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Voltronic Infinisolar 3KW+ with T105RE batteries


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I have one of the Renesola 3KW hybrid inverters from Bonanza's current special.  Well, actually I have 2...  Couldn't say no at the price.

I had in mind to use it with 8 x T105RE batteries, but comparing the inverter specs with the recommended charge for the batteries I see the inverter comes up short in maximum voltage.

The batteries want 59.28v for bulk charge (never mind 64.8 to equalise).  The inverter maxes out at 58V

Amps wise the inverter can deliver 25A which I think will be sufficient.  But I'm guessing that the voltage shortfall will mean my batteries won't get 100% charged.  And I can't equalise.

What are my options?  Would it be OK as is?  Is there a way to mod the inverter to get that extra 10% voltage?  The main benefit of the hybrid inverter is all the functions are integrated, but is it possible to use a different charger? alongside the machine.

Otherwise I guess I need to find different batteries.


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Hi Elbow

@superdiy has Infinisolar and Trojans and he is happy with the combination. He has installed HA02 battery balancer to get around the equalising problem . I suppose it comes down to how often you plan to discharge them. 

@plonkster had a very useful analogy saying charging at 58V when the bulk was 59.28V was like being on the freeway in a jalopy that can only do 100km/h when the speed limit is 120 km/h. You will reach you destination but it just takes longer. If you only discharge occasionally then the lower bulk voltage is not such a huge disadvantage. If you plan to discharge every evening then there may not be enough solar hours in a day to recharge the battery.

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22 minutes ago, Elbow said:

my batteries won't get 100% charge

You can charge  battery to 100% at a lower voltage, it just takes longer. MUCH longer. In fact, every alarm system/cheap UPS rely on this to charge their batteries. They have no special three-stage charger, they simply hold their little internal 12V battery at 13.8V permanently, and over the course of a week it eventually charges fully.

So as Chris says, if you want to cycle them daily, then yes, you'll probably have a problem. You may have to spend some time each week making sure they fully recharge. If you cycle them only lightly, or use the inverter as a GTI and the batteries are literally only used for backup, then no need to worry. You'll be fine.

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I agree with @plonkster. If you are just going to use battery as backup, then you should be fine. That what I do, and I have noticed that the battery water level don't need regular topup as before, when I was using the batts. I even think if you are going to do this, then even the RE's is an overkill. Why buy batteries with a high cycle count if you are not  going to cycle them. ? If I was to redesign, I go for the plain T-105 models. Obvious, if you plan on running of Batts overnight every night, then the RE is preferable. 

Mine are 9 month old now, and the BMV reports the cycle count = 2!

The highest Vbat = 59.4V, but must have been for very short period, cannot see this on the graphs, but see 58.6V bulk charge, which is the max setting on the 5kW.

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Thanks guys for the advice - really appreciate it.

I have put some EmonCMS monitoring on my board and I'm gathering some stats - I'm going to use that to really understand my load profile and that should help figure out exactly what I need.  Once I've got a few weeks data I'll post the data and my analysis for comment.

Right now it shows my geyser using between 9 and 14 kWh per day, and everything else using between 15 and 20 kWh.  I have an old Intel server running as a NAS and that uses a steady 230W so that is really costing me - 6 kWh of that total.

So decision one: solar geyser, "power dump" element off PV, or heat-pump to deal with the hot water.
And replace that old server with something more efficient.

Anyway - thanks for the help with the battery question.






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@Elbow , I have two strings op 8 x T105 batteries in parallel connected with two parallel Axpert MKS inverters. I was equally concerned about the charging of the batteries. Using ICC-Pi from @Manie as control program togeter with his MQTT Dashboard, I run on batteries from 9:00 to 16:30 in winter and from 1:00am to 17:00 in summer. Since I am not grid tied, it would be an inexcusable waste to let all the solar generation, in excess to consumption, during the day go to waste. My batteries rarely go below 85% as I switch to grid when it is very overcast and the batteries are near 80% using RealVNC from my desktop PC.

I also use @Coulomb's latest firmware and have set parameter 32 to 30 minutes but increase that to 3 hours when I want to refill batteries. So during the night when on grid, this ensures that the batteries are fully charged in the morning for refilling. The same setting can be set to up to 900 minus (15 hrs) to keep the charge voltage at 58.4V for equalising. As @Chris Hobson suggested, you should consider the HA02 equalisers, available from him. I have five, four to equalise four blocks of four batteries and using half of the fifth one  connecting the last battery on one block to the first on the second block of each string. The batteries remain equalised within narrow margins.

Below is a response from Trojan USA on my question about the issue.


Your battery bank is rated at 450-Ah. The initial charge rate for proper charging should in the range of 10-13% of 450-AH (45-60A), up to a maximum rate of 20% (90A). What is your equalization capable voltage? You can use a lower voltage, but it will take longer to equalize batteries. That CTek charger will not equalize these heavy duty deep cycle batteries.


Dear Sir/Madam, I have 16 T105s connected in 2 strings of 8 batteries. The 2 strings are connected in parallel. My Inverter MPPT charger has a maximum voltage rating of 58.4V which is below the T105 bulk charge rate of 59.28V. I also does not have equalization capability of 64.80V. The only solution I can think of is an external charger with equalization capability and the best I could find locally is a Ctek MXT14 charger which can do 31.6V for equalization. Could I use this to equalize the batteries in blocks of 4 as the Ctek voltage is 24V. Will it also have a very detrimental effect on the batteries if the solar MPPT charger only charge them to 58.4V daily. I mostly do not discharge below 80% SOC. Your kind advice and any suggestions and recommendations will be greatly appreciated.

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I follow the off-gridders advices in that batts must be charge full at least once a week.

Not stressing if I don't get a SOC above 87% (in my case) at the end of the day after I powered all the stuff I wanted the entire day.

EDIT: Each weekend there is a day that there is little powered, then the batts are normally charged full again.

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