Lithium without BMS campervan set up correct?

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longgun asked Jul 12, '19

Lithium without BMS campervan set up correct?

Hi

I am designing a system with x2 lifepo4 138ah 'powerwalls' which I bought without BMS. I am going to keep a close eye on the state of cell balance of the lifepo4's through a separate Battery Capacity Meter plugged into the 4s and balance charge them as necessary.

My system comprises the following - 300w panels, 100/20 victron smart solar mppt, victron multiplus 800/35 inverter charger, 712 battery meter, sterling B2B charger and victron battery protect.

I found the following schematic from a fellow member which Im thinking to use its pretty much the same as my own.

My question is will x1 battery protect be ok (keeping an eye on the discharge) and if so where is the best place to place it? Directly from the battery?

Im a complete newby and if this schematic is good I would use it.

Many thanks for all your help!

Lithium Battery BMS Battery Protect monitoring schematics

3739-victron-lithium.png (129.6 KiB)

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klim8skeptic ♦ commented · Jul 12, 2019 at 09:10 PM

"My question is will x1 battery protect be ok (keeping an eye on the discharge) and if so where is the best place to place it? Directly from the battery?"

Battery Protects can not be used in a situation where the current will flow in both directions, ie the inverter/charger. (one BP cannot be used for chargers and loads)

Seek further advice.

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longgun klim8skeptic ♦ commented · Jul 13, 2019 at 08:49 AM

Many thanks klim8skeptic ..... yes Im aware of this.

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Modifications Space

Node Red Space

Answer 1 · 2019-07-13T07:59:12Z

kai answered · Jul 13, 2019 at 07:59 AM

If I were in your position I would try to really understand the schematic, how the system works and be comfortable with your skillset before attempting something like this. You're looking at a sizeable investment - installation mishaps can cause substantial damage to the equipment (and potentially people).

I can see at least a few issues/omissions with the schematic, and the idea of this in combination with using LiFePo without BMS and no experience makes me very nervous.

If you're set on the idea of DIY, at least start small and have all the basics squared away first.

Sorry. I don't think this was the answer you were expecting.

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longgun commented · Jul 13, 2019 at 08:52 AM

Thankyou Kai. I will take your advice and try to work out how the system works first.....

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