lithium battery source/price thread

[tanglewood]

Originally Posted by john61ct

I just meant that "amp hour" is precise

many people claim (does wiki still?) that Ah means "amp per hour"

which to me is not precise.

An amp as an average current flow, running **for an hour** or **over the period** of an hour, yes that is precise.

Noobs see a device nameplate rating of 4A draw at say nominal 12V, and think "that means it will use just under 100Ah every 24 hours".

In fact, power demand may vary greatly within each hour due to many factors, ambient temperature affects duty cycles for example, so in reality that device only uses 25-40Ah per day in moderate circumstances.

Using "amps per hour" or "watts per hour" is just plain confusing, and IMO should be struck from polite society.

Not really.


An amp is an instantaneous measure of current. There is no time element.


When you integrate it over time you get amp-hours which is equivalent to a steady 1 amp over 1 hour, but can actually be arrived at with arbitrary combinations of current and time.



And if a devices nameplate rating is 4A @12V, it is often very reasonable to predict just under 100Ah*V energy use per day. The operative assumption is that the current is constant, and whether or not that's true depends on the device. I think that's your point about the common noob mistake. Actual consumption is the integral of I*V over time.





If you want to talk about imprecise language, or short hand, it's referring to Ah as a unit of energy. Implied is the " times Voltage" part of the equation that turns it into energy.

[john61ct]

> An amp is an instantaneous measure of current.

Yes absolutely, but both amp and current mean a flow **rate**

Ah and Wh are like gallons, the static quantity of energy, while watts and amps are like "fluid ounces per second"

which is why

> There is no time element.

is precisely wrong!

Amps **do** already include the element of time, in the denominator of

one coulomb **per second**.

As Watts is defined as Joules **per second**.

Ah as you say are integrating, or accumulating, or totalizing that flow **rate** over time, as the amps rate is often fluctuating within the time span.

X amps **for** Y hours, so yes it seems "a bit like" regular multiplication

40A for 15min = 10AH

AH per min/hr/day is correct

but amps "per" min/hr/day makes little sense.

Ah (or Wh) are therefore required when you want to indicate energy usage over a period of time, or capacity of storage, at a given voltage.

____
Yes without the voltage you cannot calculate power from energy, so Wh are needed when a use case covers conversion, say discussing an inverter, both before (mains AC power) and after.

But Ah are a better unit than Wh when voltage is relatively constant, for measuring battery capacity, "Ah per time" better for load consumption, and amps better than watts for carrying capacity of wire and other infrastructure.

To save time, the EEs here explain why, for those interested: https://electronics.stackexchange.co...of-watts-hours

[KTP]

It is some universal law or something that all internet threads will eventually devolve into either cat pictures or comparisons with Hitler. The center does not hold.

[ferrofan]

Originally Posted by Shrew

I love 'crowd funded' research. It feels a lot like. " I don't want to do my homeworl, just tell me what you found out when you did your research".

Why would anyone not think it a good idea to pool knowledge? If one person spends a weekend researching a topic they get a limited amount of reference material. If a thousand people spend a weekend researching the same topic and share the results - they have the equivalent of 19 years of weekend research - bit of a no brainer in my opinion.

[swampbush]

I am still looking for Lifepo4. I see these are on sale today in Australia for a lower dollar figure than the US price. When adjusted for our low dollar they are even cheaper. 170ah with 100amp bms for $1320 aus.

https://au.renogy.com/renogy-lithium...12-volt-170ah/

[denizati]

Have you looked at these guys ?
https://www.gsl-energy.com/
There prices seem very good. I am looking at 300AH unit and it is $1140.

[KTP]

Originally Posted by denizati

Have you looked at these guys ?
https://www.gsl-energy.com/
There prices seem very good. I am looking at 300AH unit and it is $1140.

Data sheets have quite a few errors...warranty would be 30 feet or 30 days...pass

[newhaul]

Originally Posted by KTP

Data sheets have quite a few errors...warranty would be 30 feet or 30 days...pass

just messaged manufacturer waiting on answer as I type

[Pitchondesign]

Found a quote for 12v 200ah, includes internal BMS for about $1,300usd shipped. Look at RUIXU battery. Never dealt with then. Apparently have some connection to Sinopoly battery.

[newhaul]

Originally Posted by Pitchondesign

Found a quote for 12v 200ah, includes internal BMS for about $1,300usd shipped. Look at RUIXU battery. Never dealt with then. Apparently have some connection to Sinopoly battery.

they are sinopoly

[john61ct]

I think it more likely they are just a reseller.

[Pete7]

Originally Posted by john61ct

And note there are also practical limits for paralleling these 4S / 12V drop-ins if increased capacity is needed try to buy units as large as possible, personally I try to stick to 3P, maybe 4 strings max in a pinch.

You are not making your posts very easy to read for anyone who has just joined Cruisers Forum (CF) or learning about lithium ferrophosphate (LFP). Perhaps instead of using abbreviations which some folk won't know, you write the less obvious ones in full. Or at least write them out in full first time followed by the abbreviation in brackets like: Amp-hour (AH).

Pete

[newhaul]

Originally Posted by john61ct

I think it more likely they are just a reseller.

John consdering you don't have Lfp house bank and I have talked with my sales rep at sinopoly Trust me the ruixu is sinopoly .

[newhaul]

Originally Posted by KTP

Data sheets have quite a few errors...warranty would be 30 feet or 30 days...pass

ok just got word back and the warranty period is 10 years. On those drop ins .

[john61ct]

Originally Posted by newhaul

Trust me the ruixu is sinopoly .

I am not saying the Sinopoly batts they sell are not genuine.

I am saying I do not think the company RUIXU is a subsidiary of the company Sinopoly.

Which is how I interpreted:

Originally Posted by newhaul

they are sinopoly