DC to DC charger and Solar at the same time

[StevieRuss]

I have a Victron DC - DC charger (bluetooth 30amp) charging two 120ah AGMs in our van. As i'm upgrading the solar on the roof (to around 400watts) I will be upgrading to a Victron MPPT charge controller (50amp) how can I be sure that the combination of the two charging systems whilst running at the same time (driving around obviously!) be over current for the batteries?

I was wondering if there is something smart about the two Victron devices that will somehow know when to restrict the current to probably 40-50amps or will disaster be avoided only by isolating the panels manually?

 

[sunshine_eggo]

Charging from multiple sources

One can have as many independent charging sources running concurrently as they like provided they are programmed properly for the voltage of one's battery bank. Examples (some or all at once, even multiples of a single type, different brands, etc.): Solar PV via MPPT Solar PV via PWM AC-DC...

diysolarforum.com

Most Victron MPPT allow you to limit the current below the max.

Some Victron chargers have a high and a low current setting.

400W of solar flat on a van roof will rarely put out anything near 400W (bad angle and high cell temps).

It's on you to determine how much how batteries can take and how to configure your charge sources.

 

[mikefitz]

You can set the Victron chargers for maximum output current if needed. 240 Ah of AGM will not be too worried by 50 amps charge current. Its farly easy to determing the battery status via the Victron app and turn the devices off ( via the app).
My guess is total charge current will be order of 50 amps.

Mike

 

[StevieRuss]

Thanks guys. That's very helpful

 

[StevieRuss]

400W of solar flat on a van roof will rarely put out anything near 400W (bad angle and high cell temps).

Yeah. Our current broken 100watt panel only gave an occasional 100 watts so I kind of thought the 400 may look a bit overkill but it's to make the most of what they won't manage to achieve in an ideal world

 

[HRTKD]

If you get the right Victron components, they can be networked and that can allow those devices to coordinate on the maximum output current. It's a bit of an upgrade from the usual Victron equipment. I'm using a Cerbo GX to do that.

 

[StevieRuss]

If you get the right Victron components, they can be networked and that can allow those devices to coordinate on the maximum output current. It's a bit of an upgrade from the usual Victron equipment. I'm using a Cerbo GX to do that.

I was just reading about those. Maybe a bit over kill for my system though but something I can envisage looking at more in the future. It’s kind of the reason I’ve moved over to Victron more recently as they seem to have some very clever systems. Still using my old EPever MPPT though which had been solid..

 

[brb58]

There is a range of the max recommended charge current for AGM batteries and it varies depending on manufacturer from 0.1C to 0.3C. For most I see, it's 0.2C which would be 48A in your case. The reality though is that the battery pretty much accepts what its going to accept and pretty much self regulates unless the charge voltage is really high. If you have your absorption voltage set at an acceptable level, you will not have an issue.

Out of curiosity, what does the manufacturer of your battery list for charge spec?

With 400W flat mounted, you aren't going to get more than 23A or so.

 

[StevieRuss]

There is a range of the max recommended charge current for AGM batteries and it varies depending on manufacturer from 0.1C to 0.3C. For most I see, it's 0.2C which would be 48A in your case. The reality though is that the battery pretty much accepts what its going to accept and pretty much self regulates unless the charge voltage is really high. If you have your absorption voltage set at an acceptable level, you will not have an issue.

Out of curiosity, what does the manufacturer of your battery list for charge spec?

With 400W flat mounted, you aren't going to get more than 23A or so.

Many thanks.

The batteries are about five years old now or actually slightly older and I don’t have the specs for them to hand. I set up the EPever MPPT through a PC laptop when I first fired it up and it is set to 14.7 and 13.8 so I take it those were the correct figures at the time. Oh actually this is them. They’re Lioch 120ah AGMs

https://www.alpha-batteries.co.uk/120ah-leoch-agm-leisure-battery/