Lithium question?/

[weldted]

Hi all, we have had the following fitted

 

*4 x 175 watt solar panels, Victron mttp 60 amp controller

• Victron 2Kva Multi

• Victron GX touch control panel

• 230 amp upgraded split charge

• Victron battery protects for the charge and loads

• Victron Cerbo control system

• Victron BMV battery shunt

• 2 x Transporter Energy batteries

 

We are fortunate to have a large garage at the bottom of our garden to keep the van in. There lies a small problem. As it is in the garage no solar benefit. I have fitted the original 100 watt panel that came with the van on the roof of the garage and fed it via the buzz bar into the van. Obviously at this time of year it does not keep up with the 0.7 amp hour draw this system uses to power the mifi, monitoring,tracker and the parasitic current draw. Would you keep the van permanently on hook up and let the Victron float charge the batteries? Or let it rundown to say 60% soc and then bring it back up to 80% as I understand it is best to not keep these batteries fully charged if you are not using the van.

[spirou]

As it's a victron system I'd plug it in and use custom charge parameters to keep the battery anywhere between 50 and 80%

[ColinM50]

Can't see why you want to go to the bother of rigging up another solar panel on the roof unless you haven't got mains in the garage.

 

I keep my m/h in the garden and leave it plugged in all year and run it on a cheap mech timer for a couple of hours a day and if it's really cold, I'd put a fan heater on for a couple of hours too thought tbh it's never really that cold

[weldted]

The van is kept in an insulated garage so the cold weather is not much of a problem. If I wanted to I could just leave the power on no problem. But you get so much different opinions re lithium just looking for the best practise.

[mikefitz]

Its highly likely the Victron BMV needs the settings modified for your system, so until you have more experience on the relationship between the BMV readings and the actual SOC, it may be prudent to use battery voltage to estimate battery SOC, perhaps in conjunction with the Bluetooth application.

 

Its very difficult to stop charging at 80% state of charge. One solution would be using the AC charger with the usual absorption voltage of 14.2 to 14.4 volts, and with a float at 13.30 volts, and re boost at 0.1 volt less than float. This will initially charge fully and slowly discharge. The float power input will supply loads and will keep the battery at around 70% SOC. 0.05 volts can make a difference, so depending on calibration and experience, the float value may be needed to be adjusted slightly.

 

When the van is put into full service the additional loads will pull down the volts below the re boost voltage and a charge to full will occur.

 

Tests have shown shallow charge and discharge may create a memory effect in the battery, that will in reduce its working capacity. Full capacity is restored by a full charge and discharge.

 

I may have made the comment before, but care should be taken with Victron battery protects used as programmable protection switches between inverters or inverter chargers and the battery. They are single direction devices and cannot handle the surge current taken by inverter input capacitors.

https://community.victronenergy.com/questions/63134/why-can-i-not-use-a-smart-battery-protect-between.html

 

Mike

[weldted]

Thank you for your replies, as this installation was a serious chunk of change I will not be altering any settings. The 100 watt panel I fitted on the roof of my garage has reduce the discharge to virtually nil given it is heavily overcast today and no input overnight for now will leave well alone. When the capacity drops to around 50% will just turn the charger back on. Hopefully before not too long we will be able to get out and about. So far from collecting the van it was just a trip home ven in our garage and thats it.

[silverback]

lithium are best left if not used in a semi charged state ie. 50% taken out and left on a bench, but as you are discharging with alarms etc I would keep an eye on them and switch charger on every week or 2 week depending on the discharge, if you google storing a lithium battery it will tell you more

Jonathan

 

[weldted]

Thank you for your advice, these batteries are fitted one under each front seat protected by a Kevlar shrouds, so not easily removed. I did not want this system installed in the gas locker, one although we have a gas tank, LPG pumps are getting a bit thin on the ground. Also the gas locker is not the most secure so do not fancy loosing the batteries and possibly the Victron. So all installed internally.

[weldted]

Just an update, we have been in France since 17th of March, we have covered around 4000 miles temperature between -3c near Mont Blanc and 38 near Roxanne. Currently at an aire outside temp 31C sitting with the hab air-con on (much scratching of heads by other motorhomes as no mains available at this aire.) not needed ehu once have found that even with only 2 x 100 amp lithiums during the day when the sun is out can run the air-con for around 4 hours or as it is now running it at 20c can get the van cool for the evening. Big chunk of change but in my opinion worth it.