Victron 500ah Smartshunt and Fogstar Drift Lithium batteries

[Al n Val]

hi everyone I have 2 x Fogstar Lithium 280ah batteries in parallel so obviously only one negative going to sources , do i need a shunt for each battery or will the Victron 500ah shunt handle both batteries I have the Drift app on my iphone but both BMS’s show different stages of charge/discharge Fogstar tell me that it’s normal as it’s a difference in the BMS and not the batteries and they also recommended 2 x Victron shunts cheers and finally does anyone have one for sale or know the best price for one atm KS Energy are coming out at £83.88 Allan

 

[Lenny HB]

You only need one shunt as the batteries are in parallel.
The Fogstar batteries & BMS's should sort themselves out after a few cycles.

Our own RogerIvy will probably be the best price with Funster discount.

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[funflair]

As Lenny says just one shunt but on the -ve that feeds the consumers of course, we have 4 batteries and one shunt, well actually two as we have the original Buttner that came on the van and an additional Victron one as I didn't believe the Buttner, and yes they report different %state of charge until 100% but the Victron is the most accurate

 

[Al n Val]

thanks guys

i’ve emailed RogerIvy waiting for a reply

The Fogstar Drift BMS’s are working fine but the differences in each one drives me mental

Al

 

[autorouter]

It might be worth checking that the two batteries are wired together optimally. The two positives should be linked with substantial wire, at least the same thickness as the supply wires. Same with the two negatives. Check that the terminals are tight. You could check with a multimeter that the voltages across the two batteries are identical.

Then check that the positive supply wire goes to one battery, and the negative supply/shunt goes to the other battery. If you do that, the voltages across each battery will be equal even with small voltage drops in the cable due to high amps. It ensures that the two batteries are always charged exactly equally.

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[RogerIvy]

thanks guys

i’ve emailed RogerIvy waiting for a reply

The Fogstar Drift BMS’s are working fine but the differences in each one drives me mental

Al

Hi Al

Replied to you via email.

Just to make sure I understand one thing, you know that if you have two batteries you should/could use only one shunt to make it appear as a single battery to all intents and purposes?

On another note, even identical batteries report “different versions of the truth” in terms of SOC (state of charge) and it can drive one mad trying to understand. Add a shunt to the equation and for your sanity you’ll need to ignore the different SOC and rely on the shunt. The other thing to note is that if the shunt has incorrect setup it will be far out - a badly configured shunt is less accurate than the BMSs.

What Autorouter said is also very important, and when you get that right at least the voltages should be the same even if the SOC aren’t.

Rog

 

[bigtwin]

What’s the maximum discharge current that the BMS in each battery can handle and what size inverter do you have fitted?

Ian

 

[Al n Val]

What’s the maximum discharge current that the BMS in each battery can handle and what size inverter do you have fitted?

Ian

hi Ian

the Fogstar drift batteries have a max discharge of 200A per battery and my inverter is a Giandel PSW 2kw

Al

 

[bigtwin]

hi Ian

the Fogstar drift batteries have a max discharge of 200A per battery and my inverter is a Giandel PSW 2kw

Al

As others have said, a 500A shunt is ample. You’re not going to challenge that with a 2kW inverter and your LiFePO4 batteries will limit your draw to 400A in any case.

Ian