Using a MPPT as a battery charger?

[curiouscarbon]

thank you for sharing,

may i ask, did it become apparent what heated up?

the wires going to the MPPT appeared to be relatively small, perhaps they heated up?

thanks for stopping it when the smell happened, hope everything is ok

 

[BradCagle]

thank you for sharing,

may i ask, did it become apparent what heated up?

the wires going to the MPPT appeared to be relatively small, perhaps they heated up?

thanks for stopping it when the smell happened, hope everything is ok

No wires were hot. I think the smell was coming from inside the power supply. Which would correspond with my previous attempts at this, and burning out power supplies

 

[curiouscarbon]

thanks for your service to the community by attempting and documenting! ?

 

[BradCagle]

thanks for your service to the community by attempting and documenting! ?

You're welcome! I enjoy it.

 

[timselectric]

So far we have learned that your power supply can't be used this way.
I'm assuming that the problem with this test was that they are both self adjusting. So, they fought over control of the power. And the SCC won this battle.

 

[GSXR1000]

Aright I just tried it with this 10a 48v psu. Still drags the voltage down. I see what it's doing now, it's searching for MPP all the way down to the battery voltage, once it directly connects to the battery it releases. Now on this PSU it only did it once, but I think that's because the battery is fully charged. I'll let it drain, and get some video next.

View attachment 98800

that isn't large enough for 24v battery.. so when it tryst to max out 28.4v x 20 amp. 568w/48v=14.2 amp at 48v.. actually more dinner there is an efficiency loss ... do you have a clamp DC amp meter

 

[BradCagle]

that isn't large enough for 24v battery.. so when it tryst to max out 28.4v x 20 amp. 568w/48v=14.2 amp at 48v.. actually more dinner there is an efficiency loss ... do you have a clamp DC amp meter

I would love to go bigger, and keep this experiment going. Problem is I can't risk blowing my employers equipment out

At this point I will have to surrender with this being inconclusive.

I might revisit this later with all the equipment supplied at my risk.

 

[sunshine_eggo]

FWIW, since we're originally talking about a Victron MPPT, on community, there was a user powering a RS 450/100 with a 400VDC battery. Unfortunately, they were dealing with some weird limitation on that unit where input Voc must not be more than 8X battery float voltage, and it was causing problems.

While some made the comment that it's not being used as intended, the one Victron staff member was only concerned about how he could word it better in the documentation. At no point did he express concern at the user's choice to power it with a battery.

You can also find examples of competent users deploying MPPT for hydro and wind power.

 

[BradCagle]

FWIW, since we're originally talking about a Victron MPPT, on community, there was a user powering a RS 450/100 with a 400VDC battery. Unfortunately, they were dealing with some weird limitation on that unit where input Voc must not be more than 8X battery float voltage, and it was causing problems.

While some made the comment that it's not being used as intended, the one Victron staff member was only concerned about how he could word it better in the documentation. At no point did he express concern at the user's choice to power it with a battery.

You can also find examples of competent users deploying MPPT for hydro and wind power.

I think the thing to consider is when designing an MPPT for solar you're working with the knowledge a solar array can ( or should be able ) go dead short safely without self destructing.

I don't know enough about wind, or hydro, can they go direct short?

I guess a battery can too provided the BMS is up to the job.

 

[sunshine_eggo]

I think the thing to consider is when designing an MPPT for solar you're working with the knowledge a solar array can ( or should be able ) go dead short safely without self destructing.

Right. Hence my suggestion of a suitable fuse.

I don't know enough about wind, or hydro, can they go direct short?

Common method to keep wind/hydro from overspeed is to short their output; however, that was discussed as undesirable due to potential damage to the MPPT. The better solution was a switch that opened the input circuit of the MPPT and then shorted the wind output.

I guess a battery can too provided the BMS is up to the job.

or you have a fuse.

 

[Just John]

Alright, here's the video. I wanted to let it run longer, but started smelling components burning so I shut it down.

I suspect, your power supply is not current limited and the MPPT algorithm is trying to draw as much power out of the power supply as possible. Most cheaper power supplies are really only good for continuous output at 80% of their rating, and it's trying to run it at 100%.

So, what is the output of the EPEver? is it 40 amps?

3.65 x 8 = 29.2v and 29.2 x 40amps = 1168 watts and then 1168 x 1.2 =1401.6

So, with a cheap power supply, you need around 1500 watts, or it needs to be current limited.

I have run MPPT chargers just fine with my Riden, however they do limit current output. It will take a minute or two for the MPPT to find the right voltage/current and settle down.

Note, I was using a 20 amp MPPT and the Riden was fed by an 800 watt power supply I had modified to allow it to run continuously at 720 watts.

 

[BradCagle]

or you have a fuse.

Right but you don't want to blow a fuse every time you're trying to misuse your MPPT as a battery to battery charger

Anyhow, I think this whole MPPT Bat->Bat thing can work, but your mileage may vary. I would error on the side of caution.

 

[BradCagle]

I suspect, your power supply is not current limited and the MPPT algorithm is trying to draw as much power out of the power supply as possible. Most cheaper power supplies are really only good for continuous output at 80% of their rating, and it's trying to run it at 100%.

I agree

So, what is the output of the EPEver? is it 40 amps?

It's a 20a controller, so it'll (hopefully) limit charging to 20a

 

[curiouscarbon]

program the victron (or other brand) MPPT to limit input amperage to a level that will not trip fuse, and not damage power supply.

might try this myself. have a 24VDC power supply and some extra victron MPPT (<20A input) to attempt.

gut tells me that adjusting MPPT amperage setting could spare the Fuse AND PowerSupply.

dear visitors, you have inspired me. thanks for the info and fuel for experimentation.

 

[Just John]

I agree

It's a 20a controller, so it'll (hopefully) limit charging to 20a

So, nearly identical to how I tested the output of a Riden 6012 (60 volts at 12 amps) to make sure the power supply could continuously output 720 watts (it's an 800 watt supply with known issues of not being able to sustain the required 720 watts). Worked for an hour when I tested it.

 

[curiouscarbon]

most power supplies handle 60-80% continuously well

sometimes fan to handle temporary 100%

will try this (no fan) brick 24VDC power supply soon to MPPT.

intend to program MPPT to draw 75% of power supply continuous rating.

heat accelerate demise of equipment

 

[GSXR1000]

I suspect, your power supply is not current limited and the MPPT algorithm is trying to draw as much power out of the power supply as possible. Most cheaper power supplies are really only good for continuous output at 80% of their rating, and it's trying to run it at 100%.

So, what is the output of the EPEver? is it 40 amps?

3.65 x 8 = 29.2v and 29.2 x 40amps = 1168 watts and then 1168 x 1.2 =1401.6

So, with a cheap power supply, you need around 1500 watts, or it needs to be current limited.

I have run MPPT chargers just fine with my Riden, however they do limit current output. It will take a minute or two for the MPPT to find the right voltage/current and settle down.

Note, I was using a 20 amp MPPT and the Riden was fed by an 800 watt power supply I had modified to allow it to run continuously at 720 watts.

you can see I does find out the max the power supply can provide.. it raised the current till the voltage dropped then decreased current came back.. found the max power point of your PS.

49v at 10.6A.. you said 10 amps but it was over 10 and you said 10a PS so you can see it is running in overload.. that's why the smell

 

[BradCagle]

you can see I does find out the max the power supply can provide.. it raised the current till the voltage dropped then decreased current came back.. found the max power point of your PS.

Correct. However the MPPT searches for MPP periodically. I witnessed this on the other PSUs I tried in the past, so expect it to drag the voltage down more often than just on startup. At least with this controller it did that, not sure if all do it.

 

[GSXR1000]

Correct. However the MPPT searches for MPP periodically. I witnessed this on the other PSUs I tried in the past, so expect it to drag the voltage down more often than just on startup. At least with this controller it did that, not sure if all do it.

they should constantly check for new power point.. but if the power supply was larger then the power point would be at 20amp output or 15 amp input and it would not drag the voltage down

 

[Braingears]

I've been using my Victron SmartSolar 75/15 as a charger for years. I typically connect to 24V AGM Batteries and charge anything I want, and never had a single issue.