Charging off grid batteries from grid power

[drewski]

Hi everyone, wondering if I can get some ideas on charging my 12v AGM battery bank from the grid. I have a small off grid system setup and would like to be able to charge my system from my grid power when the solar panels cant keep up during the winter. In the past I put a battery charger on the batteries and that would work but it would throw off my battery monitor. Is that because I hooked the negative direct to the battery and should have hooked it up to the shunt? Can i have a battery charger charging from the grid and solar panels charging at the same time?

I have also heard people using laptop chargers and hooking direct to their charge controller. I read this might not be good with an MPPT controller but there could be a work around with diodes?

I would like to avoid buying any new hardware if I have to, but I am open to suggestions.

Thanks

 

[Zil]

For the monitor to have whatever accuracy it can have, all loads and charging must go through the shunt.

 

[pollenface]

I have used an 18v AC-DC power supply in parallel to the panels with an MPPT controller, no problems in 4 years.

 

[PHoganDive]

As Zil said, ALL charging and discharging must go through the shunt so it can be measured. The only thing connected to the battery end of the shunt should be the battery (and the measurement wire to the meter, which is high impedance to measure voltage across the shunt). All other connections should be on the other end of the shunt.

 

[Hedges]

You may be able to put a DC supply through diodes to the PV input of your charge controller. With low enough voltage it won't deliver anything except when PV voltage is low.

If you are drawing power at night, cycling the batteries, this could also stop that so cycle life is saved for power outages.
Direct to battery, perhaps a lower charge voltage would accomplish the same - load support, but not providing power when PV is available.

 

[gtstricky]

Yes, you can have multiple charge sources. The charger is a perfectly acceptable method. Just shunt it.

 

[Oad]

I want to do exactly the same. Since I want to have an automatic low maintainance system, I wonder how one can pull this off.

Can I attach the ACDC in parallel with my panels? I think that does not make any sense. I currently would go for putting a relay in front of the batteries, so that they are either charged by the solar panels or the ACDC charger. Any ideas on this?

@Will: Can you perhaps make a video for a solution like this?

With corona going on and - at least in Germany - the risk of a power outage is getting higher and higher - I think this topic will be of interest for a lot of people.

Thx Arnold

 

[Steve_S]

To those people looking to use a Battery Bank with an Inverter and desire Grid Power Charging either use as a UPS for circuits or for Usage Shifting of TOU (Time of Use) Rate, have a Look at the Samlex EVO Series of Inverter/Charger. Programable, built in ATS (Auto-Transfer Switch) some have Dual AC Input for Genset AND Grid input as well.

Samlex America: Samlex America -- Products
Samlex Europe Pure Sinewave Inverter-C/W Transfer Switch Archives - Samlex

 

[Zil]

I have a ProNauticP charger and TriStar Solar charge controller. The play well together.