C/100 for the capacity of solar batteries.
C/20 for cranking batteries
C/5 for forklift/transportation batteries
C/3 for sealed batteries

 

[snoobler]

Still doesn't meet that.

U.S. convention for solar power systems is C20.