RobDor wrote:

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Hi, a query on how something is supposed to work. New van for us (2015 model) and still working out a few things. When I have the van plugged into 240v, then I assumed the charger would charge my batteries ( I have 2 x 100ah Lithiums) regardless of whether my solar panels are also charging them, or am I wrong ? Or, does it prioritise solar charging over AC input ? Ive been away for 5 days, van is at home plugged into 240 and also solar panels are in the sun, everything is running, but my batteries are sitting at 20% charge and float light is on the AC charger. I thought the batteries would be at 100% being plugged into AC ? The Lithiums are new, AC charger set to Lithium modethis is the charger https://trailercamperaustralia.com.au/voltech-40a-240v-ac-12v-battery-charger-bc-1240p-1ap-anderson-plug.html

Any ideas what the go is ?  Cheers

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 https://www.manualslib.com/manual/1053443/Voltech-Bc-1240p-1ap.html?page=6#manual

There is a copy of your manual just in case you don't have one.  Do you have a multimeter to test anything.

Might be a dumb question Rob, but is it switched on? It might be on float charge from the solar input.

I say this because my charger was under the seat and items I stored in there pushed against the on/off switch without me knowing, charging only on solar.

Cheers Bob

This morning had a look before the sun came up and the charger is in float mode and just dribbling about 2amps to the batteries, even though batteries are only about 15% charged. Seems like its stuck in float mode. I powered off the charger, unplugged batteries (basically reset it all), plugged back in and powered up, charger cycled through and is now in absorption mode and pumping about 30amps to the batteries. For some reason it was stuck in float mode and not switching to the correct mode to charge properly. Will have to see if it keeps doing it.! It may be faulty, or it may need a different battery type selection?? Who knows. Thanks for your input.

Just checked, batteries at around 35%, but already in float mode, so something not right..

Aus-Kiwi wrote:

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What setting is the regulator set at ? Seems way lower voltage setting ? If there is one ?

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 From what I can see, you select battery type and that sets voltage levels etc. As per the manual, which is in a link in a reply above. 

How are you determining the SOC of the battery ?

If you are using a battery monitor, is it synchronised to read 100% when the battery is fully charged?

-- Edited by kgarnett on Saturday 27th of November 2021 02:44:14 PM

kgarnett wrote:

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How are you determining the SOC of the battery ?

If you are using a battery monitor, is it synchronised to read 100% when the battery is fully charged?

-- Edited by kgarnett on Saturday 27th of November 2021 02:44:14 PM

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 Batteries have smart BMS with Bluetooth that give SOC , voltage and charge/discharge current etc.

Hi Rob,
What brand of Li batteries are you using.

What is the battery open circuit terminal voltage as measured with a multimeter when the batteries are at say 20% or 35% SOC.

Terminal voltage is not a good indicator of SOC for LiFePO4 batteries because of the relatively flat voltage discharge curve, but can give some indication (eg 12.9V ~ 20% , 13.2V ~ 70%)

Do both batteries indicate the same or similar SOC by their respective BMS.

Are the individual cell voltages balanced.

The reason I ask is that I have experienced false SOC readings from the inbuilt Bluetooth BMS on my batteries. The BMS has indicated a very low SOC yet the terminal voltage and my Victron BMV 712 battery monitor indicated a high SOC which was confirmed by a load test at C20

As an aside it is not generally recommended to leave LiFePO4 batteries fully charged in storage nor on trickle charge. It is often recommended to fully charge the batteries, discharge to around 60-70% then totally isolate the batteries. Repeat every few months.

Ken

-- Edited by kgarnett on Sunday 28th of November 2021 08:43:36 AM

-- Edited by kgarnett on Sunday 28th of November 2021 11:11:01 PM

kgarnett wrote:

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Hi Rob,
What brand of Li batteries are you using.

What is the battery open circuit terminal voltage as measured with a multimeter when the batteries are at say 20% or 35% SOC.

Terminal voltage is not a good indicator of SOC for LiFePO4 batteries because of the relatively flat voltage discharge curve, but can give some indication (eg 12.9V ~ 20% , 13.2V ~ 70%)

Do both batteries indicate the same or similar SOC by their respective BMS.

Are the individual cell voltages balanced.

The reason I ask is that I have experienced false SOC readings from the inbuilt Bluetooth BMS on my batteries. The BMS has indicated a very low SOC yet the terminal voltage and my Victron BMV 712 battery monitor indicated a high SOC which was confirmed by a load test at C20

As an aside it is not generally recommended to leave LiFePO4 batteries fully charged in storage nor on trickle charge. It is often recommended to fully charge the batteries, discharge to around 60-70% then totally isolate the batteries. Repeat every few months.

Ken

-- Edited by kgarnett on Sunday 28th of November 2021 08:43:36 AM

-- Edited by kgarnett on Sunday 28th of November 2021 11:11:01 PM

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 ok thanks for the info. I haven't checked with multimeter, the BMS gives me voltage and SOC etc. both similar levels and voltages seem to be relative to SOC, i will check with meter see if it's accurate. Good to know about the cycling every few months. Might do that schedule every 3 or 4 months for battery health.