question

merav avatar image

BMV-700 is showing fuller capacity than the voltage suggests (possibly wrong as much as %30) I need to know how to sync it properly.

My BMV-700 is showing fuller capacity than the voltage suggests (possibly wrong as much as %30)

I need to know how to sync it properly.


My system is a 24v solar

Victron Easy solar 24/1600 inverter

2 x Rolls Batteries S12-290AGM 12V 260Ah (C20)

Victron Battery Monitor BMV-700


System has been in place for a year, I have noticed the BMV SOC is wrong over the past 2 months.


My sync parameters are as follows :

1.Battery capacity – 260 Ah

2.Charged Voltage – 29 V

3.Tail current – 4%

4.Charged detection time -10 minutes

5.Peukert exponent -1.25 (default)

6.charge exfficiancy factor – 95%-(default)

6. current threshold – 0.1 A (default)


question 1 ?are any the parameters needs changing ?


Possibly i need to sync the BMV again, my understanding was the unite sync itself by bringing it to %100 charge twice a month.

My question 2- can I sync it manually(using the buttons) any time or is the solar system need to be at a particular stage for syncing?


BMV Battery Monitor
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1 Answer
Alexandra avatar image
Alexandra answered ·

@merav

AGMs are generally not 95% charge efficient. They are usually more like 80 or 85 depending on age. Capacity also drops over time. You may have to tweak the settings a bit again if you are still getting drift. Each battery bank is different.

The second thing is you can manually synchronise the bmv at full charge in the app using the bluetooth dongle. But you need to be sure it is at full charge, in other works not drawing any current for charging even though it is available.

The other mistake made is often that the battery starts synchronized it on. When the battery is not charged when connected to the bmv at first.


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Thank you @Alexandra My AGMs are one year old. The tail current was %4 for most of the time, so I will take it back to this setting.

I dont have the Bluetooth dongle, but I can manually sync the the BMV using the buttons on it, only when it is fully charged and floating.

How often Should I sync manually per month?

can I do any harm by doing it too often ?

thank you

@merav

Once the settings are right usually no manual sync is necessary. Are you using the same charged voltage on your multi?

I will check the charged voltage on the multi to make sure it is the same.

Has it got a default charged voltage?

I think I need to physically unscrew the front of the multi and connect my laptop to find what its been set to (which I havenot done before) .

Thank you for explaning that once the setting are right, usually no manual sync is required.

I Have synced yesterday and the SOC is looking more curate now.

Has the SOC ever been accurate?

I believe it has been accurate over the summer months.

having said that i did trust the SOC reading without checking the voltage as well, I only realised i have a problem when in November the multi started to cut off beacouse of low battery while the SOC on the BMV was 75%-65%.

Thank you very much @Alexandra