Battery Fuel Gauge [RE-wrenches]

[Ezra Auerbach, DragonSun Consulting]

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Hi Todd,

A point of interest to all might be the new Apollo T80 www.apollo- 
solar.net). They have incorporated a SOC meter into their controller.  
I've been using one and although the SOC firmware is still a "work in  
progress" it shows some promise. (I don't work for them).

Ezra





Ezra Auerbach
DragonSun Consulting
Providing Marketing Services for the Renewable Energy Industry
Lasqueti Island, B.C. V0R 2J0

ezra at lincsat.com
250 333 8650



On 2-Nov-06, at 7:18 AM, Todd Cory, Mt. Shasta Energy Services wrote:

>
> Self discharge equates to inefficiency, which is calculated by the  
> meter every time the batteries reach a full SOC. In an ideal world,  
> this is compensated for by the meter the next time the batteries  
> are charged.
>
> If the displayed amp hours is a positive number when the batteries  
> reach the charged parameters, the meter recalculates the battery  
> efficiency lower. If the displayed amp hours is a negative number  
> when the batteries reach the charged parameters, the meter  
> recalculates the battery efficiency higher. So if the meter has  
> calculated the batteries at, say 90% efficient, the shunt must pass  
> 11 amp hours to count up 10. This should adequately compensate for  
> self discharge.
>
> The only problem I see with this is in the winter, when the  
> batteries can go many charge/discharge cycles without ever getting  
> to the charged parameters. In this scenario any meter error gets  
> compounded and inaccurate. I commonly get calls from customers in  
> the winter that say "my meter says my batteries are discharged, but  
> the generator/solar will not charge them". This is one of the rare  
> instances where looking at battery voltage can reveal the problem,  
> where the batteries are actually more charged than the meter says.  
> If the charge controller or inverter's charger talked to the meter,  
> this issue could be avoided. So far no one makes a amp hour meter  
> that will communicate with the system charge controller or inverter  
> charger.
>
> Another system that might perform better would be an electronic,  
> temperature compensated specific gravity meter with a sensor/probe  
> in the battery electrolyte. It would undoubtedly be a messy (yet  
> accurate) way to measure battery SOC, but could not be used on AGM/ 
> gel batteries.
>
> Todd
>
>
> Bob-O Schultze, Electron Connection wrote:
>
>>
>> Of course, the problem with all shunt based metering, Link 10,   
>> TriMetric, etc., is that they can't see self-discharge as it  
>> doesn't  pass over the shunt.
>> That's probably as much a concern in a standby system as anything  
>> else.
>> Bob-O
>> On Nov 2, 2006, at 5:29 AM, Todd Cory, Mt. Shasta Energy Services  
>> wrote:
>
>
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