Victron SmartShunt

[chrisski]

I had three Victron SCCs charging a lead acid bank, and limiting max charging amps was a problem. For me, I did not deplete my batteries more than 25%, so they were charged before the sun hit high enough in the sky to exceed the max charging amps.

I thought about entering a max amps into my SCCs that when added up never exceeded the max charge rate, but each SCC charges different so that would be inefficient.

I did not realize the Cerbo would allow an entry for all three to max out at.I know my 3 SCCs only have one entry each

Id recommend 10% as mentioned unless the spec sheet says different. My FLA spec sheet was13% but a gel or AGM may be 33%.

I ended up installing a lithium bank and am much happier.

[ShedPower]

Thanks. I would like Lithium but I’ve spent a lot on this system so far so will have to wait for a lithium upgrade. I think I may now be in the same position you had. With 1.5kw solar panels my 3 batteries should charge quickly, depending on load of course. The load currently is 750w a day.

[chrisski]

My guess is since you need about 62.5 ah of power a day, assuming 750wh, you will be close to the 39 amp max when your batteries are full. Watching for a cycle or two will help.

The problem would be when it’s cloudy until noon and then suddenly sunny. 1,5 kw of panels could get 90-100 amps of charging amps to a battery. I had about that many panels and because of angles to sun panel shading, the mist I saw was 74 amps, which still exceeded my 60 amp limit.

[ShedPower]

Wow! I think I need to increase the load and add a couple of batteries. I have limited the chargers to 40 amps between them for now.

[ShedPower]

The main reason for having the system is to enjoy doing it. I don't need it as such, but to have our freezer on solar is satisfying.

[chrisski]

Now that you can get an idea how much your batteries can put out ampwise, you can figure how many batteries to add to it. Barring for weather, your highest output will be in mid June. For my Rv, that makes a huge difference at noon with the sun straight up in the air shining on all panels as compared to December on the shortest days of the year when the sun is much lower and some of the panels are always shaded.

There’s mixed recommendations about adding lead acid batteries later about how the new ones can get dragged down to the older set and having to replace them at once. If these batteries you have are new, now is the time to add more. It’s always best to design the lead acid system to your power needs because of having to replace batteries. Lithium is a bit easier to add to and is coming down in price for pre-made batteries.

[ShedPower]

Yeah they are new batteries. Ive just ordered another one. I also have a 100ah battery kicking around. I have read that if your batteries are in paralell then you can add a battery with a different amp hour rating. Only true for paralell, not in series. if this is the case, ill also add the 100ah.

[SunEagle]

Yeah they are new batteries. Ive just ordered another one. I also have a 100ah battery kicking around. I have read that if your batteries are in paralell then you can add a battery with a different amp hour rating. Only true for paralell, not in series. if this is the case, ill also add the 100ah.

Two things you need to look into.

First parallel wired batteries can cause one or more to fail before the others.

Second. It is never a good idea to have different batteries in the same system. One of them will end up doing most of the work and fail early.

The best idea is to either use Lithium type or have the correct amount of FLA type in your system. Also with FLA you will need charging amps equal to about 1/10th the battery system Amp hour rating. More then 1/8th of the AH rating and you run the risk of cooking your batteries. Less than 1/12th of the AH rating and you run the risk of sulfating the batteries. And finally adding new batteries to older ones will hurt the newer ones.

[ShedPower]

What do you think about this?

https://rvnerds.com/2017/08/07/electrical-myths-part-3-mixing-batteries-different-agescapacities/

[Bala]

What do you think about this?

https://rvnerds.com/2017/08/07/elect...gescapacities/

I worked for a truck company for 3 years. Approximately 80 long haul b double units doing 300 000km each every year. Approximately 60 were 12v systems with 4 12 batteries in parallel and 20 with 24v systems batteries in series.

There was never a problem on the units with 24v systems boiling a battery.

It was common for the units with 12 v systems to come in with one battery boiling and it was always the battery in the same position in the pack. The battery packs are designed with the leads to equalise charge and discharge but the batteries are not exactly the same to start with and even with best design of the system they do not discharge and charge equally. Often a second hand battery was put in for the boiled one but before long another would fail.

A boiling battery is a bomb ready to blow. I have had batteries explode that were not boiling, just from load trying to start an engine.

You can always find the info you want to hear online but I think Dave's info is very poor advice. I believe batteries in parallel are not the best option but you will have a better performing and safer system when the batteries are matched as closely as possible.

[ShedPower]

Ok, thanks. Safety is paramount so I will go with your advice. I have another battery coming so I think I will change it to 24v too.

[SunEagle]

What do you think about this?

https://rvnerds.com/2017/08/07/elect...gescapacities/

I stand by my reasoning. If you choose to have different batteries in the same system then that is your choice. Hopefully they will last as long as you need them to.

[Bala]

Here is a thread from the forum.

https://www.solarpaneltalk.com/forum...es-in-parallel

[ShedPower]

Thanks I will have a look. I do want to always err on the side of caution so I will not mix different size batteries. In terms of parallel batteries, slightly off topic, I have wired mine using two bus bars, one for all the negatives and one for all the positives. And then taken a feed from each bus bar. Measuring the batteries individually, they seem to always be at the same voltage. So I think this works really well for charging and loading evenly. Im not engineer or anything like that, but just found this works well.

[ShedPower]

I have a problem on my system. I have a 1000w inverter which is fine feeding just our freezer, at about 50-70w continuous, often less. I have added our tv which runs at about 100w. However, the 13amp fuse in the plug that comes from the inverter to feed these two appliances, keeps blowing. Its a fairly simple system, and all the connections are good and well made. I haven't yet grounded the system in terms of a rod into the ground. Any ideas as to what might be causing the problem? Many thanks.