Trojan T105 RE Batteries not going to Float?

[Valken]

Good Day All,

Hope someone can shed some light? I have 8X Trojan T105RE Batteries (48V - Just under a year old) connected to my Axpert MKS 5KVA Inverter. Lately i have noticed it didn't go to Float and although the AMPS drop to about 6/7amps it never goes to float (54V) I topped up all the batteries 3 days ago and set the inverter to not use the batteries so it can charge constantly. 3 days passed now and it is still sitting on 58.8V and arround 6/7amps charge? Any ideas why?  

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This old Coulomb post suggest that current needs to drop below 20% of the total configured current, for ten minutes. For a 225ah bank then, you'd probably have that set to around 35A or maybe 40A, which means the current has to drop below 7 or 8 amps, which is right around where you are NOT dropping below. Just a wild guess though.

I found in practice that it really depends on the kind of battery. The old AGMs I had would drop to below 1% capacity if you held them at absorb for prolonged periods, and this is exactly how my Multiplus treated them. Flooded batteries tend to accept quite a bit of current even after they are full though.

 

[LivSol]

Check Specific Gravity of the cells at the end of the day. This will tell you if the batteries are being charged adequately. Reading should be 1,280.

In my experience the RE line from Trojan need higher voltages to reach full charge vs the signature line. But there are many factors.

I would guess that at 58,8 volts at 7-8amps the batteries are not fully charged. But I could be wrong. Check the SG, its only way to know where you are.

 

 

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12 hours ago, LivSol said:

In my experience the RE line from Trojan need higher voltages to reach full charge

They do reach full charge under lower voltage but it takes a lot more time.

[LivSol]

47 minutes ago, plonkster said:

They do reach full charge under lower voltage but it takes a lot more time.

Yes. Correct. But for the purposes discussed here i.e. charging off a PV array, there are limited sun hours and therefore higher voltages are needed. But also, in general the RE line seems to need a higher voltage than say the signature line under same conditions. I cannot explain this fully, but have found it to be the case.

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58 minutes ago, LivSol said:

there are limited sun hours

Yup. Even in their more traditional use (forklifts and golf carts), time is money and charging faster is preferred.

We have this discussion every few months, whether you can really use the Trojans with the lower-charging Axperts. I tend to vacillate a little on the topic, there are many who use them quite successfully with the Voltronics, and for UPS duty you can certainly get away with it (because they are permanently on float for all practical purposes), but every now and then the question does come up again.

As you say, measure the SG. That's the only way to know. If the SG is at 1280 and it still refuses to go to float, it might be because these batteries just pass too much current even when full. AGMs drop off quite a bit when they get full, and one does get the feeling that Voltronic designed these things with sealed batteries in mind.

[LivSol]

2 hours ago, plonkster said:

Yup. Even in their more traditional use (forklifts and golf carts), time is money and charging faster is preferred.

We have this discussion every few months, whether you can really use the Trojans with the lower-charging Axperts. I tend to vacillate a little on the topic, there are many who use them quite successfully with the Voltronics, and for UPS duty you can certainly get away with it (because they are permanently on float for all practical purposes), but every now and then the question does come up again.

As you say, measure the SG. That's the only way to know. If the SG is at 1280 and it still refuses to go to float, it might be because these batteries just pass too much current even when full. AGMs drop off quite a bit when they get full, and one does get the feeling that Voltronic designed these things with sealed batteries in mind.

1-3% of C20 rating indicates fully charged  battery. In the case of the the premium  RE line, 3% of C20 is still not at spec, but is for other FLA’s..Clear as mud charging is....

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13 minutes ago, LivSol said:

1-3% of C20 rating indicates fully charged  battery.

And for a 225Ah battery that is almost 7 amps. If the inverter is set to charge at a total of 35 or 40 amps, and the inverter uses 20% of that (8 amps) as the limit as reported on another thread, it is possible that it actually never goes low enough to go to float.

You could test by increasing the maximum charge current, 50A is a tad on the high side but you'd do it only to see if it goes to float.

[Valken]

41 minutes ago, plonkster said:

And for a 225Ah battery that is almost 7 amps. If the inverter is set to charge at a total of 35 or 40 amps, and the inverter uses 20% of that (8 amps) as the limit as reported on another thread, it is possible that it actually never goes low enough to go to float.

You could test by increasing the maximum charge current, 50A is a tad on the high side but you'd do it only to see if it goes to float.

Am i charging with too little AMPS? My Axpert MKS 5KVA is set to 20AMPS?

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Just now, Valken said:

Am i charging with too little AMPS? My Axpert MKS 5KVA is set to 20AMPS?

You should charge at around 15% of the Ah capacity, or around 30 to 35 amps in your case.

At 20 amps it will only go to float once charge current drops under 4 amps... again assuming that other post I linked is correct.

You can go as high as 40 amps on those batteries, it should not be a problem, those batteries can handle C/5. Just don't do it if the batteries are very low.

[LivSol]

17 hours ago, plonkster said:

You should charge at around 15% of the Ah capacity, or around 30 to 35 amps in your case.

At 20 amps it will only go to float once charge current drops under 4 amps... again assuming that other post I linked is correct.

You can go as high as 40 amps on those batteries, it should not be a problem, those batteries can handle C/5. Just don't do it if the batteries are very low.

C5 is a little aggressive in my view. 35 amps i.e C6.5, should really be the highest in my opinion. C10 is the recommended rate, a balance between faster charging and battery longevity. The recommended range is C8 - C12. 

Also, the faster you charge the battery at higher amps and voltage, the longer the said battery will sit in the absorb stage of the charge cycle. 

Just things to bare in mind..

 

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1 hour ago, LivSol said:

C5 is a little aggressive in my view. 35 amps i.e C6.5, should really be the highest in my opinion. C10 is the recommended rate, a balance between faster charging and battery longevity. The recommended range is C8 - C12. 

You're right. The best thing is to look at the spec sheet of your particular battery. Some AGMs are designed for faster charge and discharge. I looked up the specs for the T105 yesterday and there was nothing on the official sheet for "initial charge current", but the FAQ does say to aim for 10% to 13%, which also comes out to about 30A or maybe 35A.

When I say those batteries can handle C5, I should perhaps have been clearer, I didn't mean continuously :-) When charging with PV, where you will only have peak power available for a short time of the day, and you're also consuming some of that electricity at the same time, having a safety limit of C5 (where the objective is to get the algorithm into float, in other words this is a kludge or a hack) is probably okay.

So start with 30A and see if it goes to float. Then 35A... and then if you must, try 40A.

[LivSol]

On 11/2/2017 at 9:31 AM, plonkster said:

You're right. The best thing is to look at the spec sheet of your particular battery. Some AGMs are designed for faster charge and discharge. I looked up the specs for the T105 yesterday and there was nothing on the official sheet for "initial charge current", but the FAQ does say to aim for 10% to 13%, which also comes out to about 30A or maybe 35A.

When I say those batteries can handle C5, I should perhaps have been clearer, I didn't mean continuously :-) When charging with PV, where you will only have peak power available for a short time of the day, and you're also consuming some of that electricity at the same time, having a safety limit of C5 (where the objective is to get the algorithm into float, in other words this is a kludge or a hack) is probably okay.

So start with 30A and see if it goes to float. Then 35A... and then if you must, try 40A.

To be clear, when I referred to charge rates, I am talking about the T105 RE. AGM batteries can handle much higher charge rates, making them ideal for limited sun hour situations. 

It’s a matter of the internal resistance of the various battey types.