I am confused about how many amps in a C rate, if anyone can explain that again. Thanks.After getting the SiO2s late last year, I charged them to as full as they would get, which was at 14.6v with amps tapered to 0.5a /100AH same as ordinary AGMs spec. The SiO2 battery spec charging graph says they get down to "0.02CA" and then after more time to "0.01CA" as Full.Does that "0.01CA" for Full mean 1 amp per 100AH? If so, that is twice the 0.5 amps per 100 with ordinary AGMs.Meanwhile, after floating them at 13.3v--I picked that voltage as being not a full float in case I was not supposed to be floating them at all--still not sure about that whole thing--They got charged yesterday (as a spot check) at 14.6v and amps tapered on the two in parallel (200AH) to 0.2 amps and stayed at that for a time, so I went back to float at 13.3 for now.That is 0.1 amp each as their Full. Could "0.01CA" be a typo? When I had ordinary AGMs, I would see lower than 0.5a/100AH on them too.(I assume that time floating did them some good, since they now taper to 0.1 each instead of that 0.5 when I first got them. I think I will keep floating them between trips, never mind what Trojan says.)

my hobby batteries have a charge C rate and a discharge C rateone C is the amp hour capacity of your battery in amps it takes to charge in one hourfor example a 4 amp hour battery rated for 1 C charge can be charged at 4 amps and it should take about one houra 4 amp hour battery rated for charge at .5 C charge can be charged at (.5 x4 = 2 amps) and it will take about 2 hours

Once the curve goes flat you know they are full charge. I would spend minimum time at 0.2 amps and cut the voltage sooner than later.For storage (or even during use) you might even stop sooner such as 2 amps. I don't think you really need to cram them all the way to the top.Double check with the manufacturer or supplier.

C rating is a way to describe how much voltage drop and heat a battery will suffer. This example is opposite of RV batteries, but might help to understand. Some of those radio control drones use a tiny little 1amp battery with a 100c discharge rate. That means you can pull 100amps of burst power out of that super small little 1amp battery. There will also be a recommended charge C rating. Lets say the battery has a 5c max charge rate. For a 1amp battery you would want to limit charge to 5a or less. For your RV the math looks a bit differnt. Since your batteries are 100s of amps and it appears the charge C rating is a fraction like you posted. 0.01C rating for a 100a battery would be 1amp. Often the discharge C rating is much higher than the charging C rating.

The "C-Rating" is the term I used here (perhaps wrongly) to describe the "CA" number in the battery spec. Thanks for confirming "0.01CA" is 1 amp on a 100AH battery. (It is not the charging rate, but is what the amps will be down to after tapering down to "Full") These batteries can be charged to a max of 27 amps per 100 AH or about "0.27C" or "0.27CA" if I got that right.I would like to know more about why discharge rates are sometimes seen as way higher than spec charging rates. Why can't the batts accept as fast as they can discharge like Wets can (where the chemical change is just reversed between charging and discharging--same speed of change)?

I believe charging some of these chemistries will separate the electrolyte or plate chemistry.I know with lithium for example too fast will move the actual metallic lithium in the cell instead of just the ions.I assume SiO2 would have similar breakdown for moving things too fast.Otherwise we could charge an electric vehicle or your phone in 10 seconds for just applying more power.

Math is Hard-- C Rate ? | Good Sam Community

14 Replies

BFL13
Explorer II
Jan 31, 2021
The "C-Rating" is the term I used here (perhaps wrongly) to describe the "CA" number in the battery spec. Thanks for confirming "0.01CA" is 1 amp on a 100AH battery. (It is not the charging rate, but is what the amps will be down to after tapering down to "Full") These batteries can be charged to a max of 27 amps per 100 AH or about "0.27C" or "0.27CA" if I got that right.

I would like to know more about why discharge rates are sometimes seen as way higher than spec charging rates. Why can't the batts accept as fast as they can discharge like Wets can (where the chemical change is just reversed between charging and discharging--same speed of change)?
wopachop
Explorer
Jan 31, 2021
C rating is a way to describe how much voltage drop and heat a battery will suffer.

This example is opposite of RV batteries, but might help to understand. Some of those radio control drones use a tiny little 1amp battery with a 100c discharge rate. That means you can pull 100amps of burst power out of that super small little 1amp battery.
There will also be a recommended charge C rating. Lets say the battery has a 5c max charge rate. For a 1amp battery you would want to limit charge to 5a or less.
For your RV the math looks a bit differnt. Since your batteries are 100s of amps and it appears the charge C rating is a fraction like you posted. 0.01C rating for a 100a battery would be 1amp.
Often the discharge C rating is much higher than the charging C rating.
time2roll
Nomad
Jan 31, 2021
Once the curve goes flat you know they are full charge. I would spend minimum time at 0.2 amps and cut the voltage sooner than later.

For storage (or even during use) you might even stop sooner such as 2 amps. I don't think you really need to cram them all the way to the top.

Double check with the manufacturer or supplier.
roam1
Explorer
Jan 31, 2021
my hobby batteries have a charge C rate and a discharge C rate
one C is the amp hour capacity of your battery in amps it takes to charge in one hour
for example a 4 amp hour battery rated for 1 C charge can be charged at 4 amps and it should take about one hour

a 4 amp hour battery rated for charge at .5 C charge can be charged at (.5 x4 = 2 amps) and it will take about 2 hours

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Math is Hard-- C Rate ?

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