question

mrdias avatar image
mrdias asked

Should i use a Battery protect with Smart MPPT and LifePO?

Hi, I see some builds over the internet that have a battery protect between the MPPT and Battery connected to a BMS (all victron). Is this really required? Doesnt the MPPT stop the charging if voltage is set right on the MPPT settings?

I have set the MPPT battery to LifePo but i havent test if it works, i am afraid to go over the voltage.


Thanks

MPPT ControllersLithium Battery
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1 Answer
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

To prevent overcharging you should use a "VE.Direct non inverting remote on-off cable"(ASS030550320) and connect it to the "charge disconnet" terminal of the BMS and the VE.direct terminal of the MPPT.


4 comments
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mrdias avatar image mrdias commented ·

Thank you for your reply, so the MPPT on its own will overcharge the battery even tho its set to lithium?

I am already using the VE.direct cable to the Color Control and i am already using the charge disconnect for the starter battery relay.

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ mrdias commented ·

Normally the MPPT should stop charging by itself at 14.2V.

But if there is some kind of failure in a cell and the BMS says "stop charging", the MTTP have to be turned off.

If the VE.direct terminal is already in use you maybe should use a Cyrix-li-charge(or Battery Protect) to cut-off the MPPT or you connect the MPPT to the starter battery.

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mpptcutoffbp.png (505.7 KiB)
mrdias avatar image mrdias Matthias Lange - DE ♦ commented ·

If the BMS is giving 12v on the charge disconnect port untill it cuts it incase something is wrong, cant we connect more than 1 batery protect in paralel in that charge disconnect port?

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ mrdias commented ·

We done this successfully a few times.

I don't know why VE has rated the charge disconnect only for 10mA and the load disconnect for 2A(miniBMS 1A).

IMHO this should be changed asap. In many cases you need to cut-off more then one current source.

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