Jump to content

setting up BMV700 for battery capacity. query


frygood

Featured Posts

Hi Guys 

 

I have changed my Batteries and i want to know what to set my bmv ah rating at.

i have 3x 130ah batteries = 390ah

I have been told by 2 different people i should use the C20 rates which are

3x 117ah=351ah

So my question is do I set the BMV to 390 or 351

please be gentle with me.

 

Many thanks Carl 

Link to comment
Share on other sites

2 minutes ago, frygood said:

Hi Guys 

 

I have changed my Batteries and i want to know what to set my bmv ah rating at.

i have 3x 130ah batteries = 390ah

I have been told by 2 different people i should use the C20 rates which are

3x 117ah=351ah

So my question is do I set the BMV to 390 or 351

please be gentle with me.

 

Many thanks Carl 

If your batteries are not brand spanking new, then they will have lost some of their capacity.

You 1st need to do a capacity check and then set the BMV to your actual capacity.

Link to comment
Share on other sites

18 minutes ago, frygood said:

HI Alan

 

Thanks for the reply.

My batteries are brand spanking new. 1 day old now

so what is the answer.

 

 

I don't use anything as vulgar as lead acid batteries (!!) so am not really in a position to reply with certainty...

However the 'sales' capacity quoted is theoretical and not actual -  that's a 'no' for the 390 Ah.

The C20 rate is a much more sensible capacity - but it still overstates the actual capacity available as nobody charges as C/20. For now I'd set it at the C20 capacity -

Until somebody else comes along with a better / good reason...

 

Methinks most folks watch the actual charge current at any given time and stop charging when the charge current goes down to - say-  5 amps.

That's what I do with my WSOBs.

Link to comment
Share on other sites

It’s pretty much irrelevant what you set it to. If you get it right this week it’ll be wrong next month, it simply has no way to track the steady loss of capacity of the bank.

 

Determine fully charged by watching the charge current and decide when to start charging either by voltage if you’re experienced in doing so, or with a SmartGauge if you’re not. 

  • Greenie 1
Link to comment
Share on other sites

I'm with 'im ^^^^.  I'd set it to 350 now and maybe 300 later on, based on nothing better than a wet finger - other folk's guesstimates may appear here shortly.  The percentage charge figure on these meters is a progressively worsening wild-assed guess anyway and will steadily lead you into trouble should you rely on it.

Link to comment
Share on other sites

Agreed. 350 or 390 Ahr, it doesnt matter. The accuracy of the SoC calculation is not that good to see a difference.

Use the voltage and Amps in/out and Ahrs to monitor your batteries. I wouldnt trust SoC more than +/- 10%. Just ignore it.

Ahrs out and voltage at rest (or nearly at rest) tells you how discharged you are, and Volts/Amps in tells you how near 100%  SoC you are.

Even the Ahrs out can be dubious to know if you are 100% charged unless you have set all your parameters correct.

Edited by Dr Bob
Link to comment
Share on other sites

12 hours ago, WotEver said:

It’s pretty much irrelevant what you set it to. If you get it right this week it’ll be wrong next month, it simply has no way to track the steady loss of capacity of the bank.

 

Determine fully charged by watching the charge current and decide when to start charging either by voltage if you’re experienced in doing so, or with a SmartGauge if you’re not. 

I agree. The SoC measurement on all shunt based meters is fairly pointless. I don't bother with it on my BEP 12v monitor. I use off-load voltages and my smartgauge. The 12v monitor is mainly useful for looking at amps in/out of the domestic bank and voltages on 3 different banks.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.